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Certificate Management over CMS (CMC): Transport Protocols
draft-ietf-lamps-rfc5273bis-01

Document Type Active Internet-Draft (lamps WG)
Authors Joe Mandel , Sean Turner
Last updated 2024-09-29
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draft-ietf-lamps-rfc5273bis-01
LAMPS Working Group                                        J. Mandel, Ed
Internet-Draft                                              AKAYLA, Inc.
Obsoletes: 5273, 6402 (if approved)                        S. Turner, Ed
Intended status: Standards Track                                   sn3rd
Expires: 2 April 2025                                  29 September 2024

       Certificate Management over CMS (CMC): Transport Protocols
                     draft-ietf-lamps-rfc5273bis-01

Abstract

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

   This document obsoletes RFCs 5273 and 6402.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-lamps-rfc5273bis/.

   Discussion of this document takes place on the WG LAMPS mailing list
   (mailto:spasm@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/spasm/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/spasm/.

   Source for this draft and an issue tracker can be found at
   https://github.com/seanturner/cmcbis.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

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   This Internet-Draft will expire on 2 April 2025.

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   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   This document may contain material from IETF Documents or IETF
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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Terminology  . . . . . . . . . . . . . . . . . .   3
   3.  Changes Since 5273 and 6402 . . . . . . . . . . . . . . . . .   3
   4.  File-Based Protocol . . . . . . . . . . . . . . . . . . . . .   4
   5.  Mail-Based Protocol . . . . . . . . . . . . . . . . . . . . .   4
   6.  HTTP/HTTPS-Based Protocol . . . . . . . . . . . . . . . . . .   5
     6.1.  PKI Request . . . . . . . . . . . . . . . . . . . . . . .   6
     6.2.  PKI Response  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  TCP-Based Protocol  . . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   9
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

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1.  Introduction

   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.

   This document obsoletes [CMC-TRANSv1] and [CMC-Updates].  This
   document also incorporates [erratum3593].

2.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Changes Since 5273 and 6402

      |  Note: For now, this section will be list of the changes
      |  introduced by each version.  After WGLC, this section will be
      |  finalized.

   TODO for -03:

   *  Consider AuthEnvelopedData

   *  Added requirements to follow BCP 195

   -02 version changes:

   *  Replaced TLS 1.0 with TLS 1.2 or later

   -01 version changes:

   *  Changed RFC 5272 references to draft-mandel-lamps-rfc5272bis

   *  Merged [erratum3593]

   -00 version changes:

   *  Moved 2119-text to its own section

   *  Added "Changes Since 5273 and 6402" section

   *  Updated references

   *  Merged [CMC-Updates] text

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   *  Updated and moved Acknowledgments

4.  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, Full PKI Request or Full PKI 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 |
                 +=====================+================+
                 | Simple PKI Request  | .p10           |
                 +---------------------+----------------+
                 | Full PKI Request    | .crq           |
                 +---------------------+----------------+
                 | Simple PKI Response | .p7c           |
                 +---------------------+----------------+
                 | Full PKI Response   | .crp           |
                 +---------------------+----------------+

                    Table 1: File PKI Request/Response
                              Identification

5.  Mail-Based Protocol

   MIME wrapping is defined for those environments that are MIME native.
   The basic mime wrapping in this section is taken from [SMIMEV4].
   When using a mail-based protocol, MIME wrapping between the layers of
   CMS wrapping is optional.  Note that this is different from the
   standard S/MIME (Secure MIME) message.

   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.

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   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-request".  A file name with the ".p7m" extension
   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"
   extension MUST be specified as part of the content-type or content-
   disposition statement.

   +====================+==============+================+==============+
   | Item               | MIME Type    | File Extension | SMIME Type   |
   +====================+==============+================+==============+
   | Simple PKI         | application/ | .p10           | N/A          |
   | Request            | pkcs10       |                |              |
   +--------------------+--------------+----------------+--------------+
   | Full PKI           | application/ | .p7m           | CMC-request  |
   | Request            | pkcs7-mime   |                |              |
   +--------------------+--------------+----------------+--------------+
   | Simple PKI         | application/ | .p7c           | certs-only   |
   | Response           | pkcs7-mime   |                |              |
   +--------------------+--------------+----------------+--------------+
   | Full PKI           | application/ | .p7m           | CMC-response |
   | Response           | pkcs7-mime   |                |              |
   +--------------------+--------------+----------------+--------------+

             Table 2: MIME PKI Request/Response Identification

6.  HTTP/HTTPS-Based Protocol

   This section describes the conventions for use of HTTP [HTTP] as a
   transport layer.  In most circumstances, the use of HTTP over TLS
   [HTTP] provides any necessary content protection from eavesdroppers.

   In order for CMC clients and servers using HTTP to interoperate, the
   following rules apply.

      Clients MUST use the POST method to submit their requests.

      Servers MUST use the 200 response code for successful responses.

      Clients MAY attempt to send HTTP requests using TLS 1.2 [TLS] or
      later, although servers are not required to support TLS.  If TLS
      1.2 [TLS] (or later) is used then implementations MUST follow the
      recommendations in [BCP195].

