draft-ietf-dnsop-dnssec-trust-anchor-02.txt   draft-ietf-dnsop-dnssec-trust-anchor-03.txt 
DNS Operations M. Larson Intended Status: Informational M. Larson
Internet-Draft VeriSign DNS Operations VeriSign
Expires: January 15, 2009 O. Gudmundsson Internet-Draft O. Gudmundsson
OGUD Consulting LLC Expires: September 10, 2009 OGUD Consulting LLC
July 14, 2008 March 9, 2009
DNSSEC Trust Anchor Configuration and Maintenance DNSSEC Trust Anchor Configuration and Maintenance
draft-ietf-dnsop-dnssec-trust-anchor-02 draft-ietf-dnsop-dnssec-trust-anchor-03
Status of this Memo Status of this Memo
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Abstract Abstract
This document recommends a preferred format for specifying trust This document recommends a preferred format for specifying trust
anchors in DNSSEC validating security-aware resolvers and describes anchors in DNSSEC validating security-aware resolvers and describes
how such a resolver should initialize trust anchors for use. This how such a resolver should initialize trust anchors for use. This
document also describes different mechanisms for keeping trust document also describes different mechanisms for keeping trust
anchors up to date over time. anchors up to date over time.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Trust Anchor Format . . . . . . . . . . . . . . . . . . . . . 4 2. Trust Anchor Format . . . . . . . . . . . . . . . . . . . . . 5
3. Trust Anchor Priming . . . . . . . . . . . . . . . . . . . . . 5 3. Trust Anchor Priming . . . . . . . . . . . . . . . . . . . . . 6
4. Trust Anchor Maintenance . . . . . . . . . . . . . . . . . . . 7 4. Trust Anchor Maintenance . . . . . . . . . . . . . . . . . . . 8
5. Security considerations . . . . . . . . . . . . . . . . . . . 9 5. Security considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. Normative References . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 14
1. Introduction 1. Introduction
The DNSSEC standards documents ([RFC4033], [RFC4034] and [RFC4035]) The DNSSEC standards documents ([RFC4033], [RFC4034] and [RFC4035])
describe the need for trust anchors and how they are used. A describe the need for trust anchors and how they are used. A
validating security-aware resolver (subsequently referred to as a validating security-aware resolver (subsequently referred to as a
"validating resolver") needs to be configured with one or more trust "validating resolver") needs to be configured with one or more trust
anchors, which specify the public keys of signed zones. To anchors, which specify the public keys of signed zones. To
authenticate DNS data, a validating resolver builds a chain of trust authenticate DNS data, a validating resolver builds a chain of trust
from a configured trust anchor to that data. from a configured trust anchor to that data.
skipping to change at page 4, line 43 skipping to change at page 6, line 5
RRSet from one of the zone's authoritative servers. It should be RRSet from one of the zone's authoritative servers. It should be
noted that in practice, priming is almost always required because noted that in practice, priming is almost always required because
data in the trust anchor zone will usually be signed with a different data in the trust anchor zone will usually be signed with a different
key than the one configured as the trust anchor, thus requiring the key than the one configured as the trust anchor, thus requiring the
validating resolver to obtain all keys in the DNSKEY RRSet. validating resolver to obtain all keys in the DNSKEY RRSet.
Using a DS format is also recommended because it is smaller than the Using a DS format is also recommended because it is smaller than the
DNSKEY format and is easier to enter manually, either by typing or DNSKEY format and is easier to enter manually, either by typing or
cutting and pasting. cutting and pasting.
Another advantage of configuring a trust anchor using a DS record is
that the entire hash of the public key in the DS RDATA need not
necessarily be specified. A validating resolver MAY support
configuration using a truncated DS hash value as a human-factors
convenience: shorter strings are easier to type and less prone to
error when entered manually. Even with a truncated hash configured,
a validating resolver can still verify that the corresponding DNSKEY
is present in the trust anchor zone's apex DNSKEY RRSet. RFC 2104
[RFC2104] offers guidance on acceptable truncation lengths.
3. Trust Anchor Priming 3. Trust Anchor Priming
A validating resolver needs to obtain and validate the DNSKEY RRSet A validating resolver needs to obtain and validate the DNSKEY RRSet
corresponding to a configured DS for that trust anchor to be usable corresponding to a configured DS for that trust anchor to be usable
in DNSSEC validation. This process is called "priming" the trust in DNSSEC validation. This process is called "priming" the trust
anchor. Priming can occur when the validating resolver starts, but a anchor. Priming can occur when the validating resolver starts, but a
validating resolver SHOULD defer priming of individual trust anchors validating resolver SHOULD defer priming of individual trust anchors
until each is first needed for verification. This priming on demand until each is first needed for verification. This priming on demand
is especially important when a validating resolver is configured with is especially important when a validating resolver is configured with
a large number of trust anchors to avoid sending a large number of a large number of trust anchors to avoid sending a large number of
skipping to change at page 5, line 48 skipping to change at page 6, line 48
found in the previous step, i.e., that there exists a valid RRSIG found in the previous step, i.e., that there exists a valid RRSIG
(cryptographically and temporally) for the DNSKEY RRSet generated (cryptographically and temporally) for the DNSKEY RRSet generated
with the private key corresponding to the DNSKEY found in the with the private key corresponding to the DNSKEY found in the
previous step. previous step.
