LAMPS Working Group                                         H. BrockhausInternet-Draft                                             D. von OheimbObsoletes: 6712 9480 (if approved)                               SiemensIntended status: Standards Track                            M. OunsworthExpires: 13 July 2025                                            J. Gray                                                                 Entrust                                                          9 January 2025   Internet X.509 Public Key Infrastructure -- HTTP Transfer for the                 Certificate Management Protocol (CMP)                     draft-ietf-lamps-rfc6712bis-10Abstract   This document describes how to layer the Certificate Management   Protocol (CMP) over HTTP.   It includes the updates to RFC 6712 specified in RFC 9480 Section 3.   These updates introduce CMP URIs using a Well-known prefix.  It   obsoletes RFC 6712 and together with I-D.ietf-lamps-rfc4210bis and it   also obsoletes RFC 9480.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."   This Internet-Draft will expire on 13 July 2025.Copyright Notice   Copyright (c) 2025 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   Provisions Relating to IETF Documents (https://trustee.ietf.org/   license-info) in effect on the date of publication of this document.Brockhaus, et al.         Expires 13 July 2025                  [Page 1]Internet-Draft            HTTP Transfer for CMP             January 2025   Please review these documents carefully, as they describe your rights   and restrictions with respect to this document.  Code Components   extracted from this document must include Revised BSD License text as   described in Section 4.e of the Trust Legal Provisions and are   provided without warranty as described in the Revised BSD License.Table of Contents   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2     1.1.  Changes Made by RFC 9480  . . . . . . . . . . . . . . . .   4     1.2.  Changes Made by This Document . . . . . . . . . . . . . .   4   2.  Conventions Used in This Document . . . . . . . . . . . . . .   4   3.  HTTP-Based Protocol . . . . . . . . . . . . . . . . . . . . .   4     3.1.  General Form  . . . . . . . . . . . . . . . . . . . . . .   5     3.2.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .   5     3.3.  Communication Workflow  . . . . . . . . . . . . . . . . .   5     3.4.  HTTP Request-URI  . . . . . . . . . . . . . . . . . . . .   6     3.5.  Pushing of Announcements  . . . . . . . . . . . . . . . .   6   4.  Implementation Considerations . . . . . . . . . . . . . . . .   7   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10   Appendix A.  History of Changes . . . . . . . . . . . . . . . . .  11   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  131.  Introduction   [RFC Editor: please delete:   During IESG telechat the CMP Updates document was approved on   condition that LAMPS provides a RFC6712bis document.  Version -00 of   this document shall be identical to RFC 6712 and version -01   incorporates the changes specified in CMP Updates Section 3.   A history of changes is available in Appendix A of this document.   The authors of this document wish to thank Tomi Kause and Martin   Peylo, the original authors of RFC 6712, for their work and invite   them, next to further volunteers, to join the -bis activity as co-   authors.   ]Brockhaus, et al.         Expires 13 July 2025                  [Page 2]Internet-Draft            HTTP Transfer for CMP             January 2025   The Certificate Management Protocol (CMP) [I-D.ietf-lamps-rfc4210bis]   requires a well-defined transfer mechanism to enable End Entities   (EEs), Registration Authorities (RAs), and Certification Authorities   (CAs) to pass PKIMessage structures between them.   The first version of the CMP specification [RFC2510] included a brief   description of a simple transfer protocol layer on top of TCP.  Its   features were simple transfer-level error handling and a mechanism to   poll for outstanding PKI messages.  Additionally, it was mentioned   that PKI messages could also be conveyed using file-, E-mail-, and   HTTP-based transfer, but those were not specified in detail.   Since the second version of the CMP specification [RFC4210]   incorporated its own polling mechanism and thus the need for a   transfer protocol providing this functionality vanished.  The   remaining features CMP requires from its transfer protocols are   connection and error handling.   CMP can benefit from utilizing reliable transport as CMP requires   connection and error handling from the transfer protocol.  All these   features are covered by HTTP.  Additionally, delayed delivery of CMP   response messages may be handled at transfer level, regardless of the   message contents.  Since [RFC9480] extends the polling mechanism   specified in the second version of CMP [RFC4210] to cover all types   of PKI management transactions, delays detected at application level   may also be handled within CMP, using pollReq and pollRep messages.   