draft-ietf-dnsext-dnssec-bis-updates-08.txt   draft-ietf-dnsext-dnssec-bis-updates-09.txt 
Network Working Group S. Weiler Network Working Group S. Weiler
Internet-Draft SPARTA, Inc. Internet-Draft SPARTA, Inc.
Updates: 4033, 4034, 4035, 5155 D. Blacka Updates: 4033, 4034, 4035, 5155 D. Blacka
(if approved) VeriSign, Inc. (if approved) VeriSign, Inc.
Intended status: Standards Track January 14, 2009 Intended status: Standards Track September 5, 2009
Expires: July 18, 2009 Expires: March 9, 2010
Clarifications and Implementation Notes for DNSSECbis Clarifications and Implementation Notes for DNSSECbis
draft-ietf-dnsext-dnssec-bis-updates-08 draft-ietf-dnsext-dnssec-bis-updates-09
Status of this Memo Status of this Memo
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skipping to change at page 1, line 34 skipping to change at page 1, line 34
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This Internet-Draft will expire on July 18, 2009. This Internet-Draft will expire on March 9, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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to this document.
Abstract Abstract
This document is a collection of technical clarifications to the This document is a collection of technical clarifications to the
DNSSECbis document set. It is meant to serve as a resource to DNSSECbis document set. It is meant to serve as a resource to
implementors as well as a repository of DNSSECbis errata. implementors as well as a 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. Important Additions to DNSSSECbis . . . . . . . . . . . . . . 3 2. Important Additions to DNSSSECbis . . . . . . . . . . . . . . 3
2.1. NSEC3 Support . . . . . . . . . . . . . . . . . . . . . . 3 2.1. NSEC3 Support . . . . . . . . . . . . . . . . . . . . . . 3
2.2. SHA-256 Support . . . . . . . . . . . . . . . . . . . . . 3 2.2. SHA-256 Support . . . . . . . . . . . . . . . . . . . . . 3
3. Significant Concerns . . . . . . . . . . . . . . . . . . . . . 4 3. Security Concerns . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 4 3.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 4
3.2. Validating Responses to an ANY Query . . . . . . . . . . . 4 3.2. Validating Responses to an ANY Query . . . . . . . . . . . 4
3.3. Check for CNAME . . . . . . . . . . . . . . . . . . . . . 5 3.3. Check for CNAME . . . . . . . . . . . . . . . . . . . . . 5
3.4. Insecure Delegation Proofs . . . . . . . . . . . . . . . . 5 3.4. Insecure Delegation Proofs . . . . . . . . . . . . . . . . 5
3.5. Errors in Canonical Form Type Code List . . . . . . . . . 5
4. Interoperability Concerns . . . . . . . . . . . . . . . . . . 5 4. Interoperability Concerns . . . . . . . . . . . . . . . . . . 5
4.1. Unknown DS Message Digest Algorithms . . . . . . . . . . . 5 4.1. Errors in Canonical Form Type Code List . . . . . . . . . 5
4.2. Private Algorithms . . . . . . . . . . . . . . . . . . . . 6 4.2. Unknown DS Message Digest Algorithms . . . . . . . . . . . 5
4.3. Caution About Local Policy and Multiple RRSIGs . . . . . . 6 4.3. Private Algorithms . . . . . . . . . . . . . . . . . . . . 6
4.4. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 7 4.4. Caution About Local Policy and Multiple RRSIGs . . . . . . 7
4.5. Setting the DO Bit on Replies . . . . . . . . . . . . . . 7 4.5. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 7
4.6. Setting the AD bit on Replies . . . . . . . . . . . . . . 7 4.6. Setting the DO Bit on Replies . . . . . . . . . . . . . . 7
4.7. Setting the CD bit on Requests . . . . . . . . . . . . . . 8 4.7. Setting the AD bit on Replies . . . . . . . . . . . . . . 7
4.8. Nested Trust Anchors . . . . . . . . . . . . . . . . . . . 8 4.8. Setting the CD bit on Requests . . . . . . . . . . . . . . 8
4.9. Nested Trust Anchors . . . . . . . . . . . . . . . . . . . 8
5. Minor Corrections and Clarifications . . . . . . . . . . . . . 8 5. Minor Corrections and Clarifications . . . . . . . . . . . . . 8
5.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 8 5.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 8
5.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 8 5.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 9
5.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 9 5.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 9
5.4. Errors in RFC 5155 . . . . . . . . . . . . . . . . . . . . 9 5.4. Errors in RFC 5155 . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 11 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction and Terminology 1. Introduction and Terminology
This document lists some clarifications and corrections to DNSSECbis, This document lists some additions, clarifications and corrections to
as described in [RFC4033], [RFC4034], and [RFC4035]. the core DNSSECbis specification, as originally 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
repository of items that need to be addressed when advancing the repository of items that need to be addressed when advancing the
DNSSECbis documents from Proposed Standard to Draft Standard. DNSSECbis documents from Proposed Standard to Draft Standard.
