draft-ietf-dnsext-dnssec-bis-updates-05.txt   draft-ietf-dnsext-dnssec-bis-updates-06.txt 
Network Working Group S. Weiler Network Working Group S. Weiler
Internet-Draft SPARTA, Inc Internet-Draft SPARTA, Inc.
Updates: 4034, 4035 R. Austein Updates: 4034, 4035 R. Austein
(if approved) ISC (if approved) ISC
Expires: September 5, 2007 March 4, 2007 Expires: May 22, 2008 November 19, 2007
Clarifications and Implementation Notes for DNSSECbis Clarifications and Implementation Notes for DNSSECbis
draft-ietf-dnsext-dnssec-bis-updates-05 draft-ietf-dnsext-dnssec-bis-updates-06
Status of this Memo Status of this Memo
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This Internet-Draft will expire on September 5, 2007. This Internet-Draft will expire on May 22, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document is a collection of minor technical clarifications to This document is a collection of minor technical clarifications to
the DNSSECbis document set. It is meant to serve as a resource to the DNSSECbis document set. It is meant to serve as a resource to
implementors as well as an interim repository of DNSSECbis errata. implementors as well as an interim repository of DNSSECbis errata.
Table of Contents Table of Contents
1. Introduction and Terminology . . . . . . . . . . . . . . . . . 3 1. Introduction and Terminology . . . . . . . . . . . . . . . . . 3
1.1. Structure of this Document . . . . . . . . . . . . . . . . 3 1.1. Structure of this Document . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Significant Concerns . . . . . . . . . . . . . . . . . . . . . 3 2. Significant Concerns . . . . . . . . . . . . . . . . . . . . . 3
2.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 3 2.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 3
2.2. Validating Responses to an ANY Query . . . . . . . . . . . 4 2.2. Validating Responses to an ANY Query . . . . . . . . . . . 4
2.3. Check for CNAMEa . . . . . . . . . . . . . . . . . . . . . 4 2.3. Check for CNAME . . . . . . . . . . . . . . . . . . . . . 4
3. Interoperability Concerns . . . . . . . . . . . . . . . . . . 4 2.4. Unsecure Delegation Proofs . . . . . . . . . . . . . . . . 4
3.1. Unknown DS Message Digest Algorithms . . . . . . . . . . . 4 2.5. Errors in Canonical Form Type Code List . . . . . . . . . 4
3. Interoperability Concerns . . . . . . . . . . . . . . . . . . 5
3.1. Unknown DS Message Digest Algorithms . . . . . . . . . . . 5
3.2. Private Algorithms . . . . . . . . . . . . . . . . . . . . 5 3.2. Private Algorithms . . . . . . . . . . . . . . . . . . . . 5
3.3. Caution About Local Policy and Multiple RRSIGs . . . . . . 5 3.3. Caution About Local Policy and Multiple RRSIGs . . . . . . 6
3.4. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 6 3.4. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 6
3.5. Setting the DO Bit on Replies . . . . . . . . . . . . . . 6 3.5. Setting the DO Bit on Replies . . . . . . . . . . . . . . 6
4. Minor Corrections and Clarifications . . . . . . . . . . . . . 6 4. Minor Corrections and Clarifications . . . . . . . . . . . . . 7
4.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 6 4.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 7
4.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 6 4.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 7
4.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 7 4.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 7
4.4. Errors in Canonical Form Type Code List . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 9 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 11
1. Introduction and Terminology 1. Introduction and Terminology
This document lists some minor clarifications and corrections to This document lists some minor clarifications and corrections to
DNSSECbis, as described in [RFC4033], [RFC4034], and [RFC4035]. DNSSECbis, as described in [RFC4033], [RFC4034], and [RFC4035].
It is intended to serve as a resource for implementors and as a It is intended to serve as a resource for implementors and as a
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2. Significant Concerns 2. Significant Concerns
This section provides clarifications that, if overlooked, could lead This section provides clarifications that, if overlooked, could lead
to security issues or major interoperability problems. to security issues or major interoperability problems.
