Network Working Group M. StJohns
Internet-Draft Nominum, Inc.
-Expires: February 16, 2006 August 15, 2005
+Expires: July 14, 2006 January 10, 2006
Automated Updates of DNSSEC Trust Anchors
- draft-ietf-dnsext-trustupdate-timers-01
+ draft-ietf-dnsext-trustupdate-timers-02
Status of this Memo
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
- This Internet-Draft will expire on February 16, 2006.
+ This Internet-Draft will expire on July 14, 2006.
Copyright Notice
- Copyright (C) The Internet Society (2005).
+ Copyright (C) The Internet Society (2006).
Abstract
-StJohns Expires February 16, 2006 [Page 1]
+StJohns Expires July 14, 2006 [Page 1]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
addition of a single flag bit to the DNSKEY record.
+
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 1.1 Compliance Nomenclature . . . . . . . . . . . . . . . . . 3
- 1.2 Changes since -00 . . . . . . . . . . . . . . . . . . . . 3
+ 1.1. Compliance Nomenclature . . . . . . . . . . . . . . . . . 3
+ 1.2. Changes since -00 . . . . . . . . . . . . . . . . . . . . 3
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
- 2.1 Revocation . . . . . . . . . . . . . . . . . . . . . . . . 4
- 2.2 Add Hold-Down . . . . . . . . . . . . . . . . . . . . . . 4
- 2.3 Remove Hold-down . . . . . . . . . . . . . . . . . . . . . 5
- 2.4 Active Refresh . . . . . . . . . . . . . . . . . . . . . . 6
- 2.5 Resolver Parameters . . . . . . . . . . . . . . . . . . . 6
- 2.5.1 Add Hold-Down Time . . . . . . . . . . . . . . . . . . 6
- 2.5.2 Remove Hold-Down Time . . . . . . . . . . . . . . . . 6
- 2.5.3 Minimum Trust Anchors per Trust Point . . . . . . . . 6
+ 2.1. Revocation . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.2. Add Hold-Down . . . . . . . . . . . . . . . . . . . . . . 5
+ 2.3. Remove Hold-down . . . . . . . . . . . . . . . . . . . . . 5
+ 2.4. Active Refresh . . . . . . . . . . . . . . . . . . . . . . 6
+ 2.5. Resolver Parameters . . . . . . . . . . . . . . . . . . . 6
+ 2.5.1. Add Hold-Down Time . . . . . . . . . . . . . . . . . . 6
+ 2.5.2. Remove Hold-Down Time . . . . . . . . . . . . . . . . 6
+ 2.5.3. Minimum Trust Anchors per Trust Point . . . . . . . . 6
3. Changes to DNSKEY RDATA Wire Format . . . . . . . . . . . . . 6
- 4. State Table . . . . . . . . . . . . . . . . . . . . . . . . . 6
- 4.1 Events . . . . . . . . . . . . . . . . . . . . . . . . . . 7
- 4.2 States . . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 4. State Table . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 4.1. Events . . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 4.2. States . . . . . . . . . . . . . . . . . . . . . . . . . . 8
+ 4.3. Trust Point Deletion . . . . . . . . . . . . . . . . . . . 8
5. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 8
- 5.1 Adding A Trust Anchor . . . . . . . . . . . . . . . . . . 8
- 5.2 Deleting a Trust Anchor . . . . . . . . . . . . . . . . . 9
- 5.3 Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 9
- 5.4 Active Key Compromised . . . . . . . . . . . . . . . . . . 9
- 5.5 Stand-by Key Compromised . . . . . . . . . . . . . . . . . 9
- 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
- 6.1 Key Ownership vs Acceptance Policy . . . . . . . . . . . . 10
- 6.2 Multiple Key Compromise . . . . . . . . . . . . . . . . . 10
- 6.3 Dynamic Updates . . . . . . . . . . . . . . . . . . . . . 10
- 7. Normative References . . . . . . . . . . . . . . . . . . . . . 10
- Editorial Comments . . . . . . . . . . . . . . . . . . . . . . 11
- Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11
- Intellectual Property and Copyright Statements . . . . . . . . 12
-
-
+ 5.1. Adding A Trust Anchor . . . . . . . . . . . . . . . . . . 9
+ 5.2. Deleting a Trust Anchor . . . . . . . . . . . . . . . . . 9
+ 5.3. Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 9
+ 5.4. Active Key Compromised . . . . . . . . . . . . . . . . . . 9
+ 5.5. Stand-by Key Compromised . . . . . . . . . . . . . . . . . 10
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
+ 7.1. Key Ownership vs Acceptance Policy . . . . . . . . . . . . 10
+ 7.2. Multiple Key Compromise . . . . . . . . . . . . . . . . . 10
+ 7.3. Dynamic Updates . . . . . . . . . . . . . . . . . . . . . 11
+ 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
+ Editorial Comments . . . . . . . . . . . . . . . . . . . . . . . .
