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--DNSEXT D. Blacka
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--Intended status: Standards Track April 7, 2006
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-- DNSSEC Experiments
-- draft-ietf-dnsext-dnssec-experiments-03
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on October 9, 2006.
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--Copyright Notice
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-- Copyright (C) The Internet Society (2006).
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--Abstract
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-- This document describes a methodology for deploying alternate, non-
-- backwards-compatible, DNSSEC methodologies in an experimental fashion
-- without disrupting the deployment of standard DNSSEC.
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--Table of Contents
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-- 1. Definitions and Terminology . . . . . . . . . . . . . . . . . 3
-- 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
-- 3. Experiments . . . . . . . . . . . . . . . . . . . . . . . . . 5
-- 4. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
-- 5. Defining an Experiment . . . . . . . . . . . . . . . . . . . . 8
-- 6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 9
-- 7. Use in Non-Experiments . . . . . . . . . . . . . . . . . . . . 10
-- 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
-- 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
-- 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
-- 10.1. Normative References . . . . . . . . . . . . . . . . . . 13
-- 10.2. Informative References . . . . . . . . . . . . . . . . . 13
-- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
-- Intellectual Property and Copyright Statements . . . . . . . . . . 15
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--1. Definitions and Terminology
--
-- Throughout this document, familiarity with the DNS system (RFC 1035
-- [5]) and the DNS security extensions ([2], [3], and [4] is assumed.
--
-- The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119 [1].
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--2. Overview
--
-- Historically, experimentation with DNSSEC alternatives has been a
-- problematic endeavor. There has typically been a desire to both
-- introduce non-backwards-compatible changes to DNSSEC and to try these
-- changes on real zones in the public DNS. This creates a problem when
-- the change to DNSSEC would make all or part of the zone using those
-- changes appear bogus (bad) or otherwise broken to existing security-
-- aware resolvers.
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-- This document describes a standard methodology for setting up DNSSEC
-- experiments. This methodology addresses the issue of co-existence
-- with standard DNSSEC and DNS by using unknown algorithm identifiers
-- to hide the experimental DNSSEC protocol modifications from standard
-- security-aware resolvers.
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--3. Experiments
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-- When discussing DNSSEC experiments, it is necessary to classify these
-- experiments into two broad categories:
--
-- Backwards-Compatible: describes experimental changes that, while not
-- strictly adhering to the DNSSEC standard, are nonetheless
-- interoperable with clients and servers that do implement the
-- DNSSEC standard.
--
-- Non-Backwards-Compatible: describes experiments that would cause a
-- standard security-aware resolver to (incorrectly) determine that
-- all or part of a zone is bogus, or to otherwise not interoperate
-- with standard DNSSEC clients and servers.
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-- Not included in these terms are experiments with the core DNS
-- protocol itself.
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-- The methodology described in this document is not necessary for
-- backwards-compatible experiments, although it certainly may be used
-- if desired.
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--4. Method
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-- The core of the methodology is the use of strictly unknown algorithm
-- identifiers when signing the experimental zone, and more importantly,
-- having only unknown algorithm identifiers in the DS records for the
-- delegation to the zone at the parent.
--
-- This technique works because of the way DNSSEC-compliant validators
-- are expected to work in the presence of a DS set with only unknown
-- algorithm identifiers. From [4], Section 5.2:
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-- If the validator does not support any of the algorithms listed in
-- an authenticated DS RRset, then the resolver has no supported
-- authentication path leading from the parent to the child. The
-- resolver should treat this case as it would the case of an
-- authenticated NSEC RRset proving that no DS RRset exists, as
-- described above.
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-- And further:
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-- If the resolver does not support any of the algorithms listed in
-- an authenticated DS RRset, then the resolver will not be able to
-- verify the authentication path to the child zone. In this case,
-- the resolver SHOULD treat the child zone as if it were unsigned.
--
-- While this behavior isn't strictly mandatory (as marked by MUST), it
-- is likely that a validator would implement this behavior, or, more to
-- the point, it would handle this situation in a safe way (see below
-- (Section 6).)
--
-- Because we are talking about experiments, it is RECOMMENDED that
-- private algorithm numbers be used (see [3], appendix A.1.1. Note
-- that secure handling of private algorithms requires special handing
-- by the validator logic. See [6] for further details.) Normally,
-- instead of actually inventing new signing algorithms, the recommended
-- path is to create alternate algorithm identifiers that are aliases
-- for the existing, known algorithms. While, strictly speaking, it is
-- only necessary to create an alternate identifier for the mandatory
-- algorithms, it is suggested that all optional defined algorithms be
-- aliased as well.
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-- It is RECOMMENDED that for a particular DNSSEC experiment, a
-- particular domain name base is chosen for all new algorithms, then
-- the algorithm number (or name) is prepended to it. For example, for
-- experiment A, the base name of "dnssec-experiment-a.example.com" is
-- chosen. Then, aliases for algorithms 3 (DSA) and 5 (RSASHA1) are
-- defined to be "3.dnssec-experiment-a.example.com" and
-- "5.dnssec-experiment-a.example.com". However, any unique identifier
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-- Using this method, resolvers (or, more specifically, DNSSEC
-- validators) essentially indicate their ability to understand the
-- DNSSEC experiment's semantics by understanding what the new algorithm
-- identifiers signify.
--
-- This method creates two classes of security-aware servers and
-- resolvers: servers and resolvers that are aware of the experiment
-- (and thus recognize the experiment's algorithm identifiers and
-- experimental semantics), and servers and resolvers that are unaware
-- of the experiment.
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-- This method also precludes any zone from being both in an experiment
-- and in a classic DNSSEC island of security. That is, a zone is
-- either in an experiment and only experimentally validatable, or it is
-- not.
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--5. Defining an Experiment
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-- The DNSSEC experiment MUST define the particular set of (previously
-- unknown) algorithm identifiers that identify the experiment, and
-- define what each unknown algorithm identifier means. Typically,
-- unless the experiment is actually experimenting with a new DNSSEC
-- algorithm, this will be a mapping of private algorithm identifiers to
-- existing, known algorithms.
--
-- Normally the experiment will choose a DNS name as the algorithm
-- identifier base. This DNS name SHOULD be under the control of the
-- authors of the experiment. Then the experiment will define a mapping
-- between known mandatory and optional algorithms into this private
-- algorithm identifier space. Alternately, the experiment MAY use the
-- OID private algorithm space instead (using algorithm number 254), or
-- MAY choose non-private algorithm numbers, although this would require
-- an IANA allocation.
--
-- For example, an experiment might specify in its description the DNS
-- name "dnssec-experiment-a.example.com" as the base name, and declare
-- that "3.dnssec-experiment-a.example.com" is an alias of DNSSEC
-- algorithm 3 (DSA), and that "5.dnssec-experiment-a.example.com" is an
-- alias of DNSSEC algorithm 5 (RSASHA1).
--
-- Resolvers MUST only recognize the experiment's semantics when present
-- in a zone signed by one or more of these algorithm identifiers. This
-- is necessary to isolate the semantics of one experiment from any
-- others that the resolver might understand.
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-- In general, resolvers involved in the experiment are expected to
-- understand both standard DNSSEC and the defined experimental DNSSEC
-- protocol, although this isn't required.
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--6. Considerations
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-- There are a number of considerations with using this methodology.
--
-- 1. Under some circumstances, it may be that the experiment will not
-- be sufficiently masked by this technique and may cause resolution
-- problem for resolvers not aware of the experiment. For instance,
-- the resolver may look at a non-validatable response and conclude
-- that the response is bogus, either due to local policy or
-- implementation details. This is not expected to be a common
-- case, however.
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-- 2. It will not be possible for security-aware resolvers unaware of
-- the experiment to build a chain of trust through an experimental
-- zone.
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--7. Use in Non-Experiments
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-- This general methodology MAY be used for non-backwards compatible
-- DNSSEC protocol changes that start out as or become standards. In
-- this case:
--
-- o The protocol change SHOULD use public IANA allocated algorithm
-- identifiers instead of private algorithm identifiers. This will
-- help identify the protocol change as a standard, rather than an
-- experiment.
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-- o Resolvers MAY recognize the protocol change in zones not signed
-- (or not solely signed) using the new algorithm identifiers.
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--8. Security Considerations
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-- Zones using this methodology will be considered insecure by all
-- resolvers except those aware of the experiment. It is not generally
-- possible to create a secure delegation from an experimental zone that
-- will be followed by resolvers unaware of the experiment.
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--9. IANA Considerations
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-- This document has no IANA actions.
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--10. References
--
--10.1. Normative References
--
-- [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
-- [2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033,
-- March 2005.
--
-- [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- [4] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions",
-- RFC 4035, March 2005.
--
--10.2. Informative References
--
-- [5] Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
-- [6] Austein, R. and S. Weiler, "Clarifications and Implementation
-- Notes for DNSSECbis", draft-ietf-dnsext-dnssec-bis-updates-02
-- (work in progress), January 2006.
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--Author's Address
--
-- David Blacka
-- VeriSign, Inc.
-- 21355 Ridgetop Circle
-- Dulles, VA 20166
-- US
--
-- Phone: +1 703 948 3200
-- Email: davidb@verisign.com
-- URI: http://www.verisignlabs.com
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--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
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--Network Working Group S. Weiler
--Internet-Draft SPARTA, Inc
--Updates: 4034, 4035 (if approved) J. Ihren
--Expires: July 24, 2006 Autonomica AB
-- January 20, 2006
--
--
-- Minimally Covering NSEC Records and DNSSEC On-line Signing
-- draft-ietf-dnsext-dnssec-online-signing-02
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on July 24, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document describes how to construct DNSSEC NSEC resource records
-- that cover a smaller range of names than called for by RFC4034. By
-- generating and signing these records on demand, authoritative name
-- servers can effectively stop the disclosure of zone contents
-- otherwise made possible by walking the chain of NSEC records in a
-- signed zone.
--
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--Changes from ietf-01 to ietf-02
--
-- Clarified that a generated NSEC RR's type bitmap MUST have the RRSIG
-- and NSEC bits set, to be consistent with DNSSECbis -- previous text
-- said SHOULD.
--
-- Made the applicability statement a little less oppressive.
--
--Changes from ietf-00 to ietf-01
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-- Added an applicability statement, making reference to ongoing work on
-- NSEC3.
--
-- Added the phrase "epsilon functions", which has been commonly used to
-- describe the technique and already appeared in the header of each
-- page, in place of "increment and decrement functions". Also added an
-- explanatory sentence.
--
-- Corrected references from 4034 section 6.2 to section 6.1.
--
-- Fixed an out-of-date reference to [-bis] and other typos.
--
-- Replaced IANA Considerations text.
--
-- Escaped close parentheses in examples.
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-- Added some more acknowledgements.
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--Changes from weiler-01 to ietf-00
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-- Inserted RFC numbers for 4033, 4034, and 4035.
--
-- Specified contents of bitmap field in synthesized NSEC RR's, pointing
-- out that this relaxes a constraint in 4035. Added 4035 to the
-- Updates header.
--
--Changes from weiler-00 to weiler-01
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-- Clarified that this updates RFC4034 by relaxing requirements on the
-- next name field.
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-- Added examples covering wildcard names.
--
-- In the 'better functions' section, reiterated that perfect functions
-- aren't needed.
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-- Added a reference to RFC 2119.
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--Table of Contents
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-- 1. Introduction and Terminology . . . . . . . . . . . . . . . . . 4
-- 2. Applicability of This Technique . . . . . . . . . . . . . . . 4
-- 3. Minimally Covering NSEC Records . . . . . . . . . . . . . . . 5
-- 4. Better Epsilon Functions . . . . . . . . . . . . . . . . . . . 6
-- 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
-- 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
-- 7. Normative References . . . . . . . . . . . . . . . . . . . . . 8
-- Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 8
-- Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
-- Intellectual Property and Copyright Statements . . . . . . . . . . 11
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--1. Introduction and Terminology
--
-- With DNSSEC [1], an NSEC record lists the next instantiated name in
-- its zone, proving that no names exist in the "span" between the
-- NSEC's owner name and the name in the "next name" field. In this
-- document, an NSEC record is said to "cover" the names between its
-- owner name and next name.
--
-- Through repeated queries that return NSEC records, it is possible to
-- retrieve all of the names in the zone, a process commonly called
-- "walking" the zone. Some zone owners have policies forbidding zone
-- transfers by arbitrary clients; this side-effect of the NSEC
-- architecture subverts those policies.
--
-- This document presents a way to prevent zone walking by constructing
-- NSEC records that cover fewer names. These records can make zone
-- walking take approximately as many queries as simply asking for all
-- possible names in a zone, making zone walking impractical. Some of
-- these records must be created and signed on demand, which requires
-- on-line private keys. Anyone contemplating use of this technique is
-- strongly encouraged to review the discussion of the risks of on-line
-- signing in Section 6.
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119 [4].
--
--
--2. Applicability of This Technique
--
-- The technique presented here may be useful to a zone owner that wants
-- to use DNSSEC, is concerned about exposure of its zone contents via
-- zone walking, and is willing to bear the costs of on-line signing.
--
-- As discussed in Section 6, on-line signing has several security
-- risks, including an increased likelihood of private keys being
-- disclosed and an increased risk of denial of service attack. Anyone
-- contemplating use of this technique is strongly encouraged to review
-- the discussion of the risks of on-line signing in Section 6.
--
-- Furthermore, at the time this document was published, the DNSEXT
-- working group was actively working on a mechanism to prevent zone
-- walking that does not require on-line signing (tentatively called
-- NSEC3). The new mechanism is likely to expose slightly more
-- information about the zone than this technique (e.g. the number of
-- instantiated names), but it may be preferable to this technique.
--
--
--
--
--
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--
--
--3. Minimally Covering NSEC Records
--
-- This mechanism involves changes to NSEC records for instantiated
-- names, which can still be generated and signed in advance, as well as
-- the on-demand generation and signing of new NSEC records whenever a
-- name must be proven not to exist.
--
-- In the 'next name' field of instantiated names' NSEC records, rather
-- than list the next instantiated name in the zone, list any name that
-- falls lexically after the NSEC's owner name and before the next
-- instantiated name in the zone, according to the ordering function in
-- RFC4034 [2] section 6.1. This relaxes the requirement in section
-- 4.1.1 of RFC4034 that the 'next name' field contains the next owner
-- name in the zone. This change is expected to be fully compatible
-- with all existing DNSSEC validators. These NSEC records are returned
-- whenever proving something specifically about the owner name (e.g.
-- that no resource records of a given type appear at that name).
--
-- Whenever an NSEC record is needed to prove the non-existence of a
-- name, a new NSEC record is dynamically produced and signed. The new
-- NSEC record has an owner name lexically before the QNAME but
-- lexically following any existing name and a 'next name' lexically
-- following the QNAME but before any existing name.
--
-- The generated NSEC record's type bitmap MUST have the RRSIG and NSEC
-- bits set and SHOULD NOT have any other bits set. This relaxes the
-- requirement in Section 2.3 of RFC4035 that NSEC RRs not appear at
-- names that did not exist before the zone was signed.
--
-- The functions to generate the lexically following and proceeding
-- names need not be perfect nor consistent, but the generated NSEC
-- records must not cover any existing names. Furthermore, this
-- technique works best when the generated NSEC records cover as few
-- names as possible. In this document, the functions that generate the
-- nearby names are called 'epsilon' functions, a reference to the
-- mathematical convention of using the greek letter epsilon to
-- represent small deviations.
--
-- An NSEC record denying the existence of a wildcard may be generated
-- in the same way. Since the NSEC record covering a non-existent
-- wildcard is likely to be used in response to many queries,
-- authoritative name servers using the techniques described here may
-- want to pregenerate or cache that record and its corresponding RRSIG.
--
-- For example, a query for an A record at the non-instantiated name
-- example.com might produce the following two NSEC records, the first
-- denying the existence of the name example.com and the second denying
-- the existence of a wildcard:
--
--
--
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--
--
-- exampld.com 3600 IN NSEC example-.com ( RRSIG NSEC )
--
-- \).com 3600 IN NSEC +.com ( RRSIG NSEC )
--
-- Before answering a query with these records, an authoritative server
-- must test for the existence of names between these endpoints. If the
-- generated NSEC would cover existing names (e.g. exampldd.com or
-- *bizarre.example.com), a better epsilon function may be used or the
-- covered name closest to the QNAME could be used as the NSEC owner
-- name or next name, as appropriate. If an existing name is used as
-- the NSEC owner name, that name's real NSEC record MUST be returned.
-- Using the same example, assuming an exampldd.com delegation exists,
-- this record might be returned from the parent:
--
-- exampldd.com 3600 IN NSEC example-.com ( NS DS RRSIG NSEC )
--
-- Like every authoritative record in the zone, each generated NSEC
-- record MUST have corresponding RRSIGs generated using each algorithm
-- (but not necessarily each DNSKEY) in the zone's DNSKEY RRset, as
-- described in RFC4035 [3] section 2.2. To minimize the number of
-- signatures that must be generated, a zone may wish to limit the
-- number of algorithms in its DNSKEY RRset.
--
--
--4. Better Epsilon Functions
--
-- Section 6.1 of RFC4034 defines a strict ordering of DNS names.
-- Working backwards from that definition, it should be possible to
-- define epsilon functions that generate the immediately following and
-- preceding names, respectively. This document does not define such
-- functions. Instead, this section presents functions that come
-- reasonably close to the perfect ones. As described above, an
-- authoritative server should still ensure than no generated NSEC
-- covers any existing name.
--
-- To increment a name, add a leading label with a single null (zero-
-- value) octet.
--
-- To decrement a name, decrement the last character of the leftmost
-- label, then fill that label to a length of 63 octets with octets of
-- value 255. To decrement a null (zero-value) octet, remove the octet
-- -- if an empty label is left, remove the label. Defining this
-- function numerically: fill the left-most label to its maximum length
-- with zeros (numeric, not ASCII zeros) and subtract one.
--
-- In response to a query for the non-existent name foo.example.com,
-- these functions produce NSEC records of:
--
--
--
--
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--
--
-- fon\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255.example.com 3600 IN NSEC \000.foo.example.com ( NSEC RRSIG )
--
-- \)\255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255.example.com 3600 IN NSEC \000.*.example.com ( NSEC RRSIG )
--
-- The first of these NSEC RRs proves that no exact match for
-- foo.example.com exists, and the second proves that there is no
-- wildcard in example.com.
--
-- Both of these functions are imperfect: they don't take into account
-- constraints on number of labels in a name nor total length of a name.
-- As noted in the previous section, though, this technique does not
-- depend on the use of perfect epsilon functions: it is sufficient to
-- test whether any instantiated names fall into the span covered by the
-- generated NSEC and, if so, substitute those instantiated owner names
-- for the NSEC owner name or next name, as appropriate.
--
--
--5. IANA Considerations
--
-- This document specifies no IANA Actions.
--
--
--6. Security Considerations
--
-- This approach requires on-demand generation of RRSIG records. This
-- creates several new vulnerabilities.
--
-- First, on-demand signing requires that a zone's authoritative servers
-- have access to its private keys. Storing private keys on well-known
-- internet-accessible servers may make them more vulnerable to
-- unintended disclosure.
--
-- Second, since generation of digital signatures tends to be
-- computationally demanding, the requirement for on-demand signing
-- makes authoritative servers vulnerable to a denial of service attack.
--
-- Lastly, if the epsilon functions are predictable, on-demand signing
-- may enable a chosen-plaintext attack on a zone's private keys. Zones
-- using this approach should attempt to use cryptographic algorithms
-- that are resistant to chosen-plaintext attacks. It's worth noting
--
--
--
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--
--
-- that while DNSSEC has a "mandatory to implement" algorithm, that is a
-- requirement on resolvers and validators -- there is no requirement
-- that a zone be signed with any given algorithm.
--
-- The success of using minimally covering NSEC record to prevent zone
-- walking depends greatly on the quality of the epsilon functions
-- chosen. An increment function that chooses a name obviously derived
-- from the next instantiated name may be easily reverse engineered,
-- destroying the value of this technique. An increment function that
-- always returns a name close to the next instantiated name is likewise
-- a poor choice. Good choices of epsilon functions are the ones that
-- produce the immediately following and preceding names, respectively,
-- though zone administrators may wish to use less perfect functions
-- that return more human-friendly names than the functions described in
-- Section 4 above.
--
-- Another obvious but misguided concern is the danger from synthesized
-- NSEC records being replayed. It's possible for an attacker to replay
-- an old but still validly signed NSEC record after a new name has been
-- added in the span covered by that NSEC, incorrectly proving that
-- there is no record at that name. This danger exists with DNSSEC as
-- defined in [3]. The techniques described here actually decrease the
-- danger, since the span covered by any NSEC record is smaller than
-- before. Choosing better epsilon functions will further reduce this
-- danger.
--
--7. Normative References
--
-- [1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033,
-- March 2005.
--
-- [2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions",
-- RFC 4035, March 2005.
--
-- [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
--
--Appendix A. Acknowledgments
--
-- Many individuals contributed to this design. They include, in
-- addition to the authors of this document, Olaf Kolkman, Ed Lewis,
--
--
--
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--
--
-- Peter Koch, Matt Larson, David Blacka, Suzanne Woolf, Jaap Akkerhuis,
-- Jakob Schlyter, Bill Manning, and Joao Damas.
--
-- In addition, the editors would like to thank Ed Lewis, Scott Rose,
-- and David Blacka for their careful review of the document.
--
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--Authors' Addresses
--
-- Samuel Weiler
-- SPARTA, Inc
-- 7075 Samuel Morse Drive
-- Columbia, Maryland 21046
-- US
--
-- Email: weiler@tislabs.com
--
--
-- Johan Ihren
-- Autonomica AB
-- Bellmansgatan 30
-- Stockholm SE-118 47
-- Sweden
--
-- Email: johani@autonomica.se
--
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--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--
--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
-- except as set forth therein, the authors retain all their rights.
--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
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--Network Working Group W. Hardaker
--Internet-Draft Sparta
--Expires: August 25, 2006 February 21, 2006
--
--
-- Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs)
-- draft-ietf-dnsext-ds-sha256-05.txt
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on August 25, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document specifies how to use the SHA-256 digest type in DNS
-- Delegation Signer (DS) Resource Records (RRs). DS records, when
-- stored in a parent zone, point to key signing DNSKEY key(s) in a
-- child zone.
--
--
--
--
--
--
--
--
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--
--
--Table of Contents
--
-- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
-- 2. Implementing the SHA-256 algorithm for DS record support . . . 3
-- 2.1. DS record field values . . . . . . . . . . . . . . . . . . 3
-- 2.2. DS Record with SHA-256 Wire Format . . . . . . . . . . . . 3
-- 2.3. Example DS Record Using SHA-256 . . . . . . . . . . . . . . 4
-- 3. Implementation Requirements . . . . . . . . . . . . . . . . . . 4
-- 4. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4
-- 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
-- 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
-- 6.1. Potential Digest Type Downgrade Attacks . . . . . . . . . . 5
-- 6.2. SHA-1 vs SHA-256 Considerations for DS Records . . . . . . 6
-- 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
-- 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
-- 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
-- 8.2. Informative References . . . . . . . . . . . . . . . . . . 7
-- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
-- Intellectual Property and Copyright Statements . . . . . . . . . . 9
--
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--
--
--1. Introduction
--
-- The DNSSEC [RFC4033] [RFC4034] [RFC4035] DS RR is published in parent
-- zones to distribute a cryptographic digest of a child's Key Signing
-- Key (KSK) DNSKEY RR. The DS RRset is signed by at least one of the
-- parent zone's private zone data signing keys for each algorithm in
-- use by the parent. Each signature is published in an RRSIG resource
-- record, owned by the same domain as the DS RRset and with a type
-- covered of DS.
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [RFC2119].
--
--
--2. Implementing the SHA-256 algorithm for DS record support
--
-- This document specifies that the digest type code [XXX: To be
-- assigned by IANA; likely 2] is to be assigned to SHA-256 [SHA256]
-- [SHA256CODE] for use within DS records. The results of the digest
-- algorithm MUST NOT be truncated and the entire 32 byte digest result
-- is to be published in the DS record.
--
--2.1. DS record field values
--
-- Using the SHA-256 digest algorithm within a DS record will make use
-- of the following DS-record fields:
--
-- Digest type: [XXX: To be assigned by IANA; likely 2]
--
-- Digest: A SHA-256 bit digest value calculated by using the following
-- formula ("|" denotes concatenation). The resulting value is not
-- truncated and the entire 32 byte result is to used in the
-- resulting DS record and related calculations.
--
-- digest = SHA_256(DNSKEY owner name | DNSKEY RDATA)
--
-- where DNSKEY RDATA is defined by [RFC4034] as:
--
-- DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key
--
-- The Key Tag field and Algorithm fields remain unchanged by this
-- document and are specified in the [RFC4034] specification.
--
--2.2. DS Record with SHA-256 Wire Format
--
-- The resulting on-the-wire format for the resulting DS record will be
-- [XXX: IANA assignment should replace the 2 below]:
--
--
--
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--
--
-- 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
-- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | Key Tag | Algorithm | DigestType=2 |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- / /
-- / Digest (length for SHA-256 is 32 bytes) /
-- / /
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
--
--2.3. Example DS Record Using SHA-256
--
-- The following is an example DNSKEY and matching DS record. This
-- DNSKEY record comes from the example DNSKEY/DS records found in
-- section 5.4 of [RFC4034].
--
-- The DNSKEY record:
--
-- dskey.example.com. 86400 IN DNSKEY 256 3 5 ( AQOeiiR0GOMYkDshWoSKz9Xz
-- fwJr1AYtsmx3TGkJaNXVbfi/
-- 2pHm822aJ5iI9BMzNXxeYCmZ
-- DRD99WYwYqUSdjMmmAphXdvx
-- egXd/M5+X7OrzKBaMbCVdFLU
-- Uh6DhweJBjEVv5f2wwjM9Xzc
-- nOf+EPbtG9DMBmADjFDc2w/r
-- ljwvFw==
-- ) ; key id = 60485
--
-- The resulting DS record covering the above DNSKEY record using a SHA-
-- 256 digest: [RFC Editor: please replace XXX with the assigned digest
-- type (likely 2):]
--
-- dskey.example.com. 86400 IN DS 60485 5 XXX ( D4B7D520E7BB5F0F67674A0C
-- CEB1E3E0614B93C4F9E99B83
-- 83F6A1E4469DA50A )
--
--
--3. Implementation Requirements
--
-- Implementations MUST support the use of the SHA-256 algorithm in DS
-- RRs. Validator implementations SHOULD ignore DS RRs containing SHA-1
-- digests if DS RRs with SHA-256 digests are present in the DS RRset.
--
--
--4. Deployment Considerations
--
-- If a validator does not support the SHA-256 digest type and no other
-- DS RR exists in a zone's DS RRset with a supported digest type, then
--
--
--
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--
--
-- the validator has no supported authentication path leading from the
-- parent to the child. The resolver should treat this case as it would
-- the case of an authenticated NSEC RRset proving that no DS RRset
-- exists, as described in [RFC4035], section 5.2.
--
-- Because zone administrators can not control the deployment speed of
-- support for SHA-256 in validators that may be referencing any of
-- their zones, zone operators should consider deploying both SHA-1 and
-- SHA-256 based DS records. This should be done for every DNSKEY for
-- which DS records are being generated. Whether to make use of both
-- digest types and for how long is a policy decision that extends
-- beyond the scope of this document.
--
--
--5. IANA Considerations
--
-- Only one IANA action is required by this document:
--
-- The Digest Type to be used for supporting SHA-256 within DS records
-- needs to be assigned by IANA. This document requests that the Digest
-- Type value of 2 be assigned to the SHA-256 digest algorithm.
--
-- At the time of this writing, the current digest types assigned for
-- use in DS records are as follows:
--
-- VALUE Digest Type Status
-- 0 Reserved -
-- 1 SHA-1 MANDATORY
-- 2 SHA-256 MANDATORY
-- 3-255 Unassigned -
--
--
--6. Security Considerations
--
--6.1. Potential Digest Type Downgrade Attacks
--
-- A downgrade attack from a stronger digest type to a weaker one is
-- possible if all of the following are true:
--
-- o A zone includes multiple DS records for a given child's DNSKEY,
-- each of which use a different digest type.
--
-- o A validator accepts a weaker digest even if a stronger one is
-- present but invalid.
--
-- For example, if the following conditions are all true:
--
--
--
--
--
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--
--
-- o Both SHA-1 and SHA-256 based digests are published in DS records
-- within a parent zone for a given child zone's DNSKEY.
--
-- o The DS record with the SHA-1 digest matches the digest computed
-- using the child zone's DNSKEY.
--
-- o The DS record with the SHA-256 digest fails to match the digest
-- computed using the child zone's DNSKEY.
--
-- Then if the validator accepts the above situation as secure then this
-- can be used as a downgrade attack since the stronger SHA-256 digest
-- is ignored.
--
--6.2. SHA-1 vs SHA-256 Considerations for DS Records
--
-- Users of DNSSEC are encouraged to deploy SHA-256 as soon as software
-- implementations allow for it. SHA-256 is widely believed to be more
-- resilient to attack than SHA-1, and confidence in SHA-1's strength is
-- being eroded by recently-announced attacks. Regardless of whether or
-- not the attacks on SHA-1 will affect DNSSEC, it is believed (at the
-- time of this writing) that SHA-256 is the better choice for use in DS
-- records.
--
-- At the time of this publication, the SHA-256 digest algorithm is
-- considered sufficiently strong for the immediate future. It is also
-- considered sufficient for use in DNSSEC DS RRs for the immediate
-- future. However, future published attacks may weaken the usability
-- of this algorithm within the DS RRs. It is beyond the scope of this
-- document to speculate extensively on the cryptographic strength of
-- the SHA-256 digest algorithm.
--
-- Likewise, it is also beyond the scope of this document to specify
-- whether or for how long SHA-1 based DS records should be
-- simultaneously published alongside SHA-256 based DS records.
--
--
--7. Acknowledgments
--
-- This document is a minor extension to the existing DNSSEC documents
-- and those authors are gratefully appreciated for the hard work that
-- went into the base documents.
--
-- The following people contributed to portions of this document in some
-- fashion: Mark Andrews, Roy Arends, Olafur Gudmundsson, Paul Hoffman,
-- Olaf M. Kolkman, Edward Lewis, Scott Rose, Stuart E. Schechter, Sam
-- Weiler.
--
--
--
--
--
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--
--
--8. References
--
--8.1. Normative References
--
-- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
-- [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "DNS Security Introduction and Requirements",
-- RFC 4033, March 2005.
--
-- [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Resource Records for the DNS Security Extensions",
-- RFC 4034, March 2005.
--
-- [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Protocol Modifications for the DNS Security
-- Extensions", RFC 4035, March 2005.
--
-- [SHA256] National Institute of Standards and Technology, "Secure
-- Hash Algorithm. NIST FIPS 180-2", August 2002.
--
--8.2. Informative References
--
-- [SHA256CODE]
-- Eastlake, D., "US Secure Hash Algorithms (SHA)",
-- June 2005.
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--Hardaker Expires August 25, 2006 [Page 7]
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--Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006
--
--
--Author's Address
--
-- Wes Hardaker
-- Sparta
-- P.O. Box 382
-- Davis, CA 95617
-- US
--
-- Email: hardaker@tislabs.com
--
--
--
--
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--Hardaker Expires August 25, 2006 [Page 8]
--\f
--Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006
--
--
--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
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-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
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-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
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-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--
--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
-- except as set forth therein, the authors retain all their rights.
--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
--Hardaker Expires August 25, 2006 [Page 9]
--\f
+++ /dev/null
--
--
--
--
--
--
--DNSEXT Working Group Bernard Aboba
--INTERNET-DRAFT Dave Thaler
--Category: Standards Track Levon Esibov
--<draft-ietf-dnsext-mdns-46.txt> Microsoft Corporation
--16 April 2006
--
-- Linklocal Multicast Name Resolution (LLMNR)
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on October 15, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society 2006.
--
--Abstract
--
-- The goal of Link-Local Multicast Name Resolution (LLMNR) is to enable
-- name resolution in scenarios in which conventional DNS name
-- resolution is not possible. LLMNR supports all current and future
-- DNS formats, types and classes, while operating on a separate port
-- from DNS, and with a distinct resolver cache. Since LLMNR only
-- operates on the local link, it cannot be considered a substitute for
-- DNS.
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 1]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--Table of Contents
--
--1. Introduction .......................................... 3
-- 1.1 Requirements .................................... 4
-- 1.2 Terminology ..................................... 4
--2. Name Resolution Using LLMNR ........................... 4
-- 2.1 LLMNR Packet Format ............................. 5
-- 2.2 Sender Behavior ................................. 8
-- 2.3 Responder Behavior .............................. 8
-- 2.4 Unicast Queries and Responses ................... 11
-- 2.5 Off-link Detection .............................. 11
-- 2.6 Responder Responsibilities ...................... 12
-- 2.7 Retransmission and Jitter ....................... 13
-- 2.8 DNS TTL ......................................... 14
-- 2.9 Use of the Authority and Additional Sections .... 14
--3. Usage model ........................................... 15
-- 3.1 LLMNR Configuration ............................. 16
--4. Conflict Resolution ................................... 18
-- 4.1 Uniqueness Verification ......................... 18
-- 4.2 Conflict Detection and Defense .................. 19
-- 4.3 Considerations for Multiple Interfaces .......... 20
-- 4.4 API issues ...................................... 22
--5. Security Considerations ............................... 22
-- 5.1 Denial of Service ............................... 22
-- 5.2 Spoofing ...............,........................ 23
-- 5.3 Authentication .................................. 24
-- 5.4 Cache and Port Separation ....................... 24
--6. IANA considerations ................................... 25
--7. Constants ............................................. 25
--8. References ............................................ 26
-- 8.1 Normative References ............................ 26
-- 8.2 Informative References .......................... 26
--Acknowledgments .............................................. 28
--Authors' Addresses ........................................... 28
--Intellectual Property Statement .............................. 29
--Disclaimer of Validity ....................................... 29
--Copyright Statement .......................................... 29
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 2]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--1. Introduction
--
-- This document discusses Link Local Multicast Name Resolution (LLMNR),
-- which is based on the DNS packet format and supports all current and
-- future DNS formats, types and classes. LLMNR operates on a separate
-- port from the Domain Name System (DNS), with a distinct resolver
-- cache.
--
-- Since LLMNR only operates on the local link, it cannot be considered
-- a substitute for DNS. Link-scope multicast addresses are used to
-- prevent propagation of LLMNR traffic across routers, potentially
-- flooding the network. LLMNR queries can also be sent to a unicast
-- address, as described in Section 2.4.
--
-- Propagation of LLMNR packets on the local link is considered
-- sufficient to enable name resolution in small networks. In such
-- networks, if a network has a gateway, then typically the network is
-- able to provide DNS server configuration. Configuration issues are
-- discussed in Section 3.1.
--
-- In the future, it may be desirable to consider use of multicast name
-- resolution with multicast scopes beyond the link-scope. This could
-- occur if LLMNR deployment is successful, the need arises for
-- multicast name resolution beyond the link-scope, or multicast routing
-- becomes ubiquitous. For example, expanded support for multicast name
-- resolution might be required for mobile ad-hoc networks.
--
-- Once we have experience in LLMNR deployment in terms of
-- administrative issues, usability and impact on the network, it will
-- be possible to reevaluate which multicast scopes are appropriate for
-- use with multicast name resolution. IPv4 administratively scoped
-- multicast usage is specified in "Administratively Scoped IP
-- Multicast" [RFC2365].
--
-- Service discovery in general, as well as discovery of DNS servers
-- using LLMNR in particular, is outside of the scope of this document,
-- as is name resolution over non-multicast capable media.
--
--1.1. Requirements
--
-- In this document, several words are used to signify the requirements
-- of the specification. The key words "MUST", "MUST NOT", "REQUIRED",
-- "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
-- and "OPTIONAL" in this document are to be interpreted as described in
-- [RFC2119].
--
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 3]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--1.2. Terminology
--
-- This document assumes familiarity with DNS terminology defined in
-- [RFC1035]. Other terminology used in this document includes:
--
--Routable Address
-- An address other than a Link-Local address. This includes globally
-- routable addresses, as well as private addresses.
--
--Reachable
-- An LLMNR responder considers one of its addresses reachable over a
-- link if it will respond to an ARP or Neighbor Discovery query for
-- that address received on that link.
--
--Responder
-- A host that listens to LLMNR queries, and responds to those for
-- which it is authoritative.
--
--Sender
-- A host that sends an LLMNR query.
--
--UNIQUE
-- There are some scenarios when multiple responders may respond to
-- the same query. There are other scenarios when only one responder
-- may respond to a query. Names for which only a single responder is
-- anticipated are referred to as UNIQUE. Name uniqueness is
-- configured on the responder, and therefore uniqueness verification
-- is the responder's responsibility.
--
--2. Name Resolution Using LLMNR
--
-- LLMNR queries are sent to and received on port 5355. The IPv4 link-
-- scope multicast address a given responder listens to, and to which a
-- sender sends queries, is 224.0.0.252. The IPv6 link-scope multicast
-- address a given responder listens to, and to which a sender sends all
-- queries, is FF02:0:0:0:0:0:1:3.
--
-- Typically a host is configured as both an LLMNR sender and a
-- responder. A host MAY be configured as a sender, but not a
-- responder. However, a host configured as a responder MUST act as a
-- sender, if only to verify the uniqueness of names as described in
-- Section 4. This document does not specify how names are chosen or
-- configured. This may occur via any mechanism, including DHCPv4
-- [RFC2131] or DHCPv6 [RFC3315].
--
-- A typical sequence of events for LLMNR usage is as follows:
--
-- [a] An LLMNR sender sends an LLMNR query to the link-scope
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 4]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- multicast address(es), unless a unicast query is indicated,
-- as specified in Section 2.4.
--
-- [b] A responder responds to this query only if it is authoritative
-- for the name in the query. A responder responds to a
-- multicast query by sending a unicast UDP response to the sender.
-- Unicast queries are responded to as indicated in Section 2.4.
--
-- [c] Upon reception of the response, the sender processes it.
--
-- The sections that follow provide further details on sender and
-- responder behavior.
--
--2.1. LLMNR Packet Format
--
-- LLMNR is based on the DNS packet format defined in [RFC1035] Section
-- 4 for both queries and responses. LLMNR implementations SHOULD send
-- UDP queries and responses only as large as are known to be
-- permissible without causing fragmentation. When in doubt a maximum
-- packet size of 512 octets SHOULD be used. LLMNR implementations MUST
-- accept UDP queries and responses as large as the smaller of the link
-- MTU or 9194 octets (Ethernet jumbo frame size of 9KB (9216) minus 22
-- octets for the header, VLAN tag and CRC).
--
--2.1.1. LLMNR Header Format
--
-- LLMNR queries and responses utilize the DNS header format defined in
-- [RFC1035] with exceptions noted below:
--
-- 1 1 1 1 1 1
-- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- | ID |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- |QR| Opcode | C|TC| T| Z| Z| Z| Z| RCODE |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- | QDCOUNT |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- | ANCOUNT |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- | NSCOUNT |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
-- | ARCOUNT |
-- +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
--
-- where:
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 5]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--ID A 16 bit identifier assigned by the program that generates any kind
-- of query. This identifier is copied from the query to the response
-- and can be used by the sender to match responses to outstanding
-- queries. The ID field in a query SHOULD be set to a pseudo-random
-- value. For advice on generation of pseudo-random values, please
-- consult [RFC1750].
--
--QR Query/Response. A one bit field, which if set indicates that the
-- message is an LLMNR response; if clear then the message is an LLMNR
-- query.
--
--OPCODE
-- A four bit field that specifies the kind of query in this message.
-- This value is set by the originator of a query and copied into the
-- response. This specification defines the behavior of standard
-- queries and responses (opcode value of zero). Future
-- specifications may define the use of other opcodes with LLMNR.
-- LLMNR senders and responders MUST support standard queries (opcode
-- value of zero). LLMNR queries with unsupported OPCODE values MUST
-- be silently discarded by responders.
--
--C Conflict. When set within a request, the 'C'onflict bit indicates
-- that a sender has received multiple LLMNR responses to this query.
-- In an LLMNR response, if the name is considered UNIQUE, then the
-- 'C' bit is clear, otherwise it is set. LLMNR senders do not
-- retransmit queries with the 'C' bit set. Responders MUST NOT
-- respond to LLMNR queries with the 'C' bit set, but may start the
-- uniqueness verification process, as described in Section 4.2.
--
--TC TrunCation - specifies that this message was truncated due to
-- length greater than that permitted on the transmission channel.
-- The TC bit MUST NOT be set in an LLMNR query and if set is ignored
-- by an LLMNR responder. If the TC bit is set in an LLMNR response,
-- then the sender SHOULD resend the LLMNR query over TCP using the
-- unicast address of the responder as the destination address. If
-- the sender receives a response to the TCP query, then it SHOULD
-- discard the UDP response with the TC bit set. See [RFC2181] and
-- Section 2.4 of this specification for further discussion of the TC
-- bit.
--
--T Tentative. The 'T'entative bit is set in a response if the
-- responder is authoritative for the name, but has not yet verified
-- the uniqueness of the name. A responder MUST ignore the 'T' bit in
-- a query, if set. A response with the 'T' bit set is silently
-- discarded by the sender, except if it is a uniqueness query, in
-- which case a conflict has been detected and a responder MUST
-- resolve the conflict as described in Section 4.1.
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 6]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--Z Reserved for future use. Implementations of this specification
-- MUST set these bits to zero in both queries and responses. If
-- these bits are set in a LLMNR query or response, implementations of
-- this specification MUST ignore them. Since reserved bits could
-- conceivably be used for different purposes than in DNS,
-- implementors are advised not to enable processing of these bits in
-- an LLMNR implementation starting from a DNS code base.
--
--RCODE
-- Response code -- this 4 bit field is set as part of LLMNR
-- responses. In an LLMNR query, the sender MUST set RCODE to zero;
-- the responder ignores the RCODE and assumes it to be zero. The
-- response to a multicast LLMNR query MUST have RCODE set to zero. A
-- sender MUST silently discard an LLMNR response with a non-zero
-- RCODE sent in response to a multicast query.
--
-- If an LLMNR responder is authoritative for the name in a multicast
-- query, but an error is encountered, the responder SHOULD send an
-- LLMNR response with an RCODE of zero, no RRs in the answer section,
-- and the TC bit set. This will cause the query to be resent using
-- TCP, and allow the inclusion of a non-zero RCODE in the response to
-- the TCP query. Responding with the TC bit set is preferable to not
-- sending a response, since it enables errors to be diagnosed. This
-- may be required, for example, when an LLMNR query includes a TSIG
-- RR in the additional section, and the responder encounters a
-- problem that requires returning a non-zero RCODE. TSIG error
-- conditions defined in [RFC2845] include a TSIG RR in an
-- unacceptable position (RCODE=1) or a TSIG RR which does not
-- validate (RCODE=9 with TSIG ERROR 17 (BADKEY) or 16 (BADSIG)).
--
-- Since LLMNR responders only respond to LLMNR queries for names for
-- which they are authoritative, LLMNR responders MUST NOT respond
-- with an RCODE of 3; instead, they should not respond at all.
--
-- LLMNR implementations MUST support EDNS0 [RFC2671] and extended
-- RCODE values.
--
--QDCOUNT
-- An unsigned 16 bit integer specifying the number of entries in the
-- question section. A sender MUST place only one question into the
-- question section of an LLMNR query. LLMNR responders MUST silently
-- discard LLMNR queries with QDCOUNT not equal to one. LLMNR senders
-- MUST silently discard LLMNR responses with QDCOUNT not equal to
-- one.
--
--ANCOUNT
-- An unsigned 16 bit integer specifying the number of resource
-- records in the answer section. LLMNR responders MUST silently
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 7]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- discard LLMNR queries with ANCOUNT not equal to zero.
--
--NSCOUNT
-- An unsigned 16 bit integer specifying the number of name server
-- resource records in the authority records section. Authority
-- record section processing is described in Section 2.9. LLMNR
-- responders MUST silently discard LLMNR queries with NSCOUNT not
-- equal to zero.
--
--ARCOUNT
-- An unsigned 16 bit integer specifying the number of resource
-- records in the additional records section. Additional record
-- section processing is described in Section 2.9.
--
--2.2. Sender Behavior
--
-- A sender MAY send an LLMNR query for any legal resource record type
-- (e.g., A, AAAA, PTR, SRV, etc.) to the link-scope multicast address.
-- As described in Section 2.4, a sender MAY also send a unicast query.
--
-- The sender MUST anticipate receiving no replies to some LLMNR
-- queries, in the event that no responders are available within the
-- link-scope. If no response is received, a resolver treats it as a
-- response that the name does not exist (RCODE=3 is returned). A
-- sender can handle duplicate responses by discarding responses with a
-- source IP address and ID field that duplicate a response already
-- received.
--
-- When multiple valid LLMNR responses are received with the 'C' bit
-- set, they SHOULD be concatenated and treated in the same manner that
-- multiple RRs received from the same DNS server would be. However,
-- responses with the 'C' bit set SHOULD NOT be concatenated with
-- responses with the 'C' bit clear; instead, only the responses with
-- the 'C' bit set SHOULD be returned. If valid LLMNR response(s) are
-- received along with error response(s), then the error responses are
-- silently discarded.
--
-- Since the responder may order the RRs in the response so as to
-- indicate preference, the sender SHOULD preserve ordering in the
-- response to the querying application.
--
--2.3. Responder Behavior
--
-- An LLMNR response MUST be sent to the sender via unicast.
--
-- Upon configuring an IP address, responders typically will synthesize
-- corresponding A, AAAA and PTR RRs so as to be able to respond to
-- LLMNR queries for these RRs. An SOA RR is synthesized only when a
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 8]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- responder has another RR in addition to the SOA RR; the SOA RR MUST
-- NOT be the only RR that a responder has. However, in general whether
-- RRs are manually or automatically created is an implementation
-- decision.
--
-- For example, a host configured to have computer name "host1" and to
-- be a member of the "example.com" domain, and with IPv4 address
-- 192.0.2.1 and IPv6 address 2001:0DB8::1:2:3:FF:FE:4:5:6 might be
-- authoritative for the following records:
--
-- host1. IN A 192.0.2.1
-- IN AAAA 2001:0DB8::1:2:3:FF:FE:4:5:6
--
-- host1.example.com. IN A 192.0.2.1
-- IN AAAA 2001:0DB8::1:2:3:FF:FE:4:5:6
--
-- 1.2.0.192.in-addr.arpa. IN PTR host1.
-- IN PTR host1.example.com.
--
-- 6.0.5.0.4.0.E.F.F.F.3.0.2.0.1.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.
-- ip6.arpa IN PTR host1. (line split for formatting reasons)
-- IN PTR host1.example.com.
--
-- An LLMNR responder might be further manually configured with the name
-- of a local mail server with an MX RR included in the "host1." and
-- "host1.example.com." records.
--
-- In responding to queries:
--
--[a] Responders MUST listen on UDP port 5355 on the link-scope multicast
-- address(es) defined in Section 2, and on TCP port 5355 on the
-- unicast address(es) that could be set as the source address(es)
-- when the responder responds to the LLMNR query.
--
--[b] Responders MUST direct responses to the port from which the query
-- was sent. When queries are received via TCP this is an inherent
-- part of the transport protocol. For queries received by UDP the
-- responder MUST take note of the source port and use that as the
-- destination port in the response. Responses MUST always be sent
-- from the port to which they were directed.
--
--[c] Responders MUST respond to LLMNR queries for names and addresses
-- they are authoritative for. This applies to both forward and
-- reverse lookups, with the exception of queries with the 'C' bit
-- set, which do not elicit a response.
--
--[d] Responders MUST NOT respond to LLMNR queries for names they are not
-- authoritative for.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 9]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--[e] Responders MUST NOT respond using data from the LLMNR or DNS
-- resolver cache.
--
--[f] If a DNS server is running on a host that supports LLMNR, the DNS
-- server MUST respond to LLMNR queries only for the RRSets relating
-- to the host on which the server is running, but MUST NOT respond
-- for other records for which the server is authoritative. DNS
-- servers also MUST NOT send LLMNR queries in order to resolve DNS
-- queries.
--
--[g] If a responder is authoritative for a name, it MUST respond with
-- RCODE=0 and an empty answer section, if the type of query does not
-- match a RR that the responder has.
--
-- As an example, a host configured to respond to LLMNR queries for the
-- name "foo.example.com." is authoritative for the name
-- "foo.example.com.". On receiving an LLMNR query for an A RR with the
-- name "foo.example.com." the host authoritatively responds with A
-- RR(s) that contain IP address(es) in the RDATA of the resource
-- record. If the responder has a AAAA RR, but no A RR, and an A RR
-- query is received, the responder would respond with RCODE=0 and an
-- empty answer section.
--
-- In conventional DNS terminology a DNS server authoritative for a zone
-- is authoritative for all the domain names under the zone apex except
-- for the branches delegated into separate zones. Contrary to
-- conventional DNS terminology, an LLMNR responder is authoritative
-- only for the zone apex.
--
-- For example the host "foo.example.com." is not authoritative for the
-- name "child.foo.example.com." unless the host is configured with
-- multiple names, including "foo.example.com." and
-- "child.foo.example.com.". As a result, "foo.example.com." cannot
-- reply to an LLMNR query for "child.foo.example.com." with RCODE=3
-- (authoritative name error). The purpose of limiting the name
-- authority scope of a responder is to prevent complications that could
-- be caused by coexistence of two or more hosts with the names
-- representing child and parent (or grandparent) nodes in the DNS tree,
-- for example, "foo.example.com." and "child.foo.example.com.".
--
-- Without the restriction on authority an LLMNR query for an A resource
-- record for the name "child.foo.example.com." would result in two
-- authoritative responses: RCODE=3 (authoritative name error) received
-- from "foo.example.com.", and a requested A record - from
-- "child.foo.example.com.". To prevent this ambiguity, LLMNR enabled
-- hosts could perform a dynamic update of the parent (or grandparent)
-- zone with a delegation to a child zone; for example a host
-- "child.foo.example.com." could send a dynamic update for the NS and
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 10]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- glue A record to "foo.example.com.". However, this approach
-- significantly complicates implementation of LLMNR and would not be
-- acceptable for lightweight hosts.
--
--2.4. Unicast Queries and Responses
--
-- Unicast queries SHOULD be sent when:
--
-- [a] A sender repeats a query after it received a response
-- with the TC bit set to the previous LLMNR multicast query, or
--
-- [b] The sender queries for a PTR RR of a fully formed IP address
-- within the "in-addr.arpa" or "ip6.arpa" zones.
--
-- Unicast LLMNR queries MUST be done using TCP and the responses MUST
-- be sent using the same TCP connection as the query. Senders MUST
-- support sending TCP queries, and responders MUST support listening
-- for TCP queries. If the sender of a TCP query receives a response to
-- that query not using TCP, the response MUST be silently discarded.
--
-- Unicast UDP queries MUST be silently discarded.
--
-- A unicast PTR RR query for an off-link address will not elicit a
-- response, but instead an ICMP TTL or Hop Limit exceeded message will
-- be received. An implementation receiving an ICMP message in response
-- to a TCP connection setup attempt can return immediately, treating
-- this as a response that no such name exists (RCODE=3 is returned).
-- An implementation that cannot process ICMP messages MAY send
-- multicast UDP queries for PTR RRs. Since TCP implementations will
-- not retransmit prior to RTOmin, a considerable period will elapse
-- before TCP retransmits multiple times, resulting in a long timeout
-- for TCP PTR RR queries sent to an off-link destination.
--
--2.5. "Off link" Detection
--
-- A sender MUST select a source address for LLMNR queries that is
-- assigned on the interface on which the query is sent. The
-- destination address of an LLMNR query MUST be a link-scope multicast
-- address or a unicast address.
--
-- A responder MUST select a source address for responses that is
-- assigned on the interface on which the query was received. The
-- destination address of an LLMNR response MUST be a unicast address.
--
-- On receiving an LLMNR query, the responder MUST check whether it was
-- sent to a LLMNR multicast addresses defined in Section 2. If it was
-- sent to another multicast address, then the query MUST be silently
-- discarded.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 11]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- Section 2.4 discusses use of TCP for LLMNR queries and responses. In
-- composing an LLMNR query using TCP, the sender MUST set the Hop Limit
-- field in the IPv6 header and the TTL field in the IPv4 header of the
-- response to one (1). The responder SHOULD set the TTL or Hop Limit
-- settings on the TCP listen socket to one (1) so that SYN-ACK packets
-- will have TTL (IPv4) or Hop Limit (IPv6) set to one (1). This
-- prevents an incoming connection from off-link since the sender will
-- not receive a SYN-ACK from the responder.
--
-- For UDP queries and responses, the Hop Limit field in the IPv6 header
-- and the TTL field in the IPV4 header MAY be set to any value.
-- However, it is RECOMMENDED that the value 255 be used for
-- compatibility with early implementations of [RFC3927].
--
-- Implementation note:
--
-- In the sockets API for IPv4 [POSIX], the IP_TTL and
-- IP_MULTICAST_TTL socket options are used to set the TTL of
-- outgoing unicast and multicast packets. The IP_RECVTTL socket
-- option is available on some platforms to retrieve the IPv4 TTL of
-- received packets with recvmsg(). [RFC2292] specifies similar
-- options for setting and retrieving the IPv6 Hop Limit.
--
--2.6. Responder Responsibilities
--
-- It is the responsibility of the responder to ensure that RRs returned
-- in LLMNR responses MUST only include values that are valid on the
-- local interface, such as IPv4 or IPv6 addresses valid on the local
-- link or names defended using the mechanism described in Section 4.
-- IPv4 Link-Local addresses are defined in [RFC3927]. IPv6 Link-Local
-- addresses are defined in [RFC2373]. In particular:
--
-- [a] If a link-scope IPv6 address is returned in a AAAA RR,
-- that address MUST be valid on the local link over which
-- LLMNR is used.
--
-- [b] If an IPv4 address is returned, it MUST be reachable
-- through the link over which LLMNR is used.
--
-- [c] If a name is returned (for example in a CNAME, MX
-- or SRV RR), the name MUST be resolvable on the local
-- link over which LLMNR is used.
--
-- Where multiple addresses represent valid responses to a query, the
-- order in which the addresses are returned is as follows:
--
-- [d] If the source address of the query is a link-scope address,
-- then the responder SHOULD include a link-scope address first
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 12]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- in the response, if available.
--
-- [e] If the source address of the query is a routable address,
-- then the responder MUST include a routable address first
-- in the response, if available.
--
--2.7. Retransmission and Jitter
--
-- An LLMNR sender uses the timeout interval LLMNR_TIMEOUT to determine
-- when to retransmit an LLMNR query. An LLMNR sender SHOULD either
-- estimate the LLMNR_TIMEOUT for each interface, or set a reasonably
-- high initial timeout. Suggested constants are described in Section
-- 7.
--
-- If an LLMNR query sent over UDP is not resolved within LLMNR_TIMEOUT,
-- then a sender SHOULD repeat the transmission of the query in order to
-- assure that it was received by a host capable of responding to it.
-- An LLMNR query SHOULD NOT be sent more than three times.
--
-- Where LLMNR queries are sent using TCP, retransmission is handled by
-- the transport layer. Queries with the 'C' bit set MUST be sent using
-- multicast UDP and MUST NOT be retransmitted.
--
-- An LLMNR sender cannot know in advance if a query sent using
-- multicast will receive no response, one response, or more than one
-- response. An LLMNR sender MUST wait for LLMNR_TIMEOUT if no response
-- has been received, or if it is necessary to collect all potential
-- responses, such as if a uniqueness verification query is being made.
-- Otherwise an LLMNR sender SHOULD consider a multicast query answered
-- after the first response is received, if that response has the 'C'
-- bit clear.
--
-- However, if the first response has the 'C' bit set, then the sender
-- SHOULD wait for LLMNR_TIMEOUT + JITTER_INTERVAL in order to collect
-- all possible responses. When multiple valid answers are received,
-- they may first be concatenated, and then treated in the same manner
-- that multiple RRs received from the same DNS server would. A unicast
-- query sender considers the query answered after the first response is
-- received.
--
-- Since it is possible for a response with the 'C' bit clear to be
-- followed by a response with the 'C' bit set, an LLMNR sender SHOULD
-- be prepared to process additional responses for the purposes of
-- conflict detection, even after it has considered a query answered.
--
-- In order to avoid synchronization, the transmission of each LLMNR
-- query and response SHOULD delayed by a time randomly selected from
-- the interval 0 to JITTER_INTERVAL. This delay MAY be avoided by
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 13]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- responders responding with names which they have previously
-- determined to be UNIQUE (see Section 4 for details).
--
--2.8. DNS TTL
--
-- The responder should insert a pre-configured TTL value in the records
-- returned in an LLMNR response. A default value of 30 seconds is
-- RECOMMENDED. In highly dynamic environments (such as mobile ad-hoc
-- networks), the TTL value may need to be reduced.
--
-- Due to the TTL minimalization necessary when caching an RRset, all
-- TTLs in an RRset MUST be set to the same value.
--
--2.9. Use of the Authority and Additional Sections
--
-- Unlike the DNS, LLMNR is a peer-to-peer protocol and does not have a
-- concept of delegation. In LLMNR, the NS resource record type may be
-- stored and queried for like any other type, but it has no special
-- delegation semantics as it does in the DNS. Responders MAY have NS
-- records associated with the names for which they are authoritative,
-- but they SHOULD NOT include these NS records in the authority
-- sections of responses.
--
-- Responders SHOULD insert an SOA record into the authority section of
-- a negative response, to facilitate negative caching as specified in
-- [RFC2308]. The TTL of this record is set from the minimum of the
-- MINIMUM field of the SOA record and the TTL of the SOA itself, and
-- indicates how long a resolver may cache the negative answer. The
-- owner name of the SOA record (MNAME) MUST be set to the query name.
-- The RNAME, SERIAL, REFRESH, RETRY and EXPIRE values MUST be ignored
-- by senders. Negative responses without SOA records SHOULD NOT be
-- cached.
--
-- In LLMNR, the additional section is primarily intended for use by
-- EDNS0, TSIG and SIG(0). As a result, unless the 'C' bit is set,
-- senders MAY only include pseudo RR-types in the additional section of
-- a query; unless the 'C' bit is set, responders MUST ignore the
-- additional section of queries containing other RR types.
--
-- In queries where the 'C' bit is set, the sender SHOULD include the
-- conflicting RRs in the additional section. Since conflict
-- notifications are advisory, responders SHOULD log information from
-- the additional section, but otherwise MUST ignore the additional
-- section.
--
-- Senders MUST NOT cache RRs from the authority or additional section
-- of a response as answers, though they may be used for other purposes
-- such as negative caching.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 14]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--3. Usage Model
--
-- LLMNR is a peer-to-peer name resolution protocol that is not intended
-- as a replacement for DNS; rather, it enables name resolution in
-- scenarios in which conventional DNS name resolution is not possible.
-- This includes situations in which hosts are not configured with the
-- address of a DNS server; where the DNS server is unavailable or
-- unreachable; where there is no DNS server authoritative for the name
-- of a host, or where the authoritative DNS server does not have the
-- desired RRs.
--
-- By default, an LLMNR sender SHOULD send LLMNR queries only for
-- single-label names. In order to reduce unnecessary DNS queries, stub
-- resolvers supporting both DNS and LLMNR SHOULD avoid sending DNS
-- queries for single-label names. An LLMNR sender SHOULD NOT be
-- enabled to send a query for any name, except where security
-- mechanisms (described in Section 5.3) can be utilized.
--
-- Regardless of whether security mechanisms can be utilized, LLMNR
-- queries SHOULD NOT be sent unless one of the following conditions are
-- met:
--
-- [1] No manual or automatic DNS configuration has been performed.
-- If DNS server address(es) have been configured, a
-- host SHOULD attempt to reach DNS servers over all protocols
-- on which DNS server address(es) are configured, prior to sending
-- LLMNR queries. For dual stack hosts configured with DNS server
-- address(es) for one protocol but not another, this implies that
-- DNS queries SHOULD be sent over the protocol configured with
-- a DNS server, prior to sending LLMNR queries.
--
-- [2] All attempts to resolve the name via DNS on all interfaces
-- have failed after exhausting the searchlist. This can occur
-- because DNS servers did not respond, or because they
-- responded to DNS queries with RCODE=3 (Authoritative Name
-- Error) or RCODE=0, and an empty answer section. Where a
-- single resolver call generates DNS queries for A and AAAA RRs,
-- an implementation MAY choose not to send LLMNR queries if any
-- of the DNS queries is successful. An LLMNR query SHOULD only
-- be sent for the originally requested name; a searchlist
-- is not used to form additional LLMNR queries.
--
-- Since LLMNR is a secondary name resolution mechanism, its usage is in
-- part determined by the behavior of DNS implementations. In general,
-- robust DNS resolver implementations are more likely to avoid
-- unnecessary LLMNR queries.
--
-- As noted in [DNSPerf], even when DNS servers are configured, a
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 15]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- significant fraction of DNS queries do not receive a response, or
-- result in negative responses due to missing inverse mappings or NS
-- records that point to nonexistent or inappropriate hosts. This has
-- the potential to result in a large number of unnecessary LLMNR
-- queries.
--
-- [RFC1536] describes common DNS implementation errors and fixes. If
-- the proposed fixes are implemented, unnecessary LLMNR queries will be
-- reduced substantially, and so implementation of [RFC1536] is
-- recommended.
--
-- For example, [RFC1536] Section 1 describes issues with retransmission
-- and recommends implementation of a retransmission policy based on
-- round trip estimates, with exponential back-off. [RFC1536] Section 4
-- describes issues with failover, and recommends that resolvers try
-- another server when they don't receive a response to a query. These
-- policies are likely to avoid unnecessary LLMNR queries.
--
-- [RFC1536] Section 3 describes zero answer bugs, which if addressed
-- will also reduce unnecessary LLMNR queries.
--
-- [RFC1536] Section 6 describes name error bugs and recommended
-- searchlist processing that will reduce unnecessary RCODE=3
-- (authoritative name) errors, thereby also reducing unnecessary LLMNR
-- queries.
--
-- If error responses are received from both DNS and LLMNR, then the
-- lowest RCODE value should be returned. For example, if either DNS or
-- LLMNR receives a response with RCODE=0, then this should returned to
-- the caller.
--
--3.1. LLMNR Configuration
--
-- LLMNR usage MAY be configured manually or automatically on a per
-- interface basis. By default, LLMNR responders SHOULD be enabled on
-- all interfaces, at all times. Enabling LLMNR for use in situations
-- where a DNS server has been configured will result in a change in
-- default behavior without a simultaneous update to configuration
-- information. Where this is considered undesirable, LLMNR SHOULD NOT
-- be enabled by default, so that hosts will neither listen on the link-
-- scope multicast address, nor will they send queries to that address.
--
-- Since IPv4 and IPv6 utilize distinct configuration mechanisms, it is
-- possible for a dual stack host to be configured with the address of a
-- DNS server over IPv4, while remaining unconfigured with a DNS server
-- suitable for use over IPv6.
--
-- In these situations, a dual stack host will send AAAA queries to the
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 16]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- configured DNS server over IPv4. However, an IPv6-only host
-- unconfigured with a DNS server suitable for use over IPv6 will be
-- unable to resolve names using DNS. Automatic IPv6 DNS configuration
-- mechanisms (such as [RFC3315] and [DNSDisc]) are not yet widely
-- deployed, and not all DNS servers support IPv6. Therefore lack of
-- IPv6 DNS configuration may be a common problem in the short term, and
-- LLMNR may prove useful in enabling link-local name resolution over
-- IPv6.
--
-- Where a DHCPv4 server is available but not a DHCPv6 server [RFC3315],
-- IPv6-only hosts may not be configured with a DNS server. Where there
-- is no DNS server authoritative for the name of a host or the
-- authoritative DNS server does not support dynamic client update over
-- IPv6 or DHCPv6-based dynamic update, then an IPv6-only host will not
-- be able to do DNS dynamic update, and other hosts will not be able to
-- resolve its name.
--
-- For example, if the configured DNS server responds to a AAAA RR query
-- sent over IPv4 or IPv6 with an authoritative name error (RCODE=3) or
-- RCODE=0 and an empty answer section, then a AAAA RR query sent using
-- LLMNR over IPv6 may be successful in resolving the name of an
-- IPv6-only host on the local link.
--
-- Similarly, if a DHCPv4 server is available providing DNS server
-- configuration, and DNS server(s) exist which are authoritative for
-- the A RRs of local hosts and support either dynamic client update
-- over IPv4 or DHCPv4-based dynamic update, then the names of local
-- IPv4 hosts can be resolved over IPv4 without LLMNR. However, if no
-- DNS server is authoritative for the names of local hosts, or the
-- authoritative DNS server(s) do not support dynamic update, then LLMNR
-- enables linklocal name resolution over IPv4.
--
-- Where DHCPv4 or DHCPv6 is implemented, DHCP options can be used to
-- configure LLMNR on an interface. The LLMNR Enable Option, described
-- in [LLMNREnable], can be used to explicitly enable or disable use of
-- LLMNR on an interface. The LLMNR Enable Option does not determine
-- whether or in which order DNS itself is used for name resolution.
-- The order in which various name resolution mechanisms should be used
-- can be specified using the Name Service Search Option (NSSO) for DHCP
-- [RFC2937], using the LLMNR Enable Option code carried in the NSSO
-- data.
--
-- It is possible that DNS configuration mechanisms will go in and out
-- of service. In these circumstances, it is possible for hosts within
-- an administrative domain to be inconsistent in their DNS
-- configuration.
--
-- For example, where DHCP is used for configuring DNS servers, one or
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 17]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- more DHCP servers can fail. As a result, hosts configured prior to
-- the outage will be configured with a DNS server, while hosts
-- configured after the outage will not. Alternatively, it is possible
-- for the DNS configuration mechanism to continue functioning while
-- configured DNS servers fail.
--
-- An outage in the DNS configuration mechanism may result in hosts
-- continuing to use LLMNR even once the outage is repaired. Since
-- LLMNR only enables linklocal name resolution, this represents a
-- degradation in capabilities. As a result, hosts without a configured
-- DNS server may wish to periodically attempt to obtain DNS
-- configuration if permitted by the configuration mechanism in use. In
-- the absence of other guidance, a default retry interval of one (1)
-- minute is RECOMMENDED.
--
--4. Conflict Resolution
--
-- By default, a responder SHOULD be configured to behave as though its
-- name is UNIQUE on each interface on which LLMNR is enabled. However,
-- it is also possible to configure multiple responders to be
-- authoritative for the same name. For example, multiple responders
-- MAY respond to a query for an A or AAAA type record for a cluster
-- name (assigned to multiple hosts in the cluster).
--
-- To detect duplicate use of a name, an administrator can use a name
-- resolution utility which employs LLMNR and lists both responses and
-- responders. This would allow an administrator to diagnose behavior
-- and potentially to intervene and reconfigure LLMNR responders who
-- should not be configured to respond to the same name.
--
--4.1. Uniqueness Verification
--
-- Prior to sending an LLMNR response with the 'T' bit clear, a
-- responder configured with a UNIQUE name MUST verify that there is no
-- other host within the scope of LLMNR query propagation that is
-- authoritative for the same name on that interface.
--
-- Once a responder has verified that its name is UNIQUE, if it receives
-- an LLMNR query for that name, with the 'C' bit clear, it MUST
-- respond, with the 'T' bit clear. Prior to verifying that its name is
-- UNIQUE, a responder MUST set the 'T' bit in responses.
--
-- Uniqueness verification is carried out when the host:
--
-- - starts up or is rebooted
-- - wakes from sleep (if the network interface was inactive
-- during sleep)
-- - is configured to respond to LLMNR queries on an interface
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 18]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- enabled for transmission and reception of IP traffic
-- - is configured to respond to LLMNR queries using additional
-- UNIQUE resource records
-- - verifies the acquisition of a new IP address and configuration
-- on an interface
--
-- To verify uniqueness, a responder MUST send an LLMNR query with the
-- 'C' bit clear, over all protocols on which it responds to LLMNR
-- queries (IPv4 and/or IPv6). It is RECOMMENDED that responders verify
-- uniqueness of a name by sending a query for the name with type='ANY'.
--
-- If no response is received, the sender retransmits the query, as
-- specified in Section 2.7. If a response is received, the sender MUST
-- check if the source address matches the address of any of its
-- interfaces; if so, then the response is not considered a conflict,
-- since it originates from the sender. To avoid triggering conflict
-- detection, a responder that detects that it is connected to the same
-- link on multiple interfaces SHOULD set the 'C' bit in responses.
--
-- If a response is received with the 'T' bit clear, the responder MUST
-- NOT use the name in response to LLMNR queries received over any
-- protocol (IPv4 or IPv6). If a response is received with the 'T' bit
-- set, the responder MUST check if the source IP address in the
-- response, interpreted as an unsigned integer, is less than the source
-- IP address in the query. If so, the responder MUST NOT use the name
-- in response to LLMNR queries received over any protocol (IPv4 or
-- IPv6). For the purpose of uniqueness verification, the contents of
-- the answer section in a response is irrelevant.
--
-- Periodically carrying out uniqueness verification in an attempt to
-- detect name conflicts is not necessary, wastes network bandwidth, and
-- may actually be detrimental. For example, if network links are
-- joined only briefly, and are separated again before any new
-- communication is initiated, temporary conflicts are benign and no
-- forced reconfiguration is required. LLMNR responders SHOULD NOT
-- periodically attempt uniqueness verification.
--
--4.2. Conflict Detection and Defense
--
-- Hosts on disjoint network links may configure the same name for use
-- with LLMNR. If these separate network links are later joined or
-- bridged together, then there may be multiple hosts which are now on
-- the same link, trying to use the same name.
--
-- In order to enable ongoing detection of name conflicts, when an LLMNR
-- sender receives multiple LLMNR responses to a query, it MUST check if
-- the 'C' bit is clear in any of the responses. If so, the sender
-- SHOULD send another query for the same name, type and class, this
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 19]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- time with the 'C' bit set, with the potentially conflicting resource
-- records included in the additional section.
--
-- Queries with the 'C' bit set are considered advisory and responders
-- MUST verify the existence of a conflict before acting on it. A
-- responder receiving a query with the 'C' bit set MUST NOT respond.
--
-- If the query is for a UNIQUE name, then the responder MUST send its
-- own query for the same name, type and class, with the 'C' bit clear.
-- If a response is received, the sender MUST check if the source
-- address matches the address of any of its interfaces; if so, then the
-- response is not considered a conflict, since it originates from the
-- sender. To avoid triggering conflict detection, a responder that
-- detects that it is connected to the same link on multiple interfaces
-- SHOULD set the 'C' bit in responses.
--
-- An LLMNR responder MUST NOT ignore conflicts once detected and SHOULD
-- log them. Upon detecting a conflict, an LLMNR responder MUST
-- immediately stop using the conflicting name in response to LLMNR
-- queries received over any supported protocol, if the source IP
-- address in the response, interpreted as an unsigned integer, is less
-- than the source IP address in the uniqueness verification query.
--
-- After stopping the use of a name, the responder MAY elect to
-- configure a new name. However, since name reconfiguration may be
-- disruptive, this is not required, and a responder may have been
-- configured to respond to multiple names so that alternative names may
-- already be available. A host that has stopped the use of a name may
-- attempt uniqueness verification again after the expiration of the TTL
-- of the conflicting response.
--
--4.3. Considerations for Multiple Interfaces
--
-- A multi-homed host may elect to configure LLMNR on only one of its
-- active interfaces. In many situations this will be adequate.
-- However, should a host need to configure LLMNR on more than one of
-- its active interfaces, there are some additional precautions it MUST
-- take. Implementers who are not planning to support LLMNR on multiple
-- interfaces simultaneously may skip this section.
--
-- Where a host is configured to issue LLMNR queries on more than one
-- interface, each interface maintains its own independent LLMNR
-- resolver cache, containing the responses to LLMNR queries.
--
-- A multi-homed host checks the uniqueness of UNIQUE records as
-- described in Section 4. The situation is illustrated in figure 1.
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 20]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- ---------- ----------
-- | | | |
-- [A] [myhost] [myhost]
--
-- Figure 1. Link-scope name conflict
--
-- In this situation, the multi-homed myhost will probe for, and defend,
-- its host name on both interfaces. A conflict will be detected on one
-- interface, but not the other. The multi-homed myhost will not be
-- able to respond with a host RR for "myhost" on the interface on the
-- right (see Figure 1). The multi-homed host may, however, be
-- configured to use the "myhost" name on the interface on the left.
--
-- Since names are only unique per-link, hosts on different links could
-- be using the same name. If an LLMNR client sends requests over
-- multiple interfaces, and receives replies from more than one, the
-- result returned to the client is defined by the implementation. The
-- situation is illustrated in figure 2.
--
-- ---------- ----------
-- | | | |
-- [A] [myhost] [A]
--
--
-- Figure 2. Off-segment name conflict
--
-- If host myhost is configured to use LLMNR on both interfaces, it will
-- send LLMNR queries on both interfaces. When host myhost sends a
-- query for the host RR for name "A" it will receive a response from
-- hosts on both interfaces.
--
-- Host myhost cannot distinguish between the situation shown in Figure
-- 2, and that shown in Figure 3 where no conflict exists.
--
-- [A]
-- | |
-- ----- -----
-- | |
-- [myhost]
--
-- Figure 3. Multiple paths to same host
--
-- This illustrates that the proposed name conflict resolution mechanism
-- does not support detection or resolution of conflicts between hosts
-- on different links. This problem can also occur with DNS when a
-- multi-homed host is connected to two different networks with
-- separated name spaces. It is not the intent of this document to
-- address the issue of uniqueness of names within DNS.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 21]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--4.4. API Issues
--
-- [RFC2553] provides an API which can partially solve the name
-- ambiguity problem for applications written to use this API, since the
-- sockaddr_in6 structure exposes the scope within which each scoped
-- address exists, and this structure can be used for both IPv4 (using
-- v4-mapped IPv6 addresses) and IPv6 addresses.
--
-- Following the example in Figure 2, an application on 'myhost' issues
-- the request getaddrinfo("A", ...) with ai_family=AF_INET6 and
-- ai_flags=AI_ALL|AI_V4MAPPED. LLMNR requests will be sent from both
-- interfaces and the resolver library will return a list containing
-- multiple addrinfo structures, each with an associated sockaddr_in6
-- structure. This list will thus contain the IPv4 and IPv6 addresses
-- of both hosts responding to the name 'A'. Link-local addresses will
-- have a sin6_scope_id value that disambiguates which interface is used
-- to reach the address. Of course, to the application, Figures 2 and 3
-- are still indistinguishable, but this API allows the application to
-- communicate successfully with any address in the list.
--
--5. Security Considerations
--
-- LLMNR is a peer-to-peer name resolution protocol designed for use on
-- the local link. While LLMNR limits the vulnerability of responders
-- to off-link senders, it is possible for an off-link responder to
-- reach a sender.
--
-- In scenarios such as public "hotspots" attackers can be present on
-- the same link. These threats are most serious in wireless networks
-- such as 802.11, since attackers on a wired network will require
-- physical access to the network, while wireless attackers may mount
-- attacks from a distance. Link-layer security such as [IEEE-802.11i]
-- can be of assistance against these threats if it is available.
--
-- This section details security measures available to mitigate threats
-- from on and off-link attackers.
--
--5.1. Denial of Service
--
-- Attackers may take advantage of LLMNR conflict detection by
-- allocating the same name, denying service to other LLMNR responders
-- and possibly allowing an attacker to receive packets destined for
-- other hosts. By logging conflicts, LLMNR responders can provide
-- forensic evidence of these attacks.
--
-- An attacker may spoof LLMNR queries from a victim's address in order
-- to mount a denial of service attack. Responders setting the IPv6 Hop
-- Limit or IPv4 TTL field to a value larger than one in an LLMNR UDP
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 22]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- response may be able to reach the victim across the Internet.
--
-- While LLMNR responders only respond to queries for which they are
-- authoritative and LLMNR does not provide wildcard query support, an
-- LLMNR response may be larger than the query, and an attacker can
-- generate multiple responses to a query for a name used by multiple
-- responders. A sender may protect itself against unsolicited
-- responses by silently discarding them as rapidly as possible.
--
--5.2. Spoofing
--
-- LLMNR is designed to prevent reception of queries sent by an off-link
-- attacker. LLMNR requires that responders receiving UDP queries check
-- that they are sent to a link-scope multicast address. However, it is
-- possible that some routers may not properly implement link-scope
-- multicast, or that link-scope multicast addresses may leak into the
-- multicast routing system. To prevent successful setup of TCP
-- connections by an off-link sender, responders receiving a TCP SYN
-- reply with a TCP SYN-ACK with TTL set to one (1).
--
-- While it is difficult for an off-link attacker to send an LLMNR query
-- to a responder, it is possible for an off-link attacker to spoof a
-- response to a query (such as an A or AAAA query for a popular
-- Internet host), and by using a TTL or Hop Limit field larger than one
-- (1), for the forged response to reach the LLMNR sender. Since the
-- forged response will only be accepted if it contains a matching ID
-- field, choosing a pseudo-random ID field within queries provides some
-- protection against off-link responders.
--
-- Since LLMNR queries can be sent when DNS server(s) do not respond, an
-- attacker can execute a denial of service attack on the DNS server(s)
-- and then poison the LLMNR cache by responding to an LLMNR query with
-- incorrect information. As noted in "Threat Analysis of the Domain
-- Name System (DNS)" [RFC3833] these threats also exist with DNS, since
-- DNS response spoofing tools are available that can allow an attacker
-- to respond to a query more quickly than a distant DNS server.
-- However, while switched networks or link layer security may make it
-- difficult for an on-link attacker to snoop unicast DNS queries,
-- multicast LLMNR queries are propagated to all hosts on the link,
-- making it possible for an on-link attacker to spoof LLMNR responses
-- without having to guess the value of the ID field in the query.
--
-- Since LLMNR queries are sent and responded to on the local-link, an
-- attacker will need to respond more quickly to provide its own
-- response prior to arrival of the response from a legitimate
-- responder. If an LLMNR query is sent for an off-link host, spoofing
-- a response in a timely way is not difficult, since a legitimate
-- response will never be received.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 23]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- This vulnerability can be reduced by limiting use of LLMNR to
-- resolution of single-label names as described in Section 3, or by
-- implementation of authentication (see Section 5.3).
--
--5.3. Authentication
--
-- LLMNR is a peer-to-peer name resolution protocol, and as a result,
-- it is often deployed in situations where no trust model can be
-- assumed. Where a pre-arranged security configuration is possible,
-- the following security mechanisms may be used:
--
--[a] LLMNR implementations MAY support TSIG [RFC2845] and/or SIG(0)
-- [RFC2931] security mechanisms. "DNS Name Service based on Secure
-- Multicast DNS for IPv6 Mobile Ad Hoc Networks" [LLMNRSec] describes
-- the use of TSIG to secure LLMNR, based on group keys. While group
-- keys can be used to demonstrate membership in a group, they do not
-- protect against forgery by an attacker that is a member of the
-- group.
--
--[b] IPsec ESP with a null-transform MAY be used to authenticate unicast
-- LLMNR queries and responses or LLMNR responses to multicast
-- queries. In a small network without a certificate authority, this
-- can be most easily accomplished through configuration of a group
-- pre-shared key for trusted hosts. As with TSIG, this does not
-- protect against forgery by an attacker with access to the group
-- pre-shared key.
--
--[c] LLMNR implementations MAY support DNSSEC [RFC4033]. In order to
-- support DNSSEC, LLMNR implementations MAY be configured with trust
-- anchors, or they MAY make use of keys obtained from DNS queries.
-- Since LLMNR does not support "delegated trust" (CD or AD bits),
-- LLMNR implementations cannot make use of DNSSEC unless they are
-- DNSSEC-aware and support validation. Unlike approaches [a] or [b],
-- DNSSEC permits a responder to demonstrate ownership of a name, not
-- just membership within a trusted group. As a result, it enables
-- protection against forgery.
--
--5.4. Cache and Port Separation
--
-- In order to prevent responses to LLMNR queries from polluting the DNS
-- cache, LLMNR implementations MUST use a distinct, isolated cache for
-- LLMNR on each interface. The use of separate caches is most
-- effective when LLMNR is used as a name resolution mechanism of last
-- resort, since this minimizes the opportunities for poisoning the
-- LLMNR cache, and decreases reliance on it.
--
-- LLMNR operates on a separate port from DNS, reducing the likelihood
-- that a DNS server will unintentionally respond to an LLMNR query.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 24]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
-- If LLMNR is given higher priority than DNS among the enabled name
-- resolution mechanisms, a denial of service attack on the DNS server
-- would not be necessary in order to poison the LLMNR cache, since
-- LLMNR queries would be sent even when the DNS server is available.
-- In addition, the LLMNR cache, once poisoned, would take precedence
-- over the DNS cache, eliminating the benefits of cache separation. As
-- a result, LLMNR SHOULD NOT be used as a primary name resolution
-- mechanism.
--
--6. IANA Considerations
--
-- LLMNR requires allocation of port 5355 for both TCP and UDP.
--
-- LLMNR requires allocation of link-scope multicast IPv4 address
-- 224.0.0.252, as well as link-scope multicast IPv6 address
-- FF02:0:0:0:0:0:1:3.
--
-- This specification creates two new name spaces: the LLMNR namespace
-- and the reserved bits in the LLMNR header. The reserved bits in the
-- LLMNR header are allocated by IETF Consensus, in accordance with BCP
-- 26 [RFC2434].
--
-- In order to to avoid creating any new administrative procedures,
-- administration of the LLMNR namespace will piggyback on the
-- administration of the DNS namespace.
--
-- The rights to use a fully qualified domain name (FQDN) within LLMNR
-- are obtained coincident with acquiring the rights to use that name
-- within DNS. Those wishing to use a FQDN within LLMNR should first
-- acquire the rights to use the corresponding FQDN within DNS. Using a
-- FQDN within LLMNR without ownership of the corresponding name in DNS
-- creates the possibility of conflict and therefore is discouraged.
--
-- LLMNR responders may self-allocate a name within the single-label
-- name space, first defined in [RFC1001]. Since single-label names are
-- not unique, no registration process is required.
--
--7. Constants
--
-- The following timing constants are used in this protocol; they are
-- not intended to be user configurable.
--
-- JITTER_INTERVAL 100 ms
-- LLMNR_TIMEOUT 1 second (if set statically on all interfaces)
-- 100 ms (IEEE 802 media, including IEEE 802.11)
--
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 25]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--8. References
--
--8.1. Normative References
--
--[RFC1001] Auerbach, K. and A. Aggarwal, "Protocol Standard for a NetBIOS
-- Service on a TCP/UDP Transport: Concepts and Methods", RFC
-- 1001, March 1987.
--
--[RFC1035] Mockapetris, P., "Domain Names - Implementation and
-- Specification", RFC 1035, November 1987.
--
--[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
--[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
-- Specification", RFC 2181, July 1997.
--
--[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)",
-- RFC 2308, March 1998.
--
--[RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing
-- Architecture", RFC 2373, July 1998.
--
--[RFC2434] Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA
-- Considerations Section in RFCs", BCP 26, RFC 2434, October
-- 1998.
--
--[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671,
-- August 1999.
--
--[RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
-- "Secret Key Transaction Authentication for DNS (TSIG)", RFC
-- 2845, May 2000.
--
--[RFC2931] Eastlake, D., "DNS Request and Transaction Signatures
-- (SIG(0)s)", RFC 2931, September 2000.
--
--8.2. Informative References
--
--[DNSPerf] Jung, J., et al., "DNS Performance and the Effectiveness of
-- Caching", IEEE/ACM Transactions on Networking, Volume 10,
-- Number 5, pp. 589, October 2002.
--
--[DNSDisc] Durand, A., Hagino, I. and D. Thaler, "Well known site local
-- unicast addresses to communicate with recursive DNS servers",
-- Internet draft (work in progress), draft-ietf-ipv6-dns-
-- discovery-07.txt, October 2002.
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 26]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--[IEEE-802.11i]
-- Institute of Electrical and Electronics Engineers, "Supplement
-- to Standard for Telecommunications and Information Exchange
-- Between Systems - LAN/MAN Specific Requirements - Part 11:
-- Wireless LAN Medium Access Control (MAC) and Physical Layer
-- (PHY) Specifications: Specification for Enhanced Security",
-- IEEE 802.11i, July 2004.
--
--[LLMNREnable]
-- Guttman, E., "DHCP LLMNR Enable Option", Internet draft (work
-- in progress), draft-guttman-mdns-enable-02.txt, April 2002.
--
--[LLMNRSec]
-- Jeong, J., Park, J. and H. Kim, "DNS Name Service based on
-- Secure Multicast DNS for IPv6 Mobile Ad Hoc Networks", ICACT
-- 2004, Phoenix Park, Korea, February 9-11, 2004.
--
--[POSIX] IEEE Std. 1003.1-2001 Standard for Information Technology --
-- Portable Operating System Interface (POSIX). Open Group
-- Technical Standard: Base Specifications, Issue 6, December
-- 2001. ISO/IEC 9945:2002. http://www.opengroup.org/austin
--
--[RFC1536] Kumar, A., et. al., "DNS Implementation Errors and Suggested
-- Fixes", RFC 1536, October 1993.
--
--[RFC1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
-- Recommendations for Security", RFC 1750, December 1994.
--
--[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
-- March 1997.
--
--[RFC2292] Stevens, W. and M. Thomas, "Advanced Sockets API for IPv6",
-- RFC 2292, February 1998.
--
--[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC
-- 2365, July 1998.
--
--[RFC2553] Gilligan, R., Thomson, S., Bound, J. and W. Stevens, "Basic
-- Socket Interface Extensions for IPv6", RFC 2553, March 1999.
--
--[RFC2937] Smith, C., "The Name Service Search Option for DHCP", RFC
-- 2937, September 2000.
--
--[RFC3315] Droms, R., et al., "Dynamic Host Configuration Protocol for
-- IPv6 (DHCPv6)", RFC 3315, July 2003.
--
--[RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain Name
-- System (DNS)", RFC 3833, August 2004.
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 27]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--[RFC3927] Cheshire, S., Aboba, B. and E. Guttman, "Dynamic Configuration
-- of Link-Local IPv4 Addresses", RFC 3927, October 2004.
--
--[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D. and S. Rose,
-- "DNS Security Introduction and Requirement", RFC 4033, March
-- 2005.
--
--Acknowledgments
--
-- This work builds upon original work done on multicast DNS by Bill
-- Manning and Bill Woodcock. Bill Manning's work was funded under
-- DARPA grant #F30602-99-1-0523. The authors gratefully acknowledge
-- their contribution to the current specification. Constructive input
-- has also been received from Mark Andrews, Rob Austein, Randy Bush,
-- Stuart Cheshire, Ralph Droms, Robert Elz, James Gilroy, Olafur
-- Gudmundsson, Andreas Gustafsson, Erik Guttman, Myron Hattig,
-- Christian Huitema, Olaf Kolkman, Mika Liljeberg, Keith Moore,
-- Tomohide Nagashima, Thomas Narten, Erik Nordmark, Markku Savela, Mike
-- St. Johns, Sander Van-Valkenburg, and Brian Zill.
--
--Authors' Addresses
--
-- Bernard Aboba
-- Microsoft Corporation
-- One Microsoft Way
-- Redmond, WA 98052
--
-- Phone: +1 425 706 6605
-- EMail: bernarda@microsoft.com
--
-- Dave Thaler
-- Microsoft Corporation
-- One Microsoft Way
-- Redmond, WA 98052
--
-- Phone: +1 425 703 8835
-- EMail: dthaler@microsoft.com
--
-- Levon Esibov
-- Microsoft Corporation
-- One Microsoft Way
-- Redmond, WA 98052
--
-- EMail: levone@microsoft.com
--
--
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 28]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at ietf-
-- ipr@ietf.org.
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
-- except as set forth therein, the authors retain all their rights.
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
--
--
--
--Aboba, Thaler & Esibov Standards Track [Page 29]
--
--
--
--
--
--INTERNET-DRAFT LLMNR 16 April 2006
--
--
--Open Issues
--
-- Open issues with this specification are tracked on the following web
-- site:
--
-- http://www.drizzle.com/~aboba/DNSEXT/llmnrissues.html
--
--
--
--
--
--
--
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--Aboba, Thaler & Esibov Standards Track [Page 30]
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--
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--
--
--
--Network Working Group R. Austein
--Internet-Draft ISC
--Expires: July 15, 2006 January 11, 2006
--
--
-- DNS Name Server Identifier Option (NSID)
-- draft-ietf-dnsext-nsid-01
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on July 15, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- With the increased use of DNS anycast, load balancing, and other
-- mechanisms allowing more than one DNS name server to share a single
-- IP address, it is sometimes difficult to tell which of a pool of name
-- servers has answered a particular query. While existing ad-hoc
-- mechanism allow an operator to send follow-up queries when it is
-- necessary to debug such a configuration, the only completely reliable
-- way to obtain the identity of the name server which responded is to
-- have the name server include this information in the response itself.