1.1. Structure of this Document 1.1. Structure of this Document
The clarifications to DNSSECbis are sorted according to their The clarifications to DNSSECbis are sorted according to their
importance, starting with ones which could, if ignored, lead to importance, starting with ones which could, if ignored, lead to
security and stability problems and progressing down to security problems and progressing down to clarifications that are
clarifications that are expected to have little operational impact. expected to have little operational impact.
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Important Additions to DNSSSECbis 2. Important Additions to DNSSSECbis
This section provides This section updates the set of core DNSSEC protocol documents
originally specified in Section 10 of [RFC4033].
2.1. NSEC3 Support 2.1. NSEC3 Support
[RFC5155] describes the use and behavior of the NSEC3 and NSEC3PARAM [RFC5155] describes the use and behavior of the NSEC3 and NSEC3PARAM
records for hashed denial of existence. Validator implementations records for hashed denial of existence. Validator implementations
are strongly encouraged to include support for NSEC3 as a number of are strongly encouraged to include support for NSEC3 because a number
highly visible zones are expected to use it. Validators that do not of highly visible zones are expected to use it. Validators that do
support validation of responses using NSEC3 will likely be hampered not support validation of responses using NSEC3 will likely be
in validating large portions of the DNS space. hampered in validating large portions of the DNS space.
[RFC5155] should be considered part of the DNS Security Document [RFC5155] should be considered part of the DNS Security Document
Family as described by [RFC4033], Section 10. Family as described by [RFC4033], Section 10.
2.2. SHA-256 Support 2.2. SHA-256 Support
[RFC4509] describes the use of SHA-256 as a digest algorithm for use [RFC4509] describes the use of SHA-256 as a digest algorithm for use
with Delegation Signer (DS) RRs. [I-D.ietf-dnsext-dnssec-rsasha256] with Delegation Signer (DS) RRs. [I-D.ietf-dnsext-dnssec-rsasha256]
describes the use of the RSASHA256 algorthim for use in DNSKEY and describes the use of the RSASHA256 algorithm for use in DNSKEY and
RRSIG RRs. Validator implementations are strongly encouraged to RRSIG RRs. Validator implementations are strongly encouraged to
include support for this algorithm for DS, DNSKEY, and RRSIG records. include support for this algorithm for DS, DNSKEY, and RRSIG records.
Both [RFC4509] and [I-D.ietf-dnsext-dnssec-rsasha256] should also be Both [RFC4509] and [I-D.ietf-dnsext-dnssec-rsasha256] should also be
considered part of the DNS Security Document Family as described by considered part of the DNS Security Document Family as described by
[RFC4033], Section 10. [RFC4033], Section 10.
3. Significant Concerns 3. Security 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.
3.1. Clarifications on Non-Existence Proofs 3.1. Clarifications on Non-Existence Proofs
[RFC4035] Section 5.4 underspecifies the algorithm for checking non- [RFC4035] Section 5.4 under-specifies the algorithm for checking non-
existence proofs. In particular, the algorithm as presented would existence proofs. In particular, the algorithm as presented would
incorrectly allow an NSEC or NSEC3 RR from an ancestor zone to prove incorrectly allow an NSEC or NSEC3 RR from an ancestor zone to prove
the non-existence of other RRs at that name in the child zone or the non-existence of RRs in the child zone.
other names in the child zone.