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
+ Intellectual Property and Copyright Statements . . . . . . . . . . 13
-
-StJohns Expires February 16, 2006 [Page 2]
+StJohns Expires July 14, 2006 [Page 2]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
1. Introduction
document DOES NOT discuss the general problem of the initial
configuration of trust anchors for the resolver.
-1.1 Compliance Nomenclature
+1.1. Compliance Nomenclature
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 BCP 14, [RFC2119].
-1.2 Changes since -00
+1.2. Changes since -00
Added the concept of timer triggered resolver queries to refresh the
-StJohns Expires February 16, 2006 [Page 3]
+StJohns Expires July 14, 2006 [Page 3]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
resolvers view of the trust anchor key RRSet.
Re-submitted expired draft as -01. Updated DNSSEC RFC References.
+ Draft -02. Added the IANA Considerations section. Added text to
+ describe what happens if all trust anchors at a trust point are
+ deleted.
+
+
2. Theory of Operation
The general concept of this mechanism is that existing trust anchors
compromise, an attacker could add a new key and revoke all the other
old keys.
-2.1 Revocation
+2.1. Revocation
Assume two trust anchor keys A and B. Assume that B has been
compromised. Without a specific revocation bit, B could invalidate A
of the private key of a DNSKEY to revoke that DNSKEY.
A key is considered revoked when the resolver sees the key in a self-
- signed RRSet and the key has the REVOKE bit set to '1'. Once the
- resolver sees the REVOKE bit, it MUST NOT use this key as a trust
- anchor or for any other purposes except validating the RRSIG over the
- DNSKEY RRSet specifically for the purpose of validating the
- revocation. Unlike the 'Add' operation below, revocation is
- immediate and permanent upon receipt of a valid revocation at the
- resolver.
+ signed RRSet and the key has the REVOKE bit (see Section 6 below) set
+ to '1'. Once the resolver sees the REVOKE bit, it MUST NOT use this
+ key as a trust anchor or for any other purposes except validating the
+ RRSIG over the DNSKEY RRSet specifically for the purpose of
+ validating the revocation. Unlike the 'Add' operation below,
+ revocation is immediate and permanent upon receipt of a valid
+ revocation at the resolver.
N.B. A DNSKEY with the REVOKE bit set has a different fingerprint
than one without the bit set. This affects the matching of a DNSKEY
used to configure a trust point. [msj3]
In the given example, the attacker could revoke B because it has
- knowledge of B's private key, but could not revoke A.
-2.2 Add Hold-Down
- Assume two trust point keys A and B. Assume that B has been
+StJohns Expires July 14, 2006 [Page 4]
+\f
+Internet-Draft trustanchor-update January 2006
-StJohns Expires February 16, 2006 [Page 4]
-\f
-Internet-Draft trustanchor-update August 2005
+ knowledge of B's private key, but could not revoke A.
+2.2. Add Hold-Down
+ Assume two trust point keys A and B. Assume that B has been
compromised. An attacker could generate and add a new trust anchor
key - C (by adding C to the DNSKEY RRSet and signing it with B), and
then invalidate the compromised key. This would result in the both
their own (e.g. using the example, signed only by B). This is no
worse than the current situation assuming a compromised key.
-2.3 Remove Hold-down
+2.3. Remove Hold-down
A new key which has been seen by the resolver, but hasn't reached
it's add hold-down time, MAY be removed from the DNSKEY RRSet by the
- zone owner. If the resolver sees a validated DNSKEY RRSet without
- this key, it waits for the remove hold-down time and then, if the key
- hasn't reappeared, SHOULD discard any information about the key.
-
-
-StJohns Expires February 16, 2006 [Page 5]
+StJohns Expires July 14, 2006 [Page 5]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
-2.4 Active Refresh
+ zone owner. If the resolver sees a validated DNSKEY RRSet without
+ this key, it waits for the remove hold-down time and then, if the key
+ hasn't reappeared, SHOULD discard any information about the key.
+
+2.4. Active Refresh
A resolver which has been configured for automatic update of keys
from a particular trust point MUST query that trust point (e.g. do a
lesser of 1 day or 10% of the original TTL or 10% of the original
expiration interval.
-2.5 Resolver Parameters
+2.5. Resolver Parameters
-2.5.1 Add Hold-Down Time
+2.5.1. Add Hold-Down Time
The add hold-down time is 30 days or the expiration time of the TTL
of the first trust point DNSKEY RRSet which contained the key,
DNSKEY RRSets which contain the new key MUST be seen by the resolver
prior to the key's acceptance.
