Internet Draft S. Boeyen PKIX Working Group Entrust Technologies July 2000 P. Hallam-Baker Expires in January 2001 VeriSign Inc. Internet X.509 Public Key Infrastructure Repository Locator Service 1 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 in January 2001. Comments should be sent to the PKIX mail list at: ietf-pkix@imc.org. 1.1 Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. 2 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 based on a domain name, identify the protocols that can be used to access the repository, and obtain addresses for the servers that host the repository service. 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]. 3 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 Boeyen & Hallam-Baker Expires January 2001 [Page 1] 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 defininition of a SRV RR format for this service and an example of its potential use in an email environment. 4 SRV RR definition 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: LDAP HTTP OCSP Note that when these protocol names appear in SRV records, they MUST be prepended by a "_" character. Other protocols could be added in future. System administrators SHOULD create at least one PKIXREP SRV RR for each protocol that can be used to access their service. If the service is operated on a number of hosts, additional records can be created, as described in RFC 2782. 4.1 SRV RR example This example uses fictional domain "example.test" 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.test. Assume that example.test maintains a "border directory" PKI repository and that Bob's Boeyen & Hallam-Baker Expires January 2001 [Page 2] certificate is available from that directory "border.example.test" via LDAP. Alice's client system retrieves, via DNS, the SRV record for _PKIXREP._LDAP.example.test. - the QNAME of the DNS query is _PKIXREP._LDAP.example.test - the QCLASS of the DNS query is IN - the QTYPE of the DNS query is SRV The result SHOULD include the host address for example.test's border directory system. Note that if example.test 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. 5 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. 6 References RFC 2119: Keywords for use in RFCs to indicate requirement levels. RFC 2782: A DNS RR for specifying the location of services (DNS SRV) RFC 2559: Internet X.509 Public Key Infrastructure Operational Protocols - LDAPv2 RFC 2560: Internet X.509 Public Key Infrastructure Online Certificate Status Protocol - OCSP RFC 2585: Internet X.509 Public Key Infrastructure Operational Protocols: FTP and HTTP 7 Authors' Addresses Sharon Boeyen Entrust Technologies 750 Heron Road, Suite 0800 Ottawa, Ontario Canada K1V 1A7 email: sharon.boeyen@entrust.com Phillip M. Hallam-Baker VeriSign Inc. 401 Edgewater Place, Suite 280 Wakefield MA 01880 email: pbaker@VeriSign.com Boeyen & Hallam-Baker Expires January 2001 [Page 3]