DNS Extensions                                                O. Kolkman
Internet-Draft                                                  RIPE NCC
Expires: March 2, 2003                                       J. Schlyter
                                                    Carlstedt Research &
                                                              Technology
                                                          September 2002


                      KEY RR Key Signing (KS) Flag
              draft-ietf-dnsext-keyrr-key-signing-flag-01

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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-
   Drafts.

   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 http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 2, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   With the DS record [1] the concept of key signing and zone signing
   keys has been introduced.  Key signing keys are the keys that sign
   the keyset only.  In general, key signing keys are the keys that are
   pointed to by DS records and are the first keys to be used when
   following a chain of trust into the zone.  The key signing keys only
   sign the KEY RRset at the apex of a zone, zone signing keys sign all
   data in a zone.  We propose a flag to distinguish the key signing key
   from other keys in the KEY RR set during DNSSEC operations.




Kolkman & Schlyter        Expires March 2, 2003                 [Page 1]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


   The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED",
   "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be
   interpreted as described in RFC2119.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  The Key Signing Flag . . . . . . . . . . . . . . . . . . . . .  3
   3.  DNSSEC Protocol Changes  . . . . . . . . . . . . . . . . . . .  3
   4.  Operational Guidelines . . . . . . . . . . . . . . . . . . . .  4
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  4
   6.  Document Changes . . . . . . . . . . . . . . . . . . . . . . .  4
   6.1 draft version 00 -> 01 . . . . . . . . . . . . . . . . . . . .  5
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  5
       References . . . . . . . . . . . . . . . . . . . . . . . . . .  5
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  6
       Full Copyright Statement . . . . . . . . . . . . . . . . . . .  7


































Kolkman & Schlyter        Expires March 2, 2003                 [Page 2]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


1. Introduction

   "All keys are equal but some keys are more equal than others" [2]

   With the DS record [1] the concept of key signing and zone signing
   keys has been introduced.  In general these are the keys that are
   pointed to by DS records and are the first keys to be used when
   following the chain of trust into a zone ( secure entry points of the
   zone).  These key signing keys may also be configured in resolver
   systems that use zones as a trusted root[4] for a secure island.

   Early deployment tests have shown that during the key-exchange
   between the parent and the child it is useful to indicate which keys
   are to be used as the secure entry point to a zone.  We introduce the
   Key Signing Key flag to indicate this special 'administrative' status
   of the key.  The availability of the flag allows the key exchange to
   be automated where, without the flag, some additional out-of-band
   communication is needed.

2. The Key Signing Flag


                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              flags          |K|   protocol    |   algorithm   |
      |                             |S|               |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               /
      /                        public key                             /
      /                                                               /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                KEY RR Format



   The bit 15th bit (TBD) in the flags field is assigned to be the key
   signing flag.  If set the key is intended to be used as key signing
   key.  If the bit is not set, no special meaning should be assigned.
   The 15th bit is currently reserved [3].

3. DNSSEC Protocol Changes

   The use of the KS flag does not change the DNS resolution and
   resolution protocol.  The KS flag is only used to provide a hint
   about the different administrative properties and MUST NOT be used
   during the resolving process.



Kolkman & Schlyter        Expires March 2, 2003                 [Page 3]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


4. Operational Guidelines

   By setting the KS flag on a particular key, zone administrators
   indicate that that key should be used as the secure entry point for
   their zone.  Therefore zone administrators SHOULD set the bit only
   for zone keys that are used to sign the KEY RRset and are intended to
   act as the first link in the chain of trust for their zone.

   Parent zone administrators and resolver administrators that want to
   configure a keysigning key as their 'trusted key' MAY choose to
   ignore the flag.

   Using the flag a key rollover can be automated.  The parent can use
   an existing trust relation to verify keysets in which a new key with
   the KS flag appears.

   If the bit is modified during the lifetime of the key then this would
   have impact on the keytag and on the hash data in the DS RRs
   intending to point to this key.  The bit SHOULD NOT be modified once
   the key has been put into use.

5. Security Considerations

   The flag MUST NOT be used in the resolution protocol or to determine
   the security status of a key.  The flag is to be used for
   administrative purposes only.

   No trust in a key should be inferred from this flag - trust must be
   inferred from an existing chain of trust or an out-of-band exchange.

   Since this flag MAY be used for automating key exchanges, we think
   the following consideration is in place.

   Automated mechanisms for rollover of the DS RR may be vulnerable to a
   class of replay attacks.  This may happen after a key exchange where
   a keyset, containing two keys with the KS flag set, is sent to the
   parent.  The parent verifies the keyset with the existing trust
   relation and creates the new DS RR from the key that the current DS
   is not pointing to.  This key exchange may be replayed, if the parent
   does not maintain state of which DS RRs where used previously so that
   the new DS RR is replaced by the old DS RR again.  These kinds of
   attacks can be prevented by maintaining a registry of keys that have
   been used to generate DS RRs from previously.

6. Document Changes






Kolkman & Schlyter        Expires March 2, 2003                 [Page 4]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


6.1 draft version 00 -> 01

      Clean up of references and correction of typos;

      modified Abstract text a little;

      Added explicit warning for replay attacks to the security section;

      Removed the text that hinted on a distinction between a keysigning
      key configured in resolvers and in parent zones.


7. Acknowledgments

   The ideas documented in this draft are inspired by communications we
   had with numerous people and ideas published by other folk, Olafur
   Gudmundsson, Daniel Karrenberg, Dan Massey and Sam Weiler have been
   helping with providing ideas and feedback.

   This document saw the light during a workshop on DNSSEC operations
   hosted by USC/ISI.

References

   [1]  Gudmundsson, "Delegation Signer Resource Record", work in
        progress draft-ietf-dnsext-delegation-signer-08.txt, June 2002.

   [2]  Orwell, "Animal Farm; a Fairy Story"", 1945, <http://
        www.ddc.net/ygg/etext/animal.htm#10>.

   [3]  Massey and Rose, "Limiting the Scope of the KEY Resource
        Record", work in progress draft-ietf-dnsext-restrict-key-for-
        dnssec-03, June 28 2002.

   [4]  Lewis, E., "DNS Security Extension Clarification on Zone
        Status", RFC 3090, March 2001.















Kolkman & Schlyter        Expires March 2, 2003                 [Page 5]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


Authors' Addresses

   Olaf M. Kolkman
   RIPE NCC
   Singel 256
   Amsterdam  1016 AB
   NL

   Phone: +31 20 535 4444
   EMail: olaf@ripe.net
   URI:   http://www.ripe.net/


   Jakob Schlyter
   Carlstedt Research & Technology
   Stora Badhusgatan 18-20
   Goteborg  SE-411 21
   Sweden

   EMail: jakob@crt.se
   URI:   http://www.crt.se/~jakob/






























Kolkman & Schlyter        Expires March 2, 2003                 [Page 6]


Internet-Draft        KEY RR Key Signing (KS) Flag        September 2002


Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















Kolkman & Schlyter        Expires March 2, 2003                 [Page 7]