2.1. Clarifications on Non-Existence Proofs 2.1. Clarifications on Non-Existence Proofs
[RFC4035] Section 5.4 slightly underspecifies the algorithm for [RFC4035] Section 5.4 slightly underspecifies the algorithm for
checking non-existence proofs. In particular, the algorithm there checking non-existence proofs. In particular, the algorithm there
might incorrectly allow the NSEC from an ancestor zone to prove the might incorrectly allow the NSEC from an ancestor zone to prove the
non-existence of either other RRs at that name in the child zone or non-existence of other RRs at that name in the child zone or other
other names in the child zone. It might also allow a NSEC at the names in the child zone. It might also allow a NSEC at the same name
same name as a DNAME to prove the non-existence of names beneath that as a DNAME to prove the non-existence of names beneath that DNAME.
DNAME.
An ancestor delegation NSEC (one with the NS bit set, but no SOA bit An ancestor delegation NSEC (one with the NS bit set, but no SOA bit
set, and with a singer field that's shorter than the owner name) must set, and with a signer field that's shorter than the owner name) MUST
not be used to assume non-existence of any RRs below that zone cut NOT be used to assume non-existence of any RRs below that zone cut
(both RRs at that ownername and at ownernames with more leading (both RRs at that ownername and at ownernames with more leading
labels, no matter their content). Similarly, an NSEC with the DNAME labels, no matter their content). Similarly, an NSEC with the DNAME
bit set must not be used to assume the non-existence of any bit set must not be used to assume the non-existence of any subdomain
descendant of that NSEC's owner name. of that NSEC's owner name.
2.2. Validating Responses to an ANY Query 2.2. Validating Responses to an ANY Query
[RFC4035] does not address how to validate responses when QTYPE=*. [RFC4035] does not address how to validate responses when QTYPE=*.
As described in Section 6.2.2 of [RFC1034], a proper response to As described in Section 6.2.2 of [RFC1034], a proper response to
QTYPE=* may include a subset of the RRsets at a given name -- it is QTYPE=* may include a subset of the RRsets at a given name -- it is
not necessary to include all RRsets at the QNAME in the response. not necessary to include all RRsets at the QNAME in the response.
When validating a response to QTYPE=*, validate all received RRsets When validating a response to QTYPE=*, validate all received RRsets
that match QNAME and QCLASS. If any of those RRsets fail validation, that match QNAME and QCLASS. If any of those RRsets fail validation,
treat the answer as Bogus. If there are no RRsets matching QNAME and treat the answer as Bogus. If there are no RRsets matching QNAME and
QCLASS, validate that fact using the rules in [RFC4035] Section 5.4 QCLASS, validate that fact using the rules in [RFC4035] Section 5.4
(as clarified in this document). To be clear, a validator must not (as clarified in this document). To be clear, a validator must not
insist on receiving all records at the QNAME in response to QTYPE=*. expect to receive all records at the QNAME in response to QTYPE=*.
2.3. Check for CNAMEa 2.3. Check for CNAME
Section 5 of [RFC4035] says little about validating responses based Section 5 of [RFC4035] says little about validating responses based
on (or that should be based on) CNAMEs. When validating a NODATA on (or that should be based on) CNAMEs. When validating a NODATA
response, it's important to check the CNAME bit in the NSEC bitmap. response, it's important to check the CNAME bit in the NSEC bitmap.
If the CNAME bit is set, the validator MUST validate the CNAME RR and If the CNAME bit is set, the validator MUST validate the CNAME RR and
follow it, as appropriate. follow it, as appropriate.
2.4. Unsecure Delegation Proofs
[RFC4035] Section 5.2 specifies that a validator, when proving a
delegation is unsecure, needs to check for the absence of the DS and
SOA bits in the NSEC type bitmap. The validator also needs to check
for the presence of the NS bit in the NSEC RR (proving that there is,
indeed, a delegation). If this is not checked, spoofed unsigned
delegations might be used to claim that an existing signed record is
not signed.
2.5. Errors in Canonical Form Type Code List
When canonicalizing DNS names, DNS names in the RDATA section of NSEC
and RRSIG resource records are not downcased.
[RFC4034] Section 6.2 item 3 has a list of resource record types for
which DNS names in the RDATA are downcased for purposes of DNSSEC
canonical form (for both ordering and signing). That list
erroneously contains NSEC and RRSIG. According to [RFC3755], DNS
names in the RDATA of NSEC and RRSIG should not be downcased.