-- This note defines a protocol extension to support this functionality.
--
--
--
--Austein Expires July 15, 2006 [Page 1]
--\f
--Internet-Draft DNS NSID January 2006
--
--
--Table of Contents
--
-- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
-- 1.1. Reserved Words . . . . . . . . . . . . . . . . . . . . . . 3
-- 2. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
-- 2.1. Resolver Behavior . . . . . . . . . . . . . . . . . . . . 4
-- 2.2. Name Server Behavior . . . . . . . . . . . . . . . . . . . 4
-- 2.3. The NSID Option . . . . . . . . . . . . . . . . . . . . . 4
-- 2.4. Presentation Format . . . . . . . . . . . . . . . . . . . 5
-- 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 6
-- 3.1. The NSID Payload . . . . . . . . . . . . . . . . . . . . . 6
-- 3.2. NSID Is Not Transitive . . . . . . . . . . . . . . . . . . 8
-- 3.3. User Interface Issues . . . . . . . . . . . . . . . . . . 8
-- 3.4. Truncation . . . . . . . . . . . . . . . . . . . . . . . . 9
-- 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
-- 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
-- 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
-- 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
-- 7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
-- 7.2. Informative References . . . . . . . . . . . . . . . . . . 13
-- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
-- Intellectual Property and Copyright Statements . . . . . . . . . . 15
--
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--
--1. Introduction
--
-- With the increased use of DNS anycast, load balancing, and other
-- mechanisms allowing more than one DNS name server to share a single
-- IP address, it is sometimes difficult to tell which of a pool of name
-- servers has answered a particular query.
--
-- Existing ad-hoc mechanisms allow an operator to send follow-up
-- queries when it is necessary to debug such a configuration, but there
-- are situations in which this is not a totally satisfactory solution,
-- since anycast routing may have changed, or the server pool in
-- question may be behind some kind of extremely dynamic load balancing
-- hardware. Thus, while these ad-hoc mechanisms are certainly better
-- than nothing (and have the advantage of already being deployed), a
-- better solution seems desirable.
--
-- Given that a DNS query is an idempotent operation with no retained
-- state, it would appear that the only completely reliable way to
-- obtain the identity of the name server which responded to a
-- particular query is to have that name server include identifying
-- information in the response itself. This note defines a protocol
-- enhancement to achieve this.
--
--1.1. Reserved Words
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [RFC2119].
--
--
--
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--Austein Expires July 15, 2006 [Page 3]
--\f
--Internet-Draft DNS NSID January 2006
--
--
--2. Protocol
--
-- This note uses an EDNS [RFC2671] option to signal the resolver's
-- desire for information identifying the name server and to hold the
-- name server's response, if any.
--
--2.1. Resolver Behavior
--
-- A resolver signals its desire for information identifying a name
-- server by sending an empty NSID option (Section 2.3) in an EDNS OPT
-- pseudo-RR in the query message.
--
-- The resolver MUST NOT include any NSID payload data in the query
-- message.
--
-- The semantics of an NSID request are not transitive. That is: the
-- presence of an NSID option in a query is a request that the name
-- server which receives the query identify itself. If the name server
-- side of a recursive name server receives an NSID request, the client
-- is asking the recursive name server to identify itself; if the
-- resolver side of the recursive name server wishes to receive
-- identifying information, it is free to add NSID requests in its own
-- queries, but that is a separate matter.
--
--2.2. Name Server Behavior
--
-- A name server which understands the NSID option and chooses to honor
-- a particular NSID request responds by including identifying
-- information in a NSID option (Section 2.3) in an EDNS OPT pseudo-RR
-- in the response message.
--
-- The name server MUST ignore any NSID payload data that might be
-- present in the query message.
--
-- The NSID option is not transitive. A name server MUST NOT send an
-- NSID option back to a resolver which did not request it. In
-- particular, while a recursive name server may choose to add an NSID
-- option when sending a query, this has no effect on the presence or
-- absence of the NSID option in the recursive name server's response to
-- the original client.
--
-- As stated in Section 2.1, this mechanism is not restricted to
-- authoritative name servers; the semantics are intended to be equally
-- applicable to recursive name servers.
--
--2.3. The NSID Option
--
-- The OPTION-CODE for the NSID option is [TBD].
--
--
--
--Austein Expires July 15, 2006 [Page 4]
--\f
--Internet-Draft DNS NSID January 2006
--
--
-- The OPTION-DATA for the NSID option is an opaque byte string the
-- semantics of which are deliberately left outside the protocol. See
-- Section 3.1 for discussion.
--
--2.4. Presentation Format
--
-- User interfaces MUST read and write the content of the NSID option as
-- a sequence of hexadecimal digits, two digits per payload octet.
--
-- The NSID payload is binary data. Any comparison between NSID
-- payloads MUST be a comparison of the raw binary data. Copy
-- operations MUST NOT assume that the raw NSID payload is null-
-- terminated. Any resemblance between raw NSID payload data and any
-- form of text is purely a convenience, and does not change the
-- underlying nature of the payload data.
--
-- See Section 3.3 for discussion.
--
--
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--
--3. Discussion
--
-- This section discusses certain aspects of the protocol and explains
-- considerations that led to the chosen design.
--
--3.1. The NSID Payload
--
-- The syntax and semantics of the content of the NSID option is
-- deliberately left outside the scope of this specification. This
-- section describe some of the kinds of data that server administrators
-- might choose to provide as the content of the NSID option, and
-- explains the reasoning behind choosing a simple opaque byte string.
--
-- There are several possibilities for the payload of the NSID option:
--
-- o It could be the "real" name of the specific name server within the
-- name server pool.
--
-- o It could be the "real" IP address (IPv4 or IPv6) of the name
-- server within the name server pool.
--
-- o It could be some sort of pseudo-random number generated in a
-- predictable fashion somehow using the server's IP address or name
-- as a seed value.
--
-- o It could be some sort of probabilisticly unique identifier
-- initially derived from some sort of random number generator then
-- preserved across reboots of the name server.
--
-- o It could be some sort of dynamicly generated identifier so that
-- only the name server operator could tell whether or not any two
-- queries had been answered by the same server.
--
-- o It could be a blob of signed data, with a corresponding key which
-- might (or might not) be available via DNS lookups.
--
-- o It could be a blob of encrypted data, the key for which could be
-- restricted to parties with a need to know (in the opinion of the
-- server operator).
--
-- o It could be an arbitrary string of octets chosen at the discretion
-- of the name server operator.
--
-- Each of these options has advantages and disadvantages:
--
-- o Using the "real" name is simple, but the name server may not have
-- a "real" name.
--
--
--
--
--Austein Expires July 15, 2006 [Page 6]
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--Internet-Draft DNS NSID January 2006
--
--
-- o Using the "real" address is also simple, and the name server
-- almost certainly does have at least one non-anycast IP address for
-- maintenance operations, but the operator of the name server may
-- not be willing to divulge its non-anycast address.
--
-- o Given that one common reason for using anycast DNS techniques is
-- an attempt to harden a critical name server against denial of
-- service attacks, some name server operators are likely to want an
-- identifier other than the "real" name or "real" address of the
-- name server instance.
--
-- o Using a hash or pseudo-random number can provide a fixed length
-- value that the resolver can use to tell two name servers apart
-- without necessarily being able to tell where either one of them
-- "really" is, but makes debugging more difficult if one happens to
-- be in a friendly open environment. Furthermore, hashing might not
-- add much value, since a hash based on an IPv4 address still only
-- involves a 32-bit search space, and DNS names used for servers
-- that operators might have to debug at 4am tend not to be very
-- random.
--
-- o Probabilisticly unique identifiers have similar properties to
-- hashed identifiers, but (given a sufficiently good random number
-- generator) are immune to the search space issues. However, the
-- strength of this approach is also its weakness: there is no
-- algorithmic transformation by which even the server operator can
-- associate name server instances with identifiers while debugging,
-- which might be annoying. This approach also requires the name
-- server instance to preserve the probabilisticly unique identifier
-- across reboots, but this does not appear to be a serious
-- restriction, since authoritative nameservers almost always have
-- some form of nonvolatile storage in any case, and in the rare case
-- of a name server that does not have any way to store such an
-- identifier, nothing terrible will happen if the name server just
-- generates a new identifier every time it reboots.
--
-- o Using an arbitrary octet string gives name server operators yet
-- another thing to configure, or mis-configure, or forget to
-- configure. Having all the nodes in an anycast name server
-- constellation identify themselves as "My Name Server" would not be
-- particularly useful.
--
-- Given all of the issues listed above, there does not appear to be a
-- single solution that will meet all needs. Section 2.3 therefore
-- defines the NSID payload to be an opaque byte string and leaves the
-- choice up to the implementor and name server operator. The following
-- guidelines may be useful to implementors and server operators:
--
--
--
--
--Austein Expires July 15, 2006 [Page 7]
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--Internet-Draft DNS NSID January 2006
--
--
-- o Operators for whom divulging the unicast address is an issue could
-- use the raw binary representation of a probabilisticly unique
-- random number. This should probably be the default implementation
-- behavior.
--
-- o Operators for whom divulging the unicast address is not an issue
-- could just use the raw binary representation of a unicast address
-- for simplicity. This should only be done via an explicit
-- configuration choice by the operator.
--
-- o Operators who really need or want the ability to set the NSID
-- payload to an arbitrary value could do so, but this should only be
-- done via an explicit configuration choice by the operator.
--
-- This approach appears to provide enough information for useful
-- debugging without unintentionally leaking the maintenance addresses
-- of anycast name servers to nogoodniks, while also allowing name
-- server operators who do not find such leakage threatening to provide
-- more information at their own discretion.
--
--3.2. NSID Is Not Transitive
--
-- As specified in Section 2.1 and Section 2.2, the NSID option is not
-- transitive. This is strictly a hop-by-hop mechanism.
--
-- Most of the discussion of name server identification to date has
-- focused on identifying authoritative name servers, since the best
-- known cases of anycast name servers are a subset of the name servers
-- for the root zone. However, given that anycast DNS techniques are
-- also applicable to recursive name servers, the mechanism may also be
-- useful with recursive name servers. The hop-by-hop semantics support
-- this.
--
-- While there might be some utility in having a transitive variant of
-- this mechanism (so that, for example, a stub resolver could ask a
-- recursive server to tell it which authoritative name server provided
-- a particular answer to the recursive name server), the semantics of
-- such a variant would be more complicated, and are left for future
-- work.
--
--3.3. User Interface Issues
--
-- Given the range of possible payload contents described in
-- Section 3.1, it is not possible to define a single presentation
-- format for the NSID payload that is efficient, convenient,
-- unambiguous, and aesthetically pleasing. In particular, while it is
-- tempting to use a presentation format that uses some form of textual
-- strings, attempting to support this would significantly complicate
--
--
--
--Austein Expires July 15, 2006 [Page 8]
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--Internet-Draft DNS NSID January 2006
--
--
-- what's intended to be a very simple debugging mechanism.
--
-- In some cases the content of the NSID payload may be binary data
-- meaningful only to the name server operator, and may not be
-- meaningful to the user or application, but the user or application
-- must be able to capture the entire content anyway in order for it to
-- be useful. Thus, the presentation format must support arbitrary
-- binary data.
--
-- In cases where the name server operator derives the NSID payload from
-- textual data, a textual form such as US-ASCII or UTF-8 strings might
-- at first glance seem easier for a user to deal with. There are,
-- however, a number of complex issues involving internationalized text
-- which, if fully addressed here, would require a set of rules
-- significantly longer than the rest of this specification. See
-- [RFC2277] for an overview of some of these issues.
--
-- It is much more important for the NSID payload data to be passed
-- unambiguously from server administrator to user and back again than
-- it is for the payload data data to be pretty while in transit. In
-- particular, it's critical that it be straightforward for a user to
-- cut and paste an exact copy of the NSID payload output by a debugging
-- tool into other formats such as email messages or web forms without
-- distortion. Hexadecimal strings, while ugly, are also robust.
--
--3.4. Truncation
--
-- In some cases, adding the NSID option to a response message may
-- trigger message truncation. This specification does not change the
-- rules for DNS message truncation in any way, but implementors will
-- need to pay attention to this issue.
--
-- Including the NSID option in a response is always optional, so this
-- specification never requires name servers to truncate response
-- messages.
--
-- By definition, a resolver that requests NSID responses also supports
-- EDNS, so a resolver that requests NSID responses can also use the
-- "sender's UDP payload size" field of the OPT pseudo-RR to signal a
-- receive buffer size large enough to make truncation unlikely.
--
--
--
--
--
--
--
--
--
--
--
--Austein Expires July 15, 2006 [Page 9]
--\f
--Internet-Draft DNS NSID January 2006
--
--
--4. IANA Considerations
--
-- This mechanism requires allocation of one ENDS option code for the
-- NSID option (Section 2.3).
--
--
--
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--Austein Expires July 15, 2006 [Page 10]
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--Internet-Draft DNS NSID January 2006
--
--
--5. Security Considerations
--
-- This document describes a channel signaling mechanism, intended
-- primarily for debugging. Channel signaling mechanisms are outside
-- the scope of DNSSEC per se. Applications that require integrity
-- protection for the data being signaled will need to use a channel
-- security mechanism such as TSIG [RFC2845].
--
-- Section 3.1 discusses a number of different kinds of information that
-- a name server operator might choose to provide as the value of the
-- NSID option. Some of these kinds of information are security
-- sensitive in some environments. This specification deliberately
-- leaves the syntax and semantics of the NSID option content up to the
-- implementation and the name server operator.
--
--
--
--
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--Austein Expires July 15, 2006 [Page 11]
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--Internet-Draft DNS NSID January 2006
--
--
--6. Acknowledgements
--
-- Joe Abley, Harald Alvestrand, Mark Andrews, Roy Arends, Steve
-- Bellovin, Randy Bush, David Conrad, Johan Ihren, Daniel Karrenberg,
-- Peter Koch, Mike Patton, Mike StJohns, Paul Vixie, Sam Weiler, and
-- Suzanne Woolf. Apologies to anyone inadvertently omitted from the
-- above list.
--
--
--
--
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--Austein Expires July 15, 2006 [Page 12]
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--Internet-Draft DNS NSID January 2006
--
--
--7. References
--
--7.1. Normative References
--
-- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", RFC 2119, BCP 14, March 1997.
--
-- [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
-- RFC 2671, August 1999.
--
-- [RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
-- Wellington, "Secret Key Transaction Authentication for DNS
-- (TSIG)", RFC 2845, May 2000.
--
--7.2. Informative References
--
-- [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
-- Languages", RFC 2277, BCP 18, January 1998.
--
--
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--Austein Expires July 15, 2006 [Page 13]
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--Internet-Draft DNS NSID January 2006
--
--
--Author's Address
--
-- Rob Austein
-- ISC
-- 950 Charter Street
-- Redwood City, CA 94063
-- USA
--
-- Email: sra@isc.org
--
--
--
--
--
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--Austein Expires July 15, 2006 [Page 14]
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--
--
--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--
--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
-- except as set forth therein, the authors retain all their rights.
--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
--Austein Expires July 15, 2006 [Page 15]
--\f
+++ /dev/null
--
--INTERNET-DRAFT DSA Information in the DNS
--OBSOLETES: RFC 2536 Donald E. Eastlake 3rd
-- Motorola Laboratories
--Expires: September 2006 March 2006
--
--
-- DSA Keying and Signature Information in the DNS
-- --- ------ --- --------- ----------- -- --- ---
-- <draft-ietf-dnsext-rfc2536bis-dsa-07.txt>
-- Donald E. Eastlake 3rd
--
--
--Status of This Document
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Distribution of this document is unlimited. Comments should be sent
-- to the DNS extensions working group mailing list
-- <namedroppers@ops.ietf.org>.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/1id-abstracts.html
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html
--
--
--
--Abstract
--
-- The standard method of encoding US Government Digital Signature
-- Algorithm keying and signature information for use in the Domain Name
-- System is specified.
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 1]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
--Table of Contents
--
-- Status of This Document....................................1
-- Abstract...................................................1
--
-- Table of Contents..........................................2
--
-- 1. Introduction............................................3
-- 2. DSA Keying Information..................................3
-- 3. DSA Signature Information...............................4
-- 4. Performance Considerations..............................4
-- 5. Security Considerations.................................5
-- 6. IANA Considerations.....................................5
-- Copyright, Disclaimer, and Additional IPR Provisions.......5
--
-- Normative References.......................................7
-- Informative References.....................................7
--
-- Author's Address...........................................8
-- Expiration and File Name...................................8
--
--
--
--
--
--
--
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--
--D. Eastlake 3rd [Page 2]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
--1. Introduction
--
-- The Domain Name System (DNS) is the global hierarchical replicated
-- distributed database system for Internet addressing, mail proxy, and
-- other information [RFC 1034, 1035]. The DNS has been extended to
-- include digital signatures and cryptographic keys as described in
-- [RFC 4033, 4034, 4035] and additional work is underway which would
-- require the storage of keying and signature information in the DNS.
--
-- This document describes how to encode US Government Digital Signature
-- Algorithm (DSA) keys and signatures in the DNS. Familiarity with the
-- US Digital Signature Algorithm is assumed [FIPS 186-2, Schneier].
--
--
--
--2. DSA Keying Information
--
-- When DSA public keys are stored in the DNS, the structure of the
-- relevant part of the RDATA part of the RR being used is the fields
-- listed below in the order given.
--
-- The period of key validity is not included in this data but is
-- indicated separately, for example by an RR such as RRSIG which signs
-- and authenticates the RR containing the keying information.
--
-- Field Size
-- ----- ----
-- T 1 octet
-- Q 20 octets
-- P 64 + T*8 octets
-- G 64 + T*8 octets
-- Y 64 + T*8 octets
--
-- As described in [FIPS 186-2] and [Schneier], T is a key size
-- parameter chosen such that 0 <= T <= 8. (The meaning if the T octet
-- is greater than 8 is reserved and the remainder of the data may have
-- a different format in that case.) Q is a prime number selected at
-- key generation time such that 2**159 < Q < 2**160. Thus Q is always
-- 20 octets long and, as with all other fields, is stored in "big-
-- endian" network order. P, G, and Y are calculated as directed by the
-- [FIPS 186-2] key generation algorithm [Schneier]. P is in the range
-- 2**(511+64T) < P < 2**(512+64T) and thus is 64 + 8*T octets long. G
-- and Y are quantities modulo P and so can be up to the same length as
-- P and are allocated fixed size fields with the same number of octets
-- as P.
--
-- During the key generation process, a random number X must be
-- generated such that 1 <= X <= Q-1. X is the private key and is used
-- in the final step of public key generation where Y is computed as
--
--
--
--D. Eastlake 3rd [Page 3]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
-- Y = G**X mod P
--
--
--
--3. DSA Signature Information
--
-- The portion of the RDATA area used for US Digital Signature Algorithm
-- signature information is shown below with fields in the order they
-- are listed and the contents of each multi-octet field in "big-endian"
-- network order.
--
-- Field Size
-- ----- ----
-- T 1 octet
-- R 20 octets
-- S 20 octets
--
-- First, the data signed must be determined. Then the following steps
-- are taken, as specified in [FIPS 186-2], where Q, P, G, and Y are as
-- specified in the public key [Schneier]:
--
-- hash = SHA-1 ( data )
--
-- Generate a random K such that 0 < K < Q.
--
-- R = ( G**K mod P ) mod Q
--
-- S = ( K**(-1) * (hash + X*R) ) mod Q
--
-- For information on the SHA-1 hash function see [FIPS 180-2] and [RFC
-- 3174].
--
-- Since Q is 160 bits long, R and S can not be larger than 20 octets,
-- which is the space allocated.
--
-- T is copied from the public key. It is not logically necessary in
-- the SIG but is present so that values of T > 8 can more conveniently
-- be used as an escape for extended versions of DSA or other algorithms
-- as later standardized.
--
--
--
--4. Performance Considerations
--
-- General signature generation speeds are roughly the same for RSA [RFC
-- 3110] and DSA. With sufficient pre-computation, signature generation
-- with DSA is faster than RSA. Key generation is also faster for DSA.
-- However, signature verification is an order of magnitude slower than
-- RSA when the RSA public exponent is chosen to be small, as is
-- recommended for some applications.
--
--
--D. Eastlake 3rd [Page 4]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
-- Current DNS implementations are optimized for small transfers,
-- typically less than 512 bytes including DNS overhead. Larger
-- transfers will perform correctly and extensions have been
-- standardized [RFC 2671] to make larger transfers more efficient, it
-- is still advisable at this time to make reasonable efforts to
-- minimize the size of RR sets containing keying and/or signature
-- inforamtion consistent with adequate security.
--
--
--
--5. Security Considerations
--
-- Keys retrieved from the DNS should not be trusted unless (1) they
-- have been securely obtained from a secure resolver or independently
-- verified by the user and (2) this secure resolver and secure
-- obtainment or independent verification conform to security policies
-- acceptable to the user. As with all cryptographic algorithms,
-- evaluating the necessary strength of the key is essential and
-- dependent on local policy.
--
-- The key size limitation of a maximum of 1024 bits ( T = 8 ) in the
-- current DSA standard may limit the security of DSA. For particular
-- applications, implementors are encouraged to consider the range of
-- available algorithms and key sizes.
--
-- DSA assumes the ability to frequently generate high quality random
-- numbers. See [random] for guidance. DSA is designed so that if
-- biased rather than random numbers are used, high bandwidth covert
-- channels are possible. See [Schneier] and more recent research. The
-- leakage of an entire DSA private key in only two DSA signatures has
-- been demonstrated. DSA provides security only if trusted
-- implementations, including trusted random number generation, are
-- used.
--
--
--
--6. IANA Considerations
--
-- Allocation of meaning to values of the T parameter that are not
-- defined herein (i.e., > 8 ) requires an IETF standards actions. It
-- is intended that values unallocated herein be used to cover future
-- extensions of the DSS standard.
--
--
--
--Copyright, Disclaimer, and Additional IPR Provisions
--
-- Copyright (C) The Internet Society (2006). This document is subject to
-- the rights, licenses and restrictions contained in BCP 78, and except
-- as set forth therein, the authors retain all their rights.
--
--
--D. Eastlake 3rd [Page 5]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at ietf-
-- ipr@ietf.org.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 6]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
--Normative References
--
-- [FIPS 186-2] - U.S. Federal Information Processing Standard: Digital
-- Signature Standard, 27 January 2000.
--
-- [RFC 4034] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
--
--
--Informative References
--
-- [RFC 1034] - "Domain names - concepts and facilities", P.
-- Mockapetris, 11/01/1987.
--
-- [RFC 1035] - "Domain names - implementation and specification", P.
-- Mockapetris, 11/01/1987.
--
-- [RFC 2671] - "Extension Mechanisms for DNS (EDNS0)", P. Vixie, August
-- 1999.
--
-- [RFC 3110] - "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System
-- (DNS)", D. Eastlake 3rd. May 2001.
--
-- [RFC 3174] - "US Secure Hash Algorithm 1 (SHA1)", D. Eastlake, P.
-- Jones, September 2001.
--
-- [RFC 4033] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "DNS Security Introduction and Requirements", RFC 4033, March
-- 2005.
--
-- [RFC 4035] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Protocol Modifications for the DNS Security Extensions", RFC
-- 4035, March 2005.
--
-- [RFC 4086] - Eastlake, D., 3rd, Schiller, J., and S. Crocker,
-- "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.
--
-- [Schneier] - "Applied Cryptography Second Edition: protocols,
-- algorithms, and source code in C" (second edition), Bruce Schneier,
-- 1996, John Wiley and Sons, ISBN 0-471-11709-9.
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 7]
--\f
--
--INTERNET-DRAFT DSA Information in the DNS
--
--
--Author's Address
--
-- Donald E. Eastlake 3rd
-- Motorola Labortories
-- 155 Beaver Street
-- Milford, MA 01757 USA
--
-- Telephone: +1-508-786-7554(w)
-- EMail: Donald.Eastlake@motorola.com
--
--
--
--Expiration and File Name
--
-- This draft expires in September 2006.
--
-- Its file name is draft-ietf-dnsext-rfc2536bis-dsa-07.txt.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
--D. Eastlake 3rd [Page 8]
--\f
+++ /dev/null
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--OBSOLETES: RFC 2539 Donald E. Eastlake 3rd
-- Motorola Laboratories
--Expires: September 2006 March 2006
--
--
--
--
-- Storage of Diffie-Hellman Keying Information in the DNS
-- ------- -- -------------- ------ ----------- -- --- ---
-- <draft-ietf-dnsext-rfc2539bis-dhk-07.txt>
--
--
--
--Status of This Document
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Distribution of this document is unlimited. Comments should be sent
-- to the DNS extensions working group mailing list
-- <namedroppers@ops.ietf.org>.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/1id-abstracts.html
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html
--
--
--Abstract
--
-- The standard method for encoding Diffie-Hellman keys in the Domain
-- Name System is specified.
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 1]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--Acknowledgements
--
-- Part of the format for Diffie-Hellman keys and the description
-- thereof was taken from a work in progress by Ashar Aziz, Tom Markson,
-- and Hemma Prafullchandra. In addition, the following persons
-- provided useful comments that were incorporated into the predecessor
-- of this document: Ran Atkinson, Thomas Narten.
--
--
--
--Table of Contents
--
-- Status of This Document....................................1
-- Abstract...................................................1
--
-- Acknowledgements...........................................2
-- Table of Contents..........................................2
--
-- 1. Introduction............................................3
-- 1.1 About This Document....................................3
-- 1.2 About Diffie-Hellman...................................3
-- 2. Encoding Diffie-Hellman Keying Information..............4
-- 3. Performance Considerations..............................5
-- 4. IANA Considerations.....................................5
-- 5. Security Considerations.................................5
-- Copyright, Disclaimer, and Additional IPR Provisions.......5
--
-- Normative References.......................................7
-- Informative Refences.......................................7
--
-- Author's Address...........................................8
-- Expiration and File Name...................................8
--
-- Appendix A: Well known prime/generator pairs...............9
-- A.1. Well-Known Group 1: A 768 bit prime..................9
-- A.2. Well-Known Group 2: A 1024 bit prime.................9
-- A.3. Well-Known Group 3: A 1536 bit prime................10
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 2]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--1. Introduction
--
-- The Domain Name System (DNS) is the global hierarchical replicated
-- distributed database system for Internet addressing, mail proxy, and
-- similar information [RFC 1034, 1035]. The DNS has been extended to
-- include digital signatures and cryptographic keys as described in
-- [RFC 4033, 4034, 4035] and additonal work is underway which would use
-- the storage of keying information in the DNS.
--
--
--
--1.1 About This Document
--
-- This document describes how to store Diffie-Hellman keys in the DNS.
-- Familiarity with the Diffie-Hellman key exchange algorithm is assumed
-- [Schneier, RFC 2631].
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119.
--
--
--
--1.2 About Diffie-Hellman
--
-- Diffie-Hellman requires two parties to interact to derive keying
-- information which can then be used for authentication. Thus Diffie-
-- Hellman is inherently a key agreement algorithm. As a result, no
-- format is defined for Diffie-Hellman "signature information". For
-- example, assume that two parties have local secrets "i" and "j".
-- Assume they each respectively calculate X and Y as follows:
--
-- X = g**i ( mod p )
--
-- Y = g**j ( mod p )
--
-- They exchange these quantities and then each calculates a Z as
-- follows:
--
-- Zi = Y**i ( mod p )
--
-- Zj = X**j ( mod p )
--
-- Zi and Zj will both be equal to g**(i*j)(mod p) and will be a shared
-- secret between the two parties that an adversary who does not know i
-- or j will not be able to learn from the exchanged messages (unless
-- the adversary can derive i or j by performing a discrete logarithm
-- mod p which is hard for strong p and g).
--
-- The private key for each party is their secret i (or j). The public
--
--
--D. Eastlake 3rd [Page 3]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
-- key is the pair p and g, which is the same for both parties, and
-- their individual X (or Y).
--
-- For further information about Diffie-Hellman and precautions to take
-- in deciding on a p and g, see [RFC 2631].
--
--
--
--2. Encoding Diffie-Hellman Keying Information
--
-- When Diffie-Hellman keys appear within the RDATA portion of a RR,
-- they are encoded as shown below.
--
-- The period of key validity is not included in this data but is
-- indicated separately, for example by an RR such as RRSIG which signs
-- and authenticates the RR containing the keying information.
--
-- 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
-- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | KEY flags | protocol | algorithm=2 |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | prime length (or flag) | prime (p) (or special) /
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- / prime (p) (variable length) | generator length |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | generator (g) (variable length) |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | public value length | public value (variable length)/
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- / public value (g^i mod p) (variable length) |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
--
-- Prime length is the length of the Diffie-Hellman prime (p) in bytes
-- if it is 16 or greater. Prime contains the binary representation of
-- the Diffie-Hellman prime with most significant byte first (i.e., in
-- network order). If "prime length" field is 1 or 2, then the "prime"
-- field is actually an unsigned index into a table of 65,536
-- prime/generator pairs and the generator length SHOULD be zero. See
-- Appedix A for defined table entries and Section 4 for information on
-- allocating additional table entries. The meaning of a zero or 3
-- through 15 value for "prime length" is reserved.
--
-- Generator length is the length of the generator (g) in bytes.
-- Generator is the binary representation of generator with most
-- significant byte first. PublicValueLen is the Length of the Public
-- Value (g**i (mod p)) in bytes. PublicValue is the binary
-- representation of the DH public value with most significant byte
-- first.
--
--
--
--D. Eastlake 3rd [Page 4]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--3. Performance Considerations
--
-- Current DNS implementations are optimized for small transfers,
-- typically less than 512 bytes including DNS overhead. Larger
-- transfers will perform correctly and extensions have been
-- standardized [RFC 2671] to make larger transfers more efficient. But
-- it is still advisable at this time to make reasonable efforts to
-- minimize the size of RR sets containing keying information consistent
-- with adequate security.
--
--
--
--4. IANA Considerations
--
-- Assignment of meaning to Prime Lengths of 0 and 3 through 15 requires
-- an IETF consensus as defined in [RFC 2434].
--
-- Well known prime/generator pairs number 0x0000 through 0x07FF can
-- only be assigned by an IETF standards action. [RFC 2539], the
-- Proposed Standard predecessor of this document, assigned 0x0001
-- through 0x0002. This document additionally assigns 0x0003. Pairs
-- number 0s0800 through 0xBFFF can be assigned based on RFC
-- documentation. Pairs number 0xC000 through 0xFFFF are available for
-- private use and are not centrally coordinated. Use of such private
-- pairs outside of a closed environment may result in conflicts and/or
-- security failures.
--
--
--
--5. Security Considerations
--
-- Keying information retrieved from the DNS should not be trusted
-- unless (1) it has been securely obtained from a secure resolver or
-- independently verified by the user and (2) this secure resolver and
-- secure obtainment or independent verification conform to security
-- policies acceptable to the user. As with all cryptographic
-- algorithms, evaluating the necessary strength of the key is important
-- and dependent on security policy.
--
-- In addition, the usual Diffie-Hellman key strength considerations
-- apply. (p-1)/2 SHOULD also be prime, g SHOULD be primitive mod p, p
-- SHOULD be "large", etc. See [RFC 2631, Schneier].
--
--
--
--Copyright, Disclaimer, and Additional IPR Provisions
--
-- Copyright (C) The Internet Society (2006). This document is subject to
-- the rights, licenses and restrictions contained in BCP 78, and except
-- as set forth therein, the authors retain all their rights.
--
--
--D. Eastlake 3rd [Page 5]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at ietf-
-- ipr@ietf.org.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 6]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--Normative References
--
-- [RFC 2119] - Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
-- [RFC 2434] - "Guidelines for Writing an IANA Considerations Section
-- in RFCs", T. Narten, H. Alvestrand, October 1998.
--
-- [RFC 2631] - "Diffie-Hellman Key Agreement Method", E. Rescorla, June
-- 1999.
--
-- [RFC 4034] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
--
--
--Informative Refences
--
-- [RFC 1034] - "Domain names - concepts and facilities", P.
-- Mockapetris, November 1987.
--
-- [RFC 1035] - "Domain names - implementation and specification", P.
-- Mockapetris, November 1987.
--
-- [RFC 2539] - "Storage of Diffie-Hellman Keys in the Domain Name
-- System (DNS)", D. Eastlake, March 1999, obsoleted by this RFC.
--
-- [RFC 2671] - "Extension Mechanisms for DNS (EDNS0)", P. Vixie, August
-- 1999.
--
-- [RFC 4033] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "DNS Security Introduction and Requirements", RFC 4033, March
-- 2005.
--
-- [RFC 4035] - Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Protocol Modifications for the DNS Security Extensions", RFC
-- 4035, March 2005.
--
-- [Schneier] - Bruce Schneier, "Applied Cryptography: Protocols,
-- Algorithms, and Source Code in C" (Second Edition), 1996, John Wiley
-- and Sons.
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 7]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--Author's Address
--
-- Donald E. Eastlake 3rd
-- Motorola Laboratories
-- 155 Beaver Street
-- Milford, MA 01757 USA
--
-- Telephone: +1-508-786-7554
-- EMail: Donald.Eastlake@motorola.com
--
--
--
--Expiration and File Name
--
-- This draft expires in September 2006.
--
-- Its file name is draft-ietf-dnsext-rfc2539bis-dhk-07.txt.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 8]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--Appendix A: Well known prime/generator pairs
--
-- These numbers are copied from the IPSEC effort where the derivation
-- of these values is more fully explained and additional information is
-- available. Richard Schroeppel performed all the mathematical and
-- computational work for this appendix.
--
--
--
--A.1. Well-Known Group 1: A 768 bit prime
--
-- The prime is 2^768 - 2^704 - 1 + 2^64 * { [2^638 pi] + 149686 }. Its
-- decimal value is
-- 155251809230070893513091813125848175563133404943451431320235
-- 119490296623994910210725866945387659164244291000768028886422
-- 915080371891804634263272761303128298374438082089019628850917
-- 0691316593175367469551763119843371637221007210577919
--
-- Prime modulus: Length (32 bit words): 24, Data (hex):
-- FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
-- 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
-- EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
-- E485B576 625E7EC6 F44C42E9 A63A3620 FFFFFFFF FFFFFFFF
--
-- Generator: Length (32 bit words): 1, Data (hex): 2
--
--
--
--A.2. Well-Known Group 2: A 1024 bit prime
--
-- The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
-- Its decimal value is
-- 179769313486231590770839156793787453197860296048756011706444
-- 423684197180216158519368947833795864925541502180565485980503
-- 646440548199239100050792877003355816639229553136239076508735
-- 759914822574862575007425302077447712589550957937778424442426
-- 617334727629299387668709205606050270810842907692932019128194
-- 467627007
--
-- Prime modulus: Length (32 bit words): 32, Data (hex):
-- FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
-- 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
-- EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
-- E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
-- EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
-- FFFFFFFF FFFFFFFF
--
-- Generator: Length (32 bit words): 1, Data (hex): 2
--
--
--
--
--D. Eastlake 3rd [Page 9]
--\f
--
--INTERNET-DRAFT Diffie-Hellman Information in the DNS
--
--
--A.3. Well-Known Group 3: A 1536 bit prime
--
-- The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }.
-- Its decimal value is
-- 241031242692103258855207602219756607485695054850245994265411
-- 694195810883168261222889009385826134161467322714147790401219
-- 650364895705058263194273070680500922306273474534107340669624
-- 601458936165977404102716924945320037872943417032584377865919
-- 814376319377685986952408894019557734611984354530154704374720
-- 774996976375008430892633929555996888245787241299381012913029
-- 459299994792636526405928464720973038494721168143446471443848
-- 8520940127459844288859336526896320919633919
--
-- Prime modulus Length (32 bit words): 48, Data (hex):
-- FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
-- 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
-- EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
-- E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
-- EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D
-- C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F
-- 83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D
-- 670C354E 4ABC9804 F1746C08 CA237327 FFFFFFFF FFFFFFFF
--
-- Generator: Length (32 bit words): 1, Data (hex): 2
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--D. Eastlake 3rd [Page 10]
--\f
+++ /dev/null
--Internet-Draft dnsext-wcard January 9, 2006
--
--DNSEXT Working Group E. Lewis
--INTERNET DRAFT NeuStar
--Expiration Date: July 9, 2006 January 9, 2006
--Updates RFC 1034, RFC 2672
--
-- The Role of Wildcards
-- in the Domain Name System
-- draft-ietf-dnsext-wcard-clarify-10.txt
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that
-- any applicable patent or other IPR claims of which he or she is
-- aware have been or will be disclosed, and any of which he or she
-- becomes aware will be disclosed, in accordance with Section 6 of
-- BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six
-- months and may be updated, replaced, or obsoleted by other
-- documents at any time. It is inappropriate to use Internet-Drafts
-- as reference material or to cite them other than as "work in
-- progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html
--
-- This Internet-Draft will expire on July 9, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This is an update to the wildcard definition of RFC 1034. The
-- interaction with wildcards and CNAME is changed, an error
-- condition removed, and the words defining some concepts central
-- to wildcards are changed. The overall goal is not to change
-- wildcards, but to refine the definition of RFC 1034.
--
--
--
--
--DNSEXT Working Group Expires July 9, 2006 [Page 1]
--\f
--Internet-Draft dnsext-wcard January 9, 2006
--
--Table of Contents
--
--1. Introduction . . . . . . . . . . . . . . . . 3
--1 1 Motivation 3
--1 2 The Original Definition 3
--1 3 Roadmap to This Document 4
--1 3 1 New Terms 4
--1.3.2 Changed Text 5
--1.3.3 Considerations with Special Types 5
--1.4 Standards Terminology 5
--2. Wildcard Syntax . . . . . . . . . . . . . . . 6
--2.1 Identifying a Wildcard 6
--2.1.1 Wild Card Domain Name and Asterisk Label 6
--2.1.2 Asterisks and Other Characters 6
--2.1.3 Non-terminal Wild Card Domain Names 6
--2.2 Existence Rules 7
--2.2.1 An Example 7
--2.2.2 Empty Non-terminals 9
--2.2.3 Yet Another Definition of Existence 10
--2.3 When is a Wild Card Domain Name Not Special 10
--3. Impact of a Wild Card Domain Name On a Response . . . . . 10
--3.1 Step 2 10
--3.2 Step 3 11
--3.3 Part 'c' 11
--3.3.1 Closest Encloser and the Source of Synthesis 12
--3.3.2 Closest Encloser and Source of Synthesis Examples 12
--3.3.3 Type Matching 13
--4. Considerations with Special Types . . . . . . . . . 13
--4.1 SOA RRSet at a Wild Card Domain Name 13
--4.2 NS RRSet at a Wild Card Domain Name 14
--4.2.1 Discarded Notions 14
--4.3 CNAME RRSet at a Wild Card Domain Name 15
--4.4 DNAME RRSet at a Wild Card Domain Name 15
--4.5 SRV RRSet at a Wild Card Domain Name 16
--4.6 DS RRSet at a Wild Card Domain Name 16
--4.7 NSEC RRSet at a Wild Card Domain Name 17
--4.8 RRSIG at a Wild Card Domain Name 17
--4.9 Empty Non-terminal Wild Card Domain Name 17
--5. Security Considerations . . . . . . . . . . . . . 17
--6. IANA Considerations . . . . . . . . . . . . . 17
--7. References . . . . . . . . . . . . . 17
--8. Editor . . . . . . . . . . . . . 18
--9. Others Contributing to the Document . . . . . . . . 18
--10. Trailing Boilerplate . . . . . . . . . . . . . 19
--
--
--
--
--
--
--
--
--DNSEXT Working Group Expires July 9, 2006 [Page 2]
--\f
--Internet-Draft dnsext-wcard January 9, 2006
--
--1. Introduction
--
-- In RFC 1034 [RFC1034], sections 4.3.2 and 4.3.3 describe the
-- synthesis of answers from special resource records called
-- wildcards. The definition in RFC 1034 is incomplete and has
-- proven to be confusing. This document describes the wildcard
-- synthesis by adding to the discussion and making limited
-- modifications. Modifications are made to close inconsistencies
-- that have led to interoperability issues. This description
-- does not expand the service intended by the original definition.
--
-- Staying within the spirit and style of the original documents,
-- this document avoids specifying rules for DNS implementations
-- regarding wildcards. The intention is to only describe what is
-- needed for interoperability, not restrict implementation choices.
-- In addition, consideration is given to minimize any backwards
-- compatibility issues with implementations that comply with RFC
-- 1034's definition.
--
-- This document is focused on the concept of wildcards as defined
-- in RFC 1034. Nothing is implied regarding alternative means of
-- synthesizing resource record sets, nor are alternatives discussed.
--
--1.1 Motivation
--
-- Many DNS implementations diverge, in different ways, from the
-- original definition of wildcards. Although there is clearly a
-- need to clarify the original documents in light of this alone,
-- the impetus for this document lay in the engineering of the DNS
-- security extensions [RFC4033]. With an unclear definition of
-- wildcards the design of authenticated denial became entangled.
--
-- This document is intended to limit its changes, documenting only
-- those based on implementation experience, and to remain as close
-- to the original document as possible. To reinforce that this
-- document is meant to clarify and adjust and not redefine wildcards,
-- relevant sections of RFC 1034 are repeated verbatim to facilitate
-- comparison of the old and new text.
--
--1.2 The Original Definition
--
-- The definition of the wildcard concept is comprised by the
-- documentation of the algorithm by which a name server prepares
-- a response (in RFC 1034's section 4.3.2) and the way in which
-- a resource record (set) is identified as being a source of
-- synthetic data (section 4.3.3).
--
-- This is the definition of the term "wildcard" as it appears in
-- RFC 1034, section 4.3.3.
--
--
--
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--
--# In the previous algorithm, special treatment was given to RRs with
--# owner names starting with the label "*". Such RRs are called
--# wildcards. Wildcard RRs can be thought of as instructions for
--# synthesizing RRs. When the appropriate conditions are met, the name
--# server creates RRs with an owner name equal to the query name and
--# contents taken from the wildcard RRs.
--
-- This passage follows the algorithm in which the term wildcard
-- is first used. In this definition, wildcard refers to resource
-- records. In other usage, wildcard has referred to domain names,
-- and it has been used to describe the operational practice of
-- relying on wildcards to generate answers. It is clear from this
-- that there is a need to define clear and unambiguous terminology
-- in the process of discussing wildcards.
--
-- The mention of the use of wildcards in the preparation of a
-- response is contained in step 3c of RFC 1034's section 4.3.2
-- entitled "Algorithm." Note that "wildcard" does not appear in
-- the algorithm, instead references are made to the "*" label.
-- The portion of the algorithm relating to wildcards is
-- deconstructed in detail in section 3 of this document, this is
-- the beginning of the relevant portion of the "Algorithm."
--
--# c. If at some label, a match is impossible (i.e., the
--# corresponding label does not exist), look to see if [...]
--# the "*" label exists.
--
-- The scope of this document is the RFC 1034 definition of
-- wildcards and the implications of updates to those documents,
-- such as DNSSEC. Alternate schemes for synthesizing answers are
-- not considered. (Note that there is no reference listed. No
-- document is known to describe any alternate schemes, although
-- there has been some mention of them in mailing lists.)
--
--1.3 Roadmap to This Document
--
-- This document accomplishes these three items.
-- o Defines new terms
-- o Makes minor changes to avoid conflicting concepts
-- o Describes the actions of certain resource records as wildcards
--
--1.3.1 New Terms
--
-- To help in discussing what resource records are wildcards, two
-- terms will be defined - "asterisk label" and "wild card domain
-- name". These are defined in section 2.1.1.
--
-- To assist in clarifying the role of wildcards in the name server
-- algorithm in RFC 1034, 4.3.2, "source of synthesis" and "closest
-- encloser" are defined. These definitions are in section 3.3.2.
-- "Label match" is defined in section 3.2.
--
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--
-- The new terms are used to make discussions of wildcards clearer.
-- Terminology doesn't directly have an impact on implementations.
--
--1.3.2 Changed Text
--
-- The definition of "existence" is changed superficially. This
-- change will not be apparent to implementations; it is needed to
-- make descriptions more precise. The change appears in section
-- 2.2.3.
--
-- RFC 1034, section 4.3.3., seems to prohibit having two asterisk
-- labels in a wildcard owner name. With this document the
-- restriction is removed entirely. This change and its implications
-- are in section 2.1.3.
--
-- The actions when a source of synthesis owns a CNAME RR are
-- changed to mirror the actions if an exact match name owns a
-- CNAME RR. This is an addition to the words in RFC 1034,
-- section 4.3.2, step 3, part c. The discussion of this is in
-- section 3.3.3.
--
-- Only the latter change represents an impact to implementations.
-- The definition of existence is not a protocol impact. The change
-- to the restriction on names is unlikely to have an impact, as
-- RFC 1034 contained no specification on when and how to enforce the
-- restriction.
--
--1.3.3 Considerations with Special Types
--
-- This document describes semantics of wildcard RRSets for
-- "interesting" types as well as empty non-terminal wildcards.
-- Understanding these situations in the context of wildcards has
-- been clouded because these types incur special processing if
-- they are the result of an exact match. This discussion is in
-- section 4.
--
-- These discussions do not have an implementation impact, they cover
-- existing knowledge of the types, but to a greater level of detail.
--
--1.4 Standards Terminology
--
-- This document does not use terms as defined in "Key words for use
-- in RFCs to Indicate Requirement Levels." [RFC2119]
--
-- Quotations of RFC 1034 are denoted by a '#' in the leftmost
-- column. References to section "4.3.2" are assumed to refer
-- to RFC 1034's section 4.3.2, simply titled "Algorithm."
--
--
--
--
--
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--
--2. Wildcard Syntax
--
-- The syntax of a wildcard is the same as any other DNS resource
-- record, across all classes and types. The only significant
-- feature is the owner name.
--
-- Because wildcards are encoded as resource records with special
-- names, they are included in zone transfers and incremental zone
-- transfers[RFC1995] just as non-wildcard resource records are.
-- This feature has been under appreciated until discussions on
-- alternative approaches to wildcards appeared on mailing lists.
--
--2.1 Identifying a Wildcard
--
-- To provide a more accurate description of wildcards, the
-- definition has to start with a discussion of the domain names
-- that appear as owners. Two new terms are needed, "Asterisk
-- Label" and "Wild Card Domain Name."
--
--2.1.1 Wild Card Domain Name and Asterisk Label
--
-- A "wild card domain name" is defined by having its initial
-- (i.e., left-most or least significant) label be, in binary format:
--
-- 0000 0001 0010 1010 (binary) = 0x01 0x2a (hexadecimal)
--
-- The first octet is the normal label type and length for a 1 octet
-- long label, the second octet is the ASCII representation [RFC20]
-- for the '*' character.
--
-- A descriptive name of a label equaling that value is an "asterisk
-- label."
--
-- RFC 1034's definition of wildcard would be "a resource record
-- owned by a wild card domain name."
--
--2.1.2 Asterisks and Other Characters
--
-- No label values other than that in section 2.1.1 are asterisk
-- labels, hence names beginning with other labels are never wild
-- card domain names. Labels such as 'the*' and '**' are not
-- asterisk labels so these labels do not start wild card domain
-- names.
--
--2.1.3 Non-terminal Wild Card Domain Names
--
-- In section 4.3.3, the following is stated:
--
--# .......................... The owner name of the wildcard RRs is of
--# the form "*.<anydomain>", where <anydomain> is any domain name.
--# <anydomain> should not contain other * labels......................
--
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--
-- The restriction is now removed. The original documentation of it
-- is incomplete and the restriction does not serve any purpose
-- given years of operational experience.
--
-- There are three possible reasons for putting the restriction in
-- place, but none of the three has held up over time. One is
-- that the restriction meant that there would never be subdomains
-- of wild card domain names, but the restriciton as stated still
-- permits "example.*.example." for instance. Another is that
-- wild card domain names are not intended to be empty non-terminals,
-- but this situation does not disrupt the algorithm in 4.3.2.
-- Finally, "nested" wild card domain names are not ambiguous once
-- the concept of the closest encloser had been documented.
--
-- A wild card domain name can have subdomains. There is no need
-- to inspect the subdomains to see if there is another asterisk
-- label in any subdomain.
--
-- A wild card domain name can be an empty non-terminal. (See the
-- upcoming sections on empty non-terminals.) In this case, any
-- lookup encountering it will terminate as would any empty
-- non-terminal match.
--
--2.2 Existence Rules
--
-- The notion that a domain name 'exists' is mentioned in the
-- definition of wildcards. In section 4.3.3 of RFC 1034:
--
--# Wildcard RRs do not apply:
--#
--...
--# - When the query name or a name between the wildcard domain and
--# the query name is know[n] to exist. For example, if a wildcard
--
-- "Existence" is therefore an important concept in the understanding
-- of wildcards. Unfortunately, the definition of what exists, in RFC
-- 1034, is unclear. So, in sections 2.2.2. and 2.2.3, another look is
-- taken at the definition of existence.
--
--2.2.1 An Example
--
-- To illustrate what is meant by existence consider this complete
-- zone:
--
--
--
--
--
--
--
--
--
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--
-- $ORIGIN example.
-- example. 3600 IN SOA <SOA RDATA>
-- example. 3600 NS ns.example.com.
-- example. 3600 NS ns.example.net.
-- *.example. 3600 TXT "this is a wild card"
-- *.example. 3600 MX 10 host1.example.
-- sub.*.example. 3600 TXT "this is not a wild card"
-- host1.example. 3600 A 192.0.4.1
-- _ssh._tcp.host1.example. 3600 SRV <SRV RDATA>
-- _ssh._tcp.host2.example. 3600 SRV <SRV RDATA>
-- subdel.example. 3600 NS ns.example.com.
-- subdel.example. 3600 NS ns.example.net.
--
-- A look at the domain names in a tree structure is helpful:
--
-- |
-- -------------example------------
-- / / \ \
-- / / \ \
-- / / \ \
-- * host1 host2 subdel
-- | | |
-- | | |
-- sub _tcp _tcp
-- | |
-- | |
-- _ssh _ssh
--
-- The following responses would be synthesized from one of the
-- wildcards in the zone:
--
-- QNAME=host3.example. QTYPE=MX, QCLASS=IN
-- the answer will be a "host3.example. IN MX ..."
--
-- QNAME=host3.example. QTYPE=A, QCLASS=IN
-- the answer will reflect "no error, but no data"
-- because there is no A RR set at '*.example.'
--
-- QNAME=foo.bar.example. QTYPE=TXT, QCLASS=IN
-- the answer will be "foo.bar.example. IN TXT ..."
-- because bar.example. does not exist, but the wildcard
-- does.
--
-- The following responses would not be synthesized from any of the
-- wildcards in the zone:
--
-- QNAME=host1.example., QTYPE=MX, QCLASS=IN
-- because host1.example. exists
--
-- QNAME=sub.*.example., QTYPE=MX, QCLASS=IN
-- because sub.*.example. exists
--
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--
-- QNAME=_telnet._tcp.host1.example., QTYPE=SRV, QCLASS=IN
-- because _tcp.host1.example. exists (without data)
--
-- QNAME=host.subdel.example., QTYPE=A, QCLASS=IN
-- because subdel.example. exists (and is a zone cut)
--
-- QNAME=ghost.*.example., QTYPE=MX, QCLASS=IN
-- because *.example. exists
--
-- The final example highlights one common misconception about
-- wildcards. A wildcard "blocks itself" in the sense that a
-- wildcard does not match its own subdomains. I.e. "*.example."
-- does not match all names in the "example." zone, it fails to
-- match the names below "*.example." To cover names under
-- "*.example.", another wild card domain name is needed -
-- "*.*.example." - which covers all but it's own subdomains.
--
--2.2.2 Empty Non-terminals
--
-- Empty non-terminals [RFC2136, Section 7.16] are domain names
-- that own no resource records but have subdomains that do. In
-- section 2.2.1, "_tcp.host1.example." is an example of a empty
-- non-terminal name. Empty non-terminals are introduced by this
-- text in section 3.1 of RFC 1034:
--
--# The domain name space is a tree structure. Each node and leaf on
--# the tree corresponds to a resource set (which may be empty). The
--# domain system makes no distinctions between the uses of the
--# interior nodes and leaves, and this memo uses the term "node" to
--# refer to both.
--
-- The parenthesized "which may be empty" specifies that empty non-
-- terminals are explicitly recognized, and that empty non-terminals
-- "exist."
--
-- Pedantically reading the above paragraph can lead to an
-- interpretation that all possible domains exist - up to the
-- suggested limit of 255 octets for a domain name [RFC1035].
-- For example, www.example. may have an A RR, and as far as is
-- practically concerned, is a leaf of the domain tree. But the
-- definition can be taken to mean that sub.www.example. also
-- exists, albeit with no data. By extension, all possible domains
-- exist, from the root on down.
--
-- As RFC 1034 also defines "an authoritative name error indicating
-- that the name does not exist" in section 4.3.1, so this apparently
-- is not the intent of the original definition, justifying the
-- need for an updated definition in the next section.
--
--
--
--
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--
--2.2.3 Yet Another Definition of Existence
--
-- RFC1034's wording is fixed by the following paragraph:
--
-- The domain name space is a tree structure. Nodes in the tree
-- either own at least one RRSet and/or have descendants that
-- collectively own at least one RRSet. A node may exist with no
-- RRSets only if it has descendents that do, this node is an empty
-- non-terminal.
--
-- A node with no descendants is a leaf node. Empty leaf nodes do
-- not exist.
--
-- Note that at a zone boundary, the domain name owns data,
-- including the NS RR set. In the delegating zone, the NS RR
-- set is not authoritative, but that is of no consequence here.
-- The domain name owns data, therefore, it exists.
--
--2.3 When is a Wild Card Domain Name Not Special
--
-- When a wild card domain name appears in a message's query section,
-- no special processing occurs. An asterisk label in a query name
-- only matches a single, corresponding asterisk label in the
-- existing zone tree when the 4.3.2 algorithm is being followed.
--
-- When a wild card domain name appears in the resource data of a
-- record, no special processing occurs. An asterisk label in that
-- context literally means just an asterisk.
--
--3. Impact of a Wild Card Domain Name On a Response
--
-- RFC 1034's description of how wildcards impact response
-- generation is in its section 4.3.2. That passage contains the
-- algorithm followed by a server in constructing a response.
-- Within that algorithm, step 3, part 'c' defines the behavior of
-- the wildcard.
--
-- The algorithm in section 4.3.2. is not intended to be pseudo-code,
-- i.e., its steps are not intended to be followed in strict order.
-- The "algorithm" is a suggested means of implementing the
-- requirements. As such, in step 3, parts a, b, and c, do not have
-- to be implemented in that order, provided that the result of the
-- implemented code is compliant with the protocol's specification.
--
--3.1 Step 2
--
-- Step 2 of section 4.3.2 reads:
--
--# 2. Search the available zones for the zone which is the nearest
--# ancestor to QNAME. If such a zone is found, go to step 3,
--# otherwise step 4.
--
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--
-- In this step, the most appropriate zone for the response is
-- chosen. The significance of this step is that it means all of
-- step 3 is being performed within one zone. This has significance
-- when considering whether or not an SOA RR can be ever be used for
-- synthesis.
--
--3.2 Step 3
--
-- Step 3 is dominated by three parts, labelled 'a', 'b', and 'c'.
-- But the beginning of the step is important and needs explanation.
--
--# 3. Start matching down, label by label, in the zone. The
--# matching process can terminate several ways:
--
-- The word 'matching' refers to label matching. The concept
-- is based in the view of the zone as the tree of existing names.
-- The query name is considered to be an ordered sequence of
-- labels - as if the name were a path from the root to the owner
-- of the desired data. (Which it is - 3rd paragraph of RFC 1034,
-- section 3.1.)
--
-- The process of label matching a query name ends in exactly one of
-- three choices, the parts 'a', 'b', and 'c'. Either the name is
-- found, the name is below a cut point, or the name is not found.
--
-- Once one of the parts is chosen, the other parts are not
-- considered. (E.g., do not execute part 'c' and then change
-- the execution path to finish in part 'b'.) The process of label
-- matching is also done independent of the query type (QTYPE).
--
-- Parts 'a' and 'b' are not an issue for this clarification as they
-- do not relate to record synthesis. Part 'a' is an exact match
-- that results in an answer, part 'b' is a referral.
--
--3.3 Part 'c'
--
-- The context of part 'c' is that the process of label matching the
-- labels of the query name has resulted in a situation in which
-- there is no corresponding label in the tree. It is as if the
-- lookup has "fallen off the tree."
--
--# c. If at some label, a match is impossible (i.e., the
--# corresponding label does not exist), look to see if [...]
--# the "*" label exists.
--
-- To help describe the process of looking 'to see if [...] the "*"
-- label exists' a term has been coined to describe the last domain
-- (node) matched. The term is "closest encloser."
--
--
--
--
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--
--3.3.1 Closest Encloser and the Source of Synthesis
--
-- The closest encloser is the node in the zone's tree of existing
-- domain names that has the most labels matching the query name
-- (consecutively, counting from the root label downward). Each match
-- is a "label match" and the order of the labels is the same.
--
-- The closest encloser is, by definition, an existing name in the
-- zone. The closest encloser might be an empty non-terminal or even
-- be a wild card domain name itself. In no circumstances is the
-- closest encloser to be used to synthesize records for the current
-- query.
--
-- The source of synthesis is defined in the context of a query
-- process as that wild card domain name immediately descending
-- from the closest encloser, provided that this wild card domain
-- name exists. "Immediately descending" means that the source
-- of synthesis has a name of the form:
-- <asterisk label>.<closest encloser>.
-- A source of synthesis does not guarantee having a RRSet to use
-- for synthesis. The source of synthesis could be an empty
-- non-terminal.
--
-- If the source of synthesis does not exist (not on the domain
-- tree), there will be no wildcard synthesis. There is no search
-- for an alternate.
--
-- The important concept is that for any given lookup process, there
-- is at most one place at which wildcard synthetic records can be
-- obtained. If the source of synthesis does not exist, the lookup
-- terminates, the lookup does not look for other wildcard records.
--
--3.3.2 Closest Encloser and Source of Synthesis Examples
--
-- To illustrate, using the example zone in section 2.2.1 of this
-- document, the following chart shows QNAMEs and the closest
-- enclosers.
--
-- QNAME Closest Encloser Source of Synthesis
-- host3.example. example. *.example.
-- _telnet._tcp.host1.example. _tcp.host1.example. no source
-- _telnet._tcp.host2.example. host2.example. no source
-- _telnet._tcp.host3.example. example. *.example.
-- _chat._udp.host3.example. example. *.example.
-- foobar.*.example. *.example. no source
--
--
--
--
--
--
--
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--
--3.3.3 Type Matching
--
-- RFC 1034 concludes part 'c' with this:
--
--# If the "*" label does not exist, check whether the name
--# we are looking for is the original QNAME in the query
--# or a name we have followed due to a CNAME. If the name
--# is original, set an authoritative name error in the
--# response and exit. Otherwise just exit.
--#
--# If the "*" label does exist, match RRs at that node
--# against QTYPE. If any match, copy them into the answer
--# section, but set the owner of the RR to be QNAME, and
--# not the node with the "*" label. Go to step 6.
--
-- The final paragraph covers the role of the QTYPE in the lookup
-- process.
--
-- Based on implementation feedback and similarities between step
-- 'a' and step 'c' a change to this passage has been made.
--
-- The change is to add the following text to step 'c' prior to the
-- instructions to "go to step 6":
--
-- If the data at the source of synthesis is a CNAME, and
-- QTYPE doesn't match CNAME, copy the CNAME RR into the
-- answer section of the response changing the owner name
-- to the QNAME, change QNAME to the canonical name in the
-- CNAME RR, and go back to step 1.
--
-- This is essentially the same text in step a covering the
-- processing of CNAME RRSets.
--
--4. Considerations with Special Types
--
-- Sections 2 and 3 of this document discuss wildcard synthesis
-- with respect to names in the domain tree and ignore the impact
-- of types. In this section, the implication of wildcards of
-- specific types are discussed. The types covered are those
-- that have proven to be the most difficult to understand. The
-- types are SOA, NS, CNAME, DNAME, SRV, DS, NSEC, RRSIG and
-- "none," i.e., empty non-terminal wild card domain names.
--
--4.1 SOA RRSet at a Wild Card Domain Name
--
-- A wild card domain name owning an SOA RRSet means that the
-- domain is at the root of the zone (apex). The domain can not
-- be a source of synthesis because that is, by definition, a
-- descendent node (of the closest encloser) and a zone apex is
-- at the top of the zone.
--
--
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--
-- Although a wild card domain name owning an SOA RRSet can never
-- be a source of synthesis, there is no reason to forbid the
-- ownership of an SOA RRSet.
--
-- E.g., given this zone:
-- $ORIGIN *.example.
-- @ 3600 IN SOA <SOA RDATA>
-- 3600 NS ns1.example.com.
-- 3600 NS ns1.example.net.
-- www 3600 TXT "the www txt record"
--
-- A query for www.*.example.'s TXT record would still find the
-- "the www txt record" answer. The asterisk label only becomes
-- significant when section 4.3.2, step 3 part 'c' is in effect.
--
-- Of course, there would need to be a delegation in the parent
-- zone, "example." for this to work too. This is covered in the
-- next section.
--
--4.2 NS RRSet at a Wild Card Domain Name
--
-- With the definition of DNSSEC [RFC4033, RFC4034, RFC4035] now
-- in place, the semantics of a wild card domain name owning an
-- NS RRSet has come to be poorly defined. The dilemma relates to
-- a conflict between the rules for synthesis in part 'c' and the
-- fact that the resulting synthesis generates a record for which
-- the zone is not authoritative. In a DNSSEC signed zone, the
-- mechanics of signature management (generation and inclusion
-- in a message) have become unclear.
--
-- Salient points of the working group discussion on this topic is
-- summarized in section 4.2.1.
--
-- As a result of these discussion, there is no definition given for
-- wild card domain names owning an NS RRSet. The semantics are
-- left undefined until there is a clear need to have a set defined,
-- and until there is a clear direction to proceed. Operationally,
-- inclusion of wild card NS RRSets in a zone is discouraged, but
-- not barred.
--
--4.2.1 Discarded Notions
--
-- Prior to DNSSEC, a wild card domain name owning a NS RRSet
-- appeared to be workable, and there are some instances in which
-- it is found in deployments using implementations that support
-- this. Continuing to allow this in the specification is not
-- tenable with DNSSEC. The reason is that the synthesis of the
-- NS RRSet is being done in a zone that has delegated away the
-- responsibility for the name. This "unauthorized" synthesis is
-- not a problem for the base DNS protocol, but DNSSEC, in affirming
-- the authorization model for DNS exposes the problem.
--
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--
-- Outright banning of wildcards of type NS is also untenable as
-- the DNS protocol does not define how to handle "illegal" data.
-- Implementations may choose not to load a zone, but there is no
-- protocol definition. The lack of the definition is complicated
-- by having to cover dynamic update [RFC 2136], zone transfers,
-- as well as loading at the master server. The case of a client
-- (resolver, caching server) getting a wildcard of type NS in
-- a reply would also have to be considered.
--
-- Given the daunting challenge of a complete definition of how to
-- ban such records, dealing with existing implementations that
-- permit the records today is a further complication. There are
-- uses of wild card domain name owning NS RRSets.
--
-- One compromise proposed would have redefined wildcards of type
-- NS to not be used in synthesis, this compromise fell apart
-- because it would have required significant edits to the DNSSEC
-- signing and validation work. (Again, DNSSEC catches
-- unauthorized data.)
--
-- With no clear consensus forming on the solution to this dilemma,
-- and the realization that wildcards of type NS are a rarity in
-- operations, the best course of action is to leave this open-ended
-- until "it matters."
--
--4.3 CNAME RRSet at a Wild Card Domain Name
--
-- The issue of a CNAME RRSet owned by a wild card domain name has
-- prompted a suggested change to the last paragraph of step 3c of
-- the algorithm in 4.3.2. The changed text appears in section
-- 3.3.3 of this document.
--
--4.4 DNAME RRSet at a Wild Card Domain Name
--
-- Ownership of a DNAME [RFC2672] RRSet by a wild card domain name
-- represents a threat to the coherency of the DNS and is to be
-- avoided or outright rejected. Such a DNAME RRSet represents
-- non-deterministic synthesis of rules fed to different caches.
-- As caches are fed the different rules (in an unpredictable
-- manner) the caches will cease to be coherent. ("As caches
-- are fed" refers to the storage in a cache of records obtained
-- in responses by recursive or iterative servers.)
--
-- For example, assume one cache, responding to a recursive
-- request, obtains the record:
-- "a.b.example. DNAME foo.bar.example.net."
-- and another cache obtains:
-- "b.example. DNAME foo.bar.example.net."
-- both generated from the record:
-- "*.example. DNAME foo.bar.example.net."
-- by an authoritative server.
--
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--
-- The DNAME specification is not clear on whether DNAME records
-- in a cache are used to rewrite queries. In some interpretations,
-- the rewrite occurs, in some, it is not. Allowing for the
-- occurrence of rewriting, queries for "sub.a.b.example. A" may
-- be rewritten as "sub.foo.bar.tld. A" by the former caching
-- server and may be rewritten as "sub.a.foo.bar.tld. A" by the
-- latter. Coherency is lost, an operational nightmare ensues.
--
-- Another justification for banning or avoiding wildcard DNAME
-- records is the observation that such a record could synthesize
-- a DNAME owned by "sub.foo.bar.example." and "foo.bar.example."
-- There is a restriction in the DNAME definition that no domain
-- exist below a DNAME-owning domain, hence, the wildcard DNAME
-- is not to be permitted.
--
--4.5 SRV RRSet at a Wild Card Domain Name
--
-- The definition of the SRV RRset is RFC 2782 [RFC2782]. In the
-- definition of the record, there is some confusion over the term
-- "Name." The definition reads as follows:
--
--# The format of the SRV RR
--...
--# _Service._Proto.Name TTL Class SRV Priority Weight Port Target
--...
--# Name
--# The domain this RR refers to. The SRV RR is unique in that the
--# name one searches for is not this name; the example near the end
--# shows this clearly.
--
-- Do not confuse the definition "Name" with the owner name. I.e.,
-- once removing the _Service and _Proto labels from the owner name
-- of the SRV RRSet, what remains could be a wild card domain name
-- but this is immaterial to the SRV RRSet.
--
-- E.g., If an SRV record is:
-- _foo._udp.*.example. 10800 IN SRV 0 1 9 old-slow-box.example.
--
-- *.example is a wild card domain name and although it is the Name
-- of the SRV RR, it is not the owner (domain name). The owner
-- domain name is "_foo._udp.*.example." which is not a wild card
-- domain name.
--
-- The confusion is likely based on the mixture of the specification
-- of the SRV RR and the description of a "use case."
--
--4.6 DS RRSet at a Wild Card Domain Name
--
-- A DS RRSet owned by a wild card domain name is meaningless and
-- harmless. This statement is made in the context that an NS RRSet
-- at a wild card domain name is undefined. At a non-delegation
--
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--
-- point, a DS RRSet has no value (no corresponding DNSKEY RRSet
-- will be used in DNSSEC validation). If there is a synthesized
-- DS RRSet, it alone will not be very useful as it exists in the
-- context of a delegation point.
--
--4.7 NSEC RRSet at a Wild Card Domain Name
--
-- Wild card domain names in DNSSEC signed zones will have an NSEC
-- RRSet. Synthesis of these records will only occur when the
-- query exactly matches the record. Synthesized NSEC RR's will not
-- be harmful as they will never be used in negative caching or to
-- generate a negative response. [RFC2308]
--
--4.8 RRSIG at a Wild Card Domain Name
--
-- RRSIG records will be present at a wild card domain name in a
-- signed zone, and will be synthesized along with data sought in a
-- query. The fact that the owner name is synthesized is not a
-- problem as the label count in the RRSIG will instruct the
-- verifying code to ignore it.
--
--4.9 Empty Non-terminal Wild Card Domain Name
--
-- If a source of synthesis is an empty non-terminal, then the
-- response will be one of no error in the return code and no RRSet
-- in the answer section.
--
--5. Security Considerations
--
-- This document is refining the specifications to make it more
-- likely that security can be added to DNS. No functional
-- additions are being made, just refining what is considered
-- proper to allow the DNS, security of the DNS, and extending
-- the DNS to be more predictable.
--
--6. IANA Considerations
--
-- None.
--
--7. References
--
-- Normative References
--
-- [RFC20] ASCII Format for Network Interchange, V.G. Cerf,
-- Oct-16-1969
--
-- [RFC1034] Domain Names - Concepts and Facilities,
-- P.V. Mockapetris, Nov-01-1987
--
-- [RFC1035] Domain Names - Implementation and Specification, P.V
-- Mockapetris, Nov-01-1987
--
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--
-- [RFC1995] Incremental Zone Transfer in DNS, M. Ohta, August 1996
--
-- [RFC2119] Key Words for Use in RFCs to Indicate Requirement
-- Levels, S Bradner, March 1997
--
-- [RFC2308] Negative Caching of DNS Queries (DNS NCACHE),
-- M. Andrews, March 1998
--
-- [RFC2672] Non-Terminal DNS Name Redirection, M. Crawford,
-- August 1999.
--
-- [RFC2782] A DNS RR for specifying the location of services (DNS
-- SRV), A. Gulbrandsen, et.al., February 2000
--
-- [RFC4033] DNS Security Introduction and Requirements, R. Arends,
-- et.al., March 2005
--
-- [RFC4034] Resource Records for the DNS Security Extensions,
-- R. Arends, et.al., March 2005
--
-- [RFC4035] Protocol Modifications for the DNS Security Extensions,
-- R. Arends, et.al., March 2005
--
-- Informative References
--
-- [RFC2136] Dynamic Updates in the Domain Name System (DNS UPDATE),
-- P. Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound,
-- April 1997
--
--8. Editor
--
-- Name: Edward Lewis
-- Affiliation: NeuStar
-- Address: 46000 Center Oak Plaza, Sterling, VA, 20166, US
-- Phone: +1-571-434-5468
-- Email: ed.lewis@neustar.biz
--
-- Comments on this document can be sent to the editor or the mailing
-- list for the DNSEXT WG, namedroppers@ops.ietf.org.
--
--9. Others Contributing to the Document
--
-- This document represents the work of a large working group. The
-- editor merely recorded the collective wisdom of the working group.
--
--
--
--
--
--
--
--
--
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--
--10. Trailing Boilerplate
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided
-- on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION
-- HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET
-- SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
-- WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
-- ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
-- INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
-- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of
-- any Intellectual Property Rights or other rights that might
-- be claimed to pertain to the implementation or use of the
-- technology described in this document or the extent to which
-- any license under such rights might or might not be available;
-- nor does it represent that it has made any independent effort
-- to identify any such rights. Information on the procedures
-- with respect to rights in RFC documents can be found in BCP 78
-- and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the
-- use of such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR
-- repository at http://www.ietf.org/ipr. The IETF invites any
-- interested party to bring to its attention any copyrights,
-- patents or patent applications, or other proprietary rights
-- that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--Expiration
--
-- This document expires on or about July 9, 2006.
--
--
--
--DNSEXT Working Group Expires July 9, 2006 [Page 19]
+++ /dev/null
--
--
--
--DNS Operations M. Larson
--Internet-Draft P. Barber
--Expires: August 14, 2006 VeriSign
-- February 10, 2006
--
--
-- Observed DNS Resolution Misbehavior
-- draft-ietf-dnsop-bad-dns-res-05
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on August 14, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This memo describes DNS iterative resolver behavior that results in a
-- significant query volume sent to the root and top-level domain (TLD)
-- name servers. We offer implementation advice to iterative resolver
-- developers to alleviate these unnecessary queries. The
-- recommendations made in this document are a direct byproduct of
-- observation and analysis of abnormal query traffic patterns seen at
-- two of the thirteen root name servers and all thirteen com/net TLD
-- name servers.
--
--
--
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--
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119 [1].
--
--
--Table of Contents
--
-- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
-- 1.1. A note about terminology in this memo . . . . . . . . . . 3
-- 2. Observed iterative resolver misbehavior . . . . . . . . . . . 5
-- 2.1. Aggressive requerying for delegation information . . . . . 5
-- 2.1.1. Recommendation . . . . . . . . . . . . . . . . . . . . 6
-- 2.2. Repeated queries to lame servers . . . . . . . . . . . . . 7
-- 2.2.1. Recommendation . . . . . . . . . . . . . . . . . . . . 7
-- 2.3. Inability to follow multiple levels of indirection . . . . 8
-- 2.3.1. Recommendation . . . . . . . . . . . . . . . . . . . . 9
-- 2.4. Aggressive retransmission when fetching glue . . . . . . . 9
-- 2.4.1. Recommendation . . . . . . . . . . . . . . . . . . . . 10
-- 2.5. Aggressive retransmission behind firewalls . . . . . . . . 10
-- 2.5.1. Recommendation . . . . . . . . . . . . . . . . . . . . 11
-- 2.6. Misconfigured NS records . . . . . . . . . . . . . . . . . 11
-- 2.6.1. Recommendation . . . . . . . . . . . . . . . . . . . . 12
-- 2.7. Name server records with zero TTL . . . . . . . . . . . . 12
-- 2.7.1. Recommendation . . . . . . . . . . . . . . . . . . . . 13
-- 2.8. Unnecessary dynamic update messages . . . . . . . . . . . 13
-- 2.8.1. Recommendation . . . . . . . . . . . . . . . . . . . . 14
-- 2.9. Queries for domain names resembling IPv4 addresses . . . . 14
-- 2.9.1. Recommendation . . . . . . . . . . . . . . . . . . . . 14
-- 2.10. Misdirected recursive queries . . . . . . . . . . . . . . 15
-- 2.10.1. Recommendation . . . . . . . . . . . . . . . . . . . . 15
-- 2.11. Suboptimal name server selection algorithm . . . . . . . . 15
-- 2.11.1. Recommendation . . . . . . . . . . . . . . . . . . . . 16
-- 3. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
-- 4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 18
-- 5. Security considerations . . . . . . . . . . . . . . . . . . . 19
-- 6. Internationalization considerations . . . . . . . . . . . . . 20
-- 7. Informative References . . . . . . . . . . . . . . . . . . . . 20
-- Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
-- Intellectual Property and Copyright Statements . . . . . . . . . . 22
--
--
--
--
--
--
--
--
--
--
--
--
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--
--1. Introduction
--
-- Observation of query traffic received by two root name servers and
-- the thirteen com/net TLD name servers has revealed that a large
-- proportion of the total traffic often consists of "requeries". A
-- requery is the same question (<QNAME, QTYPE, QCLASS>) asked
-- repeatedly at an unexpectedly high rate. We have observed requeries
-- from both a single IP address and multiple IP addresses (i.e., the
-- same query received simultaneously from multiple IP addresses).
--
-- By analyzing requery events we have found that the cause of the
-- duplicate traffic is almost always a deficient iterative resolver,
-- stub resolver or application implementation combined with an
-- operational anomaly. The implementation deficiencies we have
-- identified to date include well-intentioned recovery attempts gone
-- awry, insufficient caching of failures, early abort when multiple
-- levels of indirection must be followed, and aggressive retry by stub
-- resolvers or applications. Anomalies that we have seen trigger
-- requery events include lame delegations, unusual glue records, and
-- anything that makes all authoritative name servers for a zone
-- unreachable (DoS attacks, crashes, maintenance, routing failures,
-- congestion, etc.).
--
-- In the following sections, we provide a detailed explanation of the
-- observed behavior and recommend changes that will reduce the requery
-- rate. None of the changes recommended affects the core DNS protocol
-- specification; instead, this document consists of guidelines to
-- implementors of iterative resolvers.
--
--1.1. A note about terminology in this memo
--
-- To recast an old saying about standards, the nice thing about DNS
-- terms is that there are so many of them to choose from. Writing or
-- talking about DNS can be difficult and cause confusion resulting from
-- a lack of agreed-upon terms for its various components. Further
-- complicating matters are implementations that combine multiple roles
-- into one piece of software, which makes naming the result
-- problematic. An example is the entity that accepts recursive
-- queries, issues iterative queries as necessary to resolve the initial
-- recursive query, caches responses it receives, and which is also able
-- to answer questions about certain zones authoritatively. This entity
-- is an iterative resolver combined with an authoritative name server
-- and is often called a "recursive name server" or a "caching name
-- server".
--
-- This memo is concerned principally with the behavior of iterative
-- resolvers, which are typically found as part of a recursive name
-- server. This memo uses the more precise term "iterative resolver",
--
--
--
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--
-- because the focus is usually on that component. In instances where
-- the name server role of this entity requires mentioning, this memo
-- uses the term "recursive name server". As an example of the
-- difference, the name server component of a recursive name server
-- receives DNS queries and the iterative resolver component sends
-- queries.
--
-- The advent of IPv6 requires mentioning AAAA records as well as A
-- records when discussing glue. To avoid continuous repetition and
-- qualification, this memo uses the general term "address record" to
-- encompass both A and AAAA records when a particular situation is
-- relevant to both types.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
--
--2. Observed iterative resolver misbehavior
--
--2.1. Aggressive requerying for delegation information
--
-- There can be times when every name server in a zone's NS RRset is
-- unreachable (e.g., during a network outage), unavailable (e.g., the
-- name server process is not running on the server host) or
-- misconfigured (e.g., the name server is not authoritative for the
-- given zone, also known as "lame"). Consider an iterative resolver
-- that attempts to resolve a query for a domain name in such a zone and
-- discovers that none of the zone's name servers can provide an answer.
-- We have observed a recursive name server implementation whose
-- iterative resolver then verifies the zone's NS RRset in its cache by
-- querying for the zone's delegation information: it sends a query for
-- the zone's NS RRset to one of the parent zone's name servers. (Note
-- that queries with QTYPE=NS are not required by the standard
-- resolution algorithm described in section 4.3.2 of RFC 1034 [2].
-- These NS queries represent this implementation's addition to that
-- algorithm.)
--
-- For example, suppose that "example.com" has the following NS RRset:
--
-- example.com. IN NS ns1.example.com.
-- example.com. IN NS ns2.example.com.
--
-- Upon receipt of a query for "www.example.com" and assuming that
-- neither "ns1.example.com" nor "ns2.example.com" can provide an
-- answer, this iterative resolver implementation immediately queries a
-- "com" zone name server for the "example.com" NS RRset to verify it
-- has the proper delegation information. This implementation performs
-- this query to a zone's parent zone for each recursive query it
-- receives that fails because of a completely unresponsive set of name
-- servers for the target zone. Consider the effect when a popular zone
-- experiences a catastrophic failure of all its name servers: now every
-- recursive query for domain names in that zone sent to this recursive
-- name server implementation results in a query to the failed zone's
-- parent name servers. On one occasion when several dozen popular
-- zones became unreachable, the query load on the com/net name servers
-- increased by 50%.
--
-- We believe this verification query is not reasonable. Consider the
-- circumstances: When an iterative resolver is resolving a query for a
-- domain name in a zone it has not previously searched, it uses the
-- list of name servers in the referral from the target zone's parent.
-- If on its first attempt to search the target zone, none of the name
-- servers in the referral is reachable, a verification query to the
-- parent would be pointless: this query to the parent would come so
-- quickly on the heels of the referral that it would be almost certain
--
--
--
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--
--
-- to contain the same list of name servers. The chance of discovering
-- any new information is slim.
--
-- The other possibility is that the iterative resolver successfully
-- contacts one of the target zone's name servers and then caches the NS
-- RRset from the authority section of a response, the proper behavior
-- according to section 5.4.1 of RFC 2181 [3], because the NS RRset from
-- the target zone is more trustworthy than delegation information from
-- the parent zone. If, while processing a subsequent recursive query,
-- the iterative resolver discovers that none of the name servers
-- specified in the cached NS RRset is available or authoritative,
-- querying the parent would be wrong. An NS RRset from the parent zone
-- would now be less trustworthy than data already in the cache.
--
-- For this query of the parent zone to be useful, the target zone's
-- entire set of name servers would have to change AND the former set of
-- name servers would have to be deconfigured or decommissioned AND the
-- delegation information in the parent zone would have to be updated
-- with the new set of name servers, all within the TTL of the target
-- zone's NS RRset. We believe this scenario is uncommon:
-- administrative best practices dictate that changes to a zone's set of
-- name servers happen gradually when at all possible, with servers
-- removed from the NS RRset left authoritative for the zone as long as
-- possible. The scenarios that we can envision that would benefit from
-- the parent requery behavior do not outweigh its damaging effects.
--
-- This section should not be understood to claim that all queries to a
-- zone's parent are bad. In some cases, such queries are not only
-- reasonable but required. Consider the situation when required
-- information, such as the address of a name server (i.e., the address
-- record corresponding to the RDATA of an NS record), has timed out of
-- an iterative resolver's cache before the corresponding NS record. If
-- the name of the name server is below the apex of the zone, then the
-- name server's address record is only available as glue in the parent
-- zone. For example, consider this NS record:
--
-- example.com. IN NS ns.example.com.
--
-- If a cache has this NS record but not the address record for
-- "ns.example.com", it is unable to contact the "example.com" zone
-- directly and must query the "com" zone to obtain the address record.
-- Note, however, that such a query would not have QTYPE=NS according to
-- the standard resolution algorithm.
--
--2.1.1. Recommendation
--
-- An iterative resolver MUST NOT send a query for the NS RRset of a
-- non-responsive zone to any of the name servers for that zone's parent
--
--
--
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--
--
-- zone. For the purposes of this injunction, a non-responsive zone is
-- defined as a zone for which every name server listed in the zone's NS
-- RRset:
--
-- 1. is not authoritative for the zone (i.e., lame), or,
--
-- 2. returns a server failure response (RCODE=2), or,
--
-- 3. is dead or unreachable according to section 7.2 of RFC 2308 [4].
--
--2.2. Repeated queries to lame servers
--
-- Section 2.1 describes a catastrophic failure: when every name server
-- for a zone is unable to provide an answer for one reason or another.
-- A more common occurrence is when a subset of a zone's name servers
-- are unavailable or misconfigured. Different failure modes have
-- different expected durations. Some symptoms indicate problems that
-- are potentially transient; for example, various types of ICMP
-- unreachable messages because a name server process is not running or
-- a host or network is unreachable, or a complete lack of a response to
-- a query. Such responses could be the result of a host rebooting or
-- temporary outages; these events don't necessarily require any human
-- intervention and can be reasonably expected to be temporary.
--
-- Other symptoms clearly indicate a condition requiring human
-- intervention, such as lame server: if a name server is misconfigured
-- and not authoritative for a zone delegated to it, it is reasonable to
-- assume that this condition has potential to last longer than
-- unreachability or unresponsiveness. Consequently, repeated queries
-- to known lame servers are not useful. In this case of a condition
-- with potential to persist for a long time, a better practice would be
-- to maintain a list of known lame servers and avoid querying them
-- repeatedly in a short interval.
--
-- It should also be noted, however, that some authoritative name server
-- implementations appear to be lame only for queries of certain types
-- as described in RFC 4074 [5]. In this case, it makes sense to retry
-- the "lame" servers for other types of queries, particularly when all
-- known authoritative name servers appear to be "lame".
--
--2.2.1. Recommendation
--
-- Iterative resolvers SHOULD cache name servers that they discover are
-- not authoritative for zones delegated to them (i.e. lame servers).
-- If this caching is performed, lame servers MUST be cached against the
-- specific query tuple <zone name, class, server IP address>. Zone
-- name can be derived from the owner name of the NS record that was
-- referenced to query the name server that was discovered to be lame.
--
--
--
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--
--
-- Implementations that perform lame server caching MUST refrain from
-- sending queries to known lame servers based on a time interval from
-- when the server is discovered to be lame. A minimum interval of
-- thirty minutes is RECOMMENDED.
--
-- An exception to this recommendation occurs if all name servers for a
-- zone are marked lame. In that case, the iterative resolver SHOULD
-- temporarily ignore the servers' lameness status and query one or more
-- servers. This behavior is a workaround for the type-specific
-- lameness issue described in the previous section.
--
-- Implementors should take care not to make lame server avoidance logic
-- overly broad: note that a name server could be lame for a parent zone
-- but not a child zone, e.g., lame for "example.com" but properly
-- authoritative for "sub.example.com". Therefore a name server should
-- not be automatically considered lame for subzones. In the case
-- above, even if a name server is known to be lame for "example.com",
-- it should be queried for QNAMEs at or below "sub.example.com" if an
-- NS record indicates it should be authoritative for that zone.
--
--2.3. Inability to follow multiple levels of indirection
--
-- Some iterative resolver implementations are unable to follow
-- sufficient levels of indirection. For example, consider the
-- following delegations:
--
-- foo.example. IN NS ns1.example.com.
-- foo.example. IN NS ns2.example.com.
--
-- example.com. IN NS ns1.test.example.net.
-- example.com. IN NS ns2.test.example.net.
--
-- test.example.net. IN NS ns1.test.example.net.
-- test.example.net. IN NS ns2.test.example.net.
--
-- An iterative resolver resolving the name "www.foo.example" must
-- follow two levels of indirection, first obtaining address records for
-- "ns1.test.example.net" or "ns2.test.example.net" in order to obtain
-- address records for "ns1.example.com" or "ns2.example.com" in order
-- to query those name servers for the address records of
-- "www.foo.example". While this situation may appear contrived, we
-- have seen multiple similar occurrences and expect more as new generic
-- top-level domains (gTLDs) become active. We anticipate many zones in
-- new gTLDs will use name servers in existing gTLDs, increasing the
-- number of delegations using out-of-zone name servers.
--
--
--
--
--
--
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--
--
--2.3.1. Recommendation
--
-- Clearly constructing a delegation that relies on multiple levels of
-- indirection is not a good administrative practice. However, the
-- practice is widespread enough to require that iterative resolvers be
-- able to cope with it. Iterative resolvers SHOULD be able to handle
-- arbitrary levels of indirection resulting from out-of-zone name
-- servers. Iterative resolvers SHOULD implement a level-of-effort
-- counter to avoid loops or otherwise performing too much work in
-- resolving pathological cases.
--
-- A best practice that avoids this entire issue of indirection is to
-- name one or more of a zone's name servers in the zone itself. For
-- example, if the zone is named "example.com", consider naming some of
-- the name servers "ns{1,2,...}.example.com" (or similar).
--
--2.4. Aggressive retransmission when fetching glue
--
-- When an authoritative name server responds with a referral, it
-- includes NS records in the authority section of the response.
-- According to the algorithm in section 4.3.2 of RFC 1034 [2], the name
-- server should also "put whatever addresses are available into the
-- additional section, using glue RRs if the addresses are not available
-- from authoritative data or the cache." Some name server
-- implementations take this address inclusion a step further with a
-- feature called "glue fetching". A name server that implements glue
-- fetching attempts to include address records for every NS record in
-- the authority section. If necessary, the name server issues multiple
-- queries of its own to obtain any missing address records.
--
-- Problems with glue fetching can arise in the context of
-- "authoritative-only" name servers, which only serve authoritative
-- data and ignore requests for recursion. Such an entity will not
-- normally generate any queries of its own. Instead it answers non-
-- recursive queries from iterative resolvers looking for information in
-- zones it serves. With glue fetching enabled, however, an
-- authoritative server invokes an iterative resolver to look up an
-- unknown address record to complete the additional section of a
-- response.
--
-- We have observed situations where the iterative resolver of a glue-
-- fetching name server can send queries that reach other name servers,
-- but is apparently prevented from receiving the responses. For
-- example, perhaps the name server is authoritative-only and therefore
-- its administrators expect it to receive only queries and not
-- responses. Perhaps unaware of glue fetching and presuming that the
-- name server's iterative resolver will generate no queries, its
-- administrators place the name server behind a network device that
--
--
--
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--
-- prevents it from receiving responses. If this is the case, all glue-
-- fetching queries will go answered.
--
-- We have observed name server implementations whose iterative
-- resolvers retry excessively when glue-fetching queries are
-- unanswered. A single com/net name server has received hundreds of
-- queries per second from a single such source. Judging from the
-- specific queries received and based on additional analysis, we
-- believe these queries result from overly aggressive glue fetching.
--
--2.4.1. Recommendation
--
-- Implementers whose name servers support glue fetching SHOULD take
-- care to avoid sending queries at excessive rates. Implementations
-- SHOULD support throttling logic to detect when queries are sent but
-- no responses are received.
--
--2.5. Aggressive retransmission behind firewalls
--
-- A common occurrence and one of the largest sources of repeated
-- queries at the com/net and root name servers appears to result from
-- resolvers behind misconfigured firewalls. In this situation, an
-- iterative resolver is apparently allowed to send queries through a
-- firewall to other name servers, but not receive the responses. The
-- result is more queries than necessary because of retransmission, all
-- of which are useless because the responses are never received. Just
-- as with the glue-fetching scenario described in Section 2.4, the
-- queries are sometimes sent at excessive rates. To make matters
-- worse, sometimes the responses, sent in reply to legitimate queries,
-- trigger an alarm on the originator's intrusion detection system. We
-- are frequently contacted by administrators responding to such alarms
-- who believe our name servers are attacking their systems.