An "ancestor delegation" NSEC RR (or NSEC3 RR) is one with: An "ancestor delegation" NSEC RR (or NSEC3 RR) is one with:
o the NS bit set, o the NS bit set,
o the SOA bit clear, and o the SOA bit clear, and
o a signer field that is shorter than the owner name of the NSEC RR, o a signer field that is shorter than the owner name of the NSEC RR,
or the original owner name for the NSEC3 RR. or the original owner name for the NSEC3 RR.
Ancestor delegation NSEC or NSEC3 RRs MUST NOT be used to assume non- Ancestor delegation NSEC or NSEC3 RRs MUST NOT be used to assume non-
existence of any RRs below that zone cut, which include all RRs at existence of any RRs below that zone cut, which include all RRs at
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owner name as a DNAME RR, or an NSEC3 RR at the same original owner owner name as a DNAME RR, or an NSEC3 RR at the same original owner
name as a DNAME, to prove the non-existence of names beneath that name as a DNAME, to prove the non-existence of names beneath that
DNAME. An NSEC or NSEC3 RR with the DNAME bit set MUST NOT be used DNAME. An NSEC or NSEC3 RR with the DNAME bit set MUST NOT be used
to assume the non-existence of any subdomain of that NSEC/NSEC3 RR's to assume the non-existence of any subdomain of that NSEC/NSEC3 RR's
(original) owner name. (original) owner name.
3.2. Validating Responses to an ANY Query 3.2. 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. That is,
not necessary to include all RRsets at the QNAME in the response. it is 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=*, all received RRsets that match
that match QNAME and QCLASS. If any of those RRsets fail validation, QNAME and QCLASS MUST be validated. If any of those RRsets fail
treat the answer as Bogus. If there are no RRsets matching QNAME and validation, the answer is considered Bogus. If there are no RRsets
QCLASS, validate that fact using the rules in [RFC4035] Section 5.4 matching QNAME and QCLASS, that fact MUST be validated according to
(as clarified in this document). To be clear, a validator must not the rules in [RFC4035] Section 5.4 (as clarified in this document).
expect to receive all records at the QNAME in response to QTYPE=*. To be clear, a validator must not expect to receive all records at
the QNAME in response to QTYPE=*.
3.3. Check for CNAME 3.3. 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 NOERROR/ on (or that should be based on) CNAMEs. When validating a NOERROR/
NODATA response, validators MUST check the CNAME bit in the matching NODATA response, validators MUST check the CNAME bit in the matching
NSEC or NSEC3 RR's type bitmap. If the CNAME bit is set, the NSEC or NSEC3 RR's type bitmap in addition to the bit for the query
validator MUST validate the CNAME RR and follow it, as appropriate. type. Without this check, an attacker could successfully transform a
positive CNAME response into a NOERROR/NODATA response.
3.4. Insecure Delegation Proofs 3.4. Insecure Delegation Proofs
[RFC4035] Section 5.2 specifies that a validator, when proving a [RFC4035] Section 5.2 specifies that a validator, when proving a
delegation is not secure, needs to check for the absence of the DS delegation is not secure, needs to check for the absence of the DS
and SOA bits in the NSEC (or NSEC3) type bitmap. The validator also and SOA bits in the NSEC (or NSEC3) type bitmap. The validator also
needs to check for the presence of the NS bit in the NSEC (or NSEC3) needs to check for the presence of the NS bit in the matching NSEC
RR (proving that there is, indeed, a delegation). If this is not (or NSEC3) RR (proving that there is, indeed, a delegation), or
checked, spoofed unsigned delegations might be used to claim that an alternately make sure that the delegation is covered by an NSEC3 RR
existing signed record is not signed. with the Opt-Out flag set. If this is not checked, spoofed unsigned
delegations might be used to claim that an existing signed record is
not signed.
3.5. Errors in Canonical Form Type Code List 4. Interoperability Concerns
4.1. Errors in Canonical Form Type Code List
When canonicalizing DNS names, DNS names in the RDATA section of NSEC When canonicalizing DNS names, DNS names in the RDATA section of NSEC
and RRSIG resource records are not downcased. and RRSIG resource records are not downcased.
[RFC4034] Section 6.2 item 3 has a list of resource record types for [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 which DNS names in the RDATA are downcased for purposes of DNSSEC
canonical form (for both ordering and signing). That list canonical form (for both ordering and signing). That list
erroneously contains NSEC and RRSIG. According to [RFC3755], DNS erroneously contains NSEC and RRSIG. According to [RFC3755], DNS
names in the RDATA of NSEC and RRSIG should not be downcased. names in the RDATA of NSEC and RRSIG should not be downcased.
