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- DNSEXT Working Group Olafur Gudmundsson
- INTERNET-DRAFT November 2001
- <draft-ietf-dnsext-delegation-signer-04.txt>
-
- Updates: RFC 1035, RFC 2535, RFC 3008.
-
-
- Delegation Signer record in parent.
-
-
-Status of this Memo
-
- This document is an Internet-Draft and is in full conformance with all
- provisions of Section 10 of RFC2026.
-
- 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
-
- Comments should be sent to the authors or the DNSEXT WG mailing list
- namedroppers@ops.ietf.org
-
- This draft expires on May 20, 2002.
-
- Copyright Notice
-
- Copyright (C) The Internet Society (2001). All rights reserved.
-
-
-
-Abstract
-
- The Delegation Signer (DS) RR set is stored in a delegating (parent)
- zone at each delegation point, and indicates the keys used in the
- delegated (child) zone. The main design goal of the DS RR simplify the
- operation of secure delegations by eliminating the need to store the
- same RR in parent and child, as is done with the NS RR set and the KEY
-
-
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- set in RFC2535.
- Secure resolvers need to take an additional step with DS to verify a
- child's KEY RR set. Operationally this schema is much simpler as
- operation of the two zones at delegation is now decoupled to great
- extent.
- This document updates RFC1035, RFC2535 and RFC3008.
-
-
-1 - Introduction
-
- Familiarity with the DNS system [RFC1035], DNS security extensions
- [RFC2535] and DNSSEC terminology [RFC3090] is important.
-
- When the same data can reside in two administratively different DNS
- zones, the data frequently gets out of sync. NS record in a zone
- indicates that this name is a delegation and the NS record lists the
- authorative servers for the real zone. Based on actual measurements
- 10-30% of all delegations in the Internet have differing NS sets at
- parent and child. There are number of reasons for this, including lack
- of communication between parent and child and bogus name-servers being
- listed to meet registrar requirements.
-
- DNSSEC [RFC2535,RFC3008,RFC3090] specifies that child must have its
- KEY set signed by the parent to create a verifiable chain of KEYs.
- There is some debate, where the signed KEY set should reside,
- parent[Parent] or child[RFC2535]. If the KEY set resides at the child,
- frequent two way communication is needed between the two parties.
- First the child needs to transmit the key set to parent and then the
- parent sends the signed set or signatures to child. If the KEY set
- resides at the parent the communication is reduced as the child only
- sends changed key sets to parent.
-
- DNSSEC[RFC2535] requires that the parent store NULL key set for
- unsecure children, this complicates resolution process in many cases
- as servers for both parent and child need to be queried for KEY set if
- the child server does not return a KEY set. Storing the KEY record
- only in the parent zone simplifies this and allows the elimination of
- the NULL key set.
-
- Another complication of the DNSSEC KEY model is that KEY record is
- used to store DNS zone keys and public keys for other protocols.
- There are number of potential problems with this including:
- 1. KEY set can become quite large if many applications/protocols
- store their keys at the zone apex. Possible protocols are IPSEC,
- HTTP, SMTP, SSH and others that use public key cryptography.
- 2. Key set may require frequent updates.
- 3. Probability of compromised/lost keys increases and triggers
- emergency key rollover procedures.
-
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- 4. Parent may refuse sign key sets with NON DNS zone keys.
- 5. Parent may not meet the child's expectations in turnaround time
- in resigning the key set.
-
- Given these and other reasons there is good reason to explore
- alternatives to using only KEY records to create chain of trust.
-
- Some of these problems can be reduced or eliminated by operational
- rules or protocol changes. To reduce the number of keys at apex, a
- rule to require applications to store their KEY records at the SRV
- name for that application is one possibility. Another is to restrict
- KEY record to DNS keys only and create a new type for all non DNS
- keys. Third possible solution is to ban the storage of non DNS related
- keys at zone apex. There are other possible solutions but they are
- outside the scope of this document.
-
-
-1.2 - Reserved words
-
- The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED",
- "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be
- interpreted as described in RFC2119.
-
-2 - DS (Delegation KEY Signer)
-
-2.1 - Delegation Signer Record model
-
- This document proposes an alternative to the KEY record chain of
- trust, that uses a special record that can only reside at the parent.
- This record will identify the key(s) that child are allowed to self
- sign its own KEY set.
-
- The chain of trust is now established by verifying the parent KEY set,
- the DS set from the parent and the KEY set at the child. This is
- cryptographically equivalent to just using KEY records.
-
- Communication between the parent and child is greatly reduced, since
- the child only needs to notify parent about changes in keys that sign
- its apex KEY RRset. Parent is ignorant of all other keys in the
- child's apex KEY RRset, and the child maintains full control over the
- apex KEY set and its content. Child can maintain any policies over
- its DNS and other KEY usage with minimal impact on parent. Thus if
- child wants to have frequent key rollover for its DNS keys parent does
- not need to be aware of it as the child can use one key to only sign
- its apex KEY set and other keys to sign the other record sets in the
- zone.
-
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- This model fits well with slow roll out of DNSSEC and islands of
- security model. In the islands of security model someone that trusts
- "good.example." can preconfigure a key from "good.example." as a
- trusted keys and from then on trusts any data that is signed by that
- key or has a chain of trust to that key. If "example." starts
- advertising DS records, "good.example." does not have to change
- operations, by suspending self-signing. DS records can also be used to
- identify trusted keys instead of KEY records. One further advantage
- is the information stored in the parent is minimized, as only records
- for secure delegations are needed.
