Network Working Group M. Andrews
Internet-Draft Internet Systems Consortium
Expires: December 25, 2005 S. Weiler
SPARTA, Inc.
June 23, 2005
The DNSSEC Lookaside Validation (DLV) DNS Resource Record
draft-andrews-dlv-dns-rr-00
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Copyright (C) The Internet Society (2005).
Abstract
This document defines a new DNS Resource Record, called the DNSSEC
Lookaside Validation (DLV) RR, for publishing DNSSEC trust anchors
outside of the DNS delegation chain. These records allow resolvers
to validate DNSSEC-signed data from zones whose ancestors either
aren't signed or refuse to publish DS records for their children.
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1. Introduction
DNSSEC [1] [2] [3] authenticates DNS data by building public-key
signature chains along the DNS delegation chain from a trust anchor,
ideally a trust anchor for the DNS root. Due to a myriad of
technical and political concerns, it appears unlikely that many
delegation-heavy zones, including the root and most generic top level
domains (gTLDs), will sign their zones in the near future, which
leaves DNS resolvers with no means to validate data from the children
of those zones without maintaining a large number of preconfigured
keys.
This document defines a new resource record for publishing trust
anchors outside of the DNS's normal delegation chain. Use of these
records by validators is outside the scope of this document.
2. DLV Resource Record
The DLV resource record has exactly the same wire and presentation
formats as the DS resource record, defined in RFC4034 Section 5. It
uses the same IANA-assigned values in the algorithm and digest type
fields as the DS record. (Those IANA registries are known as the
"DNS Security Algorithm Numbers" and "DS RR Type Algorithm Numbers"
registries.)
Unlike the DS record, the DLV record may not appear on the parent's
side of a zone cut. Consequently, DLV records do not require the
special processing described in section 3.1.4.1 of RFC4035. DLV
records may appear at the apex of a zone.
3. Security Considerations
Publishing DLV records introduces no security problems -- they're
just DNS data.
Users of DLV records will almost certainly want to impose constraints
on their use, but those constraints are best left to be described by
the users of the records. At a minimum, it would be wise to not use
the records without some sort of cryptographic authentication.
RFC4034 Section 8 describes security considerations specific to the
DS resource record. Those considerations are equally applicable to
DLV records. Of particular note, the key tag field is used to help
select DNSKEY resource records efficiently, but it does not uniquely
identify a single DNSKEY resource record. It is possible for two
distinct DNSKEY RRs to have the same owner name, the same algorithm
type, and the same key tag. An implementation that uses only the key
tag to select a DNSKEY RR might select the wrong public key in some
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circumstances.
For discussion of the security implications of DNSSEC see RFC4033,
RFC4034, and RFC4035.
4. IANA Considerations
IANA has assigned DNS type code X to the DLV resource record from the
Specification Required portion of the DNS Resource Record Type
registry, as defined in [4].
The DLV resource record reuses the same algorithm and digest type
registries already used for the DS resource record, currently known
as the "DNS Security Algorithm Numbers" and "DS RR Type Algorithm
Numbers" registries.
5. Normative References
[1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"DNS Security Introduction and Requirements", RFC 4033,
March 2005.
[2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"Resource Records for the DNS Security Extensions", RFC 4034,
March 2005.
[3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"Protocol Modifications for the DNS Security Extensions",
RFC 4035, March 2005.
[4] Eastlake, D., Brunner-Williams, E., and B. Manning, "Domain Name
System (DNS) IANA Considerations", BCP 42, RFC 2929,
September 2000.
Authors' Addresses
Mark Andrews
Internet Systems Consortium
950 Charter St.
Redwood City, CA 94063
US
Email: Mark_Andrews@isc.org
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Samuel Weiler
SPARTA, Inc.
7075 Samuel Morse Drive
Columbia, Maryland 21046
US
Email: weiler@tislabs.com
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