Internet DRAFT - draft-wijngaards-dnsext-trust-history


DNS Extensions Working Group                               W. Wijngaards
Internet-Draft                                                NLnet Labs
Intended status: Standards Track                           June 30, 2009
Expires: January 1, 2010

                  DNSSEC Trust Anchor History Service

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on January 1, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.


   When DNS validators have trusted keys, but have been offline for a
   longer period, key rollover will fail and they are stuck with stale
   trust anchors.  History service allows validators to query for older

Wijngaards               Expires January 1, 2010                [Page 1]
Internet-Draft            Trust History Service                June 2009

   DNSKEY RRsets and pick up the rollover trail where they left off.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.  Introduction

   DNSSEC [RFC4034] validators that have been offline or have missed an
   (emergency) rollover can use trust history service to get back on
   track.  The trust history location is assumed available from the
   validator configuration.  The validator then fetches old DNSKEY
   RRsets and checks they form a chain to the latest key.

   Providers of trust history can fetch the DNSKEY data as published by
   the zone they track, and copy-and-paste it.  They need not sign nor
   hold private keys safe.  The algorithms for this are explained below.

2.  Trust History Lookup

   The algorithm is in steps.  The TALINK RR type is defined below.

   Step 1.  The validator performs a DNSKEY lookup to the target zone,
   which looks like any other initial DNSKEY lookup for a trust anchor.
   If the keyset verifies with the trust anchor currently held, the
   keyset already works.  Otherwise, store this result, the further
   algorithm either ends with this result or fails.

   Step 2.  Fetch the trust history list end points.  Query type TALINK
   to the location configured for trust history.

   Step 3.  Go backwards through the trust history list.  Verify that
   the keyset validly signs the next keyset.  This is [RFC4034]
   validation, but the RRSIG expiration date is ignored.  Replace the
   owner domain name with the target zone name for verification.  One of
   the keys that signs the next keyset MUST have the SEP bit set.  Query
   type TALINK to get previous and next locations.

   If all SEP keys have the REVOKE flag set at this step, and the keyset
   is signed by all SEP keys, then continue but store that the end
   result is that the trust point is deleted, see Section 5 [RFC5011].

   Step 4.  When the trust anchor currently held by the validator
   verifies the keyset, the algorithm is done.  The validator SHOULD
   store the result on stable storage.  Use the new trust anchor for
   validation (if using [RFC5011], put it in state VALID).

Wijngaards               Expires January 1, 2010                [Page 2]
Internet-Draft            Trust History Service                June 2009

3.  Trust History Tracker

   The tracker polls the target zone DNSKEY RRset regularly.  Ignore
   date changes in the RRSIG.  Ignore changes to keys with no SEP flag.

   Copy the newly polled DNSKEY RRset and RRSIGs, change the owner name
   to a new name at the history location.  Publish the new RRset and
   TALINK records to make it the last element in the list.

   The list is stored as the DNS Resource Record type TALINK (decimal
   TBD).  The rdata consists of two domain names.  The first name is the
   start, or previous name, and the other name the end or next name in
   the list.  The root label '.' is used at the endpoints of the list.

   The presentation format is the two domain names.  The wire encoding
   is the two domain names, with no compression so the type can be
   treated according to [RFC3597].  The list is a double linked list,
   because this empowers low memory hosts to perform consistency checks.

4.  Example

   In this example provides trust history for  The DNSKEY rdata and RRSIG rdata is omitted for
   brevity, it is a copy and paste of the data from


   h0 TALINK .
   h0 DNSKEY ...
   h0 RRSIG ...

   h1 TALINK
   h1 DNSKEY ...
   h1 RRSIG ...

   h2 TALINK .
   h2 DNSKEY ...
   h2 RRSIG ...

5.  Security Considerations

   The trust history tracker only provides a cached copy of old data.
   The history data can be altered or withheld; the lookup algorithm
   then fails.

   The security depends on the key that the validator is holding, and
   the keys in the chain up to the present.  If the old key held by the

Wijngaards               Expires January 1, 2010                [Page 3]
Internet-Draft            Trust History Service                June 2009

   validator is too old, the validator MAY not accept this risk, and
   then SHOULD perform out of band key priming.

   If a validator is also using RFC5011 for the target zone, then the
   trust history algorithm SHOULD only be invoked if the last RFC5011
   successful probe was more than 30 days ago.  If a new key has been
   announced, invoke the history if no 2 probes succeeded during the add
   hold-down time and there was no successful probe after the add hold-
   down time passed.  Therefore the time of the last successful probe
   MUST be stored on stable storage.

   The algorithm looks up the initial DNSKEY like other validators do,
   and then walks the history in reverse.  This avoids exposing the
   validator on the network as a host with an older key and the key id.

   The SEP bit is checked to make sure that control over the KSK is
   necessary to change the keyset for the target zone.

6.  IANA Considerations

   Resource record type TALINK should refer to this RFC, it has RR type
   number TBD (decimal) [by dnsext expert review].

7.  References

7.1.  Informative References

   [RFC5011]  StJohns, M., "Automated Updates of DNS Security (DNSSEC)
              Trust Anchors", RFC 5011, September 2007.

7.2.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, September 2003.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, March 2005.

Wijngaards               Expires January 1, 2010                [Page 4]
Internet-Draft            Trust History Service                June 2009

Author's Address

   Wouter Wijngaards
   NLnet Labs
   Science Park 140
   Amsterdam  1098 XG
   The Netherlands

   Phone: +31-20-888-4551

Wijngaards               Expires January 1, 2010                [Page 5]