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      Servers MUST NOT assume client support for any type of HTTP
      authentication such as cookies, Basic authentication, or Digest
      authentication.

      Clients and servers are expected to follow the other rules and
      restrictions in [HTTP].  Note that some of those rules are for
      HTTP methods other than POST; clearly, only the rules that apply
      to POST are relevant for this specification.

6.1.  PKI Request

   A PKI Request using the POST method is constructed as follows:

   The Content-Type header MUST have the appropriate value from Table 2.

   The body of the message is the binary value of the encoding of the
   PKI Request.

6.2.  PKI Response

   An HTTP-based PKI Response is composed of the appropriate HTTP
   headers, followed by the binary value of the BER (Basic Encoding
   Rules) encoding of either a Simple or Full PKI Response.

   The Content-Type header MUST have the appropriate value from Table 2.

7.  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 client closes a connection after receiving a response, or it
   issues another request to the server using the same connection.
   Reusing one connection for multiple successive requests, instead of
   opening multiple connections that are only used for a single request,
   is RECOMMENDED for performance and resource conservation reasons.  A
   server MAY close a connection after it has been idle for some period
   of time; this timeout would typically be several minutes long.

   CMC requires a registered port number to send and receive CMC
   messages over TCP.  The title of this IP Protocol number is "pkix-
   cmc".  The value of this TCP port is 5318.

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   Prior to [CMC-Updates], CMC did not have a registered port number and
   used an externally configured port from the Private Port range.
   Client implementations MAY want to continue to allow for this to
   occur.  Servers SHOULD change to use the new port.  It is expected
   that HTTP will continue to be the primary transport method used by
   CMC installations.

8.  IANA Considerations

   IANA has assigned a TCP port number in the Registered Port Number
   range for the use of CMC.

     Service name: pkix-cmc
     Port Number: 5318
     Transport protocol: TCP
     Description: PKIX Certificate Management using CMS (CMC)
     Reference: RFC 6402
     Assignee: iesg@ietf.org
     Contact: chair@ietf.org

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 Certification Authority (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 6.6 of [CMC-STRUCT].  Developers of state-constrained PKI
   clients are strongly encouraged to incorporate the use of these
   attributes.

   Initiation of a secure communications channel between an end-entity
   and a CA or Registration Authority (RA) -- and, similarly, between an
   RA and another RA or CA -- necessarily requires an out-of-band trust
   initiation mechanism.  For example, a secure channel may be
   constructed between the end-entity and the CA via IPsec [IPsec] or
   TLS [TLS].  Many such schemes exist, and the choice of any particular
   scheme for trust initiation is outside the scope of this document.
   Implementers of this protocol are strongly encouraged to consider
   generally accepted principles of secure key management when
   integrating this capability within an overall security architecture.

   In some instances, no prior out-of-band trust will have been
   initiated prior to use of this protocol.  This can occur when the
   protocol itself is being used to download onto the system the set of

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   trust anchors to be used for these protocols.  In these instances,
   the Enveloped Data content type (Section 3.2.1.3.3 of [CMC-STRUCT])
   must be used to provide the same shrouding that TLS would have
   provided.

10.  References

10.1.  Normative References

   [BCP195]   Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/rfc/rfc9325>.

   [CMC-STRUCT]
              Mandel, J. and S. Turner, "Certificate Management over CMS
              (CMC)", Work in Progress, Internet-Draft, draft-ietf-
              lamps-rfc5272bis-01, 29 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
              rfc5272bis-01>.

   [erratum3593]
              "RFC 5273 erratum 3593", April 2013,
              <https://www.rfc-editor.org/errata/eid3593>.

   [HTTP]     Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9110>.

   [IPsec]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/rfc/rfc4301>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [SMIMEV4]  Schaad, J., Ramsdell, B., and S. Turner, "Secure/
              Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
              Message Specification", RFC 8551, DOI 10.17487/RFC8551,
              April 2019, <https://www.rfc-editor.org/rfc/rfc8551>.

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10.2.  Informative References

   [CMC-TRANSv1]
              Mandel, J. and S. Turner, "Certificate Management over CMS
              (CMC): Transport Protocols", Work in Progress, Internet-
              Draft, draft-ietf-lamps-rfc5273bis-00, 12 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
              rfc5273bis-00>.

   [CMC-Updates]
              Schaad, J., "Certificate Management over CMS (CMC)
              Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
              <https://www.rfc-editor.org/rfc/rfc6402>.

   [TLS]      Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/rfc/rfc5246>.

Acknowledgements

   Obviously, the authors of this version of the document would like to
   thank Jim Schaad and Michael Myers for their work on the previous
   version of this document.

   The acknowledgment from the previous version of this document
   follows:

   The authors and the PKIX Working Group are grateful for the
   participation of Xiaoyi Liu 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.

Contributors

   Jim Schaad
   August Cellars

   Michael Myers
   TraceRoute Security, Inc.

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Authors' Addresses

   Joseph Mandel
   AKAYLA, Inc.
   Email: joe@akayla.com

   Sean Turner (editor)
   sn3rd
   Email: sean@sn3rd.com

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