-2.5.2 Remove Hold-Down Time
+2.5.2. Remove Hold-Down Time
The remove hold-down time is 30 days.
-2.5.3 Minimum Trust Anchors per Trust Point
+2.5.3. Minimum Trust Anchors per Trust Point
A compliant resolver MUST be able to manage at least five SEP keys
per trust point.
+
3. Changes to DNSKEY RDATA Wire Format
Bit n [msj2] of the DNSKEY Flags field is designated as the 'REVOKE'
consider this key permanently invalid for all purposes except for
validing the revocation.
-4. State Table
- The most important thing to understand is the resolver's view of any
- key at a trust point. The following state table describes that view
- at various points in the key's lifetime. The table is a normative
- part of this specification. The initial state of the key is 'Start'.
-StJohns Expires February 16, 2006 [Page 6]
+StJohns Expires July 14, 2006 [Page 6]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
+4. State Table
+
+ The most important thing to understand is the resolver's view of any
+ key at a trust point. The following state table describes that view
+ at various points in the key's lifetime. The table is a normative
+ part of this specification. The initial state of the key is 'Start'.
The resolver's view of the state of the key changes as various events
occur.
Removed | | | | | | |
----------------------------------------------------------
-
-4.1 Events
+4.1. Events
NewKey The resolver sees a valid DNSKEY RRSet with a new SEP key.
That key will become a new trust anchor for the named trust point
after its been present in the RRSet for at least 'add time'.
"REVOKED" bit set, and there is an RRSig over the DNSKEY RRSet
signed by this key.
-4.2 States
- Start The key doesn't yet exist as a trust anchor at the resolver.
- It may or may not exist at the zone server, but hasn't yet been
- seen at the resolver.
-
-StJohns Expires February 16, 2006 [Page 7]
+StJohns Expires July 14, 2006 [Page 7]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
+4.2. States
+ Start The key doesn't yet exist as a trust anchor at the resolver.
+ It may or may not exist at the zone server, but hasn't yet been
+ seen at the resolver.
AddPend The key has been seen at the resolver, has its 'SEP' bit set,
and has been included in a validated DNSKEY RRSet. There is a
hold-down time for the key before it can be used as a trust
Valid The key has been seen at the resolver and has been included in
all validated DNSKEY RRSets from the time it was first seen up
through the hold-down time. It is now valid for verifying RRSets
- that arrive after the hold down time. Clarification: The DNSKEY
+ that arrive after the hold down time. Clarification: The DNSKEY
RRSet does not need to be continuously present at the resolver
(e.g. its TTL might expire). If the RRSet is seen, and is
validated (i.e. verifies against an existing trust anchor), this
- key MUST be in the RRSet otherwise a 'KeyRem' event is triggered.
+ key MUST be in the RRSet otherwise a 'KeyRem' event is triggered.
Missing This is an abnormal state. The key remains as a valid trust
point key, but was not seen at the resolver in the last validated
DNSKEY RRSet. This is an abnormal state because the zone operator
should be using the REVOKE bit prior to removal. [Discussion
- item: Should a missing key be considered revoked after some
- period of time?]
+ item: Should a missing key be considered revoked after some period
+ of time?]
Revoked This is the state a key moves to once the resolver sees an
RRSIG(DNSKEY) signed by this key where that DNSKEY RRSet contains
this key with its REVOKE bit set to '1'. Once in this state, this
key may be purged from the resolver. A key in the removed state
MUST NOT be considered a valid trust anchor.
+4.3. Trust Point Deletion
+
+ A trust point which has all of its trust anchors revoked is
+ considered deleted and is treated as if the trust point was never
+ configured. If there are no superior trust points, data at and below
+ the deleted trust point are considered insecure. If there there ARE
+ superior trust points, data at and below the deleted trust point are
+ evaluated with respect to the superior trust point.
+
+
5. Scenarios
The suggested model for operation is to have one active key and one
RRSet, but the resolver will accept it as a trust anchor if/when it
sees the signature on the trust point DNSKEY RRSet.
+
+
+
+StJohns Expires July 14, 2006 [Page 8]
+\f
+Internet-Draft trustanchor-update January 2006
+
+
Since the stand-by key is not in active signing use, the associated
private key may (and SHOULD) be provided with additional protections
not normally available to a key that must be used frequently. E.g.
but that will be dependent on operational concerns not addressed
here.
-5.1 Adding A Trust Anchor
+5.1. Adding A Trust Anchor
Assume an existing trust anchor key 'A'.