-
- The main disadvantage of this approach that verifying delegations KEY
- set requires twice as many signature verification operations. There
- is no impact on the number of signatures verified for other RR sets.
-
-2.2 Protocol change
-
- Each secure delegation in a secure zone MUST contain a DS RR set. If
- a DS RR set accompanies the NS RR set, the intent is to state that the
- child zone is secured. If an NS RR set exists without a DS RR set the
- intent is to state that the child zone is unsecure. DS sets MUST NOT
- appear at non delegations or at zone APEX.
-
- In a zone that uses DS, insecure delegations MUST have the NODS[TBD]
- bit set in the NXT record. This is required to differenciate this
- delegation from Secure RFC2535 delegation.
-
- Updates RFC2535 sections 2.3.4 and 3.4, as well as RFC3008 section
- 2.7:
- Delegating zones MUST NOT store KEY records for delegations. The only
- records that can appear at delegation in parent are NS, SIG, NXT and
- DS.
-
- Zone MUST self sign its apex KEY set, it SHOULD sign it with a key
- that corresponds to a DS record in the parent. The KEY used to sign
- the apex KEY RRset MAY sign other RRsets in the zone.
-
- If child apex KEY RRset is not signed with one of the keys specified
- in the DS record the child is locally secure[RFC3090] and SHOULD only
- be considered secure if the resolver has been configured to trust the
- key used.
-
- Authorative server answering a query with the OK bit[OKbit] set, MUST
- include the DS records and NXT record along with signatures in answers
- for a delegation and space is available. DS and NXT records SHOULD
- have lower priority than address records but higher priority than KEY.
- Caching servers SHOULD return the DS and parent NXT record(s) in the
- additional section under the same condition.
-
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-2.2.1 - Comments on protocol change
-
- Over the years there has been various discussions on that the
- delegation model in DNS is broken as there is no real good way to
- assert if delegation exists. In RFC2535 version of DNSSEC the
- authentication of a delegation is the NS bit in the NXT bitmap at the
- delegation point. Something more explicit is needed and the DS record
- addresses this for secure delegations.
-
- DS record is the first DNS record that can only appear on the upper
- side of a delegation. NS records appear at both sides as do SIG and
- NXT. All other records can only appear at the lower side. This will
- cause some problems as servers authorative for parent, reject DS
- record even if the server understands unknown types, or will not hand
- them out unless explicitly asked. Similarly a nameserver acting as a
- authorative for child and as a caching recursive server may never
- return the DS record.
-
- A caching server that supports unkown types, does not care from which
- side DS record comes from and thus does not have to be changed.
- Different TTL values on the child's NS set and parents DS set can
- cause the DS set to expire before the NS set.
-
- Secure resolvers need to know about the DS record and how to interpret
- it. In the worst case, introducing the DS record, doubles the
- signatures that need to be checked to validate a KEY set.
-
-2.3 Wire format of DS record
-
- The DS (type=TDB) record consists of algorithm, key tag and SHA-1
- digest of the public key KEY record allowed to sign the child's
- delegation.
-
- 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 | |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | SHA-1 digest |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | (20 bytes) |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- | |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
- | |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
- | |
- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
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- The key tag is calculated as specified in RFC2535, Algorithm MUST be
- an algorithm number assigned in the range 1..251 and the algorithm
- MUST be allowed to sign DNS data. The SHA-1 digest is calculated over
- the canonical name of the delegation followed by the RDATA of the KEY
- record.
- DS records MUST NOT point to a null KEY record, and the KEY records
- pointed to by DS records MUST have protocol value 3 (DNSSEC).
- DS records MUST NOT point to KEY records where flag field has folowing
- bit settings, bit 0 (no authentication) is set, bit 6 MUST be set to 0
- and bit 7 MUST be set to 1 (zone key). Settings of other bits are not
- important.
- The size of the DS RDATA is 23 bytes, regardless of key size.
-
-2.3.1 Justifications for fields
-
- The algorithm and key tag fields are here to allow resolvers to
- quickly identify the candidate KEY records to examine. The key tag
- adds some greater assurance than SHA-1 digest on its own. SHA-1 is a
- strong cryptographic checksum, it is real hard for attacker to
- generate a KEY record that has the same SHA-1 digest. Combining the
- name of the key and the key data as input to the digest provides
- stronger assurance of the binding.
-
- This format allows concise representation of the keys that child will
- use, thus keeping down the size of the answer for the delegation,
- reducing the probability of packet overflow. The SHA-1 hash is strong
- enough to uniquely identify the key. This is similar to the PGP
- footprint.
-
- DS record is also well suited to lists trusted keys for islands of
- security in configuration files.
-
-2.4 Presentation format of DS record
-
- The presentation format of DS record consists of 2 numbers followed by
- digest presented in hex.
- foo.example DS 12345 3 123456789abcdef67890
-
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-2.5 Transition issues for installed base
-
- RFC2535 compliant resolver will assume that all DS secured delegations
- are locally secure. This is a bad thing, thus it might be necessary
- for a transition period to support both DS and SIG@Child. The cost is
- one or more signatures in the answer for KEY records and that early
- adopters have to use cumbersome communications that DS solves. #.bp
-
-2.6 Backwards compatibilty with RFC2535 SIG@child and RFC1035
-
- This section documents how a resolver determines the type of
- delegation.