--
-- Not only do some resolvers in this situation retransmit queries at an
-- excessive rate, but they continue to do so for days or even weeks.
-- This scenario could result from an organization with multiple
-- recursive name servers, only a subset of whose iterative resolvers'
-- traffic is improperly filtered in this manner. Stub resolvers in the
-- organization could be configured to query multiple recursive name
-- servers. Consider the case where a stub resolver queries a filtered
-- recursive name server first. The iterative resolver of this
-- recursive name server sends one or more queries whose replies are
-- filtered, so it can't respond to the stub resolver, which times out.
-- Then the stub resolver retransmits to a recursive name server that is
-- able to provide an answer. Since resolution ultimately succeeds the
-- underlying problem might not be recognized or corrected. A popular
-- stub resolver implementation has a very aggressive retransmission
-- schedule, including simultaneous queries to multiple recursive name
--
--
--
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--
-- servers, which could explain how such a situation could persist
-- without being detected.
--
--2.5.1. Recommendation
--
-- The most obvious recommendation is that administrators SHOULD take
-- care not to place iterative resolvers behind a firewall that allows
-- queries to pass through but not the resulting replies.
--
-- Iterative resolvers SHOULD take care to avoid sending queries at
-- excessive rates. Implementations SHOULD support throttling logic to
-- detect when queries are sent but no responses are received.
--
--2.6. Misconfigured NS records
--
-- Sometimes a zone administrator forgets to add the trailing dot on the
-- domain names in the RDATA of a zone's NS records. Consider this
-- fragment of the zone file for "example.com":
--
-- $ORIGIN example.com.
-- example.com. 3600 IN NS ns1.example.com ; Note missing
-- example.com. 3600 IN NS ns2.example.com ; trailing dots
--
-- The zone's authoritative servers will parse the NS RDATA as
-- "ns1.example.com.example.com" and "ns2.example.com.example.com" and
-- return NS records with this incorrect RDATA in responses, including
-- typically the authority section of every response containing records
-- from the "example.com" zone.
--
-- Now consider a typical sequence of queries. An iterative resolver
-- attempting to resolve address records for "www.example.com" with no
-- cached information for this zone will query a "com" authoritative
-- server. The "com" server responds with a referral to the
-- "example.com" zone, consisting of NS records with valid RDATA and
-- associated glue records. (This example assumes that the
-- "example.com" zone delegation information is correct in the "com"
-- zone.) The iterative resolver caches the NS RRset from the "com"
-- server and follows the referral by querying one of the "example.com"
-- authoritative servers. This server responds with the
-- "www.example.com" address record in the answer section and,
-- typically, the "example.com" NS records in the authority section and,
-- if space in the message remains, glue address records in the
-- additional section. According to Section 5.4 of RFC 2181 [3], NS
-- records in the authority section of an authoritative answer are more
-- trustworthy than NS records from the authority section of a non-
-- authoritative answer. Thus the "example.com" NS RRset just received
-- from the "example.com" authoritative server overrides the
-- "example.com" NS RRset received moments ago from the "com"
--
--
--
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-- authoritative server.
--
-- But the "example.com" zone contains the erroneous NS RRset as shown
-- in the example above. Subsequent queries for names in "example.com"
-- will cause the iterative resolver to attempt to use the incorrect NS
-- records and so it will try to resolve the nonexistent names
-- "ns1.example.com.example.com" and "ns2.example.com.example.com". In
-- this example, since all of the zone's name servers are named in the
-- zone itself (i.e., "ns1.example.com.example.com" and
-- "ns2.example.com.example.com" both end in "example.com") and all are
-- bogus, the iterative resolver cannot reach any "example.com" name
-- servers. Therefore attempts to resolve these names result in address
-- record queries to the "com" authoritative servers. Queries for such
-- obviously bogus glue address records occur frequently at the com/net
-- name servers.
--
--2.6.1. Recommendation
--
-- An authoritative server can detect this situation. A trailing dot
-- missing from an NS record's RDATA always results by definition in a
-- name server name that exists somewhere under the apex of the zone the
-- NS record appears in. Note that further levels of delegation are
-- possible, so a missing trailing dot could inadvertently create a name
-- server name that actually exists in a subzone.
--
-- An authoritative name server SHOULD issue a warning when one of a
-- zone's NS records references a name server below the zone's apex when
-- a corresponding address record does not exist in the zone AND there
-- are no delegated subzones where the address record could exist.
--
--2.7. Name server records with zero TTL
--
-- Sometimes a popular com/net subdomain's zone is configured with a TTL
-- of zero on the zone's NS records, which prohibits these records from
-- being cached and will result in a higher query volume to the zone's
-- authoritative servers. The zone's administrator should understand
-- the consequences of such a configuration and provision resources
-- accordingly. A zero TTL on the zone's NS RRset, however, carries
-- additional consequences beyond the zone itself: if an iterative
-- resolver cannot cache a zone's NS records because of a zero TTL, it
-- will be forced to query that zone's parent's name servers each time
-- it resolves a name in the zone. The com/net authoritative servers do
-- see an increased query load when a popular com/net subdomain's zone
-- is configured with a TTL of zero on the zone's NS records.
--
-- A zero TTL on an RRset expected to change frequently is extreme but
-- permissible. A zone's NS RRset is a special case, however, because
-- changes to it must be coordinated with the zone's parent. In most
--
--
--
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-- zone parent/child relationships we are aware of, there is typically
-- some delay involved in effecting changes. Further, changes to the
-- set of a zone's authoritative name servers (and therefore to the
-- zone's NS RRset) are typically relatively rare: providing reliable
-- authoritative service requires a reasonably stable set of servers.
-- Therefore an extremely low or zero TTL on a zone's NS RRset rarely
-- makes sense, except in anticipation of an upcoming change. In this
-- case, when the zone's administrator has planned a change and does not
-- want iterative resolvers throughout the Internet to cache the NS
-- RRset for a long period of time, a low TTL is reasonable.
--
--2.7.1. Recommendation
--
-- Because of the additional load placed on a zone's parent's
-- authoritative servers resulting from a zero TTL on a zone's NS RRset,
-- under such circumstances authoritative name servers SHOULD issue a
-- warning when loading a zone.
--
--2.8. Unnecessary dynamic update messages
--
-- The UPDATE message specified in RFC 2136 [6] allows an authorized
-- agent to update a zone's data on an authoritative name server using a
-- DNS message sent over the network. Consider the case of an agent
-- desiring to add a particular resource record. Because of zone cuts,
-- the agent does not necessarily know the proper zone to which the
-- record should be added. The dynamic update process requires that the
-- agent determine the appropriate zone so the UPDATE message can be
-- sent to one of the zone's authoritative servers (typically the
-- primary master as specified in the zone's SOA MNAME field).
--
-- The appropriate zone to update is the closest enclosing zone, which
-- cannot be determined only by inspecting the domain name of the record
-- to be updated, since zone cuts can occur anywhere. One way to
-- determine the closest enclosing zone entails walking up the name
-- space tree by sending repeated UPDATE messages until success. For
-- example, consider an agent attempting to add an address record with
-- the name "foo.bar.example.com". The agent could first attempt to
-- update the "foo.bar.example.com" zone. If the attempt failed, the
-- update could be directed to the "bar.example.com" zone, then the
-- "example.com" zone, then the "com" zone, and finally the root zone.
--
-- A popular dynamic agent follows this algorithm. The result is many
-- UPDATE messages received by the root name servers, the com/net
-- authoritative servers, and presumably other TLD authoritative
-- servers. A valid question is why the algorithm proceeds to send
-- updates all the way to TLD and root name servers. This behavior is
-- not entirely unreasonable: in enterprise DNS architectures with an
-- "internal root" design, there could conceivably be private, non-
--
--
--
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--
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-- public TLD or root zones that would be the appropriate targets for a
-- dynamic update.
--
-- A significant deficiency with this algorithm is that knowledge of a
-- given UPDATE message's failure is not helpful in directing future
-- UPDATE messages to the appropriate servers. A better algorithm would
-- be to find the closest enclosing zone by walking up the name space
-- with queries for SOA or NS rather than "probing" with UPDATE
-- messages. Once the appropriate zone is found, an UPDATE message can
-- be sent. In addition, the results of these queries can be cached to
-- aid in determining closest enclosing zones for future updates. Once
-- the closest enclosing zone is determined with this method, the update
-- will either succeed or fail and there is no need to send further
-- updates to higher-level zones. The important point is that walking
-- up the tree with queries yields cacheable information, whereas
-- walking up the tree by sending UPDATE messages does not.
--
--2.8.1. Recommendation
--
-- Dynamic update agents SHOULD send SOA or NS queries to progressively
-- higher-level names to find the closest enclosing zone for a given
-- name to update. Only after the appropriate zone is found should the
-- client send an UPDATE message to one of the zone's authoritative
-- servers. Update clients SHOULD NOT "probe" using UPDATE messages by
-- walking up the tree to progressively higher-level zones.
--
--2.9. Queries for domain names resembling IPv4 addresses
--
-- The root name servers receive a significant number of A record
-- queries where the QNAME looks like an IPv4 address. The source of
-- these queries is unknown. It could be attributed to situations where
-- a user believes an application will accept either a domain name or an
-- IP address in a given configuration option. The user enters an IP
-- address, but the application assumes any input is a domain name and
-- attempts to resolve it, resulting in an A record lookup. There could
-- also be applications that produce such queries in a misguided attempt
-- to reverse map IP addresses.
--
-- These queries result in Name Error (RCODE=3) responses. An iterative
-- resolver can negatively cache such responses, but each response
-- requires a separate cache entry, i.e., a negative cache entry for the
-- domain name "192.0.2.1" does not prevent a subsequent query for the
-- domain name "192.0.2.2".
--
--2.9.1. Recommendation
--
-- It would be desirable for the root name servers not to have to answer
-- these queries: they unnecessarily consume CPU resources and network
--
--
--
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-- bandwidth. A possible solution is to delegate these numeric TLDs
-- from the root zone to a separate set of servers to absorb the
-- traffic. The "black hole servers" used by the AS 112 Project [8],
-- which are currently delegated the in-addr.arpa zones corresponding to
-- RFC 1918 [7] private use address space, would be a possible choice to
-- receive these delegations. Of course, the proper and usual root zone
-- change procedures would have to be followed to make such a change to
-- the root zone.
--
--2.10. Misdirected recursive queries
--
-- The root name servers receive a significant number of recursive
-- queries (i.e., queries with the RD bit set in the header). Since
-- none of the root servers offers recursion, the servers' response in
-- such a situation ignores the request for recursion and the response
-- probably does not contain the data the querier anticipated. Some of
-- these queries result from users configuring stub resolvers to query a
-- root server. (This situation is not hypothetical: we have received
-- complaints from users when this configuration does not work as
-- hoped.) Of course, users should not direct stub resolvers to use
-- name servers that do not offer recursion, but we are not aware of any
-- stub resolver implementation that offers any feedback to the user
-- when so configured, aside from simply "not working".
--
--2.10.1. Recommendation
--
-- When the IP address of a name server that supposedly offers recursion
-- is configured in a stub resolver using an interactive user interface,
-- the resolver could send a test query to verify that the server indeed
-- supports recursion (i.e., verify that the response has the RA bit set
-- in the header). The user could be immediately notified if the server
-- is non-recursive.
--
-- The stub resolver could also report an error, either through a user
-- interface or in a log file, if the queried server does not support
-- recursion. Error reporting SHOULD be throttled to avoid a
-- notification or log message for every response from a non-recursive
-- server.
--
--2.11. Suboptimal name server selection algorithm
--
-- An entire document could be devoted to the topic of problems with
-- different implementations of the recursive resolution algorithm. The
-- entire process of recursion is woefully under specified, requiring
-- each implementor to design an algorithm. Sometimes implementors make
-- poor design choices that could be avoided if a suggested algorithm
-- and best practices were documented, but that is a topic for another
-- document.
--
--
--
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--
-- Some deficiencies cause significant operational impact and are
-- therefore worth mentioning here. One of these is name server
-- selection by an iterative resolver. When an iterative resolver wants
-- to contact one of a zone's authoritative name servers, how does it
-- choose from the NS records listed in the zone's NS RRset? If the
-- selection mechanism is suboptimal, queries are not spread evenly
-- among a zone's authoritative servers. The details of the selection
-- mechanism are up to the implementor, but we offer some suggestions.
--
--2.11.1. Recommendation
--
-- This list is not conclusive, but reflects the changes that would
-- produce the most impact in terms of reducing disproportionate query
-- load among a zone's authoritative servers. I.e., these changes would
-- help spread the query load evenly.
--
-- o Do not make assumptions based on NS RRset order: all NS RRs SHOULD
-- be treated equally. (In the case of the "com" zone, for example,
-- most of the root servers return the NS record for "a.gtld-
-- servers.net" first in the authority section of referrals.
-- Apparently as a result, this server receives disproportionately
-- more traffic than the other 12 authoritative servers for "com".)
--
-- o Use all NS records in an RRset. (For example, we are aware of
-- implementations that hard-coded information for a subset of the
-- root servers.)
--
-- o Maintain state and favor the best-performing of a zone's
-- authoritative servers. A good definition of performance is
-- response time. Non-responsive servers can be penalized with an
-- extremely high response time.
--
-- o Do not lock onto the best-performing of a zone's name servers. An
-- iterative resolver SHOULD periodically check the performance of
-- all of a zone's name servers to adjust its determination of the
-- best-performing one.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--3. Acknowledgments
--
-- The authors would like to thank the following people for their
-- comments that improved this document: Andras Salamon, Dave Meyer,
-- Doug Barton, Jaap Akkerhuis, Jinmei Tatuya, John Brady, Kevin Darcy,
-- Olafur Gudmundsson, Pekka Savola, Peter Koch and Rob Austein. We
-- apologize if we have omitted anyone; any oversight was unintentional.
--
--
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--4. IANA considerations
--
-- There are no new IANA considerations introduced by this memo.
--
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--5. Security considerations
--
-- The iterative resolver misbehavior discussed in this document exposes
-- the root and TLD name servers to increased risk of both intentional
-- and unintentional denial of service attacks.
--
-- We believe that implementation of the recommendations offered in this
-- document will reduce the amount of unnecessary traffic seen at root
-- and TLD name servers, thus reducing the opportunity for an attacker
-- to use such queries to his or her advantage.
--
--
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--6. Internationalization considerations
--
-- There are no new internationalization considerations introduced by
-- this memo.
--
--7. Informative References
--
-- [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
-- [2] Mockapetris, P., "Domain names - concepts and facilities",
-- STD 13, RFC 1034, November 1987.
--
-- [3] Elz, R. and R. Bush, "Clarifications to the DNS Specification",
-- RFC 2181, July 1997.
--
-- [4] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)",
-- RFC 2308, March 1998.
--
-- [5] Morishita, Y. and T. Jinmei, "Common Misbehavior Against DNS
-- Queries for IPv6 Addresses", RFC 4074, May 2005.
--
-- [6] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, "Dynamic
-- Updates in the Domain Name System (DNS UPDATE)", RFC 2136,
-- April 1997.
--
-- [7] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E.
-- Lear, "Address Allocation for Private Internets", BCP 5,
-- RFC 1918, February 1996.
--
-- [8] <http://www.as112.net>
--
--
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--
--Authors' Addresses
--
-- Matt Larson
-- VeriSign, Inc.
-- 21345 Ridgetop Circle
-- Dulles, VA 20166-6503
-- USA
--
-- Email: mlarson@verisign.com
--
--
-- Piet Barber
-- VeriSign, Inc.
-- 21345 Ridgetop Circle
-- Dulles, VA 20166-6503
-- USA
--
-- Email: pbarber@verisign.com
--
--
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--
--
--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
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--
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
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--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
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--
--
--
--
--
--
-- DNSOP Working Group Paul Vixie, ISC
-- INTERNET-DRAFT Akira Kato, WIDE
-- <draft-ietf-dnsop-respsize-06.txt> August 2006
--
-- DNS Referral Response Size Issues
--
-- Status of this Memo
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- Copyright Notice
--
-- Copyright (C) The Internet Society (2006). All Rights Reserved.
--
--
--
--
-- Abstract
--
-- With a mandated default minimum maximum message size of 512 octets,
-- the DNS protocol presents some special problems for zones wishing to
-- expose a moderate or high number of authority servers (NS RRs). This
-- document explains the operational issues caused by, or related to
-- this response size limit, and suggests ways to optimize the use of
-- this limited space. Guidance is offered to DNS server implementors
-- and to DNS zone operators.
--
--
--
--
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--
--
-- 1 - Introduction and Overview
--
-- 1.1. The DNS standard (see [RFC1035 4.2.1]) limits message size to 512
-- octets. Even though this limitation was due to the required minimum IP
-- reassembly limit for IPv4, it became a hard DNS protocol limit and is
-- not implicitly relaxed by changes in transport, for example to IPv6.
--
-- 1.2. The EDNS0 protocol extension (see [RFC2671 2.3, 4.5]) permits
-- larger responses by mutual agreement of the requester and responder.
-- The 512 octet message size limit will remain in practical effect until
-- there is widespread deployment of EDNS0 in DNS resolvers on the
-- Internet.
--
-- 1.3. Since DNS responses include a copy of the request, the space
-- available for response data is somewhat less than the full 512 octets.
-- Negative responses are quite small, but for positive and delegation
-- responses, every octet must be carefully and sparingly allocated. This
-- document specifically addresses delegation response sizes.
--
-- 2 - Delegation Details
--
-- 2.1. RELEVANT PROTOCOL ELEMENTS
--
-- 2.1.1. A delegation response will include the following elements:
--
-- Header Section: fixed length (12 octets)
-- Question Section: original query (name, class, type)
-- Answer Section: empty, or a CNAME/DNAME chain
-- Authority Section: NS RRset (nameserver names)
-- Additional Section: A and AAAA RRsets (nameserver addresses)
--
-- 2.1.2. If the total response size exceeds 512 octets, and if the data
-- that does not fit was "required", then the TC bit will be set
-- (indicating truncation). This will usually cause the requester to retry
-- using TCP, depending on what information was desired and what
-- information was omitted. For example, truncation in the authority
-- section is of no interest to a stub resolver who only plans to consume
-- the answer section. If a retry using TCP is needed, the total cost of
-- the transaction is much higher. See [RFC1123 6.1.3.2] for details on
-- the requirement that UDP be attempted before falling back to TCP.
--
-- 2.1.3. RRsets are never sent partially unless TC bit set to indicate
-- truncation. When TC bit is set, the final apparent RRset in the final
-- non-empty section must be considered "possibly damaged" (see [RFC1035
-- 6.2], [RFC2181 9]).
--
--
--
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--
--
-- 2.1.4. With or without truncation, the glue present in the additional
-- data section should be considered "possibly incomplete", and requesters
-- should be prepared to re-query for any damaged or missing RRsets. Note
-- that truncation of the additional data section might not be signalled
-- via the TC bit since additional data is often optional (see discussion
-- in [RFC4472 B]).
--
-- 2.1.5. DNS label compression allows a domain name to be instantiated
-- only once per DNS message, and then referenced with a two-octet
-- "pointer" from other locations in that same DNS message (see [RFC1035
-- 4.1.4]). If all nameserver names in a message share a common parent
-- (for example, all ending in ".ROOT-SERVERS.NET"), then more space will
-- be available for incompressable data (such as nameserver addresses).
--
-- 2.1.6. The query name can be as long as 255 octets of network data. In
-- this worst case scenario, the question section will be 259 octets in
-- size, which would leave only 240 octets for the authority and additional
-- sections (after deducting 12 octets for the fixed length header.)
--
-- 2.2. ADVICE TO ZONE OWNERS
--
-- 2.2.1. Average and maximum question section sizes can be predicted by
-- the zone owner, since they will know what names actually exist, and can
-- measure which ones are queried for most often. Note that if the zone
-- contains any wildcards, it is possible for maximum length queries to
-- require positive responses, but that it is reasonable to expect
-- truncation and TCP retry in that case. For cost and performance
-- reasons, the majority of requests should be satisfied without truncation
-- or TCP retry.
--
-- 2.2.2. Some queries to non-existing names can be large, but this is not
-- a problem because negative responses need not contain any answer,
-- authority or additional records. See [RFC2308 2.1] for more information
-- about the format of negative responses.
--
-- 2.2.3. The minimum useful number of name servers is two, for redundancy
-- (see [RFC1034 4.1]). A zone's name servers should be reachable by all
-- IP transport protocols (e.g., IPv4 and IPv6) in common use.
--
-- 2.2.4. The best case is no truncation at all. This is because many
-- requesters will retry using TCP immediately, or will automatically re-
-- query for RRsets that are possibly truncated, without considering
-- whether the omitted data was actually necessary.
--
--
--
--
--
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--
--
-- 2.3. ADVICE TO SERVER IMPLEMENTORS
--
-- 2.3.1. In case of multi-homed name servers, it is advantageous to
-- include an address record from each of several name servers before
-- including several address records for any one name server. If address
-- records for more than one transport (for example, A and AAAA) are
-- available, then it is advantageous to include records of both types
-- early on, before the message is full.
--
-- 2.3.2. Each added NS RR for a zone will add 12 fixed octets (name, type,
-- class, ttl, and rdlen) plus 2 to 255 variable octets (for the NSDNAME).
-- Each A RR will require 16 octets, and each AAAA RR will require 28
-- octets.
--
-- 2.3.3. While DNS distinguishes between necessary and optional resource
-- records, this distinction is according to protocol elements necessary to
-- signify facts, and takes no official notice of protocol content
-- necessary to ensure correct operation. For example, a nameserver name
-- that is in or below the zone cut being described by a delegation is
-- "necessary content," since there is no way to reach that zone unless the
-- parent zone's delegation includes "glue records" describing that name
-- server's addresses.
--
-- 2.3.4. It is also necessary to distinguish between "explicit truncation"
-- where a message could not contain enough records to convey its intended
-- meaning, and so the TC bit has been set, and "silent truncation", where
-- the message was not large enough to contain some records which were "not
-- required", and so the TC bit was not set.
--
-- 2.3.5. A delegation response should prioritize glue records as follows.
--
-- first
-- All glue RRsets for one name server whose name is in or below the
-- zone being delegated, or which has multiple address RRsets (currently
-- A and AAAA), or preferably both;
--
-- second
-- Alternate between adding all glue RRsets for any name servers whose
-- names are in or below the zone being delegated, and all glue RRsets
-- for any name servers who have multiple address RRsets (currently A
-- and AAAA);
--
-- thence
-- All other glue RRsets, in any order.
--
--
--
--
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--
--
-- Whenever there are multiple candidates for a position in this priority
-- scheme, one should be chosen on a round-robin or fully random basis.
--
-- The goal of this priority scheme is to offer "necessary" glue first,
-- avoiding silent truncation for this glue if possible.
--
-- 2.3.6. If any "necessary content" is silently truncated, then it is
-- advisable that the TC bit be set in order to force a TCP retry, rather
-- than have the zone be unreachable. Note that a parent server's proper
-- response to a query for in-child glue or below-child glue is a referral
-- rather than an answer, and that this referral MUST be able to contain
-- the in-child or below-child glue, and that in outlying cases, only EDNS
-- or TCP will be large enough to contain that data.
--
-- 3 - Analysis
--
-- 3.1. An instrumented protocol trace of a best case delegation response
-- follows. Note that 13 servers are named, and 13 addresses are given.
-- This query was artificially designed to exactly reach the 512 octet
-- limit.
--
-- ;; flags: qr rd; QUERY: 1, ANS: 0, AUTH: 13, ADDIT: 13
-- ;; QUERY SECTION:
-- ;; [23456789.123456789.123456789.\
-- 123456789.123456789.123456789.com A IN] ;; @80
--
-- ;; AUTHORITY SECTION:
-- com. 86400 NS E.GTLD-SERVERS.NET. ;; @112
-- com. 86400 NS F.GTLD-SERVERS.NET. ;; @128
-- com. 86400 NS G.GTLD-SERVERS.NET. ;; @144
-- com. 86400 NS H.GTLD-SERVERS.NET. ;; @160
-- com. 86400 NS I.GTLD-SERVERS.NET. ;; @176
-- com. 86400 NS J.GTLD-SERVERS.NET. ;; @192
-- com. 86400 NS K.GTLD-SERVERS.NET. ;; @208
-- com. 86400 NS L.GTLD-SERVERS.NET. ;; @224
-- com. 86400 NS M.GTLD-SERVERS.NET. ;; @240
-- com. 86400 NS A.GTLD-SERVERS.NET. ;; @256
-- com. 86400 NS B.GTLD-SERVERS.NET. ;; @272
-- com. 86400 NS C.GTLD-SERVERS.NET. ;; @288
-- com. 86400 NS D.GTLD-SERVERS.NET. ;; @304
--
--
--
--
--
--
--
--
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--
--
-- ;; ADDITIONAL SECTION:
-- A.GTLD-SERVERS.NET. 86400 A 192.5.6.30 ;; @320
-- B.GTLD-SERVERS.NET. 86400 A 192.33.14.30 ;; @336
-- C.GTLD-SERVERS.NET. 86400 A 192.26.92.30 ;; @352
-- D.GTLD-SERVERS.NET. 86400 A 192.31.80.30 ;; @368
-- E.GTLD-SERVERS.NET. 86400 A 192.12.94.30 ;; @384
-- F.GTLD-SERVERS.NET. 86400 A 192.35.51.30 ;; @400
-- G.GTLD-SERVERS.NET. 86400 A 192.42.93.30 ;; @416
-- H.GTLD-SERVERS.NET. 86400 A 192.54.112.30 ;; @432
-- I.GTLD-SERVERS.NET. 86400 A 192.43.172.30 ;; @448
-- J.GTLD-SERVERS.NET. 86400 A 192.48.79.30 ;; @464
-- K.GTLD-SERVERS.NET. 86400 A 192.52.178.30 ;; @480
-- L.GTLD-SERVERS.NET. 86400 A 192.41.162.30 ;; @496
-- M.GTLD-SERVERS.NET. 86400 A 192.55.83.30 ;; @512
--
-- ;; MSG SIZE sent: 80 rcvd: 512
--
-- 3.2. For longer query names, the number of address records supplied will
-- be lower. Furthermore, it is only by using a common parent name (which
-- is GTLD-SERVERS.NET in this example) that all 13 addresses are able to
-- fit, due to the use of DNS compression pointers in the last 12
-- occurances of the parent domain name. The following output from a
-- response simulator demonstrates these properties.
--
-- % perl respsize.pl a.dns.br b.dns.br c.dns.br d.dns.br
-- a.dns.br requires 10 bytes
-- b.dns.br requires 4 bytes
-- c.dns.br requires 4 bytes
-- d.dns.br requires 4 bytes
-- # of NS: 4
-- For maximum size query (255 byte):
-- only A is considered: # of A is 4 (green)
-- A and AAAA are considered: # of A+AAAA is 3 (yellow)
-- preferred-glue A is assumed: # of A is 4, # of AAAA is 3 (yellow)
-- For average size query (64 byte):
-- only A is considered: # of A is 4 (green)
-- A and AAAA are considered: # of A+AAAA is 4 (green)
-- preferred-glue A is assumed: # of A is 4, # of AAAA is 4 (green)
--
--
--
--
--
--
--
--
--
--
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--
--
-- % perl respsize.pl ns-ext.isc.org ns.psg.com ns.ripe.net ns.eu.int
-- ns-ext.isc.org requires 16 bytes
-- ns.psg.com requires 12 bytes
-- ns.ripe.net requires 13 bytes
-- ns.eu.int requires 11 bytes
-- # of NS: 4
-- For maximum size query (255 byte):
-- only A is considered: # of A is 4 (green)
-- A and AAAA are considered: # of A+AAAA is 3 (yellow)
-- preferred-glue A is assumed: # of A is 4, # of AAAA is 2 (yellow)
-- For average size query (64 byte):
-- only A is considered: # of A is 4 (green)
-- A and AAAA are considered: # of A+AAAA is 4 (green)
-- preferred-glue A is assumed: # of A is 4, # of AAAA is 4 (green)
--
-- (Note: The response simulator program is shown in Section 5.)
--
-- Here we use the term "green" if all address records could fit, or
-- "yellow" if two or more could fit, or "orange" if only one could fit, or
-- "red" if no address record could fit. It's clear that without a common
-- parent for nameserver names, much space would be lost. For these
-- examples we use an average/common name size of 15 octets, befitting our
-- assumption of GTLD-SERVERS.NET as our common parent name.
--
-- We're assuming a medium query name size of 64 since that is the typical
-- size seen in trace data at the time of this writing. If
-- Internationalized Domain Name (IDN) or any other technology which
-- results in larger query names be deployed significantly in advance of
-- EDNS, then new measurements and new estimates will have to be made.
--
-- 4 - Conclusions
--
-- 4.1. The current practice of giving all nameserver names a common parent
-- (such as GTLD-SERVERS.NET or ROOT-SERVERS.NET) saves space in DNS
-- responses and allows for more nameservers to be enumerated than would
-- otherwise be possible, since the common parent domain name only appears
-- once in a DNS message and is referred to via "compression pointers"
-- thereafter.
--
-- 4.2. If all nameserver names for a zone share a common parent, then it
-- is operationally advisable to make all servers for the zone thus served
-- also be authoritative for the zone of that common parent. For example,
-- the root name servers (?.ROOT-SERVERS.NET) can answer authoritatively
-- for the ROOT-SERVERS.NET. This is to ensure that the zone's servers
-- always have the zone's nameservers' glue available when delegating, and
--
--
--
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--
--
-- will be able to respond with answers rather than referrals if a
-- requester who wants that glue comes back asking for it. In this case
-- the name server will likely be a "stealth server" -- authoritative but
-- unadvertised in the glue zone's NS RRset. See [RFC1996 2] for more
-- information about stealth servers.
--
-- 4.3. Thirteen (13) is the effective maximum number of nameserver names
-- usable traditional (non-extended) DNS, assuming a common parent domain
-- name, and given that implicit referral response truncation is
-- undesirable in the average case.
--
-- 4.4. Multi-homing of name servers within a protocol family is
-- inadvisable since the necessary glue RRsets (A or AAAA) are atomically
-- indivisible, and will be larger than a single resource record. Larger
-- RRsets are more likely to lead to or encounter truncation.
--
-- 4.5. Multi-homing of name servers across protocol families is less
-- likely to lead to or encounter truncation, partly because multiprotocol
-- clients are more likely to speak EDNS which can use a larger response
-- size limit, and partly because the resource records (A and AAAA) are in
-- different RRsets and are therefore divisible from each other.
--
-- 4.6. Name server names which are at or below the zone they serve are
-- more sensitive to referral response truncation, and glue records for
-- them should be considered "less optional" than other glue records, in
-- the assembly of referral responses.
--
-- 4.7. If a zone is served by thirteen (13) name servers having a common
-- parent name (such as ?.ROOT-SERVERS.NET) and each such name server has a
-- single address record in some protocol family (e.g., an A RR), then all
-- thirteen name servers or any subset thereof could multi-home in a second
-- protocol family by adding a second address record (e.g., an AAAA RR)
-- without reducing the reachability of the zone thus served.
--
-- 5 - Source Code
--
-- #!/usr/bin/perl
-- #
-- # SYNOPSIS
-- # repsize.pl [ -z zone ] fqdn_ns1 fqdn_ns2 ...
-- # if all queries are assumed to have a same zone suffix,
-- # such as "jp" in JP TLD servers, specify it in -z option
-- #
-- use strict;
-- use Getopt::Std;
--
--
--
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--
--
-- my ($sz_msg) = (512);
-- my ($sz_header, $sz_ptr, $sz_rr_a, $sz_rr_aaaa) = (12, 2, 16, 28);
-- my ($sz_type, $sz_class, $sz_ttl, $sz_rdlen) = (2, 2, 4, 2);
-- my (%namedb, $name, $nssect, %opts, $optz);
-- my $n_ns = 0;
--
-- getopt('z', %opts);
-- if (defined($opts{'z'})) {
-- server_name_len($opts{'z'}); # just register it
-- }
--
-- foreach $name (@ARGV) {
-- my $len;
-- $n_ns++;
-- $len = server_name_len($name);
-- print "$name requires $len bytes\n";
-- $nssect += $sz_ptr + $sz_type + $sz_class + $sz_ttl
-- + $sz_rdlen + $len;
-- }
-- print "# of NS: $n_ns\n";
-- arsect(255, $nssect, $n_ns, "maximum");
-- arsect(64, $nssect, $n_ns, "average");
--
-- sub server_name_len {
-- my ($name) = @_;
-- my (@labels, $len, $n, $suffix);
--
-- $name =~ tr/A-Z/a-z/;
-- @labels = split(/\./, $name);
-- $len = length(join('.', @labels)) + 2;
-- for ($n = 0; $#labels >= 0; $n++, shift @labels) {
-- $suffix = join('.', @labels);
-- return length($name) - length($suffix) + $sz_ptr
-- if (defined($namedb{$suffix}));
-- $namedb{$suffix} = 1;
-- }
-- return $len;
-- }
--
-- sub arsect {
-- my ($sz_query, $nssect, $n_ns, $cond) = @_;
-- my ($space, $n_a, $n_a_aaaa, $n_p_aaaa, $ansect);
-- $ansect = $sz_query + 1 + $sz_type + $sz_class;
-- $space = $sz_msg - $sz_header - $ansect - $nssect;
-- $n_a = atmost(int($space / $sz_rr_a), $n_ns);
--
--
--
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--
--
-- $n_a_aaaa = atmost(int($space
-- / ($sz_rr_a + $sz_rr_aaaa)), $n_ns);
-- $n_p_aaaa = atmost(int(($space - $sz_rr_a * $n_ns)
-- / $sz_rr_aaaa), $n_ns);
-- printf "For %s size query (%d byte):\n", $cond, $sz_query;
-- printf " only A is considered: ";
-- printf "# of A is %d (%s)\n", $n_a, &judge($n_a, $n_ns);
-- printf " A and AAAA are considered: ";
-- printf "# of A+AAAA is %d (%s)\n",
-- $n_a_aaaa, &judge($n_a_aaaa, $n_ns);
-- printf " preferred-glue A is assumed: ";
-- printf "# of A is %d, # of AAAA is %d (%s)\n",
-- $n_a, $n_p_aaaa, &judge($n_p_aaaa, $n_ns);
-- }
--
-- sub judge {
-- my ($n, $n_ns) = @_;
-- return "green" if ($n >= $n_ns);
-- return "yellow" if ($n >= 2);
-- return "orange" if ($n == 1);
-- return "red";
-- }
--
-- sub atmost {
-- my ($a, $b) = @_;
-- return 0 if ($a < 0);
-- return $b if ($a > $b);
-- return $a;
-- }
--
-- 6 - Security Considerations
--
-- The recommendations contained in this document have no known security
-- implications.
--
-- 7 - IANA Considerations
--
-- This document does not call for changes or additions to any IANA
-- registry.
--
-- 8 - Acknowledgement
--
-- The authors thank Peter Koch, Rob Austein, Joe Abley, and Mark Andrews
-- for their valuable comments and suggestions.
--
--
--
--
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--
--
-- This work was supported by the US National Science Foundation (research
-- grant SCI-0427144) and DNS-OARC.
--
-- 9 - References
--
-- [RFC1034] Mockapetris, P.V., "Domain names - Concepts and Facilities",
-- RFC1034, November 1987.
--
-- [RFC1035] Mockapetris, P.V., "Domain names - Implementation and
-- Specification", RFC1035, November 1987.
--
-- [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
-- Application and Support", RFC1123, October 1989.
--
-- [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
-- Changes (DNS NOTIFY)", RFC1996, August 1996.
--
-- [RFC2181] Elz, R., Bush, R., "Clarifications to the DNS Specification",
-- RFC2181, July 1997.
--
-- [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)",
-- RFC2308, March 1998.
--
-- [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC2671,
-- August 1999.
--
-- [RFC4472] Durand, A., Ihren, J., Savola, P., "Operational Consideration
-- and Issues with IPV6 DNS", April 2006.
--
-- 10 - Authors' Addresses
--
-- Paul Vixie
-- Internet Systems Consortium, Inc.
-- 950 Charter Street
-- Redwood City, CA 94063
-- +1 650 423 1301
-- vixie@isc.org
--
-- Akira Kato
-- University of Tokyo, Information Technology Center
-- 2-11-16 Yayoi Bunkyo
-- Tokyo 113-8658, JAPAN
-- +81 3 5841 2750
-- kato@wide.ad.jp
--
--
--
--
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--
--
-- Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors retain
-- all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR
-- IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
-- Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in this
-- document or the extent to which any license under such rights might or
-- might not be available; nor does it represent that it has made any
-- independent effort to identify any such rights. Information on the
-- procedures with respect to rights in RFC documents can be found in BCP
-- 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an attempt
-- made to obtain a general license or permission for the use of such
-- proprietary rights by implementers or users of this specification can be
-- obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary rights
-- that may cover technology that may be required to implement this
-- standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
-- Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
-- Expires January 2007 [Page 12]
--\f
--
+++ /dev/null
--
--
--
--
--Network Working Group S. Woolf
--Internet-Draft Internet Systems Consortium, Inc.
--Expires: September 6, 2006 D. Conrad
-- Nominum, Inc.
-- March 5, 2006
--
--
-- Requirements for a Mechanism Identifying a Name Server Instance
-- draft-ietf-dnsop-serverid-06
--
--Status of this Memo
--
-- By submitting this Internet-Draft, each author represents that any
-- applicable patent or other IPR claims of which he or she is aware
-- have been or will be disclosed, and any of which he or she becomes
-- aware will be disclosed, in accordance with Section 6 of BCP 79.
--
-- Internet-Drafts are working documents of the Internet Engineering
-- Task Force (IETF), its areas, and its working groups. Note that
-- other groups may also distribute working documents as Internet-
-- Drafts.
--
-- Internet-Drafts are draft documents valid for a maximum of six months
-- and may be updated, replaced, or obsoleted by other documents at any
-- time. It is inappropriate to use Internet-Drafts as reference
-- material or to cite them other than as "work in progress."
--
-- The list of current Internet-Drafts can be accessed at
-- http://www.ietf.org/ietf/1id-abstracts.txt.
--
-- The list of Internet-Draft Shadow Directories can be accessed at
-- http://www.ietf.org/shadow.html.
--
-- This Internet-Draft will expire on September 6, 2006.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- With the increased use of DNS anycast, load balancing, and other
-- mechanisms allowing more than one DNS name server to share a single
-- IP address, it is sometimes difficult to tell which of a pool of name
-- servers has answered a particular query. A standardized mechanism to
-- determine the identity of a name server responding to a particular
-- query would be useful, particularly as a diagnostic aid for
-- administrators. Existing ad hoc mechanisms for addressing this need
--
--
--
--Woolf & Conrad Expires September 6, 2006 [Page 1]
--\f
--Internet-Draft Serverid March 2006
--
--
-- have some shortcomings, not the least of which is the lack of prior
-- analysis of exactly how such a mechanism should be designed and
-- deployed. This document describes the existing convention used in
-- some widely deployed implementations of the DNS protocol, including
-- advantages and disadvantages, and discusses some attributes of an
-- improved mechanism.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Woolf & Conrad Expires September 6, 2006 [Page 2]
--\f
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--
--
--1. Introduction and Rationale
--
-- Identifying which name server is responding to queries is often
-- useful, particularly in attempting to diagnose name server
-- difficulties. This is most obviously useful for authoritative
-- nameservers in the attempt to diagnose the source or prevalence of
-- inaccurate data, but can also conceivably be useful for caching
-- resolvers in similar and other situations. Furthermore, the ability
-- to identify which server is responding to a query has become more
-- useful as DNS has become more critical to more Internet users, and as
-- network and server deployment topologies have become more complex.
--
-- The traditional means for determining which of several possible
-- servers is answering a query has traditionally been based on the use
-- of the server's IP address as a unique identifier. However, the
-- modern Internet has seen the deployment of various load balancing,
-- fault-tolerance, or attack-resistance schemes such as shared use of
-- unicast IP addresses as documented in [RFC3258]. An unfortunate side
-- effect of these schemes has been to make the use of IP addresses as
-- identifiers somewhat problematic. Specifically, a dedicated DNS
-- query may not go to the same server as answered a previous query,
-- even though sent to the same IP address. Non-DNS methods such as
-- ICMP ping, TCP connections, or non-DNS UDP packets (such as those
-- generated by tools like "traceroute"), etc., may well be even less
-- certain to reach the same server as the one which receives the DNS
-- queries.
--
-- There is a well-known and frequently-used technique for determining
-- an identity for a nameserver more specific than the possibly-non-
-- unique "server that answered the query I sent to IP address XXX".
-- The widespread use of the existing convention suggests a need for a
-- documented, interoperable means of querying the identity of a
-- nameserver that may be part of an anycast or load-balancing cluster.
-- At the same time, however, it also has some drawbacks that argue
-- against standardizing it as it's been practiced so far.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
--
--2. Existing Conventions
--
-- For some time, the commonly deployed Berkeley Internet Name Domain
-- implementation of the DNS protocol suite from the Internet Systems
-- Consortium [BIND] has supported a way of identifying a particular
-- server via the use of a standards-compliant, if somewhat unusual, DNS
-- query. Specifically, a query to a recent BIND server for a TXT
-- resource record in class 3 (CHAOS) for the domain name
-- "HOSTNAME.BIND." will return a string that can be configured by the
-- name server administrator to provide a unique identifier for the
-- responding server. (The value defaults to the result of a
-- gethostname() call). This mechanism, which is an extension of the
-- BIND convention of using CHAOS class TXT RR queries to sub-domains of
-- the "BIND." domain for version information, has been copied by
-- several name server vendors.
--
-- A refinement to the BIND-based mechanism, which dropped the
-- implementation-specific string, replaces ".BIND" with ".SERVER".
-- Thus the query string to learn the unique name of a server may be
-- queried as "ID.SERVER".
--
-- (For reference, the other well-known name used by recent versions of
-- BIND within the CHAOS class "BIND." domain is "VERSION.BIND." A
-- query for a CHAOS TXT RR for this name will return an
-- administratively defined string which defaults to the version of the
-- server responding. This is, however, not generally implemented by
-- other vendors.)
--
--2.1. Advantages
--
-- There are several valuable attributes to this mechanism, which
-- account for its usefulness.
--
-- 1. The "HOSTNAME.BIND" or "ID.SERVER" query response mechanism is
-- within the DNS protocol itself. An identification mechanism that
-- relies on the DNS protocol is more likely to be successful
-- (although not guaranteed) in going to the same system as a
-- "normal" DNS query.
--
-- 2. Since the identity information is requested and returned within
-- the DNS protocol, it doesn't require allowing any other query
-- mechanism to the server, such as holes in firewalls for
-- otherwise-unallowed ICMP Echo requests. Thus it is likely to
-- reach the same server over a path subject to the same routing,
-- resource, and security policy as the query, without any special
-- exceptions to site security policy.
--
--
--
--
--
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--
--
-- 3. It is simple to configure. An administrator can easily turn on
-- this feature and control the results of the relevant query.
--
-- 4. It allows the administrator complete control of what information
-- is given out in the response, minimizing passive leakage of
-- implementation or configuration details. Such details are often
-- considered sensitive by infrastructure operators.
--
-- 5. Hypothetically, since it's an ordinary DNS record and the
-- relevant DNSSEC RRs are class independent, the id.server response
-- RR could be signed, which has the advantages described in
-- [RFC4033].
--
--2.2. Disadvantages
--
-- At the same time, there are some serious drawbacks to the CHAOS/TXT
-- query mechanism that argue against standardizing it as it currently
-- operates.
--
-- 1. It requires an additional query to correlate between the answer
-- to a DNS query under normal conditions and the supposed identity
-- of the server receiving the query. There are a number of
-- situations in which this simply isn't reliable.
--
-- 2. It reserves an entire class in the DNS (CHAOS) for what amounts
-- to one zone. While CHAOS class is defined in [RFC1034] and
-- [RFC1035], it's not clear that supporting it solely for this
-- purpose is a good use of the namespace or of implementation
-- effort.
--
-- 3. The initial and still common form, using .BIND, is implementation
-- specific. BIND is one DNS implementation. At the time of this
-- writing, it is probably the most prevalent for authoritative
-- servers. This does not justify standardizing on its ad hoc
-- solution to a problem shared across many operators and
-- implementors. Meanwhile, the proposed refinement changes the
-- string but preserves the ad hoc CHAOS/TXT mechanism.
--
-- 4. There is no convention or shared understanding of what
-- information an answer to such a query for a server identity could
-- or should include, including a possible encoding or
-- authentication mechanism.
--
-- The first of the listed disadvantages may be technically the most
-- serious. It argues for an attempt to design a good answer to the
-- problem that "I need to know what nameserver is answering my
-- queries", not simply a convenient one.
--
--
--
--
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--
--
--2.3. Characteristics of an Implementation Neutral Convention
--
-- The discussion above of advantages and disadvantages to the
-- HOSTNAME.BIND mechanism suggest some requirements for a better
-- solution to the server identification problem. These are summarized
-- here as guidelines for any effort to provide appropriate protocol
-- extensions:
--
-- 1. The mechanism adopted must be in-band for the DNS protocol. That
-- is, it needs to allow the query for the server's identifying
-- information to be part of a normal, operational query. It should
-- also permit a separate, dedicated query for the server's
-- identifying information. But it should preserve the ability of
-- the CHAOS/TXT query-based mechanism to work through firewalls and
-- in other situations where only DNS can be relied upon to reach
-- the server of interest.
--
-- 2. The new mechanism should not require dedicated namespaces or
-- other reserved values outside of the existing protocol mechanisms
-- for these, i.e. the OPT pseudo-RR. In particular, it should not
-- propagate the existing drawback of requiring support for a CLASS
-- and top level domain in the authoritative server (or the querying
-- tool) to be useful.
--
-- 3. Support for the identification functionality should be easy to
-- implement and easy to enable. It must be easy to disable and
-- should lend itself to access controls on who can query for it.
--
-- 4. It should be possible to return a unique identifier for a server
-- without requiring the exposure of information that may be non-
-- public and considered sensitive by the operator, such as a
-- hostname or unicast IP address maintained for administrative
-- purposes.
--
-- 5. It should be possible to authenticate the received data by some
-- mechanism analogous to those provided by DNSSEC. In this
-- context, the need could be met by including encryption options in
-- the specification of a new mechanism.
--
-- 6. The identification mechanism should not be implementation-
-- specific.
--
--
--
--
--
--
--
--
--
--
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--
--
--3. IANA Considerations
--
-- This document proposes no specific IANA action. Protocol extensions,
-- if any, to meet the requirements described are out of scope for this
-- document. A proposed extension, specified and adopted by normal IETF
-- process, is described in [NSID], including relevant IANA action.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
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--
--
--
--
--
--
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--
--
--4. Security Considerations
--
-- Providing identifying information as to which server is responding to
-- a particular query from a particular location in the Internet can be
-- seen as information leakage and thus a security risk. This motivates
-- the suggestion above that a new mechanism for server identification
-- allow the administrator to disable the functionality altogether or
-- partially restrict availability of the data. It also suggests that
-- the serverid data should not be readily correlated with a hostname or
-- unicast IP address that may be considered private to the nameserver
-- operator's management infrastructure.
--
-- Propagation of protocol or service meta-data can sometimes expose the
-- application to denial of service or other attack. As DNS is a
-- critically important infrastructure service for the production
-- Internet, extra care needs to be taken against this risk for
-- designers, implementors, and operators of a new mechanism for server
-- identification.
--
-- Both authentication and confidentiality of serverid data are
-- potentially of interest to administrators-- that is, operators may
-- wish to make serverid data available and reliable to themselves and
-- their chosen associates only. This would imply both an ability to
-- authenticate it to themselves and keep it private from arbitrary
-- other parties. This led to Characteristics 4 and 5 of an improved
-- solution.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
--
--5. Acknowledgements
--
-- The technique for host identification documented here was initially
-- implemented by Paul Vixie of the Internet Software Consortium in the
-- Berkeley Internet Name Daemon package. Comments and questions on
-- earlier drafts were provided by Bob Halley, Brian Wellington, Andreas
-- Gustafsson, Ted Hardie, Chris Yarnell, Randy Bush, and members of the
-- ICANN Root Server System Advisory Committee. The newest version
-- takes a significantly different direction from previous versions,
-- owing to discussion among contributors to the DNSOP working group and
-- others, particularly Olafur Gudmundsson, Ed Lewis, Bill Manning, Sam
-- Weiler, and Rob Austein.
--
--6. References
--
-- [1] Mockapetris, P., "Domain Names - Concepts and Facilities",
-- RFC 1034, STD 0013, November 1987.
--
-- [2] Mockapetris, P., "Domain Names - Implementation and
-- Specification", RFC 1035, STD 0013, November 1987.
--
-- [3] Hardie, T., "Distributing Authoritative Name Servers via Shared
-- Unicast Addresses", RFC 3258, April 2002.
--
-- [4] ISC, "BIND 9 Configuration Reference".
--
-- [5] Austein, S., "DNS Name Server Identifier Option (NSID)",
-- Internet Drafts http://www.ietf.org/internet-drafts/
-- draft-ietf-dnsext-nsid-01.txt, January 2006.
--
-- [6] Arends, R., Austein, S., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033,
-- March 2005.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
--
--Authors' Addresses
--
-- Suzanne Woolf
-- Internet Systems Consortium, Inc.
-- 950 Charter Street
-- Redwood City, CA 94063
-- US
--
-- Phone: +1 650 423-1333
-- Email: woolf@isc.org
-- URI: http://www.isc.org/
--
--
-- David Conrad
-- Nominum, Inc.
-- 2385 Bay Road
-- Redwood City, CA 94063
-- US
--
-- Phone: +1 1 650 381 6003
-- Email: david.conrad@nominum.com
-- URI: http://www.nominum.com/
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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--
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--
--
--
--
--
--
--
--
--
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--
--
--Intellectual Property Statement
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--
--Disclaimer of Validity
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--
--Copyright Statement
--
-- Copyright (C) The Internet Society (2006). This document is subject
-- to the rights, licenses and restrictions contained in BCP 78, and
-- except as set forth therein, the authors retain all their rights.
--
--
--Acknowledgment
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
--Woolf & Conrad Expires September 6, 2006 [Page 11]
--\f
--
+++ /dev/null
--
--
--
--
--
--
--Network Working Group R. Hinden
--Request for Comments: 4193 Nokia
--Category: Standards Track B. Haberman
-- JHU-APL
-- October 2005
--
--
-- Unique Local IPv6 Unicast Addresses
--
--Status of This Memo
--
-- This document specifies an Internet standards track protocol for the
-- Internet community, and requests discussion and suggestions for
-- improvements. Please refer to the current edition of the "Internet
-- Official Protocol Standards" (STD 1) for the standardization state
-- and status of this protocol. Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2005).
--
--Abstract
--
-- This document defines an IPv6 unicast address format that is globally
-- unique and is intended for local communications, usually inside of a
-- site. These addresses are not expected to be routable on the global
-- Internet.
--
--Table of Contents
--
-- 1. Introduction ....................................................2
-- 2. Acknowledgements ................................................3
-- 3. Local IPv6 Unicast Addresses ....................................3
-- 3.1. Format .....................................................3
-- 3.1.1. Background ..........................................4
-- 3.2. Global ID ..................................................4
-- 3.2.1. Locally Assigned Global IDs .........................5
-- 3.2.2. Sample Code for Pseudo-Random Global ID Algorithm ...5
-- 3.2.3. Analysis of the Uniqueness of Global IDs ............6
-- 3.3. Scope Definition ...........................................6
-- 4. Operational Guidelines ..........................................7
-- 4.1. Routing ....................................................7
-- 4.2. Renumbering and Site Merging ...............................7
-- 4.3. Site Border Router and Firewall Packet Filtering ...........8
-- 4.4. DNS Issues .................................................8
-- 4.5. Application and Higher Level Protocol Issues ...............9
-- 4.6. Use of Local IPv6 Addresses for Local Communication ........9
-- 4.7. Use of Local IPv6 Addresses with VPNs .....................10
--
--
--
--Hinden & Haberman Standards Track [Page 1]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- 5. Global Routing Considerations ..................................11
-- 5.1. From the Standpoint of the Internet .......................11
-- 5.2. From the Standpoint of a Site .............................11
-- 6. Advantages and Disadvantages ...................................12
-- 6.1. Advantages ................................................12
-- 6.2. Disadvantages .............................................13
-- 7. Security Considerations ........................................13
-- 8. IANA Considerations ............................................13
-- 9. References .....................................................13
-- 9.1. Normative References ......................................13
-- 9.2. Informative References ....................................14
--
--1. Introduction
--
-- This document defines an IPv6 unicast address format that is globally
-- unique and is intended for local communications [IPV6]. These
-- addresses are called Unique Local IPv6 Unicast Addresses and are
-- abbreviated in this document as Local IPv6 addresses. They are not
-- expected to be routable on the global Internet. They are routable
-- inside of a more limited area such as a site. They may also be
-- routed between a limited set of sites.
--
-- Local IPv6 unicast addresses have the following characteristics:
--
-- - Globally unique prefix (with high probability of uniqueness).
--
-- - Well-known prefix to allow for easy filtering at site
-- boundaries.
--
-- - Allow sites to be combined or privately interconnected without
-- creating any address conflicts or requiring renumbering of
-- interfaces that use these prefixes.
--
-- - Internet Service Provider independent and can be used for
-- communications inside of a site without having any permanent or
-- intermittent Internet connectivity.
--
-- - If accidentally leaked outside of a site via routing or DNS,
-- there is no conflict with any other addresses.
--
-- - In practice, applications may treat these addresses like global
-- scoped addresses.
--
-- This document defines the format of Local IPv6 addresses, how to
-- allocate them, and usage considerations including routing, site
-- border routers, DNS, application support, VPN usage, and guidelines
-- for how to use for local communication inside a site.
--
--
--
--
--Hinden & Haberman Standards Track [Page 2]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [RFC2119].
--
--2. Acknowledgements
--
-- The underlying idea of creating Local IPv6 addresses described in
-- this document has been proposed a number of times by a variety of
-- people. The authors of this document do not claim exclusive credit.
-- Credit goes to Brian Carpenter, Christian Huitema, Aidan Williams,
-- Andrew White, Charlie Perkins, and many others. The authors would
-- also like to thank Brian Carpenter, Charlie Perkins, Harald
-- Alvestrand, Keith Moore, Margaret Wasserman, Shannon Behrens, Alan
-- Beard, Hans Kruse, Geoff Huston, Pekka Savola, Christian Huitema, Tim
-- Chown, Steve Bellovin, Alex Zinin, Tony Hain, Bill Fenner, Sam
-- Hartman, and Elwyn Davies for their comments and suggestions on this
-- document.
--
--3. Local IPv6 Unicast Addresses
--
--3.1. Format
--
-- The Local IPv6 addresses are created using a pseudo-randomly
-- allocated global ID. They have the following format:
--
-- | 7 bits |1| 40 bits | 16 bits | 64 bits |
-- +--------+-+------------+-----------+----------------------------+
-- | Prefix |L| Global ID | Subnet ID | Interface ID |
-- +--------+-+------------+-----------+----------------------------+
--
-- Where:
--
-- Prefix FC00::/7 prefix to identify Local IPv6 unicast
-- addresses.
--
-- L Set to 1 if the prefix is locally assigned.
-- Set to 0 may be defined in the future. See
-- Section 3.2 for additional information.
--
-- Global ID 40-bit global identifier used to create a
-- globally unique prefix. See Section 3.2 for
-- additional information.
--
-- Subnet ID 16-bit Subnet ID is an identifier of a subnet
-- within the site.
--
-- Interface ID 64-bit Interface ID as defined in [ADDARCH].
--
--
--
--
--Hinden & Haberman Standards Track [Page 3]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--3.1.1. Background
--
-- There were a range of choices available when choosing the size of the
-- prefix and Global ID field length. There is a direct tradeoff
-- between having a Global ID field large enough to support foreseeable
-- future growth and not using too much of the IPv6 address space
-- needlessly. A reasonable way of evaluating a specific field length
-- is to compare it to a projected 2050 world population of 9.3 billion
-- [POPUL] and the number of resulting /48 prefixes per person. A range
-- of prefix choices is shown in the following table:
--
-- Prefix Global ID Number of Prefixes % of IPv6
-- Length /48 Prefixes per Person Address Space
--
-- /11 37 137,438,953,472 15 0.049%
-- /10 38 274,877,906,944 30 0.098%
-- /9 39 549,755,813,888 59 0.195%
-- /8 40 1,099,511,627,776 118 0.391%
-- /7 41 2,199,023,255,552 236 0.781%
-- /6 42 4,398,046,511,104 473 1.563%
--
-- A very high utilization ratio of these allocations can be assumed
-- because the Global ID field does not require internal structure, and
-- there is no reason to be able to aggregate the prefixes.
--
-- The authors believe that a /7 prefix resulting in a 41-bit Global ID
-- space (including the L bit) is a good choice. It provides for a
-- large number of assignments (i.e., 2.2 trillion) and at the same time
-- uses less than .8% of the total IPv6 address space. It is unlikely
-- that this space will be exhausted. If more than this were to be
-- needed, then additional IPv6 address space could be allocated for
-- this purpose.
--
--3.2. Global ID
--
-- The allocation of Global IDs is pseudo-random [RANDOM]. They MUST
-- NOT be assigned sequentially or with well-known numbers. This is to
-- ensure that there is not any relationship between allocations and to
-- help clarify that these prefixes are not intended to be routed
-- globally. Specifically, these prefixes are not designed to
-- aggregate.
--
-- This document defines a specific local method to allocate Global IDs,
-- indicated by setting the L bit to 1. Another method, indicated by
-- clearing the L bit, may be defined later. Apart from the allocation
-- method, all Local IPv6 addresses behave and are treated identically.
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 4]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- The local assignments are self-generated and do not need any central
-- coordination or assignment, but have an extremely high probability of
-- being unique.
--
--3.2.1. Locally Assigned Global IDs
--
-- Locally assigned Global IDs MUST be generated with a pseudo-random
-- algorithm consistent with [RANDOM]. Section 3.2.2 describes a
-- suggested algorithm. It is important that all sites generating
-- Global IDs use a functionally similar algorithm to ensure there is a
-- high probability of uniqueness.
--
-- The use of a pseudo-random algorithm to generate Global IDs in the
-- locally assigned prefix gives an assurance that any network numbered
-- using such a prefix is highly unlikely to have that address space
-- clash with any other network that has another locally assigned prefix
-- allocated to it. This is a particularly useful property when
-- considering a number of scenarios including networks that merge,
-- overlapping VPN address space, or hosts mobile between such networks.
--
--3.2.2. Sample Code for Pseudo-Random Global ID Algorithm
--
-- The algorithm described below is intended to be used for locally
-- assigned Global IDs. In each case the resulting global ID will be
-- used in the appropriate prefix as defined in Section 3.2.
--
-- 1) Obtain the current time of day in 64-bit NTP format [NTP].
--
-- 2) Obtain an EUI-64 identifier from the system running this
-- algorithm. If an EUI-64 does not exist, one can be created from
-- a 48-bit MAC address as specified in [ADDARCH]. If an EUI-64
-- cannot be obtained or created, a suitably unique identifier,
-- local to the node, should be used (e.g., system serial number).
--
-- 3) Concatenate the time of day with the system-specific identifier
-- in order to create a key.
--
-- 4) Compute an SHA-1 digest on the key as specified in [FIPS, SHA1];
-- the resulting value is 160 bits.
--
-- 5) Use the least significant 40 bits as the Global ID.
--
-- 6) Concatenate FC00::/7, the L bit set to 1, and the 40-bit Global
-- ID to create a Local IPv6 address prefix.
--
-- This algorithm will result in a Global ID that is reasonably unique
-- and can be used to create a locally assigned Local IPv6 address
-- prefix.
--
--
--
--Hinden & Haberman Standards Track [Page 5]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--3.2.3. Analysis of the Uniqueness of Global IDs
--
-- The selection of a pseudo random Global ID is similar to the
-- selection of an SSRC identifier in RTP/RTCP defined in Section 8.1 of
-- [RTP]. This analysis is adapted from that document.
--
-- Since Global IDs are chosen randomly (and independently), it is
-- possible that separate networks have chosen the same Global ID. For
-- any given network, with one or more random Global IDs, that has
-- inter-connections to other such networks, having a total of N such
-- IDs, the probability that two or more of these IDs will collide can
-- be approximated using the formula:
--
-- P = 1 - exp(-N**2 / 2**(L+1))
--
-- where P is the probability of collision, N is the number of
-- interconnected Global IDs, and L is the length of the Global ID.
--
-- The following table shows the probability of a collision for a range
-- of connections using a 40-bit Global ID field.
--
-- Connections Probability of Collision
--
-- 2 1.81*10^-12
-- 10 4.54*10^-11
-- 100 4.54*10^-09
-- 1000 4.54*10^-07
-- 10000 4.54*10^-05
--
-- Based on this analysis, the uniqueness of locally generated Global
-- IDs is adequate for sites planning a small to moderate amount of
-- inter-site communication using locally generated Global IDs.
--
--3.3. Scope Definition
--
-- By default, the scope of these addresses is global. That is, they
-- are not limited by ambiguity like the site-local addresses defined in
-- [ADDARCH]. Rather, these prefixes are globally unique, and as such,
-- their applicability is greater than site-local addresses. Their
-- limitation is in the routability of the prefixes, which is limited to
-- a site and any explicit routing agreements with other sites to
-- propagate them (also see Section 4.1). Also, unlike site-locals, a
-- site may have more than one of these prefixes and use them at the
-- same time.
--
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 6]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--4. Operational Guidelines
--
-- The guidelines in this section do not require any change to the
-- normal routing and forwarding functionality in an IPv6 host or
-- router. These are configuration and operational usage guidelines.
--
--4.1. Routing
--
-- Local IPv6 addresses are designed to be routed inside of a site in
-- the same manner as other types of unicast addresses. They can be
-- carried in any IPv6 routing protocol without any change.
--
-- It is expected that they would share the same Subnet IDs with
-- provider-based global unicast addresses, if they were being used
-- concurrently [GLOBAL].
--
-- The default behavior of exterior routing protocol sessions between
-- administrative routing regions must be to ignore receipt of and not
-- advertise prefixes in the FC00::/7 block. A network operator may
-- specifically configure prefixes longer than FC00::/7 for inter-site
-- communication.
--
-- If BGP is being used at the site border with an ISP, the default BGP
-- configuration must filter out any Local IPv6 address prefixes, both
-- incoming and outgoing. It must be set both to keep any Local IPv6
-- address prefixes from being advertised outside of the site as well as
-- to keep these prefixes from being learned from another site. The
-- exception to this is if there are specific /48 or longer routes
-- created for one or more Local IPv6 prefixes.
--
-- For link-state IGPs, it is suggested that a site utilizing IPv6 local
-- address prefixes be contained within one IGP domain or area. By
-- containing an IPv6 local address prefix to a single link-state area
-- or domain, the distribution of prefixes can be controlled.
--
--4.2. Renumbering and Site Merging
--
-- The use of Local IPv6 addresses in a site results in making
-- communication that uses these addresses independent of renumbering a
-- site's provider-based global addresses.
--
-- When merging multiple sites, the addresses created with these
-- prefixes are unlikely to need to be renumbered because all of the
-- addresses have a high probability of being unique. Routes for each
-- specific prefix would have to be configured to allow routing to work
-- correctly between the formerly separate sites.
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 7]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--4.3. Site Border Router and Firewall Packet Filtering
--
-- While no serious harm will be done if packets with these addresses
-- are sent outside of a site via a default route, it is recommended
-- that routers be configured by default to keep any packets with Local
-- IPv6 addresses from leaking outside of the site and to keep any site
-- prefixes from being advertised outside of their site.
--
-- Site border routers and firewalls should be configured to not forward
-- any packets with Local IPv6 source or destination addresses outside
-- of the site, unless they have been explicitly configured with routing
-- information about specific /48 or longer Local IPv6 prefixes. This
-- will ensure that packets with Local IPv6 destination addresses will
-- not be forwarded outside of the site via a default route. The
-- default behavior of these devices should be to install a "reject"
-- route for these prefixes. Site border routers should respond with
-- the appropriate ICMPv6 Destination Unreachable message to inform the
-- source that the packet was not forwarded. [ICMPV6]. This feedback is
-- important to avoid transport protocol timeouts.
--
-- Routers that maintain peering arrangements between Autonomous Systems
-- throughout the Internet should obey the recommendations for site
-- border routers, unless configured otherwise.
--
--4.4. DNS Issues
--
-- At the present time, AAAA and PTR records for locally assigned local
-- IPv6 addresses are not recommended to be installed in the global DNS.
--
-- For background on this recommendation, one of the concerns about
-- adding AAAA and PTR records to the global DNS for locally assigned
-- Local IPv6 addresses stems from the lack of complete assurance that
-- the prefixes are unique. There is a small possibility that the same
-- locally assigned IPv6 Local addresses will be used by two different
-- organizations both claiming to be authoritative with different
-- contents. In this scenario, it is likely there will be a connection
-- attempt to the closest host with the corresponding locally assigned
-- IPv6 Local address. This may result in connection timeouts,
-- connection failures indicated by ICMP Destination Unreachable
-- messages, or successful connections to the wrong host. Due to this
-- concern, adding AAAA records for these addresses to the global DNS is
-- thought to be unwise.
--
-- Reverse (address-to-name) queries for locally assigned IPv6 Local
-- addresses MUST NOT be sent to name servers for the global DNS, due to
-- the load that such queries would create for the authoritative name
-- servers for the ip6.arpa zone. This form of query load is not
-- specific to locally assigned Local IPv6 addresses; any current form
--
--
--
--Hinden & Haberman Standards Track [Page 8]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- of local addressing creates additional load of this kind, due to
-- reverse queries leaking out of the site. However, since allowing
-- such queries to escape from the site serves no useful purpose, there
-- is no good reason to make the existing load problems worse.
--
-- The recommended way to avoid sending such queries to nameservers for
-- the global DNS is for recursive name server implementations to act as
-- if they were authoritative for an empty d.f.ip6.arpa zone and return
-- RCODE 3 for any such query. Implementations that choose this
-- strategy should allow it to be overridden, but returning an RCODE 3
-- response for such queries should be the default, both because this
-- will reduce the query load problem and also because, if the site
-- administrator has not set up the reverse tree corresponding to the
-- locally assigned IPv6 Local addresses in use, returning RCODE 3 is in
-- fact the correct answer.
--
--4.5. Application and Higher Level Protocol Issues
--
-- Application and other higher level protocols can treat Local IPv6
-- addresses in the same manner as other types of global unicast
-- addresses. No special handling is required. This type of address
-- may not be reachable, but that is no different from other types of
-- IPv6 global unicast address. Applications need to be able to handle
-- multiple addresses that may or may not be reachable at any point in
-- time. In most cases, this complexity should be hidden in APIs.
--
-- From a host's perspective, the difference between Local IPv6 and
-- other types of global unicast addresses shows up as different
-- reachability and could be handled by default in that way. In some
-- cases, it is better for nodes and applications to treat them
-- differently from global unicast addresses. A starting point might be
-- to give them preference over global unicast, but fall back to global
-- unicast if a particular destination is found to be unreachable. Much
-- of this behavior can be controlled by how they are allocated to nodes
-- and put into the DNS. However, it is useful if a host can have both
-- types of addresses and use them appropriately.
--
-- Note that the address selection mechanisms of [ADDSEL], and in
-- particular the policy override mechanism replacing default address
-- selection, are expected to be used on a site where Local IPv6
-- addresses are configured.
--
--4.6. Use of Local IPv6 Addresses for Local Communication
--
-- Local IPv6 addresses, like global scope unicast addresses, are only
-- assigned to nodes if their use has been enabled (via IPv6 address
-- autoconfiguration [ADDAUTO], DHCPv6 [DHCP6], or manually). They are
--
--
--
--
--Hinden & Haberman Standards Track [Page 9]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- not created automatically in the way that IPv6 link-local addresses
-- are and will not appear or be used unless they are purposely
-- configured.
--
-- In order for hosts to autoconfigure Local IPv6 addresses, routers
-- have to be configured to advertise Local IPv6 /64 prefixes in router
-- advertisements, or a DHCPv6 server must have been configured to
-- assign them. In order for a node to learn the Local IPv6 address of
-- another node, the Local IPv6 address must have been installed in a
-- naming system (e.g., DNS, proprietary naming system, etc.) For these
-- reasons, controlling their usage in a site is straightforward.
--
-- To limit the use of Local IPv6 addresses the following guidelines
-- apply:
--
-- - Nodes that are to only be reachable inside of a site: The local
-- DNS should be configured to only include the Local IPv6
-- addresses of these nodes. Nodes with only Local IPv6 addresses
-- must not be installed in the global DNS.
--
-- - Nodes that are to be limited to only communicate with other
-- nodes in the site: These nodes should be set to only
-- autoconfigure Local IPv6 addresses via [ADDAUTO] or to only
-- receive Local IPv6 addresses via [DHCP6]. Note: For the case
-- where both global and Local IPv6 prefixes are being advertised
-- on a subnet, this will require a switch in the devices to only
-- autoconfigure Local IPv6 addresses.
--
-- - Nodes that are to be reachable from inside of the site and from
-- outside of the site: The DNS should be configured to include
-- the global addresses of these nodes. The local DNS may be
-- configured to also include the Local IPv6 addresses of these
-- nodes.
--
-- - Nodes that can communicate with other nodes inside of the site
-- and outside of the site: These nodes should autoconfigure global
-- addresses via [ADDAUTO] or receive global address via [DHCP6].
-- They may also obtain Local IPv6 addresses via the same
-- mechanisms.
--
--4.7. Use of Local IPv6 Addresses with VPNs
--
-- Local IPv6 addresses can be used for inter-site Virtual Private
-- Networks (VPN) if appropriate routes are set up. Because the
-- addresses are unique, these VPNs will work reliably and without the
-- need for translation. They have the additional property that they
-- will continue to work if the individual sites are renumbered or
-- merged.
--
--
--
--Hinden & Haberman Standards Track [Page 10]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--5. Global Routing Considerations
--
-- Section 4.1 provides operational guidelines that forbid default
-- routing of local addresses between sites. Concerns were raised to
-- the IPv6 working group and to the IETF as a whole that sites may
-- attempt to use local addresses as globally routed provider-
-- independent addresses. This section describes why using local
-- addresses as globally-routed provider-independent addresses is
-- unadvisable.
--
--5.1. From the Standpoint of the Internet
--
-- There is a mismatch between the structure of IPv6 local addresses and
-- the normal IPv6 wide area routing model. The /48 prefix of an IPv6
-- local addresses fits nowhere in the normal hierarchy of IPv6 unicast
-- addresses. Normal IPv6 unicast addresses can be routed
-- hierarchically down to physical subnet (link) level and only have to
-- be flat-routed on the physical subnet. IPv6 local addresses would
-- have to be flat-routed even over the wide area Internet.
--
-- Thus, packets whose destination address is an IPv6 local address
-- could be routed over the wide area only if the corresponding /48
-- prefix were carried by the wide area routing protocol in use, such as
-- BGP. This contravenes the operational assumption that long prefixes
-- will be aggregated into many fewer short prefixes, to limit the table
-- size and convergence time of the routing protocol. If a network uses
-- both normal IPv6 addresses [ADDARCH] and IPv6 local addresses, these
-- types of addresses will certainly not aggregate with each other,
-- since they differ from the most significant bit onwards. Neither
-- will IPv6 local addresses aggregate with each other, due to their
-- random bit patterns. This means that there would be a very
-- significant operational penalty for attempting to use IPv6 local
-- address prefixes generically with currently known wide area routing
-- technology.
--
--5.2. From the Standpoint of a Site
--
-- There are a number of design factors in IPv6 local addresses that
-- reduce the likelihood that IPv6 local addresses will be used as
-- arbitrary global unicast addresses. These include:
--
-- - The default rules to filter packets and routes make it very
-- difficult to use IPv6 local addresses for arbitrary use across
-- the Internet. For a site to use them as general purpose unicast
-- addresses, it would have to make sure that the default rules
-- were not being used by all other sites and intermediate ISPs
-- used for their current and future communication.
--
--
--
--
--Hinden & Haberman Standards Track [Page 11]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- - They are not mathematically guaranteed to be unique and are not
-- registered in public databases. Collisions, while highly
-- unlikely, are possible and a collision can compromise the
-- integrity of the communications. The lack of public
-- registration creates operational problems.
--
-- - The addresses are allocated randomly. If a site had multiple
-- prefixes that it wanted to be used globally, the cost of
-- advertising them would be very high because they could not be
-- aggregated.
--
-- - They have a long prefix (i.e., /48) so a single local address
-- prefix doesn't provide enough address space to be used
-- exclusively by the largest organizations.
--
--6. Advantages and Disadvantages
--
--6.1. Advantages
--
-- This approach has the following advantages:
--
-- - Provides Local IPv6 prefixes that can be used independently of
-- any provider-based IPv6 unicast address allocations. This is
-- useful for sites not always connected to the Internet or sites
-- that wish to have a distinct prefix that can be used to localize
-- traffic inside of the site.
--
-- - Applications can treat these addresses in an identical manner as
-- any other type of global IPv6 unicast addresses.
--
-- - Sites can be merged without any renumbering of the Local IPv6
-- addresses.
--
-- - Sites can change their provider-based IPv6 unicast address
-- without disrupting any communication that uses Local IPv6
-- addresses.
--
-- - Well-known prefix that allows for easy filtering at site
-- boundary.
--
-- - Can be used for inter-site VPNs.
--
-- - If accidently leaked outside of a site via routing or DNS, there
-- is no conflict with any other addresses.
--
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 12]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--6.2. Disadvantages
--
-- This approach has the following disadvantages:
--
-- - Not possible to route Local IPv6 prefixes on the global Internet
-- with current routing technology. Consequentially, it is
-- necessary to have the default behavior of site border routers to
-- filter these addresses.
--
-- - There is a very low probability of non-unique locally assigned
-- Global IDs being generated by the algorithm in Section 3.2.3.
-- This risk can be ignored for all practical purposes, but it
-- leads to a theoretical risk of clashing address prefixes.
--
--7. Security Considerations
--
-- Local IPv6 addresses do not provide any inherent security to the
-- nodes that use them. They may be used with filters at site
-- boundaries to keep Local IPv6 traffic inside of the site, but this is
-- no more or less secure than filtering any other type of global IPv6
-- unicast addresses.
--
-- Local IPv6 addresses do allow for address-based security mechanisms,
-- including IPsec, across end to end VPN connections.
--
--8. IANA Considerations
--
-- The IANA has assigned the FC00::/7 prefix to "Unique Local Unicast".
--
--9. References
--
--9.1. Normative References
--
-- [ADDARCH] Hinden, R. and S. Deering, "Internet Protocol Version 6
-- (IPv6) Addressing Architecture", RFC 3513, April 2003.
--
-- [FIPS] "Federal Information Processing Standards Publication",
-- (FIPS PUB) 180-1, Secure Hash Standard, 17 April 1995.
--
-- [GLOBAL] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
-- Unicast Address Format", RFC 3587, August 2003.
--
-- [ICMPV6] Conta, A. and S. Deering, "Internet Control Message
-- Protocol (ICMPv6) for the Internet Protocol Version 6
-- (IPv6) Specification", RFC 2463, December 1998.
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 13]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
-- [IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
-- (IPv6) Specification", RFC 2460, December 1998.
--
-- [NTP] Mills, D., "Network Time Protocol (Version 3)
-- Specification, Implementation and Analysis", RFC 1305,
-- March 1992.
--
-- [RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
-- "Randomness Requirements for Security", BCP 106, RFC 4086,
-- June 2005.
--
-- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
-- [SHA1] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
-- (SHA1)", RFC 3174, September 2001.
--
--9.2. Informative References
--
-- [ADDAUTO] Thomson, S. and T. Narten, "IPv6 Stateless Address
-- Autoconfiguration", RFC 2462, December 1998.
--
-- [ADDSEL] Draves, R., "Default Address Selection for Internet
-- Protocol version 6 (IPv6)", RFC 3484, February 2003.
--
-- [DHCP6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and
-- M. Carney, "Dynamic Host Configuration Protocol for IPv6
-- (DHCPv6)", RFC 3315, July 2003.
--
-- [POPUL] Population Reference Bureau, "World Population Data Sheet
-- of the Population Reference Bureau 2002", August 2002.
--
-- [RTP] Schulzrinne, H., Casner, S., Frederick, R., and V.
-- Jacobson, "RTP: A Transport Protocol for Real-Time
-- Applications", STD 64, RFC 3550, July 2003.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 14]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--Authors' Addresses
--
-- Robert M. Hinden
-- Nokia
-- 313 Fairchild Drive
-- Mountain View, CA 94043
-- USA
--
-- Phone: +1 650 625-2004
-- EMail: bob.hinden@nokia.com
--
--
-- Brian Haberman
-- Johns Hopkins University
-- Applied Physics Lab
-- 11100 Johns Hopkins Road
-- Laurel, MD 20723
-- USA
--
-- Phone: +1 443 778 1319
-- EMail: brian@innovationslab.net
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 15]
--\f
--RFC 4193 Unique Local IPv6 Unicast Addresses October 2005
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2005).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at ietf-
-- ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is currently provided by the
-- Internet Society.
--
--
--
--
--
--
--
--Hinden & Haberman Standards Track [Page 16]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group J. Schlyter
--Request for Comments: 4255 OpenSSH
--Category: Standards Track W. Griffin
-- SPARTA
-- January 2006
--
--
-- Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
--
--Status of This Memo
--
-- This document specifies an Internet standards track protocol for the
-- Internet community, and requests discussion and suggestions for
-- improvements. Please refer to the current edition of the "Internet
-- Official Protocol Standards" (STD 1) for the standardization state
-- and status of this protocol. Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document describes a method of verifying Secure Shell (SSH) host
-- keys using Domain Name System Security (DNSSEC). The document
-- defines a new DNS resource record that contains a standard SSH key
-- fingerprint.
--
--Table of Contents
--
-- 1. Introduction ....................................................2
-- 2. SSH Host Key Verification .......................................2
-- 2.1. Method .....................................................2
-- 2.2. Implementation Notes .......................................2
-- 2.3. Fingerprint Matching .......................................3
-- 2.4. Authentication .............................................3
-- 3. The SSHFP Resource Record .......................................3
-- 3.1. The SSHFP RDATA Format .....................................4
-- 3.1.1. Algorithm Number Specification ......................4
-- 3.1.2. Fingerprint Type Specification ......................4
-- 3.1.3. Fingerprint .........................................5
-- 3.2. Presentation Format of the SSHFP RR ........................5
-- 4. Security Considerations .........................................5
-- 5. IANA Considerations .............................................6
-- 6. Normative References ............................................7
-- 7. Informational References ........................................7
-- 8. Acknowledgements ................................................8
--
--
--
--
--Schlyter & Griffin Standards Track [Page 1]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
--1. Introduction
--
-- The SSH [6] protocol provides secure remote login and other secure
-- network services over an insecure network. The security of the
-- connection relies on the server authenticating itself to the client
-- as well as the user authenticating itself to the server.
--
-- If a connection is established to a server whose public key is not
-- already known to the client, a fingerprint of the key is presented to
-- the user for verification. If the user decides that the fingerprint
-- is correct and accepts the key, the key is saved locally and used for
-- verification for all following connections. While some security-
-- conscious users verify the fingerprint out-of-band before accepting
-- the key, many users blindly accept the presented key.
--
-- The method described here can provide out-of-band verification by
-- looking up a fingerprint of the server public key in the DNS [1][2]
-- and using DNSSEC [5] to verify the lookup.
--
-- In order to distribute the fingerprint using DNS, this document
-- defines a new DNS resource record, "SSHFP", to carry the fingerprint.
--
-- Basic understanding of the DNS system [1][2] and the DNS security
-- extensions [5] is assumed by this document.
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119 [3].
--
--2. SSH Host Key Verification
--
--2.1. Method
--
-- Upon connection to an SSH server, the SSH client MAY look up the
-- SSHFP resource record(s) for the host it is connecting to. If the
-- algorithm and fingerprint of the key received from the SSH server
-- match the algorithm and fingerprint of one of the SSHFP resource
-- record(s) returned from DNS, the client MAY accept the identity of
-- the server.
--
--2.2. Implementation Notes
--
-- Client implementors SHOULD provide a configurable policy used to
-- select the order of methods used to verify a host key. This document
-- defines one method: Fingerprint storage in DNS. Another method
-- defined in the SSH Architecture [6] uses local files to store keys
-- for comparison. Other methods that could be defined in the future
-- might include storing fingerprints in LDAP or other databases. A
--
--
--
--Schlyter & Griffin Standards Track [Page 2]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
-- configurable policy will allow administrators to determine which
-- methods they want to use and in what order the methods should be
-- prioritized. This will allow administrators to determine how much
-- trust they want to place in the different methods.
--
-- One specific scenario for having a configurable policy is where
-- clients do not use fully qualified host names to connect to servers.
-- In this scenario, the implementation SHOULD verify the host key
-- against a local database before verifying the key via the fingerprint
-- returned from DNS. This would help prevent an attacker from
-- injecting a DNS search path into the local resolver and forcing the
-- client to connect to a different host.
--
--2.3. Fingerprint Matching
--
-- The public key and the SSHFP resource record are matched together by
-- comparing algorithm number and fingerprint.
--
-- The public key algorithm and the SSHFP algorithm number MUST
-- match.
--
-- A message digest of the public key, using the message digest
-- algorithm specified in the SSHFP fingerprint type, MUST match the
-- SSHFP fingerprint.
--
--2.4. Authentication
--
-- A public key verified using this method MUST NOT be trusted if the
-- SSHFP resource record (RR) used for verification was not
-- authenticated by a trusted SIG RR.
--
-- Clients that do validate the DNSSEC signatures themselves SHOULD use
-- standard DNSSEC validation procedures.
--
-- Clients that do not validate the DNSSEC signatures themselves MUST
-- use a secure transport (e.g., TSIG [9], SIG(0) [10], or IPsec [8])
-- between themselves and the entity performing the signature
-- validation.
--
--3. The SSHFP Resource Record
--
-- The SSHFP resource record (RR) is used to store a fingerprint of an
-- SSH public host key that is associated with a Domain Name System
-- (DNS) name.
--
-- The RR type code for the SSHFP RR is 44.
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 3]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
--3.1. The SSHFP RDATA Format
--
-- The RDATA for a SSHFP RR consists of an algorithm number, fingerprint
-- type and the fingerprint of the public host key.
--
-- 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
-- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | algorithm | fp type | /
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
-- / /
-- / fingerprint /
-- / /
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
--
--3.1.1. Algorithm Number Specification
--
-- This algorithm number octet describes the algorithm of the public
-- key. The following values are assigned:
--
-- Value Algorithm name
-- ----- --------------
-- 0 reserved
-- 1 RSA
-- 2 DSS
--
-- Reserving other types requires IETF consensus [4].
--
--3.1.2. Fingerprint Type Specification
--
-- The fingerprint type octet describes the message-digest algorithm
-- used to calculate the fingerprint of the public key. The following
-- values are assigned:
--
-- Value Fingerprint type
-- ----- ----------------
-- 0 reserved
-- 1 SHA-1
--
-- Reserving other types requires IETF consensus [4].
--
-- For interoperability reasons, as few fingerprint types as possible
-- should be reserved. The only reason to reserve additional types is
-- to increase security.
--
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 4]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
--3.1.3. Fingerprint
--
-- The fingerprint is calculated over the public key blob as described
-- in [7].
--
-- The message-digest algorithm is presumed to produce an opaque octet
-- string output, which is placed as-is in the RDATA fingerprint field.
--
--3.2. Presentation Format of the SSHFP RR
--
-- The RDATA of the presentation format of the SSHFP resource record
-- consists of two numbers (algorithm and fingerprint type) followed by
-- the fingerprint itself, presented in hex, e.g.:
--
-- host.example. SSHFP 2 1 123456789abcdef67890123456789abcdef67890
--
-- The use of mnemonics instead of numbers is not allowed.
--
--4. Security Considerations
--
-- Currently, the amount of trust a user can realistically place in a
-- server key is proportional to the amount of attention paid to
-- verifying that the public key presented actually corresponds to the
-- private key of the server. If a user accepts a key without verifying
-- the fingerprint with something learned through a secured channel, the
-- connection is vulnerable to a man-in-the-middle attack.
--
-- The overall security of using SSHFP for SSH host key verification is
-- dependent on the security policies of the SSH host administrator and
-- DNS zone administrator (in transferring the fingerprint), detailed
-- aspects of how verification is done in the SSH implementation, and in
-- the client's diligence in accessing the DNS in a secure manner.
--
-- One such aspect is in which order fingerprints are looked up (e.g.,
-- first checking local file and then SSHFP). We note that, in addition
-- to protecting the first-time transfer of host keys, SSHFP can
-- optionally be used for stronger host key protection.
--
-- If SSHFP is checked first, new SSH host keys may be distributed by
-- replacing the corresponding SSHFP in DNS.
--
-- If SSH host key verification can be configured to require SSHFP,
-- SSH host key revocation can be implemented by removing the
-- corresponding SSHFP from DNS.
--
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 5]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
-- As stated in Section 2.2, we recommend that SSH implementors provide
-- a policy mechanism to control the order of methods used for host key
-- verification. One specific scenario for having a configurable policy
-- is where clients use unqualified host names to connect to servers.
-- In this case, we recommend that SSH implementations check the host
-- key against a local database before verifying the key via the
-- fingerprint returned from DNS. This would help prevent an attacker
-- from injecting a DNS search path into the local resolver and forcing
-- the client to connect to a different host.
--
-- A different approach to solve the DNS search path issue would be for
-- clients to use a trusted DNS search path, i.e., one not acquired
-- through DHCP or other autoconfiguration mechanisms. Since there is
-- no way with current DNS lookup APIs to tell whether a search path is
-- from a trusted source, the entire client system would need to be
-- configured with this trusted DNS search path.
--
-- Another dependency is on the implementation of DNSSEC itself. As
-- stated in Section 2.4, we mandate the use of secure methods for
-- lookup and that SSHFP RRs are authenticated by trusted SIG RRs. This
-- is especially important if SSHFP is to be used as a basis for host
-- key rollover and/or revocation, as described above.
--
-- Since DNSSEC only protects the integrity of the host key fingerprint
-- after it is signed by the DNS zone administrator, the fingerprint
-- must be transferred securely from the SSH host administrator to the
-- DNS zone administrator. This could be done manually between the
-- administrators or automatically using secure DNS dynamic update [11]
-- between the SSH server and the nameserver. We note that this is no
-- different from other key enrollment situations, e.g., a client
-- sending a certificate request to a certificate authority for signing.
--
--5. IANA Considerations
--
-- IANA has allocated the RR type code 44 for SSHFP from the standard RR
-- type space.
--
-- IANA has opened a new registry for the SSHFP RR type for public key
-- algorithms. The defined types are:
--
-- 0 is reserved
-- 1 is RSA
-- 2 is DSA
--
-- Adding new reservations requires IETF consensus [4].
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 6]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
-- IANA has opened a new registry for the SSHFP RR type for fingerprint
-- types. The defined types are:
--
-- 0 is reserved
-- 1 is SHA-1
--
-- Adding new reservations requires IETF consensus [4].
--
--6. Normative References
--
-- [1] Mockapetris, P., "Domain names - concepts and facilities", STD
-- 13, RFC 1034, November 1987.
--
-- [2] Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
-- [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
-- [4] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
-- Considerations Section in RFCs", BCP 26, RFC 2434, October
-- 1998.
--
-- [5] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033, March
-- 2005.
--
-- Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions", RFC
-- 4035, March 2005.
--
-- [6] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
-- Protocol Architecture", RFC 4251, January 2006.
--
-- [7] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
-- Transport Layer Protocol", RFC 4253, January 2006.
--
--7. Informational References
--
-- [8] Thayer, R., Doraswamy, N., and R. Glenn, "IP Security Document
-- Roadmap", RFC 2411, November 1998.
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 7]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
-- [9] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
-- Wellington, "Secret Key Transaction Authentication for DNS
-- (TSIG)", RFC 2845, May 2000.
--
-- [10] Eastlake 3rd, D., "DNS Request and Transaction Signatures
-- ( SIG(0)s )", RFC 2931, September 2000.
--
-- [11] Wellington, B., "Secure Domain Name System (DNS) Dynamic
-- Update", RFC 3007, November 2000.
