PKIX Working Group                                            M. Myers
Internet Draft                                                VeriSign
Document: draft-ietf-pkix-cmc-trans-00.txt                      X. Liu
February 2001                                                    Cisco
Expires: July 2001                                           J. Schaad
                                                Soaring Hawk Consulting
                                                           J. Weinstein

                             CMC Transport

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

   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

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   Comments or suggestions for improvement may be made on the "ietf-
   pkix" mailing list, or directly to the author.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.


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

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in [RFC 2119].

1. Overview

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

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

   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.

   MIME TYPE                       File Extension        SMIME-TYPE

   application/pkcs10                .p10                  N/A
   (simple PKI request)

   application/pkcs7-mime            .p7m                  CMC-request
   (full PKI request)

   application/pkcs7-mime            .p7c                  certs-only
   (simple PKI response)

   application/pkcs7-mime            .p7m                  CMC-response
   (full PKI response)

4. HTTP/HTTPS based protocol

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

5. TCP based protocol

   When is the connection closed?  How is this represented?

   While this section is called TCP-Based and the messages are called
   TCP-message's, the same protocol can be used over any reliable,
   connection oriented transport protocol (e.g. SNA, DECnet, etc.).
   This protocol is suitable for cases where an end entity (or an RA)
   initiates a transaction and can poll to pick up the results.

   The length of the flags field for this version is 1 octet. The LSB
   is used to indicate a connection close; all other bits in the flags
   octet MUST be ignored by receivers, and MUST be set to zero by

   By default connections are kept open after the receipt of a
   response. Either party (client or server) MAY set the connection
   close bit at any time.  If the connection close bit is set on a
   request, then the server MUST set the bit in the response and close
   the connection after sending the response. If the bit is set on a
   response from the server, the client MUST NOT send any further
   requests on that connection. Applications MAY decide to close an
   idle connection (one on which no response is outstanding) after some
   time-out. Because of the problem where a client sends a request and
   the server closes the connection while the request is still in
   flight, clients SHOULD automatically retry a request for which no
   part of the response could be read due to a connection close or

   If the connection is kept open, it MUST only be used for subsequent
   request/response transactions started by the client - the server
   MUST NOT use it to send requests to the client. Different
   transactions may be freely interwoven on the same connection. E.g. a
   CR/CP need not immediately be followed by the Confirm, but may be
   followed by any other request from a different transaction.

7.3  Socket-Based Transport

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

9.  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.

10. Acknowledgments

   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.

11. References

   [CMS]      Housley, R., "Cryptographic Message Syntax", RFC 2630,
              June 1999.

   [CRMF]     Myers, M., Adams, C., Solo, D. and D. Kemp, "Internet
              X.509 Certificate Request Message Format", RFC 2511,

   [DH]       B. Kaliski, "PKCS 3: Diffie-Hellman Key Agreement v1.4"

   [DH-POP]   H. Prafullchandra, J. Schaad, "Diffie-Hellman Proof-of-
              Possession Algorithms", Work in Progress.

   [HMAC]     Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, February

   [PKCS1]    Kaliski, B., "PKCS #1: RSA Encryption, Version 1.5", RFC
              2313, March 1998.

   [PKCS7]    Kaliski, B., "PKCS #7: Cryptographic Message Syntax
              RFC 2315, October 1997.

   [PKCS8]    RSA Laboratories, "PKCS#8: Private-Key Information Syntax
              Standard, Version 1.2", November 1, 1993.

   [PKCS10]   Kaliski, B., "PKCS #10: Certification Request Syntax
              v1.5", RFC 2314, October 1997.

   [PKIXCERT] Housley, R., Ford, W., Polk, W. and D. Solo "Internet
              X.509 Public Key Infrastructure Certificate and CRL
              Profile", RFC 2459, January 1999.

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

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

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

   [X942]     Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC
              2631, June 1999.

12. Authors' Addresses

   Michael Myers
   TraceRoute Security, Inc.


   Xiaoyi Liu
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134

   Phone: (480) 526-7430

   Jim Schaad
   Soaring Hawk Consulting


   Jeff Weinstein


Full Copyright Statement

   Copyright (C) The Internet Society (2000).  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

   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



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