The same section also erroneously lists HINFO, and twice at that. The same section also erroneously lists HINFO, and twice at that.
Since HINFO records contain no domain names, they are not subject to Since HINFO records contain no domain names, they are not subject to
downcasing. downcasing.
4. Interoperability Concerns 4.2. Unknown DS Message Digest Algorithms
4.1. 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 public key
indicated by the algorithms shown in those zone's DS RRsets. It does algorithms, as indicated by the key algorithms shown in those zone's
not explicitly address how to handle DS records that use unsupported DS RRsets. It does not explicitly address how to handle DS records
message digest algorithms. In brief, DS records using unknown or that use unsupported message digest algorithms. In brief, DS records
unsupported message digest algorithms MUST be treated the same way as using unknown or unsupported message digest algorithms MUST be
DS records referring to DNSKEY RRs of unknown or unsupported treated the same way as DS records referring to DNSKEY RRs of unknown
algorithms. or unsupported public key algorithms.
The existing text says: The existing text says:
If the validator does not support any of the algorithms listed in If the validator does not support any of the algorithms listed in
an authenticated DS RRset, then the resolver has no supported an authenticated DS RRset, then the resolver has no supported
authentication path leading from the parent to the child. The authentication path leading from the parent to the child. The
resolver should treat this case as it would the case of an resolver should treat this case as it would the case of an
authenticated NSEC RRset proving that no DS RRset exists, as authenticated NSEC RRset proving that no DS RRset exists, as
described above. described above.
To paraphrase the above, when determining the security status of a To paraphrase the above, when determining the security status of a
zone, a validator discards (for this purpose only) any DS records zone, a validator disregards any DS records listing unknown or
listing unknown or unsupported algorithms. If none are left, the unsupported algorithms. If none are left, the zone is treated as if
zone is treated as if it were unsigned. it were unsigned.
Modified to consider DS message digest algorithms, a validator also Modified to consider DS message digest algorithms, a validator also
discards any DS records using unknown or unsupported message digest disregards any DS records using unknown or unsupported message digest
algorithms. algorithms.
4.2. Private Algorithms 4.3. Private Algorithms
As discussed above, section 5.2 of [RFC4035] requires that validators As discussed above, section 5.2 of [RFC4035] requires that validators
make decisions about the security status of zones based on the public make decisions about the security status of zones based on the public
key algorithms shown in the DS records for those zones. In the case key algorithms shown in the DS records for those zones. In the case
of private algorithms, as described in [RFC4034] Appendix A.1.1, the of private algorithms, as described in [RFC4034] Appendix A.1.1, the
eight-bit algorithm field in the DS RR is not conclusive about what eight-bit algorithm field in the DS RR is not conclusive about what
algorithm(s) is actually in use. algorithm(s) is actually in use.
If no private algorithms appear in the DS set or if any supported If no private algorithms appear in the DS set or if any supported
algorithm appears in the DS set, no special processing will be algorithm appears in the DS set, no special processing will be
needed. In the remaining cases, the security status of the zone needed. In the remaining cases, the security status of the zone
depends on whether or not the resolver supports any of the private depends on whether or not the resolver supports any of the private
algorithms in use (provided that these DS records use supported hash algorithms in use (provided that these DS records use supported hash
functions, as discussed in Section 4.1). In these cases, the functions, as discussed in Section 4.2). 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 Bogus 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 [RFC4955]. as suggested by [RFC4955].
4.3. Caution About Local Policy and Multiple RRSIGs 4.4. 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
result if any can be validated and giving a failure only if all result if any can be validated and giving a failure only if all
RRSIGs fail validation. RRSIGs fail validation.
If a resolver adopts a more restrictive policy, there's a danger that If a resolver adopts a more restrictive policy, there's a danger that
properly-signed data might unnecessarily fail validation, perhaps properly-signed data might unnecessarily fail validation, perhaps
because of cache timing issues. Furthermore, certain zone management because of cache timing issues. Furthermore, certain zone management
techniques, like the Double Signature Zone-signing Key Rollover techniques, like the Double Signature Zone-signing Key Rollover
method described in section 4.2.1.2 of [RFC4641] might not work method described in section 4.2.1.2 of [RFC4641] might not work
reliably. reliably.