1. Generate a new key pair.
-
-
-
-
-
-StJohns Expires February 16, 2006 [Page 8]
-\f
-Internet-Draft trustanchor-update August 2005
-
-
2. Create a DNSKEY record from the key pair and set the SEP and Zone
- Key bits.
+ Key bits.
3. Add the DNSKEY to the RRSet.
4. Sign the DNSKEY RRSet ONLY with the existing trust anchor key -
'A'.
5. Wait a while.
-5.2 Deleting a Trust Anchor
+5.2. Deleting a Trust Anchor
Assume existing trust anchors 'A' and 'B' and that you want to revoke
and delete 'A'.
the RRSet for at least the remove hold-down time, but then may remove
it from the DNSKEY RRSet.
-5.3 Key Roll-Over
+5.3. Key Roll-Over
Assume existing keys A and B. 'A' is actively in use (i.e. has been
signing the DNSKEY RRSet.) 'B' was the stand-by key. (i.e. has been
2. Add 'C' to the DNSKEY RRSet.
3. Set the revocation bit on key 'A'.
4. Sign the RRSet with 'A' and 'B'.
- 'A' is now revoked, 'B' is now the active key, and 'C' will be the
+ 'A' is now revoked, 'B' is now the active key, and 'C' will be the
stand-by key once the hold-down expires. The operator SHOULD include
the revoked 'A' in the RRSet for at least the remove hold-down time,
but may then remove it from the DNSKEY RRSet.
-5.4 Active Key Compromised
+5.4. Active Key Compromised
This is the same as the mechanism for Key Roll-Over (Section 5.3)
above assuming 'A' is the active key.
-5.5 Stand-by Key Compromised
+
+
+StJohns Expires July 14, 2006 [Page 9]
+\f
+Internet-Draft trustanchor-update January 2006
+
+
+5.5. Stand-by Key Compromised
Using the same assumptions and naming conventions as Key Roll-Over
(Section 5.3) above:
included in the RRSet for the remove hold-down time.
+6. IANA Considerations
-StJohns Expires February 16, 2006 [Page 9]
-\f
-Internet-Draft trustanchor-update August 2005
+ The IANA will need to assign a bit in the DNSKEY flags field (see
+ section 4.3 of [RFC3755]) for the REVOKE bit. There are no other
+ IANA actions required.
-6. Security Considerations
+7. Security Considerations
-6.1 Key Ownership vs Acceptance Policy
+7.1. Key Ownership vs Acceptance Policy
The reader should note that, while the zone owner is responsible
creating and distributing keys, it's wholly the decision of the
will need to establish a mechanism for manual or other out-of-band
updates outside the scope of this document.
-6.2 Multiple Key Compromise
+7.2. Multiple Key Compromise
This scheme permits recovery as long as at least one valid trust
anchor key remains uncompromised. E.g. if there are three keys, you
manual or other out-of-band update of all resolvers will be required
if all trust anchor keys at a trust point are compromised.
-6.3 Dynamic Updates
+
+
+
+StJohns Expires July 14, 2006 [Page 10]
+\f
+Internet-Draft trustanchor-update January 2006
+
+
+7.3. Dynamic Updates
Allowing a resolver to update its trust anchor set based in-band key
information is potentially less secure than a manual process.
lack of a standard management framework for DNS, this approach is no
worse than the existing situation.
-7. Normative References
+8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2535] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, March 1999.
+ [RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation
+ Signer (DS)", RFC 3755, May 2004.
+
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
-
-
-StJohns Expires February 16, 2006 [Page 10]
-\f
-Internet-Draft trustanchor-update August 2005
-
-
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
at the trust anchor, they won't be able to match.
+
+
+
+
+StJohns Expires July 14, 2006 [Page 11]
+\f
+Internet-Draft trustanchor-update January 2006
+
+
Author's Address
Michael StJohns
-StJohns Expires February 16, 2006 [Page 11]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+StJohns Expires July 14, 2006 [Page 12]
\f
-Internet-Draft trustanchor-update August 2005
+Internet-Draft trustanchor-update January 2006
Intellectual Property Statement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
- The IETF has been notified of intellectual property rights claimed in
- regard to some or all of the specification contained in this
- document. For more information consult the online list of claimed
- rights.
-
Disclaimer of Validity
Copyright Statement
- Copyright (C) The Internet Society (2005). This document is subject
+ 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.
-
-
-
-StJohns Expires February 16, 2006 [Page 12]
-\f
-Internet-Draft trustanchor-update August 2005
-
-
Acknowledgment
Funding for the RFC Editor function is currently provided by the
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-StJohns Expires February 16, 2006 [Page 13]
+StJohns Expires July 14, 2006 [Page 13]
\f
projects / thirdparty / bind9.git / commitdiff
