PKIX Working Group                                             J. Schaad
Internet-Draft                                   Soaring Hawk Consulting
Expires: November 13, 2006                                      M. Myers
                                               TraceRoute Security, Inc.
                                                            May 12, 2006


       Certificate Management over CMS (CMC) Transport Protocols
                    draft-ietf-pkix-cmc-trans-05.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines a number of transport mechanisms that are used
   to move CMC (Certificate Managment over CMS (Cryptographic Message
   Syntax)) messages.  The transport mechanisms described in this
   document are: HTTP, file, mail and TCP.






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1.  Overview

   This document defines a number of transport methods that are used to
   move CMC messages (defined in [CMC-STRUCT]).  The transport
   mechanisms described in this document are: HTTP, file, mail and TCP.

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


2.  File based protocol

   Enrollment messages and responses may be transferred between clients
   and servers using file system-based mechanisms, such as when
   enrollment is performed for an off-line client.  When files are used
   to transport binary, BER-encoded Full Enrollment Request and Response
   messages, there MUST be only one instance of a request or response
   message in a single file.  The following file type extensions SHOULD
   be used:

                  +-------------------+----------------+
                  | Message Type      | File Extension |
                  +-------------------+----------------+
                  | Full PKI Request  | .crq           |
                  | Full PKI Response | .crp           |
                  +-------------------+----------------+


3.  Mail based protocol

   MIME wrapping is defined for those environments that are MIME native.

   The basic mime wrapping in this section is taken from [SMIMEV2] and
   [SMIMEV3].  Simple enrollment requests are encoded using the
   "application/pkcs10" content type.  A file name MUST be included
   either in a content type or a content disposition statement.  The
   extension for the file MUST be ".p10".

   Simple enrollment response messages MUST be encoded as content-type
   "application/pkcs7-mime".  An smime-type parameter MUST be on the
   content-type statement with a value of "certs-only."  A file name
   with the ".p7c" extension MUST be specified as part of the content-
   type or content-disposition statement.

   Full enrollment request messages MUST be encoded as content-type
   "application/pkcs7-mime".  The smime-type parameter MUST be included
   with a value of "CMC-enroll".  A file name with the ".p7m" extension



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   MUST be specified as part of the content-type or content-disposition
   statement.

   Full enrollment response messages MUST be encoded as content-type
   "application/pkcs7-mime".  The smime-type parameter MUST be included
   with a value of "CMC-response."  A file name with the ".p7m"
   extensions MUST be specified as part of the content-type or content-
   disposition statement.

   +-------------+------------------------+-------------+--------------+
   | Item        | MIME TYPE              | File        | SMIME-TYPE   |
   |             |                        | Extension   |              |
   +-------------+------------------------+-------------+--------------+
   | simple      | application/pkcs10     | .p10        | N/A          |
   | request     |                        |             |              |
   | full        | applicaiton/pkcs7-mime | .p7m        | CMC-request  |
   | request     |                        |             |              |
   | simple      | application/pkcs7-mime | .p7c        | certs-only   |
   | response    |                        |             |              |
   | full        | application/pkcs7-mime | .p7m        | CMC-response |
   | response    |                        |             |              |
   +-------------+------------------------+-------------+--------------+


4.  HTTP/HTTPS based protocol

   HTTP messages are wrapped with by a mime object as specified above.


5.  TCP based protocol

   When CMC messages are sent over a TCP-Based connection, no wrapping
   is required of the message.  Messages are sent in their binary
   encoded form.

   The connection is closed by the server after generating a response
   for the client.  (All CMC request messages from client to server
   generate a response message.)  If a second set of messages from the
   client to the server is required to complete the transaction, the
   client generates a new TCP-Based connection for this purpose; it
   cannot reuse an existing one.

   Out of band setup can be used to keep a TCP-Based connection open for
   more than one message pair.  A situation where this can occur is an
   RA talking to a CA over a specially setup TCP connection.






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6.   Socket-Based Transport

   When enrollment messages and responses are sent over sockets, no
   wrapping is required.  Messages MUST be sent in their binary, BER-
   encoded form.


7.   Security Considerations

   Mechanisms for thwarting replay attacks may be required in particular
   implementations of this protocol depending on the operational
   environment.  In cases where the CA maintains significant state
   information, replay attacks may be detectable without the inclusion
   of the optional nonce mechanisms.  Implementers of this protocol need
   to carefully consider environmental conditions before choosing
   whether or not to implement the senderNonce and recipientNonce
   attributes described in section 5.6.  Developers of state-constrained
   PKI clients are strongly encouraged to incorporate the use of these
   attributes.


8.  Acknowledgments

   The authors and the Working Group are greatful for the participation
   of Xiaoui Lui and Jeff Weinstein in helping to author the original
   versions of this document.

   The authors would like to thank Brian LaMacchia for his work in
   developing and writing up many of the concepts presented in this
   document.  The authors would also like to thank Alex Deacon and Barb
   Fox for their contributions.


9.  References

9.1.  Normative References

   [CMC-STRUCT]
              Schaad, J. and M. Myers, "Certificate Management Messages
              over CMS", Work in Progress , September 2005.

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

   [SMIMEV3]  Ramsdell, B., "S/MIME Version 3 Message Specification",
              RFC 2633, June 1999.





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9.2.  Informative References

   [SMIMEV2]  Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L., and
              L. Repka, "S/MIME Version 2 Message Specification",
              RFC 2311, March 1998.














































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Authors' Addresses

   Jim Schaad
   Soaring Hawk Consulting
   PO Box 675
   Gold Bar, WA  98251

   Phone: (425) 785-1031
   Email: jimsch@exmsft.com


   Michael Myers
   TraceRoute Security, Inc.

   Email: myers@coastside.inc




































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