--
--8. Acknowledgements
--
-- The authors gratefully acknowledge, in no particular order, the
-- contributions of the following persons:
--
-- Martin Fredriksson
--
-- Olafur Gudmundsson
--
-- Edward Lewis
--
-- Bill Sommerfeld
--
--Authors' Addresses
--
-- Jakob Schlyter
-- OpenSSH
-- 812 23rd Avenue SE
-- Calgary, Alberta T2G 1N8
-- Canada
--
-- EMail: jakob@openssh.com
-- URI: http://www.openssh.com/
--
--
-- Wesley Griffin
-- SPARTA
-- 7075 Samuel Morse Drive
-- Columbia, MD 21046
-- USA
--
-- EMail: wgriffin@sparta.com
-- URI: http://www.sparta.com/
--
--
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 8]
--\f
--RFC 4255 DNS and SSH Fingerprints January 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Schlyter & Griffin Standards Track [Page 9]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group D. Eastlake 3rd
--Request for Comments: 4343 Motorola Laboratories
--Updates: 1034, 1035, 2181 January 2006
--Category: Standards Track
--
--
-- Domain Name System (DNS) Case Insensitivity Clarification
--
--Status of This Memo
--
-- This document specifies an Internet standards track protocol for the
-- Internet community, and requests discussion and suggestions for
-- improvements. Please refer to the current edition of the "Internet
-- Official Protocol Standards" (STD 1) for the standardization state
-- and status of this protocol. Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- Domain Name System (DNS) names are "case insensitive". This document
-- explains exactly what that means and provides a clear specification
-- of the rules. This clarification updates RFCs 1034, 1035, and 2181.
--
--Table of Contents
--
-- 1. Introduction ....................................................2
-- 2. Case Insensitivity of DNS Labels ................................2
-- 2.1. Escaping Unusual DNS Label Octets ..........................2
-- 2.2. Example Labels with Escapes ................................3
-- 3. Name Lookup, Label Types, and CLASS .............................3
-- 3.1. Original DNS Label Types ...................................4
-- 3.2. Extended Label Type Case Insensitivity Considerations ......4
-- 3.3. CLASS Case Insensitivity Considerations ....................4
-- 4. Case on Input and Output ........................................5
-- 4.1. DNS Output Case Preservation ...............................5
-- 4.2. DNS Input Case Preservation ................................5
-- 5. Internationalized Domain Names ..................................6
-- 6. Security Considerations .........................................6
-- 7. Acknowledgements ................................................7
-- Normative References................................................7
-- Informative References..............................................8
--
--
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 1]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
--1. Introduction
--
-- The Domain Name System (DNS) is the global hierarchical replicated
-- distributed database system for Internet addressing, mail proxy, and
-- other information. Each node in the DNS tree has a name consisting
-- of zero or more labels [STD13, RFC1591, RFC2606] that are treated in
-- a case insensitive fashion. This document clarifies the meaning of
-- "case insensitive" for the DNS. This clarification updates RFCs
-- 1034, 1035 [STD13], and [RFC2181].
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [RFC2119].
--
--2. Case Insensitivity of DNS Labels
--
-- DNS was specified in the era of [ASCII]. DNS names were expected to
-- look like most host names or Internet email address right halves (the
-- part after the at-sign, "@") or to be numeric, as in the in-addr.arpa
-- part of the DNS name space. For example,
--
-- foo.example.net.
-- aol.com.
-- www.gnu.ai.mit.edu.
-- or 69.2.0.192.in-addr.arpa.
--
-- Case-varied alternatives to the above [RFC3092] would be DNS names
-- like
--
-- Foo.ExamplE.net.
-- AOL.COM.
-- WWW.gnu.AI.mit.EDU.
-- or 69.2.0.192.in-ADDR.ARPA.
--
-- However, the individual octets of which DNS names consist are not
-- limited to valid ASCII character codes. They are 8-bit bytes, and
-- all values are allowed. Many applications, however, interpret them
-- as ASCII characters.
--
--2.1. Escaping Unusual DNS Label Octets
--
-- In Master Files [STD13] and other human-readable and -writable ASCII
-- contexts, an escape is needed for the byte value for period (0x2E,
-- ".") and all octet values outside of the inclusive range from 0x21
-- ("!") to 0x7E ("~"). That is to say, 0x2E and all octet values in
-- the two inclusive ranges from 0x00 to 0x20 and from 0x7F to 0xFF.
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 2]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- One typographic convention for octets that do not correspond to an
-- ASCII printing graphic is to use a back-slash followed by the value
-- of the octet as an unsigned integer represented by exactly three
-- decimal digits.
--
-- The same convention can be used for printing ASCII characters so that
-- they will be treated as a normal label character. This includes the
-- back-slash character used in this convention itself, which can be
-- expressed as \092 or \\, and the special label separator period
-- ("."), which can be expressed as and \046 or \. It is advisable to
-- avoid using a backslash to quote an immediately following non-
-- printing ASCII character code to avoid implementation difficulties.
--
-- A back-slash followed by only one or two decimal digits is undefined.
-- A back-slash followed by four decimal digits produces two octets, the
-- first octet having the value of the first three digits considered as
-- a decimal number, and the second octet being the character code for
-- the fourth decimal digit.
--
--2.2. Example Labels with Escapes
--
-- The first example below shows embedded spaces and a period (".")
-- within a label. The second one shows a 5-octet label where the
-- second octet has all bits zero, the third is a backslash, and the
-- fourth octet has all bits one.
--
-- Donald\032E\.\032Eastlake\0323rd.example.
-- and a\000\\\255z.example.
--
--3. Name Lookup, Label Types, and CLASS
--
-- According to the original DNS design decision, comparisons on name
-- lookup for DNS queries should be case insensitive [STD13]. That is
-- to say, a lookup string octet with a value in the inclusive range
-- from 0x41 to 0x5A, the uppercase ASCII letters, MUST match the
-- identical value and also match the corresponding value in the
-- inclusive range from 0x61 to 0x7A, the lowercase ASCII letters. A
-- lookup string octet with a lowercase ASCII letter value MUST
-- similarly match the identical value and also match the corresponding
-- value in the uppercase ASCII letter range.
--
-- (Historical note: The terms "uppercase" and "lowercase" were invented
-- after movable type. The terms originally referred to the two font
-- trays for storing, in partitioned areas, the different physical type
-- elements. Before movable type, the nearest equivalent terms were
-- "majuscule" and "minuscule".)
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 3]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- One way to implement this rule would be to subtract 0x20 from all
-- octets in the inclusive range from 0x61 to 0x7A before comparing
-- octets. Such an operation is commonly known as "case folding", but
-- implementation via case folding is not required. Note that the DNS
-- case insensitivity does NOT correspond to the case folding specified
-- in [ISO-8859-1] or [ISO-8859-2]. For example, the octets 0xDD (\221)
-- and 0xFD (\253) do NOT match, although in other contexts, where they
-- are interpreted as the upper- and lower-case version of "Y" with an
-- acute accent, they might.
--
--3.1. Original DNS Label Types
--
-- DNS labels in wire-encoded names have a type associated with them.
-- The original DNS standard [STD13] had only two types: ASCII labels,
-- with a length from zero to 63 octets, and indirect (or compression)
-- labels, which consist of an offset pointer to a name location
-- elsewhere in the wire encoding on a DNS message. (The ASCII label of
-- length zero is reserved for use as the name of the root node of the
-- name tree.) ASCII labels follow the ASCII case conventions described
-- herein and, as stated above, can actually contain arbitrary byte
-- values. Indirect labels are, in effect, replaced by the name to
-- which they point, which is then treated with the case insensitivity
-- rules in this document.
--
--3.2. Extended Label Type Case Insensitivity Considerations
--
-- DNS was extended by [RFC2671] so that additional label type numbers
-- would be available. (The only such type defined so far is the BINARY
-- type [RFC2673], which is now Experimental [RFC3363].)
--
-- The ASCII case insensitivity conventions only apply to ASCII labels;
-- that is to say, label type 0x0, whether appearing directly or invoked
-- by indirect labels.
--
--3.3. CLASS Case Insensitivity Considerations
--
-- As described in [STD13] and [RFC2929], DNS has an additional axis for
-- data location called CLASS. The only CLASS in global use at this
-- time is the "IN" (Internet) CLASS.
--
-- The handling of DNS label case is not CLASS dependent. With the
-- original design of DNS, it was intended that a recursive DNS resolver
-- be able to handle new CLASSes that were unknown at the time of its
-- implementation. This requires uniform handling of label case
-- insensitivity. Should it become desirable, for example, to allocate
-- a CLASS with "case sensitive ASCII labels", it would be necessary to
-- allocate a new label type for these labels.
--
--
--
--
--Eastlake 3rd Standards Track [Page 4]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
--4. Case on Input and Output
--
-- While ASCII label comparisons are case insensitive, [STD13] says case
-- MUST be preserved on output and preserved when convenient on input.
-- However, this means less than it would appear, since the preservation
-- of case on output is NOT required when output is optimized by the use
-- of indirect labels, as explained below.
--
--4.1. DNS Output Case Preservation
--
-- [STD13] views the DNS namespace as a node tree. ASCII output is as
-- if a name were marshaled by taking the label on the node whose name
-- is to be output, converting it to a typographically encoded ASCII
-- string, walking up the tree outputting each label encountered, and
-- preceding all labels but the first with a period ("."). Wire output
-- follows the same sequence, but each label is wire encoded, and no
-- periods are inserted. No "case conversion" or "case folding" is done
-- during such output operations, thus "preserving" case. However, to
-- optimize output, indirect labels may be used to point to names
-- elsewhere in the DNS answer. In determining whether the name to be
-- pointed to (for example, the QNAME) is the "same" as the remainder of
-- the name being optimized, the case insensitive comparison specified
-- above is done. Thus, such optimization may easily destroy the output
-- preservation of case. This type of optimization is commonly called
-- "name compression".
--
--4.2. DNS Input Case Preservation
--
-- Originally, DNS data came from an ASCII Master File as defined in
-- [STD13] or a zone transfer. DNS Dynamic update and incremental zone
-- transfers [RFC1995] have been added as a source of DNS data [RFC2136,
-- RFC3007]. When a node in the DNS name tree is created by any of such
-- inputs, no case conversion is done. Thus, the case of ASCII labels
-- is preserved if they are for nodes being created. However, when a
-- name label is input for a node that already exists in DNS data being
-- held, the situation is more complex. Implementations are free to
-- retain the case first loaded for such a label, to allow new input to
-- override the old case, or even to maintain separate copies preserving
-- the input case.
--
-- For example, if data with owner name "foo.bar.example" [RFC3092] is
-- loaded and then later data with owner name "xyz.BAR.example" is
-- input, the name of the label on the "bar.example" node (i.e., "bar")
-- might or might not be changed to "BAR" in the DNS stored data. Thus,
-- later retrieval of data stored under "xyz.bar.example" in this case
-- can use "xyz.BAR.example" in all returned data, use "xyz.bar.example"
-- in all returned data, or even, when more than one RR is being
-- returned, use a mixture of these two capitalizations. This last case
--
--
--
--Eastlake 3rd Standards Track [Page 5]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- is unlikely, as optimization of answer length through indirect labels
-- tends to cause only one copy of the name tail ("bar.example" or
-- "BAR.example") to be used for all returned RRs. Note that none of
-- this has any effect on the number or completeness of the RR set
-- returned, only on the case of the names in the RR set returned.
--
-- The same considerations apply when inputting multiple data records
-- with owner names differing only in case. For example, if an "A"
-- record is the first resource record stored under owner name
-- "xyz.BAR.example" and then a second "A" record is stored under
-- "XYZ.BAR.example", the second MAY be stored with the first (lower
-- case initial label) name, the second MAY override the first so that
-- only an uppercase initial label is retained, or both capitalizations
-- MAY be kept in the DNS stored data. In any case, a retrieval with
-- either capitalization will retrieve all RRs with either
-- capitalization.
--
-- Note that the order of insertion into a server database of the DNS
-- name tree nodes that appear in a Master File is not defined so that
-- the results of inconsistent capitalization in a Master File are
-- unpredictable output capitalization.
--
--5. Internationalized Domain Names
--
-- A scheme has been adopted for "internationalized domain names" and
-- "internationalized labels" as described in [RFC3490, RFC3454,
-- RFC3491, and RFC3492]. It makes most of [UNICODE] available through
-- a separate application level transformation from internationalized
-- domain name to DNS domain name and from DNS domain name to
-- internationalized domain name. Any case insensitivity that
-- internationalized domain names and labels have varies depending on
-- the script and is handled entirely as part of the transformation
-- described in [RFC3454] and [RFC3491], which should be seen for
-- further details. This is not a part of the DNS as standardized in
-- STD 13.
--
--6. Security Considerations
--
-- The equivalence of certain DNS label types with case differences, as
-- clarified in this document, can lead to security problems. For
-- example, a user could be confused by believing that two domain names
-- differing only in case were actually different names.
--
-- Furthermore, a domain name may be used in contexts other than the
-- DNS. It could be used as a case sensitive index into some database
-- or file system. Or it could be interpreted as binary data by some
-- integrity or authentication code system. These problems can usually
-- be handled by using a standardized or "canonical" form of the DNS
--
--
--
--Eastlake 3rd Standards Track [Page 6]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- ASCII type labels; that is, always mapping the ASCII letter value
-- octets in ASCII labels to some specific pre-chosen case, either
-- uppercase or lower case. An example of a canonical form for domain
-- names (and also a canonical ordering for them) appears in Section 6
-- of [RFC4034]. See also [RFC3597].
--
-- Finally, a non-DNS name may be stored into DNS with the false
-- expectation that case will always be preserved. For example,
-- although this would be quite rare, on a system with case sensitive
-- email address local parts, an attempt to store two Responsible Person
-- (RP) [RFC1183] records that differed only in case would probably
-- produce unexpected results that might have security implications.
-- That is because the entire email address, including the possibly case
-- sensitive local or left-hand part, is encoded into a DNS name in a
-- readable fashion where the case of some letters might be changed on
-- output as described above.
--
--7. Acknowledgements
--
-- The contributions to this document by Rob Austein, Olafur
-- Gudmundsson, Daniel J. Anderson, Alan Barrett, Marc Blanchet, Dana,
-- Andreas Gustafsson, Andrew Main, Thomas Narten, and Scott Seligman
-- are gratefully acknowledged.
--
--Normative References
--
-- [ASCII] ANSI, "USA Standard Code for Information Interchange",
-- X3.4, American National Standards Institute: New York,
-- 1968.
--
-- [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
-- August 1996.
--
-- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
-- [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
-- "Dynamic Updates in the Domain Name System (DNS
-- UPDATE)", RFC 2136, April 1997.
--
-- [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
-- Specification", RFC 2181, July 1997.
--
-- [RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
-- Update", RFC 3007, November 2000.
--
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 7]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
-- (RR) Types", RFC 3597, September 2003.
--
-- [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
-- Rose, "Resource Records for the DNS Security
-- Extensions", RFC 4034, March 2005.
--
-- [STD13] Mockapetris, P., "Domain names - concepts and
-- facilities", STD 13, RFC 1034, November 1987.
--
-- Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
--Informative References
--
-- [ISO-8859-1] International Standards Organization, Standard for
-- Character Encodings, Latin-1.
--
-- [ISO-8859-2] International Standards Organization, Standard for
-- Character Encodings, Latin-2.
--
-- [RFC1183] Everhart, C., Mamakos, L., Ullmann, R., and P.
-- Mockapetris, "New DNS RR Definitions", RFC 1183, October
-- 1990.
--
-- [RFC1591] Postel, J., "Domain Name System Structure and
-- Delegation", RFC 1591, March 1994.
--
-- [RFC2606] Eastlake 3rd, D. and A. Panitz, "Reserved Top Level DNS
-- Names", BCP 32, RFC 2606, June 1999.
--
-- [RFC2929] Eastlake 3rd, D., Brunner-Williams, E., and B. Manning,
-- "Domain Name System (DNS) IANA Considerations", BCP 42,
-- RFC 2929, September 2000.
--
-- [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC
-- 2671, August 1999.
--
-- [RFC2673] Crawford, M., "Binary Labels in the Domain Name System",
-- RFC 2673, August 1999.
--
-- [RFC3092] Eastlake 3rd, D., Manros, C., and E. Raymond, "Etymology
-- of "Foo"", RFC 3092, 1 April 2001.
--
-- [RFC3363] Bush, R., Durand, A., Fink, B., Gudmundsson, O., and T.
-- Hain, "Representing Internet Protocol version 6 (IPv6)
-- Addresses in the Domain Name System (DNS)", RFC 3363,
-- August 2002.
--
--
--
--Eastlake 3rd Standards Track [Page 8]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
-- [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
-- Internationalized Strings ("stringprep")", RFC 3454,
-- December 2002.
--
-- [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
-- "Internationalizing Domain Names in Applications
-- (IDNA)", RFC 3490, March 2003.
--
-- [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
-- Profile for Internationalized Domain Names (IDN)", RFC
-- 3491, March 2003.
--
-- [RFC3492] Costello, A., "Punycode: A Bootstring encoding of
-- Unicode for Internationalized Domain Names in
-- Applications (IDNA)", RFC 3492, March 2003.
--
-- [UNICODE] The Unicode Consortium, "The Unicode Standard",
-- <http://www.unicode.org/unicode/standard/standard.html>.
--
--Author's Address
--
-- Donald E. Eastlake 3rd
-- Motorola Laboratories
-- 155 Beaver Street
-- Milford, MA 01757 USA
--
-- Phone: +1 508-786-7554 (w)
-- EMail: Donald.Eastlake@motorola.com
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 9]
--\f
--RFC 4343 DNS Case Insensitivity Clarification January 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Eastlake 3rd Standards Track [Page 10]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group J. Rosenberg, Ed.
--Request for Comments: 4367 IAB
--Category: Informational February 2006
--
--
-- What's in a Name: False Assumptions about DNS Names
--
--Status of This Memo
--
-- This memo provides information for the Internet community. It does
-- not specify an Internet standard of any kind. Distribution of this
-- memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- The Domain Name System (DNS) provides an essential service on the
-- Internet, mapping structured names to a variety of data, usually IP
-- addresses. These names appear in email addresses, Uniform Resource
-- Identifiers (URIs), and other application-layer identifiers that are
-- often rendered to human users. Because of this, there has been a
-- strong demand to acquire names that have significance to people,
-- through equivalence to registered trademarks, company names, types of
-- services, and so on. There is a danger in this trend; the humans and
-- automata that consume and use such names will associate specific
-- semantics with some names and thereby make assumptions about the
-- services that are, or should be, provided by the hosts associated
-- with the names. Those assumptions can often be false, resulting in a
-- variety of failure conditions. This document discusses this problem
-- in more detail and makes recommendations on how it can be avoided.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Rosenberg Informational [Page 1]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
--Table of Contents
--
-- 1. Introduction ....................................................2
-- 2. Target Audience .................................................4
-- 3. Modeling Usage of the DNS .......................................4
-- 4. Possible Assumptions ............................................5
-- 4.1. By the User ................................................5
-- 4.2. By the Client ..............................................6
-- 4.3. By the Server ..............................................7
-- 5. Consequences of False Assumptions ...............................8
-- 6. Reasons Why the Assumptions Can Be False ........................9
-- 6.1. Evolution ..................................................9
-- 6.2. Leakage ...................................................10
-- 6.3. Sub-Delegation ............................................10
-- 6.4. Mobility ..................................................12
-- 6.5. Human Error ...............................................12
-- 7. Recommendations ................................................12
-- 8. A Note on RFC 2219 and RFC 2782 ................................13
-- 9. Security Considerations ........................................14
-- 10. Acknowledgements ..............................................14
-- 11. IAB Members ...................................................14
-- 12. Informative References ........................................15
--
--1. Introduction
--
-- The Domain Name System (DNS) [1] provides an essential service on the
-- Internet, mapping structured names to a variety of different types of
-- data. Most often it is used to obtain the IP address of a host
-- associated with that name [2] [1] [3]. However, it can be used to
-- obtain other information, and proposals have been made for nearly
-- everything, including geographic information [4].
--
-- Domain names are most often used in identifiers used by application
-- protocols. The most well known include email addresses and URIs,
-- such as the HTTP URL [5], Real Time Streaming Protocol (RTSP) URL
-- [6], and SIP URI [7]. These identifiers are ubiquitous, appearing on
-- business cards, web pages, street signs, and so on. Because of this,
-- there has been a strong demand to acquire domain names that have
-- significance to people through equivalence to registered trademarks,
-- company names, types of services, and so on. Such identifiers serve
-- many business purposes, including extension of brand, advertising,
-- and so on.
--
-- People often make assumptions about the type of service that is or
-- should be provided by a host associated with that name, based on
-- their expectations and understanding of what the name implies. This,
-- in turn, triggers attempts by organizations to register domain names
-- based on that presumed user expectation. Examples of this are the
--
--
--
--Rosenberg Informational [Page 2]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- various proposals for a Top-Level Domain (TLD) that could be
-- associated with adult content [8], the requests for creation of TLDs
-- associated with mobile devices and services, and even phishing
-- attacks.
--
-- When these assumptions are codified into the behavior of an
-- automaton, such as an application client or server, as a result of
-- implementor choice, management directive, or domain owner policy, the
-- overall system can fail in various ways. This document describes a
-- number of typical ways in which these assumptions can be codified,
-- how they can be wrong, the consequences of those mistakes, and the
-- recommended ways in which they can be avoided.
--
-- Section 4 describes some of the possible assumptions that clients,
-- servers, and people can make about a domain name. In this context,
-- an "assumption" is defined as any behavior that is expected when
-- accessing a service at a domain name, even though the behavior is not
-- explicitly codified in protocol specifications. Frequently, these
-- assumptions involve ignoring parts of a specification based on an
-- assumption that the client or server is deployed in an environment
-- that is more rigid than the specification allows. Section 5
-- overviews some of the consequences of these false assumptions.
-- Generally speaking, these consequences can include a variety of
-- different interoperability failures, user experience failures, and
-- system failures. Section 6 discusses why these assumptions can be
-- false from the very beginning or become false at some point in the
-- future. Most commonly, they become false because the environment
-- changes in unexpected ways over time, and what was a valid assumption
-- before, no longer is. Other times, the assumptions prove wrong
-- because they were based on the belief that a specific community of
-- clients and servers was participating, and an element outside of that
-- community began participating.
--
-- Section 7 then provides some recommendations. These recommendations
-- encapsulate some of the engineering mantras that have been at the
-- root of Internet protocol design for decades. These include:
--
-- Follow the specifications.
--
-- Use the capability negotiation techniques provided in the
-- protocols.
--
-- Be liberal in what you accept, and conservative in what you send.
-- [18]
--
-- Overall, automata should not change their behavior within a protocol
-- based on the domain name, or some component of the domain name, of
-- the host they are communicating with.
--
--
--
--Rosenberg Informational [Page 3]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
--2. Target Audience
--
-- This document has several audiences. Firstly, it is aimed at
-- implementors who ultimately develop the software that make the false
-- assumptions that are the subject of this document. The
-- recommendations described here are meant to reinforce the engineering
-- guidelines that are often understood by implementors, but frequently
-- forgotten as deadlines near and pressures mount.
--
-- The document is also aimed at technology managers, who often develop
-- the requirements that lead to these false assumptions. For them,
-- this document serves as a vehicle for emphasizing the importance of
-- not taking shortcuts in the scope of applicability of a project.
--
-- Finally, this document is aimed at domain name policy makers and
-- administrators. For them, it points out the perils in establishing
-- domain policies that get codified into the operation of applications
-- running within that domain.
--
--3. Modeling Usage of the DNS
--
--
-- +--------+
-- | |
-- | |
-- | DNS |
-- |Service |
-- | |
-- +--------+
-- ^ |
-- | |
-- | |
-- | |
-- /--\ | |
-- | | | V
-- | | +--------+ +--------+
-- \--/ | | | |
-- | | | | |
-- ---+--- | Client |-------------------->| Server |
-- | | | | |
-- | | | | |
-- /\ +--------+ +--------+
-- / \
-- / \
--
-- User
-- Figure 1
--
--
--
--
--Rosenberg Informational [Page 4]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- Figure 1 shows a simple conceptual model of how the DNS is used by
-- applications. A user of the application obtains an identifier for
-- particular content or service it wishes to obtain. This identifier
-- is often a URL or URI that contains a domain name. The user enters
-- this identifier into its client application (for example, by typing
-- in the URL in a web browser window). The client is the automaton (a
-- software and/or hardware system) that contacts a server for that
-- application in order to provide service to the user. To do that, it
-- contacts a DNS server to resolve the domain name in the identifier to
-- an IP address. It then contacts the server at that IP address. This
-- simple model applies to application protocols such as HTTP [5], SIP
-- [7], RTSP [6], and SMTP [9].
--
-- >From this model, it is clear that three entities in the system can
-- potentially make false assumptions about the service provided by the
-- server. The human user may form expectations relating to the content
-- of the service based on a parsing of the host name from which the
-- content originated. The server might assume that the client
-- connecting to it supports protocols that it does not, can process
-- content that it cannot, or has capabilities that it does not.
-- Similarly, the client might assume that the server supports
-- protocols, content, or capabilities that it does not. Furthermore,
-- applications can potentially contain a multiplicity of humans,
-- clients, and servers, all of which can independently make these false
-- assumptions.
--
--4. Possible Assumptions
--
-- For each of the three elements, there are many types of false
-- assumptions that can be made.
--
--4.1. By the User
--
-- The set of possible assumptions here is nearly boundless. Users
-- might assume that an HTTP URL that looks like a company name maps to
-- a server run by that company. They might assume that an email from a
-- email address in the .gov TLD is actually from a government employee.
-- They might assume that the content obtained from a web server within
-- a TLD labeled as containing adult materials (for example, .sex)
-- actually contains adult content [8]. These assumptions are
-- unavoidable, may all be false, and are not the focus of this
-- document.
--
--
--
--
--
--
--
--
--
--Rosenberg Informational [Page 5]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
--4.2. By the Client
--
-- Even though the client is an automaton, it can make some of the same
-- assumptions that a human user might make. For example, many clients
-- assume that any host with a hostname that begins with "www" is a web
-- server, even though this assumption may be false.
--
-- In addition, the client concerns itself with the protocols needed to
-- communicate with the server. As a result, it might make assumptions
-- about the operation of the protocols for communicating with the
-- server. These assumptions manifest themselves in an implementation
-- when a standardized protocol negotiation technique defined by the
-- protocol is ignored, and instead, some kind of rule is coded into the
-- software that comes to its own conclusion about what the negotiation
-- would have determined. The result is often a loss of
-- interoperability, degradation in reliability, and worsening of user
-- experience.
--
-- Authentication Algorithm: Though a protocol might support a
-- multiplicity of authentication techniques, a client might assume
-- that a server always supports one that is only optional according
-- to the protocol. For example, a SIP client contacting a SIP
-- server in a domain that is apparently used to identify mobile
-- devices (for example, www.example.cellular) might assume that the
-- server supports the optional Authentication and Key Agreement
-- (AKA) digest technique [10], just because of the domain name that
-- was used to access the server. As another example, a web client
-- might assume that a server with the name https.example.com
-- supports HTTP over Transport Layer Security (TLS) [16].
--
-- Data Formats: Though a protocol might allow a multiplicity of data
-- formats to be sent from the server to the client, the client might
-- assume a specific one, rather than using the content labeling and
-- negotiation capabilities of the underlying protocol. For example,
-- an RTSP client might assume that all audio content delivered to it
-- from media.example.cellular uses a low-bandwidth codec. As
-- another example, a mail client might assume that the contents of
-- messages it retrieves from a mail server at mail.example.cellular
-- are always text, instead of checking the MIME headers [11] in the
-- message in order to determine the actual content type.
--
-- Protocol Extensions: A client may attempt an operation on the server
-- that requires the server to support an optional protocol
-- extension. However, rather than implementing the necessary
-- fallback logic, the client may falsely assume that the extension
-- is supported. As an example, a SIP client that requires reliable
-- provisional responses to its request (RFC 3262 [17]) might assume
-- that this extension is supported on servers in the domain
--
--
--
--Rosenberg Informational [Page 6]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- sip.example.telecom. Furthermore, the client would not implement
-- the fallback behavior defined in RFC 3262, since it would assume
-- that all servers it will communicate with are in this domain and
-- that all therefore support this extension. However, if the
-- assumptions prove wrong, the client is unable to make any phone
-- calls.
--
-- Languages: A client may support facilities for processing text
-- content differently depending on the language of the text. Rather
-- than determining the language from markers in the message from the
-- server, the client might assume a language based on the domain
-- name. This assumption can easily be wrong. For example, a client
-- might assume that any text in a web page retrieved from a server
-- within the .de country code TLD (ccTLD) is in German, and attempt
-- a translation to Finnish. This would fail dramatically if the
-- text was actually in French. Unfortunately, this client behavior
-- is sometimes exhibited because the server has not properly labeled
-- the language of the content in the first place, often because the
-- server assumed such a labeling was not needed. This is an example
-- of how these false assumptions can create vicious cycles.
--
--4.3. By the Server
--
-- The server, like the client, is an automaton. Let us consider one
-- servicing a particular domain -- www.company.cellular, for example.
-- It might assume that all clients connecting to this domain support
-- particular capabilities, rather than using the underlying protocol to
-- make this determination. Some examples include:
--
-- Authentication Algorithm: The server can assume that a client
-- supports a particular, optional, authentication technique, and it
-- therefore does not support the mandatory one.
--
-- Language: The server can serve content in a particular language,
-- based on an assumption that clients accessing the domain speak a
-- particular language, or based on an assumption that clients coming
-- from a particular IP address speak a certain language.
--
-- Data Formats: The server can assume that the client supports a
-- particular set of MIME types and is only capable of sending ones
-- within that set. When it generates content in a protocol
-- response, it ignores any content negotiation headers that were
-- present in the request. For example, a web server might ignore
-- the Accept HTTP header field and send a specific image format.
--
--
--
--
--
--
--
--Rosenberg Informational [Page 7]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- Protocol Extensions: The server might assume that the client supports
-- a particular optional protocol extension, and so it does not
-- support the fallback behavior necessary in the case where the
-- client does not.
--
-- Client Characteristics: The server might assume certain things about
-- the physical characteristics of its clients, such as memory
-- footprint, processing power, screen sizes, screen colors, pointing
-- devices, and so on. Based on these assumptions, it might choose
-- specific behaviors when processing a request. For example, a web
-- server might always assume that clients connect through cell
-- phones, and therefore return content that lacks images and is
-- tuned for such devices.
--
--5. Consequences of False Assumptions
--
-- There are numerous negative outcomes that can arise from the various
-- false assumptions that users, servers, and clients can make. These
-- include:
--
-- Interoperability Failure: In these cases, the client or server
-- assumed some kind of protocol operation, and this assumption was
-- wrong. The result is that the two are unable to communicate, and
-- the user receives some kind of an error. This represents a total
-- interoperability failure, manifesting itself as a lack of service
-- to users of the system. Unfortunately, this kind of failure
-- persists. Repeated attempts over time by the client to access the
-- service will fail. Only a change in the server or client software
-- can fix this problem.
--
-- System Failure: In these cases, the client or server misinterpreted a
-- protocol operation, and this misinterpretation was serious enough
-- to uncover a bug in the implementation. The bug causes a system
-- crash or some kind of outage, either transient or permanent (until
-- user reset). If this failure occurs in a server, not only will
-- the connecting client lose service, but other clients attempting
-- to connect will not get service. As an example, if a web server
-- assumes that content passed to it from a client (created, for
-- example, by a digital camera) is of a particular content type, and
-- it always passes image content to a codec for decompression prior
-- to storage, the codec might crash when it unexpectedly receives an
-- image compressed in a different format. Of course, it might crash
-- even if the Content-Type was correct, but the compressed bitstream
-- was invalid. False assumptions merely introduce additional
-- failure cases.
--
--
--
--
--
--
--Rosenberg Informational [Page 8]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- Poor User Experience: In these cases, the client and server
-- communicate, but the user receives a diminished user experience.
-- For example, if a client on a PC connects to a web site that
-- provides content for mobile devices, the content may be
-- underwhelming when viewed on the PC. Or, a client accessing a
-- streaming media service may receive content of very low bitrate,
-- even though the client supported better codecs. Indeed, if a user
-- wishes to access content from both a cellular device and a PC
-- using a shared address book (that is, an address book shared
-- across multiple devices), the user would need two entries in that
-- address book, and would need to use the right one from the right
-- device. This is a poor user experience.
--
-- Degraded Security: In these cases, a weaker security mechanism is
-- used than the one that ought to have been used. As an example, a
-- server in a domain might assume that it is only contacted by
-- clients with a limited set of authentication algorithms, even
-- though the clients have been recently upgraded to support a
-- stronger set.
--
--6. Reasons Why the Assumptions Can Be False
--
-- Assumptions made by clients and servers about the operation of
-- protocols when contacting a particular domain are brittle, and can be
-- wrong for many reasons. On the server side, many of the assumptions
-- are based on the notion that a domain name will only be given to, or
-- used by, a restricted set of clients. If the holder of the domain
-- name assumes something about those clients, and can assume that only
-- those clients use the domain name, then it can configure or program
-- the server to operate specifically for those clients. Both parts of
-- this assumption can be wrong, as discussed in more detail below.
--
-- On the client side, the notion is similar, being based on the
-- assumption that a server within a particular domain will provide a
-- specific type of service. Sub-delegation and evolution, both
-- discussed below, can make these assumptions wrong.
--
--6.1. Evolution
--
-- The Internet and the devices that access it are constantly evolving,
-- often at a rapid pace. Unfortunately, there is a tendency to build
-- for the here and now, and then worry about the future at a later
-- time. Many of the assumptions above are predicated on
-- characteristics of today's clients and servers. Support for specific
-- protocols, authentication techniques, or content are based on today's
-- standards and today's devices. Even though they may, for the most
-- part, be true, they won't always be. An excellent example is mobile
-- devices. A server servicing a domain accessed by mobile devices
--
--
--
--Rosenberg Informational [Page 9]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- might try to make assumptions about the protocols, protocol
-- extensions, security mechanisms, screen sizes, or processor power of
-- such devices. However, all of these characteristics can and will
-- change over time.
--
-- When they do change, the change is usually evolutionary. The result
-- is that the assumptions remain valid in some cases, but not in
-- others. It is difficult to fix such systems, since it requires the
-- server to detect what type of client is connecting, and what its
-- capabilities are. Unless the system is built and deployed with these
-- capability negotiation techniques built in to begin with, such
-- detection can be extremely difficult. In fact, fixing it will often
-- require the addition of such capability negotiation features that, if
-- they had been in place and used to begin with, would have avoided the
-- problem altogether.
--
--6.2. Leakage
--
-- Servers also make assumptions because of the belief that they will
-- only be accessed by specific clients, and in particular, those that
-- are configured or provisioned to use the domain name. In essence,
-- there is an assumption of community -- that a specific community
-- knows and uses the domain name, while others outside of the community
-- do not.
--
-- The problem is that this notion of community is a false one. The
-- Internet is global. The DNS is global. There is no technical
-- barrier that separates those inside of the community from those
-- outside. The ease with which information propagates across the
-- Internet makes it extremely likely that such domain names will
-- eventually find their way into clients outside of the presumed
-- community. The ubiquitous presence of domain names in various URI
-- formats, coupled with the ease of conveyance of URIs, makes such
-- leakage merely a matter of time. Furthermore, since the DNS is
-- global, and since it can only have one root [12], it becomes possible
-- for clients outside of the community to search and find and use such
-- "special" domain names.
--
-- Indeed, this leakage is a strength of the Internet architecture, not
-- a weakness. It enables global access to services from any client
-- with a connection to the Internet. That, in turn, allows for rapid
-- growth in the number of customers for any particular service.
--
--6.3. Sub-Delegation
--
-- Clients and users make assumptions about domains because of the
-- notion that there is some kind of centralized control that can
-- enforce those assumptions. However, the DNS is not centralized; it
--
--
--
--Rosenberg Informational [Page 10]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- is distributed. If a domain doesn't delegate its sub-domains and has
-- its records within a single zone, it is possible to maintain a
-- centralized policy about operation of its domain. However, once a
-- domain gets sufficiently large that the domain administrators begin
-- to delegate sub-domains to other authorities, it becomes increasingly
-- difficult to maintain any kind of central control on the nature of
-- the service provided in each sub-domain.
--
-- Similarly, the usage of domain names with human semantic connotation
-- tends to lead to a registration of multiple domains in which a
-- particular service is to run. As an example, a service provider with
-- the name "example" might register and set up its services in
-- "example.com", "example.net", and generally example.foo for each foo
-- that is a valid TLD. This, like sub-delegation, results in a growth
-- in the number of domains over which it is difficult to maintain
-- centralized control.
--
-- Not that it is not possible, since there are many examples of
-- successful administration of policies across sub-domains many levels
-- deep. However, it takes an increasing amount of effort to ensure
-- this result, as it requires human intervention and the creation of
-- process and procedure. Automated validation of adherence to policies
-- is very difficult to do, as there is no way to automatically verify
-- many policies that might be put into place.
--
-- A less costly process for providing centralized management of
-- policies is to just hope that any centralized policies are being
-- followed, and then wait for complaints or perform random audits.
-- Those approaches have many problems.
--
-- The invalidation of assumptions due to sub-delegation is discussed in
-- further detail in Section 4.1.3 of [8] and in Section 3.3 of [20].
--
-- As a result of the fragility of policy continuity across sub-
-- delegations, if a client or user assumes some kind of property
-- associated with a TLD (such as ".wifi"), it becomes increasingly more
-- likely with the number of sub-domains that this property will not
-- exist in a server identified by a particular name. For example, in
-- "store.chain.company.provider.wifi", there may be four levels of
-- delegation from ".wifi", making it quite likely that, unless the
-- holder of ".wifi" is working diligently, the properties that the
-- holder of ".wifi" wishes to enforce are not present. These
-- properties may not be present due to human error or due to a willful
-- decision not to adhere to them.
--
--
--
--
--
--
--
--Rosenberg Informational [Page 11]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
--6.4. Mobility
--
-- One of the primary value propositions of a hostname as an identifier
-- is its persistence. A client can change IP addresses, yet still
-- retain a persistent identifier used by other hosts to reach it.
-- Because their value derives from their persistence, hostnames tend to
-- move with a host not just as it changes IP addresses, but as it
-- changes access network providers and technologies. For this reason,
-- assumptions made about a host based on the presumed access network
-- corresponding to that hostname tend to be wrong over time. As an
-- example, a PC might normally be connected to its broadband provider,
-- and through dynamic DNS have a hostname within the domain of that
-- provider. However, one cannot assume that any host within that
-- network has access over a broadband link; the user could connect
-- their PC over a low-bandwidth wireless access network and still
-- retain its domain name.
--
--6.5. Human Error
--
-- Of course, human error can be the source of errors in any system, and
-- the same is true here. There are many examples relevant to the
-- problem under discussion.
--
-- A client implementation may make the assumption that, just because a
-- DNS SRV record exists for a particular protocol in a particular
-- domain, indicating that the service is available on some port, that
-- the service is, in fact, running there. This assumption could be
-- wrong because the SRV records haven't been updated by the system
-- administrators to reflect the services currently running. As another
-- example, a client might assume that a particular domain policy
-- applies to all sub-domains. However, a system administrator might
-- have omitted to apply the policy to servers running in one of those
-- sub-domains.
--
--7. Recommendations
--
-- Based on these problems, the clear conclusion is that clients,
-- servers, and users should not make assumptions on the nature of the
-- service provided to, or by, a domain. More specifically, however,
-- the following can be said:
--
-- Follow the specifications: When specifications define mandatory
-- baseline procedures and formats, those should be implemented and
-- supported, even if the expectation is that optional procedures
-- will most often be used. For example, if a specification mandates
-- a particular baseline authentication technique, but allows others
-- to be negotiated and used, implementations need to implement the
-- baseline authentication algorithm even if the other ones are used
--
--
--
--Rosenberg Informational [Page 12]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- most of the time. Put more simply, the behavior of the protocol
-- machinery should never change based on the domain name of the
-- host.
--
-- Use capability negotiation: Many protocols are engineered with
-- capability negotiation mechanisms. For example, a content
-- negotiation framework has been defined for protocols using MIME
-- content [13] [14] [15]. SIP allows for clients to negotiate the
-- media types used in the multimedia session, as well as protocol
-- parameters. HTTP allows for clients to negotiate the media types
-- returned in requests for content. When such features are
-- available in a protocol, client and servers should make use of
-- them rather than making assumptions about supported capabilities.
-- A corollary is that protocol designers should include such
-- mechanisms when evolution is expected in the usage of the
-- protocol.
--
-- "Be liberal in what you accept, and conservative in what you send"
-- [18]: This axiom of Internet protocol design is applicable here
-- as well. Implementations should be prepared for the full breadth
-- of what a protocol allows another entity to send, rather than be
-- limiting in what it is willing to receive.
--
-- To summarize -- there is never a need to make assumptions. Rather
-- than doing so, utilize the specifications and the negotiation
-- capabilities they provide, and the overall system will be robust and
-- interoperable.
--
--8. A Note on RFC 2219 and RFC 2782
--
-- Based on the definition of an assumption given here, the behavior
-- hinted at by records in the DNS also represents an assumption. RFC
-- 2219 [19] defines well-known aliases that can be used to construct
-- domain names for reaching various well-known services in a domain.
-- This approach was later followed by the definition of a new resource
-- record, the SRV record [2], which specifies that a particular service
-- is running on a server in a domain. Although both of these
-- mechanisms are useful as a hint that a particular service is running
-- in a domain, both of them represent assumptions that may be false.
-- However, they differ in the set of reasons why those assumptions
-- might be false.
--
-- A client that assumes that "ftp.example.com" is an FTP server may be
-- wrong because the presumed naming convention in RFC 2219 was not
-- known by, or not followed by, the owner of domain.com. With RFC
-- 2782, an SRV record for a particular service would be present only by
-- explicit choice of the domain administrator, and thus a client that
--
--
--
--
--Rosenberg Informational [Page 13]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- assumes that the corresponding host provides this service would be
-- wrong only because of human error in configuration. In this case,
-- the assumption is less likely to be wrong, but it certainly can be.
--
-- The only way to determine with certainty that a service is running on
-- a host is to initiate a connection to the port for that service, and
-- check. Implementations need to be careful not to codify any
-- behaviors that cause failures should the information provided in the
-- record actually be false. This borders on common sense for robust
-- implementations, but it is valuable to raise this point explicitly.
--
--9. Security Considerations
--
-- One of the assumptions that can be made by clients or servers is the
-- availability and usage (or lack thereof) of certain security
-- protocols and algorithms. For example, a client accessing a service
-- in a particular domain might assume a specific authentication
-- algorithm or hash function in the application protocol. It is
-- possible that, over time, weaknesses are found in such a technique,
-- requiring usage of a different mechanism. Similarly, a system might
-- start with an insecure mechanism, and then decide later on to use a
-- secure one. In either case, assumptions made on security properties
-- can result in interoperability failures, or worse yet, providing
-- service in an insecure way, even though the client asked for, and
-- thought it would get, secure service. These kinds of assumptions are
-- fundamentally unsound even if the records themselves are secured with
-- DNSSEC.
--
--10. Acknowledgements
--
-- The IAB would like to thank John Klensin, Keith Moore and Peter Koch
-- for their comments.
--
--11. IAB Members
--
-- Internet Architecture Board members at the time of writing of this
-- document are:
--
-- Bernard Aboba
--
-- Loa Andersson
--
-- Brian Carpenter
--
-- Leslie Daigle
--
-- Patrik Faltstrom
--
--
--
--
--Rosenberg Informational [Page 14]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- Bob Hinden
--
-- Kurtis Lindqvist
--
-- David Meyer
--
-- Pekka Nikander
--
-- Eric Rescorla
--
-- Pete Resnick
--
-- Jonathan Rosenberg
--
--12. Informative References
--
-- [1] Mockapetris, P., "Domain names - concepts and facilities",
-- STD 13, RFC 1034, November 1987.
--
-- [2] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
-- specifying the location of services (DNS SRV)", RFC 2782,
-- February 2000.
--
-- [3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
-- Three: The Domain Name System (DNS) Database", RFC 3403,
-- October 2002.
--
-- [4] Davis, C., Vixie, P., Goodwin, T., and I. Dickinson, "A Means
-- for Expressing Location Information in the Domain Name System",
-- RFC 1876, January 1996.
--
-- [5] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
-- Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --
-- HTTP/1.1", RFC 2616, June 1999.
--
-- [6] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming
-- Protocol (RTSP)", RFC 2326, April 1998.
--
-- [7] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
-- Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
-- Session Initiation Protocol", RFC 3261, June 2002.
--
-- [8] Eastlake, D., ".sex Considered Dangerous", RFC 3675,
-- February 2004.
--
-- [9] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
-- April 2001.
--
--
--
--
--Rosenberg Informational [Page 15]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
-- [10] Niemi, A., Arkko, J., and V. Torvinen, "Hypertext Transfer
-- Protocol (HTTP) Digest Authentication Using Authentication and
-- Key Agreement (AKA)", RFC 3310, September 2002.
--
-- [11] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
-- Extensions (MIME) Part One: Format of Internet Message Bodies",
-- RFC 2045, November 1996.
--
-- [12] Internet Architecture Board, "IAB Technical Comment on the
-- Unique DNS Root", RFC 2826, May 2000.
--
-- [13] Klyne, G., "Indicating Media Features for MIME Content",
-- RFC 2912, September 2000.
--
-- [14] Klyne, G., "A Syntax for Describing Media Feature Sets",
-- RFC 2533, March 1999.
--
-- [15] Klyne, G., "Protocol-independent Content Negotiation
-- Framework", RFC 2703, September 1999.
--
-- [16] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
--
-- [17] Rosenberg, J. and H. Schulzrinne, "Reliability of Provisional
-- Responses in Session Initiation Protocol (SIP)", RFC 3262,
-- June 2002.
--
-- [18] Braden, R., "Requirements for Internet Hosts - Communication
-- Layers", STD 3, RFC 1122, October 1989.
--
-- [19] Hamilton, M. and R. Wright, "Use of DNS Aliases for Network
-- Services", BCP 17, RFC 2219, October 1997.
--
-- [20] Faltstrom, P., "Design Choices When Expanding DNS", Work in
-- Progress, June 2005.
--
--Author's Address
--
-- Jonathan Rosenberg, Editor
-- IAB
-- 600 Lanidex Plaza
-- Parsippany, NJ 07054
-- US
--
-- Phone: +1 973 952-5000
-- EMail: jdrosen@cisco.com
-- URI: http://www.jdrosen.net
--
--
--
--
--
--Rosenberg Informational [Page 16]
--\f
--RFC 4367 Name Assumptions February 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Rosenberg Informational [Page 17]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group S. Josefsson
--Request for Comments: 4398 March 2006
--Obsoletes: 2538
--Category: Standards Track
--
--
-- Storing Certificates in the Domain Name System (DNS)
--
--Status of This Memo
--
-- This document specifies an Internet standards track protocol for the
-- Internet community, and requests discussion and suggestions for
-- improvements. Please refer to the current edition of the "Internet
-- Official Protocol Standards" (STD 1) for the standardization state
-- and status of this protocol. Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- Cryptographic public keys are frequently published, and their
-- authenticity is demonstrated by certificates. A CERT resource record
-- (RR) is defined so that such certificates and related certificate
-- revocation lists can be stored in the Domain Name System (DNS).
--
-- This document obsoletes RFC 2538.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 1]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--Table of Contents
--
-- 1. Introduction ....................................................3
-- 2. The CERT Resource Record ........................................3
-- 2.1. Certificate Type Values ....................................4
-- 2.2. Text Representation of CERT RRs ............................6
-- 2.3. X.509 OIDs .................................................6
-- 3. Appropriate Owner Names for CERT RRs ............................7
-- 3.1. Content-Based X.509 CERT RR Names ..........................8
-- 3.2. Purpose-Based X.509 CERT RR Names ..........................9
-- 3.3. Content-Based OpenPGP CERT RR Names ........................9
-- 3.4. Purpose-Based OpenPGP CERT RR Names .......................10
-- 3.5. Owner Names for IPKIX, ISPKI, IPGP, and IACPKIX ...........10
-- 4. Performance Considerations .....................................11
-- 5. Contributors ...................................................11
-- 6. Acknowledgements ...............................................11
-- 7. Security Considerations ........................................12
-- 8. IANA Considerations ............................................12
-- 9. Changes since RFC 2538 .........................................13
-- 10. References ....................................................14
-- 10.1. Normative References .....................................14
-- 10.2. Informative References ...................................15
-- Appendix A. Copying Conditions ...................................16
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 2]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--1. Introduction
--
-- Public keys are frequently published in the form of a certificate,
-- and their authenticity is commonly demonstrated by certificates and
-- related certificate revocation lists (CRLs). A certificate is a
-- binding, through a cryptographic digital signature, of a public key,
-- a validity interval and/or conditions, and identity, authorization,
-- or other information. A certificate revocation list is a list of
-- certificates that are revoked, and of incidental information, all
-- signed by the signer (issuer) of the revoked certificates. Examples
-- are X.509 certificates/CRLs in the X.500 directory system or OpenPGP
-- certificates/revocations used by OpenPGP software.
--
-- Section 2 specifies a CERT resource record (RR) for the storage of
-- certificates in the Domain Name System [1] [2].
--
-- Section 3 discusses appropriate owner names for CERT RRs.
--
-- Sections 4, 7, and 8 cover performance, security, and IANA
-- considerations, respectively.
--
-- Section 9 explains the changes in this document compared to RFC 2538.
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [3].
--
--2. The CERT Resource Record
--
-- The CERT resource record (RR) has the structure given below. Its RR
-- type code is 37.
--
-- 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
-- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | type | key tag |
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-- | algorithm | /
-- +---------------+ certificate or CRL /
-- / /
-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
--
-- The type field is the certificate type as defined in Section 2.1
-- below.
--
-- The key tag field is the 16-bit value computed for the key embedded
-- in the certificate, using the RRSIG Key Tag algorithm described in
-- Appendix B of [12]. This field is used as an efficiency measure to
--
--
--
--Josefsson Standards Track [Page 3]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- pick which CERT RRs may be applicable to a particular key. The key
-- tag can be calculated for the key in question, and then only CERT RRs
-- with the same key tag need to be examined. Note that two different
-- keys can have the same key tag. However, the key MUST be transformed
-- to the format it would have as the public key portion of a DNSKEY RR
-- before the key tag is computed. This is only possible if the key is
-- applicable to an algorithm and complies to limits (such as key size)
-- defined for DNS security. If it is not, the algorithm field MUST be
-- zero and the tag field is meaningless and SHOULD be zero.
--
-- The algorithm field has the same meaning as the algorithm field in
-- DNSKEY and RRSIG RRs [12], except that a zero algorithm field
-- indicates that the algorithm is unknown to a secure DNS, which may
-- simply be the result of the algorithm not having been standardized
-- for DNSSEC [11].
--
--2.1. Certificate Type Values
--
-- The following values are defined or reserved:
--
-- Value Mnemonic Certificate Type
-- ----- -------- ----------------
-- 0 Reserved
-- 1 PKIX X.509 as per PKIX
-- 2 SPKI SPKI certificate
-- 3 PGP OpenPGP packet
-- 4 IPKIX The URL of an X.509 data object
-- 5 ISPKI The URL of an SPKI certificate
-- 6 IPGP The fingerprint and URL of an OpenPGP packet
-- 7 ACPKIX Attribute Certificate
-- 8 IACPKIX The URL of an Attribute Certificate
-- 9-252 Available for IANA assignment
-- 253 URI URI private
-- 254 OID OID private
-- 255 Reserved
-- 256-65279 Available for IANA assignment
-- 65280-65534 Experimental
-- 65535 Reserved
--
-- These values represent the initial content of the IANA registry; see
-- Section 8.
--
-- The PKIX type is reserved to indicate an X.509 certificate conforming
-- to the profile defined by the IETF PKIX working group [8]. The
-- certificate section will start with a one-octet unsigned OID length
-- and then an X.500 OID indicating the nature of the remainder of the
--
--
--
--
--
--Josefsson Standards Track [Page 4]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- certificate section (see Section 2.3, below). (NOTE: X.509
-- certificates do not include their X.500 directory-type-designating
-- OID as a prefix.)
--
-- The SPKI and ISPKI types are reserved to indicate the SPKI
-- certificate format [15], for use when the SPKI documents are moved
-- from experimental status. The format for these two CERT RR types
-- will need to be specified later.
--
-- The PGP type indicates an OpenPGP packet as described in [5] and its
-- extensions and successors. This is used to transfer public key
-- material and revocation signatures. The data is binary and MUST NOT
-- be encoded into an ASCII armor. An implementation SHOULD process
-- transferable public keys as described in Section 10.1 of [5], but it
-- MAY handle additional OpenPGP packets.
--
-- The ACPKIX type indicates an Attribute Certificate format [9].
--
-- The IPKIX and IACPKIX types indicate a URL that will serve the
-- content that would have been in the "certificate, CRL, or URL" field
-- of the corresponding type (PKIX or ACPKIX, respectively).
--
-- The IPGP type contains both an OpenPGP fingerprint for the key in
-- question, as well as a URL. The certificate portion of the IPGP CERT
-- RR is defined as a one-octet fingerprint length, followed by the
-- OpenPGP fingerprint, followed by the URL. The OpenPGP fingerprint is
-- calculated as defined in RFC 2440 [5]. A zero-length fingerprint or
-- a zero-length URL are legal, and indicate URL-only IPGP data or
-- fingerprint-only IPGP data, respectively. A zero-length fingerprint
-- and a zero-length URL are meaningless and invalid.
--
-- The IPKIX, ISPKI, IPGP, and IACPKIX types are known as "indirect".
-- These types MUST be used when the content is too large to fit in the
-- CERT RR and MAY be used at the implementer's discretion. They SHOULD
-- NOT be used where the DNS message is 512 octets or smaller and could
-- thus be expected to fit a UDP packet.
--
-- The URI private type indicates a certificate format defined by an
-- absolute URI. The certificate portion of the CERT RR MUST begin with
-- a null-terminated URI [10], and the data after the null is the
-- private format certificate itself. The URI SHOULD be such that a
-- retrieval from it will lead to documentation on the format of the
-- certificate. Recognition of private certificate types need not be
-- based on URI equality but can use various forms of pattern matching
-- so that, for example, subtype or version information can also be
-- encoded into the URI.
--
--
--
--
--
--Josefsson Standards Track [Page 5]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- The OID private type indicates a private format certificate specified
-- by an ISO OID prefix. The certificate section will start with a
-- one-octet unsigned OID length and then a BER-encoded OID indicating
-- the nature of the remainder of the certificate section. This can be
-- an X.509 certificate format or some other format. X.509 certificates
-- that conform to the IETF PKIX profile SHOULD be indicated by the PKIX
-- type, not the OID private type. Recognition of private certificate
-- types need not be based on OID equality but can use various forms of
-- pattern matching such as OID prefix.
--
--2.2. Text Representation of CERT RRs
--
-- The RDATA portion of a CERT RR has the type field as an unsigned
-- decimal integer or as a mnemonic symbol as listed in Section 2.1,
-- above.
--
-- The key tag field is represented as an unsigned decimal integer.
--
-- The algorithm field is represented as an unsigned decimal integer or
-- a mnemonic symbol as listed in [12].
--
-- The certificate/CRL portion is represented in base 64 [16] and may be
-- divided into any number of white-space-separated substrings, down to
-- single base-64 digits, which are concatenated to obtain the full
-- signature. These substrings can span lines using the standard
-- parenthesis.
--
-- Note that the certificate/CRL portion may have internal sub-fields,
-- but these do not appear in the master file representation. For
-- example, with type 254, there will be an OID size, an OID, and then
-- the certificate/CRL proper. However, only a single logical base-64
-- string will appear in the text representation.
--
--2.3. X.509 OIDs
--
-- OIDs have been defined in connection with the X.500 directory for
-- user certificates, certification authority certificates, revocations
-- of certification authority, and revocations of user certificates.
-- The following table lists the OIDs, their BER encoding, and their
-- length-prefixed hex format for use in CERT RRs:
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 6]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- id-at-userCertificate
-- = { joint-iso-ccitt(2) ds(5) at(4) 36 }
-- == 0x 03 55 04 24
-- id-at-cACertificate
-- = { joint-iso-ccitt(2) ds(5) at(4) 37 }
-- == 0x 03 55 04 25
-- id-at-authorityRevocationList
-- = { joint-iso-ccitt(2) ds(5) at(4) 38 }
-- == 0x 03 55 04 26
-- id-at-certificateRevocationList
-- = { joint-iso-ccitt(2) ds(5) at(4) 39 }
-- == 0x 03 55 04 27
--
--3. Appropriate Owner Names for CERT RRs
--
-- It is recommended that certificate CERT RRs be stored under a domain
-- name related to their subject, i.e., the name of the entity intended
-- to control the private key corresponding to the public key being
-- certified. It is recommended that certificate revocation list CERT
-- RRs be stored under a domain name related to their issuer.
--
-- Following some of the guidelines below may result in DNS names with
-- characters that require DNS quoting as per Section 5.1 of RFC 1035
-- [2].
--
-- The choice of name under which CERT RRs are stored is important to
-- clients that perform CERT queries. In some situations, the clients
-- may not know all information about the CERT RR object it wishes to
-- retrieve. For example, a client may not know the subject name of an
-- X.509 certificate, or the email address of the owner of an OpenPGP
-- key. Further, the client might only know the hostname of a service
-- that uses X.509 certificates or the Key ID of an OpenPGP key.
--
-- Therefore, two owner name guidelines are defined: content-based owner
-- names and purpose-based owner names. A content-based owner name is
-- derived from the content of the CERT RR data; for example, the
-- Subject field in an X.509 certificate or the User ID field in OpenPGP
-- keys. A purpose-based owner name is a name that a client retrieving
-- CERT RRs ought to know already; for example, the host name of an
-- X.509 protected service or the Key ID of an OpenPGP key. The
-- content-based and purpose-based owner name may be the same; for
-- example, when a client looks up a key based on the From: address of
-- an incoming email.
--
-- Implementations SHOULD use the purpose-based owner name guidelines
-- described in this document and MAY use CNAME RRs at content-based
-- owner names (or other names), pointing to the purpose-based owner
-- name.
--
--
--
--Josefsson Standards Track [Page 7]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- Note that this section describes an application-based mapping from
-- the name space used in a certificate to the name space used by DNS.
-- The DNS does not infer any relationship amongst CERT resource records
-- based on similarities or differences of the DNS owner name(s) of CERT
-- resource records. For example, if multiple labels are used when
-- mapping from a CERT identifier to a domain name, then care must be
-- taken in understanding wildcard record synthesis.
--
--3.1. Content-Based X.509 CERT RR Names
--
-- Some X.509 versions, such as the PKIX profile of X.509 [8], permit
-- multiple names to be associated with subjects and issuers under
-- "Subject Alternative Name" and "Issuer Alternative Name". For
-- example, the PKIX profile has such Alternate Names with an ASN.1
-- specification as follows:
--
-- GeneralName ::= CHOICE {
-- otherName [0] OtherName,
-- rfc822Name [1] IA5String,
-- dNSName [2] IA5String,
-- x400Address [3] ORAddress,
-- directoryName [4] Name,
-- ediPartyName [5] EDIPartyName,
-- uniformResourceIdentifier [6] IA5String,
-- iPAddress [7] OCTET STRING,
-- registeredID [8] OBJECT IDENTIFIER }
--
-- The recommended locations of CERT storage are as follows, in priority
-- order:
--
-- 1. If a domain name is included in the identification in the
-- certificate or CRL, that ought to be used.
-- 2. If a domain name is not included but an IP address is included,
-- then the translation of that IP address into the appropriate
-- inverse domain name ought to be used.
-- 3. If neither of the above is used, but a URI containing a domain
-- name is present, that domain name ought to be used.
-- 4. If none of the above is included but a character string name is
-- included, then it ought to be treated as described below for
-- OpenPGP names.
-- 5. If none of the above apply, then the distinguished name (DN)
-- ought to be mapped into a domain name as specified in [4].
--
-- Example 1: An X.509v3 certificate is issued to /CN=John Doe /DC=Doe/
-- DC=com/DC=xy/O=Doe Inc/C=XY/ with Subject Alternative Names of (a)
-- string "John (the Man) Doe", (b) domain name john-doe.com, and (c)
-- URI <https://www.secure.john-doe.com:8080/>. The storage locations
-- recommended, in priority order, would be
--
--
--
--Josefsson Standards Track [Page 8]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- 1. john-doe.com,
-- 2. www.secure.john-doe.com, and
-- 3. Doe.com.xy.
--
-- Example 2: An X.509v3 certificate is issued to /CN=James Hacker/
-- L=Basingstoke/O=Widget Inc/C=GB/ with Subject Alternate names of (a)
-- domain name widget.foo.example, (b) IPv4 address 10.251.13.201, and
-- (c) string "James Hacker <hacker@mail.widget.foo.example>". The
-- storage locations recommended, in priority order, would be
--
-- 1. widget.foo.example,
-- 2. 201.13.251.10.in-addr.arpa, and
-- 3. hacker.mail.widget.foo.example.
--
--3.2. Purpose-Based X.509 CERT RR Names
--
-- Due to the difficulty for clients that do not already possess a
-- certificate to reconstruct the content-based owner name,
-- purpose-based owner names are recommended in this section.
-- Recommendations for purpose-based owner names vary per scenario. The
-- following table summarizes the purpose-based X.509 CERT RR owner name
-- guidelines for use with S/MIME [17], SSL/TLS [13], and IPsec [14]:
--
-- Scenario Owner name
-- ------------------ ----------------------------------------------
-- S/MIME Certificate Standard translation of an RFC 2822 email
-- address. Example: An S/MIME certificate for
-- "postmaster@example.org" will use a standard
-- hostname translation of the owner name,
-- "postmaster.example.org".
--
-- TLS Certificate Hostname of the TLS server.
--
-- IPsec Certificate Hostname of the IPsec machine and/or, for IPv4
-- or IPv6 addresses, the fully qualified domain
-- name in the appropriate reverse domain.
--
-- An alternate approach for IPsec is to store raw public keys [18].
--
--3.3. Content-Based OpenPGP CERT RR Names
--
-- OpenPGP signed keys (certificates) use a general character string
-- User ID [5]. However, it is recommended by OpenPGP that such names
-- include the RFC 2822 [7] email address of the party, as in "Leslie
-- Example <Leslie@host.example>". If such a format is used, the CERT
-- ought to be under the standard translation of the email address into
--
--
--
--
--
--Josefsson Standards Track [Page 9]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- a domain name, which would be leslie.host.example in this case. If
-- no RFC 2822 name can be extracted from the string name, no specific
-- domain name is recommended.
--
-- If a user has more than one email address, the CNAME type can be used
-- to reduce the amount of data stored in the DNS. For example:
--
-- $ORIGIN example.org.
-- smith IN CERT PGP 0 0 <OpenPGP binary>
-- john.smith IN CNAME smith
-- js IN CNAME smith
--
--3.4. Purpose-Based OpenPGP CERT RR Names
--
-- Applications that receive an OpenPGP packet containing encrypted or
-- signed data but do not know the email address of the sender will have
-- difficulties constructing the correct owner name and cannot use the
-- content-based owner name guidelines. However, these clients commonly
-- know the key fingerprint or the Key ID. The key ID is found in
-- OpenPGP packets, and the key fingerprint is commonly found in
-- auxiliary data that may be available. In this case, use of an owner
-- name identical to the key fingerprint and the key ID expressed in
-- hexadecimal [16] is recommended. For example:
--
-- $ORIGIN example.org.
-- 0424D4EE81A0E3D119C6F835EDA21E94B565716F IN CERT PGP ...
-- F835EDA21E94B565716F IN CERT PGP ...
-- B565716F IN CERT PGP ...
--
-- If the same key material is stored for several owner names, the use
-- of CNAME may help avoid data duplication. Note that CNAME is not
-- always applicable, because it maps one owner name to the other for
-- all purposes, which may be sub-optimal when two keys with the same
-- Key ID are stored.
--
--3.5. Owner Names for IPKIX, ISPKI, IPGP, and IACPKIX
--
-- These types are stored under the same owner names, both purpose- and
-- content-based, as the PKIX, SPKI, PGP, and ACPKIX types.
--
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 10]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--4. Performance Considerations
--
-- The Domain Name System (DNS) protocol was designed for small
-- transfers, typically below 512 octets. While larger transfers will
-- perform correctly and work is underway to make larger transfers more
-- efficient, it is still advisable at this time that every reasonable
-- effort be made to minimize the size of certificates stored within the
-- DNS. Steps that can be taken may include using the fewest possible
-- optional or extension fields and using short field values for
-- necessary variable-length fields.
--
-- The RDATA field in the DNS protocol may only hold data of size 65535
-- octets (64kb) or less. This means that each CERT RR MUST NOT contain
-- more than 64kb of payload, even if the corresponding certificate or
-- certificate revocation list is larger. This document addresses this
-- by defining "indirect" data types for each normal type.
--
-- Deploying CERT RRs to support digitally signed email changes the
-- access patterns of DNS lookups from per-domain to per-user. If
-- digitally signed email and a key/certificate lookup based on CERT RRs
-- are deployed on a wide scale, this may lead to an increased DNS load,
-- with potential performance and cache effectiveness consequences.
-- Whether or not this load increase will be noticeable is not known.
--
--5. Contributors
--
-- The majority of this document is copied verbatim from RFC 2538, by
-- Donald Eastlake 3rd and Olafur Gudmundsson.
--
--6. Acknowledgements
--
-- Thanks to David Shaw and Michael Graff for their contributions to
-- earlier works that motivated, and served as inspiration for, this
-- document.
--
-- This document was improved by suggestions and comments from Olivier
-- Dubuisson, Scott Hollenbeck, Russ Housley, Peter Koch, Olaf M.
-- Kolkman, Ben Laurie, Edward Lewis, John Loughney, Allison Mankin,
-- Douglas Otis, Marcos Sanz, Pekka Savola, Jason Sloderbeck, Samuel
-- Weiler, and Florian Weimer. No doubt the list is incomplete. We
-- apologize to anyone we left out.
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 11]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--7. Security Considerations
--
-- By definition, certificates contain their own authenticating
-- signatures. Thus, it is reasonable to store certificates in
-- non-secure DNS zones or to retrieve certificates from DNS with DNS
-- security checking not implemented or deferred for efficiency. The
-- results may be trusted if the certificate chain is verified back to a
-- known trusted key and this conforms with the user's security policy.
--
-- Alternatively, if certificates are retrieved from a secure DNS zone
-- with DNS security checking enabled and are verified by DNS security,
-- the key within the retrieved certificate may be trusted without
-- verifying the certificate chain if this conforms with the user's
-- security policy.
--
-- If an organization chooses to issue certificates for its employees,
-- placing CERT RRs in the DNS by owner name, and if DNSSEC (with NSEC)
-- is in use, it is possible for someone to enumerate all employees of
-- the organization. This is usually not considered desirable, for the
-- same reason that enterprise phone listings are not often publicly
-- published and are even marked confidential.
--
-- Using the URI type introduces another level of indirection that may
-- open a new vulnerability. One method of securing that indirection is
-- to include a hash of the certificate in the URI itself.
--
-- If DNSSEC is used, then the non-existence of a CERT RR and,
-- consequently, certificates or revocation lists can be securely
-- asserted. Without DNSSEC, this is not possible.
--
--8. IANA Considerations
--
-- The IANA has created a new registry for CERT RR: certificate types.
-- The initial contents of this registry is:
--
-- Decimal Type Meaning Reference
-- ------- ---- ------- ---------
-- 0 Reserved RFC 4398
-- 1 PKIX X.509 as per PKIX RFC 4398
-- 2 SPKI SPKI certificate RFC 4398
-- 3 PGP OpenPGP packet RFC 4398
-- 4 IPKIX The URL of an X.509 data object RFC 4398
-- 5 ISPKI The URL of an SPKI certificate RFC 4398
-- 6 IPGP The fingerprint and URL RFC 4398
-- of an OpenPGP packet
-- 7 ACPKIX Attribute Certificate RFC 4398
-- 8 IACPKIX The URL of an Attribute RFC 4398
-- Certificate
--
--
--
--Josefsson Standards Track [Page 12]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- 9-252 Available for IANA assignment
-- by IETF Standards action
-- 253 URI URI private RFC 4398
-- 254 OID OID private RFC 4398
-- 255 Reserved RFC 4398
-- 256-65279 Available for IANA assignment
-- by IETF Consensus
-- 65280-65534 Experimental RFC 4398
-- 65535 Reserved RFC 4398
--
-- Certificate types 0x0000 through 0x00FF and 0xFF00 through 0xFFFF can
-- only be assigned by an IETF standards action [6]. This document
-- assigns 0x0001 through 0x0008 and 0x00FD and 0x00FE. Certificate
-- types 0x0100 through 0xFEFF are assigned through IETF Consensus [6]
-- based on RFC documentation of the certificate type. The availability
-- of private types under 0x00FD and 0x00FE ought to satisfy most
-- requirements for proprietary or private types.
--
-- The CERT RR reuses the DNS Security Algorithm Numbers registry. In
-- particular, the CERT RR requires that algorithm number 0 remain
-- reserved, as described in Section 2. The IANA will reference the
-- CERT RR as a user of this registry and value 0, in particular.
--
--9. Changes since RFC 2538
--
-- 1. Editorial changes to conform with new document requirements,
-- including splitting reference section into two parts and
-- updating the references to point at latest versions, and to add
-- some additional references.
-- 2. Improve terminology. For example replace "PGP" with "OpenPGP",
-- to align with RFC 2440.
-- 3. In Section 2.1, clarify that OpenPGP public key data are binary,
-- not the ASCII armored format, and reference 10.1 in RFC 2440 on
-- how to deal with OpenPGP keys, and acknowledge that
-- implementations may handle additional packet types.
-- 4. Clarify that integers in the representation format are decimal.
-- 5. Replace KEY/SIG with DNSKEY/RRSIG etc, to align with DNSSECbis
-- terminology. Improve reference for Key Tag Algorithm
-- calculations.
-- 6. Add examples that suggest use of CNAME to reduce bandwidth.
-- 7. In Section 3, appended the last paragraphs that discuss
-- "content-based" vs "purpose-based" owner names. Add Section 3.2
-- for purpose-based X.509 CERT owner names, and Section 3.4 for
-- purpose-based OpenPGP CERT owner names.
-- 8. Added size considerations.
-- 9. The SPKI types has been reserved, until RFC 2692/2693 is moved
-- from the experimental status.
-- 10. Added indirect types IPKIX, ISPKI, IPGP, and IACPKIX.
--
--
--
--Josefsson Standards Track [Page 13]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
-- 11. An IANA registry of CERT type values was created.
--
--10. References
--
--10.1. Normative References
--
-- [1] Mockapetris, P., "Domain names - concepts and facilities",
-- STD 13, RFC 1034, November 1987.
--
-- [2] Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
-- [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
-- [4] Kille, S., Wahl, M., Grimstad, A., Huber, R., and S. Sataluri,
-- "Using Domains in LDAP/X.500 Distinguished Names", RFC 2247,
-- January 1998.
--
-- [5] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,
-- "OpenPGP Message Format", RFC 2440, November 1998.
--
-- [6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
-- Considerations Section in RFCs", BCP 26, RFC 2434,
-- October 1998.
--
-- [7] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
--
-- [8] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509
-- Public Key Infrastructure Certificate and Certificate
-- Revocation List (CRL) Profile", RFC 3280, April 2002.
--
-- [9] Farrell, S. and R. Housley, "An Internet Attribute Certificate
-- Profile for Authorization", RFC 3281, April 2002.
--
-- [10] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
-- Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
-- January 2005.
--
-- [11] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033,
-- March 2005.
--
-- [12] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
--
--
--
--
--Josefsson Standards Track [Page 14]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--10.2. Informative References
--
-- [13] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
-- RFC 2246, January 1999.
--
-- [14] Kent, S. and K. Seo, "Security Architecture for the Internet
-- Protocol", RFC 4301, December 2005.
--
-- [15] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas, B.,
-- and T. Ylonen, "SPKI Certificate Theory", RFC 2693,
-- September 1999.
--
-- [16] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
-- RFC 3548, July 2003.
--
-- [17] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions
-- (S/MIME) Version 3.1 Message Specification", RFC 3851,
-- July 2004.
--
-- [18] Richardson, M., "A Method for Storing IPsec Keying Material in
-- DNS", RFC 4025, March 2005.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 15]
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--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--Appendix A. Copying Conditions
--
-- Regarding the portion of this document that was written by Simon
-- Josefsson ("the author", for the remainder of this section), the
-- author makes no guarantees and is not responsible for any damage
-- resulting from its use. The author grants irrevocable permission to
-- anyone to use, modify, and distribute it in any way that does not
-- diminish the rights of anyone else to use, modify, and distribute it,
-- provided that redistributed derivative works do not contain
-- misleading author or version information. Derivative works need not
-- be licensed under similar terms.
--
--Author's Address
--
-- Simon Josefsson
--
-- EMail: simon@josefsson.org
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 16]
--\f
--RFC 4398 Storing Certificates in the DNS February 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Josefsson Standards Track [Page 17]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group M. Wong
--Request for Comments: 4408 W. Schlitt
--Category: Experimental April 2006
--
--
-- Sender Policy Framework (SPF) for
-- Authorizing Use of Domains in E-Mail, Version 1
--
--Status of This Memo
--
-- This memo defines an Experimental Protocol for the Internet
-- community. It does not specify an Internet standard of any kind.
-- Discussion and suggestions for improvement are requested.
-- Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--IESG Note
--
-- The following documents (RFC 4405, RFC 4406, RFC 4407, and RFC 4408)
-- are published simultaneously as Experimental RFCs, although there is
-- no general technical consensus and efforts to reconcile the two
-- approaches have failed. As such, these documents have not received
-- full IETF review and are published "AS-IS" to document the different
-- approaches as they were considered in the MARID working group.
--
-- The IESG takes no position about which approach is to be preferred
-- and cautions the reader that there are serious open issues for each
-- approach and concerns about using them in tandem. The IESG believes
-- that documenting the different approaches does less harm than not
-- documenting them.
--
-- Note that the Sender ID experiment may use DNS records that may have
-- been created for the current SPF experiment or earlier versions in
-- this set of experiments. Depending on the content of the record,
-- this may mean that Sender-ID heuristics would be applied incorrectly
-- to a message. Depending on the actions associated by the recipient
-- with those heuristics, the message may not be delivered or may be
-- discarded on receipt.
--
-- Participants relying on Sender ID experiment DNS records are warned
-- that they may lose valid messages in this set of circumstances.
-- aParticipants publishing SPF experiment DNS records should consider
-- the advice given in section 3.4 of RFC 4406 and may wish to publish
-- both v=spf1 and spf2.0 records to avoid the conflict.
--
--
--
--
--Wong & Schlitt Experimental [Page 1]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Participants in the Sender-ID experiment need to be aware that the
-- way Resent-* header fields are used will result in failure to receive
-- legitimate email when interacting with standards-compliant systems
-- (specifically automatic forwarders which comply with the standards by
-- not adding Resent-* headers, and systems which comply with RFC 822
-- but have not yet implemented RFC 2822 Resent-* semantics). It would
-- be inappropriate to advance Sender-ID on the standards track without
-- resolving this interoperability problem.
--
-- The community is invited to observe the success or failure of the two
-- approaches during the two years following publication, in order that
-- a community consensus can be reached in the future.
--
--Abstract
--
-- E-mail on the Internet can be forged in a number of ways. In
-- particular, existing protocols place no restriction on what a sending
-- host can use as the reverse-path of a message or the domain given on
-- the SMTP HELO/EHLO commands. This document describes version 1 of
-- the Sender Policy Framework (SPF) protocol, whereby a domain may
-- explicitly authorize the hosts that are allowed to use its domain
-- name, and a receiving host may check such authorization.
--
--Table of Contents
--
-- 1. Introduction ....................................................4
-- 1.1. Protocol Status ............................................4
-- 1.2. Terminology ................................................5
-- 2. Operation .......................................................5
-- 2.1. The HELO Identity ..........................................5
-- 2.2. The MAIL FROM Identity .....................................5
-- 2.3. Publishing Authorization ...................................6
-- 2.4. Checking Authorization .....................................6
-- 2.5. Interpreting the Result ....................................7
-- 2.5.1. None ................................................8
-- 2.5.2. Neutral .............................................8
-- 2.5.3. Pass ................................................8
-- 2.5.4. Fail ................................................8
-- 2.5.5. SoftFail ............................................9
-- 2.5.6. TempError ...........................................9
-- 2.5.7. PermError ...........................................9
-- 3. SPF Records .....................................................9
-- 3.1. Publishing ................................................10
-- 3.1.1. DNS Resource Record Types ..........................10
-- 3.1.2. Multiple DNS Records ...............................11
-- 3.1.3. Multiple Strings in a Single DNS record ............11
-- 3.1.4. Record Size ........................................11
-- 3.1.5. Wildcard Records ...................................11
--
--
--
--Wong & Schlitt Experimental [Page 2]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- 4. The check_host() Function ......................................12
-- 4.1. Arguments .................................................12
-- 4.2. Results ...................................................13
-- 4.3. Initial Processing ........................................13
-- 4.4. Record Lookup .............................................13
-- 4.5. Selecting Records .........................................13
-- 4.6. Record Evaluation .........................................14
-- 4.6.1. Term Evaluation ....................................14
-- 4.6.2. Mechanisms .........................................15
-- 4.6.3. Modifiers ..........................................15
-- 4.7. Default Result ............................................16
-- 4.8. Domain Specification ......................................16
-- 5. Mechanism Definitions ..........................................16
-- 5.1. "all" .....................................................17
-- 5.2. "include" .................................................18
-- 5.3. "a" .......................................................19
-- 5.4. "mx" ......................................................20
-- 5.5. "ptr" .....................................................20
-- 5.6. "ip4" and "ip6" ...........................................21
-- 5.7. "exists" ..................................................22
-- 6. Modifier Definitions ...........................................22
-- 6.1. redirect: Redirected Query ................................23
-- 6.2. exp: Explanation ..........................................23
-- 7. The Received-SPF Header Field ..................................25
-- 8. Macros .........................................................27
-- 8.1. Macro Definitions .........................................27
-- 8.2. Expansion Examples ........................................30
-- 9. Implications ...................................................31
-- 9.1. Sending Domains ...........................................31
-- 9.2. Mailing Lists .............................................32
-- 9.3. Forwarding Services and Aliases ...........................32
-- 9.4. Mail Services .............................................34
-- 9.5. MTA Relays ................................................34
-- 10. Security Considerations .......................................35
-- 10.1. Processing Limits ........................................35
-- 10.2. SPF-Authorized E-Mail May Contain Other False
-- Identities ...............................................37
-- 10.3. Spoofed DNS and IP Data ..................................37
-- 10.4. Cross-User Forgery .......................................37
-- 10.5. Untrusted Information Sources ............................38
-- 10.6. Privacy Exposure .........................................38
-- 11. Contributors and Acknowledgements .............................38
-- 12. IANA Considerations ...........................................39
-- 12.1. The SPF DNS Record Type ..................................39
-- 12.2. The Received-SPF Mail Header Field .......................39
-- 13. References ....................................................39
-- 13.1. Normative References .....................................39
-- 13.2. Informative References ...................................40
--
--
--
--Wong & Schlitt Experimental [Page 3]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Appendix A. Collected ABNF .......................................42
-- Appendix B. Extended Examples ....................................44
-- B.1. Simple Examples ..........................................44
-- B.2. Multiple Domain Example ..................................45
-- B.3. DNSBL Style Example ......................................46
-- B.4. Multiple Requirements Example ............................46
--
--1. Introduction
--
-- The current E-Mail infrastructure has the property that any host
-- injecting mail into the mail system can identify itself as any domain
-- name it wants. Hosts can do this at a variety of levels: in
-- particular, the session, the envelope, and the mail headers.
-- Although this feature is desirable in some circumstances, it is a
-- major obstacle to reducing Unsolicited Bulk E-Mail (UBE, aka spam).
-- Furthermore, many domain name holders are understandably concerned
-- about the ease with which other entities may make use of their domain
-- names, often with malicious intent.
--
-- This document defines a protocol by which domain owners may authorize
-- hosts to use their domain name in the "MAIL FROM" or "HELO" identity.
-- Compliant domain holders publish Sender Policy Framework (SPF)
-- records specifying which hosts are permitted to use their names, and
-- compliant mail receivers use the published SPF records to test the
-- authorization of sending Mail Transfer Agents (MTAs) using a given
-- "HELO" or "MAIL FROM" identity during a mail transaction.
--
-- An additional benefit to mail receivers is that after the use of an
-- identity is verified, local policy decisions about the mail can be
-- made based on the sender's domain, rather than the host's IP address.
-- This is advantageous because reputation of domain names is likely to
-- be more accurate than reputation of host IP addresses. Furthermore,
-- if a claimed identity fails verification, local policy can take
-- stronger action against such E-Mail, such as rejecting it.
--
--1.1. Protocol Status
--
-- SPF has been in development since the summer of 2003 and has seen
-- deployment beyond the developers beginning in December 2003. The
-- design of SPF slowly evolved until the spring of 2004 and has since
-- stabilized. There have been quite a number of forms of SPF, some
-- written up as documents, some submitted as Internet Drafts, and many
-- discussed and debated in development forums.
--
-- The goal of this document is to clearly document the protocol defined
-- by earlier draft specifications of SPF as used in existing
-- implementations. This conception of SPF is sometimes called "SPF
-- Classic". It is understood that particular implementations and
--
--
--
--Wong & Schlitt Experimental [Page 4]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- deployments may differ from, and build upon, this work. It is hoped
-- that we have nonetheless captured the common understanding of SPF
-- version 1.
--
--1.2. Terminology
--
-- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in [RFC2119].
--
-- This document is concerned with the portion of a mail message
-- commonly called "envelope sender", "return path", "reverse path",
-- "bounce address", "2821 FROM", or "MAIL FROM". Since these terms are
-- either not well defined or often used casually, this document defines
-- the "MAIL FROM" identity in Section 2.2. Note that other terms that
-- may superficially look like the common terms, such as "reverse-path",
-- are used only with the defined meanings from normative documents.
--
--2. Operation
--
--2.1. The HELO Identity
--
-- The "HELO" identity derives from either the SMTP HELO or EHLO command
-- (see [RFC2821]). These commands supply the SMTP client (sending
-- host) for the SMTP session. Note that requirements for the domain
-- presented in the EHLO or HELO command are not always clear to the
-- sending party, and SPF clients must be prepared for the "HELO"
-- identity to be malformed or an IP address literal. At the time of
-- this writing, many legitimate E-Mails are delivered with invalid HELO
-- domains.
--
-- It is RECOMMENDED that SPF clients not only check the "MAIL FROM"
-- identity, but also separately check the "HELO" identity by applying
-- the check_host() function (Section 4) to the "HELO" identity as the
-- <sender>.
--
--2.2. The MAIL FROM Identity
--
-- The "MAIL FROM" identity derives from the SMTP MAIL command (see
-- [RFC2821]). This command supplies the "reverse-path" for a message,
-- which generally consists of the sender mailbox, and is the mailbox to
-- which notification messages are to be sent if there are problems
-- delivering the message.
--
-- [RFC2821] allows the reverse-path to be null (see Section 4.5.5 in
-- RFC 2821). In this case, there is no explicit sender mailbox, and
-- such a message can be assumed to be a notification message from the
-- mail system itself. When the reverse-path is null, this document
--
--
--
--Wong & Schlitt Experimental [Page 5]
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--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- defines the "MAIL FROM" identity to be the mailbox composed of the
-- localpart "postmaster" and the "HELO" identity (which may or may not
-- have been checked separately before).
--
-- SPF clients MUST check the "MAIL FROM" identity. SPF clients check
-- the "MAIL FROM" identity by applying the check_host() function to the
-- "MAIL FROM" identity as the <sender>.
--
--2.3. Publishing Authorization
--
-- An SPF-compliant domain MUST publish a valid SPF record as described
-- in Section 3. This record authorizes the use of the domain name in
-- the "HELO" and "MAIL FROM" identities by the MTAs it specifies.
--
-- If domain owners choose to publish SPF records, it is RECOMMENDED
-- that they end in "-all", or redirect to other records that do, so
-- that a definitive determination of authorization can be made.
--
-- Domain holders may publish SPF records that explicitly authorize no
-- hosts if mail should never originate using that domain.
--
-- When changing SPF records, care must be taken to ensure that there is
-- a transition period so that the old policy remains valid until all
-- legitimate E-Mail has been checked.
--
--2.4. Checking Authorization
--
-- A mail receiver can perform a set of SPF checks for each mail message
-- it receives. An SPF check tests the authorization of a client host
-- to emit mail with a given identity. Typically, such checks are done
-- by a receiving MTA, but can be performed elsewhere in the mail
-- processing chain so long as the required information is available and
-- reliable. At least the "MAIL FROM" identity MUST be checked, but it
-- is RECOMMENDED that the "HELO" identity also be checked beforehand.
--
-- Without explicit approval of the domain owner, checking other
-- identities against SPF version 1 records is NOT RECOMMENDED because
-- there are cases that are known to give incorrect results. For
-- example, almost all mailing lists rewrite the "MAIL FROM" identity
-- (see Section 9.2), but some do not change any other identities in the
-- message. The scenario described in Section 9.3, sub-section 1.2, is
-- another example. Documents that define other identities should
-- define the method for explicit approval.
--
-- It is possible that mail receivers will use the SPF check as part of
-- a larger set of tests on incoming mail. The results of other tests
-- may influence whether or not a particular SPF check is performed.
-- For example, finding the sending host's IP address on a local white
--
--
--
--Wong & Schlitt Experimental [Page 6]
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--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- list may cause all other tests to be skipped and all mail from that
-- host to be accepted.
--
-- When a mail receiver decides to perform an SPF check, it MUST use a
-- correctly-implemented check_host() function (Section 4) evaluated
-- with the correct parameters. Although the test as a whole is
-- optional, once it has been decided to perform a test it must be
-- performed as specified so that the correct semantics are preserved
-- between publisher and receiver.
--
-- To make the test, the mail receiver MUST evaluate the check_host()
-- function with the arguments set as follows:
--
-- <ip> - the IP address of the SMTP client that is emitting the
-- mail, either IPv4 or IPv6.
--
-- <domain> - the domain portion of the "MAIL FROM" or "HELO" identity.
--
-- <sender> - the "MAIL FROM" or "HELO" identity.
--
-- Note that the <domain> argument may not be a well-formed domain name.
-- For example, if the reverse-path was null, then the EHLO/HELO domain
-- is used, with its associated problems (see Section 2.1). In these
-- cases, check_host() is defined in Section 4.3 to return a "None"
-- result.
--
-- Although invalid, malformed, or non-existent domains cause SPF checks
-- to return "None" because no SPF record can be found, it has long been
-- the policy of many MTAs to reject E-Mail from such domains,
-- especially in the case of invalid "MAIL FROM". In order to prevent
-- the circumvention of SPF records, rejecting E-Mail from invalid
-- domains should be considered.
--
-- Implementations must take care to correctly extract the <domain> from
-- the data given with the SMTP MAIL FROM command as many MTAs will
-- still accept such things as source routes (see [RFC2821], Appendix
-- C), the %-hack (see [RFC1123]), and bang paths (see [RFC1983]).
-- These archaic features have been maliciously used to bypass security
-- systems.
--
--2.5. Interpreting the Result
--
-- This section describes how software that performs the authorization
-- should interpret the results of the check_host() function. The
-- authorization check SHOULD be performed during the processing of the
-- SMTP transaction that sends the mail. This allows errors to be
-- returned directly to the sending MTA by way of SMTP replies.
--
--
--
--
--Wong & Schlitt Experimental [Page 7]
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--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Performing the authorization after the SMTP transaction has finished
-- may cause problems, such as the following: (1) It may be difficult to
-- accurately extract the required information from potentially
-- deceptive headers; (2) legitimate E-Mail may fail because the
-- sender's policy may have since changed.
--
-- Generating non-delivery notifications to forged identities that have
-- failed the authorization check is generally abusive and against the
-- explicit wishes of the identity owner.
--
--2.5.1. None
--
-- A result of "None" means that no records were published by the domain
-- or that no checkable sender domain could be determined from the given
-- identity. The checking software cannot ascertain whether or not the
-- client host is authorized.
--
--2.5.2. Neutral
--
-- The domain owner has explicitly stated that he cannot or does not
-- want to assert whether or not the IP address is authorized. A
-- "Neutral" result MUST be treated exactly like the "None" result; the
-- distinction exists only for informational purposes. Treating
-- "Neutral" more harshly than "None" would discourage domain owners
-- from testing the use of SPF records (see Section 9.1).
--
--2.5.3. Pass
--
-- A "Pass" result means that the client is authorized to inject mail
-- with the given identity. The domain can now, in the sense of
-- reputation, be considered responsible for sending the message.
-- Further policy checks can now proceed with confidence in the
-- legitimate use of the identity.
--
--2.5.4. Fail
--
-- A "Fail" result is an explicit statement that the client is not
-- authorized to use the domain in the given identity. The checking
-- software can choose to mark the mail based on this or to reject the
-- mail outright.