4.4. Key Tag Calculation 4.5. Key Tag Calculation
[RFC4034] Appendix B.1 incorrectly defines the Key Tag field [RFC4034] Appendix B.1 incorrectly defines the Key Tag field
calculation for algorithm 1. It correctly says that the Key Tag is calculation for algorithm 1. It correctly says that the Key Tag is
the most significant 16 of the least significant 24 bits of the the most significant 16 of the least significant 24 bits of the
public key modulus. However, [RFC4034] then goes on to incorrectly public key modulus. However, [RFC4034] then goes on to incorrectly
say that this is 4th to last and 3rd to last octets of the public key say that this is 4th to last and 3rd to last octets of the public key
modulus. It is, in fact, the 3rd to last and 2nd to last octets. modulus. It is, in fact, the 3rd to last and 2nd to last octets.
4.5. Setting the DO Bit on Replies 4.6. Setting the DO Bit on Replies
[RFC4035] does not provide any instructions to servers as to how to [RFC4035] does not provide any instructions to servers as to how to
set the DO bit. Some authoritative server implementations have set the DO bit. Some authoritative server implementations have
chosen to copy the DO bit settings from the incoming query to the chosen to copy the DO bit settings from the incoming query to the
outgoing response. Others have chosen to never set the DO bit in outgoing response. Others have chosen to never set the DO bit in
responses. Either behavior is permitted. To be clear, in replies to responses. Either behavior is permitted. To be clear, in replies to
queries with the DO-bit set servers may or may not set the DO bit. queries with the DO-bit set servers may or may not set the DO bit.
4.6. Setting the AD bit on Replies 4.7. Setting the AD bit on Replies
Section 3.2.3 of [RFC4035] describes under which conditions a Section 3.2.3 of [RFC4035] describes under which conditions a
validating resolver should set or clear the AD bit in a response. In validating resolver should set or clear the AD bit in a response. In
order to protect legacy stub resolvers and middleboxes, validating order to protect legacy stub resolvers and middleboxes, validating
resolvers SHOULD only set the AD bit when a response both meets the resolvers SHOULD only set the AD bit when a response both meets the
conditions listed in RFC 4035, section 3.2.3, and the request conditions listed in RFC 4035, section 3.2.3, and the request
contained either a set DO bit or a set AD bit. contained either a set DO bit or a set AD bit.
Note that the use of the AD bit in the query was previously Note that the use of the AD bit in the query was previously
undefined. This document defines it as a signal indicating that the undefined. This document defines it as a signal indicating that the
requester understands and is interested in the value of the AD bit in requester understands and is interested in the value of the AD bit in
the response. This allows a requestor to indicate that it the response. This allows a requestor to indicate that it
understands the AD bit without also requesting DNSSEC data via the DO understands the AD bit without also requesting DNSSEC data via the DO
bit. bit.
4.7. Setting the CD bit on Requests 4.8. Setting the CD bit on Requests
When processing a request with the CD bit set, the resolver MUST set When processing a request with the CD bit set, the resolver MUST set
the CD bit on its upstream queries. the CD bit on its upstream queries.
4.8. Nested Trust Anchors 4.9. Nested Trust Anchors
A DNSSEC validator may be configured such that, for a given response, A DNSSEC validator may be configured such that, for a given response,
more than one trust anchor could be used to validate the chain of more than one trust anchor could be used to validate the chain of
trust to the response zone. For example, imagine a validor trust to the response zone. For example, imagine a validator
configured with trust anchors for "example." and "zone.example." configured with trust anchors for "example." and "zone.example."
When the validator is asked to validate a response to When the validator is asked to validate a response to
"www.sub.zone.example.", either trust anchor could apply. "www.sub.zone.example.", either trust anchor could apply.
When presented with this situation, DNSSEC validators SHOULD try all When presented with this situation, DNSSEC validators SHOULD try all
applicable trust anchors until one succeeds. applicable trust anchors until one succeeds.
There are some scenarios where different behaviors, such as choosing There are some scenarios where different behaviors, such as choosing
the trust anchor closest to the QNAME of the response, may be the trust anchor closest to the QNAME of the response, may be
desired. A DNSSEC validator MAY enable such behaviors as desired. A DNSSEC validator MAY enable such behaviors as
skipping to change at page 9, line 35 skipping to change at page 9, line 46
"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.