If the validating resolver can successfully complete the steps above, If the validating resolver can successfully complete the steps above,
all DNSKEY RRs in the RRSet ought to be considered authenticated and all DNSKEY RRs in the RRSet ought to be considered authenticated and
can be used to authenticate RRSets at or below the trust anchor. can be used to authenticate RRSets at or below the trust anchor.
If any of the steps above result in an error, the validating resolver If any of the steps above result in an error, the validating resolver
SHOULD log them. SHOULD log them and abort the verification as specified in section 5
of RFC 4035 [RFC4035].
If there are multiple trust anchors configured for a zone, any one of If there are multiple trust anchors configured for a zone, any one of
them is sufficient to validate data in the zone. For this reason, them is sufficient to validate data in the zone. For this reason,
old trust anchors SHOULD be removed from a validating resolver's old trust anchors SHOULD be removed from a validating resolver's
trust anchor list soon after the corresponding keys are no longer trust anchor list soon after the corresponding keys are no longer
used by the zone. If there are multiple trust anchors configured for used by the zone. If there are multiple trust anchors configured for
a zone, any one of them is sufficient to validate data in the zone. a zone, any one of them is sufficient to validate data in the zone.
For this reason, old trust anchors SHOULD be removed from a For this reason, old trust anchors SHOULD be removed from a
validating resolver's trust anchor list soon after the corresponding validating resolver's trust anchor list soon after the corresponding
keys are no longer used by the zone, as described in RFC 5011 keys are no longer used by the zone, as described in RFC 5011
[RFC5011]. [RFC5011].
If a validating resolver is unable to retrieve a signed DNSKEY RRSet If a validating resolver is unable to retrieve a signed DNSKEY RRSet
corresponding to a trust anchor (i.e., prime the trust anchor), it corresponding to a trust anchor (i.e., prime the trust anchor), it
SHOULD log this condition as an error. Inability to prime a zone's SHOULD log this condition as an error. Inability to prime a zone's
trust anchor results in the validating resolver's inability to trust anchor results in the validating resolver's inability to
validate data from the corresponding zone. The validating resolver validate data from the corresponding zone. The validating resolver
SHOULD treat this zone as bogus. MUST treat this zone as bogus, until such time it is able to get a
DNSKEY set validated by a Trust anchor. The processing of trust
anchor and DS from parent errors MUST follow the same rules.
4. Trust Anchor Maintenance 4. Trust Anchor Maintenance
Trust anchors correspond to zones' key signing keys and these keys do Trust anchors correspond to zones' key signing keys and these keys do
change in the course of normal operation. It is up to validating change in the course of normal operation. It is up to validating
resolver operators to ensure that configured trust anchor information resolver operators to ensure that configured trust anchor information
remains current and does not go stale: each configured trust anchor remains current and does not go stale: each configured trust anchor
SHOULD correspond to a DNSKEY RR in the trust anchor zone's apex SHOULD correspond to a DNSKEY RR in the trust anchor zone's apex
DNSKEY RRSet. This process is called trust anchor maintenance. DNSKEY RRSet. This process is called trust anchor maintenance.
(Initial trust anchor configuration requires human intervention to (Initial trust anchor configuration requires human intervention to
skipping to change at page 11, line 8 skipping to change at page 12, line 8
configured to treat responses from the zone as bogus, causing configured to treat responses from the zone as bogus, causing
resolution failures. resolution failures.
6. IANA considerations 6. IANA considerations
This document does not have any IANA actions. This document does not have any IANA actions.
7. Acknowledgments 7. Acknowledgments
This work was undertaken at the suggestion of the DNSSEC Deployment This work was undertaken at the suggestion of the DNSSEC Deployment
working group (www.dnssec-deployment.org). working group (www.dnssec-deployment.org). Following people are
acknowledged for contributing to this document, Alfred Hoenes, Edward
8. References Lewis, Geoff Huston, Paul Hoffman, Matthijs Mekking, Scott Rose Paul
Wouters.
8.1. Normative References 8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, 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.
[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.
[RFC4509] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer [RFC4509] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer
(DS) Resource Records (RRs)", RFC 4509, May 2006. (DS) Resource Records (RRs)", RFC 4509, May 2006.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC) [RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", RFC 5011, September 2007. Trust Anchors", RFC 5011, September 2007.
8.2. Informative References
Authors' Addresses Authors' Addresses
Matt Larson Matt Larson
VeriSign, Inc. VeriSign, Inc.
21345 Ridgetop Circle 21345 Ridgetop Circle
Dulles, VA 20166-6503 Dulles, VA 20166-6503
USA USA
Email: mlarson@verisign.com Email: mlarson@verisign.com
Olafur Gudmundsson Olafur Gudmundsson
OGUD Consulting LLC OGUD Consulting LLC
3821 Village Park Drive 3821 Village Park Drive
Chevy Chase, MD 20815 Chevy Chase, MD 20815
USA USA
Email: ogud@ogud.com Email: ogud@ogud.com
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