599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffNetwork Working Group R. Austein
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graffdraft-ietf-dnsind-sigalgopt-00.txt On Sabbatical
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Internet Software Consortium
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff DNS SIGALGOPT
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffStatus of this document
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff This document is an Internet-Draft and is in full conformance with
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff all provisions of Section 10 of RFC 2026.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Internet-Drafts are working documents of the Internet Engineering
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Task Force (IETF), its areas, and its working groups. Note that other
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff groups may also distribute working documents as Internet-Drafts.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Internet-Drafts are draft documents valid for a maximum of six months
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff and may be updated, replaced, or obsoleted by other documents at any
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff time. It is inappropriate to use Internet-Drafts as reference
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff material or to cite them other than as "work in progress."
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff The list of current Internet-Drafts can be accessed at
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff The list of Internet-Draft Shadow Directories can be accessed at
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Distribution of this document is unlimited. Please send comments to
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff the namedroppers@internic.net mailing list.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff This document describes a mechanism for conserving packet space in a
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff DNS response message in the presence of multiple DNSSEC signature
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffMotivation and Scope
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff DNSSEC [DNSSEC] specifies a general framework for attaching
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff cryptographic signatures to DNS resource records. The framework
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff includes provisions for multiple signature protocols, possibly even
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff on a per-name basis. While this open-ended framework is good and
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff useful, it poses a problem when multiple signature protocols are in
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff use and DNS message sizes are limited by the underlying UDP transport
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff packet size. EDNS0 [EDNS0] provides a way to specify a larger
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffAustein & Vixie Expires 18 April 2000 [Page 1]
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graffdraft-ietf-dnsind-sigalgopt-00.txt October 1999
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff payload size, but this still does not entirely solve the problem for
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff large RRsets. Worse, in cases where multiple signature algorithms
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff generate a response packet so large that it must be truncated, the
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff signatures that fit into the truncated response will be useless if
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff the resolver doesn't know how to verify signatures generated with
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff that algorithm.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff This note proposes a way for a resolver to indicate which signature
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff algorithms it understands to a name server in the form of an ordered
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff list. When this mechanism is in use, the name server can conserve
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff packet space by (a) not sending signatures with algorithms that the
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff resolver will not understand, and (b) not sending multiple signatures
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff for the same resource records.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff [DNSSEC] SIG RRs include a one-octet code indicating the algorithm
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff associated with a particular signature. The SIGALGOPT option defined
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff below allows the resolver to specify an ordered list of signature
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff algorithms using the same one-octet codes that DNSSEC uses.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff SIGALGOPT is encoded n the variable RDATA part of the OPT pseudo-RR
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff in the DNS request (see [EDNS0]).
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff The OPTION-CODE for SIGALGOPT is [TBD].
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff The OPTION-DATA for SIGALGOPT is an ordered list of the one-octet
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff codes used by DNSSEC.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff If the SIGALGOPT option in a query specifies multiple signature
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff algorithms and signatures using more than one of those algorithms are
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff available in the zone, the server must respond with the signatures
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff corresponding to the first algorithm on the SIGALGOPT list that
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff matches, omitting any signatures corresponding to the remaining
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff We have deliberately not provided a mechanism to return all the
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff matching signatures, because the purpose of the SIGALGOPT mechanism
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff is to minimize packet size. If the resolver wants to see all
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff available signatures, it should just leave off the SIGALGOPT option
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffSecurity Considerations
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Good question. What horrible things could a bad guy do by
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff creating/altering/deleting SIGALGOPT? Are any of the possible
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff attacks more interesting than denial of service?
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffAustein & Vixie Expires 18 April 2000 [Page 2]
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graffdraft-ietf-dnsind-sigalgopt-00.txt October 1999
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffIANA Considerations
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff SIGALGOPT will need an option code.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff The signature algorithm codes themselves are borrowed from DNSSEC and
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff do not create any new issues for IANA.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff [DNSSEC] Eastlake, D., "Domain Name System Security Extensions", RFC
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff 2535, March 1999.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff [DNS-CONCEPTS] Mockapetris, P., "Domain names - concepts and
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff facilities", RFC 1034, November 1987.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff [DNS-IMPLEMENTATION] Mockapetris, P., "Domain names - implementation
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff and specification", RFC 1035, November 1987.
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff [EDNS0] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671,
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffAuthor's addresses:
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff On Sabbatical
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff sra@hactrn.net
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Internet Software Consortium
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff 950 Charter Street
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff Redwood City, CA 94063
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff +1 650 779 7001
599c6d44f4d41aab5d3da98214492eb26e674b65Michael Graff vixie@isc.org
599c6d44f4d41aab5d3da98214492eb26e674b65Michael GraffAustein & Vixie Expires 18 April 2000 [Page 3]