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Versions: 00 01 02 03 04 RFC 4386

   Internet Draft                                             S. Boeyen
   PKIX Working Group                                      Entrust Inc.
   Document: draft-ietf-pkix-pkixrep-04.txt             P. Hallam-Baker
   Expires: Jan 2006                                      VeriSign Inc.
   Experimental                                          September 2005


                   Internet X.509 Public Key Infrastructure
                           Repository Locator Service
                      <draft-ietf-pkix-pkixrep-04.txt>

Status of this Memo

   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
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   This Internet-Draft will expire in Jan 2006. Comments should be sent
   to the PKIX mail list at:  ietf-pkix@imc.org.

   By submitting this Internet-Draft, each author represents that any
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   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

Abstract

   This document defines a PKI repository locator service. The service
   makes use of DNS SRV records defined in accordance with RFC 2782. The
   service enables certificate using systems to locate PKI repositories




Conventions used in this document





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   The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
   "RECOMMENDED", "MAY", and "OPTIONAL" in this document (in uppercase,
   as shown) are to be interpreted as described in [RFC2119].

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.

Table of Contents

   1. Overview.......................................................2
   2. SRV RR definition..............................................2
      2.1 Assignment of new protocol prefixes........................3
      2.2 Use of multiple repositories...............................3
      2.3 SRV RR example.............................................3
   3. Security considerations........................................4
   4. IANA Considerations............................................4
   Copyright.........................................................4
   References........................................................5
   Author's Addresses................................................5

1.   Overview

   Operational protocols have been specified for retrieval of PKI data,
   including public-key certificates and revocation information, from
   PKI repositories in a number of RFCs including RFC 2559, RFC 2560
   and RFC 2585. These RFCs assume that a certificate using system has
   the knowledge information necessary to identify, locate and connect
   to the PKI repository with a specific protocol. Although there are
   some tools available in protocol-specific environments for this
   purpose, such as knowledge references in directory systems, these are
   restricted to use with a single protocol and do not share a common
   means of publication. This draft provides a solution to this problem
   through the use of SRV RRs in DNS. This solution is expected to be
   particularly useful in environments where only a domain name is
   available. In other situations (e.g. where a certificate is available
   that contains the required information), such a DNS lookup is not
   needed.

   RFC 2782 defines a DNS RR for specifying the location of services
   (SRV). This Internet-draft defines SRV records for a PKI repository
   locator service to enable PKI clients to obtain the necessary
   information to connect to a domain's PKI repository, including
   information about each protocol that is supported by that domain for
   access to its repository. This Internet-draft includes the definition
   of a SRV RR format for this service and an example of its potential
   use in an email environment.

2.   SRV RR definition



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   The format of the SRV RR, whose DNS type code is 33, is:

    _Service._Proto.Name TTL Class SRV Priority Weight Port Target

   For the PKI repository locator service, this draft uses the symbolic
   name "PKIXREP". Note that when used in an SRV RR, this name MUST
   be prepended with a "_" character.

   The protocols that can be included in PKIXREP SRV RRs are:

      Protocol     SRV Prefix

      LDAP         _LDAP
      HTTP         _HTTP
      OCSP         _OCSP

2.1     Assignment of new protocol prefixes

   Protocol prefix assignments for new PKIX repository protocols SHOULD
   be defined in the document that specifies the protocol.

2.2     Use of multiple repositories

   The existence of multiple repositories MAY be determined by making
   separate DNS queries for each of the protocols supported by the
   client.

   If this approach is found to be unacceptably inefficient due to a
   proliferation of repository protocols at a future date the service
   discovery protocol could be extended to allow the repository to
   advertise the protocols supported.

2.3     SRV RR example

   This example uses fictional domain "example.com" as an aid in
   understanding the use of SRV records by a certificate using system.

   Let an email client that needs a certificate for a recipient be Alice
   and assume that Alice's client system supports LDAP for certificate
   retrieval. Let the message recipient be Bob and let Bob's email
   address be bob@example.com. Assume that example.test maintains a
   "border directory" PKI repository and that Bob's certificate is
   available from that directory "border.example.com" via LDAP.

   Alice's client system retrieves, via DNS, the SRV record for
   _PKIXREP._LDAP.example.com.

        - the QNAME of the DNS query is _PKIXREP._LDAP.example.com
        - the QCLASS of the DNS query is IN


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        - the QTYPE of the DNS query is SRV

   The result SHOULD include the host address for example.com's border
   directory system.

   Note that if example.com operated their service on a number of hosts,
   more than one SRV RR would be returned. In this case, RFC 2782
   defines the procedure to be followed in determining which of these
   should be accessed first.

3.   Security considerations

   Security issues regarding PKI repositories themselves are outside the
   scope of this specification. For LDAP repositories, for example,
   specific security considerations are addressed in RFC 2559.

   Security issues with respect to the use of SRV records in general are
   addressed in RFC 2782 and these issues apply to the use of SRV
   records in the context of the PKIXREP service defined here.

4.   IANA Considerations

   This document reserves the use of "_PKIXREP" Service label. Since
   this relates to a service which may pass messages over a number of
   different message transports, they must be associated with a specific
   transport.

   In order to ensure that the association between "_PKIXREP" and their
   respective underlying services is deterministic, this document
   requests that IANA create a registry: The PKIX SRV Protocol Label.

   For this registry, an entry shall consist of a label name and a
   pointer to a specification describing how the protocol named in the
   label uses SRV. Specifications should conform to the requirements
   listed in RFC 2434 for "specification required".

Copyright

   Copyright (C) The Internet Society (2005).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights."

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE


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   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


References

   [RFC 2119] Bradner, S., "Keywords for use in RFCs to indicate
              requirement levels, March 1997.

   [RFC 2782] Gulbrandsen, A. Vixie, P. and Esibov, L., "A DNS RR for
              specifying the location of services (DNS SRV)", Feb 2000.

   [RFC 2559] Boeyen, S. Howes, T. and Richard, P., "Internet X.509
              Public Key Infrastructure Operational Protocols - LDAPv2",
              April 1999.

   [RFC 2560] Myers, M. Ankney, R. Malpani, A. Galperin, S. and Adams, C.
              "Internet X.509 Public Key Infrastructure Online Certificate
              Status Protocol - OCSP", June 1999.

   RFC 2585] Housley, R. and Hoffman, P. "Internet X.509 Public Key
             Infrastructure Operational Protocols: FTP and HTTP",
             May, 1999.

   RFC 2434] Narten, T. and Alvestrand, H. "Guidelines for Writing an
             IANA Considerations Section in RFCs", RFC 2434, BCP 26,
             October 1998.

Author's Addresses

   Sharon Boeyen
   Entrust
   1000 Innovation Drive
   Ottawa, Ontario
   Canada K2K 3E7
   email: sharon.boeyen@entrust.com

   Phillip M. Hallam-Baker
   VeriSign Inc.
   401 Edgewater Place, Suite 280
   Wakefield MA 01880
   email: pbaker@VeriSign.com









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