--
-- If the checking software chooses to reject the mail during the SMTP
-- transaction, then it SHOULD use an SMTP reply code of 550 (see
-- [RFC2821]) and, if supported, the 5.7.1 Delivery Status Notification
-- (DSN) code (see [RFC3464]), in addition to an appropriate reply text.
-- The check_host() function may return either a default explanation
-- string or one from the domain that published the SPF records (see
-- Section 6.2). If the information does not originate with the
--
--
--
--Wong & Schlitt Experimental [Page 8]
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--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- checking software, it should be made clear that the text is provided
-- by the sender's domain. For example:
--
-- 550-5.7.1 SPF MAIL FROM check failed:
-- 550-5.7.1 The domain example.com explains:
-- 550 5.7.1 Please see http://www.example.com/mailpolicy.html
--
--2.5.5. SoftFail
--
-- A "SoftFail" result should be treated as somewhere between a "Fail"
-- and a "Neutral". The domain believes the host is not authorized but
-- is not willing to make that strong of a statement. Receiving
-- software SHOULD NOT reject the message based solely on this result,
-- but MAY subject the message to closer scrutiny than normal.
--
-- The domain owner wants to discourage the use of this host and thus
-- desires limited feedback when a "SoftFail" result occurs. For
-- example, the recipient's Mail User Agent (MUA) could highlight the
-- "SoftFail" status, or the receiving MTA could give the sender a
-- message using a technique called "greylisting" whereby the MTA can
-- issue an SMTP reply code of 451 (4.3.0 DSN code) with a note the
-- first time the message is received, but accept it the second time.
--
--2.5.6. TempError
--
-- A "TempError" result means that the SPF client encountered a
-- transient error while performing the check. Checking software can
-- choose to accept or temporarily reject the message. If the message
-- is rejected during the SMTP transaction for this reason, the software
-- SHOULD use an SMTP reply code of 451 and, if supported, the 4.4.3 DSN
-- code.
--
--2.5.7. PermError
--
-- A "PermError" result means that the domain's published records could
-- not be correctly interpreted. This signals an error condition that
-- requires manual intervention to be resolved, as opposed to the
-- TempError result. Be aware that if the domain owner uses macros
-- (Section 8), it is possible that this result is due to the checked
-- identities having an unexpected format.
--
--3. SPF Records
--
-- An SPF record is a DNS Resource Record (RR) that declares which hosts
-- are, and are not, authorized to use a domain name for the "HELO" and
-- "MAIL FROM" identities. Loosely, the record partitions all hosts
-- into permitted and not-permitted sets (though some hosts might fall
-- into neither category).
--
--
--
--Wong & Schlitt Experimental [Page 9]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- The SPF record is a single string of text. An example record is the
-- following:
--
-- v=spf1 +mx a:colo.example.com/28 -all
--
-- This record has a version of "spf1" and three directives: "+mx",
-- "a:colo.example.com/28" (the + is implied), and "-all".
--
--3.1. Publishing
--
-- Domain owners wishing to be SPF compliant must publish SPF records
-- for the hosts that are used in the "MAIL FROM" and "HELO" identities.
-- The SPF records are placed in the DNS tree at the host name it
-- pertains to, not a subdomain under it, such as is done with SRV
-- records. This is the same whether the TXT or SPF RR type (see
-- Section 3.1.1) is used.
--
-- The example above in Section 3 might be published via these lines in
-- a domain zone file:
--
-- example.com. TXT "v=spf1 +mx a:colo.example.com/28 -all"
-- smtp-out.example.com. TXT "v=spf1 a -all"
--
-- When publishing via TXT records, beware of other TXT records
-- published there for other purposes. They may cause problems with
-- size limits (see Section 3.1.4).
--
--3.1.1. DNS Resource Record Types
--
-- This document defines a new DNS RR of type SPF, code 99. The format
-- of this type is identical to the TXT RR [RFC1035]. For either type,
-- the character content of the record is encoded as [US-ASCII].
--
-- It is recognized that the current practice (using a TXT record) is
-- not optimal, but it is necessary because there are a number of DNS
-- server and resolver implementations in common use that cannot handle
-- the new RR type. The two-record-type scheme provides a forward path
-- to the better solution of using an RR type reserved for this purpose.
--
-- An SPF-compliant domain name SHOULD have SPF records of both RR
-- types. A compliant domain name MUST have a record of at least one
-- type. If a domain has records of both types, they MUST have
-- identical content. For example, instead of publishing just one
-- record as in Section 3.1 above, it is better to publish:
--
-- example.com. IN TXT "v=spf1 +mx a:colo.example.com/28 -all"
-- example.com. IN SPF "v=spf1 +mx a:colo.example.com/28 -all"
--
--
--
--
--Wong & Schlitt Experimental [Page 10]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Example RRs in this document are shown with the TXT record type;
-- however, they could be published with the SPF type or with both
-- types.
--
--3.1.2. Multiple DNS Records
--
-- A domain name MUST NOT have multiple records that would cause an
-- authorization check to select more than one record. See Section 4.5
-- for the selection rules.
--
--3.1.3. Multiple Strings in a Single DNS record
--
-- As defined in [RFC1035] sections 3.3.14 and 3.3, a single text DNS
-- record (either TXT or SPF RR types) can be composed of more than one
-- string. If a published record contains multiple strings, then the
-- record MUST be treated as if those strings are concatenated together
-- without adding spaces. For example:
--
-- IN TXT "v=spf1 .... first" "second string..."
--
-- MUST be treated as equivalent to
--
-- IN TXT "v=spf1 .... firstsecond string..."
--
-- SPF or TXT records containing multiple strings are useful in
-- constructing records that would exceed the 255-byte maximum length of
-- a string within a single TXT or SPF RR record.
--
--3.1.4. Record Size
--
-- The published SPF record for a given domain name SHOULD remain small
-- enough that the results of a query for it will fit within 512 octets.
-- This will keep even older DNS implementations from falling over to
-- TCP. Since the answer size is dependent on many things outside the
-- scope of this document, it is only possible to give this guideline:
-- If the combined length of the DNS name and the text of all the
-- records of a given type (TXT or SPF) is under 450 characters, then
-- DNS answers should fit in UDP packets. Note that when computing the
-- sizes for queries of the TXT format, one must take into account any
-- other TXT records published at the domain name. Records that are too
-- long to fit in a single UDP packet MAY be silently ignored by SPF
-- clients.
--
--3.1.5. Wildcard Records
--
-- Use of wildcard records for publishing is not recommended. Care must
-- be taken if wildcard records are used. If a domain publishes
-- wildcard MX records, it may want to publish wildcard declarations,
--
--
--
--Wong & Schlitt Experimental [Page 11]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- subject to the same requirements and problems. In particular, the
-- declaration must be repeated for any host that has any RR records at
-- all, and for subdomains thereof. For example, the example given in
-- [RFC1034], Section 4.3.3, could be extended with the following:
--
-- X.COM. MX 10 A.X.COM
-- X.COM. TXT "v=spf1 a:A.X.COM -all"
--
-- *.X.COM. MX 10 A.X.COM
-- *.X.COM. TXT "v=spf1 a:A.X.COM -all"
--
-- A.X.COM. A 1.2.3.4
-- A.X.COM. MX 10 A.X.COM
-- A.X.COM. TXT "v=spf1 a:A.X.COM -all"
--
-- *.A.X.COM. MX 10 A.X.COM
-- *.A.X.COM. TXT "v=spf1 a:A.X.COM -all"
--
-- Notice that SPF records must be repeated twice for every name within
-- the domain: once for the name, and once with a wildcard to cover the
-- tree under the name.
--
-- Use of wildcards is discouraged in general as they cause every name
-- under the domain to exist and queries against arbitrary names will
-- never return RCODE 3 (Name Error).
--
--4. The check_host() Function
--
-- The check_host() function fetches SPF records, parses them, and
-- interprets them to determine whether a particular host is or is not
-- permitted to send mail with a given identity. Mail receivers that
-- perform this check MUST correctly evaluate the check_host() function
-- as described here.
--
-- Implementations MAY use a different algorithm than the canonical
-- algorithm defined here, so long as the results are the same in all
-- cases.
--
--4.1. Arguments
--
-- The check_host() function takes these arguments:
--
-- <ip> - the IP address of the SMTP client that is emitting the
-- mail, either IPv4 or IPv6.
--
-- <domain> - the domain that provides the sought-after authorization
-- information; initially, the domain portion of the "MAIL
-- FROM" or "HELO" identity.
--
--
--
--Wong & Schlitt Experimental [Page 12]
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--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- <sender> - the "MAIL FROM" or "HELO" identity.
--
-- The domain portion of <sender> will usually be the same as the
-- <domain> argument when check_host() is initially evaluated. However,
-- this will generally not be true for recursive evaluations (see
-- Section 5.2 below).
--
-- Actual implementations of the check_host() function may need
-- additional arguments.
--
--4.2. Results
--
-- The function check_host() can return one of several results described
-- in Section 2.5. Based on the result, the action to be taken is
-- determined by the local policies of the receiver.
--
--4.3. Initial Processing
--
-- If the <domain> is malformed (label longer than 63 characters, zero-
-- length label not at the end, etc.) or is not a fully qualified domain
-- name, or if the DNS lookup returns "domain does not exist" (RCODE 3),
-- check_host() immediately returns the result "None".
--
-- If the <sender> has no localpart, substitute the string "postmaster"
-- for the localpart.
--
--4.4. Record Lookup
--
-- In accordance with how the records are published (see Section 3.1
-- above), a DNS query needs to be made for the <domain> name, querying
-- for either RR type TXT, SPF, or both. If both SPF and TXT RRs are
-- looked up, the queries MAY be done in parallel.
--
-- If all DNS lookups that are made return a server failure (RCODE 2),
-- or other error (RCODE other than 0 or 3), or time out, then
-- check_host() exits immediately with the result "TempError".
--
--4.5. Selecting Records
--
-- Records begin with a version section:
--
-- record = version terms *SP
-- version = "v=spf1"
--
-- Starting with the set of records that were returned by the lookup,
-- record selection proceeds in two steps:
--
--
--
--
--
--Wong & Schlitt Experimental [Page 13]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- 1. Records that do not begin with a version section of exactly
-- "v=spf1" are discarded. Note that the version section is
-- terminated either by an SP character or the end of the record. A
-- record with a version section of "v=spf10" does not match and must
-- be discarded.
--
-- 2. If any records of type SPF are in the set, then all records of
-- type TXT are discarded.
--
-- After the above steps, there should be exactly one record remaining
-- and evaluation can proceed. If there are two or more records
-- remaining, then check_host() exits immediately with the result of
-- "PermError".
--
-- If no matching records are returned, an SPF client MUST assume that
-- the domain makes no SPF declarations. SPF processing MUST stop and
-- return "None".
--
--4.6. Record Evaluation
--
-- After one SPF record has been selected, the check_host() function
-- parses and interprets it to find a result for the current test. If
-- there are any syntax errors, check_host() returns immediately with
-- the result "PermError".
--
-- Implementations MAY choose to parse the entire record first and
-- return "PermError" if the record is not syntactically well formed.
-- However, in all cases, any syntax errors anywhere in the record MUST
-- be detected.
--
--4.6.1. Term Evaluation
--
-- There are two types of terms: mechanisms and modifiers. A record
-- contains an ordered list of these as specified in the following
-- Augmented Backus-Naur Form (ABNF).
--
-- terms = *( 1*SP ( directive / modifier ) )
--
-- directive = [ qualifier ] mechanism
-- qualifier = "+" / "-" / "?" / "~"
-- mechanism = ( all / include
-- / A / MX / PTR / IP4 / IP6 / exists )
-- modifier = redirect / explanation / unknown-modifier
-- unknown-modifier = name "=" macro-string
--
-- name = ALPHA *( ALPHA / DIGIT / "-" / "_" / "." )
--
-- Most mechanisms allow a ":" or "/" character after the name.
--
--
--
--Wong & Schlitt Experimental [Page 14]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Modifiers always contain an equals ('=') character immediately after
-- the name, and before any ":" or "/" characters that may be part of
-- the macro-string.
--
-- Terms that do not contain any of "=", ":", or "/" are mechanisms, as
-- defined in Section 5.
--
-- As per the definition of the ABNF notation in [RFC4234], mechanism
-- and modifier names are case-insensitive.
--
--4.6.2. Mechanisms
--
-- Each mechanism is considered in turn from left to right. If there
-- are no more mechanisms, the result is specified in Section 4.7.
--
-- When a mechanism is evaluated, one of three things can happen: it can
-- match, not match, or throw an exception.
--
-- If it matches, processing ends and the qualifier value is returned as
-- the result of that record. If it does not match, processing
-- continues with the next mechanism. If it throws an exception,
-- mechanism processing ends and the exception value is returned.
--
-- The possible qualifiers, and the results they return are as follows:
--
-- "+" Pass
-- "-" Fail
-- "~" SoftFail
-- "?" Neutral
--
-- The qualifier is optional and defaults to "+".
--
-- When a mechanism matches and the qualifier is "-", then a "Fail"
-- result is returned and the explanation string is computed as
-- described in Section 6.2.
--
-- The specific mechanisms are described in Section 5.
--
--4.6.3. Modifiers
--
-- Modifiers are not mechanisms: they do not return match or not-match.
-- Instead they provide additional information. Although modifiers do
-- not directly affect the evaluation of the record, the "redirect"
-- modifier has an effect after all the mechanisms have been evaluated.
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 15]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--4.7. Default Result
--
-- If none of the mechanisms match and there is no "redirect" modifier,
-- then the check_host() returns a result of "Neutral", just as if
-- "?all" were specified as the last directive. If there is a
-- "redirect" modifier, check_host() proceeds as defined in Section 6.1.
--
-- Note that records SHOULD always use either a "redirect" modifier or
-- an "all" mechanism to explicitly terminate processing.
--
-- For example:
--
-- v=spf1 +mx -all
-- or
-- v=spf1 +mx redirect=_spf.example.com
--
--4.8. Domain Specification
--
-- Several of these mechanisms and modifiers have a <domain-spec>
-- section. The <domain-spec> string is macro expanded (see Section 8).
-- The resulting string is the common presentation form of a fully-
-- qualified DNS name: a series of labels separated by periods. This
-- domain is called the <target-name> in the rest of this document.
--
-- Note: The result of the macro expansion is not subject to any further
-- escaping. Hence, this facility cannot produce all characters that
-- are legal in a DNS label (e.g., the control characters). However,
-- this facility is powerful enough to express legal host names and
-- common utility labels (such as "_spf") that are used in DNS.
--
-- For several mechanisms, the <domain-spec> is optional. If it is not
-- provided, the <domain> is used as the <target-name>.
--
--5. Mechanism Definitions
--
-- This section defines two types of mechanisms.
--
-- Basic mechanisms contribute to the language framework. They do not
-- specify a particular type of authorization scheme.
--
-- all
-- include
--
-- Designated sender mechanisms are used to designate a set of <ip>
-- addresses as being permitted or not permitted to use the <domain> for
-- sending mail.
--
--
--
--
--
--Wong & Schlitt Experimental [Page 16]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- a
-- mx
-- ptr
-- ip4
-- ip6
-- exists
--
-- The following conventions apply to all mechanisms that perform a
-- comparison between <ip> and an IP address at any point:
--
-- If no CIDR-length is given in the directive, then <ip> and the IP
-- address are compared for equality. (Here, CIDR is Classless Inter-
-- Domain Routing.)
--
-- If a CIDR-length is specified, then only the specified number of
-- high-order bits of <ip> and the IP address are compared for equality.
--
-- When any mechanism fetches host addresses to compare with <ip>, when
-- <ip> is an IPv4 address, A records are fetched, when <ip> is an IPv6
-- address, AAAA records are fetched. Even if the SMTP connection is
-- via IPv6, an IPv4-mapped IPv6 IP address (see [RFC3513], Section
-- 2.5.5) MUST still be considered an IPv4 address.
--
-- Several mechanisms rely on information fetched from DNS. For these
-- DNS queries, except where noted, if the DNS server returns an error
-- (RCODE other than 0 or 3) or the query times out, the mechanism
-- throws the exception "TempError". If the server returns "domain does
-- not exist" (RCODE 3), then evaluation of the mechanism continues as
-- if the server returned no error (RCODE 0) and zero answer records.
--
--5.1. "all"
--
-- all = "all"
--
-- The "all" mechanism is a test that always matches. It is used as the
-- rightmost mechanism in a record to provide an explicit default.
--
-- For example:
--
-- v=spf1 a mx -all
--
-- Mechanisms after "all" will never be tested. Any "redirect" modifier
-- (Section 6.1) has no effect when there is an "all" mechanism.
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 17]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--5.2. "include"
--
-- include = "include" ":" domain-spec
--
-- The "include" mechanism triggers a recursive evaluation of
-- check_host(). The domain-spec is expanded as per Section 8. Then
-- check_host() is evaluated with the resulting string as the <domain>.
-- The <ip> and <sender> arguments remain the same as in the current
-- evaluation of check_host().
--
-- In hindsight, the name "include" was poorly chosen. Only the
-- evaluated result of the referenced SPF record is used, rather than
-- acting as if the referenced SPF record was literally included in the
-- first. For example, evaluating a "-all" directive in the referenced
-- record does not terminate the overall processing and does not
-- necessarily result in an overall "Fail". (Better names for this
-- mechanism would have been "if-pass", "on-pass", etc.)
--
-- The "include" mechanism makes it possible for one domain to designate
-- multiple administratively-independent domains. For example, a vanity
-- domain "example.net" might send mail using the servers of
-- administratively-independent domains example.com and example.org.
--
-- Example.net could say
--
-- IN TXT "v=spf1 include:example.com include:example.org -all"
--
-- This would direct check_host() to, in effect, check the records of
-- example.com and example.org for a "Pass" result. Only if the host
-- were not permitted for either of those domains would the result be
-- "Fail".
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 18]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Whether this mechanism matches, does not match, or throws an
-- exception depends on the result of the recursive evaluation of
-- check_host():
--
-- +---------------------------------+---------------------------------+
-- | A recursive check_host() result | Causes the "include" mechanism |
-- | of: | to: |
-- +---------------------------------+---------------------------------+
-- | Pass | match |
-- | | |
-- | Fail | not match |
-- | | |
-- | SoftFail | not match |
-- | | |
-- | Neutral | not match |
-- | | |
-- | TempError | throw TempError |
-- | | |
-- | PermError | throw PermError |
-- | | |
-- | None | throw PermError |
-- +---------------------------------+---------------------------------+
--
-- The "include" mechanism is intended for crossing administrative
-- boundaries. Although it is possible to use includes to consolidate
-- multiple domains that share the same set of designated hosts, domains
-- are encouraged to use redirects where possible, and to minimize the
-- number of includes within a single administrative domain. For
-- example, if example.com and example.org were managed by the same
-- entity, and if the permitted set of hosts for both domains was
-- "mx:example.com", it would be possible for example.org to specify
-- "include:example.com", but it would be preferable to specify
-- "redirect=example.com" or even "mx:example.com".
--
--5.3. "a"
--
-- This mechanism matches if <ip> is one of the <target-name>'s IP
-- addresses.
--
-- A = "a" [ ":" domain-spec ] [ dual-cidr-length ]
--
-- An address lookup is done on the <target-name>. The <ip> is compared
-- to the returned address(es). If any address matches, the mechanism
-- matches.
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 19]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--5.4. "mx"
--
-- This mechanism matches if <ip> is one of the MX hosts for a domain
-- name.
--
-- MX = "mx" [ ":" domain-spec ] [ dual-cidr-length ]
--
-- check_host() first performs an MX lookup on the <target-name>. Then
-- it performs an address lookup on each MX name returned. The <ip> is
-- compared to each returned IP address. To prevent Denial of Service
-- (DoS) attacks, more than 10 MX names MUST NOT be looked up during the
-- evaluation of an "mx" mechanism (see Section 10). If any address
-- matches, the mechanism matches.
--
-- Note regarding implicit MXs: If the <target-name> has no MX records,
-- check_host() MUST NOT pretend the target is its single MX, and MUST
-- NOT default to an A lookup on the <target-name> directly. This
-- behavior breaks with the legacy "implicit MX" rule. See [RFC2821],
-- Section 5. If such behavior is desired, the publisher should specify
-- an "a" directive.
--
--5.5. "ptr"
--
-- This mechanism tests whether the DNS reverse-mapping for <ip> exists
-- and correctly points to a domain name within a particular domain.
--
-- PTR = "ptr" [ ":" domain-spec ]
--
-- First, the <ip>'s name is looked up using this procedure: perform a
-- DNS reverse-mapping for <ip>, looking up the corresponding PTR record
-- in "in-addr.arpa." if the address is an IPv4 one and in "ip6.arpa."
-- if it is an IPv6 address. For each record returned, validate the
-- domain name by looking up its IP address. To prevent DoS attacks,
-- more than 10 PTR names MUST NOT be looked up during the evaluation of
-- a "ptr" mechanism (see Section 10). If <ip> is among the returned IP
-- addresses, then that domain name is validated. In pseudocode:
--
-- sending-domain_names := ptr_lookup(sending-host_IP); if more than 10
-- sending-domain_names are found, use at most 10. for each name in
-- (sending-domain_names) {
-- IP_addresses := a_lookup(name);
-- if the sending-domain_IP is one of the IP_addresses {
-- validated-sending-domain_names += name;
-- } }
--
-- Check all validated domain names to see if they end in the
-- <target-name> domain. If any do, this mechanism matches. If no
-- validated domain name can be found, or if none of the validated
--
--
--
--Wong & Schlitt Experimental [Page 20]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- domain names end in the <target-name>, this mechanism fails to match.
-- If a DNS error occurs while doing the PTR RR lookup, then this
-- mechanism fails to match. If a DNS error occurs while doing an A RR
-- lookup, then that domain name is skipped and the search continues.
--
-- Pseudocode:
--
-- for each name in (validated-sending-domain_names) {
-- if name ends in <domain-spec>, return match.
-- if name is <domain-spec>, return match.
-- }
-- return no-match.
--
-- This mechanism matches if the <target-name> is either an ancestor of
-- a validated domain name or if the <target-name> and a validated
-- domain name are the same. For example: "mail.example.com" is within
-- the domain "example.com", but "mail.bad-example.com" is not.
--
-- Note: Use of this mechanism is discouraged because it is slow, it is
-- not as reliable as other mechanisms in cases of DNS errors, and it
-- places a large burden on the arpa name servers. If used, proper PTR
-- records must be in place for the domain's hosts and the "ptr"
-- mechanism should be one of the last mechanisms checked.
--
--5.6. "ip4" and "ip6"
--
-- These mechanisms test whether <ip> is contained within a given IP
-- network.
--
-- IP4 = "ip4" ":" ip4-network [ ip4-cidr-length ]
-- IP6 = "ip6" ":" ip6-network [ ip6-cidr-length ]
--
-- ip4-cidr-length = "/" 1*DIGIT
-- ip6-cidr-length = "/" 1*DIGIT
-- dual-cidr-length = [ ip4-cidr-length ] [ "/" ip6-cidr-length ]
--
-- ip4-network = qnum "." qnum "." qnum "." qnum
-- qnum = DIGIT ; 0-9
-- / %x31-39 DIGIT ; 10-99
-- / "1" 2DIGIT ; 100-199
-- / "2" %x30-34 DIGIT ; 200-249
-- / "25" %x30-35 ; 250-255
-- ; as per conventional dotted quad notation. e.g., 192.0.2.0
-- ip6-network = <as per [RFC 3513], section 2.2>
-- ; e.g., 2001:DB8::CD30
--
-- The <ip> is compared to the given network. If CIDR-length high-order
-- bits match, the mechanism matches.
--
--
--
--Wong & Schlitt Experimental [Page 21]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- If ip4-cidr-length is omitted, it is taken to be "/32". If
-- ip6-cidr-length is omitted, it is taken to be "/128". It is not
-- permitted to omit parts of the IP address instead of using CIDR
-- notations. That is, use 192.0.2.0/24 instead of 192.0.2.
--
--5.7. "exists"
--
-- This mechanism is used to construct an arbitrary domain name that is
-- used for a DNS A record query. It allows for complicated schemes
-- involving arbitrary parts of the mail envelope to determine what is
-- permitted.
--
-- exists = "exists" ":" domain-spec
--
-- The domain-spec is expanded as per Section 8. The resulting domain
-- name is used for a DNS A RR lookup. If any A record is returned,
-- this mechanism matches. The lookup type is A even when the
-- connection type is IPv6.
--
-- Domains can use this mechanism to specify arbitrarily complex
-- queries. For example, suppose example.com publishes the record:
--
-- v=spf1 exists:%{ir}.%{l1r+-}._spf.%{d} -all
--
-- The <target-name> might expand to
-- "1.2.0.192.someuser._spf.example.com". This makes fine-grained
-- decisions possible at the level of the user and client IP address.
--
-- This mechanism enables queries that mimic the style of tests that
-- existing anti-spam DNS blacklists (DNSBL) use.
--
--6. Modifier Definitions
--
-- Modifiers are name/value pairs that provide additional information.
-- Modifiers always have an "=" separating the name and the value.
--
-- The modifiers defined in this document ("redirect" and "exp") MAY
-- appear anywhere in the record, but SHOULD appear at the end, after
-- all mechanisms. Ordering of these two modifiers does not matter.
-- These two modifiers MUST NOT appear in a record more than once each.
-- If they do, then check_host() exits with a result of "PermError".
--
-- Unrecognized modifiers MUST be ignored no matter where in a record,
-- or how often. This allows implementations of this document to
-- gracefully handle records with modifiers that are defined in other
-- specifications.
--
--
--
--
--
--Wong & Schlitt Experimental [Page 22]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--6.1. redirect: Redirected Query
--
-- If all mechanisms fail to match, and a "redirect" modifier is
-- present, then processing proceeds as follows:
--
-- redirect = "redirect" "=" domain-spec
--
-- The domain-spec portion of the redirect section is expanded as per
-- the macro rules in Section 8. Then check_host() is evaluated with
-- the resulting string as the <domain>. The <ip> and <sender>
-- arguments remain the same as current evaluation of check_host().
--
-- The result of this new evaluation of check_host() is then considered
-- the result of the current evaluation with the exception that if no
-- SPF record is found, or if the target-name is malformed, the result
-- is a "PermError" rather than "None".
--
-- Note that the newly-queried domain may itself specify redirect
-- processing.
--
-- This facility is intended for use by organizations that wish to apply
-- the same record to multiple domains. For example:
--
-- la.example.com. TXT "v=spf1 redirect=_spf.example.com"
-- ny.example.com. TXT "v=spf1 redirect=_spf.example.com"
-- sf.example.com. TXT "v=spf1 redirect=_spf.example.com"
-- _spf.example.com. TXT "v=spf1 mx:example.com -all"
--
-- In this example, mail from any of the three domains is described by
-- the same record. This can be an administrative advantage.
--
-- Note: In general, the domain "A" cannot reliably use a redirect to
-- another domain "B" not under the same administrative control. Since
-- the <sender> stays the same, there is no guarantee that the record at
-- domain "B" will correctly work for mailboxes in domain "A",
-- especially if domain "B" uses mechanisms involving localparts. An
-- "include" directive may be more appropriate.
--
-- For clarity, it is RECOMMENDED that any "redirect" modifier appear as
-- the very last term in a record.
--
--6.2. exp: Explanation
--
-- explanation = "exp" "=" domain-spec
--
-- If check_host() results in a "Fail" due to a mechanism match (such as
-- "-all"), and the "exp" modifier is present, then the explanation
-- string returned is computed as described below. If no "exp" modifier
--
--
--
--Wong & Schlitt Experimental [Page 23]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- is present, then either a default explanation string or an empty
-- explanation string may be returned.
--
-- The <domain-spec> is macro expanded (see Section 8) and becomes the
-- <target-name>. The DNS TXT record for the <target-name> is fetched.
--
-- If <domain-spec> is empty, or there are any DNS processing errors
-- (any RCODE other than 0), or if no records are returned, or if more
-- than one record is returned, or if there are syntax errors in the
-- explanation string, then proceed as if no exp modifier was given.
--
-- The fetched TXT record's strings are concatenated with no spaces, and
-- then treated as an <explain-string>, which is macro-expanded. This
-- final result is the explanation string. Implementations MAY limit
-- the length of the resulting explanation string to allow for other
-- protocol constraints and/or reasonable processing limits. Since the
-- explanation string is intended for an SMTP response and [RFC2821]
-- Section 2.4 says that responses are in [US-ASCII], the explanation
-- string is also limited to US-ASCII.
--
-- Software evaluating check_host() can use this string to communicate
-- information from the publishing domain in the form of a short message
-- or URL. Software SHOULD make it clear that the explanation string
-- comes from a third party. For example, it can prepend the macro
-- string "%{o} explains: " to the explanation, such as shown in Section
-- 2.5.4.
--
-- Suppose example.com has this record:
--
-- v=spf1 mx -all exp=explain._spf.%{d}
--
-- Here are some examples of possible explanation TXT records at
-- explain._spf.example.com:
--
-- "Mail from example.com should only be sent by its own servers."
-- -- a simple, constant message
--
-- "%{i} is not one of %{d}'s designated mail servers."
-- -- a message with a little more information, including the IP
-- address that failed the check
--
-- "See http://%{d}/why.html?s=%{S}&i=%{I}"
-- -- a complicated example that constructs a URL with the
-- arguments to check_host() so that a web page can be
-- generated with detailed, custom instructions
--
-- Note: During recursion into an "include" mechanism, an exp= modifier
-- from the <target-name> MUST NOT be used. In contrast, when executing
--
--
--
--Wong & Schlitt Experimental [Page 24]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- a "redirect" modifier, an exp= modifier from the original domain MUST
-- NOT be used.
--
--7. The Received-SPF Header Field
--
-- It is RECOMMENDED that SMTP receivers record the result of SPF
-- processing in the message header. If an SMTP receiver chooses to do
-- so, it SHOULD use the "Received-SPF" header field defined here for
-- each identity that was checked. This information is intended for the
-- recipient. (Information intended for the sender is described in
-- Section 6.2, Explanation.)
--
-- The Received-SPF header field is a trace field (see [RFC2822] Section
-- 3.6.7) and SHOULD be prepended to the existing header, above the
-- Received: field that is generated by the SMTP receiver. It MUST
-- appear above all other Received-SPF fields in the message. The
-- header field has the following format:
--
-- header-field = "Received-SPF:" [CFWS] result FWS [comment FWS]
-- [ key-value-list ] CRLF
--
-- result = "Pass" / "Fail" / "SoftFail" / "Neutral" /
-- "None" / "TempError" / "PermError"
--
-- key-value-list = key-value-pair *( ";" [CFWS] key-value-pair )
-- [";"]
--
-- key-value-pair = key [CFWS] "=" ( dot-atom / quoted-string )
--
-- key = "client-ip" / "envelope-from" / "helo" /
-- "problem" / "receiver" / "identity" /
-- mechanism / "x-" name / name
--
-- identity = "mailfrom" ; for the "MAIL FROM" identity
-- / "helo" ; for the "HELO" identity
-- / name ; other identities
--
-- dot-atom = <unquoted word as per [RFC2822]>
-- quoted-string = <quoted string as per [RFC2822]>
-- comment = <comment string as per [RFC2822]>
-- CFWS = <comment or folding white space as per [RFC2822]>
-- FWS = <folding white space as per [RFC2822]>
-- CRLF = <standard end-of-line token as per [RFC2822]>
--
-- The header field SHOULD include a "(...)" style <comment> after the
-- result, conveying supporting information for the result, such as
-- <ip>, <sender>, and <domain>.
--
--
--
--
--Wong & Schlitt Experimental [Page 25]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- The following key-value pairs are designed for later machine parsing.
-- SPF clients SHOULD give enough information so that the SPF results
-- can be verified. That is, at least "client-ip", "helo", and, if the
-- "MAIL FROM" identity was checked, "envelope-from".
--
-- client-ip the IP address of the SMTP client
--
-- envelope-from the envelope sender mailbox
--
-- helo the host name given in the HELO or EHLO command
--
-- mechanism the mechanism that matched (if no mechanisms matched,
-- substitute the word "default")
--
-- problem if an error was returned, details about the error
--
-- receiver the host name of the SPF client
--
-- identity the identity that was checked; see the <identity> ABNF
-- rule
--
-- Other keys may be defined by SPF clients. Until a new key name
-- becomes widely accepted, new key names should start with "x-".
--
-- SPF clients MUST make sure that the Received-SPF header field does
-- not contain invalid characters, is not excessively long, and does not
-- contain malicious data that has been provided by the sender.
--
-- Examples of various header styles that could be generated are the
-- following:
--
-- Received-SPF: Pass (mybox.example.org: domain of
-- myname@example.com designates 192.0.2.1 as permitted sender)
-- receiver=mybox.example.org; client-ip=192.0.2.1;
-- envelope-from=<myname@example.com>; helo=foo.example.com;
--
-- Received-SPF: Fail (mybox.example.org: domain of
-- myname@example.com does not designate
-- 192.0.2.1 as permitted sender)
-- identity=mailfrom; client-ip=192.0.2.1;
-- envelope-from=<myname@example.com>;
--
--
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 26]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--8. Macros
--
--8.1. Macro Definitions
--
-- Many mechanisms and modifiers perform macro expansion on part of the
-- term.
--
-- domain-spec = macro-string domain-end
-- domain-end = ( "." toplabel [ "." ] ) / macro-expand
--
-- toplabel = ( *alphanum ALPHA *alphanum ) /
-- ( 1*alphanum "-" *( alphanum / "-" ) alphanum )
-- ; LDH rule plus additional TLD restrictions
-- ; (see [RFC3696], Section 2)
-- alphanum = ALPHA / DIGIT
--
-- explain-string = *( macro-string / SP )
--
-- macro-string = *( macro-expand / macro-literal )
-- macro-expand = ( "%{" macro-letter transformers *delimiter "}" )
-- / "%%" / "%_" / "%-"
-- macro-literal = %x21-24 / %x26-7E
-- ; visible characters except "%"
-- macro-letter = "s" / "l" / "o" / "d" / "i" / "p" / "h" /
-- "c" / "r" / "t"
-- transformers = *DIGIT [ "r" ]
-- delimiter = "." / "-" / "+" / "," / "/" / "_" / "="
--
-- A literal "%" is expressed by "%%".
--
-- "%_" expands to a single " " space.
-- "%-" expands to a URL-encoded space, viz., "%20".
--
-- The following macro letters are expanded in term arguments:
--
-- s = <sender>
-- l = local-part of <sender>
-- o = domain of <sender>
-- d = <domain>
-- i = <ip>
-- p = the validated domain name of <ip>
-- v = the string "in-addr" if <ip> is ipv4, or "ip6" if <ip> is ipv6
-- h = HELO/EHLO domain
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 27]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- The following macro letters are allowed only in "exp" text:
--
-- c = SMTP client IP (easily readable format)
-- r = domain name of host performing the check
-- t = current timestamp
--
-- A '%' character not followed by a '{', '%', '-', or '_' character is
-- a syntax error. So
--
-- -exists:%(ir).sbl.spamhaus.example.org
--
-- is incorrect and will cause check_host() to return a "PermError".
-- Instead, say
--
-- -exists:%{ir}.sbl.spamhaus.example.org
--
-- Optional transformers are the following:
--
-- *DIGIT = zero or more digits
-- 'r' = reverse value, splitting on dots by default
--
-- If transformers or delimiters are provided, the replacement value for
-- a macro letter is split into parts. After performing any reversal
-- operation and/or removal of left-hand parts, the parts are rejoined
-- using "." and not the original splitting characters.
--
-- By default, strings are split on "." (dots). Note that no special
-- treatment is given to leading, trailing, or consecutive delimiters,
-- and so the list of parts may contain empty strings. Older
-- implementations of SPF prohibit trailing dots in domain names, so
-- trailing dots should not be published by domain owners, although they
-- must be accepted by implementations conforming to this document.
-- Macros may specify delimiter characters that are used instead of ".".
--
-- The 'r' transformer indicates a reversal operation: if the client IP
-- address were 192.0.2.1, the macro %{i} would expand to "192.0.2.1"
-- and the macro %{ir} would expand to "1.2.0.192".
--
-- The DIGIT transformer indicates the number of right-hand parts to
-- use, after optional reversal. If a DIGIT is specified, the value
-- MUST be nonzero. If no DIGITs are specified, or if the value
-- specifies more parts than are available, all the available parts are
-- used. If the DIGIT was 5, and only 3 parts were available, the macro
-- interpreter would pretend the DIGIT was 3. Implementations MUST
-- support at least a value of 128, as that is the maximum number of
-- labels in a domain name.
--
--
--
--
--
--Wong & Schlitt Experimental [Page 28]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- The "s" macro expands to the <sender> argument. It is an E-Mail
-- address with a localpart, an "@" character, and a domain. The "l"
-- macro expands to just the localpart. The "o" macro expands to just
-- the domain part. Note that these values remain the same during
-- recursive and chained evaluations due to "include" and/or "redirect".
-- Note also that if the original <sender> had no localpart, the
-- localpart was set to "postmaster" in initial processing (see Section
-- 4.3).
--
-- For IPv4 addresses, both the "i" and "c" macros expand to the
-- standard dotted-quad format.
--
-- For IPv6 addresses, the "i" macro expands to a dot-format address; it
-- is intended for use in %{ir}. The "c" macro may expand to any of the
-- hexadecimal colon-format addresses specified in [RFC3513], Section
-- 2.2. It is intended for humans to read.
--
-- The "p" macro expands to the validated domain name of <ip>. The
-- procedure for finding the validated domain name is defined in Section
-- 5.5. If the <domain> is present in the list of validated domains, it
-- SHOULD be used. Otherwise, if a subdomain of the <domain> is
-- present, it SHOULD be used. Otherwise, any name from the list may be
-- used. If there are no validated domain names or if a DNS error
-- occurs, the string "unknown" is used.
--
-- The "r" macro expands to the name of the receiving MTA. This SHOULD
-- be a fully qualified domain name, but if one does not exist (as when
-- the checking is done by a MUA) or if policy restrictions dictate
-- otherwise, the word "unknown" SHOULD be substituted. The domain name
-- may be different from the name found in the MX record that the client
-- MTA used to locate the receiving MTA.
--
-- The "t" macro expands to the decimal representation of the
-- approximate number of seconds since the Epoch (Midnight, January 1,
-- 1970, UTC). This is the same value as is returned by the POSIX
-- time() function in most standards-compliant libraries.
--
-- When the result of macro expansion is used in a domain name query, if
-- the expanded domain name exceeds 253 characters (the maximum length
-- of a domain name), the left side is truncated to fit, by removing
-- successive domain labels until the total length does not exceed 253
-- characters.
--
-- Uppercased macros expand exactly as their lowercased equivalents, and
-- are then URL escaped. URL escaping must be performed for characters
-- not in the "uric" set, which is defined in [RFC3986].
--
--
--
--
--
--Wong & Schlitt Experimental [Page 29]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Note: Care must be taken so that macro expansion for legitimate
-- E-Mail does not exceed the 63-character limit on DNS labels. The
-- localpart of E-Mail addresses, in particular, can have more than 63
-- characters between dots.
--
-- Note: Domains should avoid using the "s", "l", "o", or "h" macros in
-- conjunction with any mechanism directive. Although these macros are
-- powerful and allow per-user records to be published, they severely
-- limit the ability of implementations to cache results of check_host()
-- and they reduce the effectiveness of DNS caches.
--
-- Implementations should be aware that if no directive processed during
-- the evaluation of check_host() contains an "s", "l", "o", or "h"
-- macro, then the results of the evaluation can be cached on the basis
-- of <domain> and <ip> alone for as long as the shortest Time To Live
-- (TTL) of all the DNS records involved.
--
--8.2. Expansion Examples
--
-- The <sender> is strong-bad@email.example.com.
-- The IPv4 SMTP client IP is 192.0.2.3.
-- The IPv6 SMTP client IP is 2001:DB8::CB01.
-- The PTR domain name of the client IP is mx.example.org.
--
-- macro expansion
-- ------- ----------------------------
-- %{s} strong-bad@email.example.com
-- %{o} email.example.com
-- %{d} email.example.com
-- %{d4} email.example.com
-- %{d3} email.example.com
-- %{d2} example.com
-- %{d1} com
-- %{dr} com.example.email
-- %{d2r} example.email
-- %{l} strong-bad
-- %{l-} strong.bad
-- %{lr} strong-bad
-- %{lr-} bad.strong
-- %{l1r-} strong
--
--
--
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 30]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- macro-string expansion
-- --------------------------------------------------------------------
-- %{ir}.%{v}._spf.%{d2} 3.2.0.192.in-addr._spf.example.com
-- %{lr-}.lp._spf.%{d2} bad.strong.lp._spf.example.com
--
-- %{lr-}.lp.%{ir}.%{v}._spf.%{d2}
-- bad.strong.lp.3.2.0.192.in-addr._spf.example.com
--
-- %{ir}.%{v}.%{l1r-}.lp._spf.%{d2}
-- 3.2.0.192.in-addr.strong.lp._spf.example.com
--
-- %{d2}.trusted-domains.example.net
-- example.com.trusted-domains.example.net
--
-- IPv6:
-- %{ir}.%{v}._spf.%{d2} 1.0.B.C.0.0.0.0.
-- 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.B.D.0.1.0.0.2.ip6._spf.example.com
--
--9. Implications
--
-- This section outlines the major implications that adoption of this
-- document will have on various entities involved in Internet E-Mail.
-- It is intended to make clear to the reader where this document
-- knowingly affects the operation of such entities. This section is
-- not a "how-to" manual, or a "best practices" document, and it is not
-- a comprehensive list of what such entities should do in light of this
-- document.
--
-- This section is non-normative.
--
--9.1. Sending Domains
--
-- Domains that wish to be compliant with this specification will need
-- to determine the list of hosts that they allow to use their domain
-- name in the "HELO" and "MAIL FROM" identities. It is recognized that
-- forming such a list is not just a simple technical exercise, but
-- involves policy decisions with both technical and administrative
-- considerations.
--
-- It can be helpful to publish records that include a "tracking
-- exists:" mechanism. By looking at the name server logs, a rough list
-- may then be generated. For example:
--
-- v=spf1 exists:_h.%{h}._l.%{l}._o.%{o}._i.%{i}._spf.%{d} ?all
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 31]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--9.2. Mailing Lists
--
-- Mailing lists must be aware of how they re-inject mail that is sent
-- to the list. Mailing lists MUST comply with the requirements in
-- [RFC2821], Section 3.10, and [RFC1123], Section 5.3.6, that say that
-- the reverse-path MUST be changed to be the mailbox of a person or
-- other entity who administers the list. Whereas the reasons for
-- changing the reverse-path are many and long-standing, SPF adds
-- enforcement to this requirement.
--
-- In practice, almost all mailing list software in use already complies
-- with this requirement. Mailing lists that do not comply may or may
-- not encounter problems depending on how access to the list is
-- restricted. Such lists that are entirely internal to a domain (only
-- people in the domain can send to or receive from the list) are not
-- affected.
--
--9.3. Forwarding Services and Aliases
--
-- Forwarding services take mail that is received at a mailbox and
-- direct it to some external mailbox. At the time of this writing, the
-- near-universal practice of such services is to use the original "MAIL
-- FROM" of a message when re-injecting it for delivery to the external
-- mailbox. [RFC1123] and [RFC2821] describe this action as an "alias"
-- rather than a "mail list". This means that the external mailbox's
-- MTA sees all such mail in a connection from a host of the forwarding
-- service, and so the "MAIL FROM" identity will not, in general, pass
-- authorization.
--
-- There are three places that techniques can be used to ameliorate this
-- problem.
--
-- 1. The beginning, when E-Mail is first sent.
--
-- 1. "Neutral" results could be given for IP addresses that may be
-- forwarders, instead of "Fail" results. For example:
--
-- "v=spf1 mx -exists:%{ir}.sbl.spamhaus.example.org ?all"
--
-- This would cause a lookup on an anti-spam DNS blacklist
-- (DNSBL) and cause a result of "Fail" only for E-Mail coming
-- from listed sources. All other E-Mail, including E-Mail sent
-- through forwarders, would receive a "Neutral" result. By
-- checking the DNSBL after the known good sources, problems with
-- incorrect listing on the DNSBL are greatly reduced.
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 32]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- 2. The "MAIL FROM" identity could have additional information in
-- the localpart that cryptographically identifies the mail as
-- coming from an authorized source. In this case, such an SPF
-- record could be used:
--
-- "v=spf1 mx exists:%{l}._spf_verify.%{d} -all"
--
-- Then, a specialized DNS server can be set up to serve the
-- _spf_verify subdomain that validates the localpart. Although
-- this requires an extra DNS lookup, this happens only when the
-- E-Mail would otherwise be rejected as not coming from a known
-- good source.
--
-- Note that due to the 63-character limit for domain labels,
-- this approach only works reliably if the localpart signature
-- scheme is guaranteed either to only produce localparts with a
-- maximum of 63 characters or to gracefully handle truncated
-- localparts.
--
-- 3. Similarly, a specialized DNS server could be set up that will
-- rate-limit the E-Mail coming from unexpected IP addresses.
--
-- "v=spf1 mx exists:%{ir}._spf_rate.%{d} -all"
--
-- 4. SPF allows the creation of per-user policies for special
-- cases. For example, the following SPF record and appropriate
-- wildcard DNS records can be used:
--
-- "v=spf1 mx redirect=%{l1r+}._at_.%{o}._spf.%{d}"
--
-- 2. The middle, when E-Mail is forwarded.
--
-- 1. Forwarding services can solve the problem by rewriting the
-- "MAIL FROM" to be in their own domain. This means that mail
-- bounced from the external mailbox will have to be re-bounced
-- by the forwarding service. Various schemes to do this exist
-- though they vary widely in complexity and resource
-- requirements on the part of the forwarding service.
--
-- 2. Several popular MTAs can be forced from "alias" semantics to
-- "mailing list" semantics by configuring an additional alias
-- with "owner-" prepended to the original alias name (e.g., an
-- alias of "friends: george@example.com, fred@example.org" would
-- need another alias of the form "owner-friends: localowner").
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 33]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- 3. The end, when E-Mail is received.
--
-- 1. If the owner of the external mailbox wishes to trust the
-- forwarding service, he can direct the external mailbox's MTA
-- to skip SPF tests when the client host belongs to the
-- forwarding service.
--
-- 2. Tests against other identities, such as the "HELO" identity,
-- may be used to override a failed test against the "MAIL FROM"
-- identity.
--
-- 3. For larger domains, it may not be possible to have a complete
-- or accurate list of forwarding services used by the owners of
-- the domain's mailboxes. In such cases, whitelists of
-- generally-recognized forwarding services could be employed.
--
--9.4. Mail Services
--
-- Service providers that offer mail services to third-party domains,
-- such as sending of bulk mail, may want to adjust their setup in light
-- of the authorization check described in this document. If the "MAIL
-- FROM" identity used for such E-Mail uses the domain of the service
-- provider, then the provider needs only to ensure that its sending
-- host is authorized by its own SPF record, if any.
--
-- If the "MAIL FROM" identity does not use the mail service provider's
-- domain, then extra care must be taken. The SPF record format has
-- several options for the third-party domain to authorize the service
-- provider's MTAs to send mail on its behalf. For mail service
-- providers, such as ISPs, that have a wide variety of customers using
-- the same MTA, steps should be taken to prevent cross-customer forgery
-- (see Section 10.4).
--
--9.5. MTA Relays
--
-- The authorization check generally precludes the use of arbitrary MTA
-- relays between sender and receiver of an E-Mail message.
--
-- Within an organization, MTA relays can be effectively deployed.
-- However, for purposes of this document, such relays are effectively
-- transparent. The SPF authorization check is a check between border
-- MTAs of different domains.
--
-- For mail senders, this means that published SPF records must
-- authorize any MTAs that actually send across the Internet. Usually,
-- these are just the border MTAs as internal MTAs simply forward mail
-- to these MTAs for delivery.
--
--
--
--
--Wong & Schlitt Experimental [Page 34]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- Mail receivers will generally want to perform the authorization check
-- at the border MTAs, specifically including all secondary MXs. This
-- allows mail that fails to be rejected during the SMTP session rather
-- than bounced. Internal MTAs then do not perform the authorization
-- test. To perform the authorization test other than at the border,
-- the host that first transferred the message to the organization must
-- be determined, which can be difficult to extract from the message
-- header. Testing other than at the border is not recommended.
--
--10. Security Considerations
--
--10.1. Processing Limits
--
-- As with most aspects of E-Mail, there are a number of ways that
-- malicious parties could use the protocol as an avenue for a
-- Denial-of-Service (DoS) attack. The processing limits outlined here
-- are designed to prevent attacks such as the following:
--
-- o A malicious party could create an SPF record with many references
-- to a victim's domain and send many E-Mails to different SPF
-- clients; those SPF clients would then create a DoS attack. In
-- effect, the SPF clients are being used to amplify the attacker's
-- bandwidth by using fewer bytes in the SMTP session than are used
-- by the DNS queries. Using SPF clients also allows the attacker to
-- hide the true source of the attack.
--
-- o Whereas implementations of check_host() are supposed to limit the
-- number of DNS lookups, malicious domains could publish records
-- that exceed these limits in an attempt to waste computation effort
-- at their targets when they send them mail. Malicious domains
-- could also design SPF records that cause particular
-- implementations to use excessive memory or CPU usage, or to
-- trigger bugs.
--
-- o Malicious parties could send a large volume of mail purporting to
-- come from the intended target to a wide variety of legitimate mail
-- hosts. These legitimate machines would then present a DNS load on
-- the target as they fetched the relevant records.
--
-- Of these, the case of a third party referenced in the SPF record is
-- the easiest for a DoS attack to effectively exploit. As a result,
-- limits that may seem reasonable for an individual mail server can
-- still allow an unreasonable amount of bandwidth amplification.
-- Therefore, the processing limits need to be quite low.
--
-- SPF implementations MUST limit the number of mechanisms and modifiers
-- that do DNS lookups to at most 10 per SPF check, including any
-- lookups caused by the use of the "include" mechanism or the
--
--
--
--Wong & Schlitt Experimental [Page 35]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- "redirect" modifier. If this number is exceeded during a check, a
-- PermError MUST be returned. The "include", "a", "mx", "ptr", and
-- "exists" mechanisms as well as the "redirect" modifier do count
-- against this limit. The "all", "ip4", and "ip6" mechanisms do not
-- require DNS lookups and therefore do not count against this limit.
-- The "exp" modifier does not count against this limit because the DNS
-- lookup to fetch the explanation string occurs after the SPF record
-- has been evaluated.
--
-- When evaluating the "mx" and "ptr" mechanisms, or the %{p} macro,
-- there MUST be a limit of no more than 10 MX or PTR RRs looked up and
-- checked.
--
-- SPF implementations SHOULD limit the total amount of data obtained
-- from the DNS queries. For example, when DNS over TCP or EDNS0 are
-- available, there may need to be an explicit limit to how much data
-- will be accepted to prevent excessive bandwidth usage or memory usage
-- and DoS attacks.
--
-- MTAs or other processors MAY also impose a limit on the maximum
-- amount of elapsed time to evaluate check_host(). Such a limit SHOULD
-- allow at least 20 seconds. If such a limit is exceeded, the result
-- of authorization SHOULD be "TempError".
--
-- Domains publishing records SHOULD try to keep the number of "include"
-- mechanisms and chained "redirect" modifiers to a minimum. Domains
-- SHOULD also try to minimize the amount of other DNS information
-- needed to evaluate a record. This can be done by choosing directives
-- that require less DNS information and placing lower-cost mechanisms
-- earlier in the SPF record.
--
-- For example, consider a domain set up as follows:
--
-- example.com. IN MX 10 mx.example.com.
-- mx.example.com. IN A 192.0.2.1
-- a.example.com. IN TXT "v=spf1 mx:example.com -all"
-- b.example.com. IN TXT "v=spf1 a:mx.example.com -all"
-- c.example.com. IN TXT "v=spf1 ip4:192.0.2.1 -all"
--
-- Evaluating check_host() for the domain "a.example.com" requires the
-- MX records for "example.com", and then the A records for the listed
-- hosts. Evaluating for "b.example.com" requires only the A records.
-- Evaluating for "c.example.com" requires none.
--
-- However, there may be administrative considerations: using "a" over
-- "ip4" allows hosts to be renumbered easily. Using "mx" over "a"
-- allows the set of mail hosts to be changed easily.
--
--
--
--
--Wong & Schlitt Experimental [Page 36]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--10.2. SPF-Authorized E-Mail May Contain Other False Identities
--
-- The "MAIL FROM" and "HELO" identity authorizations must not be
-- construed to provide more assurance than they do. It is entirely
-- possible for a malicious sender to inject a message using his own
-- domain in the identities used by SPF, to have that domain's SPF
-- record authorize the sending host, and yet the message can easily
-- list other identities in its header. Unless the user or the MUA
-- takes care to note that the authorized identity does not match the
-- other more commonly-presented identities (such as the From: header
-- field), the user may be lulled into a false sense of security.
--
--10.3. Spoofed DNS and IP Data
--
-- There are two aspects of this protocol that malicious parties could
-- exploit to undermine the validity of the check_host() function:
--
-- o The evaluation of check_host() relies heavily on DNS. A malicious
-- attacker could attack the DNS infrastructure and cause
-- check_host() to see spoofed DNS data, and then return incorrect
-- results. This could include returning "Pass" for an <ip> value
-- where the actual domain's record would evaluate to "Fail". See
-- [RFC3833] for a description of DNS weaknesses.
--
-- o The client IP address, <ip>, is assumed to be correct. A
-- malicious attacker could spoof TCP sequence numbers to make mail
-- appear to come from a permitted host for a domain that the
-- attacker is impersonating.
--
--10.4. Cross-User Forgery
--
-- By definition, SPF policies just map domain names to sets of
-- authorized MTAs, not whole E-Mail addresses to sets of authorized
-- users. Although the "l" macro (Section 8) provides a limited way to
-- define individual sets of authorized MTAs for specific E-Mail
-- addresses, it is generally impossible to verify, through SPF, the use
-- of specific E-Mail addresses by individual users of the same MTA.
--
-- It is up to mail services and their MTAs to directly prevent
-- cross-user forgery: based on SMTP AUTH ([RFC2554]), users should be
-- restricted to using only those E-Mail addresses that are actually
-- under their control (see [RFC4409], Section 6.1). Another means to
-- verify the identity of individual users is message cryptography such
-- as PGP ([RFC2440]) or S/MIME ([RFC3851]).
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 37]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--10.5. Untrusted Information Sources
--
-- SPF uses information supplied by third parties, such as the "HELO"
-- domain name, the "MAIL FROM" address, and SPF records. This
-- information is then passed to the receiver in the Received-SPF: trace
-- fields and possibly returned to the client MTA in the form of an SMTP
-- rejection message. This information must be checked for invalid
-- characters and excessively long lines.
--
-- When the authorization check fails, an explanation string may be
-- included in the reject response. Both the sender and the rejecting
-- receiver need to be aware that the explanation was determined by the
-- publisher of the SPF record checked and, in general, not the
-- receiver. The explanation may contain malicious URLs, or it may be
-- offensive or misleading.
--
-- This is probably less of a concern than it may initially seem since
-- such messages are returned to the sender, and the explanation strings
-- come from the sender policy published by the domain in the identity
-- claimed by that very sender. As long as the DSN is not redirected to
-- someone other than the actual sender, the only people who see
-- malicious explanation strings are people whose messages claim to be
-- from domains that publish such strings in their SPF records. In
-- practice, DSNs can be misdirected, such as when an MTA accepts an
-- E-Mail and then later generates a DSN to a forged address, or when an
-- E-Mail forwarder does not direct the DSN back to the original sender.
--
--10.6. Privacy Exposure
--
-- Checking SPF records causes DNS queries to be sent to the domain
-- owner. These DNS queries, especially if they are caused by the
-- "exists" mechanism, can contain information about who is sending
-- E-Mail and likely to which MTA the E-Mail is being sent. This can
-- introduce some privacy concerns, which may be more or less of an
-- issue depending on local laws and the relationship between the domain
-- owner and the person sending the E-Mail.
--
--11. Contributors and Acknowledgements
--
-- This document is largely based on the work of Meng Weng Wong and Mark
-- Lentczner. Although, as this section acknowledges, many people have
-- contributed to this document, a very large portion of the writing and
-- editing are due to Meng and Mark.
--
-- This design owes a debt of parentage to [RMX] by Hadmut Danisch and
-- to [DMP] by Gordon Fecyk. The idea of using a DNS record to check
-- the legitimacy of an E-Mail address traces its ancestry further back
-- through messages on the namedroppers mailing list by Paul Vixie
--
--
--
--Wong & Schlitt Experimental [Page 38]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- [Vixie] (based on suggestion by Jim Miller) and by David Green
-- [Green].
--
-- Philip Gladstone contributed the concept of macros to the
-- specification, multiplying the expressiveness of the language and
-- making per-user and per-IP lookups possible.
--
-- The authors would also like to thank the literally hundreds of
-- individuals who have participated in the development of this design.
-- They are far too numerous to name, but they include the following:
--
-- The folks on the spf-discuss mailing list.
-- The folks on the SPAM-L mailing list.
-- The folks on the IRTF ASRG mailing list.
-- The folks on the IETF MARID mailing list.
-- The folks on #perl.
--
--12. IANA Considerations
--
--12.1. The SPF DNS Record Type
--
-- The IANA has assigned a new Resource Record Type and Qtype from the
-- DNS Parameters Registry for the SPF RR type with code 99.
--
--12.2. The Received-SPF Mail Header Field
--
-- Per [RFC3864], the "Received-SPF:" header field is added to the IANA
-- Permanent Message Header Field Registry. The following is the
-- registration template:
--
-- Header field name: Received-SPF
-- Applicable protocol: mail ([RFC2822])
-- Status: Experimental
-- Author/Change controller: IETF
-- Specification document(s): RFC 4408
-- Related information:
-- Requesting SPF Council review of any proposed changes and
-- additions to this field are recommended. For information about
-- the SPF Council see http://www.openspf.org/Council
--
--13. References
--
--13.1. Normative References
--
-- [RFC1035] Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
--
--
--
--
--Wong & Schlitt Experimental [Page 39]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- [RFC1123] Braden, R., "Requirements for Internet Hosts - Application
-- and Support", STD 3, RFC 1123, October 1989.
--
-- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
-- Requirement Levels", BCP 14, RFC 2119, March 1997.
--
-- [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
-- April 2001.
--
-- [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
-- 2001.
--
-- [RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format
-- for Delivery Status Notifications", RFC 3464, January
-- 2003.
--
-- [RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6
-- (IPv6) Addressing Architecture", RFC 3513, April 2003.
--
-- [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
-- Procedures for Message Header Fields", BCP 90, RFC 3864,
-- September 2004.
--
-- [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
-- Resource Identifier (URI): Generic Syntax", STD 66, RFC
-- 3986, January 2005.
--
-- [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
-- Specifications: ABNF", RFC 4234, October 2005.
--
-- [US-ASCII] American National Standards Institute (formerly United
-- States of America Standards Institute), "USA Code for
-- Information Interchange, X3.4", 1968.
--
-- ANSI X3.4-1968 has been replaced by newer versions with slight
-- modifications, but the 1968 version remains definitive for
-- the Internet.
--
--13.2 Informative References
--
-- [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
-- STD 13, RFC 1034, November 1987.
--
-- [RFC1983] Malkin, G., "Internet Users' Glossary", RFC 1983, August
-- 1996.
--
-- [RFC2440] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,
-- "OpenPGP Message Format", RFC 2440, November 1998.
--
--
--
--Wong & Schlitt Experimental [Page 40]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- [RFC2554] Myers, J., "SMTP Service Extension for Authentication",
-- RFC 2554, March 1999.
--
-- [RFC3696] Klensin, J., "Application Techniques for Checking and
-- Transformation of Names", RFC 3696, February 2004.
--
-- [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain
-- Name System (DNS)", RFC 3833, August 2004.
--
-- [RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail
-- Extensions (S/MIME) Version 3.1 Message Specification",
-- RFC 3851, July 2004.
--
-- [RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",
-- RFC 4409, April 2006.
--
-- [RMX] Danish, H., "The RMX DNS RR Type for light weight sender
-- authentication", Work In Progress
--
-- [DMP] Fecyk, G., "Designated Mailers Protocol", Work In Progress
--
-- [Vixie] Vixie, P., "Repudiating MAIL FROM", 2002.
--
-- [Green] Green, D., "Domain-Authorized SMTP Mail", 2002.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 41]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--Appendix A. Collected ABNF
--
-- This section is normative and any discrepancies with the ABNF
-- fragments in the preceding text are to be resolved in favor of this
-- grammar.
--
-- See [RFC4234] for ABNF notation. Please note that as per this ABNF
-- definition, literal text strings (those in quotes) are case-
-- insensitive. Hence, "mx" matches "mx", "MX", "mX", and "Mx".
--
-- record = version terms *SP
-- version = "v=spf1"
--
-- terms = *( 1*SP ( directive / modifier ) )
--
-- directive = [ qualifier ] mechanism
-- qualifier = "+" / "-" / "?" / "~"
-- mechanism = ( all / include
-- / A / MX / PTR / IP4 / IP6 / exists )
--
-- all = "all"
-- include = "include" ":" domain-spec
-- A = "a" [ ":" domain-spec ] [ dual-cidr-length ]
-- MX = "mx" [ ":" domain-spec ] [ dual-cidr-length ]
-- PTR = "ptr" [ ":" domain-spec ]
-- IP4 = "ip4" ":" ip4-network [ ip4-cidr-length ]
-- IP6 = "ip6" ":" ip6-network [ ip6-cidr-length ]
-- exists = "exists" ":" domain-spec
--
-- modifier = redirect / explanation / unknown-modifier
-- redirect = "redirect" "=" domain-spec
-- explanation = "exp" "=" domain-spec
-- unknown-modifier = name "=" macro-string
--
-- ip4-cidr-length = "/" 1*DIGIT
-- ip6-cidr-length = "/" 1*DIGIT
-- dual-cidr-length = [ ip4-cidr-length ] [ "/" ip6-cidr-length ]
--
-- ip4-network = qnum "." qnum "." qnum "." qnum
-- qnum = DIGIT ; 0-9
-- / %x31-39 DIGIT ; 10-99
-- / "1" 2DIGIT ; 100-199
-- / "2" %x30-34 DIGIT ; 200-249
-- / "25" %x30-35 ; 250-255
-- ; conventional dotted quad notation. e.g., 192.0.2.0
-- ip6-network = <as per [RFC 3513], section 2.2>
-- ; e.g., 2001:DB8::CD30
--
--
--
--
--Wong & Schlitt Experimental [Page 42]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- domain-spec = macro-string domain-end
-- domain-end = ( "." toplabel [ "." ] ) / macro-expand
-- toplabel = ( *alphanum ALPHA *alphanum ) /
-- ( 1*alphanum "-" *( alphanum / "-" ) alphanum )
-- ; LDH rule plus additional TLD restrictions
-- ; (see [RFC3696], Section 2)
--
-- alphanum = ALPHA / DIGIT
--
-- explain-string = *( macro-string / SP )
--
-- macro-string = *( macro-expand / macro-literal )
-- macro-expand = ( "%{" macro-letter transformers *delimiter "}" )
-- / "%%" / "%_" / "%-"
-- macro-literal = %x21-24 / %x26-7E
-- ; visible characters except "%"
-- macro-letter = "s" / "l" / "o" / "d" / "i" / "p" / "h" /
-- "c" / "r" / "t"
-- transformers = *DIGIT [ "r" ]
-- delimiter = "." / "-" / "+" / "," / "/" / "_" / "="
--
-- name = ALPHA *( ALPHA / DIGIT / "-" / "_" / "." )
--
-- header-field = "Received-SPF:" [CFWS] result FWS [comment FWS]
-- [ key-value-list ] CRLF
--
-- result = "Pass" / "Fail" / "SoftFail" / "Neutral" /
-- "None" / "TempError" / "PermError"
--
-- key-value-list = key-value-pair *( ";" [CFWS] key-value-pair )
-- [";"]
--
-- key-value-pair = key [CFWS] "=" ( dot-atom / quoted-string )
--
-- key = "client-ip" / "envelope-from" / "helo" /
-- "problem" / "receiver" / "identity" /
-- mechanism / "x-" name / name
--
-- identity = "mailfrom" ; for the "MAIL FROM" identity
-- / "helo" ; for the "HELO" identity
-- / name ; other identities
--
-- dot-atom = <unquoted word as per [RFC2822]>
-- quoted-string = <quoted string as per [RFC2822]>
-- comment = <comment string as per [RFC2822]>
-- CFWS = <comment or folding white space as per [RFC2822]>
-- FWS = <folding white space as per [RFC2822]>
-- CRLF = <standard end-of-line token as per [RFC2822]>
--
--
--
--Wong & Schlitt Experimental [Page 43]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--Appendix B. Extended Examples
--
-- These examples are based on the following DNS setup:
--
-- ; A domain with two mail servers, two hosts
-- ; and two servers at the domain name
-- $ORIGIN example.com.
-- @ MX 10 mail-a
-- MX 20 mail-b
-- A 192.0.2.10
-- A 192.0.2.11
-- amy A 192.0.2.65
-- bob A 192.0.2.66
-- mail-a A 192.0.2.129
-- mail-b A 192.0.2.130
-- www CNAME example.com.
--
-- ; A related domain
-- $ORIGIN example.org.
-- @ MX 10 mail-c
-- mail-c A 192.0.2.140
--
-- ; The reverse IP for those addresses
-- $ORIGIN 2.0.192.in-addr.arpa.
-- 10 PTR example.com.
-- 11 PTR example.com.
-- 65 PTR amy.example.com.
-- 66 PTR bob.example.com.
-- 129 PTR mail-a.example.com.
-- 130 PTR mail-b.example.com.
-- 140 PTR mail-c.example.org.
--
-- ; A rogue reverse IP domain that claims to be
-- ; something it's not
-- $ORIGIN 0.0.10.in-addr.arpa.
-- 4 PTR bob.example.com.
--
--B.1. Simple Examples
--
-- These examples show various possible published records for
-- example.com and which values if <ip> would cause check_host() to
-- return "Pass". Note that <domain> is "example.com".
--
-- v=spf1 +all
-- -- any <ip> passes
--
-- v=spf1 a -all
-- -- hosts 192.0.2.10 and 192.0.2.11 pass
--
--
--
--Wong & Schlitt Experimental [Page 44]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
-- v=spf1 a:example.org -all
-- -- no sending hosts pass since example.org has no A records
--
-- v=spf1 mx -all
-- -- sending hosts 192.0.2.129 and 192.0.2.130 pass
--
-- v=spf1 mx:example.org -all
-- -- sending host 192.0.2.140 passes
--
-- v=spf1 mx mx:example.org -all
-- -- sending hosts 192.0.2.129, 192.0.2.130, and 192.0.2.140 pass
--
-- v=spf1 mx/30 mx:example.org/30 -all
-- -- any sending host in 192.0.2.128/30 or 192.0.2.140/30 passes
--
-- v=spf1 ptr -all
-- -- sending host 192.0.2.65 passes (reverse DNS is valid and is in
-- example.com)
-- -- sending host 192.0.2.140 fails (reverse DNS is valid, but not
-- in example.com)
-- -- sending host 10.0.0.4 fails (reverse IP is not valid)
--
-- v=spf1 ip4:192.0.2.128/28 -all
-- -- sending host 192.0.2.65 fails
-- -- sending host 192.0.2.129 passes
--
--B.2. Multiple Domain Example
--
-- These examples show the effect of related records:
--
-- example.org: "v=spf1 include:example.com include:example.net -all"
--
-- This record would be used if mail from example.org actually came
-- through servers at example.com and example.net. Example.org's
-- designated servers are the union of example.com's and example.net's
-- designated servers.
--
-- la.example.org: "v=spf1 redirect=example.org"
-- ny.example.org: "v=spf1 redirect=example.org"
-- sf.example.org: "v=spf1 redirect=example.org"
--
-- These records allow a set of domains that all use the same mail
-- system to make use of that mail system's record. In this way, only
-- the mail system's record needs to be updated when the mail setup
-- changes. These domains' records never have to change.
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 45]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--B.3. DNSBL Style Example
--
-- Imagine that, in addition to the domain records listed above, there
-- are these:
--
-- $ORIGIN _spf.example.com. mary.mobile-users A
-- 127.0.0.2 fred.mobile-users A 127.0.0.2
-- 15.15.168.192.joel.remote-users A 127.0.0.2
-- 16.15.168.192.joel.remote-users A 127.0.0.2
--
-- The following records describe users at example.com who mail from
-- arbitrary servers, or who mail from personal servers.
--
-- example.com:
--
-- v=spf1 mx
-- include:mobile-users._spf.%{d}
-- include:remote-users._spf.%{d}
-- -all
--
-- mobile-users._spf.example.com:
--
-- v=spf1 exists:%{l1r+}.%{d}
--
-- remote-users._spf.example.com:
--
-- v=spf1 exists:%{ir}.%{l1r+}.%{d}
--
--B.4. Multiple Requirements Example
--
-- Say that your sender policy requires both that the IP address is
-- within a certain range and that the reverse DNS for the IP matches.
-- This can be done several ways, including the following:
--
-- example.com. SPF ( "v=spf1 "
-- "-include:ip4._spf.%{d} "
-- "-include:ptr._spf.%{d} "
-- "+all" )
-- ip4._spf.example.com. SPF "v=spf1 -ip4:192.0.2.0/24 +all"
-- ptr._spf.example.com. SPF "v=spf1 -ptr +all"
--
-- This example shows how the "-include" mechanism can be useful, how an
-- SPF record that ends in "+all" can be very restrictive, and the use
-- of De Morgan's Law.
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 46]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--Authors' Addresses
--
-- Meng Weng Wong
-- Singapore
--
-- EMail: mengwong+spf@pobox.com
--
--
-- Wayne Schlitt
-- 4615 Meredeth #9
-- Lincoln Nebraska, NE 68506
-- United States of America
--
-- EMail: wayne@schlitt.net
-- URI: http://www.schlitt.net/spf/
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 47]
--\f
--RFC 4408 Sender Policy Framework (SPF) April 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Wong & Schlitt Experimental [Page 48]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group M. Andrews
--Request for Comments: 4431 Internet Systems Consortium
--Category: Informational S. Weiler
-- SPARTA, Inc.
-- February 2006
--
--
-- The DNSSEC Lookaside Validation (DLV) DNS Resource Record
--
--Status of This Memo
--
-- This memo provides information for the Internet community. It does
-- not specify an Internet standard of any kind. Distribution of this
-- memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document defines a new DNS resource record, called the DNSSEC
-- Lookaside Validation (DLV) RR, for publishing DNSSEC trust anchors
-- outside of the DNS delegation chain.
--
--1. Introduction
--
-- DNSSEC [1] [2] [3] authenticates DNS data by building public-key
-- signature chains along the DNS delegation chain from a trust anchor,
-- ideally a trust anchor for the DNS root.
--
-- This document defines a new resource record for publishing such trust
-- anchors outside of the DNS's normal delegation chain. Use of these
-- records by DNSSEC validators is outside the scope of this document,
-- but it is expected that these records will help resolvers validate
-- DNSSEC-signed data from zones whose ancestors either aren't signed or
-- refuse to publish delegation signer (DS) records for their children.
--
--2. DLV Resource Record
--
-- The DLV resource record has exactly the same wire and presentation
-- formats as the DS resource record, defined in RFC 4034, Section 5.
-- It uses the same IANA-assigned values in the algorithm and digest
-- type fields as the DS record. (Those IANA registries are known as
-- the "DNS Security Algorithm Numbers" and "DS RR Type Algorithm
-- Numbers" registries.)
--
--
--
--
--
--Andrews & Weiler Informational [Page 1]
--\f
--RFC 4431 DLV Resource Record February 2006
--
--
-- The DLV record is a normal DNS record type without any special
-- processing requirements. In particular, the DLV record does not
-- inherit any of the special processing or handling requirements of the
-- DS record type (described in Section 3.1.4.1 of RFC 4035). Unlike
-- the DS record, the DLV record may not appear on the parent's side of
-- a zone cut. A DLV record may, however, appear at the apex of a zone.
--
--3. Security Considerations
--
-- For authoritative servers and resolvers that do not attempt to use
-- DLV RRs as part of DNSSEC validation, there are no particular
-- security concerns -- DLV RRs are just like any other DNS data.
--
-- Software using DLV RRs as part of DNSSEC validation will almost
-- certainly want to impose constraints on their use, but those
-- constraints are best left to be described by the documents that more
-- fully describe the particulars of how the records are used. At a
-- minimum, it would be unwise to use the records without some sort of
-- cryptographic authentication. More likely than not, DNSSEC itself
-- will be used to authenticate the DLV RRs. Depending on how a DLV RR
-- is used, failure to properly authenticate it could lead to
-- significant additional security problems including failure to detect
-- spoofed DNS data.
--
-- RFC 4034, Section 8, describes security considerations specific to
-- the DS RR. Those considerations are equally applicable to DLV RRs.
-- Of particular note, the key tag field is used to help select DNSKEY
-- RRs efficiently, but it does not uniquely identify a single DNSKEY
-- RR. It is possible for two distinct DNSKEY RRs to have the same
-- owner name, the same algorithm type, and the same key tag. An
-- implementation that uses only the key tag to select a DNSKEY RR might
-- select the wrong public key in some circumstances.
--
-- For further discussion of the security implications of DNSSEC, see
-- RFC 4033, RFC 4034, and RFC 4035.
--
--4. IANA Considerations
--
-- IANA has assigned DNS type code 32769 to the DLV resource record from
-- the Specification Required portion of the DNS Resource Record Type
-- registry, as defined in [4].
--
-- The DLV resource record reuses the same algorithm and digest type
-- registries already used for the DS resource record, currently known
-- as the "DNS Security Algorithm Numbers" and "DS RR Type Algorithm
-- Numbers" registries.
--
--
--
--
--
--Andrews & Weiler Informational [Page 2]
--\f
--RFC 4431 DLV Resource Record February 2006
--
--
--5. Normative References
--
-- [1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033,
-- March 2005.
--
-- [2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions",
-- RFC 4035, March 2005.
--
-- [4] Eastlake, D., Brunner-Williams, E., and B. Manning, "Domain Name
-- System (DNS) IANA Considerations", BCP 42, RFC 2929,
-- September 2000.
--
--Authors' Addresses
--
-- Mark Andrews
-- Internet Systems Consortium
-- 950 Charter St.
-- Redwood City, CA 94063
-- US
--
-- EMail: Mark_Andrews@isc.org
--
--
-- Samuel Weiler
-- SPARTA, Inc.
-- 7075 Samuel Morse Drive
-- Columbia, Maryland 21046
-- US
--
-- EMail: weiler@tislabs.com
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Andrews & Weiler Informational [Page 3]
--\f
--RFC 4431 DLV Resource Record February 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Andrews & Weiler Informational [Page 4]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group S. Weiler
--Request for Comments: 4470 SPARTA, Inc.
--Updates: 4035, 4034 J. Ihren
--Category: Standards Track Autonomica AB
-- April 2006
--
--
-- Minimally Covering NSEC Records and DNSSEC On-line Signing
--
--
--Status of This Memo
--
-- This document specifies an Internet standards track protocol for the
-- Internet community, and requests discussion and suggestions for
-- improvements. Please refer to the current edition of the "Internet
-- Official Protocol Standards" (STD 1) for the standardization state
-- and status of this protocol. Distribution of this memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document describes how to construct DNSSEC NSEC resource records
-- that cover a smaller range of names than called for by RFC 4034. By
-- generating and signing these records on demand, authoritative name
-- servers can effectively stop the disclosure of zone contents
-- otherwise made possible by walking the chain of NSEC records in a
-- signed zone.
--
--Table of Contents
--
-- 1. Introduction ....................................................1
-- 2. Applicability of This Technique .................................2
-- 3. Minimally Covering NSEC Records .................................2
-- 4. Better Epsilon Functions ........................................4
-- 5. Security Considerations .........................................5
-- 6. Acknowledgements ................................................6
-- 7. Normative References ............................................6
--
--1. Introduction
--
-- With DNSSEC [1], an NSEC record lists the next instantiated name in
-- its zone, proving that no names exist in the "span" between the
-- NSEC's owner name and the name in the "next name" field. In this
-- document, an NSEC record is said to "cover" the names between its
-- owner name and next name.
--
--
--
--Weiler & Ihren Standards Track [Page 1]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
-- Through repeated queries that return NSEC records, it is possible to
-- retrieve all of the names in the zone, a process commonly called
-- "walking" the zone. Some zone owners have policies forbidding zone
-- transfers by arbitrary clients; this side effect of the NSEC
-- architecture subverts those policies.
--
-- This document presents a way to prevent zone walking by constructing
-- NSEC records that cover fewer names. These records can make zone
-- walking take approximately as many queries as simply asking for all
-- possible names in a zone, making zone walking impractical. Some of
-- these records must be created and signed on demand, which requires
-- on-line private keys. Anyone contemplating use of this technique is
-- strongly encouraged to review the discussion of the risks of on-line
-- signing in Section 5.
--
--1.2. Keywords
--
-- The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-- document are to be interpreted as described in RFC 2119 [4].
--
--2. Applicability of This Technique
--
-- The technique presented here may be useful to a zone owner that wants
-- to use DNSSEC, is concerned about exposure of its zone contents via
-- zone walking, and is willing to bear the costs of on-line signing.
--
-- As discussed in Section 5, on-line signing has several security
-- risks, including an increased likelihood of private keys being
-- disclosed and an increased risk of denial of service attack. Anyone
-- contemplating use of this technique is strongly encouraged to review
-- the discussion of the risks of on-line signing in Section 5.
--
-- Furthermore, at the time this document was published, the DNSEXT
-- working group was actively working on a mechanism to prevent zone
-- walking that does not require on-line signing (tentatively called
-- NSEC3). The new mechanism is likely to expose slightly more
-- information about the zone than this technique (e.g., the number of
-- instantiated names), but it may be preferable to this technique.
--
--3. Minimally Covering NSEC Records
--
-- This mechanism involves changes to NSEC records for instantiated
-- names, which can still be generated and signed in advance, as well as
-- the on-demand generation and signing of new NSEC records whenever a
-- name must be proven not to exist.
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 2]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
-- In the "next name" field of instantiated names' NSEC records, rather
-- than list the next instantiated name in the zone, list any name that
-- falls lexically after the NSEC's owner name and before the next
-- instantiated name in the zone, according to the ordering function in
-- RFC 4034 [2] Section 6.1. This relaxes the requirement in Section
-- 4.1.1 of RFC 4034 that the "next name" field contains the next owner
-- name in the zone. This change is expected to be fully compatible
-- with all existing DNSSEC validators. These NSEC records are returned
-- whenever proving something specifically about the owner name (e.g.,
-- that no resource records of a given type appear at that name).
--
-- Whenever an NSEC record is needed to prove the non-existence of a
-- name, a new NSEC record is dynamically produced and signed. The new
-- NSEC record has an owner name lexically before the QNAME but
-- lexically following any existing name and a "next name" lexically
-- following the QNAME but before any existing name.
--
-- The generated NSEC record's type bitmap MUST have the RRSIG and NSEC
-- bits set and SHOULD NOT have any other bits set. This relaxes the
-- requirement in Section 2.3 of RFC4035 that NSEC RRs not appear at
-- names that did not exist before the zone was signed.
--
-- The functions to generate the lexically following and proceeding
-- names need not be perfect or consistent, but the generated NSEC
-- records must not cover any existing names. Furthermore, this
-- technique works best when the generated NSEC records cover as few
-- names as possible. In this document, the functions that generate the
-- nearby names are called "epsilon" functions, a reference to the
-- mathematical convention of using the greek letter epsilon to
-- represent small deviations.
--
-- An NSEC record denying the existence of a wildcard may be generated
-- in the same way. Since the NSEC record covering a non-existent
-- wildcard is likely to be used in response to many queries,
-- authoritative name servers using the techniques described here may
-- want to pregenerate or cache that record and its corresponding RRSIG.
--
-- For example, a query for an A record at the non-instantiated name
-- example.com might produce the following two NSEC records, the first
-- denying the existence of the name example.com and the second denying
-- the existence of a wildcard:
--
-- exampld.com 3600 IN NSEC example-.com ( RRSIG NSEC )
--
-- \).com 3600 IN NSEC +.com ( RRSIG NSEC )
--
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 3]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
-- Before answering a query with these records, an authoritative server
-- must test for the existence of names between these endpoints. If the
-- generated NSEC would cover existing names (e.g., exampldd.com or
-- *bizarre.example.com), a better epsilon function may be used or the
-- covered name closest to the QNAME could be used as the NSEC owner
-- name or next name, as appropriate. If an existing name is used as
-- the NSEC owner name, that name's real NSEC record MUST be returned.
-- Using the same example, assuming an exampldd.com delegation exists,
-- this record might be returned from the parent:
--
-- exampldd.com 3600 IN NSEC example-.com ( NS DS RRSIG NSEC )
--
-- Like every authoritative record in the zone, each generated NSEC
-- record MUST have corresponding RRSIGs generated using each algorithm
-- (but not necessarily each DNSKEY) in the zone's DNSKEY RRset, as
-- described in RFC 4035 [3] Section 2.2. To minimize the number of
-- signatures that must be generated, a zone may wish to limit the
-- number of algorithms in its DNSKEY RRset.
--
--4. Better Epsilon Functions
--
-- Section 6.1 of RFC 4034 defines a strict ordering of DNS names.
-- Working backward from that definition, it should be possible to
-- define epsilon functions that generate the immediately following and
-- preceding names, respectively. This document does not define such
-- functions. Instead, this section presents functions that come
-- reasonably close to the perfect ones. As described above, an
-- authoritative server should still ensure than no generated NSEC
-- covers any existing name.
--
-- To increment a name, add a leading label with a single null (zero-
-- value) octet.
--
-- To decrement a name, decrement the last character of the leftmost
-- label, then fill that label to a length of 63 octets with octets of
-- value 255. To decrement a null (zero-value) octet, remove the octet
-- -- if an empty label is left, remove the label. Defining this
-- function numerically: fill the leftmost label to its maximum length
-- with zeros (numeric, not ASCII zeros) and subtract one.
--
-- In response to a query for the non-existent name foo.example.com,
-- these functions produce NSEC records of the following:
--
--
--
--
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 4]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
-- fon\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255.example.com 3600 IN NSEC \000.foo.example.com ( NSEC RRSIG )
--
-- \)\255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255
-- \255\255.example.com 3600 IN NSEC \000.*.example.com ( NSEC RRSIG )
--
-- The first of these NSEC RRs proves that no exact match for
-- foo.example.com exists, and the second proves that there is no
-- wildcard in example.com.
--
-- Both of these functions are imperfect: they do not take into account
-- constraints on number of labels in a name nor total length of a name.
-- As noted in the previous section, though, this technique does not
-- depend on the use of perfect epsilon functions: it is sufficient to
-- test whether any instantiated names fall into the span covered by the
-- generated NSEC and, if so, substitute those instantiated owner names
-- for the NSEC owner name or next name, as appropriate.
--
--5. Security Considerations
--
-- This approach requires on-demand generation of RRSIG records. This
-- creates several new vulnerabilities.
--
-- First, on-demand signing requires that a zone's authoritative servers
-- have access to its private keys. Storing private keys on well-known
-- Internet-accessible servers may make them more vulnerable to
-- unintended disclosure.
--
-- Second, since generation of digital signatures tends to be
-- computationally demanding, the requirement for on-demand signing
-- makes authoritative servers vulnerable to a denial of service attack.
--
-- Last, if the epsilon functions are predictable, on-demand signing may
-- enable a chosen-plaintext attack on a zone's private keys. Zones
-- using this approach should attempt to use cryptographic algorithms
-- that are resistant to chosen-plaintext attacks. It is worth noting
-- that although DNSSEC has a "mandatory to implement" algorithm, that
-- is a requirement on resolvers and validators -- there is no
-- requirement that a zone be signed with any given algorithm.
--
-- The success of using minimally covering NSEC records to prevent zone
-- walking depends greatly on the quality of the epsilon functions
--
--
--
--Weiler & Ihren Standards Track [Page 5]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
-- chosen. An increment function that chooses a name obviously derived
-- from the next instantiated name may be easily reverse engineered,
-- destroying the value of this technique. An increment function that
-- always returns a name close to the next instantiated name is likewise
-- a poor choice. Good choices of epsilon functions are the ones that
-- produce the immediately following and preceding names, respectively,
-- though zone administrators may wish to use less perfect functions
-- that return more human-friendly names than the functions described in
-- Section 4 above.
--
-- Another obvious but misguided concern is the danger from synthesized
-- NSEC records being replayed. It is possible for an attacker to
-- replay an old but still validly signed NSEC record after a new name
-- has been added in the span covered by that NSEC, incorrectly proving
-- that there is no record at that name. This danger exists with DNSSEC
-- as defined in [3]. The techniques described here actually decrease
-- the danger, since the span covered by any NSEC record is smaller than
-- before. Choosing better epsilon functions will further reduce this
-- danger.
--
--6. Acknowledgements
--
-- Many individuals contributed to this design. They include, in
-- addition to the authors of this document, Olaf Kolkman, Ed Lewis,
-- Peter Koch, Matt Larson, David Blacka, Suzanne Woolf, Jaap Akkerhuis,
-- Jakob Schlyter, Bill Manning, and Joao Damas.
--
-- In addition, the editors would like to thank Ed Lewis, Scott Rose,
-- and David Blacka for their careful review of the document.
--
--7. Normative References
--
-- [1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033, March
-- 2005.
--
-- [2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions", RFC
-- 4035, March 2005.
--
-- [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 6]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
--Authors' Addresses
--
-- Samuel Weiler
-- SPARTA, Inc.
-- 7075 Samuel Morse Drive
-- Columbia, Maryland 21046
-- US
--
-- EMail: weiler@tislabs.com
--
--
-- Johan Ihren
-- Autonomica AB
-- Bellmansgatan 30
-- Stockholm SE-118 47
-- Sweden
--
-- EMail: johani@autonomica.se
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 7]
--\f
--RFC 4470 NSEC Epsilon April 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Weiler & Ihren Standards Track [Page 8]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group D. Eastlake 3rd
--Request for Comments: 4634 Motorola Labs
--Updates: 3174 T. Hansen
--Category: Informational AT&T Labs
-- July 2006
--
--
-- US Secure Hash Algorithms (SHA and HMAC-SHA)
--
--Status of This Memo
--
-- This memo provides information for the Internet community. It does
-- not specify an Internet standard of any kind. Distribution of this
-- memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- The United States of America has adopted a suite of Secure Hash
-- Algorithms (SHAs), including four beyond SHA-1, as part of a Federal
-- Information Processing Standard (FIPS), specifically SHA-224 (RFC
-- 3874), SHA-256, SHA-384, and SHA-512. The purpose of this document
-- is to make source code performing these hash functions conveniently
-- available to the Internet community. The sample code supports input
-- strings of arbitrary bit length. SHA-1's sample code from RFC 3174
-- has also been updated to handle input strings of arbitrary bit
-- length. Most of the text herein was adapted by the authors from FIPS
-- 180-2.
--
-- Code to perform SHA-based HMACs, with arbitrary bit length text, is
-- also included.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 1]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--Table of Contents
--
-- 1. Overview of Contents ............................................3
-- 1.1. License ....................................................4
-- 2. Notation for Bit Strings and Integers ...........................4
-- 3. Operations on Words .............................................5
-- 4. Message Padding and Parsing .....................................6
-- 4.1. SHA-224 and SHA-256 ........................................7
-- 4.2. SHA-384 and SHA-512 ........................................8
-- 5. Functions and Constants Used ....................................9
-- 5.1. SHA-224 and SHA-256 ........................................9
-- 5.2. SHA-384 and SHA-512 .......................................10
-- 6. Computing the Message Digest ...................................11
-- 6.1. SHA-224 and SHA-256 Initialization ........................11
-- 6.2. SHA-224 and SHA-256 Processing ............................11
-- 6.3. SHA-384 and SHA-512 Initialization ........................13
-- 6.4. SHA-384 and SHA-512 Processing ............................14
-- 7. SHA-Based HMACs ................................................15
-- 8. C Code for SHAs ................................................15
-- 8.1. The .h File ...............................................18
-- 8.2. The SHA Code ..............................................24
-- 8.2.1. sha1.c .............................................24
-- 8.2.2. sha224-256.c .......................................33
-- 8.2.3. sha384-512.c .......................................45
-- 8.2.4. usha.c .............................................67
-- 8.2.5. sha-private.h ......................................72
-- 8.3. The HMAC Code .............................................73
-- 8.4. The Test Driver ...........................................78
-- 9. Security Considerations .......................................106
-- 10. Normative References .........................................106
-- 11. Informative References .......................................106
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 2]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--1. Overview of Contents
--
-- NOTE: Much of the text below is taken from [FIPS180-2] and assertions
-- therein of the security of the algorithms described are made by the
-- US Government, the author of [FIPS180-2], and not by the authors of
-- this document.