- RFC1035 delegation has:
-
- RFC1035 NS
-
- RFC2535 adds the following two cases:
-
- Secure RFC2535: NS + NXT + SIG(NXT)
- NXT bit map contains: NS SIG NXT
- Insecure RFC2535: NS + KEY + SIG(KEY) + NXT + SIG(NXT)
- NXT bit map contains: NS SIG KEY NXT
- KEY must be null-key.
-
- DS adds the following two states:
-
- Secure DS: NS + DS + SIG(DS) + NXT + SIG(NXT)
- NXT bit map contains: NS SIG NXT DS
- Insecure DS: NS + NXT + SIG(NXT)
- NXT bit map contains: NS SIG KEY NXT NODS
-
- If the NODS bit is not used, a resover can not determine if this is a
- DS delegation zone. Thus is not able to determine if this delegtion is
- a secure RFC2535 or a insecure DS.
-
-2.6.1 NODS support in servers
-
- NODS is a virtual type, servers MUST refuse to store any record of
- this type. No special processing is required on answers.
-
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-3 Resolver Example
-
- To create a chain of trust resolver goes from trusted KEY to DS to
- KEY.
-
- Assume the key for domain "example." is trusted. In zone "example."
- we have
- example. KEY <stuff>
- secure.example. DS tag=10243 alg=3 <foofoo>
- secure.example. NS ns1.secure.example.
- NS ns2.secure.example.
- secure.example. NXT NS SIG NXT DS unsecure.example.
- secure.example. SIG(NXT)
- secure.example. SIG(DS)
- unsecure.example NS ns1.unsecure.example.
- unsecure.example NS ns2.unsecure.example.
- unsecure.example. NXT NS SIG NXT NODS .example.
- unsecure.example. SIG(NXT)
-
- In zone "secure.example." we have
- secure.example. SOA <soa stuff>
- secure.example. NS ns1.secure.example.
- NS ns1.secure.example.
- secure.example. KEY <tag=12345 size=1024 alg=3>
- KEY <tag=54321 size=512 alg=5>
- KEY <tag=32145 size=1024 alg=3>
- secure.example. SIG(KEY) <key-tag=12345 alg=3>
- secure.example. SIG(SOA) <key-tag=54321 alg=5>
- secure.example. SIG(NS) <key-tag=54321 alg=5>
-
- In this example the trusted key for "example." signs the DS record for
- "secure.example.", making that a trusted record. The DS record states
- what key is expected to sign the KEY RRset at "secure.example". Here
- "secure.example." has three different KEY records and the KEY
- identified in the DS record signs the KEY set, thus the KEY set is
- validated and trusted. Note that one of the other keys in the keyset
- actually signs the zone data, and resolvers will trust the signatures
- as the key appears in the KEY set.
-
- This example has only one DS record for the child but there no reason
- to outlaw multiple DS records. More than one DS record is needed
- during signing key rollover. It is strongly recommended that the DS
- set be kept small.
-
- Resolver determines the security status of "unsecure.example." by
- examining the parent size NXT for this name.
-
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-3.1 Resolver cost estimates for DS records
-
- From a RFC2535 resolver point of view for each delegation followed to
- chase down an answer one KEY record has to be verified and possibly
- some other records based on policy, for example the contents of the NS
- set. Once the resolver gets to the appropriate delegation validating
- the answer may require verifying one or more signatures. A simple A
- record lookup requires at least N delegations to be verified and 1
- RRset. For a DS enabled resolver the cost is 2N+1. For MX record the
- cost where the target of the MX record is in the same zone as the MX
- record the costs are N+2 and 2N+2. In the case of negative answer the
- same ratios hold true.
-
- Resolver may require an extra query to get the DS record and this may
- add to the overall cost of the query, but this is never worse than
- chasing down NULL KEY records from the parent in RFC2535 DNSSEC.
-
- DS adds processing overhead on resolvers, increases the size of
- delegation answers but much less than SIG@Parent.
-
-4 Acknowledgments
-
- Number of people have over the last few years contributed number of
- ideas that are captured in this document. The core idea of using one
- key to only sign key set, comes from discussions with Bill Manning and
- Perry Metzger on how to put in a single root key in all resolvers.
- Alexis Yushin, Brian Wellington, Jakob Schlyter, Scott Rosen, Edward
- Lewis, Dan Massey, Lars-Johan Liman, Mark Kosters, Olaf Kolman, Miek
- Gieben, Havard Eidnes, Donald Eastlake 3rd., Randy Bush, David Blacka,
- Rob Austein, Derek Atkins, Roy Arends, and others have provided useful
- comments.
-
-4 - Security Considerations:
-
- This document proposes a change to the validation chain of KEY records
- in DNS. The change in is not believed to reduce security in the
- overall system, in RFC2535 DNSSEC child must communicate keys to
- parent and prudent parents will require some authentication on that
- handshake. The modified protocol will require same authentication but
- allows the child to exert more local control over its own KEY set.
-
- There is a possibility that an attacker can generate an valid KEY that
- matches all the DS fields thus starting to forge data from the child.
- This is considered impractical as on average more than 2^80 keys must
- be generated before one is found that will match.
-
- DS record is a change to DNSSEC protocol and there is some installed
- base of implementations, as well as text books on how to set up
-
-
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- secured delegations. Implementations that do not understand DS record
- will not be able to follow the KEY to DS to KEY chain and consider all
- zone secured that way insecure.
-
-5 - IANA Considerations:
-
- IANA needs to allocate RR type code for DS from the standard RR type
- space.
-
- IANA needs to allocate RR type code for the virtual NODS record from
- the standard RR type space. Note: SINK (40) was never implemented and
- that type code can be reused for NODS.