5.4. Errors in RFC 5155 5.4. Errors in RFC 5155
A NSEC3 record, that matches an Empty Non-Terminal, effectively has A NSEC3 record that matches an Empty Non-Terminal effectively has no
no type associated with it. This NSEC3 record has an empty type bit type associated with it. This NSEC3 record has an empty type bit
map. Section 3.2.1 of [RFC5155] contains the statement: map. Section 3.2.1 of [RFC5155] contains the statement:
Blocks with no types present MUST NOT be included. Blocks with no types present MUST NOT be included.
However, the same section contains a regular expression: However, the same section contains a regular expression:
Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )+ Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )+
The plus sign in the regular expression indicates that there is one The plus sign in the regular expression indicates that there is one
or more of the preceding element. This means that there must be at or more of the preceding element. This means that there must be at
skipping to change at page 10, line 13 skipping to change at page 10, line 21
RFC 5155 3.2.1 should be: RFC 5155 3.2.1 should be:
Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )* Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )*
6. IANA Considerations 6. IANA Considerations
This document specifies no IANA Actions. This document specifies no IANA Actions.
7. Security Considerations 7. Security Considerations
This document does not make fundamental changes to the DNSSEC This document adds two cryptographic features to the core DNSSEC
protocol, as it was generally understood when DNSSECbis was protocol. Additionally, it addresses some ambiguities and omissions
published. It does, however, address some ambiguities and omissions in the core DNSSEC documents that, if not recognized and addressed in
in those documents that, if not recognized and addressed in
implementations, could lead to security failures. In particular, the implementations, could lead to security failures. In particular, the
validation algorithm clarifications in Section 3 are critical for validation algorithm clarifications in Section 3 are critical for
preserving the security properties DNSSEC offers. Furthermore, preserving the security properties DNSSEC offers. Furthermore,
failure to address some of the interoperability concerns in Section 4 failure to address some of the interoperability concerns in Section 4
could limit the ability to later change or expand DNSSEC, including could limit the ability to later change or expand DNSSEC, including
by adding new algorithms. adding new algorithms.
8. References 8. References
8.1. Normative References 8.1. Normative References
[I-D.ietf-dnsext-dnssec-rsasha256] [I-D.ietf-dnsext-dnssec-rsasha256]
Jansen, J., "Use of SHA-2 algorithms with RSA in DNSKEY Jansen, J., "Use of SHA-2 algorithms with RSA in DNSKEY
and RRSIG Resource Records for DNSSEC", and RRSIG Resource Records for DNSSEC",
draft-ietf-dnsext-dnssec-rsasha256-10 (work in progress), draft-ietf-dnsext-dnssec-rsasha256-14 (work in progress),
January 2009. June 2009.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
RFC 1034, STD 13, November 1987. RFC 1034, STD 13, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997. Requirement Levels", RFC 2119, BCP 14, March 1997.
[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.
skipping to change at page 11, line 34 skipping to change at page 11, line 41
Appendix A. Acknowledgments Appendix A. Acknowledgments
The editors would like the thank Rob Austein for his previous work as The editors would like the thank Rob Austein for his previous work as
an editor of this document. an editor of this document.
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 4.2, and the lack of specificity in handling ANY described in Section 4.3, and the lack of specificity in handling ANY
queries, as described in Section 3.2, were discovered by David queries, as described in Section 3.2, were discovered by David
Blacka. Blacka.
The error in algorithm 1 key tag calculation, as described in The error in algorithm 1 key tag calculation, as described in
Section 4.4, was found by Abhijit Hayatnagarkar. Donald Eastlake Section 4.5, was found by Abhijit Hayatnagarkar. Donald Eastlake
contributed text for Section 4.4. contributed text for Section 4.5.
The bug relating to delegation NSEC RR's in Section 3.1 was found by The bug relating to delegation NSEC RR's in Section 3.1 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 5.3 of this document. also contributed text for Section 5.3 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, Suzanne Woolf, and Scott Rose for their substantive Gudmundsson, Suzanne Woolf, and Scott Rose for their substantive
comments on the text of this document. comments on the text of this document.
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