--
-- The text below specifies Secure Hash Algorithms, SHA-224 [RFC3874],
-- SHA-256, SHA-384, and SHA-512, for computing a condensed
-- representation of a message or a data file. (SHA-1 is specified in
-- [RFC3174].) When a message of any length < 2^64 bits (for SHA-224
-- and SHA-256) or < 2^128 bits (for SHA-384 and SHA-512) is input to
-- one of these algorithms, the result is an output called a message
-- digest. The message digests range in length from 224 to 512 bits,
-- depending on the algorithm. Secure hash algorithms are typically
-- used with other cryptographic algorithms, such as digital signature
-- algorithms and keyed hash authentication codes, or in the generation
-- of random numbers [RFC4086].
--
-- The four algorithms specified in this document are called secure
-- because it is computationally infeasible to (1) find a message that
-- corresponds to a given message digest, or (2) find two different
-- messages that produce the same message digest. Any change to a
-- message in transit will, with very high probability, result in a
-- different message digest. This will result in a verification failure
-- when the secure hash algorithm is used with a digital signature
-- algorithm or a keyed-hash message authentication algorithm.
--
-- The code provided herein supports input strings of arbitrary bit
-- length. SHA-1's sample code from [RFC3174] has also been updated to
-- handle input strings of arbitrary bit length. See Section 1.1 for
-- license information for this code.
--
-- Section 2 below defines the terminology and functions used as
-- building blocks to form these algorithms. Section 3 describes the
-- fundamental operations on words from which these algorithms are
-- built. Section 4 describes how messages are padded up to an integral
-- multiple of the required block size and then parsed into blocks.
-- Section 5 defines the constants and the composite functions used to
-- specify these algorithms. Section 6 gives the actual specification
-- for the SHA-224, SHA-256, SHA-384, and SHA-512 functions. Section 7
-- provides pointers to the specification of HMAC keyed message
-- authentication codes based on the SHA algorithms. Section 8 gives
-- sample code for the SHA algorithms and Section 9 code for SHA-based
-- HMACs. The SHA-based HMACs will accept arbitrary bit length text.
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 3]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--1.1. License
--
-- Permission is granted for all uses, commercial and non-commercial, of
-- the sample code found in Section 8. Royalty free license to use,
-- copy, modify and distribute the software found in Section 8 is
-- granted, provided that this document is identified in all material
-- mentioning or referencing this software, and provided that
-- redistributed derivative works do not contain misleading author or
-- version information.
--
-- The authors make no representations concerning either the
-- merchantability of this software or the suitability of this software
-- for any particular purpose. It is provided "as is" without express
-- or implied warranty of any kind.
--
--2. Notation for Bit Strings and Integers
--
-- The following terminology related to bit strings and integers will be
-- used:
--
-- a. A hex digit is an element of the set {0, 1, ... , 9, A, ... ,
-- F}. A hex digit is the representation of a 4-bit string.
-- Examples: 7 = 0111, A = 1010.
--
-- b. A word equals a 32-bit or 64-bit string, which may be
-- represented as a sequence of 8 or 16 hex digits, respectively.
-- To convert a word to hex digits, each 4-bit string is converted
-- to its hex equivalent as described in (a) above. Example:
--
-- 1010 0001 0000 0011 1111 1110 0010 0011 = A103FE23.
--
-- Throughout this document, the "big-endian" convention is used
-- when expressing both 32-bit and 64-bit words, so that within
-- each word the most significant bit is shown in the left-most bit
-- position.
--
-- c. An integer may be represented as a word or pair of words.
--
-- An integer between 0 and 2^32 - 1 inclusive may be represented
-- as a 32-bit word. The least significant four bits of the
-- integer are represented by the right-most hex digit of the word
-- representation. Example: the integer 291 = 2^8+2^5+2^1+2^0 =
-- 256+32+2+1 is represented by the hex word 00000123.
--
-- The same holds true for an integer between 0 and 2^64-1
-- inclusive, which may be represented as a 64-bit word.
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 4]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- If Z is an integer, 0 <= z < 2^64, then z = (2^32)x + y where 0
-- <= x < 2^32 and 0 <= y < 2^32. Since x and y can be represented
-- as words X and Y, respectively, z can be represented as the pair
-- of words (X,Y).
--
-- d. block = 512-bit or 1024-bit string. A block (e.g., B) may be
-- represented as a sequence of 32-bit or 64-bit words.
--
--3. Operations on Words
--
-- The following logical operators will be applied to words in all four
-- hash operations specified herein. SHA-224 and SHA-256 operate on
-- 32-bit words, while SHA-384 and SHA-512 operate on 64-bit words.
--
-- In the operations below, x<<n is obtained as follows: discard the
-- left-most n bits of x and then pad the result with n zeroed bits on
-- the right (the result will still be the same number of bits).
--
-- a. Bitwise logical word operations
--
-- X AND Y = bitwise logical "and" of X and Y.
--
-- X OR Y = bitwise logical "inclusive-or" of X and Y.
--
-- X XOR Y = bitwise logical "exclusive-or" of X and Y.
--
-- NOT X = bitwise logical "complement" of X.
--
-- Example:
-- 01101100101110011101001001111011
-- XOR 01100101110000010110100110110111
-- --------------------------------
-- = 00001001011110001011101111001100
--
-- b. The operation X + Y is defined as follows: words X and Y
-- represent w-bit integers x and y, where 0 <= x < 2^w and
-- 0 <= y < 2^w. For positive integers n and m, let
--
-- n mod m
--
-- be the remainder upon dividing n by m. Compute
--
-- z = (x + y) mod 2^w.
--
-- Then 0 <= z < 2^w. Convert z to a word, Z, and define Z = X +
-- Y.
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 5]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- c. The right shift operation SHR^n(x), where x is a w-bit word and
-- n is an integer with 0 <= n < w, is defined by
--
-- SHR^n(x) = x>>n
--
-- d. The rotate right (circular right shift) operation ROTR^n(x),
-- where x is a w-bit word and n is an integer with 0 <= n < w, is
-- defined by
--
-- ROTR^n(x) = (x>>n) OR (x<<(w-n))
--
-- e. The rotate left (circular left shift) operation ROTL^n(x), where
-- x is a w-bit word and n is an integer with 0 <= n < w, is
-- defined by
--
-- ROTL^n(X) = (x<<n) OR (x>>w-n)
--
-- Note the following equivalence relationships, where w is fixed
-- in each relationship:
--
-- ROTL^n(x) = ROTR^(w-x)(x)
--
-- ROTR^n(x) = ROTL^(w-n)(x)
--
--4. Message Padding and Parsing
--
-- The hash functions specified herein are used to compute a message
-- digest for a message or data file that is provided as input. The
-- message or data file should be considered to be a bit string. The
-- length of the message is the number of bits in the message (the empty
-- message has length 0). If the number of bits in a message is a
-- multiple of 8, for compactness we can represent the message in hex.
-- The purpose of message padding is to make the total length of a
-- padded message a multiple of 512 for SHA-224 and SHA-256 or a
-- multiple of 1024 for SHA-384 and SHA-512.
--
-- The following specifies how this padding shall be performed. As a
-- summary, a "1" followed by a number of "0"s followed by a 64-bit or
-- 128-bit integer are appended to the end of the message to produce a
-- padded message of length 512*n or 1024*n. The minimum number of "0"s
-- necessary to meet this criterion is used. The appended integer is
-- the length of the original message. The padded message is then
-- processed by the hash function as n 512-bit or 1024-bit blocks.
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 6]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--4.1. SHA-224 and SHA-256
--
-- Suppose a message has length L < 2^64. Before it is input to the
-- hash function, the message is padded on the right as follows:
--
-- a. "1" is appended. Example: if the original message is
-- "01010000", this is padded to "010100001".
--
-- b. K "0"s are appended where K is the smallest, non-negative
-- solution to the equation
--
-- L + 1 + K = 448 (mod 512)
--
-- c. Then append the 64-bit block that is L in binary representation.
-- After appending this block, the length of the message will be a
-- multiple of 512 bits.
--
-- Example: Suppose the original message is the bit string
--
-- 01100001 01100010 01100011 01100100 01100101
--
-- After step (a), this gives
--
-- 01100001 01100010 01100011 01100100 01100101 1
--
-- Since L = 40, the number of bits in the above is 41 and K = 407
-- "0"s are appended, making the total now 448. This gives the
-- following in hex:
--
-- 61626364 65800000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000
--
-- The 64-bit representation of L = 40 is hex 00000000 00000028.
-- Hence the final padded message is the following hex:
--
-- 61626364 65800000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000028
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 7]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--4.2. SHA-384 and SHA-512
--
-- Suppose a message has length L < 2^128. Before it is input to the
-- hash function, the message is padded on the right as follows:
--
-- a. "1" is appended. Example: if the original message is
-- "01010000", this is padded to "010100001".
--
-- b. K "0"s are appended where K is the smallest, non-negative
-- solution to the equation
--
-- L + 1 + K = 896 (mod 1024)
--
-- c. Then append the 128-bit block that is L in binary
-- representation. After appending this block, the length of the
-- message will be a multiple of 1024 bits.
--
-- Example: Suppose the original message is the bit string
--
-- 01100001 01100010 01100011 01100100 01100101
--
-- After step (a) this gives
--
-- 01100001 01100010 01100011 01100100 01100101 1
--
-- Since L = 40, the number of bits in the above is 41 and K = 855
-- "0"s are appended, making the total now 896. This gives the
-- following in hex:
--
-- 61626364 65800000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
--
-- The 128-bit representation of L = 40 is hex 00000000 00000000
-- 00000000 00000028. Hence the final padded message is the
-- following hex:
--
-- 61626364 65800000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 8]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000000
-- 00000000 00000000 00000000 00000028
--
--5. Functions and Constants Used
--
-- The following subsections give the six logical functions and the
-- table of constants used in each of the hash functions.
--
--5.1. SHA-224 and SHA-256
--
-- SHA-224 and SHA-256 use six logical functions, where each function
-- operates on 32-bit words, which are represented as x, y, and z. The
-- result of each function is a new 32-bit word.
--
-- CH( x, y, z) = (x AND y) XOR ( (NOT x) AND z)
--
-- MAJ( x, y, z) = (x AND y) XOR (x AND z) XOR (y AND z)
--
-- BSIG0(x) = ROTR^2(x) XOR ROTR^13(x) XOR ROTR^22(x)
--
-- BSIG1(x) = ROTR^6(x) XOR ROTR^11(x) XOR ROTR^25(x)
--
-- SSIG0(x) = ROTR^7(x) XOR ROTR^18(x) XOR SHR^3(x)
--
-- SSIG1(x) = ROTR^17(x) XOR ROTR^19(x) XOR SHR^10(x)
--
-- SHA-224 and SHA-256 use the same sequence of sixty-four constant
-- 32-bit words, K0, K1, ..., K63. These words represent the first
-- thirty-two bits of the fractional parts of the cube roots of the
-- first sixty-four prime numbers. In hex, these constant words are as
-- follows (from left to right):
--
-- 428a2f98 71374491 b5c0fbcf e9b5dba5
-- 3956c25b 59f111f1 923f82a4 ab1c5ed5
-- d807aa98 12835b01 243185be 550c7dc3
-- 72be5d74 80deb1fe 9bdc06a7 c19bf174
-- e49b69c1 efbe4786 0fc19dc6 240ca1cc
-- 2de92c6f 4a7484aa 5cb0a9dc 76f988da
-- 983e5152 a831c66d b00327c8 bf597fc7
-- c6e00bf3 d5a79147 06ca6351 14292967
-- 27b70a85 2e1b2138 4d2c6dfc 53380d13
-- 650a7354 766a0abb 81c2c92e 92722c85
-- a2bfe8a1 a81a664b c24b8b70 c76c51a3
-- d192e819 d6990624 f40e3585 106aa070
-- 19a4c116 1e376c08 2748774c 34b0bcb5
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 9]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- 391c0cb3 4ed8aa4a 5b9cca4f 682e6ff3
-- 748f82ee 78a5636f 84c87814 8cc70208
-- 90befffa a4506ceb bef9a3f7 c67178f2
--
--5.2. SHA-384 and SHA-512
--
-- SHA-384 and SHA-512 each use six logical functions, where each
-- function operates on 64-bit words, which are represented as x, y, and
-- z. The result of each function is a new 64-bit word.
--
-- CH( x, y, z) = (x AND y) XOR ( (NOT x) AND z)
--
-- MAJ( x, y, z) = (x AND y) XOR (x AND z) XOR (y AND z)
--
-- BSIG0(x) = ROTR^28(x) XOR ROTR^34(x) XOR ROTR^39(x)
--
-- BSIG1(x) = ROTR^14(x) XOR ROTR^18(x) XOR ROTR^41(x)
--
-- SSIG0(x) = ROTR^1(x) XOR ROTR^8(x) XOR SHR^7(x)
--
-- SSIG1(x) = ROTR^19(x) XOR ROTR^61(x) XOR SHR^6(x)
--
-- SHA-384 and SHA-512 use the same sequence of eighty constant 64-bit
-- words, K0, K1, ... K79. These words represent the first sixty-four
-- bits of the fractional parts of the cube roots of the first eighty
-- prime numbers. In hex, these constant words are as follows (from
-- left to right):
--
-- 428a2f98d728ae22 7137449123ef65cd b5c0fbcfec4d3b2f e9b5dba58189dbbc
-- 3956c25bf348b538 59f111f1b605d019 923f82a4af194f9b ab1c5ed5da6d8118
-- d807aa98a3030242 12835b0145706fbe 243185be4ee4b28c 550c7dc3d5ffb4e2
-- 72be5d74f27b896f 80deb1fe3b1696b1 9bdc06a725c71235 c19bf174cf692694
-- e49b69c19ef14ad2 efbe4786384f25e3 0fc19dc68b8cd5b5 240ca1cc77ac9c65
-- 2de92c6f592b0275 4a7484aa6ea6e483 5cb0a9dcbd41fbd4 76f988da831153b5
-- 983e5152ee66dfab a831c66d2db43210 b00327c898fb213f bf597fc7beef0ee4
-- c6e00bf33da88fc2 d5a79147930aa725 06ca6351e003826f 142929670a0e6e70
-- 27b70a8546d22ffc 2e1b21385c26c926 4d2c6dfc5ac42aed 53380d139d95b3df
-- 650a73548baf63de 766a0abb3c77b2a8 81c2c92e47edaee6 92722c851482353b
-- a2bfe8a14cf10364 a81a664bbc423001 c24b8b70d0f89791 c76c51a30654be30
-- d192e819d6ef5218 d69906245565a910 f40e35855771202a 106aa07032bbd1b8
-- 19a4c116b8d2d0c8 1e376c085141ab53 2748774cdf8eeb99 34b0bcb5e19b48a8
-- 391c0cb3c5c95a63 4ed8aa4ae3418acb 5b9cca4f7763e373 682e6ff3d6b2b8a3
-- 748f82ee5defb2fc 78a5636f43172f60 84c87814a1f0ab72 8cc702081a6439ec
-- 90befffa23631e28 a4506cebde82bde9 bef9a3f7b2c67915 c67178f2e372532b
-- ca273eceea26619c d186b8c721c0c207 eada7dd6cde0eb1e f57d4f7fee6ed178
-- 06f067aa72176fba 0a637dc5a2c898a6 113f9804bef90dae 1b710b35131c471b
-- 28db77f523047d84 32caab7b40c72493 3c9ebe0a15c9bebc 431d67c49c100d4c
-- 4cc5d4becb3e42b6 597f299cfc657e2a 5fcb6fab3ad6faec 6c44198c4a475817
--
--
--
--Eastlake 3rd & Hansen Informational [Page 10]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--6. Computing the Message Digest
--
-- The output of each of the secure hash functions, after being applied
-- to a message of N blocks, is the hash quantity H(N). For SHA-224 and
-- SHA-256, H(i) can be considered to be eight 32-bit words, H(i)0,
-- H(i)1, ... H(i)7. For SHA-384 and SHA-512, it can be considered to
-- be eight 64-bit words, H(i)0, H(i)1, ..., H(i)7.
--
-- As described below, the hash words are initialized, modified as each
-- message block is processed, and finally concatenated after processing
-- the last block to yield the output. For SHA-256 and SHA-512, all of
-- the H(N) variables are concatenated while the SHA-224 and SHA-384
-- hashes are produced by omitting some from the final concatenation.
--
--6.1. SHA-224 and SHA-256 Initialization
--
-- For SHA-224, the initial hash value, H(0), consists of the following
-- 32-bit words in hex:
--
-- H(0)0 = c1059ed8
-- H(0)1 = 367cd507
-- H(0)2 = 3070dd17
-- H(0)3 = f70e5939
-- H(0)4 = ffc00b31
-- H(0)5 = 68581511
-- H(0)6 = 64f98fa7
-- H(0)7 = befa4fa4
--
-- For SHA-256, the initial hash value, H(0), consists of the following
-- eight 32-bit words, in hex. These words were obtained by taking the
-- first thirty-two bits of the fractional parts of the square roots of
-- the first eight prime numbers.
--
-- H(0)0 = 6a09e667
-- H(0)1 = bb67ae85
-- H(0)2 = 3c6ef372
-- H(0)3 = a54ff53a
-- H(0)4 = 510e527f
-- H(0)5 = 9b05688c
-- H(0)6 = 1f83d9ab
-- H(0)7 = 5be0cd19
--
--6.2. SHA-224 and SHA-256 Processing
--
-- SHA-224 and SHA-256 perform identical processing on messages blocks
-- and differ only in how H(0) is initialized and how they produce their
-- final output. They may be used to hash a message, M, having a length
-- of L bits, where 0 <= L < 2^64. The algorithm uses (1) a message
--
--
--
--Eastlake 3rd & Hansen Informational [Page 11]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- schedule of sixty-four 32-bit words, (2) eight working variables of
-- 32 bits each, and (3) a hash value of eight 32-bit words.
--
-- The words of the message schedule are labeled W0, W1, ..., W63. The
-- eight working variables are labeled a, b, c, d, e, f, g, and h. The
-- words of the hash value are labeled H(i)0, H(i)1, ..., H(i)7, which
-- will hold the initial hash value, H(0), replaced by each successive
-- intermediate hash value (after each message block is processed),
-- H(i), and ending with the final hash value, H(N), after all N blocks
-- are processed. They also use two temporary words, T1 and T2.
--
-- The input message is padded as described in Section 4.1 above then
-- parsed into 512-bit blocks, which are considered to be composed of 16
-- 32-bit words M(i)0, M(i)1, ..., M(i)15. The following computations
-- are then performed for each of the N message blocks. All addition is
-- performed modulo 2^32.
--
-- For i = 1 to N
--
-- 1. Prepare the message schedule W:
-- For t = 0 to 15
-- Wt = M(i)t
-- For t = 16 to 63
-- Wt = SSIG1(W(t-2)) + W(t-7) + SSIG0(t-15) + W(t-16)
--
-- 2. Initialize the working variables:
-- a = H(i-1)0
-- b = H(i-1)1
-- c = H(i-1)2
-- d = H(i-1)3
-- e = H(i-1)4
-- f = H(i-1)5
-- g = H(i-1)6
-- h = H(i-1)7
--
-- 3. Perform the main hash computation:
-- For t = 0 to 63
-- T1 = h + BSIG1(e) + CH(e,f,g) + Kt + Wt
-- T2 = BSIG0(a) + MAJ(a,b,c)
-- h = g
-- g = f
-- f = e
-- e = d + T1
-- d = c
-- c = b
-- b = a
-- a = T1 + T2
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 12]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- 4. Compute the intermediate hash value H(i):
-- H(i)0 = a + H(i-1)0
-- H(i)1 = b + H(i-1)1
-- H(i)2 = c + H(i-1)2
-- H(i)3 = d + H(i-1)3
-- H(i)4 = e + H(i-1)4
-- H(i)5 = f + H(i-1)5
-- H(i)6 = g + H(i-1)6
-- H(i)7 = h + H(i-1)7
--
-- After the above computations have been sequentially performed for all
-- of the blocks in the message, the final output is calculated. For
-- SHA-256, this is the concatenation of all of H(N)0, H(N)1, through
-- H(N)7. For SHA-224, this is the concatenation of H(N)0, H(N)1,
-- through H(N)6.
--
--6.3. SHA-384 and SHA-512 Initialization
--
-- For SHA-384, the initial hash value, H(0), consists of the following
-- eight 64-bit words, in hex. These words were obtained by taking the
-- first sixty-four bits of the fractional parts of the square roots of
-- the ninth through sixteenth prime numbers.
--
-- H(0)0 = cbbb9d5dc1059ed8
-- H(0)1 = 629a292a367cd507
-- H(0)2 = 9159015a3070dd17
-- H(0)3 = 152fecd8f70e5939
-- H(0)4 = 67332667ffc00b31
-- H(0)5 = 8eb44a8768581511
-- H(0)6 = db0c2e0d64f98fa7
-- H(0)7 = 47b5481dbefa4fa4
--
-- For SHA-512, the initial hash value, H(0), consists of the following
-- eight 64-bit words, in hex. These words were obtained by taking the
-- first sixty-four bits of the fractional parts of the square roots of
-- the first eight prime numbers.
--
-- H(0)0 = 6a09e667f3bcc908
-- H(0)1 = bb67ae8584caa73b
-- H(0)2 = 3c6ef372fe94f82b
-- H(0)3 = a54ff53a5f1d36f1
-- H(0)4 = 510e527fade682d1
-- H(0)5 = 9b05688c2b3e6c1f
-- H(0)6 = 1f83d9abfb41bd6b
-- H(0)7 = 5be0cd19137e2179
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 13]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--6.4. SHA-384 and SHA-512 Processing
--
-- SHA-384 and SHA-512 perform identical processing on message blocks
-- and differ only in how H(0) is initialized and how they produce their
-- final output. They may be used to hash a message, M, having a length
-- of L bits, where 0 <= L < 2^128. The algorithm uses (1) a message
-- schedule of eighty 64-bit words, (2) eight working variables of 64
-- bits each, and (3) a hash value of eight 64-bit words.
--
-- The words of the message schedule are labeled W0, W1, ..., W79. The
-- eight working variables are labeled a, b, c, d, e, f, g, and h. The
-- words of the hash value are labeled H(i)0, H(i)1, ..., H(i)7, which
-- will hold the initial hash value, H(0), replaced by each successive
-- intermediate hash value (after each message block is processed),
-- H(i), and ending with the final hash value, H(N) after all N blocks
-- are processed.
--
-- The input message is padded as described in Section 4.2 above, then
-- parsed into 1024-bit blocks, which are considered to be composed of
-- 16 64-bit words M(i)0, M(i)1, ..., M(i)15. The following
-- computations are then performed for each of the N message blocks.
-- All addition is performed modulo 2^64.
--
-- For i = 1 to N
--
-- 1. Prepare the message schedule W:
-- For t = 0 to 15
-- Wt = M(i)t
-- For t = 16 to 79
-- Wt = SSIG1(W(t-2)) + W(t-7) + SSIG0(t-15) + W(t-16)
--
-- 2. Initialize the working variables:
-- a = H(i-1)0
-- b = H(i-1)1
-- c = H(i-1)2
-- d = H(i-1)3
-- e = H(i-1)4
-- f = H(i-1)5
-- g = H(i-1)6
-- h = H(i-1)7
--
-- 3. Perform the main hash computation:
-- For t = 0 to 79
-- T1 = h + BSIG1(e) + CH(e,f,g) + Kt + Wt
-- T2 = BSIG0(a) + MAJ(a,b,c)
-- h = g
-- g = f
-- f = e
--
--
--
--Eastlake 3rd & Hansen Informational [Page 14]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- e = d + T1
-- d = c
-- c = b
-- b = a
-- a = T1 + T2
--
-- 4. Compute the intermediate hash value H(i):
-- H(i)0 = a + H(i-1)0
-- H(i)1 = b + H(i-1)1
-- H(i)2 = c + H(i-1)2
-- H(i)3 = d + H(i-1)3
-- H(i)4 = e + H(i-1)4
-- H(i)5 = f + H(i-1)5
-- H(i)6 = g + H(i-1)6
-- H(i)7 = h + H(i-1)7
--
-- After the above computations have been sequentially performed for all
-- of the blocks in the message, the final output is calculated. For
-- SHA-512, this is the concatenation of all of H(N)0, H(N)1, through
-- H(N)7. For SHA-384, this is the concatenation of H(N)0, H(N)1,
-- through H(N)5.
--
--7. SHA-Based HMACs
--
-- HMAC is a method for computing a keyed MAC (message authentication
-- code) using a hash function as described in [RFC2104]. It uses a key
-- to mix in with the input text to produce the final hash.
--
-- Sample code is also provided, in Section 8.3 below, to perform HMAC
-- based on any of the SHA algorithms described herein. The sample code
-- found in [RFC2104] was written in terms of a specified text size.
-- Since SHA is defined in terms of an arbitrary number of bits, the
-- sample HMAC code has been written to allow the text input to HMAC to
-- have an arbitrary number of octets and bits. A fixed-length
-- interface is also provided.
--
--8. C Code for SHAs
--
-- Below is a demonstration implementation of these secure hash
-- functions in C. Section 8.1 contains the header file sha.h, which
-- declares all constants, structures, and functions used by the sha and
-- hmac functions. Section 8.2 contains the C code for sha1.c,
-- sha224-256.c, sha384-512.c, and usha.c along with sha-private.h,
-- which provides some declarations common to all the sha functions.
-- Section 8.3 contains the C code for the hmac functions. Section 8.4
-- contains a test driver to exercise the code.
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 15]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- For each of the digest length $$$, there is the following set of
-- constants, a structure, and functions:
--
-- Constants:
-- SHA$$$HashSize number of octets in the hash
-- SHA$$$HashSizeBits number of bits in the hash
-- SHA$$$_Message_Block_Size
-- number of octets used in the intermediate
-- message blocks
-- shaSuccess = 0 constant returned by each function on success
-- shaNull = 1 constant returned by each function when
-- presented with a null pointer parameter
-- shaInputTooLong = 2 constant returned by each function when the
-- input data is too long
-- shaStateError constant returned by each function when
-- SHA$$$Input is called after SHA$$$FinalBits or
-- SHA$$$Result.
--
-- Structure:
-- typedef SHA$$$Context
-- an opaque structure holding the complete state
-- for producing the hash
--
-- Functions:
-- int SHA$$$Reset(SHA$$$Context *);
-- Reset the hash context state
-- int SHA$$$Input(SHA$$$Context *, const uint8_t *octets,
-- unsigned int bytecount);
-- Incorporate bytecount octets into the hash.
-- int SHA$$$FinalBits(SHA$$$Context *, const uint8_t octet,
-- unsigned int bitcount);
-- Incorporate bitcount bits into the hash. The bits are in
-- the upper portion of the octet. SHA$$$Input() cannot be
-- called after this.
-- int SHA$$$Result(SHA$$$Context *,
-- uint8_t Message_Digest[SHA$$$HashSize]);
-- Do the final calculations on the hash and copy the value
-- into Message_Digest.
--
-- In addition, functions with the prefix USHA are provided that take a
-- SHAversion value (SHA$$$) to select the SHA function suite. They add
-- the following constants, structure, and functions:
--
-- Constants:
-- shaBadParam constant returned by USHA functions when
-- presented with a bad SHAversion (SHA$$$)
-- parameter
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 16]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- SHA$$$ SHAversion enumeration values, used by usha
-- and hmac functions to select the SHA function
-- suite
--
-- Structure:
-- typedef USHAContext
-- an opaque structure holding the complete state
-- for producing the hash
--
-- Functions:
-- int USHAReset(USHAContext *, SHAversion whichSha);
-- Reset the hash context state.
-- int USHAInput(USHAContext *,
-- const uint8_t *bytes, unsigned int bytecount);
-- Incorporate bytecount octets into the hash.
-- int USHAFinalBits(USHAContext *,
-- const uint8_t bits, unsigned int bitcount);
-- Incorporate bitcount bits into the hash.
-- int USHAResult(USHAContext *,
-- uint8_t Message_Digest[USHAMaxHashSize]);
-- Do the final calculations on the hash and copy the value
-- into Message_Digest. Octets in Message_Digest beyond
-- USHAHashSize(whichSha) are left untouched.
-- int USHAHashSize(enum SHAversion whichSha);
-- The number of octets in the given hash.
-- int USHAHashSizeBits(enum SHAversion whichSha);
-- The number of bits in the given hash.
-- int USHABlockSize(enum SHAversion whichSha);
-- The internal block size for the given hash.
--
-- The hmac functions follow the same pattern to allow any length of
-- text input to be used.
--
-- Structure:
-- typedef HMACContext an opaque structure holding the complete state
-- for producing the hash
--
-- Functions:
-- int hmacReset(HMACContext *ctx, enum SHAversion whichSha,
-- const unsigned char *key, int key_len);
-- Reset the hash context state.
-- int hmacInput(HMACContext *ctx, const unsigned char *text,
-- int text_len);
-- Incorporate text_len octets into the hash.
-- int hmacFinalBits(HMACContext *ctx, const uint8_t bits,
-- unsigned int bitcount);
-- Incorporate bitcount bits into the hash.
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 17]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- int hmacResult(HMACContext *ctx,
-- uint8_t Message_Digest[USHAMaxHashSize]);
-- Do the final calculations on the hash and copy the value
-- into Message_Digest. Octets in Message_Digest beyond
-- USHAHashSize(whichSha) are left untouched.
--
-- In addition, a combined interface is provided, similar to that shown
-- in RFC 2104, that allows a fixed-length text input to be used.
--
-- int hmac(SHAversion whichSha,
-- const unsigned char *text, int text_len,
-- const unsigned char *key, int key_len,
-- uint8_t Message_Digest[USHAMaxHashSize]);
-- Calculate the given digest for the given text and key, and
-- return the resulting hash. Octets in Message_Digest beyond
-- USHAHashSize(whichSha) are left untouched.
--
--8.1. The .h File
--
--/**************************** sha.h ****************************/
--/******************* See RFC 4634 for details ******************/
--#ifndef _SHA_H_
--#define _SHA_H_
--
--/*
-- * Description:
-- * This file implements the Secure Hash Signature Standard
-- * algorithms as defined in the National Institute of Standards
-- * and Technology Federal Information Processing Standards
-- * Publication (FIPS PUB) 180-1 published on April 17, 1995, 180-2
-- * published on August 1, 2002, and the FIPS PUB 180-2 Change
-- * Notice published on February 28, 2004.
-- *
-- * A combined document showing all algorithms is available at
-- * http://csrc.nist.gov/publications/fips/
-- * fips180-2/fips180-2withchangenotice.pdf
-- *
-- * The five hashes are defined in these sizes:
-- * SHA-1 20 byte / 160 bit
-- * SHA-224 28 byte / 224 bit
-- * SHA-256 32 byte / 256 bit
-- * SHA-384 48 byte / 384 bit
-- * SHA-512 64 byte / 512 bit
-- */
--
--#include <stdint.h>
--/*
-- * If you do not have the ISO standard stdint.h header file, then you
--
--
--
--Eastlake 3rd & Hansen Informational [Page 18]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * must typedef the following:
-- * name meaning
-- * uint64_t unsigned 64 bit integer
-- * uint32_t unsigned 32 bit integer
-- * uint8_t unsigned 8 bit integer (i.e., unsigned char)
-- * int_least16_t integer of >= 16 bits
-- *
-- */
--
--#ifndef _SHA_enum_
--#define _SHA_enum_
--/*
-- * All SHA functions return one of these values.
-- */
--enum {
-- shaSuccess = 0,
-- shaNull, /* Null pointer parameter */
-- shaInputTooLong, /* input data too long */
-- shaStateError, /* called Input after FinalBits or Result */
-- shaBadParam /* passed a bad parameter */
--};
--#endif /* _SHA_enum_ */
--
--/*
-- * These constants hold size information for each of the SHA
-- * hashing operations
-- */
--enum {
-- SHA1_Message_Block_Size = 64, SHA224_Message_Block_Size = 64,
-- SHA256_Message_Block_Size = 64, SHA384_Message_Block_Size = 128,
-- SHA512_Message_Block_Size = 128,
-- USHA_Max_Message_Block_Size = SHA512_Message_Block_Size,
--
-- SHA1HashSize = 20, SHA224HashSize = 28, SHA256HashSize = 32,
-- SHA384HashSize = 48, SHA512HashSize = 64,
-- USHAMaxHashSize = SHA512HashSize,
--
-- SHA1HashSizeBits = 160, SHA224HashSizeBits = 224,
-- SHA256HashSizeBits = 256, SHA384HashSizeBits = 384,
-- SHA512HashSizeBits = 512, USHAMaxHashSizeBits = SHA512HashSizeBits
--};
--
--/*
-- * These constants are used in the USHA (unified sha) functions.
-- */
--typedef enum SHAversion {
-- SHA1, SHA224, SHA256, SHA384, SHA512
--} SHAversion;
--
--
--
--Eastlake 3rd & Hansen Informational [Page 19]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * This structure will hold context information for the SHA-1
-- * hashing operation.
-- */
--typedef struct SHA1Context {
-- uint32_t Intermediate_Hash[SHA1HashSize/4]; /* Message Digest */
--
-- uint32_t Length_Low; /* Message length in bits */
-- uint32_t Length_High; /* Message length in bits */
--
-- int_least16_t Message_Block_Index; /* Message_Block array index */
-- /* 512-bit message blocks */
-- uint8_t Message_Block[SHA1_Message_Block_Size];
--
-- int Computed; /* Is the digest computed? */
-- int Corrupted; /* Is the digest corrupted? */
--} SHA1Context;
--
--/*
-- * This structure will hold context information for the SHA-256
-- * hashing operation.
-- */
--typedef struct SHA256Context {
-- uint32_t Intermediate_Hash[SHA256HashSize/4]; /* Message Digest */
--
-- uint32_t Length_Low; /* Message length in bits */
-- uint32_t Length_High; /* Message length in bits */
--
-- int_least16_t Message_Block_Index; /* Message_Block array index */
-- /* 512-bit message blocks */
-- uint8_t Message_Block[SHA256_Message_Block_Size];
--
-- int Computed; /* Is the digest computed? */
-- int Corrupted; /* Is the digest corrupted? */
--} SHA256Context;
--
--/*
-- * This structure will hold context information for the SHA-512
-- * hashing operation.
-- */
--typedef struct SHA512Context {
--#ifdef USE_32BIT_ONLY
-- uint32_t Intermediate_Hash[SHA512HashSize/4]; /* Message Digest */
-- uint32_t Length[4]; /* Message length in bits */
--#else /* !USE_32BIT_ONLY */
-- uint64_t Intermediate_Hash[SHA512HashSize/8]; /* Message Digest */
-- uint64_t Length_Low, Length_High; /* Message length in bits */
--#endif /* USE_32BIT_ONLY */
--
--
--
--Eastlake 3rd & Hansen Informational [Page 20]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- int_least16_t Message_Block_Index; /* Message_Block array index */
-- /* 1024-bit message blocks */
-- uint8_t Message_Block[SHA512_Message_Block_Size];
--
-- int Computed; /* Is the digest computed?*/
-- int Corrupted; /* Is the digest corrupted? */
--} SHA512Context;
--
--/*
-- * This structure will hold context information for the SHA-224
-- * hashing operation. It uses the SHA-256 structure for computation.
-- */
--typedef struct SHA256Context SHA224Context;
--
--/*
-- * This structure will hold context information for the SHA-384
-- * hashing operation. It uses the SHA-512 structure for computation.
-- */
--typedef struct SHA512Context SHA384Context;
--
--/*
-- * This structure holds context information for all SHA
-- * hashing operations.
-- */
--typedef struct USHAContext {
-- int whichSha; /* which SHA is being used */
-- union {
-- SHA1Context sha1Context;
-- SHA224Context sha224Context; SHA256Context sha256Context;
-- SHA384Context sha384Context; SHA512Context sha512Context;
-- } ctx;
--} USHAContext;
--
--/*
-- * This structure will hold context information for the HMAC
-- * keyed hashing operation.
-- */
--typedef struct HMACContext {
-- int whichSha; /* which SHA is being used */
-- int hashSize; /* hash size of SHA being used */
-- int blockSize; /* block size of SHA being used */
-- USHAContext shaContext; /* SHA context */
-- unsigned char k_opad[USHA_Max_Message_Block_Size];
-- /* outer padding - key XORd with opad */
--} HMACContext;
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 21]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * Function Prototypes
-- */
--
--/* SHA-1 */
--extern int SHA1Reset(SHA1Context *);
--extern int SHA1Input(SHA1Context *, const uint8_t *bytes,
-- unsigned int bytecount);
--extern int SHA1FinalBits(SHA1Context *, const uint8_t bits,
-- unsigned int bitcount);
--extern int SHA1Result(SHA1Context *,
-- uint8_t Message_Digest[SHA1HashSize]);
--
--/* SHA-224 */
--extern int SHA224Reset(SHA224Context *);
--extern int SHA224Input(SHA224Context *, const uint8_t *bytes,
-- unsigned int bytecount);
--extern int SHA224FinalBits(SHA224Context *, const uint8_t bits,
-- unsigned int bitcount);
--extern int SHA224Result(SHA224Context *,
-- uint8_t Message_Digest[SHA224HashSize]);
--
--/* SHA-256 */
--extern int SHA256Reset(SHA256Context *);
--extern int SHA256Input(SHA256Context *, const uint8_t *bytes,
-- unsigned int bytecount);
--extern int SHA256FinalBits(SHA256Context *, const uint8_t bits,
-- unsigned int bitcount);
--extern int SHA256Result(SHA256Context *,
-- uint8_t Message_Digest[SHA256HashSize]);
--
--/* SHA-384 */
--extern int SHA384Reset(SHA384Context *);
--extern int SHA384Input(SHA384Context *, const uint8_t *bytes,
-- unsigned int bytecount);
--extern int SHA384FinalBits(SHA384Context *, const uint8_t bits,
-- unsigned int bitcount);
--extern int SHA384Result(SHA384Context *,
-- uint8_t Message_Digest[SHA384HashSize]);
--
--/* SHA-512 */
--extern int SHA512Reset(SHA512Context *);
--extern int SHA512Input(SHA512Context *, const uint8_t *bytes,
-- unsigned int bytecount);
--extern int SHA512FinalBits(SHA512Context *, const uint8_t bits,
-- unsigned int bitcount);
--extern int SHA512Result(SHA512Context *,
-- uint8_t Message_Digest[SHA512HashSize]);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 22]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/* Unified SHA functions, chosen by whichSha */
--extern int USHAReset(USHAContext *, SHAversion whichSha);
--extern int USHAInput(USHAContext *,
-- const uint8_t *bytes, unsigned int bytecount);
--extern int USHAFinalBits(USHAContext *,
-- const uint8_t bits, unsigned int bitcount);
--extern int USHAResult(USHAContext *,
-- uint8_t Message_Digest[USHAMaxHashSize]);
--extern int USHABlockSize(enum SHAversion whichSha);
--extern int USHAHashSize(enum SHAversion whichSha);
--extern int USHAHashSizeBits(enum SHAversion whichSha);
--
--/*
-- * HMAC Keyed-Hashing for Message Authentication, RFC2104,
-- * for all SHAs.
-- * This interface allows a fixed-length text input to be used.
-- */
--extern int hmac(SHAversion whichSha, /* which SHA algorithm to use */
-- const unsigned char *text, /* pointer to data stream */
-- int text_len, /* length of data stream */
-- const unsigned char *key, /* pointer to authentication key */
-- int key_len, /* length of authentication key */
-- uint8_t digest[USHAMaxHashSize]); /* caller digest to fill in */
--
--/*
-- * HMAC Keyed-Hashing for Message Authentication, RFC2104,
-- * for all SHAs.
-- * This interface allows any length of text input to be used.
-- */
--extern int hmacReset(HMACContext *ctx, enum SHAversion whichSha,
-- const unsigned char *key, int key_len);
--extern int hmacInput(HMACContext *ctx, const unsigned char *text,
-- int text_len);
--
--extern int hmacFinalBits(HMACContext *ctx, const uint8_t bits,
-- unsigned int bitcount);
--extern int hmacResult(HMACContext *ctx,
-- uint8_t digest[USHAMaxHashSize]);
--
--#endif /* _SHA_H_ */
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 23]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--8.2. The SHA Code
--
-- This code is primarily intended as expository and could be optimized
-- further. For example, the assignment rotations through the variables
-- a, b, ..., h could be treated as a cycle and the loop unrolled,
-- rather than doing the explicit copying.
--
-- Note that there are alternative representations of the Ch() and Maj()
-- functions controlled by an ifdef.
--
--8.2.1. sha1.c
--
--/**************************** sha1.c ****************************/
--/******************** See RFC 4634 for details ******************/
--/*
-- * Description:
-- * This file implements the Secure Hash Signature Standard
-- * algorithms as defined in the National Institute of Standards
-- * and Technology Federal Information Processing Standards
-- * Publication (FIPS PUB) 180-1 published on April 17, 1995, 180-2
-- * published on August 1, 2002, and the FIPS PUB 180-2 Change
-- * Notice published on February 28, 2004.
-- *
-- * A combined document showing all algorithms is available at
-- * http://csrc.nist.gov/publications/fips/
-- * fips180-2/fips180-2withchangenotice.pdf
-- *
-- * The SHA-1 algorithm produces a 160-bit message digest for a
-- * given data stream. It should take about 2**n steps to find a
-- * message with the same digest as a given message and
-- * 2**(n/2) to find any two messages with the same digest,
-- * when n is the digest size in bits. Therefore, this
-- * algorithm can serve as a means of providing a
-- * "fingerprint" for a message.
-- *
-- * Portability Issues:
-- * SHA-1 is defined in terms of 32-bit "words". This code
-- * uses <stdint.h> (included via "sha.h") to define 32 and 8
-- * bit unsigned integer types. If your C compiler does not
-- * support 32 bit unsigned integers, this code is not
-- * appropriate.
-- *
-- * Caveats:
-- * SHA-1 is designed to work with messages less than 2^64 bits
-- * long. This implementation uses SHA1Input() to hash the bits
-- * that are a multiple of the size of an 8-bit character, and then
-- * uses SHA1FinalBits() to hash the final few bits of the input.
-- */
--
--
--
--Eastlake 3rd & Hansen Informational [Page 24]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--#include "sha.h"
--#include "sha-private.h"
--
--/*
-- * Define the SHA1 circular left shift macro
-- */
--#define SHA1_ROTL(bits,word) \
-- (((word) << (bits)) | ((word) >> (32-(bits))))
--
--/*
-- * add "length" to the length
-- */
--static uint32_t addTemp;
--#define SHA1AddLength(context, length) \
-- (addTemp = (context)->Length_Low, \
-- (context)->Corrupted = \
-- (((context)->Length_Low += (length)) < addTemp) && \
-- (++(context)->Length_High == 0) ? 1 : 0)
--
--/* Local Function Prototypes */
--static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte);
--static void SHA1PadMessage(SHA1Context *, uint8_t Pad_Byte);
--static void SHA1ProcessMessageBlock(SHA1Context *);
--
--/*
-- * SHA1Reset
-- *
-- * Description:
-- * This function will initialize the SHA1Context in preparation
-- * for computing a new SHA1 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA1Reset(SHA1Context *context)
--{
-- if (!context)
-- return shaNull;
--
-- context->Length_Low = 0;
-- context->Length_High = 0;
-- context->Message_Block_Index = 0;
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 25]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- /* Initial Hash Values: FIPS-180-2 section 5.3.1 */
-- context->Intermediate_Hash[0] = 0x67452301;
-- context->Intermediate_Hash[1] = 0xEFCDAB89;
-- context->Intermediate_Hash[2] = 0x98BADCFE;
-- context->Intermediate_Hash[3] = 0x10325476;
-- context->Intermediate_Hash[4] = 0xC3D2E1F0;
--
-- context->Computed = 0;
-- context->Corrupted = 0;
--
-- return shaSuccess;
--}
--
--/*
-- * SHA1Input
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA1Input(SHA1Context *context,
-- const uint8_t *message_array, unsigned length)
--{
-- if (!length)
-- return shaSuccess;
--
-- if (!context || !message_array)
-- return shaNull;
--
-- if (context->Computed) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
-- }
--
-- if (context->Corrupted)
--
--
--
--Eastlake 3rd & Hansen Informational [Page 26]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- return context->Corrupted;
--
-- while (length-- && !context->Corrupted) {
-- context->Message_Block[context->Message_Block_Index++] =
-- (*message_array & 0xFF);
--
-- if (!SHA1AddLength(context, 8) &&
-- (context->Message_Block_Index == SHA1_Message_Block_Size))
-- SHA1ProcessMessageBlock(context);
--
-- message_array++;
-- }
--
-- return shaSuccess;
--}
--
--/*
-- * SHA1FinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA1FinalBits(SHA1Context *context, const uint8_t message_bits,
-- unsigned int length)
--{
-- uint8_t masks[8] = {
-- /* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
-- /* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
-- /* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
-- /* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
-- };
-- uint8_t markbit[8] = {
-- /* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
-- /* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
-- /* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 27]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- /* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
-- };
--
-- if (!length)
-- return shaSuccess;
--
-- if (!context)
-- return shaNull;
--
-- if (context->Computed || (length >= 8) || (length == 0)) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
-- }
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- SHA1AddLength(context, length);
-- SHA1Finalize(context,
-- (uint8_t) ((message_bits & masks[length]) | markbit[length]));
--
-- return shaSuccess;
--}
--
--/*
-- * SHA1Result
-- *
-- * Description:
-- * This function will return the 160-bit message digest into the
-- * Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 19th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA-1 hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA1Result(SHA1Context *context,
-- uint8_t Message_Digest[SHA1HashSize])
--{
-- int i;
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 28]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- if (!context || !Message_Digest)
-- return shaNull;
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- if (!context->Computed)
-- SHA1Finalize(context, 0x80);
--
-- for (i = 0; i < SHA1HashSize; ++i)
-- Message_Digest[i] = (uint8_t) (context->Intermediate_Hash[i>>2]
-- >> 8 * ( 3 - ( i & 0x03 ) ));
--
-- return shaSuccess;
--}
--
--/*
-- * SHA1Finalize
-- *
-- * Description:
-- * This helper function finishes off the digest calculations.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte)
--{
-- int i;
-- SHA1PadMessage(context, Pad_Byte);
-- /* message may be sensitive, clear it out */
-- for (i = 0; i < SHA1_Message_Block_Size; ++i)
-- context->Message_Block[i] = 0;
-- context->Length_Low = 0; /* and clear length */
-- context->Length_High = 0;
-- context->Computed = 1;
--}
--
--/*
--
--
--
--Eastlake 3rd & Hansen Informational [Page 29]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * SHA1PadMessage
-- *
-- * Description:
-- * According to the standard, the message must be padded to an
-- * even 512 bits. The first padding bit must be a '1'. The last
-- * 64 bits represent the length of the original message. All bits
-- * in between should be 0. This helper function will pad the
-- * message according to those rules by filling the Message_Block
-- * array accordingly. When it returns, it can be assumed that the
-- * message digest has been computed.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to pad
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * Nothing.
-- */
--static void SHA1PadMessage(SHA1Context *context, uint8_t Pad_Byte)
--{
-- /*
-- * Check to see if the current message block is too small to hold
-- * the initial padding bits and length. If so, we will pad the
-- * block, process it, and then continue padding into a second
-- * block.
-- */
-- if (context->Message_Block_Index >= (SHA1_Message_Block_Size - 8)) {
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
-- while (context->Message_Block_Index < SHA1_Message_Block_Size)
-- context->Message_Block[context->Message_Block_Index++] = 0;
--
-- SHA1ProcessMessageBlock(context);
-- } else
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
--
-- while (context->Message_Block_Index < (SHA1_Message_Block_Size - 8))
-- context->Message_Block[context->Message_Block_Index++] = 0;
--
-- /*
-- * Store the message length as the last 8 octets
-- */
-- context->Message_Block[56] = (uint8_t) (context->Length_High >> 24);
-- context->Message_Block[57] = (uint8_t) (context->Length_High >> 16);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 30]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- context->Message_Block[58] = (uint8_t) (context->Length_High >> 8);
-- context->Message_Block[59] = (uint8_t) (context->Length_High);
-- context->Message_Block[60] = (uint8_t) (context->Length_Low >> 24);
-- context->Message_Block[61] = (uint8_t) (context->Length_Low >> 16);
-- context->Message_Block[62] = (uint8_t) (context->Length_Low >> 8);
-- context->Message_Block[63] = (uint8_t) (context->Length_Low);
--
-- SHA1ProcessMessageBlock(context);
--}
--
--/*
-- * SHA1ProcessMessageBlock
-- *
-- * Description:
-- * This helper function will process the next 512 bits of the
-- * message stored in the Message_Block array.
-- *
-- * Parameters:
-- * None.
-- *
-- * Returns:
-- * Nothing.
-- *
-- * Comments:
-- * Many of the variable names in this code, especially the
-- * single character names, were used because those were the
-- * names used in the publication.
-- */
--static void SHA1ProcessMessageBlock(SHA1Context *context)
--{
-- /* Constants defined in FIPS-180-2, section 4.2.1 */
-- const uint32_t K[4] = {
-- 0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6
-- };
-- int t; /* Loop counter */
-- uint32_t temp; /* Temporary word value */
-- uint32_t W[80]; /* Word sequence */
-- uint32_t A, B, C, D, E; /* Word buffers */
--
-- /*
-- * Initialize the first 16 words in the array W
-- */
-- for (t = 0; t < 16; t++) {
-- W[t] = ((uint32_t)context->Message_Block[t * 4]) << 24;
-- W[t] |= ((uint32_t)context->Message_Block[t * 4 + 1]) << 16;
-- W[t] |= ((uint32_t)context->Message_Block[t * 4 + 2]) << 8;
-- W[t] |= ((uint32_t)context->Message_Block[t * 4 + 3]);
-- }
--
--
--
--Eastlake 3rd & Hansen Informational [Page 31]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- for (t = 16; t < 80; t++)
-- W[t] = SHA1_ROTL(1, W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
--
-- A = context->Intermediate_Hash[0];
-- B = context->Intermediate_Hash[1];
-- C = context->Intermediate_Hash[2];
-- D = context->Intermediate_Hash[3];
-- E = context->Intermediate_Hash[4];
--
-- for (t = 0; t < 20; t++) {
-- temp = SHA1_ROTL(5,A) + SHA_Ch(B, C, D) + E + W[t] + K[0];
-- E = D;
-- D = C;
-- C = SHA1_ROTL(30,B);
-- B = A;
-- A = temp;
-- }
--
-- for (t = 20; t < 40; t++) {
-- temp = SHA1_ROTL(5,A) + SHA_Parity(B, C, D) + E + W[t] + K[1];
-- E = D;
-- D = C;
-- C = SHA1_ROTL(30,B);
-- B = A;
-- A = temp;
-- }
--
-- for (t = 40; t < 60; t++) {
-- temp = SHA1_ROTL(5,A) + SHA_Maj(B, C, D) + E + W[t] + K[2];
-- E = D;
-- D = C;
-- C = SHA1_ROTL(30,B);
-- B = A;
-- A = temp;
-- }
--
-- for (t = 60; t < 80; t++) {
-- temp = SHA1_ROTL(5,A) + SHA_Parity(B, C, D) + E + W[t] + K[3];
-- E = D;
-- D = C;
-- C = SHA1_ROTL(30,B);
-- B = A;
-- A = temp;
-- }
--
-- context->Intermediate_Hash[0] += A;
-- context->Intermediate_Hash[1] += B;
-- context->Intermediate_Hash[2] += C;
--
--
--
--Eastlake 3rd & Hansen Informational [Page 32]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- context->Intermediate_Hash[3] += D;
-- context->Intermediate_Hash[4] += E;
--
-- context->Message_Block_Index = 0;
--}
--
--8.2.2. sha224-256.c
--
--/*************************** sha224-256.c ***************************/
--/********************* See RFC 4634 for details *********************/
--/*
-- * Description:
-- * This file implements the Secure Hash Signature Standard
-- * algorithms as defined in the National Institute of Standards
-- * and Technology Federal Information Processing Standards
-- * Publication (FIPS PUB) 180-1 published on April 17, 1995, 180-2
-- * published on August 1, 2002, and the FIPS PUB 180-2 Change
-- * Notice published on February 28, 2004.
-- *
-- * A combined document showing all algorithms is available at
-- * http://csrc.nist.gov/publications/fips/
-- * fips180-2/fips180-2withchangenotice.pdf
-- *
-- * The SHA-224 and SHA-256 algorithms produce 224-bit and 256-bit
-- * message digests for a given data stream. It should take about
-- * 2**n steps to find a message with the same digest as a given
-- * message and 2**(n/2) to find any two messages with the same
-- * digest, when n is the digest size in bits. Therefore, this
-- * algorithm can serve as a means of providing a
-- * "fingerprint" for a message.
-- *
-- * Portability Issues:
-- * SHA-224 and SHA-256 are defined in terms of 32-bit "words".
-- * This code uses <stdint.h> (included via "sha.h") to define 32
-- * and 8 bit unsigned integer types. If your C compiler does not
-- * support 32 bit unsigned integers, this code is not
-- * appropriate.
-- *
-- * Caveats:
-- * SHA-224 and SHA-256 are designed to work with messages less
-- * than 2^64 bits long. This implementation uses SHA224/256Input()
-- * to hash the bits that are a multiple of the size of an 8-bit
-- * character, and then uses SHA224/256FinalBits() to hash the
-- * final few bits of the input.
-- */
--
--#include "sha.h"
--#include "sha-private.h"
--
--
--
--Eastlake 3rd & Hansen Informational [Page 33]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/* Define the SHA shift, rotate left and rotate right macro */
--#define SHA256_SHR(bits,word) ((word) >> (bits))
--#define SHA256_ROTL(bits,word) \
-- (((word) << (bits)) | ((word) >> (32-(bits))))
--#define SHA256_ROTR(bits,word) \
-- (((word) >> (bits)) | ((word) << (32-(bits))))
--
--/* Define the SHA SIGMA and sigma macros */
--#define SHA256_SIGMA0(word) \
-- (SHA256_ROTR( 2,word) ^ SHA256_ROTR(13,word) ^ SHA256_ROTR(22,word))
--#define SHA256_SIGMA1(word) \
-- (SHA256_ROTR( 6,word) ^ SHA256_ROTR(11,word) ^ SHA256_ROTR(25,word))
--#define SHA256_sigma0(word) \
-- (SHA256_ROTR( 7,word) ^ SHA256_ROTR(18,word) ^ SHA256_SHR( 3,word))
--#define SHA256_sigma1(word) \
-- (SHA256_ROTR(17,word) ^ SHA256_ROTR(19,word) ^ SHA256_SHR(10,word))
--
--/*
-- * add "length" to the length
-- */
--static uint32_t addTemp;
--#define SHA224_256AddLength(context, length) \
-- (addTemp = (context)->Length_Low, (context)->Corrupted = \
-- (((context)->Length_Low += (length)) < addTemp) && \
-- (++(context)->Length_High == 0) ? 1 : 0)
--
--/* Local Function Prototypes */
--static void SHA224_256Finalize(SHA256Context *context,
-- uint8_t Pad_Byte);
--static void SHA224_256PadMessage(SHA256Context *context,
-- uint8_t Pad_Byte);
--static void SHA224_256ProcessMessageBlock(SHA256Context *context);
--static int SHA224_256Reset(SHA256Context *context, uint32_t *H0);
--static int SHA224_256ResultN(SHA256Context *context,
-- uint8_t Message_Digest[], int HashSize);
--
--/* Initial Hash Values: FIPS-180-2 Change Notice 1 */
--static uint32_t SHA224_H0[SHA256HashSize/4] = {
-- 0xC1059ED8, 0x367CD507, 0x3070DD17, 0xF70E5939,
-- 0xFFC00B31, 0x68581511, 0x64F98FA7, 0xBEFA4FA4
--};
--
--/* Initial Hash Values: FIPS-180-2 section 5.3.2 */
--static uint32_t SHA256_H0[SHA256HashSize/4] = {
-- 0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
-- 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19
--};
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 34]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * SHA224Reset
-- *
-- * Description:
-- * This function will initialize the SHA384Context in preparation
-- * for computing a new SHA224 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA224Reset(SHA224Context *context)
--{
-- return SHA224_256Reset(context, SHA224_H0);
--}
--
--/*
-- * SHA224Input
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA224Input(SHA224Context *context, const uint8_t *message_array,
-- unsigned int length)
--{
-- return SHA256Input(context, message_array, length);
--}
--
--/*
-- * SHA224FinalBits
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 35]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA224FinalBits( SHA224Context *context,
-- const uint8_t message_bits, unsigned int length)
--{
-- return SHA256FinalBits(context, message_bits, length);
--}
--
--/*
-- * SHA224Result
-- *
-- * Description:
-- * This function will return the 224-bit message
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 28th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA224Result(SHA224Context *context,
-- uint8_t Message_Digest[SHA224HashSize])
--{
-- return SHA224_256ResultN(context, Message_Digest, SHA224HashSize);
--}
--
--/*
-- * SHA256Reset
--
--
--
--Eastlake 3rd & Hansen Informational [Page 36]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- * Description:
-- * This function will initialize the SHA256Context in preparation
-- * for computing a new SHA256 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA256Reset(SHA256Context *context)
--{
-- return SHA224_256Reset(context, SHA256_H0);
--}
--
--/*
-- * SHA256Input
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA256Input(SHA256Context *context, const uint8_t *message_array,
-- unsigned int length)
--{
-- if (!length)
-- return shaSuccess;
--
-- if (!context || !message_array)
-- return shaNull;
--
-- if (context->Computed) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
--
--
--
--Eastlake 3rd & Hansen Informational [Page 37]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- }
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- while (length-- && !context->Corrupted) {
-- context->Message_Block[context->Message_Block_Index++] =
-- (*message_array & 0xFF);
--
-- if (!SHA224_256AddLength(context, 8) &&
-- (context->Message_Block_Index == SHA256_Message_Block_Size))
-- SHA224_256ProcessMessageBlock(context);
--
-- message_array++;
-- }
--
-- return shaSuccess;
--
--}
--
--/*
-- * SHA256FinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA256FinalBits(SHA256Context *context,
-- const uint8_t message_bits, unsigned int length)
--{
-- uint8_t masks[8] = {
-- /* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
-- /* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
-- /* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
-- /* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
-- };
--
--
--
--Eastlake 3rd & Hansen Informational [Page 38]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- uint8_t markbit[8] = {
-- /* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
-- /* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
-- /* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
-- /* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
-- };
--
-- if (!length)
-- return shaSuccess;
--
-- if (!context)
-- return shaNull;
--
-- if ((context->Computed) || (length >= 8) || (length == 0)) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
-- }
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- SHA224_256AddLength(context, length);
-- SHA224_256Finalize(context, (uint8_t)
-- ((message_bits & masks[length]) | markbit[length]));
--
-- return shaSuccess;
--}
--
--/*
-- * SHA256Result
-- *
-- * Description:
-- * This function will return the 256-bit message
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 32nd element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int SHA256Result(SHA256Context *context, uint8_t Message_Digest[])
--{
--
--
--
--Eastlake 3rd & Hansen Informational [Page 39]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- return SHA224_256ResultN(context, Message_Digest, SHA256HashSize);
--}
--
--/*
-- * SHA224_256Finalize
-- *
-- * Description:
-- * This helper function finishes off the digest calculations.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--static void SHA224_256Finalize(SHA256Context *context,
-- uint8_t Pad_Byte)
--{
-- int i;
-- SHA224_256PadMessage(context, Pad_Byte);
-- /* message may be sensitive, so clear it out */
-- for (i = 0; i < SHA256_Message_Block_Size; ++i)
-- context->Message_Block[i] = 0;
-- context->Length_Low = 0; /* and clear length */
-- context->Length_High = 0;
-- context->Computed = 1;
--}
--
--/*
-- * SHA224_256PadMessage
-- *
-- * Description:
-- * According to the standard, the message must be padded to an
-- * even 512 bits. The first padding bit must be a '1'. The
-- * last 64 bits represent the length of the original message.
-- * All bits in between should be 0. This helper function will pad
-- * the message according to those rules by filling the
-- * Message_Block array accordingly. When it returns, it can be
-- * assumed that the message digest has been computed.
-- *
-- * Parameters:
-- * context: [in/out]
--
--
--
--Eastlake 3rd & Hansen Informational [Page 40]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * The context to pad
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * Nothing.
-- */
--static void SHA224_256PadMessage(SHA256Context *context,
-- uint8_t Pad_Byte)
--{
-- /*
-- * Check to see if the current message block is too small to hold
-- * the initial padding bits and length. If so, we will pad the
-- * block, process it, and then continue padding into a second
-- * block.
-- */
-- if (context->Message_Block_Index >= (SHA256_Message_Block_Size-8)) {
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
-- while (context->Message_Block_Index < SHA256_Message_Block_Size)
-- context->Message_Block[context->Message_Block_Index++] = 0;
-- SHA224_256ProcessMessageBlock(context);
-- } else
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
--
-- while (context->Message_Block_Index < (SHA256_Message_Block_Size-8))
-- context->Message_Block[context->Message_Block_Index++] = 0;
--
-- /*
-- * Store the message length as the last 8 octets
-- */
-- context->Message_Block[56] = (uint8_t)(context->Length_High >> 24);
-- context->Message_Block[57] = (uint8_t)(context->Length_High >> 16);
-- context->Message_Block[58] = (uint8_t)(context->Length_High >> 8);
-- context->Message_Block[59] = (uint8_t)(context->Length_High);
-- context->Message_Block[60] = (uint8_t)(context->Length_Low >> 24);
-- context->Message_Block[61] = (uint8_t)(context->Length_Low >> 16);
-- context->Message_Block[62] = (uint8_t)(context->Length_Low >> 8);
-- context->Message_Block[63] = (uint8_t)(context->Length_Low);
--
-- SHA224_256ProcessMessageBlock(context);
--}
--
--/*
-- * SHA224_256ProcessMessageBlock
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 41]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Description:
-- * This function will process the next 512 bits of the message
-- * stored in the Message_Block array.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- *
-- * Returns:
-- * Nothing.
-- *
-- * Comments:
-- * Many of the variable names in this code, especially the
-- * single character names, were used because those were the
-- * names used in the publication.
-- */
--static void SHA224_256ProcessMessageBlock(SHA256Context *context)
--{
-- /* Constants defined in FIPS-180-2, section 4.2.2 */
-- static const uint32_t K[64] = {
-- 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b,
-- 0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01,
-- 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7,
-- 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
-- 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152,
-- 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
-- 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc,
-- 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
-- 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819,
-- 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08,
-- 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f,
-- 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
-- 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
-- };
-- int t, t4; /* Loop counter */
-- uint32_t temp1, temp2; /* Temporary word value */
-- uint32_t W[64]; /* Word sequence */
-- uint32_t A, B, C, D, E, F, G, H; /* Word buffers */
--
-- /*
-- * Initialize the first 16 words in the array W
-- */
-- for (t = t4 = 0; t < 16; t++, t4 += 4)
-- W[t] = (((uint32_t)context->Message_Block[t4]) << 24) |
-- (((uint32_t)context->Message_Block[t4 + 1]) << 16) |
-- (((uint32_t)context->Message_Block[t4 + 2]) << 8) |
-- (((uint32_t)context->Message_Block[t4 + 3]));
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 42]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- for (t = 16; t < 64; t++)
-- W[t] = SHA256_sigma1(W[t-2]) + W[t-7] +
-- SHA256_sigma0(W[t-15]) + W[t-16];
--
-- A = context->Intermediate_Hash[0];
-- B = context->Intermediate_Hash[1];
-- C = context->Intermediate_Hash[2];
-- D = context->Intermediate_Hash[3];
-- E = context->Intermediate_Hash[4];
-- F = context->Intermediate_Hash[5];
-- G = context->Intermediate_Hash[6];
-- H = context->Intermediate_Hash[7];
--
-- for (t = 0; t < 64; t++) {
-- temp1 = H + SHA256_SIGMA1(E) + SHA_Ch(E,F,G) + K[t] + W[t];
-- temp2 = SHA256_SIGMA0(A) + SHA_Maj(A,B,C);
-- H = G;
-- G = F;
-- F = E;
-- E = D + temp1;
-- D = C;
-- C = B;
-- B = A;
-- A = temp1 + temp2;
-- }
--
-- context->Intermediate_Hash[0] += A;
-- context->Intermediate_Hash[1] += B;
-- context->Intermediate_Hash[2] += C;
-- context->Intermediate_Hash[3] += D;
-- context->Intermediate_Hash[4] += E;
-- context->Intermediate_Hash[5] += F;
-- context->Intermediate_Hash[6] += G;
-- context->Intermediate_Hash[7] += H;
--
-- context->Message_Block_Index = 0;
--}
--
--/*
-- * SHA224_256Reset
-- *
-- * Description:
-- * This helper function will initialize the SHA256Context in
-- * preparation for computing a new SHA256 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 43]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * H0
-- * The initial hash value to use.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--static int SHA224_256Reset(SHA256Context *context, uint32_t *H0)
--{
-- if (!context)
-- return shaNull;
--
-- context->Length_Low = 0;
-- context->Length_High = 0;
-- context->Message_Block_Index = 0;
--
-- context->Intermediate_Hash[0] = H0[0];
-- context->Intermediate_Hash[1] = H0[1];
-- context->Intermediate_Hash[2] = H0[2];
-- context->Intermediate_Hash[3] = H0[3];
-- context->Intermediate_Hash[4] = H0[4];
-- context->Intermediate_Hash[5] = H0[5];
-- context->Intermediate_Hash[6] = H0[6];
-- context->Intermediate_Hash[7] = H0[7];
--
-- context->Computed = 0;
-- context->Corrupted = 0;
--
-- return shaSuccess;
--}
--
--/*
-- * SHA224_256ResultN
-- *
-- * Description:
-- * This helper function will return the 224-bit or 256-bit message
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 28th/32nd element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- * HashSize: [in]
-- * The size of the hash, either 28 or 32.
-- *
-- * Returns:
--
--
--
--Eastlake 3rd & Hansen Informational [Page 44]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * sha Error Code.
-- */
--static int SHA224_256ResultN(SHA256Context *context,
-- uint8_t Message_Digest[], int HashSize)
--{
-- int i;
--
-- if (!context || !Message_Digest)
-- return shaNull;
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- if (!context->Computed)
-- SHA224_256Finalize(context, 0x80);
--
-- for (i = 0; i < HashSize; ++i)
-- Message_Digest[i] = (uint8_t)
-- (context->Intermediate_Hash[i>>2] >> 8 * ( 3 - ( i & 0x03 ) ));
--
-- return shaSuccess;
--}
--
--8.2.3. sha384-512.c
--
--/*************************** sha384-512.c ***************************/
--/********************* See RFC 4634 for details *********************/
--/*
-- * Description:
-- * This file implements the Secure Hash Signature Standard
-- * algorithms as defined in the National Institute of Standards
-- * and Technology Federal Information Processing Standards
-- * Publication (FIPS PUB) 180-1 published on April 17, 1995, 180-2
-- * published on August 1, 2002, and the FIPS PUB 180-2 Change
-- * Notice published on February 28, 2004.
-- *
-- * A combined document showing all algorithms is available at
-- * http://csrc.nist.gov/publications/fips/
-- * fips180-2/fips180-2withchangenotice.pdf
-- *
-- * The SHA-384 and SHA-512 algorithms produce 384-bit and 512-bit
-- * message digests for a given data stream. It should take about
-- * 2**n steps to find a message with the same digest as a given
-- * message and 2**(n/2) to find any two messages with the same
-- * digest, when n is the digest size in bits. Therefore, this
-- * algorithm can serve as a means of providing a
-- * "fingerprint" for a message.
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 45]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Portability Issues:
-- * SHA-384 and SHA-512 are defined in terms of 64-bit "words",
-- * but if USE_32BIT_ONLY is #defined, this code is implemented in
-- * terms of 32-bit "words". This code uses <stdint.h> (included
-- * via "sha.h") to define the 64, 32 and 8 bit unsigned integer
-- * types. If your C compiler does not support 64 bit unsigned
-- * integers, and you do not #define USE_32BIT_ONLY, this code is
-- * not appropriate.
-- *
-- * Caveats:
-- * SHA-384 and SHA-512 are designed to work with messages less
-- * than 2^128 bits long. This implementation uses
-- * SHA384/512Input() to hash the bits that are a multiple of the
-- * size of an 8-bit character, and then uses SHA384/256FinalBits()
-- * to hash the final few bits of the input.
-- *
-- */
--
--#include "sha.h"
--#include "sha-private.h"
--
--#ifdef USE_32BIT_ONLY
--/*
-- * Define 64-bit arithmetic in terms of 32-bit arithmetic.
-- * Each 64-bit number is represented in a 2-word array.
-- * All macros are defined such that the result is the last parameter.
-- */
--
--/*
-- * Define shift, rotate left and rotate right functions
-- */
--#define SHA512_SHR(bits, word, ret) ( \
-- /* (((uint64_t)((word))) >> (bits)) */ \
-- (ret)[0] = (((bits) < 32) && ((bits) >= 0)) ? \
-- ((word)[0] >> (bits)) : 0, \
-- (ret)[1] = ((bits) > 32) ? ((word)[0] >> ((bits) - 32)) : \
-- ((bits) == 32) ? (word)[0] : \
-- ((bits) >= 0) ? \
-- (((word)[0] << (32 - (bits))) | \
-- ((word)[1] >> (bits))) : 0 )
--
--#define SHA512_SHL(bits, word, ret) ( \
-- /* (((uint64_t)(word)) << (bits)) */ \
-- (ret)[0] = ((bits) > 32) ? ((word)[1] << ((bits) - 32)) : \
-- ((bits) == 32) ? (word)[1] : \
-- ((bits) >= 0) ? \
-- (((word)[0] << (bits)) | \
-- ((word)[1] >> (32 - (bits)))) : \
--
--
--
--Eastlake 3rd & Hansen Informational [Page 46]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- 0, \
-- (ret)[1] = (((bits) < 32) && ((bits) >= 0)) ? \
-- ((word)[1] << (bits)) : 0 )
--
--/*
-- * Define 64-bit OR
-- */
--#define SHA512_OR(word1, word2, ret) ( \
-- (ret)[0] = (word1)[0] | (word2)[0], \
-- (ret)[1] = (word1)[1] | (word2)[1] )
--
--/*
-- * Define 64-bit XOR
-- */
--#define SHA512_XOR(word1, word2, ret) ( \
-- (ret)[0] = (word1)[0] ^ (word2)[0], \
-- (ret)[1] = (word1)[1] ^ (word2)[1] )
--
--/*
-- * Define 64-bit AND
-- */
--#define SHA512_AND(word1, word2, ret) ( \
-- (ret)[0] = (word1)[0] & (word2)[0], \
-- (ret)[1] = (word1)[1] & (word2)[1] )
--
--/*
-- * Define 64-bit TILDA
-- */
--#define SHA512_TILDA(word, ret) \
-- ( (ret)[0] = ~(word)[0], (ret)[1] = ~(word)[1] )
--
--/*
-- * Define 64-bit ADD
-- */
--#define SHA512_ADD(word1, word2, ret) ( \
-- (ret)[1] = (word1)[1], (ret)[1] += (word2)[1], \
-- (ret)[0] = (word1)[0] + (word2)[0] + ((ret)[1] < (word1)[1]) )
--
--/*
-- * Add the 4word value in word2 to word1.
-- */
--static uint32_t ADDTO4_temp, ADDTO4_temp2;
--#define SHA512_ADDTO4(word1, word2) ( \
-- ADDTO4_temp = (word1)[3], \
-- (word1)[3] += (word2)[3], \
-- ADDTO4_temp2 = (word1)[2], \
-- (word1)[2] += (word2)[2] + ((word1)[3] < ADDTO4_temp), \
-- ADDTO4_temp = (word1)[1], \
--
--
--
--Eastlake 3rd & Hansen Informational [Page 47]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- (word1)[1] += (word2)[1] + ((word1)[2] < ADDTO4_temp2), \
-- (word1)[0] += (word2)[0] + ((word1)[1] < ADDTO4_temp) )
--
--/*
-- * Add the 2word value in word2 to word1.
-- */
--static uint32_t ADDTO2_temp;
--#define SHA512_ADDTO2(word1, word2) ( \
-- ADDTO2_temp = (word1)[1], \
-- (word1)[1] += (word2)[1], \
-- (word1)[0] += (word2)[0] + ((word1)[1] < ADDTO2_temp) )
--
--/*
-- * SHA rotate ((word >> bits) | (word << (64-bits)))
-- */
--static uint32_t ROTR_temp1[2], ROTR_temp2[2];
--#define SHA512_ROTR(bits, word, ret) ( \
-- SHA512_SHR((bits), (word), ROTR_temp1), \
-- SHA512_SHL(64-(bits), (word), ROTR_temp2), \
-- SHA512_OR(ROTR_temp1, ROTR_temp2, (ret)) )
--
--/*
-- * Define the SHA SIGMA and sigma macros
-- * SHA512_ROTR(28,word) ^ SHA512_ROTR(34,word) ^ SHA512_ROTR(39,word)
-- */
--static uint32_t SIGMA0_temp1[2], SIGMA0_temp2[2],
-- SIGMA0_temp3[2], SIGMA0_temp4[2];
--#define SHA512_SIGMA0(word, ret) ( \
-- SHA512_ROTR(28, (word), SIGMA0_temp1), \
-- SHA512_ROTR(34, (word), SIGMA0_temp2), \
-- SHA512_ROTR(39, (word), SIGMA0_temp3), \
-- SHA512_XOR(SIGMA0_temp2, SIGMA0_temp3, SIGMA0_temp4), \
-- SHA512_XOR(SIGMA0_temp1, SIGMA0_temp4, (ret)) )
--
--/*
-- * SHA512_ROTR(14,word) ^ SHA512_ROTR(18,word) ^ SHA512_ROTR(41,word)
-- */
--static uint32_t SIGMA1_temp1[2], SIGMA1_temp2[2],
-- SIGMA1_temp3[2], SIGMA1_temp4[2];
--#define SHA512_SIGMA1(word, ret) ( \
-- SHA512_ROTR(14, (word), SIGMA1_temp1), \
-- SHA512_ROTR(18, (word), SIGMA1_temp2), \
-- SHA512_ROTR(41, (word), SIGMA1_temp3), \
-- SHA512_XOR(SIGMA1_temp2, SIGMA1_temp3, SIGMA1_temp4), \
-- SHA512_XOR(SIGMA1_temp1, SIGMA1_temp4, (ret)) )
--
--/*
-- * (SHA512_ROTR( 1,word) ^ SHA512_ROTR( 8,word) ^ SHA512_SHR( 7,word))
--
--
--
--Eastlake 3rd & Hansen Informational [Page 48]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- */
--static uint32_t sigma0_temp1[2], sigma0_temp2[2],
-- sigma0_temp3[2], sigma0_temp4[2];
--#define SHA512_sigma0(word, ret) ( \
-- SHA512_ROTR( 1, (word), sigma0_temp1), \
-- SHA512_ROTR( 8, (word), sigma0_temp2), \
-- SHA512_SHR( 7, (word), sigma0_temp3), \
-- SHA512_XOR(sigma0_temp2, sigma0_temp3, sigma0_temp4), \
-- SHA512_XOR(sigma0_temp1, sigma0_temp4, (ret)) )
--
--/*
-- * (SHA512_ROTR(19,word) ^ SHA512_ROTR(61,word) ^ SHA512_SHR( 6,word))
-- */
--static uint32_t sigma1_temp1[2], sigma1_temp2[2],
-- sigma1_temp3[2], sigma1_temp4[2];
--#define SHA512_sigma1(word, ret) ( \
-- SHA512_ROTR(19, (word), sigma1_temp1), \
-- SHA512_ROTR(61, (word), sigma1_temp2), \
-- SHA512_SHR( 6, (word), sigma1_temp3), \
-- SHA512_XOR(sigma1_temp2, sigma1_temp3, sigma1_temp4), \
-- SHA512_XOR(sigma1_temp1, sigma1_temp4, (ret)) )
--
--#undef SHA_Ch
--#undef SHA_Maj
--
--#ifndef USE_MODIFIED_MACROS
--/*
-- * These definitions are the ones used in FIPS-180-2, section 4.1.3
-- * Ch(x,y,z) ((x & y) ^ (~x & z))
-- */
--static uint32_t Ch_temp1[2], Ch_temp2[2], Ch_temp3[2];
--#define SHA_Ch(x, y, z, ret) ( \
-- SHA512_AND(x, y, Ch_temp1), \
-- SHA512_TILDA(x, Ch_temp2), \
-- SHA512_AND(Ch_temp2, z, Ch_temp3), \
-- SHA512_XOR(Ch_temp1, Ch_temp3, (ret)) )
--/*
-- * Maj(x,y,z) (((x)&(y)) ^ ((x)&(z)) ^ ((y)&(z)))
-- */
--static uint32_t Maj_temp1[2], Maj_temp2[2],
-- Maj_temp3[2], Maj_temp4[2];
--#define SHA_Maj(x, y, z, ret) ( \
-- SHA512_AND(x, y, Maj_temp1), \
-- SHA512_AND(x, z, Maj_temp2), \
-- SHA512_AND(y, z, Maj_temp3), \
-- SHA512_XOR(Maj_temp2, Maj_temp3, Maj_temp4), \
-- SHA512_XOR(Maj_temp1, Maj_temp4, (ret)) )
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 49]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--#else /* !USE_32BIT_ONLY */
--/*
-- * These definitions are potentially faster equivalents for the ones
-- * used in FIPS-180-2, section 4.1.3.
-- * ((x & y) ^ (~x & z)) becomes
-- * ((x & (y ^ z)) ^ z)
-- */
--#define SHA_Ch(x, y, z, ret) ( \
-- (ret)[0] = (((x)[0] & ((y)[0] ^ (z)[0])) ^ (z)[0]), \
-- (ret)[1] = (((x)[1] & ((y)[1] ^ (z)[1])) ^ (z)[1]) )
--
--/*
-- * ((x & y) ^ (x & z) ^ (y & z)) becomes
-- * ((x & (y | z)) | (y & z))
-- */
--#define SHA_Maj(x, y, z, ret) ( \
-- ret[0] = (((x)[0] & ((y)[0] | (z)[0])) | ((y)[0] & (z)[0])), \
-- ret[1] = (((x)[1] & ((y)[1] | (z)[1])) | ((y)[1] & (z)[1])) )
--#endif /* USE_MODIFIED_MACROS */
--
--/*
-- * add "length" to the length
-- */
--static uint32_t addTemp[4] = { 0, 0, 0, 0 };
--#define SHA384_512AddLength(context, length) ( \
-- addTemp[3] = (length), SHA512_ADDTO4((context)->Length, addTemp), \
-- (context)->Corrupted = (((context)->Length[3] == 0) && \
-- ((context)->Length[2] == 0) && ((context)->Length[1] == 0) && \
-- ((context)->Length[0] < 8)) ? 1 : 0 )
--
--/* Local Function Prototypes */
--static void SHA384_512Finalize(SHA512Context *context,
-- uint8_t Pad_Byte);
--static void SHA384_512PadMessage(SHA512Context *context,
-- uint8_t Pad_Byte);
--static void SHA384_512ProcessMessageBlock(SHA512Context *context);
--static int SHA384_512Reset(SHA512Context *context, uint32_t H0[]);
--static int SHA384_512ResultN( SHA512Context *context,
-- uint8_t Message_Digest[], int HashSize);
--
--/* Initial Hash Values: FIPS-180-2 sections 5.3.3 and 5.3.4 */
--static uint32_t SHA384_H0[SHA512HashSize/4] = {
-- 0xCBBB9D5D, 0xC1059ED8, 0x629A292A, 0x367CD507, 0x9159015A,
-- 0x3070DD17, 0x152FECD8, 0xF70E5939, 0x67332667, 0xFFC00B31,
-- 0x8EB44A87, 0x68581511, 0xDB0C2E0D, 0x64F98FA7, 0x47B5481D,
-- 0xBEFA4FA4
--};
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 50]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--static uint32_t SHA512_H0[SHA512HashSize/4] = {
-- 0x6A09E667, 0xF3BCC908, 0xBB67AE85, 0x84CAA73B, 0x3C6EF372,
-- 0xFE94F82B, 0xA54FF53A, 0x5F1D36F1, 0x510E527F, 0xADE682D1,
-- 0x9B05688C, 0x2B3E6C1F, 0x1F83D9AB, 0xFB41BD6B, 0x5BE0CD19,
-- 0x137E2179
--};
--
--#else /* !USE_32BIT_ONLY */
--
--/* Define the SHA shift, rotate left and rotate right macro */
--#define SHA512_SHR(bits,word) (((uint64_t)(word)) >> (bits))
--#define SHA512_ROTR(bits,word) ((((uint64_t)(word)) >> (bits)) | \
-- (((uint64_t)(word)) << (64-(bits))))
--
--/* Define the SHA SIGMA and sigma macros */
--#define SHA512_SIGMA0(word) \
-- (SHA512_ROTR(28,word) ^ SHA512_ROTR(34,word) ^ SHA512_ROTR(39,word))
--#define SHA512_SIGMA1(word) \
-- (SHA512_ROTR(14,word) ^ SHA512_ROTR(18,word) ^ SHA512_ROTR(41,word))
--#define SHA512_sigma0(word) \
-- (SHA512_ROTR( 1,word) ^ SHA512_ROTR( 8,word) ^ SHA512_SHR( 7,word))
--#define SHA512_sigma1(word) \
-- (SHA512_ROTR(19,word) ^ SHA512_ROTR(61,word) ^ SHA512_SHR( 6,word))
--
--/*
-- * add "length" to the length
-- */
--static uint64_t addTemp;
--#define SHA384_512AddLength(context, length) \
-- (addTemp = context->Length_Low, context->Corrupted = \
-- ((context->Length_Low += length) < addTemp) && \
-- (++context->Length_High == 0) ? 1 : 0)
--
--/* Local Function Prototypes */
--static void SHA384_512Finalize(SHA512Context *context,
-- uint8_t Pad_Byte);
--static void SHA384_512PadMessage(SHA512Context *context,
-- uint8_t Pad_Byte);
--static void SHA384_512ProcessMessageBlock(SHA512Context *context);
--static int SHA384_512Reset(SHA512Context *context, uint64_t H0[]);
--static int SHA384_512ResultN(SHA512Context *context,
-- uint8_t Message_Digest[], int HashSize);
--
--/* Initial Hash Values: FIPS-180-2 sections 5.3.3 and 5.3.4 */
--static uint64_t SHA384_H0[] = {
-- 0xCBBB9D5DC1059ED8ll, 0x629A292A367CD507ll, 0x9159015A3070DD17ll,
-- 0x152FECD8F70E5939ll, 0x67332667FFC00B31ll, 0x8EB44A8768581511ll,
-- 0xDB0C2E0D64F98FA7ll, 0x47B5481DBEFA4FA4ll
--
--
--
--Eastlake 3rd & Hansen Informational [Page 51]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--};
--static uint64_t SHA512_H0[] = {
-- 0x6A09E667F3BCC908ll, 0xBB67AE8584CAA73Bll, 0x3C6EF372FE94F82Bll,
-- 0xA54FF53A5F1D36F1ll, 0x510E527FADE682D1ll, 0x9B05688C2B3E6C1Fll,
-- 0x1F83D9ABFB41BD6Bll, 0x5BE0CD19137E2179ll
--};
--
--#endif /* USE_32BIT_ONLY */
--
--/*
-- * SHA384Reset
-- *
-- * Description:
-- * This function will initialize the SHA384Context in preparation
-- * for computing a new SHA384 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA384Reset(SHA384Context *context)
--{
-- return SHA384_512Reset(context, SHA384_H0);
--}
--
--/*
-- * SHA384Input
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 52]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- */
--int SHA384Input(SHA384Context *context,
-- const uint8_t *message_array, unsigned int length)
--{
-- return SHA512Input(context, message_array, length);
--}
--
--/*
-- * SHA384FinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA384FinalBits(SHA384Context *context,
-- const uint8_t message_bits, unsigned int length)
--{
-- return SHA512FinalBits(context, message_bits, length);
--}
--
--/*
-- * SHA384Result
-- *
-- * Description:
-- * This function will return the 384-bit message
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 48th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 53]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA384Result(SHA384Context *context,
-- uint8_t Message_Digest[SHA384HashSize])
--{
-- return SHA384_512ResultN(context, Message_Digest, SHA384HashSize);
--}
--
--/*
-- * SHA512Reset
-- *
-- * Description:
-- * This function will initialize the SHA512Context in preparation
-- * for computing a new SHA512 message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA512Reset(SHA512Context *context)
--{
-- return SHA384_512Reset(context, SHA512_H0);
--}
--
--/*
-- * SHA512Input
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 54]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- */
--int SHA512Input(SHA512Context *context,
-- const uint8_t *message_array,
-- unsigned int length)
--{
-- if (!length)
-- return shaSuccess;
--
-- if (!context || !message_array)
-- return shaNull;
--
-- if (context->Computed) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
-- }
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- while (length-- && !context->Corrupted) {
-- context->Message_Block[context->Message_Block_Index++] =
-- (*message_array & 0xFF);
--
-- if (!SHA384_512AddLength(context, 8) &&
-- (context->Message_Block_Index == SHA512_Message_Block_Size))
-- SHA384_512ProcessMessageBlock(context);
--
-- message_array++;
-- }
--
-- return shaSuccess;
--}
--
--/*
-- * SHA512FinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
--
--
--
--Eastlake 3rd & Hansen Informational [Page 55]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int SHA512FinalBits(SHA512Context *context,
-- const uint8_t message_bits, unsigned int length)
--{
-- uint8_t masks[8] = {
-- /* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
-- /* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
-- /* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
-- /* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
-- };
-- uint8_t markbit[8] = {
-- /* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
-- /* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
-- /* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
-- /* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
-- };
--
-- if (!length)
-- return shaSuccess;
--
-- if (!context)
-- return shaNull;
--
-- if ((context->Computed) || (length >= 8) || (length == 0)) {
-- context->Corrupted = shaStateError;
-- return shaStateError;
-- }
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- SHA384_512AddLength(context, length);
-- SHA384_512Finalize(context, (uint8_t)
-- ((message_bits & masks[length]) | markbit[length]));
--
-- return shaSuccess;
--}
--
--/*
-- * SHA384_512Finalize
-- *
-- * Description:
-- * This helper function finishes off the digest calculations.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 56]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--static void SHA384_512Finalize(SHA512Context *context,
-- uint8_t Pad_Byte)
--{
-- int_least16_t i;
-- SHA384_512PadMessage(context, Pad_Byte);
-- /* message may be sensitive, clear it out */
-- for (i = 0; i < SHA512_Message_Block_Size; ++i)
-- context->Message_Block[i] = 0;
--#ifdef USE_32BIT_ONLY /* and clear length */
-- context->Length[0] = context->Length[1] = 0;
-- context->Length[2] = context->Length[3] = 0;
--#else /* !USE_32BIT_ONLY */
-- context->Length_Low = 0;
-- context->Length_High = 0;
--#endif /* USE_32BIT_ONLY */
-- context->Computed = 1;
--}
--
--/*
-- * SHA512Result
-- *
-- * Description:
-- * This function will return the 512-bit message
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 64th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
-- * Returns:
--
--
--
--Eastlake 3rd & Hansen Informational [Page 57]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * sha Error Code.
-- *
-- */
--int SHA512Result(SHA512Context *context,
-- uint8_t Message_Digest[SHA512HashSize])
--{
-- return SHA384_512ResultN(context, Message_Digest, SHA512HashSize);
--}
--
--/*
-- * SHA384_512PadMessage
-- *
-- * Description:
-- * According to the standard, the message must be padded to an
-- * even 1024 bits. The first padding bit must be a '1'. The
-- * last 128 bits represent the length of the original message.
-- * All bits in between should be 0. This helper function will
-- * pad the message according to those rules by filling the
-- * Message_Block array accordingly. When it returns, it can be
-- * assumed that the message digest has been computed.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to pad
-- * Pad_Byte: [in]
-- * The last byte to add to the digest before the 0-padding
-- * and length. This will contain the last bits of the message
-- * followed by another single bit. If the message was an
-- * exact multiple of 8-bits long, Pad_Byte will be 0x80.
-- *
-- * Returns:
-- * Nothing.
-- *
-- */
--static void SHA384_512PadMessage(SHA512Context *context,
-- uint8_t Pad_Byte)
--{
-- /*
-- * Check to see if the current message block is too small to hold
-- * the initial padding bits and length. If so, we will pad the
-- * block, process it, and then continue padding into a second
-- * block.
