Internet Draft                              Ronald Tschal„r (Trustpoint)
PKIX Working Group                              Amit Kapoor (Trustpoint)
Expires in 6 months                Carlisle Adams (Entrust Technologies)
                                                               Aug. 1999


                  Using HTTP as a Transport Protocol for CMP
                      <draft-ietf-pkix-cmp-http-00.txt>


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
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  Internet-Drafts.

  Internet-Drafts are draft documents valid for a maximum of six
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  reference material or to cite them other than as "work in progress."

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  The list of Internet-Draft Shadow Directories can be accessed at
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  This Internet-Draft will expire on February 5, 2000


Copyright Notice

  Copyright (C)The Internet Society (1999). All Rights Reserved.


Abstract

  This document describes how to layer [CMP] over [HTTP]. A simple method
  for doing so is described in section 5.4 of [CMP], but that method does
  not accommodate a polling mechanism, which may be required in some
  environments. This document specifies an alternative method which uses
  the polling protocol defined in section 5.2 of [CMP]. A new Content-Type
  for messages is also defined.

  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].


1. Motivation

  Section 5.4 of the CMP spec specifies sending the DER-encoded CMP
  message directly over HTTP. However, because the method described there
  does not define a polling mechanism, the server is required to send a
  final response immediately.  This may be impossible for environments in
  which manual intervention is needed in the registration/certification
  process (and, for practical reasons, a connection cannot be left open
  indefinitely until the manual activity is complete). On the other hand,
  section 5.2 of [CMP] defines a simple protocol over TCP that allows
  polling. This protocol can be used over HTTP in a straightforward way,
  solving the above problem and simplifying implementations that support
  multiple protocols.


2. Specification

  A client creates a "direct TCP-based PKI message", henceforth referred
  to simply as "message", as specified in section 5.2 of [CMP]. The
  message is then sent as the entity-body of an HTTP POST request. If the
  HTTP request is successful then the server returns a similar message
  in the body of the response. The response status code in this case
  MUST be 200; other 2xx codes MUST NOT be used. The content type of the
  request and response MUST be "application/pkixcmp-poll". Content
  codings may be applied.

  Note that a server may return any 1xx, 3xx, 4xx, or 5xx code if the
  HTTP request needs further handling or is otherwise not acceptable.


3. Discussion

  The protocol defined in section 5.2 of [CMP] provides a means for
  letting the client poll for the response. It also defines a response
  for every request, which maps well onto HTTP's request-response
  nature. By using the exact same messages as section 5.2, client and
  server implementations that handle CMP messages over both TCP and HTTP
  are simplified.

  A new content type is introduced so as to avoid confusion with the
  protocol defined in section 5.4 of [CMP]. It is recommended that the
  section 5.4 specification be phased out in favour of the one described in
  this document.

  Because in general CMP message are not cacheable, requests and
  responses should include a "Cache-Control: no-cache" (and, if either
  side uses HTTP/1.0, a "Pragma: no-cache") to prevent the client from
  getting cached responses. This is especially important for polling
  requests and responses.


4. Security Considerations

  No new security considerations with respect to [CMP] are introduced.


References

  [CMP]     Adams, C., Farrell, S., "Internet X.509 Public Key
            Infrastructure, Certificate Management Protocols", RFC 2510,
            March 1999.

  [HTTP]    Fielding, R.T., et. al, "Hypertext Transfer Protocol --
            HTTP/1.1", RFC 2616, June 1999.

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


Authors' Addresses

  Amit Kapoor
  Trustpoint
  429 Castro Street, Suite B
  Mountain View, CA 94041
  US

  E-Mail: amit@trustpoint.com

  Ronald Tschal„r
  Trustpoint
  429 Castro Street, Suite B
  Mountain View, CA 94041
  US

  E-Mail: ronald@trustpoint.com

  Carlisle Adams
  Entrust Technologies
  750 Heron Road, Suite E08,
  Ottawa, Ontario
  Canada K1V 1A7

  E-Mail: cadams@entrust.com


Appendix A: Registration of MIME Type for Section 2

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/pkixcmp-poll

   MIME media type name: application

   MIME subtype name: pkixcmp-poll

   Required parameters: none

   Optional parameters: none

   Encoding considerations:
   Content may contain arbitrary octet values (the ASN.1 DER encoding of
   a PKI message, as defined in the IETF PKIX Working Group
   specifications).  base64 encoding is required for MIME e-mail; no
   encoding is necessary for HTTP.

   Security considerations:
   This MIME type may be used to transport Public-Key Infrastructure
   (PKI) messages between PKI entities.  These messages are defined by
   the IETF PKIX Working Group and are used to establish and maintain an
   Internet X.509 PKI.  There is no requirement for specific security
   mechanisms to be applied at this level if the PKI messages themselves
   are protected as defined in the PKIX specifications.

   Interoperability considerations: -

   Published specification: this document

   Applications which use this media type:
   Applications using certificate management, operational, or ancillary
   protocols (as defined by the IETF PKIX Working Group) to send PKI
   messages via e-mail or HTTP.

   Additional information:

     Magic number (s): -
     File extension (s): ".PKI"
     Macintosh File Type Code (s): -

   Person and email address to contact for further information:
   Carlisle Adams, cadams@entrust.com

   Intended usage: COMMON

   Author/Change controller: Carlisle Adams



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