-
-References:
-
-[RFC1035] P. Mockapetris, ``Domain Names - Implementation and
- Specification'', STD 13, RFC 1035, November 1987.
-
-[RFC2535] D. Eastlake, ``Domain Name System Security Extensions'', RFC
- 2535, March 1999.
-
-[RFC3008] B. Wellington, ``Domain Name System Security (DNSSEC) Signing
- Authority'', RFC 3008, November 2000.
-
-[RFC3090] E. Lewis `` DNS Security Extension Clarification on Zone
- Status'', RFC 3090, March 2001.
-
-[OKbit] D. Conrad, ``Indicating Resolver Support of DNSSEC'', work in
- progress <draft-ietf-dnsext-dnssec-okbit-02.txt>, April 2001.
-
-[Parent] R. Gieben, T. Lindgreen, ``Parent stores the child's zone
- KEYs'', work in progress <draft-ietf-dnsext-parent-stores-
- zones-keys-01.txt>, May 2001.
-
-Author Address
-
- Olafur Gudmundsson
- 3826 Legation Street, NW
- Washington, DC, 20015
- USA
- <ogud@ogud.com>
-
-
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-Appendix A: Changes from Prior versions
-
-Changes from version 03
- Added strict rules on what KEY records can be pointed to by DS.
-
-Changes from version 02
- Added text outlawing DS at non delegations.
- Added table showing the contents of DS, SIG@child, and RFC1034
- delegations.
- Added the NODS type/bit definition to distiguish insecure DS
- delegation from secure SIG@child one.
- Added the requirement that NXT be returned with referal answers.
- Minor text edits.
-
-Changes from version 01
- Deleted KEY size field as it did not contribute anything but
- complexity.
- Number of wordsmith changes to make document more readable.
- The word CAN was used when SHOULD was intended.
- Deleted section 2.4 "Justifications for compact format" moved relevant
- text to section 2.2.
- Reverse alphabetized the acknowledgments section.
- Reorganized sections 1 and 2 for readability.
-
-
-Changes from version 00
- Changed name from DK to DS based on working group comments.
- Dropped verbose format based on WG comments.
- Added text about TTL issue/problem in caching servers.
- Added text about islands of security and clarified the cost impact.
- Major editing of arguments and some reordering of text for clarity.
- Added section on transition issues.
-
-Full Copyright Statement
-
- Copyright (C) The Internet Society (2001). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published and
- distributed, in whole or in part, without restriction of any kind,
- provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of developing
- Internet standards in which case the procedures for copyrights defined
- in the Internet Standards process must be followed, or as required to
-
-
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- translate it into languages other than English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS 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."
-
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--- /dev/null
+
+
+
+
+
+
+ DNSEXT Working Group Olafur Gudmundsson
+ INTERNET-DRAFT January 2002
+ <draft-ietf-dnsext-delegation-signer-05.txt>
+
+ Updates: RFC 1035, RFC 2535, RFC 3008, RFC 3090.
+
+
+ Delegation Signer Resource Record
+
+
+Status of this Memo
+
+ This document is an Internet-Draft and is in full conformance with
+ all provisions of Section 10 of RFC2026.
+
+ 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
+
+ Comments should be sent to the authors or the DNSEXT WG mailing list
+ namedroppers@ops.ietf.org
+
+ This draft expires on July 5, 2002.
+
+ Copyright Notice
+
+ Copyright (C) The Internet Society (2002). All rights reserved.
+
+
+
+Abstract
+
+ The Delegation Signer Resource Record is inserted at a zone cut point
+ to indicate tha the delegated zone is digitally signed and that the
+ delegation zone recognizes the indicated key as a valid zone key for
+ the delegated zone. The DS RR is an modification to the DNS Security
+
+
+
+Gudmundsson Expires July 2002 [Page 1]
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ Extensions definition, motivated by operational considerations. The
+ intent is to use the resource record as an explicit statement about
+ the delegation, rather than relying on inference.
+
+ This document defines the DS RR, gives examples of how it is used and
+ the implications of this record on resolvers. This change is not
+ backwards compatible with RFC 2535.
+ This document updates RFC1035, RFC2535, RFC3008 and RFC3090.
+
+
+1 - Introduction
+
+ Familiarity with the DNS system [RFC1035], DNS security extensions
+ [RFC2535] and DNSSEC terminology [RFC3090] is important.
+
+ Experience shows that when the same data can reside in two
+ administratively different DNS zones, the data frequently gets out of
+ sync. NS record in a zone indicates that this name is a delegation
+ and the NS record lists the authorative servers for the real zone.
+ Based on actual measurements 10-30% of all delegations in the
+ Internet have differing NS sets at parent and child. There are number
+ of reasons for this, including lack of communication between parent
+ and child and bogus name-servers being listed to meet registrar
+ requirements.
+
+ DNSSEC [RFC2535,RFC3008,RFC3090] specifies that child must have its
+ KEY set signed by the parent to create a verifiable chain of KEYs.
+ There has been some debate on where the signed KEY set should reside,
+ at the child[RFC2535] or at the parent. If the KEY set resides at the
+ child, maintaining the signed KEY set in the child, requires frequent
+ two way communication is needed between the two parties. First the
+ child needs to transmit the key set to parent and then the parent
+ sends the signed set or signatures to child. Storing the KEY at the
+ parent simplifies the communication.