-- */
-- if (context->Message_Block_Index >= (SHA512_Message_Block_Size-16)) {
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
-- while (context->Message_Block_Index < SHA512_Message_Block_Size)
-- context->Message_Block[context->Message_Block_Index++] = 0;
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 58]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- SHA384_512ProcessMessageBlock(context);
-- } else
-- context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
--
-- while (context->Message_Block_Index < (SHA512_Message_Block_Size-16))
-- context->Message_Block[context->Message_Block_Index++] = 0;
--
-- /*
-- * Store the message length as the last 16 octets
-- */
--#ifdef USE_32BIT_ONLY
-- context->Message_Block[112] = (uint8_t)(context->Length[0] >> 24);
-- context->Message_Block[113] = (uint8_t)(context->Length[0] >> 16);
-- context->Message_Block[114] = (uint8_t)(context->Length[0] >> 8);
-- context->Message_Block[115] = (uint8_t)(context->Length[0]);
-- context->Message_Block[116] = (uint8_t)(context->Length[1] >> 24);
-- context->Message_Block[117] = (uint8_t)(context->Length[1] >> 16);
-- context->Message_Block[118] = (uint8_t)(context->Length[1] >> 8);
-- context->Message_Block[119] = (uint8_t)(context->Length[1]);
--
-- context->Message_Block[120] = (uint8_t)(context->Length[2] >> 24);
-- context->Message_Block[121] = (uint8_t)(context->Length[2] >> 16);
-- context->Message_Block[122] = (uint8_t)(context->Length[2] >> 8);
-- context->Message_Block[123] = (uint8_t)(context->Length[2]);
-- context->Message_Block[124] = (uint8_t)(context->Length[3] >> 24);
-- context->Message_Block[125] = (uint8_t)(context->Length[3] >> 16);
-- context->Message_Block[126] = (uint8_t)(context->Length[3] >> 8);
-- context->Message_Block[127] = (uint8_t)(context->Length[3]);
--#else /* !USE_32BIT_ONLY */
-- context->Message_Block[112] = (uint8_t)(context->Length_High >> 56);
-- context->Message_Block[113] = (uint8_t)(context->Length_High >> 48);
-- context->Message_Block[114] = (uint8_t)(context->Length_High >> 40);
-- context->Message_Block[115] = (uint8_t)(context->Length_High >> 32);
-- context->Message_Block[116] = (uint8_t)(context->Length_High >> 24);
-- context->Message_Block[117] = (uint8_t)(context->Length_High >> 16);
-- context->Message_Block[118] = (uint8_t)(context->Length_High >> 8);
-- context->Message_Block[119] = (uint8_t)(context->Length_High);
--
-- context->Message_Block[120] = (uint8_t)(context->Length_Low >> 56);
-- context->Message_Block[121] = (uint8_t)(context->Length_Low >> 48);
-- context->Message_Block[122] = (uint8_t)(context->Length_Low >> 40);
-- context->Message_Block[123] = (uint8_t)(context->Length_Low >> 32);
-- context->Message_Block[124] = (uint8_t)(context->Length_Low >> 24);
-- context->Message_Block[125] = (uint8_t)(context->Length_Low >> 16);
-- context->Message_Block[126] = (uint8_t)(context->Length_Low >> 8);
-- context->Message_Block[127] = (uint8_t)(context->Length_Low);
--#endif /* USE_32BIT_ONLY */
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 59]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- SHA384_512ProcessMessageBlock(context);
--}
--
--/*
-- * SHA384_512ProcessMessageBlock
-- *
-- * Description:
-- * This helper function will process the next 1024 bits of the
-- * message stored in the Message_Block array.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- *
-- * Returns:
-- * Nothing.
-- *
-- * Comments:
-- * Many of the variable names in this code, especially the
-- * single character names, were used because those were the
-- * names used in the publication.
-- *
-- *
-- */
--static void SHA384_512ProcessMessageBlock(SHA512Context *context)
--{
-- /* Constants defined in FIPS-180-2, section 4.2.3 */
--#ifdef USE_32BIT_ONLY
-- static const uint32_t K[80*2] = {
-- 0x428A2F98, 0xD728AE22, 0x71374491, 0x23EF65CD, 0xB5C0FBCF,
-- 0xEC4D3B2F, 0xE9B5DBA5, 0x8189DBBC, 0x3956C25B, 0xF348B538,
-- 0x59F111F1, 0xB605D019, 0x923F82A4, 0xAF194F9B, 0xAB1C5ED5,
-- 0xDA6D8118, 0xD807AA98, 0xA3030242, 0x12835B01, 0x45706FBE,
-- 0x243185BE, 0x4EE4B28C, 0x550C7DC3, 0xD5FFB4E2, 0x72BE5D74,
-- 0xF27B896F, 0x80DEB1FE, 0x3B1696B1, 0x9BDC06A7, 0x25C71235,
-- 0xC19BF174, 0xCF692694, 0xE49B69C1, 0x9EF14AD2, 0xEFBE4786,
-- 0x384F25E3, 0x0FC19DC6, 0x8B8CD5B5, 0x240CA1CC, 0x77AC9C65,
-- 0x2DE92C6F, 0x592B0275, 0x4A7484AA, 0x6EA6E483, 0x5CB0A9DC,
-- 0xBD41FBD4, 0x76F988DA, 0x831153B5, 0x983E5152, 0xEE66DFAB,
-- 0xA831C66D, 0x2DB43210, 0xB00327C8, 0x98FB213F, 0xBF597FC7,
-- 0xBEEF0EE4, 0xC6E00BF3, 0x3DA88FC2, 0xD5A79147, 0x930AA725,
-- 0x06CA6351, 0xE003826F, 0x14292967, 0x0A0E6E70, 0x27B70A85,
-- 0x46D22FFC, 0x2E1B2138, 0x5C26C926, 0x4D2C6DFC, 0x5AC42AED,
-- 0x53380D13, 0x9D95B3DF, 0x650A7354, 0x8BAF63DE, 0x766A0ABB,
-- 0x3C77B2A8, 0x81C2C92E, 0x47EDAEE6, 0x92722C85, 0x1482353B,
-- 0xA2BFE8A1, 0x4CF10364, 0xA81A664B, 0xBC423001, 0xC24B8B70,
-- 0xD0F89791, 0xC76C51A3, 0x0654BE30, 0xD192E819, 0xD6EF5218,
-- 0xD6990624, 0x5565A910, 0xF40E3585, 0x5771202A, 0x106AA070,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 60]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- 0x32BBD1B8, 0x19A4C116, 0xB8D2D0C8, 0x1E376C08, 0x5141AB53,
-- 0x2748774C, 0xDF8EEB99, 0x34B0BCB5, 0xE19B48A8, 0x391C0CB3,
-- 0xC5C95A63, 0x4ED8AA4A, 0xE3418ACB, 0x5B9CCA4F, 0x7763E373,
-- 0x682E6FF3, 0xD6B2B8A3, 0x748F82EE, 0x5DEFB2FC, 0x78A5636F,
-- 0x43172F60, 0x84C87814, 0xA1F0AB72, 0x8CC70208, 0x1A6439EC,
-- 0x90BEFFFA, 0x23631E28, 0xA4506CEB, 0xDE82BDE9, 0xBEF9A3F7,
-- 0xB2C67915, 0xC67178F2, 0xE372532B, 0xCA273ECE, 0xEA26619C,
-- 0xD186B8C7, 0x21C0C207, 0xEADA7DD6, 0xCDE0EB1E, 0xF57D4F7F,
-- 0xEE6ED178, 0x06F067AA, 0x72176FBA, 0x0A637DC5, 0xA2C898A6,
-- 0x113F9804, 0xBEF90DAE, 0x1B710B35, 0x131C471B, 0x28DB77F5,
-- 0x23047D84, 0x32CAAB7B, 0x40C72493, 0x3C9EBE0A, 0x15C9BEBC,
-- 0x431D67C4, 0x9C100D4C, 0x4CC5D4BE, 0xCB3E42B6, 0x597F299C,
-- 0xFC657E2A, 0x5FCB6FAB, 0x3AD6FAEC, 0x6C44198C, 0x4A475817
-- };
-- int t, t2, t8; /* Loop counter */
-- uint32_t temp1[2], temp2[2], /* Temporary word values */
-- temp3[2], temp4[2], temp5[2];
-- uint32_t W[2*80]; /* Word sequence */
-- uint32_t A[2], B[2], C[2], D[2], /* Word buffers */
-- E[2], F[2], G[2], H[2];
--
-- /* Initialize the first 16 words in the array W */
-- for (t = t2 = t8 = 0; t < 16; t++, t8 += 8) {
-- W[t2++] = ((((uint32_t)context->Message_Block[t8 ])) << 24) |
-- ((((uint32_t)context->Message_Block[t8 + 1])) << 16) |
-- ((((uint32_t)context->Message_Block[t8 + 2])) << 8) |
-- ((((uint32_t)context->Message_Block[t8 + 3])));
-- W[t2++] = ((((uint32_t)context->Message_Block[t8 + 4])) << 24) |
-- ((((uint32_t)context->Message_Block[t8 + 5])) << 16) |
-- ((((uint32_t)context->Message_Block[t8 + 6])) << 8) |
-- ((((uint32_t)context->Message_Block[t8 + 7])));
-- }
--
-- for (t = 16; t < 80; t++, t2 += 2) {
-- /* W[t] = SHA512_sigma1(W[t-2]) + W[t-7] +
-- SHA512_sigma0(W[t-15]) + W[t-16]; */
-- uint32_t *Wt2 = &W[t2-2*2];
-- uint32_t *Wt7 = &W[t2-7*2];
-- uint32_t *Wt15 = &W[t2-15*2];
-- uint32_t *Wt16 = &W[t2-16*2];
-- SHA512_sigma1(Wt2, temp1);
-- SHA512_ADD(temp1, Wt7, temp2);
-- SHA512_sigma0(Wt15, temp1);
-- SHA512_ADD(temp1, Wt16, temp3);
-- SHA512_ADD(temp2, temp3, &W[t2]);
-- }
--
-- A[0] = context->Intermediate_Hash[0];
--
--
--
--Eastlake 3rd & Hansen Informational [Page 61]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- A[1] = context->Intermediate_Hash[1];
-- B[0] = context->Intermediate_Hash[2];
-- B[1] = context->Intermediate_Hash[3];
-- C[0] = context->Intermediate_Hash[4];
-- C[1] = context->Intermediate_Hash[5];
-- D[0] = context->Intermediate_Hash[6];
-- D[1] = context->Intermediate_Hash[7];
-- E[0] = context->Intermediate_Hash[8];
-- E[1] = context->Intermediate_Hash[9];
-- F[0] = context->Intermediate_Hash[10];
-- F[1] = context->Intermediate_Hash[11];
-- G[0] = context->Intermediate_Hash[12];
-- G[1] = context->Intermediate_Hash[13];
-- H[0] = context->Intermediate_Hash[14];
-- H[1] = context->Intermediate_Hash[15];
--
-- for (t = t2 = 0; t < 80; t++, t2 += 2) {
-- /*
-- * temp1 = H + SHA512_SIGMA1(E) + SHA_Ch(E,F,G) + K[t] + W[t];
-- */
-- SHA512_SIGMA1(E,temp1);
-- SHA512_ADD(H, temp1, temp2);
-- SHA_Ch(E,F,G,temp3);
-- SHA512_ADD(temp2, temp3, temp4);
-- SHA512_ADD(&K[t2], &W[t2], temp5);
-- SHA512_ADD(temp4, temp5, temp1);
-- /*
-- * temp2 = SHA512_SIGMA0(A) + SHA_Maj(A,B,C);
-- */
-- SHA512_SIGMA0(A,temp3);
-- SHA_Maj(A,B,C,temp4);
-- SHA512_ADD(temp3, temp4, temp2);
-- H[0] = G[0]; H[1] = G[1];
-- G[0] = F[0]; G[1] = F[1];
-- F[0] = E[0]; F[1] = E[1];
-- SHA512_ADD(D, temp1, E);
-- D[0] = C[0]; D[1] = C[1];
-- C[0] = B[0]; C[1] = B[1];
-- B[0] = A[0]; B[1] = A[1];
-- SHA512_ADD(temp1, temp2, A);
-- }
--
-- SHA512_ADDTO2(&context->Intermediate_Hash[0], A);
-- SHA512_ADDTO2(&context->Intermediate_Hash[2], B);
-- SHA512_ADDTO2(&context->Intermediate_Hash[4], C);
-- SHA512_ADDTO2(&context->Intermediate_Hash[6], D);
-- SHA512_ADDTO2(&context->Intermediate_Hash[8], E);
-- SHA512_ADDTO2(&context->Intermediate_Hash[10], F);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 62]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- SHA512_ADDTO2(&context->Intermediate_Hash[12], G);
-- SHA512_ADDTO2(&context->Intermediate_Hash[14], H);
--
--#else /* !USE_32BIT_ONLY */
-- static const uint64_t K[80] = {
-- 0x428A2F98D728AE22ll, 0x7137449123EF65CDll, 0xB5C0FBCFEC4D3B2Fll,
-- 0xE9B5DBA58189DBBCll, 0x3956C25BF348B538ll, 0x59F111F1B605D019ll,
-- 0x923F82A4AF194F9Bll, 0xAB1C5ED5DA6D8118ll, 0xD807AA98A3030242ll,
-- 0x12835B0145706FBEll, 0x243185BE4EE4B28Cll, 0x550C7DC3D5FFB4E2ll,
-- 0x72BE5D74F27B896Fll, 0x80DEB1FE3B1696B1ll, 0x9BDC06A725C71235ll,
-- 0xC19BF174CF692694ll, 0xE49B69C19EF14AD2ll, 0xEFBE4786384F25E3ll,
-- 0x0FC19DC68B8CD5B5ll, 0x240CA1CC77AC9C65ll, 0x2DE92C6F592B0275ll,
-- 0x4A7484AA6EA6E483ll, 0x5CB0A9DCBD41FBD4ll, 0x76F988DA831153B5ll,
-- 0x983E5152EE66DFABll, 0xA831C66D2DB43210ll, 0xB00327C898FB213Fll,
-- 0xBF597FC7BEEF0EE4ll, 0xC6E00BF33DA88FC2ll, 0xD5A79147930AA725ll,
-- 0x06CA6351E003826Fll, 0x142929670A0E6E70ll, 0x27B70A8546D22FFCll,
-- 0x2E1B21385C26C926ll, 0x4D2C6DFC5AC42AEDll, 0x53380D139D95B3DFll,
-- 0x650A73548BAF63DEll, 0x766A0ABB3C77B2A8ll, 0x81C2C92E47EDAEE6ll,
-- 0x92722C851482353Bll, 0xA2BFE8A14CF10364ll, 0xA81A664BBC423001ll,
-- 0xC24B8B70D0F89791ll, 0xC76C51A30654BE30ll, 0xD192E819D6EF5218ll,
-- 0xD69906245565A910ll, 0xF40E35855771202All, 0x106AA07032BBD1B8ll,
-- 0x19A4C116B8D2D0C8ll, 0x1E376C085141AB53ll, 0x2748774CDF8EEB99ll,
-- 0x34B0BCB5E19B48A8ll, 0x391C0CB3C5C95A63ll, 0x4ED8AA4AE3418ACBll,
-- 0x5B9CCA4F7763E373ll, 0x682E6FF3D6B2B8A3ll, 0x748F82EE5DEFB2FCll,
-- 0x78A5636F43172F60ll, 0x84C87814A1F0AB72ll, 0x8CC702081A6439ECll,
-- 0x90BEFFFA23631E28ll, 0xA4506CEBDE82BDE9ll, 0xBEF9A3F7B2C67915ll,
-- 0xC67178F2E372532Bll, 0xCA273ECEEA26619Cll, 0xD186B8C721C0C207ll,
-- 0xEADA7DD6CDE0EB1Ell, 0xF57D4F7FEE6ED178ll, 0x06F067AA72176FBAll,
-- 0x0A637DC5A2C898A6ll, 0x113F9804BEF90DAEll, 0x1B710B35131C471Bll,
-- 0x28DB77F523047D84ll, 0x32CAAB7B40C72493ll, 0x3C9EBE0A15C9BEBCll,
-- 0x431D67C49C100D4Cll, 0x4CC5D4BECB3E42B6ll, 0x597F299CFC657E2All,
-- 0x5FCB6FAB3AD6FAECll, 0x6C44198C4A475817ll
-- };
-- int t, t8; /* Loop counter */
-- uint64_t temp1, temp2; /* Temporary word value */
-- uint64_t W[80]; /* Word sequence */
-- uint64_t A, B, C, D, E, F, G, H; /* Word buffers */
--
-- /*
-- * Initialize the first 16 words in the array W
-- */
-- for (t = t8 = 0; t < 16; t++, t8 += 8)
-- W[t] = ((uint64_t)(context->Message_Block[t8 ]) << 56) |
-- ((uint64_t)(context->Message_Block[t8 + 1]) << 48) |
-- ((uint64_t)(context->Message_Block[t8 + 2]) << 40) |
-- ((uint64_t)(context->Message_Block[t8 + 3]) << 32) |
-- ((uint64_t)(context->Message_Block[t8 + 4]) << 24) |
-- ((uint64_t)(context->Message_Block[t8 + 5]) << 16) |
--
--
--
--Eastlake 3rd & Hansen Informational [Page 63]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- ((uint64_t)(context->Message_Block[t8 + 6]) << 8) |
-- ((uint64_t)(context->Message_Block[t8 + 7]));
--
-- for (t = 16; t < 80; t++)
-- W[t] = SHA512_sigma1(W[t-2]) + W[t-7] +
-- SHA512_sigma0(W[t-15]) + W[t-16];
--
-- A = context->Intermediate_Hash[0];
-- B = context->Intermediate_Hash[1];
-- C = context->Intermediate_Hash[2];
-- D = context->Intermediate_Hash[3];
-- E = context->Intermediate_Hash[4];
-- F = context->Intermediate_Hash[5];
-- G = context->Intermediate_Hash[6];
-- H = context->Intermediate_Hash[7];
--
-- for (t = 0; t < 80; t++) {
-- temp1 = H + SHA512_SIGMA1(E) + SHA_Ch(E,F,G) + K[t] + W[t];
-- temp2 = SHA512_SIGMA0(A) + SHA_Maj(A,B,C);
-- H = G;
-- G = F;
-- F = E;
-- E = D + temp1;
-- D = C;
-- C = B;
-- B = A;
-- A = temp1 + temp2;
-- }
--
-- context->Intermediate_Hash[0] += A;
-- context->Intermediate_Hash[1] += B;
-- context->Intermediate_Hash[2] += C;
-- context->Intermediate_Hash[3] += D;
-- context->Intermediate_Hash[4] += E;
-- context->Intermediate_Hash[5] += F;
-- context->Intermediate_Hash[6] += G;
-- context->Intermediate_Hash[7] += H;
--#endif /* USE_32BIT_ONLY */
--
-- context->Message_Block_Index = 0;
--}
--
--/*
-- * SHA384_512Reset
-- *
-- * Description:
-- * This helper function will initialize the SHA512Context in
-- * preparation for computing a new SHA384 or SHA512 message
--
--
--
--Eastlake 3rd & Hansen Informational [Page 64]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- * H0
-- * The initial hash value to use.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--#ifdef USE_32BIT_ONLY
--static int SHA384_512Reset(SHA512Context *context, uint32_t H0[])
--#else /* !USE_32BIT_ONLY */
--static int SHA384_512Reset(SHA512Context *context, uint64_t H0[])
--#endif /* USE_32BIT_ONLY */
--{
-- int i;
-- if (!context)
-- return shaNull;
--
-- context->Message_Block_Index = 0;
--
--#ifdef USE_32BIT_ONLY
-- context->Length[0] = context->Length[1] = 0;
-- context->Length[2] = context->Length[3] = 0;
--
-- for (i = 0; i < SHA512HashSize/4; i++)
-- context->Intermediate_Hash[i] = H0[i];
--#else /* !USE_32BIT_ONLY */
-- context->Length_High = context->Length_Low = 0;
--
-- for (i = 0; i < SHA512HashSize/8; i++)
-- context->Intermediate_Hash[i] = H0[i];
--#endif /* USE_32BIT_ONLY */
--
-- context->Computed = 0;
-- context->Corrupted = 0;
--
-- return shaSuccess;
--}
--
--/*
-- * SHA384_512ResultN
-- *
-- * Description:
-- * This helper function will return the 384-bit or 512-bit message
--
--
--
--Eastlake 3rd & Hansen Informational [Page 65]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * digest into the Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 48th/64th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- * HashSize: [in]
-- * The size of the hash, either 48 or 64.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--static int SHA384_512ResultN(SHA512Context *context,
-- uint8_t Message_Digest[], int HashSize)
--{
-- int i;
--
--#ifdef USE_32BIT_ONLY
-- int i2;
--#endif /* USE_32BIT_ONLY */
--
-- if (!context || !Message_Digest)
-- return shaNull;
--
-- if (context->Corrupted)
-- return context->Corrupted;
--
-- if (!context->Computed)
-- SHA384_512Finalize(context, 0x80);
--
--#ifdef USE_32BIT_ONLY
-- for (i = i2 = 0; i < HashSize; ) {
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>24);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>16);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>8);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2++]);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>24);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>16);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2]>>8);
-- Message_Digest[i++]=(uint8_t)(context->Intermediate_Hash[i2++]);
-- }
--#else /* !USE_32BIT_ONLY */
-- for (i = 0; i < HashSize; ++i)
-- Message_Digest[i] = (uint8_t)
--
--
--
--Eastlake 3rd & Hansen Informational [Page 66]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- (context->Intermediate_Hash[i>>3] >> 8 * ( 7 - ( i % 8 ) ));
--#endif /* USE_32BIT_ONLY */
--
-- return shaSuccess;
--}
--
--8.2.4. usha.c
--
--/**************************** usha.c ****************************/
--/******************** See RFC 4634 for details ******************/
--/*
-- * Description:
-- * This file implements a unified interface to the SHA algorithms.
-- */
--
--#include "sha.h"
--
--/*
-- * USHAReset
-- *
-- * Description:
-- * This function will initialize the SHA Context in preparation
-- * for computing a new SHA message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- * whichSha: [in]
-- * Selects which SHA reset to call
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int USHAReset(USHAContext *ctx, enum SHAversion whichSha)
--{
-- if (ctx) {
-- ctx->whichSha = whichSha;
-- switch (whichSha) {
-- case SHA1: return SHA1Reset((SHA1Context*)&ctx->ctx);
-- case SHA224: return SHA224Reset((SHA224Context*)&ctx->ctx);
-- case SHA256: return SHA256Reset((SHA256Context*)&ctx->ctx);
-- case SHA384: return SHA384Reset((SHA384Context*)&ctx->ctx);
-- case SHA512: return SHA512Reset((SHA512Context*)&ctx->ctx);
-- default: return shaBadParam;
-- }
-- } else {
-- return shaNull;
--
--
--
--Eastlake 3rd & Hansen Informational [Page 67]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- }
--}
--
--/*
-- * USHAInput
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int USHAInput(USHAContext *ctx,
-- const uint8_t *bytes, unsigned int bytecount)
--{
-- if (ctx) {
-- switch (ctx->whichSha) {
-- case SHA1:
-- return SHA1Input((SHA1Context*)&ctx->ctx, bytes, bytecount);
-- case SHA224:
-- return SHA224Input((SHA224Context*)&ctx->ctx, bytes,
-- bytecount);
-- case SHA256:
-- return SHA256Input((SHA256Context*)&ctx->ctx, bytes,
-- bytecount);
-- case SHA384:
-- return SHA384Input((SHA384Context*)&ctx->ctx, bytes,
-- bytecount);
-- case SHA512:
-- return SHA512Input((SHA512Context*)&ctx->ctx, bytes,
-- bytecount);
-- default: return shaBadParam;
-- }
-- } else {
-- return shaNull;
-- }
--}
--
--
--
--Eastlake 3rd & Hansen Informational [Page 68]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * USHAFinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The SHA context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int USHAFinalBits(USHAContext *ctx,
-- const uint8_t bits, unsigned int bitcount)
--{
-- if (ctx) {
-- switch (ctx->whichSha) {
-- case SHA1:
-- return SHA1FinalBits((SHA1Context*)&ctx->ctx, bits, bitcount);
-- case SHA224:
-- return SHA224FinalBits((SHA224Context*)&ctx->ctx, bits,
-- bitcount);
-- case SHA256:
-- return SHA256FinalBits((SHA256Context*)&ctx->ctx, bits,
-- bitcount);
-- case SHA384:
-- return SHA384FinalBits((SHA384Context*)&ctx->ctx, bits,
-- bitcount);
-- case SHA512:
-- return SHA512FinalBits((SHA512Context*)&ctx->ctx, bits,
-- bitcount);
-- default: return shaBadParam;
-- }
-- } else {
-- return shaNull;
-- }
--}
--
--/*
-- * USHAResult
-- *
--
--
--
--Eastlake 3rd & Hansen Informational [Page 69]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Description:
-- * This function will return the 160-bit message digest into the
-- * Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the 19th element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the SHA-1 hash.
-- * Message_Digest: [out]
-- * Where the digest is returned.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int USHAResult(USHAContext *ctx,
-- uint8_t Message_Digest[USHAMaxHashSize])
--{
-- if (ctx) {
-- switch (ctx->whichSha) {
-- case SHA1:
-- return SHA1Result((SHA1Context*)&ctx->ctx, Message_Digest);
-- case SHA224:
-- return SHA224Result((SHA224Context*)&ctx->ctx, Message_Digest);
-- case SHA256:
-- return SHA256Result((SHA256Context*)&ctx->ctx, Message_Digest);
-- case SHA384:
-- return SHA384Result((SHA384Context*)&ctx->ctx, Message_Digest);
-- case SHA512:
-- return SHA512Result((SHA512Context*)&ctx->ctx, Message_Digest);
-- default: return shaBadParam;
-- }
-- } else {
-- return shaNull;
-- }
--}
--
--/*
-- * USHABlockSize
-- *
-- * Description:
-- * This function will return the blocksize for the given SHA
-- * algorithm.
-- *
-- * Parameters:
-- * whichSha:
-- * which SHA algorithm to query
--
--
--
--Eastlake 3rd & Hansen Informational [Page 70]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- * Returns:
-- * block size
-- *
-- */
--int USHABlockSize(enum SHAversion whichSha)
--{
-- switch (whichSha) {
-- case SHA1: return SHA1_Message_Block_Size;
-- case SHA224: return SHA224_Message_Block_Size;
-- case SHA256: return SHA256_Message_Block_Size;
-- case SHA384: return SHA384_Message_Block_Size;
-- default:
-- case SHA512: return SHA512_Message_Block_Size;
-- }
--}
--
--/*
-- * USHAHashSize
-- *
-- * Description:
-- * This function will return the hashsize for the given SHA
-- * algorithm.
-- *
-- * Parameters:
-- * whichSha:
-- * which SHA algorithm to query
-- *
-- * Returns:
-- * hash size
-- *
-- */
--int USHAHashSize(enum SHAversion whichSha)
--{
-- switch (whichSha) {
-- case SHA1: return SHA1HashSize;
-- case SHA224: return SHA224HashSize;
-- case SHA256: return SHA256HashSize;
-- case SHA384: return SHA384HashSize;
-- default:
-- case SHA512: return SHA512HashSize;
-- }
--}
--
--/*
-- * USHAHashSizeBits
-- *
-- * Description:
--
--
--
--Eastlake 3rd & Hansen Informational [Page 71]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * This function will return the hashsize for the given SHA
-- * algorithm, expressed in bits.
-- *
-- * Parameters:
-- * whichSha:
-- * which SHA algorithm to query
-- *
-- * Returns:
-- * hash size in bits
-- *
-- */
--int USHAHashSizeBits(enum SHAversion whichSha)
--{
-- switch (whichSha) {
-- case SHA1: return SHA1HashSizeBits;
-- case SHA224: return SHA224HashSizeBits;
-- case SHA256: return SHA256HashSizeBits;
-- case SHA384: return SHA384HashSizeBits;
-- default:
-- case SHA512: return SHA512HashSizeBits;
-- }
--}
--
--8.2.5. sha-private.h
--
--/*************************** sha-private.h ***************************/
--/********************** See RFC 4634 for details *********************/
--#ifndef _SHA_PRIVATE__H
--#define _SHA_PRIVATE__H
--/*
-- * These definitions are defined in FIPS-180-2, section 4.1.
-- * Ch() and Maj() are defined identically in sections 4.1.1,
-- * 4.1.2 and 4.1.3.
-- *
-- * The definitions used in FIPS-180-2 are as follows:
-- */
--
--#ifndef USE_MODIFIED_MACROS
--#define SHA_Ch(x,y,z) (((x) & (y)) ^ ((~(x)) & (z)))
--#define SHA_Maj(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
--
--#else /* USE_MODIFIED_MACROS */
--/*
-- * The following definitions are equivalent and potentially faster.
-- */
--
--#define SHA_Ch(x, y, z) (((x) & ((y) ^ (z))) ^ (z))
--#define SHA_Maj(x, y, z) (((x) & ((y) | (z))) | ((y) & (z)))
--
--
--
--Eastlake 3rd & Hansen Informational [Page 72]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--#endif /* USE_MODIFIED_MACROS */
--
--#define SHA_Parity(x, y, z) ((x) ^ (y) ^ (z))
--
--#endif /* _SHA_PRIVATE__H */
--
--8.3 The HMAC Code
--
--/**************************** hmac.c ****************************/
--/******************** See RFC 4634 for details ******************/
--/*
-- * Description:
-- * This file implements the HMAC algorithm (Keyed-Hashing for
-- * Message Authentication, RFC2104), expressed in terms of the
-- * various SHA algorithms.
-- */
--
--#include "sha.h"
--
--/*
-- * hmac
-- *
-- * Description:
-- * This function will compute an HMAC message digest.
-- *
-- * Parameters:
-- * whichSha: [in]
-- * One of SHA1, SHA224, SHA256, SHA384, SHA512
-- * key: [in]
-- * The secret shared key.
-- * key_len: [in]
-- * The length of the secret shared key.
-- * message_array: [in]
-- * An array of characters representing the message.
-- * length: [in]
-- * The length of the message in message_array
-- * digest: [out]
-- * Where the digest is returned.
-- * NOTE: The length of the digest is determined by
-- * the value of whichSha.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int hmac(SHAversion whichSha, const unsigned char *text, int text_len,
-- const unsigned char *key, int key_len,
-- uint8_t digest[USHAMaxHashSize])
--
--
--
--Eastlake 3rd & Hansen Informational [Page 73]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--{
-- HMACContext ctx;
-- return hmacReset(&ctx, whichSha, key, key_len) ||
-- hmacInput(&ctx, text, text_len) ||
-- hmacResult(&ctx, digest);
--}
--
--/*
-- * hmacReset
-- *
-- * Description:
-- * This function will initialize the hmacContext in preparation
-- * for computing a new HMAC message digest.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to reset.
-- * whichSha: [in]
-- * One of SHA1, SHA224, SHA256, SHA384, SHA512
-- * key: [in]
-- * The secret shared key.
-- * key_len: [in]
-- * The length of the secret shared key.
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int hmacReset(HMACContext *ctx, enum SHAversion whichSha,
-- const unsigned char *key, int key_len)
--{
-- int i, blocksize, hashsize;
--
-- /* inner padding - key XORd with ipad */
-- unsigned char k_ipad[USHA_Max_Message_Block_Size];
--
-- /* temporary buffer when keylen > blocksize */
-- unsigned char tempkey[USHAMaxHashSize];
--
-- if (!ctx) return shaNull;
--
-- blocksize = ctx->blockSize = USHABlockSize(whichSha);
-- hashsize = ctx->hashSize = USHAHashSize(whichSha);
--
-- ctx->whichSha = whichSha;
--
-- /*
-- * If key is longer than the hash blocksize,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 74]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * reset it to key = HASH(key).
-- */
-- if (key_len > blocksize) {
-- USHAContext tctx;
-- int err = USHAReset(&tctx, whichSha) ||
-- USHAInput(&tctx, key, key_len) ||
-- USHAResult(&tctx, tempkey);
-- if (err != shaSuccess) return err;
--
-- key = tempkey;
-- key_len = hashsize;
-- }
--
-- /*
-- * The HMAC transform looks like:
-- *
-- * SHA(K XOR opad, SHA(K XOR ipad, text))
-- *
-- * where K is an n byte key.
-- * ipad is the byte 0x36 repeated blocksize times
-- * opad is the byte 0x5c repeated blocksize times
-- * and text is the data being protected.
-- */
--
-- /* store key into the pads, XOR'd with ipad and opad values */
-- for (i = 0; i < key_len; i++) {
-- k_ipad[i] = key[i] ^ 0x36;
-- ctx->k_opad[i] = key[i] ^ 0x5c;
-- }
-- /* remaining pad bytes are '\0' XOR'd with ipad and opad values */
-- for ( ; i < blocksize; i++) {
-- k_ipad[i] = 0x36;
-- ctx->k_opad[i] = 0x5c;
-- }
--
-- /* perform inner hash */
-- /* init context for 1st pass */
-- return USHAReset(&ctx->shaContext, whichSha) ||
-- /* and start with inner pad */
-- USHAInput(&ctx->shaContext, k_ipad, blocksize);
--}
--
--/*
-- * hmacInput
-- *
-- * Description:
-- * This function accepts an array of octets as the next portion
-- * of the message.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 75]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- * Parameters:
-- * context: [in/out]
-- * The HMAC context to update
-- * message_array: [in]
-- * An array of characters representing the next portion of
-- * the message.
-- * length: [in]
-- * The length of the message in message_array
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int hmacInput(HMACContext *ctx, const unsigned char *text,
-- int text_len)
--{
-- if (!ctx) return shaNull;
-- /* then text of datagram */
-- return USHAInput(&ctx->shaContext, text, text_len);
--}
--
--/*
-- * HMACFinalBits
-- *
-- * Description:
-- * This function will add in any final bits of the message.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The HMAC context to update
-- * message_bits: [in]
-- * The final bits of the message, in the upper portion of the
-- * byte. (Use 0b###00000 instead of 0b00000### to input the
-- * three bits ###.)
-- * length: [in]
-- * The number of bits in message_bits, between 1 and 7.
-- *
-- * Returns:
-- * sha Error Code.
-- */
--int hmacFinalBits(HMACContext *ctx,
-- const uint8_t bits,
-- unsigned int bitcount)
--{
-- if (!ctx) return shaNull;
-- /* then final bits of datagram */
-- return USHAFinalBits(&ctx->shaContext, bits, bitcount);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 76]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--}
--
--/*
-- * HMACResult
-- *
-- * Description:
-- * This function will return the N-byte message digest into the
-- * Message_Digest array provided by the caller.
-- * NOTE: The first octet of hash is stored in the 0th element,
-- * the last octet of hash in the Nth element.
-- *
-- * Parameters:
-- * context: [in/out]
-- * The context to use to calculate the HMAC hash.
-- * digest: [out]
-- * Where the digest is returned.
-- * NOTE 2: The length of the hash is determined by the value of
-- * whichSha that was passed to hmacReset().
-- *
-- * Returns:
-- * sha Error Code.
-- *
-- */
--int hmacResult(HMACContext *ctx, uint8_t *digest)
--{
-- if (!ctx) return shaNull;
--
-- /* finish up 1st pass */
-- /* (Use digest here as a temporary buffer.) */
-- return USHAResult(&ctx->shaContext, digest) ||
--
-- /* perform outer SHA */
-- /* init context for 2nd pass */
-- USHAReset(&ctx->shaContext, ctx->whichSha) ||
--
-- /* start with outer pad */
-- USHAInput(&ctx->shaContext, ctx->k_opad, ctx->blockSize) ||
--
-- /* then results of 1st hash */
-- USHAInput(&ctx->shaContext, digest, ctx->hashSize) ||
--
-- /* finish up 2nd pass */
-- USHAResult(&ctx->shaContext, digest);
--}
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 77]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--8.4. The Test Driver
--
-- The following code is a main program test driver to exercise the code
-- in sha1.c, sha224-256.c, and sha384-512.c. The test driver can also
-- be used as a stand-alone program for generating the hashes.
--
-- See also [RFC2202], [RFC4231], and [SHAVS].
--
--/**************************** shatest.c ****************************/
--/********************* See RFC 4634 for details ********************/
--/*
-- * Description:
-- * This file will exercise the SHA code performing
-- * the three tests documented in FIPS PUB 180-2
-- * (http://csrc.nist.gov/publications/fips/
-- * fips180-2/fips180-2withchangenotice.pdf)
-- * one that calls SHAInput with an exact multiple of 512 bits
-- * the seven tests documented for each algorithm in
-- * "The Secure Hash Algorithm Validation System (SHAVS)",
-- * three of which are bit-level tests
-- * (http://csrc.nist.gov/cryptval/shs/SHAVS.pdf)
-- *
-- * This file will exercise the HMAC SHA1 code performing
-- * the seven tests documented in RFCs 2202 and 4231.
-- *
-- * To run the tests and just see PASSED/FAILED, use the -p option.
-- *
-- * Other options exercise:
-- * hashing an arbitrary string
-- * hashing a file's contents
-- * a few error test checks
-- * printing the results in raw format
-- *
-- * Portability Issues:
-- * None.
-- *
-- */
--
--#include <stdint.h>
--#include <stdio.h>
--#include <stdlib.h>
--#include <string.h>
--#include <ctype.h>
--#include "sha.h"
--
--static int xgetopt(int argc, char **argv, const char *optstring);
--extern char *xoptarg;
--static int scasecmp(const char *s1, const char *s2);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 78]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * Define patterns for testing
-- */
--#define TEST1 "abc"
--#define TEST2_1 \
-- "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
--#define TEST2_2a \
-- "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmn"
--#define TEST2_2b \
-- "hijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
--#define TEST2_2 TEST2_2a TEST2_2b
--#define TEST3 "a" /* times 1000000 */
--#define TEST4a "01234567012345670123456701234567"
--#define TEST4b "01234567012345670123456701234567"
-- /* an exact multiple of 512 bits */
--#define TEST4 TEST4a TEST4b /* times 10 */
--
--#define TEST7_1 \
-- "\x49\xb2\xae\xc2\x59\x4b\xbe\x3a\x3b\x11\x75\x42\xd9\x4a\xc8"
--#define TEST8_1 \
-- "\x9a\x7d\xfd\xf1\xec\xea\xd0\x6e\xd6\x46\xaa\x55\xfe\x75\x71\x46"
--#define TEST9_1 \
-- "\x65\xf9\x32\x99\x5b\xa4\xce\x2c\xb1\xb4\xa2\xe7\x1a\xe7\x02\x20" \
-- "\xaa\xce\xc8\x96\x2d\xd4\x49\x9c\xbd\x7c\x88\x7a\x94\xea\xaa\x10" \
-- "\x1e\xa5\xaa\xbc\x52\x9b\x4e\x7e\x43\x66\x5a\x5a\xf2\xcd\x03\xfe" \
-- "\x67\x8e\xa6\xa5\x00\x5b\xba\x3b\x08\x22\x04\xc2\x8b\x91\x09\xf4" \
-- "\x69\xda\xc9\x2a\xaa\xb3\xaa\x7c\x11\xa1\xb3\x2a"
--#define TEST10_1 \
-- "\xf7\x8f\x92\x14\x1b\xcd\x17\x0a\xe8\x9b\x4f\xba\x15\xa1\xd5\x9f" \
-- "\x3f\xd8\x4d\x22\x3c\x92\x51\xbd\xac\xbb\xae\x61\xd0\x5e\xd1\x15" \
-- "\xa0\x6a\x7c\xe1\x17\xb7\xbe\xea\xd2\x44\x21\xde\xd9\xc3\x25\x92" \
-- "\xbd\x57\xed\xea\xe3\x9c\x39\xfa\x1f\xe8\x94\x6a\x84\xd0\xcf\x1f" \
-- "\x7b\xee\xad\x17\x13\xe2\xe0\x95\x98\x97\x34\x7f\x67\xc8\x0b\x04" \
-- "\x00\xc2\x09\x81\x5d\x6b\x10\xa6\x83\x83\x6f\xd5\x56\x2a\x56\xca" \
-- "\xb1\xa2\x8e\x81\xb6\x57\x66\x54\x63\x1c\xf1\x65\x66\xb8\x6e\x3b" \
-- "\x33\xa1\x08\xb0\x53\x07\xc0\x0a\xff\x14\xa7\x68\xed\x73\x50\x60" \
-- "\x6a\x0f\x85\xe6\xa9\x1d\x39\x6f\x5b\x5c\xbe\x57\x7f\x9b\x38\x80" \
-- "\x7c\x7d\x52\x3d\x6d\x79\x2f\x6e\xbc\x24\xa4\xec\xf2\xb3\xa4\x27" \
-- "\xcd\xbb\xfb"
--#define TEST7_224 \
-- "\xf0\x70\x06\xf2\x5a\x0b\xea\x68\xcd\x76\xa2\x95\x87\xc2\x8d"
--#define TEST8_224 \
-- "\x18\x80\x40\x05\xdd\x4f\xbd\x15\x56\x29\x9d\x6f\x9d\x93\xdf\x62"
--#define TEST9_224 \
-- "\xa2\xbe\x6e\x46\x32\x81\x09\x02\x94\xd9\xce\x94\x82\x65\x69\x42" \
-- "\x3a\x3a\x30\x5e\xd5\xe2\x11\x6c\xd4\xa4\xc9\x87\xfc\x06\x57\x00" \
-- "\x64\x91\xb1\x49\xcc\xd4\xb5\x11\x30\xac\x62\xb1\x9d\xc2\x48\xc7" \
-- "\x44\x54\x3d\x20\xcd\x39\x52\xdc\xed\x1f\x06\xcc\x3b\x18\xb9\x1f" \
--
--
--
--Eastlake 3rd & Hansen Informational [Page 79]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "\x3f\x55\x63\x3e\xcc\x30\x85\xf4\x90\x70\x60\xd2"
--#define TEST10_224 \
-- "\x55\xb2\x10\x07\x9c\x61\xb5\x3a\xdd\x52\x06\x22\xd1\xac\x97\xd5" \
-- "\xcd\xbe\x8c\xb3\x3a\xa0\xae\x34\x45\x17\xbe\xe4\xd7\xba\x09\xab" \
-- "\xc8\x53\x3c\x52\x50\x88\x7a\x43\xbe\xbb\xac\x90\x6c\x2e\x18\x37" \
-- "\xf2\x6b\x36\xa5\x9a\xe3\xbe\x78\x14\xd5\x06\x89\x6b\x71\x8b\x2a" \
-- "\x38\x3e\xcd\xac\x16\xb9\x61\x25\x55\x3f\x41\x6f\xf3\x2c\x66\x74" \
-- "\xc7\x45\x99\xa9\x00\x53\x86\xd9\xce\x11\x12\x24\x5f\x48\xee\x47" \
-- "\x0d\x39\x6c\x1e\xd6\x3b\x92\x67\x0c\xa5\x6e\xc8\x4d\xee\xa8\x14" \
-- "\xb6\x13\x5e\xca\x54\x39\x2b\xde\xdb\x94\x89\xbc\x9b\x87\x5a\x8b" \
-- "\xaf\x0d\xc1\xae\x78\x57\x36\x91\x4a\xb7\xda\xa2\x64\xbc\x07\x9d" \
-- "\x26\x9f\x2c\x0d\x7e\xdd\xd8\x10\xa4\x26\x14\x5a\x07\x76\xf6\x7c" \
-- "\x87\x82\x73"
--#define TEST7_256 \
-- "\xbe\x27\x46\xc6\xdb\x52\x76\x5f\xdb\x2f\x88\x70\x0f\x9a\x73"
--#define TEST8_256 \
-- "\xe3\xd7\x25\x70\xdc\xdd\x78\x7c\xe3\x88\x7a\xb2\xcd\x68\x46\x52"
--#define TEST9_256 \
-- "\x3e\x74\x03\x71\xc8\x10\xc2\xb9\x9f\xc0\x4e\x80\x49\x07\xef\x7c" \
-- "\xf2\x6b\xe2\x8b\x57\xcb\x58\xa3\xe2\xf3\xc0\x07\x16\x6e\x49\xc1" \
-- "\x2e\x9b\xa3\x4c\x01\x04\x06\x91\x29\xea\x76\x15\x64\x25\x45\x70" \
-- "\x3a\x2b\xd9\x01\xe1\x6e\xb0\xe0\x5d\xeb\xa0\x14\xeb\xff\x64\x06" \
-- "\xa0\x7d\x54\x36\x4e\xff\x74\x2d\xa7\x79\xb0\xb3"
--#define TEST10_256 \
-- "\x83\x26\x75\x4e\x22\x77\x37\x2f\x4f\xc1\x2b\x20\x52\x7a\xfe\xf0" \
-- "\x4d\x8a\x05\x69\x71\xb1\x1a\xd5\x71\x23\xa7\xc1\x37\x76\x00\x00" \
-- "\xd7\xbe\xf6\xf3\xc1\xf7\xa9\x08\x3a\xa3\x9d\x81\x0d\xb3\x10\x77" \
-- "\x7d\xab\x8b\x1e\x7f\x02\xb8\x4a\x26\xc7\x73\x32\x5f\x8b\x23\x74" \
-- "\xde\x7a\x4b\x5a\x58\xcb\x5c\x5c\xf3\x5b\xce\xe6\xfb\x94\x6e\x5b" \
-- "\xd6\x94\xfa\x59\x3a\x8b\xeb\x3f\x9d\x65\x92\xec\xed\xaa\x66\xca" \
-- "\x82\xa2\x9d\x0c\x51\xbc\xf9\x33\x62\x30\xe5\xd7\x84\xe4\xc0\xa4" \
-- "\x3f\x8d\x79\xa3\x0a\x16\x5c\xba\xbe\x45\x2b\x77\x4b\x9c\x71\x09" \
-- "\xa9\x7d\x13\x8f\x12\x92\x28\x96\x6f\x6c\x0a\xdc\x10\x6a\xad\x5a" \
-- "\x9f\xdd\x30\x82\x57\x69\xb2\xc6\x71\xaf\x67\x59\xdf\x28\xeb\x39" \
-- "\x3d\x54\xd6"
--#define TEST7_384 \
-- "\x8b\xc5\x00\xc7\x7c\xee\xd9\x87\x9d\xa9\x89\x10\x7c\xe0\xaa"
--#define TEST8_384 \
-- "\xa4\x1c\x49\x77\x79\xc0\x37\x5f\xf1\x0a\x7f\x4e\x08\x59\x17\x39"
--#define TEST9_384 \
-- "\x68\xf5\x01\x79\x2d\xea\x97\x96\x76\x70\x22\xd9\x3d\xa7\x16\x79" \
-- "\x30\x99\x20\xfa\x10\x12\xae\xa3\x57\xb2\xb1\x33\x1d\x40\xa1\xd0" \
-- "\x3c\x41\xc2\x40\xb3\xc9\xa7\x5b\x48\x92\xf4\xc0\x72\x4b\x68\xc8" \
-- "\x75\x32\x1a\xb8\xcf\xe5\x02\x3b\xd3\x75\xbc\x0f\x94\xbd\x89\xfe" \
-- "\x04\xf2\x97\x10\x5d\x7b\x82\xff\xc0\x02\x1a\xeb\x1c\xcb\x67\x4f" \
-- "\x52\x44\xea\x34\x97\xde\x26\xa4\x19\x1c\x5f\x62\xe5\xe9\xa2\xd8" \
-- "\x08\x2f\x05\x51\xf4\xa5\x30\x68\x26\xe9\x1c\xc0\x06\xce\x1b\xf6" \
-- "\x0f\xf7\x19\xd4\x2f\xa5\x21\xc8\x71\xcd\x23\x94\xd9\x6e\xf4\x46" \
--
--
--
--Eastlake 3rd & Hansen Informational [Page 80]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "\x8f\x21\x96\x6b\x41\xf2\xba\x80\xc2\x6e\x83\xa9"
--#define TEST10_384 \
-- "\x39\x96\x69\xe2\x8f\x6b\x9c\x6d\xbc\xbb\x69\x12\xec\x10\xff\xcf" \
-- "\x74\x79\x03\x49\xb7\xdc\x8f\xbe\x4a\x8e\x7b\x3b\x56\x21\xdb\x0f" \
-- "\x3e\x7d\xc8\x7f\x82\x32\x64\xbb\xe4\x0d\x18\x11\xc9\xea\x20\x61" \
-- "\xe1\xc8\x4a\xd1\x0a\x23\xfa\xc1\x72\x7e\x72\x02\xfc\x3f\x50\x42" \
-- "\xe6\xbf\x58\xcb\xa8\xa2\x74\x6e\x1f\x64\xf9\xb9\xea\x35\x2c\x71" \
-- "\x15\x07\x05\x3c\xf4\xe5\x33\x9d\x52\x86\x5f\x25\xcc\x22\xb5\xe8" \
-- "\x77\x84\xa1\x2f\xc9\x61\xd6\x6c\xb6\xe8\x95\x73\x19\x9a\x2c\xe6" \
-- "\x56\x5c\xbd\xf1\x3d\xca\x40\x38\x32\xcf\xcb\x0e\x8b\x72\x11\xe8" \
-- "\x3a\xf3\x2a\x11\xac\x17\x92\x9f\xf1\xc0\x73\xa5\x1c\xc0\x27\xaa" \
-- "\xed\xef\xf8\x5a\xad\x7c\x2b\x7c\x5a\x80\x3e\x24\x04\xd9\x6d\x2a" \
-- "\x77\x35\x7b\xda\x1a\x6d\xae\xed\x17\x15\x1c\xb9\xbc\x51\x25\xa4" \
-- "\x22\xe9\x41\xde\x0c\xa0\xfc\x50\x11\xc2\x3e\xcf\xfe\xfd\xd0\x96" \
-- "\x76\x71\x1c\xf3\xdb\x0a\x34\x40\x72\x0e\x16\x15\xc1\xf2\x2f\xbc" \
-- "\x3c\x72\x1d\xe5\x21\xe1\xb9\x9b\xa1\xbd\x55\x77\x40\x86\x42\x14" \
-- "\x7e\xd0\x96"
--#define TEST7_512 \
-- "\x08\xec\xb5\x2e\xba\xe1\xf7\x42\x2d\xb6\x2b\xcd\x54\x26\x70"
--#define TEST8_512 \
-- "\x8d\x4e\x3c\x0e\x38\x89\x19\x14\x91\x81\x6e\x9d\x98\xbf\xf0\xa0"
--#define TEST9_512 \
-- "\x3a\xdd\xec\x85\x59\x32\x16\xd1\x61\x9a\xa0\x2d\x97\x56\x97\x0b" \
-- "\xfc\x70\xac\xe2\x74\x4f\x7c\x6b\x27\x88\x15\x10\x28\xf7\xb6\xa2" \
-- "\x55\x0f\xd7\x4a\x7e\x6e\x69\xc2\xc9\xb4\x5f\xc4\x54\x96\x6d\xc3" \
-- "\x1d\x2e\x10\xda\x1f\x95\xce\x02\xbe\xb4\xbf\x87\x65\x57\x4c\xbd" \
-- "\x6e\x83\x37\xef\x42\x0a\xdc\x98\xc1\x5c\xb6\xd5\xe4\xa0\x24\x1b" \
-- "\xa0\x04\x6d\x25\x0e\x51\x02\x31\xca\xc2\x04\x6c\x99\x16\x06\xab" \
-- "\x4e\xe4\x14\x5b\xee\x2f\xf4\xbb\x12\x3a\xab\x49\x8d\x9d\x44\x79" \
-- "\x4f\x99\xcc\xad\x89\xa9\xa1\x62\x12\x59\xed\xa7\x0a\x5b\x6d\xd4" \
-- "\xbd\xd8\x77\x78\xc9\x04\x3b\x93\x84\xf5\x49\x06"
--#define TEST10_512 \
-- "\xa5\x5f\x20\xc4\x11\xaa\xd1\x32\x80\x7a\x50\x2d\x65\x82\x4e\x31" \
-- "\xa2\x30\x54\x32\xaa\x3d\x06\xd3\xe2\x82\xa8\xd8\x4e\x0d\xe1\xde" \
-- "\x69\x74\xbf\x49\x54\x69\xfc\x7f\x33\x8f\x80\x54\xd5\x8c\x26\xc4" \
-- "\x93\x60\xc3\xe8\x7a\xf5\x65\x23\xac\xf6\xd8\x9d\x03\xe5\x6f\xf2" \
-- "\xf8\x68\x00\x2b\xc3\xe4\x31\xed\xc4\x4d\xf2\xf0\x22\x3d\x4b\xb3" \
-- "\xb2\x43\x58\x6e\x1a\x7d\x92\x49\x36\x69\x4f\xcb\xba\xf8\x8d\x95" \
-- "\x19\xe4\xeb\x50\xa6\x44\xf8\xe4\xf9\x5e\xb0\xea\x95\xbc\x44\x65" \
-- "\xc8\x82\x1a\xac\xd2\xfe\x15\xab\x49\x81\x16\x4b\xbb\x6d\xc3\x2f" \
-- "\x96\x90\x87\xa1\x45\xb0\xd9\xcc\x9c\x67\xc2\x2b\x76\x32\x99\x41" \
-- "\x9c\xc4\x12\x8b\xe9\xa0\x77\xb3\xac\xe6\x34\x06\x4e\x6d\x99\x28" \
-- "\x35\x13\xdc\x06\xe7\x51\x5d\x0d\x73\x13\x2e\x9a\x0d\xc6\xd3\xb1" \
-- "\xf8\xb2\x46\xf1\xa9\x8a\x3f\xc7\x29\x41\xb1\xe3\xbb\x20\x98\xe8" \
-- "\xbf\x16\xf2\x68\xd6\x4f\x0b\x0f\x47\x07\xfe\x1e\xa1\xa1\x79\x1b" \
-- "\xa2\xf3\xc0\xc7\x58\xe5\xf5\x51\x86\x3a\x96\xc9\x49\xad\x47\xd7" \
-- "\xfb\x40\xd2"
--#define SHA1_SEED "\xd0\x56\x9c\xb3\x66\x5a\x8a\x43\xeb\x6e\xa2\x3d" \
--
--
--
--Eastlake 3rd & Hansen Informational [Page 81]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "\x75\xa3\xc4\xd2\x05\x4a\x0d\x7d"
--#define SHA224_SEED "\xd0\x56\x9c\xb3\x66\x5a\x8a\x43\xeb\x6e\xa2" \
-- "\x3d\x75\xa3\xc4\xd2\x05\x4a\x0d\x7d\x66\xa9\xca\x99\xc9\xce\xb0" \
-- "\x27"
--#define SHA256_SEED "\xf4\x1e\xce\x26\x13\xe4\x57\x39\x15\x69\x6b" \
-- "\x5a\xdc\xd5\x1c\xa3\x28\xbe\x3b\xf5\x66\xa9\xca\x99\xc9\xce\xb0" \
-- "\x27\x9c\x1c\xb0\xa7"
--#define SHA384_SEED "\x82\x40\xbc\x51\xe4\xec\x7e\xf7\x6d\x18\xe3" \
-- "\x52\x04\xa1\x9f\x51\xa5\x21\x3a\x73\xa8\x1d\x6f\x94\x46\x80\xd3" \
-- "\x07\x59\x48\xb7\xe4\x63\x80\x4e\xa3\xd2\x6e\x13\xea\x82\x0d\x65" \
-- "\xa4\x84\xbe\x74\x53"
--#define SHA512_SEED "\x47\x3f\xf1\xb9\xb3\xff\xdf\xa1\x26\x69\x9a" \
-- "\xc7\xef\x9e\x8e\x78\x77\x73\x09\x58\x24\xc6\x42\x55\x7c\x13\x99" \
-- "\xd9\x8e\x42\x20\x44\x8d\xc3\x5b\x99\xbf\xdd\x44\x77\x95\x43\x92" \
-- "\x4c\x1c\xe9\x3b\xc5\x94\x15\x38\x89\x5d\xb9\x88\x26\x1b\x00\x77" \
-- "\x4b\x12\x27\x20\x39"
--
--#define TESTCOUNT 10
--#define HASHCOUNT 5
--#define RANDOMCOUNT 4
--#define HMACTESTCOUNT 7
--
--#define PRINTNONE 0
--#define PRINTTEXT 1
--#define PRINTRAW 2
--#define PRINTHEX 3
--#define PRINTBASE64 4
--
--#define PRINTPASSFAIL 1
--#define PRINTFAIL 2
--
--#define length(x) (sizeof(x)-1)
--
--/* Test arrays for hashes. */
--struct hash {
-- const char *name;
-- SHAversion whichSha;
-- int hashsize;
-- struct {
-- const char *testarray;
-- int length;
-- long repeatcount;
-- int extrabits;
-- int numberExtrabits;
-- const char *resultarray;
-- } tests[TESTCOUNT];
-- const char *randomtest;
-- const char *randomresults[RANDOMCOUNT];
--
--
--
--Eastlake 3rd & Hansen Informational [Page 82]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--} hashes[HASHCOUNT] = {
-- { "SHA1", SHA1, SHA1HashSize,
-- {
-- /* 1 */ { TEST1, length(TEST1), 1, 0, 0,
-- "A9993E364706816ABA3E25717850C26C9CD0D89D" },
-- /* 2 */ { TEST2_1, length(TEST2_1), 1, 0, 0,
-- "84983E441C3BD26EBAAE4AA1F95129E5E54670F1" },
-- /* 3 */ { TEST3, length(TEST3), 1000000, 0, 0,
-- "34AA973CD4C4DAA4F61EEB2BDBAD27316534016F" },
-- /* 4 */ { TEST4, length(TEST4), 10, 0, 0,
-- "DEA356A2CDDD90C7A7ECEDC5EBB563934F460452" },
-- /* 5 */ { "", 0, 0, 0x98, 5,
-- "29826B003B906E660EFF4027CE98AF3531AC75BA" },
-- /* 6 */ { "\x5e", 1, 1, 0, 0,
-- "5E6F80A34A9798CAFC6A5DB96CC57BA4C4DB59C2" },
-- /* 7 */ { TEST7_1, length(TEST7_1), 1, 0x80, 3,
-- "6239781E03729919C01955B3FFA8ACB60B988340" },
-- /* 8 */ { TEST8_1, length(TEST8_1), 1, 0, 0,
-- "82ABFF6605DBE1C17DEF12A394FA22A82B544A35" },
-- /* 9 */ { TEST9_1, length(TEST9_1), 1, 0xE0, 3,
-- "8C5B2A5DDAE5A97FC7F9D85661C672ADBF7933D4" },
-- /* 10 */ { TEST10_1, length(TEST10_1), 1, 0, 0,
-- "CB0082C8F197D260991BA6A460E76E202BAD27B3" }
-- }, SHA1_SEED, { "E216836819477C7F78E0D843FE4FF1B6D6C14CD4",
-- "A2DBC7A5B1C6C0A8BCB7AAA41252A6A7D0690DBC",
-- "DB1F9050BB863DFEF4CE37186044E2EEB17EE013",
-- "127FDEDF43D372A51D5747C48FBFFE38EF6CDF7B"
-- } },
-- { "SHA224", SHA224, SHA224HashSize,
-- {
-- /* 1 */ { TEST1, length(TEST1), 1, 0, 0,
-- "23097D223405D8228642A477BDA255B32AADBCE4BDA0B3F7E36C9DA7" },
-- /* 2 */ { TEST2_1, length(TEST2_1), 1, 0, 0,
-- "75388B16512776CC5DBA5DA1FD890150B0C6455CB4F58B1952522525" },
-- /* 3 */ { TEST3, length(TEST3), 1000000, 0, 0,
-- "20794655980C91D8BBB4C1EA97618A4BF03F42581948B2EE4EE7AD67" },
-- /* 4 */ { TEST4, length(TEST4), 10, 0, 0,
-- "567F69F168CD7844E65259CE658FE7AADFA25216E68ECA0EB7AB8262" },
-- /* 5 */ { "", 0, 0, 0x68, 5,
-- "E3B048552C3C387BCAB37F6EB06BB79B96A4AEE5FF27F51531A9551C" },
-- /* 6 */ { "\x07", 1, 1, 0, 0,
-- "00ECD5F138422B8AD74C9799FD826C531BAD2FCABC7450BEE2AA8C2A" },
-- /* 7 */ { TEST7_224, length(TEST7_224), 1, 0xA0, 3,
-- "1B01DB6CB4A9E43DED1516BEB3DB0B87B6D1EA43187462C608137150" },
-- /* 8 */ { TEST8_224, length(TEST8_224), 1, 0, 0,
-- "DF90D78AA78821C99B40BA4C966921ACCD8FFB1E98AC388E56191DB1" },
-- /* 9 */ { TEST9_224, length(TEST9_224), 1, 0xE0, 3,
-- "54BEA6EAB8195A2EB0A7906A4B4A876666300EEFBD1F3B8474F9CD57" },
--
--
--
--Eastlake 3rd & Hansen Informational [Page 83]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- /* 10 */ { TEST10_224, length(TEST10_224), 1, 0, 0,
-- "0B31894EC8937AD9B91BDFBCBA294D9ADEFAA18E09305E9F20D5C3A4" }
-- }, SHA224_SEED, { "100966A5B4FDE0B42E2A6C5953D4D7F41BA7CF79FD"
-- "2DF431416734BE", "1DCA396B0C417715DEFAAE9641E10A2E99D55A"
-- "BCB8A00061EB3BE8BD", "1864E627BDB2319973CD5ED7D68DA71D8B"
-- "F0F983D8D9AB32C34ADB34", "A2406481FC1BCAF24DD08E6752E844"
-- "709563FB916227FED598EB621F"
-- } },
-- { "SHA256", SHA256, SHA256HashSize,
-- {
-- /* 1 */ { TEST1, length(TEST1), 1, 0, 0, "BA7816BF8F01CFEA4141"
-- "40DE5DAE2223B00361A396177A9CB410FF61F20015AD" },
-- /* 2 */ { TEST2_1, length(TEST2_1), 1, 0, 0, "248D6A61D20638B8"
-- "E5C026930C3E6039A33CE45964FF2167F6ECEDD419DB06C1" },
-- /* 3 */ { TEST3, length(TEST3), 1000000, 0, 0, "CDC76E5C9914FB92"
-- "81A1C7E284D73E67F1809A48A497200E046D39CCC7112CD0" },
-- /* 4 */ { TEST4, length(TEST4), 10, 0, 0, "594847328451BDFA"
-- "85056225462CC1D867D877FB388DF0CE35F25AB5562BFBB5" },
-- /* 5 */ { "", 0, 0, 0x68, 5, "D6D3E02A31A84A8CAA9718ED6C2057BE"
-- "09DB45E7823EB5079CE7A573A3760F95" },
-- /* 6 */ { "\x19", 1, 1, 0, 0, "68AA2E2EE5DFF96E3355E6C7EE373E3D"
-- "6A4E17F75F9518D843709C0C9BC3E3D4" },
-- /* 7 */ { TEST7_256, length(TEST7_256), 1, 0x60, 3, "77EC1DC8"
-- "9C821FF2A1279089FA091B35B8CD960BCAF7DE01C6A7680756BEB972" },
-- /* 8 */ { TEST8_256, length(TEST8_256), 1, 0, 0, "175EE69B02BA"
-- "9B58E2B0A5FD13819CEA573F3940A94F825128CF4209BEABB4E8" },
-- /* 9 */ { TEST9_256, length(TEST9_256), 1, 0xA0, 3, "3E9AD646"
-- "8BBBAD2AC3C2CDC292E018BA5FD70B960CF1679777FCE708FDB066E9" },
-- /* 10 */ { TEST10_256, length(TEST10_256), 1, 0, 0, "97DBCA7D"
-- "F46D62C8A422C941DD7E835B8AD3361763F7E9B2D95F4F0DA6E1CCBC" },
-- }, SHA256_SEED, { "83D28614D49C3ADC1D6FC05DB5F48037C056F8D2A4CE44"
-- "EC6457DEA5DD797CD1", "99DBE3127EF2E93DD9322D6A07909EB33B6399"
-- "5E529B3F954B8581621BB74D39", "8D4BE295BB64661CA3C7EFD129A2F7"
-- "25B33072DBDDE32385B9A87B9AF88EA76F", "40AF5D3F9716B040DF9408"
-- "E31536B70FF906EC51B00447CA97D7DD97C12411F4"
-- } },
-- { "SHA384", SHA384, SHA384HashSize,
-- {
-- /* 1 */ { TEST1, length(TEST1), 1, 0, 0,
-- "CB00753F45A35E8BB5A03D699AC65007272C32AB0EDED163"
-- "1A8B605A43FF5BED8086072BA1E7CC2358BAECA134C825A7" },
-- /* 2 */ { TEST2_2, length(TEST2_2), 1, 0, 0,
-- "09330C33F71147E83D192FC782CD1B4753111B173B3B05D2"
-- "2FA08086E3B0F712FCC7C71A557E2DB966C3E9FA91746039" },
-- /* 3 */ { TEST3, length(TEST3), 1000000, 0, 0,
-- "9D0E1809716474CB086E834E310A4A1CED149E9C00F24852"
-- "7972CEC5704C2A5B07B8B3DC38ECC4EBAE97DDD87F3D8985" },
-- /* 4 */ { TEST4, length(TEST4), 10, 0, 0,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 84]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "2FC64A4F500DDB6828F6A3430B8DD72A368EB7F3A8322A70"
-- "BC84275B9C0B3AB00D27A5CC3C2D224AA6B61A0D79FB4596" },
-- /* 5 */ { "", 0, 0, 0x10, 5,
-- "8D17BE79E32B6718E07D8A603EB84BA0478F7FCFD1BB9399"
-- "5F7D1149E09143AC1FFCFC56820E469F3878D957A15A3FE4" },
-- /* 6 */ { "\xb9", 1, 1, 0, 0,
-- "BC8089A19007C0B14195F4ECC74094FEC64F01F90929282C"
-- "2FB392881578208AD466828B1C6C283D2722CF0AD1AB6938" },
-- /* 7 */ { TEST7_384, length(TEST7_384), 1, 0xA0, 3,
-- "D8C43B38E12E7C42A7C9B810299FD6A770BEF30920F17532"
-- "A898DE62C7A07E4293449C0B5FA70109F0783211CFC4BCE3" },
-- /* 8 */ { TEST8_384, length(TEST8_384), 1, 0, 0,
-- "C9A68443A005812256B8EC76B00516F0DBB74FAB26D66591"
-- "3F194B6FFB0E91EA9967566B58109CBC675CC208E4C823F7" },
-- /* 9 */ { TEST9_384, length(TEST9_384), 1, 0xE0, 3,
-- "5860E8DE91C21578BB4174D227898A98E0B45C4C760F0095"
-- "49495614DAEDC0775D92D11D9F8CE9B064EEAC8DAFC3A297" },
-- /* 10 */ { TEST10_384, length(TEST10_384), 1, 0, 0,
-- "4F440DB1E6EDD2899FA335F09515AA025EE177A79F4B4AAF"
-- "38E42B5C4DE660F5DE8FB2A5B2FBD2A3CBFFD20CFF1288C0" }
-- }, SHA384_SEED, { "CE44D7D63AE0C91482998CF662A51EC80BF6FC68661A3C"
-- "57F87566112BD635A743EA904DEB7D7A42AC808CABE697F38F", "F9C6D2"
-- "61881FEE41ACD39E67AA8D0BAD507C7363EB67E2B81F45759F9C0FD7B503"
-- "DF1A0B9E80BDE7BC333D75B804197D", "D96512D8C9F4A7A4967A366C01"
-- "C6FD97384225B58343A88264847C18E4EF8AB7AEE4765FFBC3E30BD485D3"
-- "638A01418F", "0CA76BD0813AF1509E170907A96005938BC985628290B2"
-- "5FEF73CF6FAD68DDBA0AC8920C94E0541607B0915A7B4457F7"
-- } },
-- { "SHA512", SHA512, SHA512HashSize,
-- {
-- /* 1 */ { TEST1, length(TEST1), 1, 0, 0,
-- "DDAF35A193617ABACC417349AE20413112E6FA4E89A97EA2"
-- "0A9EEEE64B55D39A2192992A274FC1A836BA3C23A3FEEBBD"
-- "454D4423643CE80E2A9AC94FA54CA49F" },
-- /* 2 */ { TEST2_2, length(TEST2_2), 1, 0, 0,
-- "8E959B75DAE313DA8CF4F72814FC143F8F7779C6EB9F7FA1"
-- "7299AEADB6889018501D289E4900F7E4331B99DEC4B5433A"
-- "C7D329EEB6DD26545E96E55B874BE909" },
-- /* 3 */ { TEST3, length(TEST3), 1000000, 0, 0,
-- "E718483D0CE769644E2E42C7BC15B4638E1F98B13B204428"
-- "5632A803AFA973EBDE0FF244877EA60A4CB0432CE577C31B"
-- "EB009C5C2C49AA2E4EADB217AD8CC09B" },
-- /* 4 */ { TEST4, length(TEST4), 10, 0, 0,
-- "89D05BA632C699C31231DED4FFC127D5A894DAD412C0E024"
-- "DB872D1ABD2BA8141A0F85072A9BE1E2AA04CF33C765CB51"
-- "0813A39CD5A84C4ACAA64D3F3FB7BAE9" },
-- /* 5 */ { "", 0, 0, 0xB0, 5,
-- "D4EE29A9E90985446B913CF1D1376C836F4BE2C1CF3CADA0"
--
--
--
--Eastlake 3rd & Hansen Informational [Page 85]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "720A6BF4857D886A7ECB3C4E4C0FA8C7F95214E41DC1B0D2"
-- "1B22A84CC03BF8CE4845F34DD5BDBAD4" },
-- /* 6 */ { "\xD0", 1, 1, 0, 0,
-- "9992202938E882E73E20F6B69E68A0A7149090423D93C81B"
-- "AB3F21678D4ACEEEE50E4E8CAFADA4C85A54EA8306826C4A"
-- "D6E74CECE9631BFA8A549B4AB3FBBA15" },
-- /* 7 */ { TEST7_512, length(TEST7_512), 1, 0x80, 3,
-- "ED8DC78E8B01B69750053DBB7A0A9EDA0FB9E9D292B1ED71"
-- "5E80A7FE290A4E16664FD913E85854400C5AF05E6DAD316B"
-- "7359B43E64F8BEC3C1F237119986BBB6" },
-- /* 8 */ { TEST8_512, length(TEST8_512), 1, 0, 0,
-- "CB0B67A4B8712CD73C9AABC0B199E9269B20844AFB75ACBD"
-- "D1C153C9828924C3DDEDAAFE669C5FDD0BC66F630F677398"
-- "8213EB1B16F517AD0DE4B2F0C95C90F8" },
-- /* 9 */ { TEST9_512, length(TEST9_512), 1, 0x80, 3,
-- "32BA76FC30EAA0208AEB50FFB5AF1864FDBF17902A4DC0A6"
-- "82C61FCEA6D92B783267B21080301837F59DE79C6B337DB2"
-- "526F8A0A510E5E53CAFED4355FE7C2F1" },
-- /* 10 */ { TEST10_512, length(TEST10_512), 1, 0, 0,
-- "C665BEFB36DA189D78822D10528CBF3B12B3EEF726039909"
-- "C1A16A270D48719377966B957A878E720584779A62825C18"
-- "DA26415E49A7176A894E7510FD1451F5" }
-- }, SHA512_SEED, { "2FBB1E7E00F746BA514FBC8C421F36792EC0E11FF5EFC3"
-- "78E1AB0C079AA5F0F66A1E3EDBAEB4F9984BE14437123038A452004A5576"
-- "8C1FD8EED49E4A21BEDCD0", "25CBE5A4F2C7B1D7EF07011705D50C62C5"
-- "000594243EAFD1241FC9F3D22B58184AE2FEE38E171CF8129E29459C9BC2"
-- "EF461AF5708887315F15419D8D17FE7949", "5B8B1F2687555CE2D7182B"
-- "92E5C3F6C36547DA1C13DBB9EA4F73EA4CBBAF89411527906D35B1B06C1B"
-- "6A8007D05EC66DF0A406066829EAB618BDE3976515AAFC", "46E36B007D"
-- "19876CDB0B29AD074FE3C08CDD174D42169D6ABE5A1414B6E79707DF5877"
-- "6A98091CF431854147BB6D3C66D43BFBC108FD715BDE6AA127C2B0E79F"
-- }
-- }
--};
--
--/* Test arrays for HMAC. */
--struct hmachash {
-- const char *keyarray[5];
-- int keylength[5];
-- const char *dataarray[5];
-- int datalength[5];
-- const char *resultarray[5];
-- int resultlength[5];
--} hmachashes[HMACTESTCOUNT] = {
-- { /* 1 */ {
-- "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
-- "\x0b\x0b\x0b\x0b\x0b"
-- }, { 20 }, {
--
--
--
--Eastlake 3rd & Hansen Informational [Page 86]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "\x48\x69\x20\x54\x68\x65\x72\x65" /* "Hi There" */
-- }, { 8 }, {
-- /* HMAC-SHA-1 */
-- "B617318655057264E28BC0B6FB378C8EF146BE00",
-- /* HMAC-SHA-224 */
-- "896FB1128ABBDF196832107CD49DF33F47B4B1169912BA4F53684B22",
-- /* HMAC-SHA-256 */
-- "B0344C61D8DB38535CA8AFCEAF0BF12B881DC200C9833DA726E9376C2E32"
-- "CFF7",
-- /* HMAC-SHA-384 */
-- "AFD03944D84895626B0825F4AB46907F15F9DADBE4101EC682AA034C7CEB"
-- "C59CFAEA9EA9076EDE7F4AF152E8B2FA9CB6",
-- /* HMAC-SHA-512 */
-- "87AA7CDEA5EF619D4FF0B4241A1D6CB02379F4E2CE4EC2787AD0B30545E1"
-- "7CDEDAA833B7D6B8A702038B274EAEA3F4E4BE9D914EEB61F1702E696C20"
-- "3A126854"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- },
-- { /* 2 */ {
-- "\x4a\x65\x66\x65" /* "Jefe" */
-- }, { 4 }, {
-- "\x77\x68\x61\x74\x20\x64\x6f\x20\x79\x61\x20\x77\x61\x6e\x74"
-- "\x20\x66\x6f\x72\x20\x6e\x6f\x74\x68\x69\x6e\x67\x3f"
-- /* "what do ya want for nothing?" */
-- }, { 28 }, {
-- /* HMAC-SHA-1 */
-- "EFFCDF6AE5EB2FA2D27416D5F184DF9C259A7C79",
-- /* HMAC-SHA-224 */
-- "A30E01098BC6DBBF45690F3A7E9E6D0F8BBEA2A39E6148008FD05E44",
-- /* HMAC-SHA-256 */
-- "5BDCC146BF60754E6A042426089575C75A003F089D2739839DEC58B964EC"
-- "3843",
-- /* HMAC-SHA-384 */
-- "AF45D2E376484031617F78D2B58A6B1B9C7EF464F5A01B47E42EC3736322"
-- "445E8E2240CA5E69E2C78B3239ECFAB21649",
-- /* HMAC-SHA-512 */
-- "164B7A7BFCF819E2E395FBE73B56E0A387BD64222E831FD610270CD7EA25"
-- "05549758BF75C05A994A6D034F65F8F0E6FDCAEAB1A34D4A6B4B636E070A"
-- "38BCE737"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- },
-- { /* 3 */
-- {
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa"
-- }, { 20 }, {
--
--
--
--Eastlake 3rd & Hansen Informational [Page 87]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd"
-- "\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd"
-- "\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd"
-- "\xdd\xdd\xdd\xdd\xdd"
-- }, { 50 }, {
-- /* HMAC-SHA-1 */
-- "125D7342B9AC11CD91A39AF48AA17B4F63F175D3",
-- /* HMAC-SHA-224 */
-- "7FB3CB3588C6C1F6FFA9694D7D6AD2649365B0C1F65D69D1EC8333EA",
-- /* HMAC-SHA-256 */
-- "773EA91E36800E46854DB8EBD09181A72959098B3EF8C122D9635514CED5"
-- "65FE",
-- /* HMAC-SHA-384 */
-- "88062608D3E6AD8A0AA2ACE014C8A86F0AA635D947AC9FEBE83EF4E55966"
-- "144B2A5AB39DC13814B94E3AB6E101A34F27",
-- /* HMAC-SHA-512 */
-- "FA73B0089D56A284EFB0F0756C890BE9B1B5DBDD8EE81A3655F83E33B227"
-- "9D39BF3E848279A722C806B485A47E67C807B946A337BEE8942674278859"
-- "E13292FB"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- },
-- { /* 4 */ {
-- "\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
-- "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19"
-- }, { 25 }, {
-- "\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd"
-- "\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd"
-- "\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd\xcd"
-- "\xcd\xcd\xcd\xcd\xcd"
-- }, { 50 }, {
-- /* HMAC-SHA-1 */
-- "4C9007F4026250C6BC8414F9BF50C86C2D7235DA",
-- /* HMAC-SHA-224 */
-- "6C11506874013CAC6A2ABC1BB382627CEC6A90D86EFC012DE7AFEC5A",
-- /* HMAC-SHA-256 */
-- "82558A389A443C0EA4CC819899F2083A85F0FAA3E578F8077A2E3FF46729"
-- "665B",
-- /* HMAC-SHA-384 */
-- "3E8A69B7783C25851933AB6290AF6CA77A9981480850009CC5577C6E1F57"
-- "3B4E6801DD23C4A7D679CCF8A386C674CFFB",
-- /* HMAC-SHA-512 */
-- "B0BA465637458C6990E5A8C5F61D4AF7E576D97FF94B872DE76F8050361E"
-- "E3DBA91CA5C11AA25EB4D679275CC5788063A5F19741120C4F2DE2ADEBEB"
-- "10A298DD"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- },
--
--
--
--Eastlake 3rd & Hansen Informational [Page 88]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- { /* 5 */ {
-- "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
-- "\x0c\x0c\x0c\x0c\x0c"
-- }, { 20 }, {
-- "Test With Truncation"
-- }, { 20 }, {
-- /* HMAC-SHA-1 */
-- "4C1A03424B55E07FE7F27BE1",
-- /* HMAC-SHA-224 */
-- "0E2AEA68A90C8D37C988BCDB9FCA6FA8",
-- /* HMAC-SHA-256 */
-- "A3B6167473100EE06E0C796C2955552B",
-- /* HMAC-SHA-384 */
-- "3ABF34C3503B2A23A46EFC619BAEF897",
-- /* HMAC-SHA-512 */
-- "415FAD6271580A531D4179BC891D87A6"
-- }, { 12, 16, 16, 16, 16 }
-- },
-- { /* 6 */ {
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- }, { 80, 131 }, {
-- "Test Using Larger Than Block-Size Key - Hash Key First"
-- }, { 54 }, {
-- /* HMAC-SHA-1 */
-- "AA4AE5E15272D00E95705637CE8A3B55ED402112",
-- /* HMAC-SHA-224 */
-- "95E9A0DB962095ADAEBE9B2D6F0DBCE2D499F112F2D2B7273FA6870E",
-- /* HMAC-SHA-256 */
-- "60E431591EE0B67F0D8A26AACBF5B77F8E0BC6213728C5140546040F0EE3"
-- "7F54",
-- /* HMAC-SHA-384 */
-- "4ECE084485813E9088D2C63A041BC5B44F9EF1012A2B588F3CD11F05033A"
-- "C4C60C2EF6AB4030FE8296248DF163F44952",
-- /* HMAC-SHA-512 */
-- "80B24263C7C1A3EBB71493C1DD7BE8B49B46D1F41B4AEEC1121B013783F8"
-- "F3526B56D037E05F2598BD0FD2215D6A1E5295E64F73F63F0AEC8B915A98"
-- "5D786598"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- },
--
--
--
--Eastlake 3rd & Hansen Informational [Page 89]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- { /* 7 */ {
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa"
-- }, { 80, 131 }, {
-- "Test Using Larger Than Block-Size Key and "
-- "Larger Than One Block-Size Data",
-- "\x54\x68\x69\x73\x20\x69\x73\x20\x61\x20\x74\x65\x73\x74\x20"
-- "\x75\x73\x69\x6e\x67\x20\x61\x20\x6c\x61\x72\x67\x65\x72\x20"
-- "\x74\x68\x61\x6e\x20\x62\x6c\x6f\x63\x6b\x2d\x73\x69\x7a\x65"
-- "\x20\x6b\x65\x79\x20\x61\x6e\x64\x20\x61\x20\x6c\x61\x72\x67"
-- "\x65\x72\x20\x74\x68\x61\x6e\x20\x62\x6c\x6f\x63\x6b\x2d\x73"
-- "\x69\x7a\x65\x20\x64\x61\x74\x61\x2e\x20\x54\x68\x65\x20\x6b"
-- "\x65\x79\x20\x6e\x65\x65\x64\x73\x20\x74\x6f\x20\x62\x65\x20"
-- "\x68\x61\x73\x68\x65\x64\x20\x62\x65\x66\x6f\x72\x65\x20\x62"
-- "\x65\x69\x6e\x67\x20\x75\x73\x65\x64\x20\x62\x79\x20\x74\x68"
-- "\x65\x20\x48\x4d\x41\x43\x20\x61\x6c\x67\x6f\x72\x69\x74\x68"
-- "\x6d\x2e"
-- /* "This is a test using a larger than block-size key and a "
-- "larger than block-size data. The key needs to be hashed "
-- "before being used by the HMAC algorithm." */
-- }, { 73, 152 }, {
-- /* HMAC-SHA-1 */
-- "E8E99D0F45237D786D6BBAA7965C7808BBFF1A91",
-- /* HMAC-SHA-224 */
-- "3A854166AC5D9F023F54D517D0B39DBD946770DB9C2B95C9F6F565D1",
-- /* HMAC-SHA-256 */
-- "9B09FFA71B942FCB27635FBCD5B0E944BFDC63644F0713938A7F51535C3A"
-- "35E2",
-- /* HMAC-SHA-384 */
-- "6617178E941F020D351E2F254E8FD32C602420FEB0B8FB9ADCCEBB82461E"
-- "99C5A678CC31E799176D3860E6110C46523E",
-- /* HMAC-SHA-512 */
-- "E37B6A775DC87DBAA4DFA9F96E5E3FFDDEBD71F8867289865DF5A32D20CD"
-- "C944B6022CAC3C4982B10D5EEB55C3E4DE15134676FB6DE0446065C97440"
-- "FA8C6A58"
-- }, { SHA1HashSize, SHA224HashSize, SHA256HashSize,
-- SHA384HashSize, SHA512HashSize }
-- }
--};
--
--/*
--
--
--
--Eastlake 3rd & Hansen Informational [Page 90]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * Check the hash value against the expected string, expressed in hex
-- */
--static const char hexdigits[] = "0123456789ABCDEF";
--int checkmatch(const unsigned char *hashvalue,
-- const char *hexstr, int hashsize)
--{
-- int i;
-- for (i = 0; i < hashsize; ++i) {
-- if (*hexstr++ != hexdigits[(hashvalue[i] >> 4) & 0xF])
-- return 0;
-- if (*hexstr++ != hexdigits[hashvalue[i] & 0xF]) return 0;
-- }
-- return 1;
--}
--
--/*
-- * Print the string, converting non-printable characters to "."
-- */
--void printstr(const char *str, int len)
--{
-- for ( ; len-- > 0; str++)
-- putchar(isprint((unsigned char)*str) ? *str : '.');
--}
--
--/*
-- * Print the string, converting non-printable characters to hex "## ".
-- */
--void printxstr(const char *str, int len)
--{
-- for ( ; len-- > 0; str++)
-- printf("%c%c ", hexdigits[(*str >> 4) & 0xF],
-- hexdigits[*str & 0xF]);
--}
--
--/*
-- * Print a usage message.
-- */
--void usage(const char *argv0)
--{
-- fprintf(stderr,
-- "Usage:\n"
-- "Common options: [-h hash] [-w|-x] [-H]\n"
-- "Standard tests:\n"
-- "\t%s [-m] [-l loopcount] [-t test#] [-e]\n"
-- "\t\t[-r randomseed] [-R randomloop-count] "
-- "[-p] [-P|-X]\n"
-- "Hash a string:\n"
-- "\t%s [-S expectedresult] -s hashstr [-k key]\n"
--
--
--
--Eastlake 3rd & Hansen Informational [Page 91]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- "Hash a file:\n"
-- "\t%s [-S expectedresult] -f file [-k key]\n"
-- "Hash a file, ignoring whitespace:\n"
-- "\t%s [-S expectedresult] -F file [-k key]\n"
-- "Additional bits to add in: [-B bitcount -b bits]\n"
-- "-h\thash to test: "
-- "0|SHA1, 1|SHA224, 2|SHA256, 3|SHA384, 4|SHA512\n"
-- "-m\tperform hmac test\n"
-- "-k\tkey for hmac test\n"
-- "-t\ttest case to run, 1-10\n"
-- "-l\thow many times to run the test\n"
-- "-e\ttest error returns\n"
-- "-p\tdo not print results\n"
-- "-P\tdo not print PASSED/FAILED\n"
-- "-X\tprint FAILED, but not PASSED\n"
-- "-r\tseed for random test\n"
-- "-R\thow many times to run random test\n"
-- "-s\tstring to hash\n"
-- "-S\texpected result of hashed string, in hex\n"
-- "-w\toutput hash in raw format\n"
-- "-x\toutput hash in hex format\n"
-- "-B\t# extra bits to add in after string or file input\n"
-- "-b\textra bits to add (high order bits of #, 0# or 0x#)\n"
-- "-H\tinput hashstr or randomseed is in hex\n"
-- , argv0, argv0, argv0, argv0);
-- exit(1);
--}
--
--/*
-- * Print the results and PASS/FAIL.
-- */
--void printResult(uint8_t *Message_Digest, int hashsize,
-- const char *hashname, const char *testtype, const char *testname,
-- const char *resultarray, int printResults, int printPassFail)
--{
-- int i, k;
-- if (printResults == PRINTTEXT) {
-- putchar('\t');
-- for (i = 0; i < hashsize ; ++i) {
-- putchar(hexdigits[(Message_Digest[i] >> 4) & 0xF]);
-- putchar(hexdigits[Message_Digest[i] & 0xF]);
-- putchar(' ');
-- }
-- putchar('\n');
-- } else if (printResults == PRINTRAW) {
-- fwrite(Message_Digest, 1, hashsize, stdout);
-- } else if (printResults == PRINTHEX) {
-- for (i = 0; i < hashsize ; ++i) {
--
--
--
--Eastlake 3rd & Hansen Informational [Page 92]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- putchar(hexdigits[(Message_Digest[i] >> 4) & 0xF]);
-- putchar(hexdigits[Message_Digest[i] & 0xF]);
-- }
-- putchar('\n');
-- }
--
-- if (printResults && resultarray) {
-- printf(" Should match:\n\t");
-- for (i = 0, k = 0; i < hashsize; i++, k += 2) {
-- putchar(resultarray[k]);
-- putchar(resultarray[k+1]);
-- putchar(' ');
-- }
-- putchar('\n');
-- }
--
-- if (printPassFail && resultarray) {
-- int ret = checkmatch(Message_Digest, resultarray, hashsize);
-- if ((printPassFail == PRINTPASSFAIL) || !ret)
-- printf("%s %s %s: %s\n", hashname, testtype, testname,
-- ret ? "PASSED" : "FAILED");
-- }
--}
--
--/*
-- * Exercise a hash series of functions. The input is the testarray,
-- * repeated repeatcount times, followed by the extrabits. If the
-- * result is known, it is in resultarray in uppercase hex.
-- */
--int hash(int testno, int loopno, int hashno,
-- const char *testarray, int length, long repeatcount,
-- int numberExtrabits, int extrabits, const unsigned char *keyarray,
-- int keylen, const char *resultarray, int hashsize, int printResults,
-- int printPassFail)
--{
-- USHAContext sha;
-- HMACContext hmac;
-- int err, i;
-- uint8_t Message_Digest[USHAMaxHashSize];
-- char buf[20];
--
-- if (printResults == PRINTTEXT) {
-- printf("\nTest %d: Iteration %d, Repeat %ld\n\t'", testno+1,
-- loopno, repeatcount);
-- printstr(testarray, length);
-- printf("'\n\t'");
-- printxstr(testarray, length);
-- printf("'\n");
--
--
--
--Eastlake 3rd & Hansen Informational [Page 93]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- printf(" Length=%d bytes (%d bits), ", length, length * 8);
-- printf("ExtraBits %d: %2.2x\n", numberExtrabits, extrabits);
-- }
--
-- memset(&sha, '\343', sizeof(sha)); /* force bad data into struct */
-- memset(&hmac, '\343', sizeof(hmac));
-- err = keyarray ? hmacReset(&hmac, hashes[hashno].whichSha,
-- keyarray, keylen) :
-- USHAReset(&sha, hashes[hashno].whichSha);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hash(): %sReset Error %d.\n",
-- keyarray ? "hmac" : "sha", err);
-- return err;
-- }
--
-- for (i = 0; i < repeatcount; ++i) {
-- err = keyarray ? hmacInput(&hmac, (const uint8_t *) testarray,
-- length) :
-- USHAInput(&sha, (const uint8_t *) testarray,
-- length);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hash(): %sInput Error %d.\n",
-- keyarray ? "hmac" : "sha", err);
-- return err;
-- }
-- }
--
-- if (numberExtrabits > 0) {
-- err = keyarray ? hmacFinalBits(&hmac, (uint8_t) extrabits,
-- numberExtrabits) :
-- USHAFinalBits(&sha, (uint8_t) extrabits,
-- numberExtrabits);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hash(): %sFinalBits Error %d.\n",
-- keyarray ? "hmac" : "sha", err);
-- return err;
-- }
-- }
--
-- err = keyarray ? hmacResult(&hmac, Message_Digest) :
-- USHAResult(&sha, Message_Digest);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hash(): %s Result Error %d, could not "
-- "compute message digest.\n", keyarray ? "hmac" : "sha", err);
-- return err;
-- }
--
-- sprintf(buf, "%d", testno+1);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 94]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- printResult(Message_Digest, hashsize, hashes[hashno].name,
-- keyarray ? "hmac standard test" : "sha standard test", buf,
-- resultarray, printResults, printPassFail);
--
-- return err;
--}
--
--/*
-- * Exercise a hash series of functions. The input is a filename.