The same section also lists HINFO twice. The implementor is
encouraged to exercise good discretion and professional judgment when
deciding whether to downcase such DNS names once or twice. [RFC3597]
contained the same error and, since it predated RFC3755, it doesn't
mention RRSIG or NSEC.
3. Interoperability Concerns 3. Interoperability Concerns
3.1. Unknown DS Message Digest Algorithms 3.1. Unknown DS Message Digest Algorithms
Section 5.2 of [RFC4035] includes rules for how to handle delegations Section 5.2 of [RFC4035] includes rules for how to handle delegations
to zones that are signed with entirely unsupported algorithms, as to zones that are signed with entirely unsupported algorithms, as
indicated by the algorithms shown in those zone's DS RRsets. It does indicated by the algorithms shown in those zone's DS RRsets. It does
not explicitly address how to handle DS records that use unsupported not explicitly address how to handle DS records that use unsupported
message digest algorithms. In brief, DS records using unknown or message digest algorithms. In brief, DS records using unknown or
unsupported message digest algorithms MUST be treated the same way as unsupported message digest algorithms MUST be treated the same way as
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functions, as discussed in Section 3.1). In these cases, the functions, as discussed in Section 3.1). In these cases, the
resolver MUST retrieve the corresponding DNSKEY for each private resolver MUST retrieve the corresponding DNSKEY for each private
algorithm DS record and examine the public key field to determine the algorithm DS record and examine the public key field to determine the
algorithm in use. The security-aware resolver MUST ensure that the algorithm in use. The security-aware resolver MUST ensure that the
hash of the DNSKEY RR's owner name and RDATA matches the digest in hash of the DNSKEY RR's owner name and RDATA matches the digest in
the DS RR. If they do not match, and no other DS establishes that the DS RR. If they do not match, and no other DS establishes that
the zone is secure, the referral should be considered BAD data, as the zone is secure, the referral should be considered BAD data, as
discussed in [RFC4035]. discussed in [RFC4035].
This clarification facilitates the broader use of private algorithms, This clarification facilitates the broader use of private algorithms,
as suggested by [I-D.ietf-dnsext-dnssec-experiments]. as suggested by [RFC4955].
3.3. Caution About Local Policy and Multiple RRSIGs 3.3. Caution About Local Policy and Multiple RRSIGs
When multiple RRSIGs cover a given RRset, [RFC4035] Section 5.3.3 When multiple RRSIGs cover a given RRset, [RFC4035] Section 5.3.3
suggests that "the local resolver security policy determines whether suggests that "the local resolver security policy determines whether
the resolver also has to test these RRSIG RRs and how to resolve the resolver also has to test these RRSIG RRs and how to resolve
conflicts if these RRSIG RRs lead to differing results." In most conflicts if these RRSIG RRs lead to differing results." In most
cases, a resolver would be well advised to accept any valid RRSIG as cases, a resolver would be well advised to accept any valid RRSIG as
sufficient. If the first RRSIG tested fails validation, a resolver sufficient. If the first RRSIG tested fails validation, a resolver
would be well advised to try others, giving a successful validation would be well advised to try others, giving a successful validation
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field value of 3 indicates that the answer was not the result of field value of 3 indicates that the answer was not the result of
wildcard expansion. This is true for "x.w.example" but not for wildcard expansion. This is true for "x.w.example" but not for
"x.w.example.com", which of course has a label count of 4 "x.w.example.com", which of course has a label count of 4
(antithetically, a label count of 3 would imply the answer was the (antithetically, a label count of 3 would imply the answer was the
result of a wildcard expansion). result of a wildcard expansion).
The first paragraph of [RFC4035] Section C.6 also has a minor error: The first paragraph of [RFC4035] Section C.6 also has a minor error:
the reference to "a.z.w.w.example" should instead be "a.z.w.example", the reference to "a.z.w.w.example" should instead be "a.z.w.example",
as in the previous line. as in the previous line.
4.4. Errors in Canonical Form Type Code List
[RFC4034] Section 6.2 item 3 has a list of resource record types for
which DNS names in the RDATA are downcased for purposes of DNSSEC
canonical form (for both ordering and signing). That list contains
HINFO twice. The implementor is encouraged to exercise good
discretion and professional judgement when deciding whether to
downcase such DNS names once or twice.