+
+ DNSSEC[RFC2535] requires that the parent store NULL key set for
+ unsecure children, this is intended to be a signal that the child is
+ unsecure. NULL Key RRset is a waste as a whole signed RRset is used
+ to effectively communicate one bit of information, child is unsecure.
+ Chasing down NULL key records complicates resolution process in many
+ cases as servers for both parent and child need to be queried for KEY
+ set if the child server does not return a KEY set. Storing the KEY
+ record only in the parent zone simplifies this and would allow the
+ elimination of the NULL key set. For large delegation zones the cost
+ of NULL keys is significant barrier to deployment.
+
+ Another complication of the DNSSEC KEY model is that KEY record is
+ used to store DNS zone keys and public keys for other protocols.
+
+
+
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ There are number of potential problems with this including:
+ 1. KEY set can become quite large if many applications/protocols
+ store their keys at the zone apex. Possible protocols are IPSEC,
+ HTTP, SMTP, SSH and others that use public key cryptography.
+ 2. Key set may require frequent updates.
+ 3. Probability of compromised/lost keys increases and triggers
+ emergency key rollover procedures.
+ 4. Parent may refuse sign key sets with NON DNS zone keys.
+ 5. Parent may not meet the child's expectations in turnaround time
+ in resigning the key set.
+
+ Given these and other reasons there is good reason to explore
+ alternatives to using only KEY records to create chain of trust.
+
+ Some of these problems can be reduced or eliminated by operational
+ rules or protocol changes. To reduce the number of keys at apex, a
+ rule to require applications to store their KEY records at the SRV
+ name for that application is one possibility. Another is to restrict
+ KEY record to DNS keys only and create a new type for all non DNS
+ keys. Third possible solution is to ban the storage of non DNS
+ related keys at zone apex. There are other possible solutions but
+ they are outside the scope of this document.
+
+
+1.2 - Reserved words
+
+ The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED",
+ "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be
+ interpreted as described in RFC2119.
+
+2 - DS (Delegation KEY Signer)
+
+2.1 - Delegation Signer Record model
+
+ This document presents replacement of the DNSSEC KEY record chain of
+ trust[RFC2535], that uses a new RR that only reside at the parent.
+ This record will identify the key(s) that child uses to self sign its
+ own KEY set.
+
+ The chain of trust is now established by verifying the parent KEY
+ set, the DS set from the parent and the KEY set at the child. This is
+ cryptographically equivalent to just using KEY records.
+
+ Communication between the parent and child is greatly reduced, since
+ the child only needs to notify parent about changes in keys that sign
+ its apex KEY RRset. Parent is ignorant of all other keys in the
+ child's apex KEY RRset, furthermore the child maintains full control
+ over the apex KEY set and its content. Child can maintain any
+
+
+
+Gudmundsson Expires July 2002 [Page 3]
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ policies over its DNS and other KEY usage with minimal impact on
+ parent. Thus if child wants to have frequent key rollover for its DNS
+ zone keys parent does not need to be aware of it as the child can use
+ one key to only sign its apex KEY set and other keys to sign the
+ other record sets in the zone.
+
+ This model fits well with slow roll out of DNSSEC and islands of
+ security model. In the islands of security model someone that trusts
+ "good.example." can preconfigure a key from "good.example." as a
+ trusted keys and from then on trusts any data that is signed by that
+ key or has a chain of trust to that key. If "example." starts
+ advertising DS records, "good.example." does not have to change
+ operations, by suspending self-signing. DS records can also be used
+ to identify trusted keys instead of KEY records. Another significant
+ advantage is the information stored in the large delegation zones
+ reduced, as only signed keying records for secure delegations are
+ needed, unlike the NULL KEY record at every unsecure delegation.
+
+ The main disadvantage of this approach that verifying delegations KEY
+ set requires two signature verification operations instead of one in
+ RFC 2535. There is no impact on the number of signatures verified
+ for other RR sets.
+
+2.2 Protocol change
+
+ All DNS servers and resolvers that support DS MUST support OK bit
+ [RFC3225] and support larger message size[RFC3226]. Each secure
+ delegation in a secure zone MUST contain a DS RR set. If a query
+ contains the OK bit, server returning a referral for the delegation
+ MUST include the following RR sets in the authority section in this
+ order:
+ parent NS
+ DS and SIG(DS) (if present)
+ parent NXT and SIG(NXT/parent)
+ This increases the size of referral messages and may cause some or
+ all glue to be omitted. If DS or NXT RR or their signatures do not
+ fit inside the DNS message the TC bit must be set. Additional
+ section processing is not changed.
+
+ If a DS RR set accompanies the NS RR set, this states that the child
+ zone is secured. If an NS RR set exists without a DS RR set the
+ intent is to state that the child zone is unsecure. DS sets MUST NOT
+ appear at non delegations or at zone APEX.
+
+ Following section 2.2.1 replaces RFC2535 sections 2.3.4 and 3.4,
+ section 2.2.2 replaces RFC3008 section 2.7, RFC3090 updates are in
+ section 2.2.3.
+
+
+
+
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+2.2.1 RFC2535 2.3.4 and 3.4: Special considerations at delegation points
+
+ DNS security would like to view each zone as a unit of data
+ completely under the control of the zone owner with each entry
+ (RRset) signed by a special private key held by the zone manager.
+ But the DNS protocol views the leaf nodes in a zone, which are also
+ the apex nodes of a subzone (i.e., delegation points), as "really"
+ belonging to the subzone. These nodes occur in two master files and
+ might have RRs signed by both the upper and lower zone's keys. A
+ retrieval could get a mixture of these RRs and SIGs, especially since
+ one server could be serving both the zone above and below a
+ delegation point[RFC 2181].