-- * If the result is known, it is in resultarray in uppercase hex.
-- */
--int hashfile(int hashno, const char *hashfilename, int bits,
-- int bitcount, int skipSpaces, const unsigned char *keyarray,
-- int keylen, const char *resultarray, int hashsize,
-- int printResults, int printPassFail)
--{
-- USHAContext sha;
-- HMACContext hmac;
-- int err, nread, c;
-- unsigned char buf[4096];
-- uint8_t Message_Digest[USHAMaxHashSize];
-- unsigned char cc;
-- FILE *hashfp = (strcmp(hashfilename, "-") == 0) ? stdin :
-- fopen(hashfilename, "r");
--
-- if (!hashfp) {
-- fprintf(stderr, "cannot open file '%s'\n", hashfilename);
-- return shaStateError;
-- }
--
-- memset(&sha, '\343', sizeof(sha)); /* force bad data into struct */
-- memset(&hmac, '\343', sizeof(hmac));
-- err = keyarray ? hmacReset(&hmac, hashes[hashno].whichSha,
-- keyarray, keylen) :
-- USHAReset(&sha, hashes[hashno].whichSha);
--
-- if (err != shaSuccess) {
-- fprintf(stderr, "hashfile(): %sReset Error %d.\n",
-- keyarray ? "hmac" : "sha", err);
-- return err;
-- }
--
-- if (skipSpaces)
-- while ((c = getc(hashfp)) != EOF) {
-- if (!isspace(c)) {
-- cc = (unsigned char)c;
-- err = keyarray ? hmacInput(&hmac, &cc, 1) :
-- USHAInput(&sha, &cc, 1);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 95]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- if (err != shaSuccess) {
-- fprintf(stderr, "hashfile(): %sInput Error %d.\n",
-- keyarray ? "hmac" : "sha", err);
-- if (hashfp != stdin) fclose(hashfp);
-- return err;
-- }
-- }
-- }
-- else
-- while ((nread = fread(buf, 1, sizeof(buf), hashfp)) > 0) {
-- err = keyarray ? hmacInput(&hmac, buf, nread) :
-- USHAInput(&sha, buf, nread);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hashfile(): %s Error %d.\n",
-- keyarray ? "hmacInput" : "shaInput", err);
-- if (hashfp != stdin) fclose(hashfp);
-- return err;
-- }
-- }
--
-- if (bitcount > 0)
-- err = keyarray ? hmacFinalBits(&hmac, bits, bitcount) :
-- USHAFinalBits(&sha, bits, bitcount);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hashfile(): %s Error %d.\n",
-- keyarray ? "hmacResult" : "shaResult", err);
-- if (hashfp != stdin) fclose(hashfp);
-- return err;
-- }
--
-- err = keyarray ? hmacResult(&hmac, Message_Digest) :
-- USHAResult(&sha, Message_Digest);
-- if (err != shaSuccess) {
-- fprintf(stderr, "hashfile(): %s Error %d.\n",
-- keyarray ? "hmacResult" : "shaResult", err);
-- if (hashfp != stdin) fclose(hashfp);
-- return err;
-- }
--
-- printResult(Message_Digest, hashsize, hashes[hashno].name, "file",
-- hashfilename, resultarray, printResults, printPassFail);
--
-- if (hashfp != stdin) fclose(hashfp);
-- return err;
--}
--
--/*
-- * Exercise a hash series of functions through multiple permutations.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 96]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- * The input is an initial seed. That seed is replicated 3 times.
-- * For 1000 rounds, the previous three results are used as the input.
-- * This result is then checked, and used to seed the next cycle.
-- * If the result is known, it is in resultarrays in uppercase hex.
-- */
--void randomtest(int hashno, const char *seed, int hashsize,
-- const char **resultarrays, int randomcount,
-- int printResults, int printPassFail)
--{
-- int i, j; char buf[20];
-- unsigned char SEED[USHAMaxHashSize], MD[1003][USHAMaxHashSize];
--
-- /* INPUT: Seed - A random seed n bits long */
-- memcpy(SEED, seed, hashsize);
-- if (printResults == PRINTTEXT) {
-- printf("%s random test seed= '", hashes[hashno].name);
-- printxstr(seed, hashsize);
-- printf("'\n");
-- }
--
-- for (j = 0; j < randomcount; j++) {
-- /* MD0 = MD1 = MD2 = Seed; */
-- memcpy(MD[0], SEED, hashsize);
-- memcpy(MD[1], SEED, hashsize);
-- memcpy(MD[2], SEED, hashsize);
-- for (i=3; i<1003; i++) {
-- /* Mi = MDi-3 || MDi-2 || MDi-1; */
-- USHAContext Mi;
-- memset(&Mi, '\343', sizeof(Mi)); /* force bad data into struct */
-- USHAReset(&Mi, hashes[hashno].whichSha);
-- USHAInput(&Mi, MD[i-3], hashsize);
-- USHAInput(&Mi, MD[i-2], hashsize);
-- USHAInput(&Mi, MD[i-1], hashsize);
-- /* MDi = SHA(Mi); */
-- USHAResult(&Mi, MD[i]);
-- }
--
-- /* MDj = Seed = MDi; */
-- memcpy(SEED, MD[i-1], hashsize);
--
-- /* OUTPUT: MDj */
-- sprintf(buf, "%d", j);
-- printResult(SEED, hashsize, hashes[hashno].name, "random test",
-- buf, resultarrays ? resultarrays[j] : 0, printResults,
-- (j < RANDOMCOUNT) ? printPassFail : 0);
-- }
--}
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 97]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--/*
-- * Look up a hash name.
-- */
--int findhash(const char *argv0, const char *opt)
--{
-- int i;
-- const char *names[HASHCOUNT][2] = {
-- { "0", "sha1" }, { "1", "sha224" }, { "2", "sha256" },
-- { "3", "sha384" }, { "4", "sha512" }
-- };
--
-- for (i = 0; i < HASHCOUNT; i++)
-- if ((strcmp(opt, names[i][0]) == 0) ||
-- (scasecmp(opt, names[i][1]) == 0))
-- return i;
--
-- fprintf(stderr, "%s: Unknown hash name: '%s'\n", argv0, opt);
-- usage(argv0);
-- return 0;
--}
--
--/*
-- * Run some tests that should invoke errors.
-- */
--void testErrors(int hashnolow, int hashnohigh, int printResults,
-- int printPassFail)
--{
-- USHAContext usha;
-- uint8_t Message_Digest[USHAMaxHashSize];
-- int hashno, err;
--
-- for (hashno = hashnolow; hashno <= hashnohigh; hashno++) {
-- memset(&usha, '\343', sizeof(usha)); /* force bad data */
-- USHAReset(&usha, hashno);
-- USHAResult(&usha, Message_Digest);
-- err = USHAInput(&usha, (const unsigned char *)"foo", 3);
-- if (printResults == PRINTTEXT)
-- printf ("\nError %d. Should be %d.\n", err, shaStateError);
-- if ((printPassFail == PRINTPASSFAIL) ||
-- ((printPassFail == PRINTFAIL) && (err != shaStateError)))
-- printf("%s se: %s\n", hashes[hashno].name,
-- (err == shaStateError) ? "PASSED" : "FAILED");
--
-- err = USHAFinalBits(&usha, 0x80, 3);
-- if (printResults == PRINTTEXT)
-- printf ("\nError %d. Should be %d.\n", err, shaStateError);
-- if ((printPassFail == PRINTPASSFAIL) ||
-- ((printPassFail == PRINTFAIL) && (err != shaStateError)))
--
--
--
--Eastlake 3rd & Hansen Informational [Page 98]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- printf("%s se: %s\n", hashes[hashno].name,
-- (err == shaStateError) ? "PASSED" : "FAILED");
--
-- err = USHAReset(0, hashes[hashno].whichSha);
-- if (printResults == PRINTTEXT)
-- printf("\nError %d. Should be %d.\n", err, shaNull);
-- if ((printPassFail == PRINTPASSFAIL) ||
-- ((printPassFail == PRINTFAIL) && (err != shaNull)))
-- printf("%s usha null: %s\n", hashes[hashno].name,
-- (err == shaNull) ? "PASSED" : "FAILED");
--
-- switch (hashno) {
-- case SHA1: err = SHA1Reset(0); break;
-- case SHA224: err = SHA224Reset(0); break;
-- case SHA256: err = SHA256Reset(0); break;
-- case SHA384: err = SHA384Reset(0); break;
-- case SHA512: err = SHA512Reset(0); break;
-- }
-- if (printResults == PRINTTEXT)
-- printf("\nError %d. Should be %d.\n", err, shaNull);
-- if ((printPassFail == PRINTPASSFAIL) ||
-- ((printPassFail == PRINTFAIL) && (err != shaNull)))
-- printf("%s sha null: %s\n", hashes[hashno].name,
-- (err == shaNull) ? "PASSED" : "FAILED");
-- }
--}
--
--/* replace a hex string in place with its value */
--int unhexStr(char *hexstr)
--{
-- char *o = hexstr;
-- int len = 0, nibble1 = 0, nibble2 = 0;
-- if (!hexstr) return 0;
-- for ( ; *hexstr; hexstr++) {
-- if (isalpha((int)(unsigned char)(*hexstr))) {
-- nibble1 = tolower(*hexstr) - 'a' + 10;
-- } else if (isdigit((int)(unsigned char)(*hexstr))) {
-- nibble1 = *hexstr - '0';
-- } else {
-- printf("\nError: bad hex character '%c'\n", *hexstr);
-- }
-- if (!*++hexstr) break;
-- if (isalpha((int)(unsigned char)(*hexstr))) {
-- nibble2 = tolower(*hexstr) - 'a' + 10;
-- } else if (isdigit((int)(unsigned char)(*hexstr))) {
-- nibble2 = *hexstr - '0';
-- } else {
-- printf("\nError: bad hex character '%c'\n", *hexstr);
--
--
--
--Eastlake 3rd & Hansen Informational [Page 99]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- }
-- *o++ = (char)((nibble1 << 4) | nibble2);
-- len++;
-- }
-- return len;
--}
--
--int main(int argc, char **argv)
--{
-- int i, err;
-- int loopno, loopnohigh = 1;
-- int hashno, hashnolow = 0, hashnohigh = HASHCOUNT - 1;
-- int testno, testnolow = 0, testnohigh;
-- int ntestnohigh = 0;
-- int printResults = PRINTTEXT;
-- int printPassFail = 1;
-- int checkErrors = 0;
-- char *hashstr = 0;
-- int hashlen = 0;
-- const char *resultstr = 0;
-- char *randomseedstr = 0;
-- int runHmacTests = 0;
-- char *hmacKey = 0;
-- int hmaclen = 0;
-- int randomcount = RANDOMCOUNT;
-- const char *hashfilename = 0;
-- const char *hashFilename = 0;
-- int extrabits = 0, numberExtrabits = 0;
-- int strIsHex = 0;
--
-- while ((i = xgetopt(argc, argv, "b:B:ef:F:h:Hk:l:mpPr:R:s:S:t:wxX"))
-- != -1)
-- switch (i) {
-- case 'b': extrabits = strtol(xoptarg, 0, 0); break;
-- case 'B': numberExtrabits = atoi(xoptarg); break;
-- case 'e': checkErrors = 1; break;
-- case 'f': hashfilename = xoptarg; break;
-- case 'F': hashFilename = xoptarg; break;
-- case 'h': hashnolow = hashnohigh = findhash(argv[0], xoptarg);
-- break;
-- case 'H': strIsHex = 1; break;
-- case 'k': hmacKey = xoptarg; hmaclen = strlen(xoptarg); break;
-- case 'l': loopnohigh = atoi(xoptarg); break;
-- case 'm': runHmacTests = 1; break;
-- case 'P': printPassFail = 0; break;
-- case 'p': printResults = PRINTNONE; break;
-- case 'R': randomcount = atoi(xoptarg); break;
-- case 'r': randomseedstr = xoptarg; break;
--
--
--
--Eastlake 3rd & Hansen Informational [Page 100]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- case 's': hashstr = xoptarg; hashlen = strlen(hashstr); break;
-- case 'S': resultstr = xoptarg; break;
-- case 't': testnolow = ntestnohigh = atoi(xoptarg) - 1; break;
-- case 'w': printResults = PRINTRAW; break;
-- case 'x': printResults = PRINTHEX; break;
-- case 'X': printPassFail = 2; break;
-- default: usage(argv[0]);
-- }
--
-- if (strIsHex) {
-- hashlen = unhexStr(hashstr);
-- unhexStr(randomseedstr);
-- hmaclen = unhexStr(hmacKey);
-- }
-- testnohigh = (ntestnohigh != 0) ? ntestnohigh:
-- runHmacTests ? (HMACTESTCOUNT-1) : (TESTCOUNT-1);
-- if ((testnolow < 0) ||
-- (testnohigh >= (runHmacTests ? HMACTESTCOUNT : TESTCOUNT)) ||
-- (hashnolow < 0) || (hashnohigh >= HASHCOUNT) ||
-- (hashstr && (testnolow == testnohigh)) ||
-- (randomcount < 0) ||
-- (resultstr && (!hashstr && !hashfilename && !hashFilename)) ||
-- ((runHmacTests || hmacKey) && randomseedstr) ||
-- (hashfilename && hashFilename))
-- usage(argv[0]);
--
-- /*
-- * Perform SHA/HMAC tests
-- */
-- for (hashno = hashnolow; hashno <= hashnohigh; ++hashno) {
-- if (printResults == PRINTTEXT)
-- printf("Hash %s\n", hashes[hashno].name);
-- err = shaSuccess;
--
-- for (loopno = 1; (loopno <= loopnohigh) && (err == shaSuccess);
-- ++loopno) {
-- if (hashstr)
-- err = hash(0, loopno, hashno, hashstr, hashlen, 1,
-- numberExtrabits, extrabits, (const unsigned char *)hmacKey,
-- hmaclen, resultstr, hashes[hashno].hashsize, printResults,
-- printPassFail);
--
-- else if (randomseedstr)
-- randomtest(hashno, randomseedstr, hashes[hashno].hashsize, 0,
-- randomcount, printResults, printPassFail);
--
-- else if (hashfilename)
-- err = hashfile(hashno, hashfilename, extrabits,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 101]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- numberExtrabits, 0,
-- (const unsigned char *)hmacKey, hmaclen,
-- resultstr, hashes[hashno].hashsize,
-- printResults, printPassFail);
--
-- else if (hashFilename)
-- err = hashfile(hashno, hashFilename, extrabits,
-- numberExtrabits, 1,
-- (const unsigned char *)hmacKey, hmaclen,
-- resultstr, hashes[hashno].hashsize,
-- printResults, printPassFail);
--
-- else /* standard tests */ {
-- for (testno = testnolow;
-- (testno <= testnohigh) && (err == shaSuccess); ++testno) {
-- if (runHmacTests) {
-- err = hash(testno, loopno, hashno,
-- hmachashes[testno].dataarray[hashno] ?
-- hmachashes[testno].dataarray[hashno] :
-- hmachashes[testno].dataarray[1] ?
-- hmachashes[testno].dataarray[1] :
-- hmachashes[testno].dataarray[0],
-- hmachashes[testno].datalength[hashno] ?
-- hmachashes[testno].datalength[hashno] :
-- hmachashes[testno].datalength[1] ?
-- hmachashes[testno].datalength[1] :
-- hmachashes[testno].datalength[0],
-- 1, 0, 0,
-- (const unsigned char *)(
-- hmachashes[testno].keyarray[hashno] ?
-- hmachashes[testno].keyarray[hashno] :
-- hmachashes[testno].keyarray[1] ?
-- hmachashes[testno].keyarray[1] :
-- hmachashes[testno].keyarray[0]),
-- hmachashes[testno].keylength[hashno] ?
-- hmachashes[testno].keylength[hashno] :
-- hmachashes[testno].keylength[1] ?
-- hmachashes[testno].keylength[1] :
-- hmachashes[testno].keylength[0],
-- hmachashes[testno].resultarray[hashno],
-- hmachashes[testno].resultlength[hashno],
-- printResults, printPassFail);
-- } else {
-- err = hash(testno, loopno, hashno,
-- hashes[hashno].tests[testno].testarray,
-- hashes[hashno].tests[testno].length,
-- hashes[hashno].tests[testno].repeatcount,
-- hashes[hashno].tests[testno].numberExtrabits,
--
--
--
--Eastlake 3rd & Hansen Informational [Page 102]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- hashes[hashno].tests[testno].extrabits, 0, 0,
-- hashes[hashno].tests[testno].resultarray,
-- hashes[hashno].hashsize,
-- printResults, printPassFail);
-- }
-- }
--
-- if (!runHmacTests) {
-- randomtest(hashno, hashes[hashno].randomtest,
-- hashes[hashno].hashsize, hashes[hashno].randomresults,
-- RANDOMCOUNT, printResults, printPassFail);
-- }
-- }
-- }
-- }
--
-- /* Test some error returns */
-- if (checkErrors) {
-- testErrors(hashnolow, hashnohigh, printResults, printPassFail);
-- }
--
-- return 0;
--}
--
--/*
-- * Compare two strings, case independently.
-- * Equivalent to strcasecmp() found on some systems.
-- */
--int scasecmp(const char *s1, const char *s2)
--{
-- for (;;) {
-- char u1 = tolower(*s1++);
-- char u2 = tolower(*s2++);
-- if (u1 != u2)
-- return u1 - u2;
-- if (u1 == '\0')
-- return 0;
-- }
--}
--
--/*
-- * This is a copy of getopt provided for those systems that do not
-- * have it. The name was changed to xgetopt to not conflict on those
-- * systems that do have it. Similarly, optarg, optind and opterr
-- * were renamed to xoptarg, xoptind and xopterr.
-- *
-- * Copyright 1990, 1991, 1992 by the Massachusetts Institute of
-- * Technology and UniSoft Group Limited.
--
--
--
--Eastlake 3rd & Hansen Informational [Page 103]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- *
-- * Permission to use, copy, modify, distribute, and sell this software
-- * and its documentation for any purpose is hereby granted without fee,
-- * provided that the above copyright notice appear in all copies and
-- * that both that copyright notice and this permission notice appear in
-- * supporting documentation, and that the names of MIT and UniSoft not
-- * be used in advertising or publicity pertaining to distribution of
-- * the software without specific, written prior permission. MIT and
-- * UniSoft make no representations about the suitability of this
-- * software for any purpose. It is provided "as is" without express
-- * or implied warranty.
-- *
-- * $XConsortium: getopt.c,v 1.2 92/07/01 11:59:04 rws Exp $
-- * NB: Reformatted to match above style.
-- */
--
--char *xoptarg;
--int xoptind = 1;
--int xopterr = 1;
--
--static int xgetopt(int argc, char **argv, const char *optstring)
--{
-- static int avplace;
-- char *ap;
-- char *cp;
-- int c;
--
-- if (xoptind >= argc)
-- return EOF;
--
-- ap = argv[xoptind] + avplace;
--
-- /* At beginning of arg but not an option */
-- if (avplace == 0) {
-- if (ap[0] != '-')
-- return EOF;
-- else if (ap[1] == '-') {
-- /* Special end of options option */
-- xoptind++;
-- return EOF;
-- } else if (ap[1] == '\0')
-- return EOF; /* single '-' is not allowed */
-- }
--
-- /* Get next letter */
-- avplace++;
-- c = *++ap;
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 104]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
-- cp = strchr(optstring, c);
-- if (cp == NULL || c == ':') {
-- if (xopterr)
-- fprintf(stderr, "Unrecognised option -- %c\n", c);
-- return '?';
-- }
--
-- if (cp[1] == ':') {
-- /* There should be an option arg */
-- avplace = 0;
-- if (ap[1] == '\0') {
-- /* It is a separate arg */
-- if (++xoptind >= argc) {
-- if (xopterr)
-- fprintf(stderr, "Option requires an argument\n");
-- return '?';
-- }
-- xoptarg = argv[xoptind++];
-- } else {
-- /* is attached to option letter */
-- xoptarg = ap + 1;
-- ++xoptind;
-- }
-- } else {
-- /* If we are out of letters then go to next arg */
-- if (ap[1] == '\0') {
-- ++xoptind;
-- avplace = 0;
-- }
--
-- xoptarg = NULL;
-- }
-- return c;
--}
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 105]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--9. Security Considerations
--
-- This document is intended to provides the Internet community
-- convenient access to source code that implements the United States of
-- America Federal Information Processing Standard Secure Hash
-- Algorithms (SHAs) [FIPS180-2] and HMACs based upon these one-way hash
-- functions. See license in Section 1.1. No independent assertion of
-- the security of this hash function by the authors for any particular
-- use is intended.
--
--10. Normative References
--
-- [FIPS180-2] "Secure Hash Standard", United States of America,
-- National Institute of Standards and Technology, Federal
-- Information Processing Standard (FIPS) 180-2,
-- http://csrc.nist.gov/publications/fips/fips180-2/
-- fips180-2withchangenotice.pdf.
--
-- [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
-- Hashing for Message Authentication", RFC 2104, February
-- 1997.
--
--11. Informative References
--
-- [RFC2202] Cheng, P. and R. Glenn, "Test Cases for HMAC-MD5 and
-- HMAC-SHA-1", RFC 2202, September 1997.
--
-- [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm
-- 1 (SHA1)", RFC 3174, September 2001.
--
-- [RFC3874] Housley, R., "A 224-bit One-way Hash Function: SHA-224",
-- RFC 3874, September 2004.
--
-- [RFC4086] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
-- "Randomness Requirements for Security", BCP 106, RFC
-- 4086, June 2005.
--
-- [RFC4231] Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-
-- 224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512", RFC
-- 4231, December 2005.
--
-- [SHAVS] "The Secure Hash Algorithm Validation System (SHAVS)",
-- http://csrc.nist.gov/cryptval/shs/SHAVS.pdf.
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 106]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--Authors' Addresses
--
-- Donald E. Eastlake, 3rd
-- Motorola Laboratories
-- 155 Beaver Street
-- Milford, MA 01757 USA
--
-- Phone: +1-508-786-7554 (w)
-- EMail: donald.eastlake@motorola.com
--
--
-- Tony Hansen
-- AT&T Laboratories
-- 200 Laurel Ave.
-- Middletown, NJ 07748 USA
--
-- Phone: +1-732-420-8934 (w)
-- EMail: tony+shs@maillennium.att.com
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 107]
--\f
--RFC 4634 SHAs and HMAC-SHAs July 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Eastlake 3rd & Hansen Informational [Page 108]
--\f
+++ /dev/null
--
--
--
--
--
--
--Network Working Group O. Kolkman
--Request for Comments: 4641 R. Gieben
--Obsoletes: 2541 NLnet Labs
--Category: Informational September 2006
--
--
-- DNSSEC Operational Practices
--
--Status of This Memo
--
-- This memo provides information for the Internet community. It does
-- not specify an Internet standard of any kind. Distribution of this
-- memo is unlimited.
--
--Copyright Notice
--
-- Copyright (C) The Internet Society (2006).
--
--Abstract
--
-- This document describes a set of practices for operating the DNS with
-- security extensions (DNSSEC). The target audience is zone
-- administrators deploying DNSSEC.
--
-- The document discusses operational aspects of using keys and
-- signatures in the DNS. It discusses issues of key generation, key
-- storage, signature generation, key rollover, and related policies.
--
-- This document obsoletes RFC 2541, as it covers more operational
-- ground and gives more up-to-date requirements with respect to key
-- sizes and the new DNSSEC specification.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 1]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--Table of Contents
--
-- 1. Introduction ....................................................3
-- 1.1. The Use of the Term 'key' ..................................4
-- 1.2. Time Definitions ...........................................4
-- 2. Keeping the Chain of Trust Intact ...............................5
-- 3. Keys Generation and Storage .....................................6
-- 3.1. Zone and Key Signing Keys ..................................6
-- 3.1.1. Motivations for the KSK and ZSK Separation ..........6
-- 3.1.2. KSKs for High-Level Zones ...........................7
-- 3.2. Key Generation .............................................8
-- 3.3. Key Effectivity Period .....................................8
-- 3.4. Key Algorithm ..............................................9
-- 3.5. Key Sizes ..................................................9
-- 3.6. Private Key Storage .......................................11
-- 4. Signature Generation, Key Rollover, and Related Policies .......12
-- 4.1. Time in DNSSEC ............................................12
-- 4.1.1. Time Considerations ................................12
-- 4.2. Key Rollovers .............................................14
-- 4.2.1. Zone Signing Key Rollovers .........................14
-- 4.2.1.1. Pre-Publish Key Rollover ..................15
-- 4.2.1.2. Double Signature Zone Signing Key
-- Rollover ..................................17
-- 4.2.1.3. Pros and Cons of the Schemes ..............18
-- 4.2.2. Key Signing Key Rollovers ..........................18
-- 4.2.3. Difference Between ZSK and KSK Rollovers ...........20
-- 4.2.4. Automated Key Rollovers ............................21
-- 4.3. Planning for Emergency Key Rollover .......................21
-- 4.3.1. KSK Compromise .....................................22
-- 4.3.1.1. Keeping the Chain of Trust Intact .........22
-- 4.3.1.2. Breaking the Chain of Trust ...............23
-- 4.3.2. ZSK Compromise .....................................23
-- 4.3.3. Compromises of Keys Anchored in Resolvers ..........24
-- 4.4. Parental Policies .........................................24
-- 4.4.1. Initial Key Exchanges and Parental Policies
-- Considerations .....................................24
-- 4.4.2. Storing Keys or Hashes? ............................25
-- 4.4.3. Security Lameness ..................................25
-- 4.4.4. DS Signature Validity Period .......................26
-- 5. Security Considerations ........................................26
-- 6. Acknowledgments ................................................26
-- 7. References .....................................................27
-- 7.1. Normative References ......................................27
-- 7.2. Informative References ....................................28
-- Appendix A. Terminology ...........................................30
-- Appendix B. Zone Signing Key Rollover How-To ......................31
-- Appendix C. Typographic Conventions ...............................32
--
--
--
--
--Kolkman & Gieben Informational [Page 2]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--1. Introduction
--
-- This document describes how to run a DNS Security (DNSSEC)-enabled
-- environment. It is intended for operators who have knowledge of the
-- DNS (see RFC 1034 [1] and RFC 1035 [2]) and want to deploy DNSSEC.
-- See RFC 4033 [4] for an introduction to DNSSEC, RFC 4034 [5] for the
-- newly introduced Resource Records (RRs), and RFC 4035 [6] for the
-- protocol changes.
--
-- During workshops and early operational deployment tests, operators
-- and system administrators have gained experience about operating the
-- DNS with security extensions (DNSSEC). This document translates
-- these experiences into a set of practices for zone administrators.
-- At the time of writing, there exists very little experience with
-- DNSSEC in production environments; this document should therefore
-- explicitly not be seen as representing 'Best Current Practices'.
--
-- The procedures herein are focused on the maintenance of signed zones
-- (i.e., signing and publishing zones on authoritative servers). It is
-- intended that maintenance of zones such as re-signing or key
-- rollovers be transparent to any verifying clients on the Internet.
--
-- The structure of this document is as follows. In Section 2, we
-- discuss the importance of keeping the "chain of trust" intact.
-- Aspects of key generation and storage of private keys are discussed
-- in Section 3; the focus in this section is mainly on the private part
-- of the key(s). Section 4 describes considerations concerning the
-- public part of the keys. Since these public keys appear in the DNS
-- one has to take into account all kinds of timing issues, which are
-- discussed in Section 4.1. Section 4.2 and Section 4.3 deal with the
-- rollover, or supercession, of keys. Finally, Section 4.4 discusses
-- considerations on how parents deal with their children's public keys
-- in order to maintain chains of trust.
--
-- The typographic conventions used in this document are explained in
-- Appendix C.
--
-- Since this is a document with operational suggestions and there are
-- no protocol specifications, the RFC 2119 [7] language does not apply.
--
-- This document obsoletes RFC 2541 [12] to reflect the evolution of the
-- underlying DNSSEC protocol since then. Changes in the choice of
-- cryptographic algorithms, DNS record types and type names, and the
-- parent-child key and signature exchange demanded a major rewrite and
-- additional information and explanation.
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 3]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--1.1. The Use of the Term 'key'
--
-- It is assumed that the reader is familiar with the concept of
-- asymmetric keys on which DNSSEC is based (public key cryptography
-- [17]). Therefore, this document will use the term 'key' rather
-- loosely. Where it is written that 'a key is used to sign data' it is
-- assumed that the reader understands that it is the private part of
-- the key pair that is used for signing. It is also assumed that the
-- reader understands that the public part of the key pair is published
-- in the DNSKEY Resource Record and that it is the public part that is
-- used in key exchanges.
--
--1.2. Time Definitions
--
-- In this document, we will be using a number of time-related terms.
-- The following definitions apply:
--
-- o "Signature validity period" The period that a signature is valid.
-- It starts at the time specified in the signature inception field
-- of the RRSIG RR and ends at the time specified in the expiration
-- field of the RRSIG RR.
--
-- o "Signature publication period" Time after which a signature (made
-- with a specific key) is replaced with a new signature (made with
-- the same key). This replacement takes place by publishing the
-- relevant RRSIG in the master zone file. After one stops
-- publishing an RRSIG in a zone, it may take a while before the
-- RRSIG has expired from caches and has actually been removed from
-- the DNS.
--
-- o "Key effectivity period" The period during which a key pair is
-- expected to be effective. This period is defined as the time
-- between the first inception time stamp and the last expiration
-- date of any signature made with this key, regardless of any
-- discontinuity in the use of the key. The key effectivity period
-- can span multiple signature validity periods.
--
-- o "Maximum/Minimum Zone Time to Live (TTL)" The maximum or minimum
-- value of the TTLs from the complete set of RRs in a zone. Note
-- that the minimum TTL is not the same as the MINIMUM field in the
-- SOA RR. See [11] for more information.
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 4]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--2. Keeping the Chain of Trust Intact
--
-- Maintaining a valid chain of trust is important because broken chains
-- of trust will result in data being marked as Bogus (as defined in [4]
-- Section 5), which may cause entire (sub)domains to become invisible
-- to verifying clients. The administrators of secured zones have to
-- realize that their zone is, to verifying clients, part of a chain of
-- trust.
--
-- As mentioned in the introduction, the procedures herein are intended
-- to ensure that maintenance of zones, such as re-signing or key
-- rollovers, will be transparent to the verifying clients on the
-- Internet.
--
-- Administrators of secured zones will have to keep in mind that data
-- published on an authoritative primary server will not be immediately
-- seen by verifying clients; it may take some time for the data to be
-- transferred to other secondary authoritative nameservers and clients
-- may be fetching data from caching non-authoritative servers. In this
-- light, note that the time for a zone transfer from master to slave is
-- negligible when using NOTIFY [9] and incremental transfer (IXFR) [8].
-- It increases when full zone transfers (AXFR) are used in combination
-- with NOTIFY. It increases even more if you rely on full zone
-- transfers based on only the SOA timing parameters for refresh.
--
-- For the verifying clients, it is important that data from secured
-- zones can be used to build chains of trust regardless of whether the
-- data came directly from an authoritative server, a caching
-- nameserver, or some middle box. Only by carefully using the
-- available timing parameters can a zone administrator ensure that the
-- data necessary for verification can be obtained.
--
-- The responsibility for maintaining the chain of trust is shared by
-- administrators of secured zones in the chain of trust. This is most
-- obvious in the case of a 'key compromise' when a trade-off between
-- maintaining a valid chain of trust and replacing the compromised keys
-- as soon as possible must be made. Then zone administrators will have
-- to make a trade-off, between keeping the chain of trust intact --
-- thereby allowing for attacks with the compromised key -- or
-- deliberately breaking the chain of trust and making secured
-- subdomains invisible to security-aware resolvers. Also see Section
-- 4.3.
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 5]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--3. Keys Generation and Storage
--
-- This section describes a number of considerations with respect to the
-- security of keys. It deals with the generation, effectivity period,
-- size, and storage of private keys.
--
--3.1. Zone and Key Signing Keys
--
-- The DNSSEC validation protocol does not distinguish between different
-- types of DNSKEYs. All DNSKEYs can be used during the validation. In
-- practice, operators use Key Signing and Zone Signing Keys and use the
-- so-called Secure Entry Point (SEP) [3] flag to distinguish between
-- them during operations. The dynamics and considerations are
-- discussed below.
--
-- To make zone re-signing and key rollover procedures easier to
-- implement, it is possible to use one or more keys as Key Signing Keys
-- (KSKs). These keys will only sign the apex DNSKEY RRSet in a zone.
-- Other keys can be used to sign all the RRSets in a zone and are
-- referred to as Zone Signing Keys (ZSKs). In this document, we assume
-- that KSKs are the subset of keys that are used for key exchanges with
-- the parent and potentially for configuration as trusted anchors --
-- the SEP keys. In this document, we assume a one-to-one mapping
-- between KSK and SEP keys and we assume the SEP flag to be set on all
-- KSKs.
--
--3.1.1. Motivations for the KSK and ZSK Separation
--
-- Differentiating between the KSK and ZSK functions has several
-- advantages:
--
-- o No parent/child interaction is required when ZSKs are updated.
--
-- o The KSK can be made stronger (i.e., using more bits in the key
-- material). This has little operational impact since it is only
-- used to sign a small fraction of the zone data. Also, the KSK is
-- only used to verify the zone's key set, not for other RRSets in
-- the zone.
--
-- o As the KSK is only used to sign a key set, which is most probably
-- updated less frequently than other data in the zone, it can be
-- stored separately from and in a safer location than the ZSK.
--
-- o A KSK can have a longer key effectivity period.
--
-- For almost any method of key management and zone signing, the KSK is
-- used less frequently than the ZSK. Once a key set is signed with the
-- KSK, all the keys in the key set can be used as ZSKs. If a ZSK is
--
--
--
--Kolkman & Gieben Informational [Page 6]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- compromised, it can be simply dropped from the key set. The new key
-- set is then re-signed with the KSK.
--
-- Given the assumption that for KSKs the SEP flag is set, the KSK can
-- be distinguished from a ZSK by examining the flag field in the DNSKEY
-- RR. If the flag field is an odd number it is a KSK. If it is an
-- even number it is a ZSK.
--
-- The Zone Signing Key can be used to sign all the data in a zone on a
-- regular basis. When a Zone Signing Key is to be rolled, no
-- interaction with the parent is needed. This allows for signature
-- validity periods on the order of days.
--
-- The Key Signing Key is only to be used to sign the DNSKEY RRs in a
-- zone. If a Key Signing Key is to be rolled over, there will be
-- interactions with parties other than the zone administrator. These
-- can include the registry of the parent zone or administrators of
-- verifying resolvers that have the particular key configured as secure
-- entry points. Hence, the key effectivity period of these keys can
-- and should be made much longer. Although, given a long enough key,
-- the key effectivity period can be on the order of years, we suggest
-- planning for a key effectivity on the order of a few months so that a
-- key rollover remains an operational routine.
--
--3.1.2. KSKs for High-Level Zones
--
-- Higher-level zones are generally more sensitive than lower-level
-- zones. Anyone controlling or breaking the security of a zone thereby
-- obtains authority over all of its subdomains (except in the case of
-- resolvers that have locally configured the public key of a subdomain,
-- in which case this, and only this, subdomain wouldn't be affected by
-- the compromise of the parent zone). Therefore, extra care should be
-- taken with high-level zones, and strong keys should be used.
--
-- The root zone is the most critical of all zones. Someone controlling
-- or compromising the security of the root zone would control the
-- entire DNS namespace of all resolvers using that root zone (except in
-- the case of resolvers that have locally configured the public key of
-- a subdomain). Therefore, the utmost care must be taken in the
-- securing of the root zone. The strongest and most carefully handled
-- keys should be used. The root zone private key should always be kept
-- off-line.
--
-- Many resolvers will start at a root server for their access to and
-- authentication of DNS data. Securely updating the trust anchors in
-- an enormous population of resolvers around the world will be
-- extremely difficult.
--
--
--
--
--Kolkman & Gieben Informational [Page 7]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--3.2. Key Generation
--
-- Careful generation of all keys is a sometimes overlooked but
-- absolutely essential element in any cryptographically secure system.
-- The strongest algorithms used with the longest keys are still of no
-- use if an adversary can guess enough to lower the size of the likely
-- key space so that it can be exhaustively searched. Technical
-- suggestions for the generation of random keys will be found in RFC
-- 4086 [14]. One should carefully assess if the random number
-- generator used during key generation adheres to these suggestions.
--
-- Keys with a long effectivity period are particularly sensitive as
-- they will represent a more valuable target and be subject to attack
-- for a longer time than short-period keys. It is strongly recommended
-- that long-term key generation occur off-line in a manner isolated
-- from the network via an air gap or, at a minimum, high-level secure
-- hardware.
--
--3.3. Key Effectivity Period
--
-- For various reasons, keys in DNSSEC need to be changed once in a
-- while. The longer a key is in use, the greater the probability that
-- it will have been compromised through carelessness, accident,
-- espionage, or cryptanalysis. Furthermore, when key rollovers are too
-- rare an event, they will not become part of the operational habit and
-- there is risk that nobody on-site will remember the procedure for
-- rollover when the need is there.
--
-- From a purely operational perspective, a reasonable key effectivity
-- period for Key Signing Keys is 13 months, with the intent to replace
-- them after 12 months. An intended key effectivity period of a month
-- is reasonable for Zone Signing Keys.
--
-- For key sizes that match these effectivity periods, see Section 3.5.
--
-- As argued in Section 3.1.2, securely updating trust anchors will be
-- extremely difficult. On the other hand, the "operational habit"
-- argument does also apply to trust anchor reconfiguration. If a short
-- key effectivity period is used and the trust anchor configuration has
-- to be revisited on a regular basis, the odds that the configuration
-- tends to be forgotten is smaller. The trade-off is against a system
-- that is so dynamic that administrators of the validating clients will
-- not be able to follow the modifications.
--
-- Key effectivity periods can be made very short, as in a few minutes.
-- But when replacing keys one has to take the considerations from
-- Section 4.1 and Section 4.2 into account.
--
--
--
--
--Kolkman & Gieben Informational [Page 8]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--3.4. Key Algorithm
--
-- There are currently three different types of algorithms that can be
-- used in DNSSEC: RSA, DSA, and elliptic curve cryptography. The
-- latter is fairly new and has yet to be standardized for usage in
-- DNSSEC.
--
-- RSA has been developed in an open and transparent manner. As the
-- patent on RSA expired in 2000, its use is now also free.
--
-- DSA has been developed by the National Institute of Standards and
-- Technology (NIST). The creation of signatures takes roughly the same
-- time as with RSA, but is 10 to 40 times as slow for verification
-- [17].
--
-- We suggest the use of RSA/SHA-1 as the preferred algorithm for the
-- key. The current known attacks on RSA can be defeated by making your
-- key longer. As the MD5 hashing algorithm is showing cracks, we
-- recommend the usage of SHA-1.
--
-- At the time of publication, it is known that the SHA-1 hash has
-- cryptanalysis issues. There is work in progress on addressing these
-- issues. We recommend the use of public key algorithms based on
-- hashes stronger than SHA-1 (e.g., SHA-256), as soon as these
-- algorithms are available in protocol specifications (see [19] and
-- [20]) and implementations.
--
--3.5. Key Sizes
--
-- When choosing key sizes, zone administrators will need to take into
-- account how long a key will be used, how much data will be signed
-- during the key publication period (see Section 8.10 of [17]), and,
-- optionally, how large the key size of the parent is. As the chain of
-- trust really is "a chain", there is not much sense in making one of
-- the keys in the chain several times larger then the others. As
-- always, it's the weakest link that defines the strength of the entire
-- chain. Also see Section 3.1.1 for a discussion of how keys serving
-- different roles (ZSK vs. KSK) may need different key sizes.
--
-- Generating a key of the correct size is a difficult problem; RFC 3766
-- [13] tries to deal with that problem. The first part of the
-- selection procedure in Section 1 of the RFC states:
--
-- 1. Determine the attack resistance necessary to satisfy the
-- security requirements of the application. Do this by
-- estimating the minimum number of computer operations that the
-- attacker will be forced to do in order to compromise the
--
--
--
--
--Kolkman & Gieben Informational [Page 9]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- security of the system and then take the logarithm base two of
-- that number. Call that logarithm value "n".
--
-- A 1996 report recommended 90 bits as a good all-around choice
-- for system security. The 90 bit number should be increased by
-- about 2/3 bit/year, or about 96 bits in 2005.
--
-- [13] goes on to explain how this number "n" can be used to calculate
-- the key sizes in public key cryptography. This culminated in the
-- table given below (slightly modified for our purpose):
--
-- +-------------+-----------+--------------+
-- | System | | |
-- | requirement | Symmetric | RSA or DSA |
-- | for attack | key size | modulus size |
-- | resistance | (bits) | (bits) |
-- | (bits) | | |
-- +-------------+-----------+--------------+
-- | 70 | 70 | 947 |
-- | 80 | 80 | 1228 |
-- | 90 | 90 | 1553 |
-- | 100 | 100 | 1926 |
-- | 150 | 150 | 4575 |
-- | 200 | 200 | 8719 |
-- | 250 | 250 | 14596 |
-- +-------------+-----------+--------------+
--
-- The key sizes given are rather large. This is because these keys are
-- resilient against a trillionaire attacker. Assuming this rich
-- attacker will not attack your key and that the key is rolled over
-- once a year, we come to the following recommendations about KSK
-- sizes: 1024 bits for low-value domains, 1300 bits for medium-value
-- domains, and 2048 bits for high-value domains.
--
-- Whether a domain is of low, medium, or high value depends solely on
-- the views of the zone owner. One could, for instance, view leaf
-- nodes in the DNS as of low value, and top-level domains (TLDs) or the
-- root zone of high value. The suggested key sizes should be safe for
-- the next 5 years.
--
-- As ZSKs can be rolled over more easily (and thus more often), the key
-- sizes can be made smaller. But as said in the introduction of this
-- paragraph, making the ZSKs' key sizes too small (in relation to the
-- KSKs' sizes) doesn't make much sense. Try to limit the difference in
-- size to about 100 bits.
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 10]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- Note that nobody can see into the future and that these key sizes are
-- only provided here as a guide. Further information can be found in
-- [16] and Section 7.5 of [17]. It should be noted though that [16] is
-- already considered overly optimistic about what key sizes are
-- considered safe.
--
-- One final note concerning key sizes. Larger keys will increase the
-- sizes of the RRSIG and DNSKEY records and will therefore increase the
-- chance of DNS UDP packet overflow. Also, the time it takes to
-- validate and create RRSIGs increases with larger keys, so don't
-- needlessly double your key sizes.
--
--3.6. Private Key Storage
--
-- It is recommended that, where possible, zone private keys and the
-- zone file master copy that is to be signed be kept and used in off-
-- line, non-network-connected, physically secure machines only.
-- Periodically, an application can be run to add authentication to a
-- zone by adding RRSIG and NSEC RRs. Then the augmented file can be
-- transferred.
--
-- When relying on dynamic update to manage a signed zone [10], be aware
-- that at least one private key of the zone will have to reside on the
-- master server. This key is only as secure as the amount of exposure
-- the server receives to unknown clients and the security of the host.
-- Although not mandatory, one could administer the DNS in the following
-- way. The master that processes the dynamic updates is unavailable
-- from generic hosts on the Internet, it is not listed in the NS RR
-- set, although its name appears in the SOA RRs MNAME field. The
-- nameservers in the NS RRSet are able to receive zone updates through
-- NOTIFY, IXFR, AXFR, or an out-of-band distribution mechanism. This
-- approach is known as the "hidden master" setup.
--
-- The ideal situation is to have a one-way information flow to the
-- network to avoid the possibility of tampering from the network.
-- Keeping the zone master file on-line on the network and simply
-- cycling it through an off-line signer does not do this. The on-line
-- version could still be tampered with if the host it resides on is
-- compromised. For maximum security, the master copy of the zone file
-- should be off-net and should not be updated based on an unsecured
-- network mediated communication.
--
-- In general, keeping a zone file off-line will not be practical and
-- the machines on which zone files are maintained will be connected to
-- a network. Operators are advised to take security measures to shield
-- unauthorized access to the master copy.
--
--
--
--
--
--Kolkman & Gieben Informational [Page 11]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- For dynamically updated secured zones [10], both the master copy and
-- the private key that is used to update signatures on updated RRs will
-- need to be on-line.
--
--4. Signature Generation, Key Rollover, and Related Policies
--
--4.1. Time in DNSSEC
--
-- Without DNSSEC, all times in the DNS are relative. The SOA fields
-- REFRESH, RETRY, and EXPIRATION are timers used to determine the time
-- elapsed after a slave server synchronized with a master server. The
-- Time to Live (TTL) value and the SOA RR minimum TTL parameter [11]
-- are used to determine how long a forwarder should cache data after it
-- has been fetched from an authoritative server. By using a signature
-- validity period, DNSSEC introduces the notion of an absolute time in
-- the DNS. Signatures in DNSSEC have an expiration date after which
-- the signature is marked as invalid and the signed data is to be
-- considered Bogus.
--
--4.1.1. Time Considerations
--
-- Because of the expiration of signatures, one should consider the
-- following:
--
-- o We suggest the Maximum Zone TTL of your zone data to be a fraction
-- of your signature validity period.
--
-- If the TTL would be of similar order as the signature validity
-- period, then all RRSets fetched during the validity period
-- would be cached until the signature expiration time. Section
-- 7.1 of [4] suggests that "the resolver may use the time
-- remaining before expiration of the signature validity period of
-- a signed RRSet as an upper bound for the TTL". As a result,
-- query load on authoritative servers would peak at signature
-- expiration time, as this is also the time at which records
-- simultaneously expire from caches.
--
-- To avoid query load peaks, we suggest the TTL on all the RRs in
-- your zone to be at least a few times smaller than your
-- signature validity period.
--
-- o We suggest the signature publication period to end at least one
-- Maximum Zone TTL duration before the end of the signature validity
-- period.
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 12]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- Re-signing a zone shortly before the end of the signature
-- validity period may cause simultaneous expiration of data from
-- caches. This in turn may lead to peaks in the load on
-- authoritative servers.
--
-- o We suggest the Minimum Zone TTL to be long enough to both fetch
-- and verify all the RRs in the trust chain. In workshop
-- environments, it has been demonstrated [18] that a low TTL (under
-- 5 to 10 minutes) caused disruptions because of the following two
-- problems:
--
-- 1. During validation, some data may expire before the
-- validation is complete. The validator should be able to
-- keep all data until it is completed. This applies to all
-- RRs needed to complete the chain of trust: DSes, DNSKEYs,
-- RRSIGs, and the final answers, i.e., the RRSet that is
-- returned for the initial query.
--
-- 2. Frequent verification causes load on recursive nameservers.
-- Data at delegation points, DSes, DNSKEYs, and RRSIGs
-- benefit from caching. The TTL on those should be
-- relatively long.
--
-- o Slave servers will need to be able to fetch newly signed zones
-- well before the RRSIGs in the zone served by the slave server pass
-- their signature expiration time.
--
-- When a slave server is out of sync with its master and data in
-- a zone is signed by expired signatures, it may be better for
-- the slave server not to give out any answer.
--
-- Normally, a slave server that is not able to contact a master
-- server for an extended period will expire a zone. When that
-- happens, the server will respond differently to queries for
-- that zone. Some servers issue SERVFAIL, whereas others turn
-- off the 'AA' bit in the answers. The time of expiration is set
-- in the SOA record and is relative to the last successful
-- refresh between the master and the slave servers. There exists
-- no coupling between the signature expiration of RRSIGs in the
-- zone and the expire parameter in the SOA.
--
-- If the server serves a DNSSEC zone, then it may well happen
-- that the signatures expire well before the SOA expiration timer
-- counts down to zero. It is not possible to completely prevent
-- this from happening by tweaking the SOA parameters. However,
-- the effects can be minimized where the SOA expiration time is
-- equal to or shorter than the signature validity period. The
-- consequence of an authoritative server not being able to update
--
--
--
--Kolkman & Gieben Informational [Page 13]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- a zone, whilst that zone includes expired signatures, is that
-- non-secure resolvers will continue to be able to resolve data
-- served by the particular slave servers while security-aware
-- resolvers will experience problems because of answers being
-- marked as Bogus.
--
-- We suggest the SOA expiration timer being approximately one
-- third or one fourth of the signature validity period. It will
-- allow problems with transfers from the master server to be
-- noticed before the actual signature times out. We also suggest
-- that operators of nameservers that supply secondary services
-- develop 'watch dogs' to spot upcoming signature expirations in
-- zones they slave, and take appropriate action.
--
-- When determining the value for the expiration parameter one has
-- to take the following into account: What are the chances that
-- all my secondaries expire the zone? How quickly can I reach an
-- administrator of secondary servers to load a valid zone? These
-- questions are not DNSSEC specific but may influence the choice
-- of your signature validity intervals.
--
--4.2. Key Rollovers
--
-- A DNSSEC key cannot be used forever (see Section 3.3). So key
-- rollovers -- or supercessions, as they are sometimes called -- are a
-- fact of life when using DNSSEC. Zone administrators who are in the
-- process of rolling their keys have to take into account that data
-- published in previous versions of their zone still lives in caches.
-- When deploying DNSSEC, this becomes an important consideration;
-- ignoring data that may be in caches may lead to loss of service for
-- clients.
--
-- The most pressing example of this occurs when zone material signed
-- with an old key is being validated by a resolver that does not have
-- the old zone key cached. If the old key is no longer present in the
-- current zone, this validation fails, marking the data "Bogus".
-- Alternatively, an attempt could be made to validate data that is
-- signed with a new key against an old key that lives in a local cache,
-- also resulting in data being marked "Bogus".
--
--4.2.1. Zone Signing Key Rollovers
--
-- For "Zone Signing Key rollovers", there are two ways to make sure
-- that during the rollover data still cached can be verified with the
-- new key sets or newly generated signatures can be verified with the
-- keys still in caches. One schema, described in Section 4.2.1.2, uses
--
--
--
--
--
--Kolkman & Gieben Informational [Page 14]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- double signatures; the other uses key pre-publication (Section
-- 4.2.1.1). The pros, cons, and recommendations are described in
-- Section 4.2.1.3.
--
--4.2.1.1. Pre-Publish Key Rollover
--
-- This section shows how to perform a ZSK rollover without the need to
-- sign all the data in a zone twice -- the "pre-publish key rollover".
-- This method has advantages in the case of a key compromise. If the
-- old key is compromised, the new key has already been distributed in
-- the DNS. The zone administrator is then able to quickly switch to
-- the new key and remove the compromised key from the zone. Another
-- major advantage is that the zone size does not double, as is the case
-- with the double signature ZSK rollover. A small "how-to" for this
-- kind of rollover can be found in Appendix B.
--
-- Pre-publish key rollover involves four stages as follows:
--
-- ----------------------------------------------------------------
-- initial new DNSKEY new RRSIGs DNSKEY removal
-- ----------------------------------------------------------------
-- SOA0 SOA1 SOA2 SOA3
-- RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) RRSIG11(SOA3)
--
-- DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY1
-- DNSKEY10 DNSKEY10 DNSKEY10 DNSKEY11
-- DNSKEY11 DNSKEY11
-- RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY) RRSIG1 (DNSKEY)
-- RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY)
-- ----------------------------------------------------------------
--
-- Pre-Publish Key Rollover
--
-- initial: Initial version of the zone: DNSKEY 1 is the Key Signing
-- Key. DNSKEY 10 is used to sign all the data of the zone, the Zone
-- Signing Key.
--
-- new DNSKEY: DNSKEY 11 is introduced into the key set. Note that no
-- signatures are generated with this key yet, but this does not
-- secure against brute force attacks on the public key. The minimum
-- duration of this pre-roll phase is the time it takes for the data
-- to propagate to the authoritative servers plus TTL value of the
-- key set.
--
-- new RRSIGs: At the "new RRSIGs" stage (SOA serial 2), DNSKEY 11 is
-- used to sign the data in the zone exclusively (i.e., all the
-- signatures from DNSKEY 10 are removed from the zone). DNSKEY 10
-- remains published in the key set. This way data that was loaded
--
--
--
--Kolkman & Gieben Informational [Page 15]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- into caches from version 1 of the zone can still be verified with
-- key sets fetched from version 2 of the zone. The minimum time
-- that the key set including DNSKEY 10 is to be published is the
-- time that it takes for zone data from the previous version of the
-- zone to expire from old caches, i.e., the time it takes for this
-- zone to propagate to all authoritative servers plus the Maximum
-- Zone TTL value of any of the data in the previous version of the
-- zone.
--
-- DNSKEY removal: DNSKEY 10 is removed from the zone. The key set, now
-- only containing DNSKEY 1 and DNSKEY 11, is re-signed with the
-- DNSKEY 1.
--
-- The above scheme can be simplified by always publishing the "future"
-- key immediately after the rollover. The scheme would look as follows
-- (we show two rollovers); the future key is introduced in "new DNSKEY"
-- as DNSKEY 12 and again a newer one, numbered 13, in "new DNSKEY
-- (II)":
--
-- ----------------------------------------------------------------
-- initial new RRSIGs new DNSKEY
-- ----------------------------------------------------------------
-- SOA0 SOA1 SOA2
-- RRSIG10(SOA0) RRSIG11(SOA1) RRSIG11(SOA2)
--
-- DNSKEY1 DNSKEY1 DNSKEY1
-- DNSKEY10 DNSKEY10 DNSKEY11
-- DNSKEY11 DNSKEY11 DNSKEY12
-- RRSIG1(DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY)
-- RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY)
-- ----------------------------------------------------------------
--
-- ----------------------------------------------------------------
-- new RRSIGs (II) new DNSKEY (II)
-- ----------------------------------------------------------------
-- SOA3 SOA4
-- RRSIG12(SOA3) RRSIG12(SOA4)
--
-- DNSKEY1 DNSKEY1
-- DNSKEY11 DNSKEY12
-- DNSKEY12 DNSKEY13
-- RRSIG1(DNSKEY) RRSIG1(DNSKEY)
-- RRSIG12(DNSKEY) RRSIG12(DNSKEY)
-- ----------------------------------------------------------------
--
-- Pre-Publish Key Rollover, Showing Two Rollovers
--
--
--
--
--
--Kolkman & Gieben Informational [Page 16]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- Note that the key introduced in the "new DNSKEY" phase is not used
-- for production yet; the private key can thus be stored in a
-- physically secure manner and does not need to be 'fetched' every time
-- a zone needs to be signed.
--
--4.2.1.2. Double Signature Zone Signing Key Rollover
--
-- This section shows how to perform a ZSK key rollover using the double
-- zone data signature scheme, aptly named "double signature rollover".
--
-- During the "new DNSKEY" stage the new version of the zone file will
-- need to propagate to all authoritative servers and the data that
-- exists in (distant) caches will need to expire, requiring at least
-- the Maximum Zone TTL.
--
-- Double signature ZSK rollover involves three stages as follows:
--
-- ----------------------------------------------------------------
-- initial new DNSKEY DNSKEY removal
-- ----------------------------------------------------------------
-- SOA0 SOA1 SOA2
-- RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2)
-- RRSIG11(SOA1)
--
-- DNSKEY1 DNSKEY1 DNSKEY1
-- DNSKEY10 DNSKEY10 DNSKEY11
-- DNSKEY11
-- RRSIG1(DNSKEY) RRSIG1(DNSKEY) RRSIG1(DNSKEY)
-- RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY)
-- RRSIG11(DNSKEY)
-- ----------------------------------------------------------------
--
-- Double Signature Zone Signing Key Rollover
--
-- initial: Initial Version of the zone: DNSKEY 1 is the Key Signing
-- Key. DNSKEY 10 is used to sign all the data of the zone, the Zone
-- Signing Key.
--
-- new DNSKEY: At the "New DNSKEY" stage (SOA serial 1) DNSKEY 11 is
-- introduced into the key set and all the data in the zone is signed
-- with DNSKEY 10 and DNSKEY 11. The rollover period will need to
-- continue until all data from version 0 of the zone has expired
-- from remote caches. This will take at least the Maximum Zone TTL
-- of version 0 of the zone.
--
-- DNSKEY removal: DNSKEY 10 is removed from the zone. All the
-- signatures from DNSKEY 10 are removed from the zone. The key set,
-- now only containing DNSKEY 11, is re-signed with DNSKEY 1.
--
--
--
--Kolkman & Gieben Informational [Page 17]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- At every instance, RRSIGs from the previous version of the zone can
-- be verified with the DNSKEY RRSet from the current version and the
-- other way around. The data from the current version can be verified
-- with the data from the previous version of the zone. The duration of
-- the "new DNSKEY" phase and the period between rollovers should be at
-- least the Maximum Zone TTL.
--
-- Making sure that the "new DNSKEY" phase lasts until the signature
-- expiration time of the data in initial version of the zone is
-- recommended. This way all caches are cleared of the old signatures.
-- However, this duration could be considerably longer than the Maximum
-- Zone TTL, making the rollover a lengthy procedure.
--
-- Note that in this example we assumed that the zone was not modified
-- during the rollover. New data can be introduced in the zone as long
-- as it is signed with both keys.
--
--4.2.1.3. Pros and Cons of the Schemes
--
-- Pre-publish key rollover: This rollover does not involve signing the
-- zone data twice. Instead, before the actual rollover, the new key
-- is published in the key set and thus is available for
-- cryptanalysis attacks. A small disadvantage is that this process
-- requires four steps. Also the pre-publish scheme involves more
-- parental work when used for KSK rollovers as explained in Section
-- 4.2.3.
--
-- Double signature ZSK rollover: The drawback of this signing scheme is
-- that during the rollover the number of signatures in your zone
-- doubles; this may be prohibitive if you have very big zones. An
-- advantage is that it only requires three steps.
--
--4.2.2. Key Signing Key Rollovers
--
-- For the rollover of a Key Signing Key, the same considerations as for
-- the rollover of a Zone Signing Key apply. However, we can use a
-- double signature scheme to guarantee that old data (only the apex key
-- set) in caches can be verified with a new key set and vice versa.
-- Since only the key set is signed with a KSK, zone size considerations
-- do not apply.
--
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 18]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- --------------------------------------------------------------------
-- initial new DNSKEY DS change DNSKEY removal
-- --------------------------------------------------------------------
-- Parent:
-- SOA0 --------> SOA1 -------->
-- RRSIGpar(SOA0) --------> RRSIGpar(SOA1) -------->
-- DS1 --------> DS2 -------->
-- RRSIGpar(DS) --------> RRSIGpar(DS) -------->
--
--
-- Child:
-- SOA0 SOA1 --------> SOA2
-- RRSIG10(SOA0) RRSIG10(SOA1) --------> RRSIG10(SOA2)
-- -------->
-- DNSKEY1 DNSKEY1 --------> DNSKEY2
-- DNSKEY2 -------->
-- DNSKEY10 DNSKEY10 --------> DNSKEY10
-- RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) --------> RRSIG2 (DNSKEY)
-- RRSIG2 (DNSKEY) -------->
-- RRSIG10(DNSKEY) RRSIG10(DNSKEY) --------> RRSIG10(DNSKEY)
-- --------------------------------------------------------------------
--
-- Stages of Deployment for a Double Signature Key Signing Key Rollover
--
-- initial: Initial version of the zone. The parental DS points to
-- DNSKEY1. Before the rollover starts, the child will have to
-- verify what the TTL is of the DS RR that points to DNSKEY1 -- it
-- is needed during the rollover and we refer to the value as TTL_DS.
--
-- new DNSKEY: During the "new DNSKEY" phase, the zone administrator
-- generates a second KSK, DNSKEY2. The key is provided to the
-- parent, and the child will have to wait until a new DS RR has been
-- generated that points to DNSKEY2. After that DS RR has been
-- published on all servers authoritative for the parent's zone, the
-- zone administrator has to wait at least TTL_DS to make sure that
-- the old DS RR has expired from caches.
--
-- DS change: The parent replaces DS1 with DS2.
--
-- DNSKEY removal: DNSKEY1 has been removed.
--
-- The scenario above puts the responsibility for maintaining a valid
-- chain of trust with the child. It also is based on the premise that
-- the parent only has one DS RR (per algorithm) per zone. An
-- alternative mechanism has been considered. Using an established
-- trust relation, the interaction can be performed in-band, and the
-- removal of the keys by the child can possibly be signaled by the
-- parent. In this mechanism, there are periods where there are two DS
--
--
--
--Kolkman & Gieben Informational [Page 19]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- RRs at the parent. Since at the moment of writing the protocol for
-- this interaction has not been developed, further discussion is out of
-- scope for this document.
--
--4.2.3. Difference Between ZSK and KSK Rollovers
--
-- Note that KSK rollovers and ZSK rollovers are different in the sense
-- that a KSK rollover requires interaction with the parent (and
-- possibly replacing of trust anchors) and the ensuing delay while
-- waiting for it.
--
-- A zone key rollover can be handled in two different ways: pre-publish
-- (Section 4.2.1.1) and double signature (Section 4.2.1.2).
--
-- As the KSK is used to validate the key set and because the KSK is not
-- changed during a ZSK rollover, a cache is able to validate the new
-- key set of the zone. The pre-publish method would also work for a
-- KSK rollover. The records that are to be pre-published are the
-- parental DS RRs. The pre-publish method has some drawbacks for KSKs.
-- We first describe the rollover scheme and then indicate these
-- drawbacks.
--
-- --------------------------------------------------------------------
-- initial new DS new DNSKEY DS/DNSKEY removal
-- --------------------------------------------------------------------
-- Parent:
-- SOA0 SOA1 --------> SOA2
-- RRSIGpar(SOA0) RRSIGpar(SOA1) --------> RRSIGpar(SOA2)
-- DS1 DS1 --------> DS2
-- DS2 -------->
-- RRSIGpar(DS) RRSIGpar(DS) --------> RRSIGpar(DS)
--
--
-- Child:
-- SOA0 --------> SOA1 SOA1
-- RRSIG10(SOA0) --------> RRSIG10(SOA1) RRSIG10(SOA1)
-- -------->
-- DNSKEY1 --------> DNSKEY2 DNSKEY2
-- -------->
-- DNSKEY10 --------> DNSKEY10 DNSKEY10
-- RRSIG1 (DNSKEY) --------> RRSIG2(DNSKEY) RRSIG2 (DNSKEY)
-- RRSIG10(DNSKEY) --------> RRSIG10(DNSKEY) RRSIG10(DNSKEY)
-- --------------------------------------------------------------------
--
-- Stages of Deployment for a Pre-Publish Key Signing Key Rollover
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 20]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- When the child zone wants to roll, it notifies the parent during the
-- "new DS" phase and submits the new key (or the corresponding DS) to
-- the parent. The parent publishes DS1 and DS2, pointing to DNSKEY1
-- and DNSKEY2, respectively. During the rollover ("new DNSKEY" phase),
-- which can take place as soon as the new DS set propagated through the
-- DNS, the child replaces DNSKEY1 with DNSKEY2. Immediately after that
-- ("DS/DNSKEY removal" phase), it can notify the parent that the old DS
-- record can be deleted.
--
-- The drawbacks of this scheme are that during the "new DS" phase the
-- parent cannot verify the match between the DS2 RR and DNSKEY2 using
-- the DNS -- as DNSKEY2 is not yet published. Besides, we introduce a
-- "security lame" key (see Section 4.4.3). Finally, the child-parent
-- interaction consists of two steps. The "double signature" method
-- only needs one interaction.
--
--4.2.4. Automated Key Rollovers
--
-- As keys must be renewed periodically, there is some motivation to
-- automate the rollover process. Consider the following:
--
-- o ZSK rollovers are easy to automate as only the child zone is
-- involved.
--
-- o A KSK rollover needs interaction between parent and child. Data
-- exchange is needed to provide the new keys to the parent;
-- consequently, this data must be authenticated and integrity must
-- be guaranteed in order to avoid attacks on the rollover.
--
--4.3. Planning for Emergency Key Rollover
--
-- This section deals with preparation for a possible key compromise.
-- Our advice is to have a documented procedure ready for when a key
-- compromise is suspected or confirmed.
--
-- When the private material of one of your keys is compromised it can
-- be used for as long as a valid trust chain exists. A trust chain
-- remains intact for
--
-- o as long as a signature over the compromised key in the trust chain
-- is valid,
--
-- o as long as a parental DS RR (and signature) points to the
-- compromised key,
--
-- o as long as the key is anchored in a resolver and is used as a
-- starting point for validation (this is generally the hardest to
-- update).
--
--
--
--Kolkman & Gieben Informational [Page 21]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- While a trust chain to your compromised key exists, your namespace is
-- vulnerable to abuse by anyone who has obtained illegitimate
-- possession of the key. Zone operators have to make a trade-off if
-- the abuse of the compromised key is worse than having data in caches
-- that cannot be validated. If the zone operator chooses to break the
-- trust chain to the compromised key, data in caches signed with this
-- key cannot be validated. However, if the zone administrator chooses
-- to take the path of a regular rollover, the malicious key holder can
-- spoof data so that it appears to be valid.
--
--4.3.1. KSK Compromise
--
-- A zone containing a DNSKEY RRSet with a compromised KSK is vulnerable
-- as long as the compromised KSK is configured as trust anchor or a
-- parental DS points to it.
--
-- A compromised KSK can be used to sign the key set of an attacker's
-- zone. That zone could be used to poison the DNS.
--
-- Therefore, when the KSK has been compromised, the trust anchor or the
-- parental DS should be replaced as soon as possible. It is local
-- policy whether to break the trust chain during the emergency
-- rollover. The trust chain would be broken when the compromised KSK
-- is removed from the child's zone while the parent still has a DS
-- pointing to the compromised KSK (the assumption is that there is only
-- one DS at the parent. If there are multiple DSes this does not apply
-- -- however the chain of trust of this particular key is broken).
--
-- Note that an attacker's zone still uses the compromised KSK and the
-- presence of a parental DS would cause the data in this zone to appear
-- as valid. Removing the compromised key would cause the attacker's
-- zone to appear as valid and the child's zone as Bogus. Therefore, we
-- advise not to remove the KSK before the parent has a DS to a new KSK
-- in place.
--
--4.3.1.1. Keeping the Chain of Trust Intact
--
-- If we follow this advice, the timing of the replacement of the KSK is
-- somewhat critical. The goal is to remove the compromised KSK as soon
-- as the new DS RR is available at the parent. And also make sure that
-- the signature made with a new KSK over the key set with the
-- compromised KSK in it expires just after the new DS appears at the
-- parent, thus removing the old cruft in one swoop.
--
-- The procedure is as follows:
--
-- 1. Introduce a new KSK into the key set, keep the compromised KSK in
-- the key set.
--
--
--
--Kolkman & Gieben Informational [Page 22]
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--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- 2. Sign the key set, with a short validity period. The validity
-- period should expire shortly after the DS is expected to appear
-- in the parent and the old DSes have expired from caches.
--
-- 3. Upload the DS for this new key to the parent.
--
-- 4. Follow the procedure of the regular KSK rollover: Wait for the DS
-- to appear in the authoritative servers and then wait as long as
-- the TTL of the old DS RRs. If necessary re-sign the DNSKEY RRSet
-- and modify/extend the expiration time.
--
-- 5. Remove the compromised DNSKEY RR from the zone and re-sign the
-- key set using your "normal" validity interval.
--
-- An additional danger of a key compromise is that the compromised key
-- could be used to facilitate a legitimate DNSKEY/DS rollover and/or
-- nameserver changes at the parent. When that happens, the domain may
-- be in dispute. An authenticated out-of-band and secure notify
-- mechanism to contact a parent is needed in this case.
--
-- Note that this is only a problem when the DNSKEY and or DS records
-- are used for authentication at the parent.
--
--4.3.1.2. Breaking the Chain of Trust
--
-- There are two methods to break the chain of trust. The first method
-- causes the child zone to appear 'Bogus' to validating resolvers. The
-- other causes the child zone to appear 'insecure'. These are
-- described below.
--
-- In the method that causes the child zone to appear 'Bogus' to
-- validating resolvers, the child zone replaces the current KSK with a
-- new one and re-signs the key set. Next it sends the DS of the new
-- key to the parent. Only after the parent has placed the new DS in
-- the zone is the child's chain of trust repaired.
--
-- An alternative method of breaking the chain of trust is by removing
-- the DS RRs from the parent zone altogether. As a result, the child
-- zone would become insecure.
--
--4.3.2. ZSK Compromise
--
-- Primarily because there is no parental interaction required when a
-- ZSK is compromised, the situation is less severe than with a KSK
-- compromise. The zone must still be re-signed with a new ZSK as soon
-- as possible. As this is a local operation and requires no
-- communication between the parent and child, this can be achieved
-- fairly quickly. However, one has to take into account that just as
--
--
--
--Kolkman & Gieben Informational [Page 23]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- with a normal rollover the immediate disappearance of the old
-- compromised key may lead to verification problems. Also note that as
-- long as the RRSIG over the compromised ZSK is not expired the zone
-- may be still at risk.
--
--4.3.3. Compromises of Keys Anchored in Resolvers
--
-- A key can also be pre-configured in resolvers. For instance, if
-- DNSSEC is successfully deployed the root key may be pre-configured in
-- most security aware resolvers.
--
-- If trust-anchor keys are compromised, the resolvers using these keys
-- should be notified of this fact. Zone administrators may consider
-- setting up a mailing list to communicate the fact that a SEP key is
-- about to be rolled over. This communication will of course need to
-- be authenticated, e.g., by using digital signatures.
--
-- End-users faced with the task of updating an anchored key should
-- always validate the new key. New keys should be authenticated out-
-- of-band, for example, through the use of an announcement website that
-- is secured using secure sockets (TLS) [21].
--
--4.4. Parental Policies
--
--4.4.1. Initial Key Exchanges and Parental Policies Considerations
--
-- The initial key exchange is always subject to the policies set by the
-- parent. When designing a key exchange policy one should take into
-- account that the authentication and authorization mechanisms used
-- during a key exchange should be as strong as the authentication and
-- authorization mechanisms used for the exchange of delegation
-- information between parent and child. That is, there is no implicit
-- need in DNSSEC to make the authentication process stronger than it
-- was in DNS.
--
-- Using the DNS itself as the source for the actual DNSKEY material,
-- with an out-of-band check on the validity of the DNSKEY, has the
-- benefit that it reduces the chances of user error. A DNSKEY query
-- tool can make use of the SEP bit [3] to select the proper key from a
-- DNSSEC key set, thereby reducing the chance that the wrong DNSKEY is
-- sent. It can validate the self-signature over a key; thereby
-- verifying the ownership of the private key material. Fetching the
-- DNSKEY from the DNS ensures that the chain of trust remains intact
-- once the parent publishes the DS RR indicating the child is secure.
--
-- Note: the out-of-band verification is still needed when the key
-- material is fetched via the DNS. The parent can never be sure
-- whether or not the DNSKEY RRs have been spoofed.
--
--
--
--Kolkman & Gieben Informational [Page 24]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--4.4.2. Storing Keys or Hashes?
--
-- When designing a registry system one should consider which of the
-- DNSKEYs and/or the corresponding DSes to store. Since a child zone
-- might wish to have a DS published using a message digest algorithm
-- not yet understood by the registry, the registry can't count on being
-- able to generate the DS record from a raw DNSKEY. Thus, we recommend
-- that registry systems at least support storing DS records.
--
-- It may also be useful to store DNSKEYs, since having them may help
-- during troubleshooting and, as long as the child's chosen message
-- digest is supported, the overhead of generating DS records from them
-- is minimal. Having an out-of-band mechanism, such as a registry
-- directory (e.g., Whois), to find out which keys are used to generate
-- DS Resource Records for specific owners and/or zones may also help
-- with troubleshooting.
--
-- The storage considerations also relate to the design of the customer
-- interface and the method by which data is transferred between
-- registrant and registry; Will the child zone administrator be able to
-- upload DS RRs with unknown hash algorithms or does the interface only
-- allow DNSKEYs? In the registry-registrar model, one can use the
-- DNSSEC extensions to the Extensible Provisioning Protocol (EPP) [15],
-- which allows transfer of DS RRs and optionally DNSKEY RRs.
--
--4.4.3. Security Lameness
--
-- Security lameness is defined as what happens when a parent has a DS
-- RR pointing to a non-existing DNSKEY RR. When this happens, the
-- child's zone may be marked "Bogus" by verifying DNS clients.
--
-- As part of a comprehensive delegation check, the parent could, at key
-- exchange time, verify that the child's key is actually configured in
-- the DNS. However, if a parent does not understand the hashing
-- algorithm used by child, the parental checks are limited to only
-- comparing the key id.
--
-- Child zones should be very careful in removing DNSKEY material,
-- specifically SEP keys, for which a DS RR exists.
--
-- Once a zone is "security lame", a fix (e.g., removing a DS RR) will
-- take time to propagate through the DNS.
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 25]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--4.4.4. DS Signature Validity Period
--
-- Since the DS can be replayed as long as it has a valid signature, a
-- short signature validity period over the DS minimizes the time a
-- child is vulnerable in the case of a compromise of the child's
-- KSK(s). A signature validity period that is too short introduces the
-- possibility that a zone is marked "Bogus" in case of a configuration
-- error in the signer. There may not be enough time to fix the
-- problems before signatures expire. Something as mundane as operator
-- unavailability during weekends shows the need for DS signature
-- validity periods longer than 2 days. We recommend an absolute
-- minimum for a DS signature validity period of a few days.
--
-- The maximum signature validity period of the DS record depends on how
-- long child zones are willing to be vulnerable after a key compromise.
-- On the other hand, shortening the DS signature validity interval
-- increases the operational risk for the parent. Therefore, the parent
-- may have policy to use a signature validity interval that is
-- considerably longer than the child would hope for.
--
-- A compromise between the operational constraints of the parent and
-- minimizing damage for the child may result in a DS signature validity
-- period somewhere between a week and months.
--
-- In addition to the signature validity period, which sets a lower
-- bound on the number of times the zone owner will need to sign the
-- zone data and which sets an upper bound to the time a child is
-- vulnerable after key compromise, there is the TTL value on the DS
-- RRs. Shortening the TTL means that the authoritative servers will
-- see more queries. But on the other hand, a short TTL lowers the
-- persistence of DS RRSets in caches thereby increasing the speed with
-- which updated DS RRSets propagate through the DNS.
--
--5. Security Considerations
--
-- DNSSEC adds data integrity to the DNS. This document tries to assess
-- the operational considerations to maintain a stable and secure DNSSEC
-- service. Not taking into account the 'data propagation' properties
-- in the DNS will cause validation failures and may make secured zones
-- unavailable to security-aware resolvers.
--
--6. Acknowledgments
--
-- Most of the ideas in this document were the result of collective
-- efforts during workshops, discussions, and tryouts.
--
-- At the risk of forgetting individuals who were the original
-- contributors of the ideas, we would like to acknowledge people who
--
--
--
--Kolkman & Gieben Informational [Page 26]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- were actively involved in the compilation of this document. In
-- random order: Rip Loomis, Olafur Gudmundsson, Wesley Griffin, Michael
-- Richardson, Scott Rose, Rick van Rein, Tim McGinnis, Gilles Guette
-- Olivier Courtay, Sam Weiler, Jelte Jansen, Niall O'Reilly, Holger
-- Zuleger, Ed Lewis, Hilarie Orman, Marcos Sanz, and Peter Koch.
--
-- Some material in this document has been copied from RFC 2541 [12].
--
-- Mike StJohns designed the key exchange between parent and child
-- mentioned in the last paragraph of Section 4.2.2
--
-- Section 4.2.4 was supplied by G. Guette and O. Courtay.
--
-- Emma Bretherick, Adrian Bedford, and Lindy Foster corrected many of
-- the spelling and style issues.
--
-- Kolkman and Gieben take the blame for introducing all miscakes (sic).
--
-- While working on this document, Kolkman was employed by the RIPE NCC
-- and Gieben was employed by NLnet Labs.
--
--7. References
--
--7.1. Normative References
--
-- [1] Mockapetris, P., "Domain names - concepts and facilities", STD
-- 13, RFC 1034, November 1987.
--
-- [2] Mockapetris, P., "Domain names - implementation and
-- specification", STD 13, RFC 1035, November 1987.
--
-- [3] Kolkman, O., Schlyter, J., and E. Lewis, "Domain Name System
-- KEY (DNSKEY) Resource Record (RR) Secure Entry Point (SEP)
-- Flag", RFC 3757, May 2004.
--
-- [4] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "DNS Security Introduction and Requirements", RFC 4033, March
-- 2005.
--
-- [5] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Resource Records for the DNS Security Extensions", RFC 4034,
-- March 2005.
--
-- [6] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
-- "Protocol Modifications for the DNS Security Extensions", RFC
-- 4035, March 2005.
--
--
--
--
--
--Kolkman & Gieben Informational [Page 27]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--7.2. Informative References
--
-- [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
-- Levels", BCP 14, RFC 2119, March 1997.
--
-- [8] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, August
-- 1996.
--
-- [9] Vixie, P., "A Mechanism for Prompt Notification of Zone Changes
-- (DNS NOTIFY)", RFC 1996, August 1996.
--
-- [10] Wellington, B., "Secure Domain Name System (DNS) Dynamic
-- Update", RFC 3007, November 2000.
--
-- [11] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)",
-- RFC 2308, March 1998.
--
-- [12] Eastlake, D., "DNS Security Operational Considerations", RFC
-- 2541, March 1999.
--
-- [13] Orman, H. and P. Hoffman, "Determining Strengths For Public
-- Keys Used For Exchanging Symmetric Keys", BCP 86, RFC 3766,
-- April 2004.
--
-- [14] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
-- Requirements for Security", BCP 106, RFC 4086, June 2005.
--
-- [15] Hollenbeck, S., "Domain Name System (DNS) Security Extensions
-- Mapping for the Extensible Provisioning Protocol (EPP)", RFC
-- 4310, December 2005.
--
-- [16] Lenstra, A. and E. Verheul, "Selecting Cryptographic Key
-- Sizes", The Journal of Cryptology 14 (255-293), 2001.
--
-- [17] Schneier, B., "Applied Cryptography: Protocols, Algorithms, and
-- Source Code in C", ISBN (hardcover) 0-471-12845-7, ISBN
-- (paperback) 0-471-59756-2, Published by John Wiley & Sons Inc.,
-- 1996.
--
-- [18] Rose, S., "NIST DNSSEC workshop notes", June 2001.
--
-- [19] Jansen, J., "Use of RSA/SHA-256 DNSKEY and RRSIG Resource
-- Records in DNSSEC", Work in Progress, January 2006.
--
-- [20] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer (DS)
-- Resource Records (RRs)", RFC 4509, May 2006.
--
--
--
--
--
--Kolkman & Gieben Informational [Page 28]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- [21] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and
-- T. Wright, "Transport Layer Security (TLS) Extensions", RFC
-- 4366, April 2006.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 29]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--Appendix A. Terminology
--
-- In this document, there is some jargon used that is defined in other
-- documents. In most cases, we have not copied the text from the
-- documents defining the terms but have given a more elaborate
-- explanation of the meaning. Note that these explanations should not
-- be seen as authoritative.
--
-- Anchored key: A DNSKEY configured in resolvers around the globe.
-- This key is hard to update, hence the term anchored.
--
-- Bogus: Also see Section 5 of [4]. An RRSet in DNSSEC is marked
-- "Bogus" when a signature of an RRSet does not validate against a
-- DNSKEY.
--
-- Key Signing Key or KSK: A Key Signing Key (KSK) is a key that is used
-- exclusively for signing the apex key set. The fact that a key is
-- a KSK is only relevant to the signing tool.
--
-- Key size: The term 'key size' can be substituted by 'modulus size'
-- throughout the document. It is mathematically more correct to use
-- modulus size, but as this is a document directed at operators we
-- feel more at ease with the term key size.
--
-- Private and public keys: DNSSEC secures the DNS through the use of
-- public key cryptography. Public key cryptography is based on the
-- existence of two (mathematically related) keys, a public key and a
-- private key. The public keys are published in the DNS by use of
-- the DNSKEY Resource Record (DNSKEY RR). Private keys should
-- remain private.
--
-- Key rollover: A key rollover (also called key supercession in some
-- environments) is the act of replacing one key pair with another at
-- the end of a key effectivity period.
--
-- Secure Entry Point (SEP) key: A KSK that has a parental DS record
-- pointing to it or is configured as a trust anchor. Although not
-- required by the protocol, we recommend that the SEP flag [3] is
-- set on these keys.
--
-- Self-signature: This only applies to signatures over DNSKEYs; a
-- signature made with DNSKEY x, over DNSKEY x is called a self-
-- signature. Note: without further information, self-signatures
-- convey no trust. They are useful to check the authenticity of the
-- DNSKEY, i.e., they can be used as a hash.
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 30]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- Singing the zone file: The term used for the event where an
-- administrator joyfully signs its zone file while producing melodic
-- sound patterns.
--
-- Signer: The system that has access to the private key material and
-- signs the Resource Record sets in a zone. A signer may be
-- configured to sign only parts of the zone, e.g., only those RRSets
-- for which existing signatures are about to expire.
--
-- Zone Signing Key (ZSK): A key that is used for signing all data in a
-- zone. The fact that a key is a ZSK is only relevant to the
-- signing tool.
--
-- Zone administrator: The 'role' that is responsible for signing a zone
-- and publishing it on the primary authoritative server.
--
--Appendix B. Zone Signing Key Rollover How-To
--
-- Using the pre-published signature scheme and the most conservative
-- method to assure oneself that data does not live in caches, here
-- follows the "how-to".
--
-- Step 0: The preparation: Create two keys and publish both in your key
-- set. Mark one of the keys "active" and the other "published".
-- Use the "active" key for signing your zone data. Store the
-- private part of the "published" key, preferably off-line. The
-- protocol does not provide for attributes to mark a key as active
-- or published. This is something you have to do on your own,
-- through the use of a notebook or key management tool.
--
-- Step 1: Determine expiration: At the beginning of the rollover make a
-- note of the highest expiration time of signatures in your zone
-- file created with the current key marked as active. Wait until
-- the expiration time marked in Step 1 has passed.
--
-- Step 2: Then start using the key that was marked "published" to sign
-- your data (i.e., mark it "active"). Stop using the key that was
-- marked "active"; mark it "rolled".
--
-- Step 3: It is safe to engage in a new rollover (Step 1) after at
-- least one signature validity period.
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 31]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--Appendix C. Typographic Conventions
--
-- The following typographic conventions are used in this document:
--
-- Key notation: A key is denoted by DNSKEYx, where x is a number or an
-- identifier, x could be thought of as the key id.
--
-- RRSet notations: RRs are only denoted by the type. All other
-- information -- owner, class, rdata, and TTL--is left out. Thus:
-- "example.com 3600 IN A 192.0.2.1" is reduced to "A". RRSets are a
-- list of RRs. A example of this would be "A1, A2", specifying the
-- RRSet containing two "A" records. This could again be abbreviated to
-- just "A".
--
-- Signature notation: Signatures are denoted as RRSIGx(RRSet), which
-- means that RRSet is signed with DNSKEYx.
--
-- Zone representation: Using the above notation we have simplified the
-- representation of a signed zone by leaving out all unnecessary
-- details such as the names and by representing all data by "SOAx"
--
-- SOA representation: SOAs are represented as SOAx, where x is the
-- serial number.
--
-- Using this notation the following signed zone:
--
-- example.net. 86400 IN SOA ns.example.net. bert.example.net. (
-- 2006022100 ; serial
-- 86400 ; refresh ( 24 hours)
-- 7200 ; retry ( 2 hours)
-- 3600000 ; expire (1000 hours)
-- 28800 ) ; minimum ( 8 hours)
-- 86400 RRSIG SOA 5 2 86400 20130522213204 (
-- 20130422213204 14 example.net.
-- cmL62SI6iAX46xGNQAdQ... )
-- 86400 NS a.iana-servers.net.
-- 86400 NS b.iana-servers.net.
-- 86400 RRSIG NS 5 2 86400 20130507213204 (
-- 20130407213204 14 example.net.
-- SO5epiJei19AjXoUpFnQ ... )
-- 86400 DNSKEY 256 3 5 (
-- EtRB9MP5/AvOuVO0I8XDxy0... ) ; id = 14
-- 86400 DNSKEY 257 3 5 (
-- gsPW/Yy19GzYIY+Gnr8HABU... ) ; id = 15
-- 86400 RRSIG DNSKEY 5 2 86400 20130522213204 (
-- 20130422213204 14 example.net.
-- J4zCe8QX4tXVGjV4e1r9... )
--
--
--
--
--Kolkman & Gieben Informational [Page 32]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
-- 86400 RRSIG DNSKEY 5 2 86400 20130522213204 (
-- 20130422213204 15 example.net.
-- keVDCOpsSeDReyV6O... )
-- 86400 RRSIG NSEC 5 2 86400 20130507213204 (
-- 20130407213204 14 example.net.
-- obj3HEp1GjnmhRjX... )
-- a.example.net. 86400 IN TXT "A label"
-- 86400 RRSIG TXT 5 3 86400 20130507213204 (
-- 20130407213204 14 example.net.
-- IkDMlRdYLmXH7QJnuF3v... )
-- 86400 NSEC b.example.com. TXT RRSIG NSEC
-- 86400 RRSIG NSEC 5 3 86400 20130507213204 (
-- 20130407213204 14 example.net.
-- bZMjoZ3bHjnEz0nIsPMM... )
-- ...
--
-- is reduced to the following representation:
--
-- SOA2006022100
-- RRSIG14(SOA2006022100)
-- DNSKEY14
-- DNSKEY15
--
-- RRSIG14(KEY)
-- RRSIG15(KEY)
--
-- The rest of the zone data has the same signature as the SOA record,
-- i.e., an RRSIG created with DNSKEY 14.
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 33]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--Authors' Addresses
--
-- Olaf M. Kolkman
-- NLnet Labs
-- Kruislaan 419
-- Amsterdam 1098 VA
-- The Netherlands
--
-- EMail: olaf@nlnetlabs.nl
-- URI: http://www.nlnetlabs.nl
--
--
-- R. (Miek) Gieben
--
-- EMail: miek@miek.nl
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 34]
--\f
--RFC 4641 DNSSEC Operational Practices September 2006
--
--
--Full Copyright Statement
--
-- Copyright (C) The Internet Society (2006).
--
-- This document is subject to the rights, licenses and restrictions
-- contained in BCP 78, and except as set forth therein, the authors
-- retain all their rights.
--
-- This document and the information contained herein are provided on an
-- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
-- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
-- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
-- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
-- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
-- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
--
--Intellectual Property
--
-- The IETF takes no position regarding the validity or scope of any
-- Intellectual Property Rights or other rights that might be claimed to
-- pertain to the implementation or use of the technology described in
-- this document or the extent to which any license under such rights
-- might or might not be available; nor does it represent that it has
-- made any independent effort to identify any such rights. Information
-- on the procedures with respect to rights in RFC documents can be
-- found in BCP 78 and BCP 79.
--
-- Copies of IPR disclosures made to the IETF Secretariat and any
-- assurances of licenses to be made available, or the result of an
-- attempt made to obtain a general license or permission for the use of
-- such proprietary rights by implementers or users of this
-- specification can be obtained from the IETF on-line IPR repository at
-- http://www.ietf.org/ipr.
--
-- The IETF invites any interested party to bring to its attention any
-- copyrights, patents or patent applications, or other proprietary
-- rights that may cover technology that may be required to implement
-- this standard. Please address the information to the IETF at
-- ietf-ipr@ietf.org.
--
--Acknowledgement
--
-- Funding for the RFC Editor function is provided by the IETF
-- Administrative Support Activity (IASA).
--
--
--
--
--
--
--
--Kolkman & Gieben Informational [Page 35]
--\f
projects / thirdparty / bind9.git / commitdiff