Further, it is worth noting that the list of RR types in [RFC3597]
has the same bug and, as could be expected, doesn't include RRSIG or
NSEC.
5. IANA Considerations 5. IANA Considerations
This document specifies no IANA Actions. This document specifies no IANA Actions.
6. Security Considerations 6. Security Considerations
This document does not make fundamental changes to the DNSSEC This document does not make fundamental changes to the DNSSEC
protocol, as it was generally understood when DNSSECbis was protocol, as it was generally understood when DNSSECbis was
published. It does, however, address some ambiguities and omissions published. It does, however, address some ambiguities and omissions
in those documents that, if not recognized and addressed in in those documents that, if not recognized and addressed in
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[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005. RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005. RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005. Extensions", RFC 4035, March 2005.
7.2. Informative References 7.2. Informative References
[I-D.ietf-dnsext-dnssec-experiments]
Blacka, D., "DNSSEC Experiments",
draft-ietf-dnsext-dnssec-experiments-03 (work in
progress), April 2006.
[I-D.ietf-dnsext-nsec3]
Laurie, B., "DNSSEC Hashed Authenticated Denial of
Existence", draft-ietf-dnsext-nsec3-09 (work in progress),
January 2007.
[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, September 2003. (RR) Types", RFC 3597, September 2003.
[RFC4470] Weiler, S. and J. Ihren, "Minimally Covering NSEC Records [RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation
and DNSSEC On-line Signing", RFC 4470, April 2006. Signer (DS)", RFC 3755, May 2004.
[RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices",
RFC 4641, September 2006. RFC 4641, September 2006.
[RFC4955] Blacka, D., "DNS Security (DNSSEC) Experiments", RFC 4955,
July 2007.
Appendix A. Acknowledgments Appendix A. Acknowledgments
The editors are extremely grateful to those who, in addition to The editors are extremely grateful to those who, in addition to
finding errors and omissions in the DNSSECbis document set, have finding errors and omissions in the DNSSECbis document set, have
provided text suitable for inclusion in this document. provided text suitable for inclusion in this document.
The lack of specificity about handling private algorithms, as The lack of specificity about handling private algorithms, as
described in Section 3.2, and the lack of specificity in handling ANY described in Section 3.2, and the lack of specificity in handling ANY
queries, as described in Section 2.2, were discovered by David queries, as described in Section 2.2, were discovered by David
Blacka. Blacka.
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Section 3.4, was found by Abhijit Hayatnagarkar. Donald Eastlake Section 3.4, was found by Abhijit Hayatnagarkar. Donald Eastlake
contributed text for Section 3.4. contributed text for Section 3.4.
The bug relating to delegation NSEC RR's in Section 2.1 was found by The bug relating to delegation NSEC RR's in Section 2.1 was found by
Roy Badami. Roy Arends found the related problem with DNAME. Roy Badami. Roy Arends found the related problem with DNAME.
The errors in the [RFC4035] examples were found by Roy Arends, who The errors in the [RFC4035] examples were found by Roy Arends, who
also contributed text for Section 4.3 of this document. also contributed text for Section 4.3 of this document.
The editors would like to thank Ed Lewis, Danny Mayer, Olafur The editors would like to thank Ed Lewis, Danny Mayer, Olafur
Gudmundsson, and Scott Rose for their substantive comments on the Gudmundsson, Suzanne Woolf, and Scott Rose for their substantive
text of this document. comments on the text of this document.
Authors' Addresses Authors' Addresses
Samuel Weiler Samuel Weiler
SPARTA, Inc SPARTA, Inc.
7110 Samuel Morse Drive 7110 Samuel Morse Drive
Columbia, Maryland 21046 Columbia, Maryland 21046
US US
Email: weiler@tislabs.com Email: weiler@tislabs.com
Rob Austein Rob Austein
ISC ISC
950 Charter Street 950 Charter Street
Redwood City, CA 94063 Redwood City, CA 94063
USA USA
Email: sra@isc.org Email: sra@isc.org
Full Copyright Statement Full Copyright Statement
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