+
+ For every secure delegation there MUST be a DS record stored in
+ parent zone signed by parent zone key. Parent zone MUST NOT contain
+ KEY record at delegation points. Delegations in parent MAY only
+ contain following RR types NS, DS, NXT and SIG. NS RR set MUST NOT be
+ signed. The NXT RR type is the exceptional case that will always
+ appear differently and authoritatively in both the super-zone and
+ subzone, if both are secure.
+
+ All secure zones MUST contain a self signed KEY RR set at apex. Upon
+ verifying the DS set from the parent, the resolver MAY trust any KEY
+ identified in the DS set as a valid signer of the childs apex KEY
+ set. Resolvers configured to trust one of the KEY's signing the KEY
+ set MAY now treat any data signed by the zone keys in the KEY set as
+ secure. In all other cases resolvers MUST consider the zone
+ insecure. DS RR MUST NOT appear at zone APEX.
+
+
+2.2.2 Signers name (replaces RFC3008 section 2.7)
+
+ The signer's name field of a data SIG MUST contain the name of the
+ zone to which the data and signature belong. The combination of
+ signer's name, key tag, and algorithm MUST identify a zone key if the
+ SIG is to be considered material. This document defines a standard
+ policy for DNSSEC validation; local policy may override the standard
+ policy.
+
+ There are no restrictions on the signer field of a SIG(0) record.
+ The combination of signer's name, key tag, and algorithm MUST
+ identify a key if this SIG(0) is to be processed.
+
+
+2.2.4 changes to RFC3090
+
+ Number of sections of RFC3090 need to be updated to reflect the DS
+ record.
+
+
+
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+2.2.4.1 RFC3090: Updates to section 1: Introduction
+
+ Most of the text is still relevant but the words ``NULL key'' are to
+ be replaced with ``missing DS set''. In section 1.3 the last three
+ paragraphs discuss the confusion in sections of RFC 2535, that are
+ replaced in section 2.2.1 above, thus these paragraphs are now
+ obsolete.
+
+
+2.2.4.2 RFC3090 section 2.1: Globally Secured
+
+ Rule 2.1.b is replaced by following rule:
+
+ 2.1.b. The zone's apex KEY RR set MUST be self signed by a private
+ key in the KEY RR set. The private key's public companion MUST be a
+ zone signing KEY RR (2.a) of a mandatory to implement algorithm and
+ owned by the parent's apex. This KEY must be identified by a signed
+ DS RR in the parent zone.
+
+ If a zone cannot get a parent to advertise a DS record for it, child
+ zone cannot be considered globally secured. The only exception to
+ this is the root zone, for which there is no parent zone
+
+
+2.2.4.3 RFC3090 section 3: Experimental Status.
+
+ The only difference between Experimental status and globally secured
+ is the missing DS in the parent. All Locally Secured zones are
+ Experimental.
+
+2.3 - Comments on protocol changes
+
+ Over the years there has been various discussions on that the
+ delegation model in DNS is broken as there is no real good way to
+ assert if delegation exists. In RFC2535 version of DNSSEC the
+ authentication of a delegation is the NS bit in the NXT bitmap at the
+ delegation point. Something more explicit is needed and the DS record
+ addresses this for secure delegations.
+
+ DS record is a major change to DNS as it is the first DNS record that
+ can only appear on the upper side of a delegation. Adding it will
+ cause interoperabilty problems and a flag day for DNSSEC. Many old
+ servers and resolvers MUST be upgraded to take advantage of DS. Some
+ old servers will be able to be authorative for zones with DS records
+ but will not add the NXT and DS records to authority section. Same
+ goes for caching servers, some may even refuse to pass on the DS and
+ NXT records.
+
+
+
+
+Gudmundsson Expires July 2002 [Page 6]
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+2.4 Wire format of DS record
+
+ The DS (type=TDB) record consists of algorithm, key tag and SHA-1
+ digest of a public key KEY record that is allowed/used to sign the
+ child's delegation. Other keys MAY sign the child's apex KEY set.
+
+ 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 | Digest type |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | SHA-1 digest |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | (20 bytes) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ The key tag is calculated as specified in RFC2535, Algorithm MUST be
+ an algorithm number assigned in the range 1..251 and the algorithm
+ MUST be allowed to sign DNS data. The digest type is an identifier
+ for the digest algorithm used. The digest is calculated over the
+ canonical name of the delegation followed by the whole RDATA of the
+ KEY record.
+
+ Digest type value 0 is reserved, value 1 is SHA-1, reserving other
+ types requires IETF standards action. For interoperabilty reasons as
+ few digest type algorithms should be reserved, the only reason to
+ reserve another digest type is to increase security.
+ DS records MUST point to zone KEY records that are allowed to
+ authenticate DNS data. Protocol MUST be set to 3. Flag field bits 0
+ and 6 MUST be set to 0, bit 7 MUST be set to 1. Value of other bits
+ is not important.
+ The size of the DS RDATA for type 1(SHA-1) is 24 bytes, regardless of
+ key size.
+
+2.4.1 Justifications for fields
+
+ The algorithm and key tag fields are here to allow resolvers to
+ quickly identify the candidate KEY records to examine. The key tag
+ adds some greater assurance than SHA-1 digest on its own. SHA-1 is a
+ strong cryptographic checksum, it is real hard for attacker to
+ generate a KEY record that has the same SHA-1 digest. Combining the
+ name of the key and the key data as input to the digest provides
+ stronger assurance of the binding.
+
+
+
+Gudmundsson Expires July 2002 [Page 7]
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+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ This format allows concise representation of the keys that child will
+ use, thus keeping down the size of the answer for the delegation,
+ reducing the probability of packet overflow. The SHA-1 hash is strong
+ enough to uniquely identify the key. This is similar to the PGP
+ footprint. The digest type field is there for possible future
+ expansion.
+
+ DS record is well suited to lists trusted keys for islands of
+ security in configuration files.
+
+2.5 Presentation format of DS record
+
+ The presentation format of DS record consists of 2 numbers followed
+ by digest presented in hex.
+ foo.example DS 12345 3 1 123456789abcdef67890
+
+2.6 Transition issues for installed base
+
+ RFC2535 compliant resolver will assume that all DS secured
+ delegations are locally secure. This is a bad thing, but the DNSEXT
+ working group has determined that rather than having to have to deal
+ with both RFC2535 secured zone and DS secured zone, a rapid adaption
+ of DS is preferable. Thus the only option for early adopters is to
+ upgrade to DS as soon as possible.
+
+2.6.1 Backwards compatibility with RFC2535 and RFC1035
+
+ This section documents how a resolver determines the type of
+ delegation.
+ RFC1035 delegation has:
+
+ RFC1035 NS
+
+ RFC2535 adds the following two cases:
+
+ Secure RFC2535: NS + NXT + SIG(NXT)
+ NXT bit map contains: NS SIG NXT
+ Insecure RFC2535: NS + KEY + SIG(KEY) + NXT + SIG(NXT)
+ NXT bit map contains: NS SIG KEY NXT
+ KEY must be null-key.
+
+ DS has the following two states:
+
+ Secure DS: NS + DS + SIG(DS) + NXT + SIG(NXT)
+ NXT bit map contains: NS SIG NXT DS
+ Insecure DS: NS + NXT + SIG(NXT)
+ NXT bit map contains: NS SIG KEY NXT
+
+
+
+
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+\f
+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ It is hard for a resolver to determine if a delegation is Secure 2535
+ or Insecure DS. This can be overcome by adding a flag to the NXT bit
+ map but only upgraded resolvers will understand this flag. Having
+ both parent and child signatures on the keyset may allow old
+ resolvers to accept zone as secure, but the cost of doing this for a
+ long time is much higher than just outlaw Sig@Child and force rapid
+ deployment of DS enabled servers and resolvers.
+
+ RFC 2535 and DS can in theory be deployed in parallel, but this will
+ require resolvers to deal with RFC 2535 configurations forever. This
+ document obsoletes NULL KEY in parent zones, that is difficult enough
+ change that flag day is required.
+
+3 Resolver Example
+
+ To create a chain of trust resolver goes from trusted KEY to DS to
+ KEY.
+
+ Assume the key for domain "example." is trusted. Zone "example."
+ contains at least the following records:
+ example. SOA <soa stuff>
+ example. NS ns.example.
+ example. KEY <stuff>
+ example. NXT NS SOA KEY SIG NXT
+ example. SIG(SOA)
+ example. SIG(NS)
+ example. SIG(NXT)
+ example. SIG(KEY)
+ secure.example. NS ns1.secure.example.
+ secure.example. DS tag=10243 alg=3 <foofoo>
+ secure.example. NXT NS SIG NXT DS unsecure.example.
+ secure.example. SIG(NXT)
+ secure.example. SIG(DS)
+ unsecure.example NS ns1.unsecure.example.
+ unsecure.example. NXT NS SIG NXT .example.
+ unsecure.example. SIG(NXT)
+
+ In zone "secure.example." following records exist:
+ secure.example. SOA <soa stuff>
+ secure.example. NS ns1.secure.example.
+ secure.example. KEY <tag=12345 alg=3>
+ secure.example. SIG(KEY) <key-tag=12345 alg=3>
+ secure.example. SIG(SOA) <key-tag=12345 alg=3>
+ secure.example. SIG(NS) <key-tag=12345 alg=5>
+
+ In this example the trusted key for "example." signs the DS record
+ for "secure.example.", making that a trusted record. The DS record
+ states what key is expected to sign the KEY RRset at
+
+
+
+Gudmundsson Expires July 2002 [Page 9]
+\f
+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ "secure.example". Here "secure.example." signs its KEY set with the
+ KEY identified in the DS set, thus the KEY set is validated and
+ trusted.
+
+ This example has only one DS record for the child, parents MUST allow
+ multiple DS records to facilitate key rollover. It is strongly
+ recommended that the DS set be kept small, 2 or 3 records SHOULD be
+ sufficient in all cases.
+
+ Resolver determines the security status of "unsecure.example." by
+ examining the parent NXT for this name.
+
+3.1 Resolver cost estimates for DS records
+
+ From a RFC2535 resolver point of view for each delegation followed to
+ chase down an answer one KEY record has to be verified and possibly
+ some other records based on policy, for example the contents of the
+ NS set. Once the resolver gets to the appropriate delegation
+ validating the answer may require verifying one or more signatures.
+ A simple A record lookup requires at least N delegations to be
+ verified and 1 RRset. For a DS enabled resolver the cost is 2N+1.
+ For MX record the cost where the target of the MX record is in the
+ same zone as the MX record the costs are N+2 and 2N+2. In the case of
+ negative answer the same ratios hold true.
+
+ Resolver may require an extra query to get the DS record and this may
+ add to the overall cost of the query, but this is never worse than
+ chasing down NULL KEY records from the parent in RFC2535 DNSSEC.
+
+ DS adds processing overhead on resolvers, increases the size of
+ delegation answers but much less than SIG@Parent.
+
+4 - Security Considerations:
+
+ This document proposes a change to the validation chain of KEY
+ records in DNS. The change in is not believed to reduce security in
+ the overall system, in RFC2535 DNSSEC child must communicate keys to
+ parent and prudent parents will require some authentication on that
+ handshake. The modified protocol will require same authentication but
+ allows the child to exert more local control over its own KEY set.
+
+ There is a possibility that an attacker can generate an valid KEY
+ that matches all the DS fields thus starting to forge data from the
+ child. This is considered impractical as on average more than 2^80
+ keys must be generated before one is found that will match.
+
+ DS record is a change to DNSSEC protocol and there is some installed
+ base of implementations, as well as text books on how to set up
+
+
+
+Gudmundsson Expires July 2002 [Page 10]
+\f
+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+ secured delegations. Implementations that do not understand DS record
+ will not be able to follow the KEY to DS to KEY chain and consider
+ all zone secured that way insecure.
+
+5 - IANA Considerations:
+
+ IANA needs to allocate RR type code for DS from the standard RR type
+ space.
+
+ IANA needs to open a new registry for the DS type for Digest
+ algorithms, Defined types are, 0 is Reserved, 1 is SHA-1. Adding new
+ reservations requires IETF standards action.
+
+4 Acknowledgments
+
+ Number of people have over the last few years contributed number of
+ ideas that are captured in this document. The core idea of using one
+ key to only sign key set, comes from discussions with Bill Manning
+ and Perry Metzger on how to put in a single root key in all
+ resolvers.
+ Alexis Yushin, Brian Wellington, Paul Vixie, Jakob Schlyter, Scott
+ Rosen, Edward Lewis, Dan Massey, Lars-Johan Liman, Mark Kosters, Olaf
+ Kolman, Phillip Hallam-Baker, Miek Gieben, Havard Eidnes, Donald
+ Eastlake 3rd., Randy Bush, David Blacka, Steve Bellovin, Rob Austein,
+ Derek Atkins, Roy Arends, Harald Alvestrand, and others have provided
+ useful comments.
+
+References:
+
+[RFC1035] P. Mockapetris, ``Domain Names - Implementation and
+ Specification'', STD 13, RFC 1035, November 1987.
+
+[RFC2181] R. Elz, R. Bush, ``Clarifications to the DNS Specification'',
+ RFC 2181, July 1997.
+
+[RFC2535] D. Eastlake, ``Domain Name System Security Extensions'', RFC
+ 2535, March 1999.
+
+[RFC3008] B. Wellington, ``Domain Name System Security (DNSSEC) Signing
+ Authority'', RFC 3008, November 2000.
+
+[RFC3090] E. Lewis `` DNS Security Extension Clarification on Zone
+ Status'', RFC 3090, March 2001.
+
+[RFC3225] D. Conrad, ``Indicating Resolver Support of DNSSEC'', RFC
+ 3225, December 2001.
+
+
+
+
+
+Gudmundsson Expires July 2002 [Page 11]
+\f
+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+[RFC3226] O. Gudmundsson, ``DNSSEC and IPv6 A6 aware server/resolver
+ message size requirements'', RFC 3226, December 2001.
+
+
+Author Address
+
+ Olafur Gudmundsson
+ 3826 Legation Street, NW
+ Washington, DC, 20015
+ USA
+ <ogud@ogud.com>
+
+Appendix A: Changes from Prior versions
+
+Changes from version 04
+ Reworded document to obsolete RFC2535 chain of trust, no backwards
+ compatibility. Require DS and NXT records in referrals in authority
+ section. Removed the NODS bit.
+ Added the requirement for OK bit and Message size.
+ Rewrote Abstract to better express what is in the document.
+ Removed size field from examples and simplified them.
+
+Changes from version 03
+ Added strict rules on what KEY records can be pointed to by DS.
+
+Changes from version 02
+ Added text outlawing DS at non delegations.
+ Added table showing the contents of DS, SIG@child, and RFC1034
+ delegations.
+ Added the NODS type/bit definition to distinguish insecure DS
+ delegation from secure SIG@child one.
+ Added the requirement that NXT be returned with referral answers.
+ Minor text edits.
+
+Changes from version 01
+ Deleted KEY size field as it did not contribute anything but
+ complexity.
+ Number of wordsmith changes to make document more readable.
+ The word CAN was used when SHOULD was intended.
+ Deleted section 2.4 "Justifications for compact format" moved
+ relevant text to section 2.2.
+ Reverse alphabetized the acknowledgments section.
+ Reorganized sections 1 and 2 for readability.
+
+
+
+
+
+
+
+
+Gudmundsson Expires July 2002 [Page 12]
+\f
+INTERNET-DRAFT Delegation Signer Record January 2002
+
+
+Changes from version 00
+ Changed name from DK to DS based on working group comments.
+ Dropped verbose format based on WG comments.
+ Added text about TTL issue/problem in caching servers.
+ Added text about islands of security and clarified the cost impact.
+ Major editing of arguments and some reordering of text for clarity.
+ Added section on transition issues.
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS 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."
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gudmundsson Expires July 2002 [Page 13]
projects / thirdparty / bind9.git / commitdiff