The usage of HTTP (e.g., HTTP/1.1 as specified in [RFC9110] and   [RFC9112]) for transferring CMP messages exclusively uses the POST   method for requests, effectively tunneling CMP over HTTP.  While this   is generally considered bad practice (see BCP 56 [RFC9205] for best   current practice on building protocols with HTTP) and should not be   emulated, there are good reasons to do so for transferring CMP.  HTTP   is used as it is generally easy-to-implement and it is able to   traverse network borders utilizing ubiquitous proxies.  Most   importantly, HTTP is already commonly used in existing CMP   implementations.  Other HTTP request methods, such as GET, are not   used because PKI management operations can only be triggered using   CMP's PKI messages, which need to be transferred using a POST   request.   With its status codes, HTTP provides needed error reporting   capabilities.  General problems on the server side, as well as those   directly caused by the respective request, can be reported to the   client.Brockhaus, et al.         Expires 13 July 2025                  [Page 3]Internet-Draft            HTTP Transfer for CMP             January 2025   As CMP implements a transaction identification (transactionID),   identifying transactions spanning over more than just a single   request/response pair, the statelessness of HTTP is not blocking its   usage as the transfer protocol for CMP messages.1.1.  Changes Made by RFC 9480   CMP Updates [RFC9480] updated Section 3.6 of [RFC6712], supporting   the PKI management operations specified in the Lightweight CMP   Profile [RFC9483], in the following areas:   *  Introduce the HTTP URI path prefix '/.well-known/cmp'.   *  Add options for extending the URI structure with further segments      and define a new protocol registry group to that aim.1.2.  Changes Made by This Document   This document obsoletes [RFC6712].  It includes the changes specified   in Section 3 of [RFC9480] as described in Section 1.1 of this   document.  Additionally, it adds the following changes:   *  Removed the requirement to support HTTP/1.0 [RFC1945] in      accordance with Section 4.1 of [RFC9205].   *  Implementations MUST forward CMP messages when an HTTP error      status code occurs, see Section 3.1.   *  Removed Section 3.8 of [RFC6712] as it contains information      redundant with current HTTP specification.2.  Conventions Used in This Document   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.  HTTP-Based Protocol   For direct interaction between two entities, where a reliable   transport protocol like TCP [RFC9293] is available, HTTP [RFC9110]   SHOULD be utilized for conveying CMP messages.  This specification   requires using the POST method (Section 3.1) and the "Content-Type"   header field (Section 3.2), which are available since HTTP/1.0   [RFC1945].Brockhaus, et al.         Expires 13 July 2025                  [Page 4]Internet-Draft            HTTP Transfer for CMP             January 2025   Note: In some situations, CMP requires multiple request/response   pairs to perform a PKI management operation.  Their affiliation with   a PKI management operation is indicated by a transaction identifier   in the CMP message header (see transactionID described in   Section 5.1.1 of [I-D.ietf-lamps-rfc4210bis]).  For details on how to   transfer multiple requests see Section 4.11 of [RFC9205].3.1.  General Form   A DER-encoded [ITU.X690.1994] PKIMessage (Section 5.1 of   [I-D.ietf-lamps-rfc4210bis]) MUST be sent as the content of an HTTP   POST request.  If this HTTP request is successful, the server returns   the CMP response in the content of the HTTP response.  The HTTP   response status code in this case MUST be 200 (OK) status code; other   Successful 2xx status codes MUST NOT be used for this purpose.  HTTP   responses to pushed CMP announcement messages described in   Section 3.5 utilize the status codes 201 and 202 to identify whether   the received information was processed.   While Redirection 3xx status codes MAY be supported by   implementations, clients should only be enabled to automatically   follow them after careful consideration of possible security   implications.  As described in Section 5, 301 (Moved Permanently)   status code could be misused for permanent denial of service.   All applicable Client Error 4xx or Server Error 5xx status codes MAY   be used to inform the client about errors.  Whenever a client   receives an HTTP response with a status code in the 2xx, 4xx, or 5xx   ranges, it MUST support handling response message content containing   a CMP response PKIMessage.3.2.  Media Type   The Internet Media Type "application/pkixcmp" MUST be set in the HTTP   "Content-Type" header field when conveying a PKIMessage.3.3.  Communication Workflow   In CMP, most communication is initiated by the EEs where every CMP   request triggers a CMP response message from the CA or RA.   The CMP announcement messages described in Section 3.5 are an   exception.  Their creation may be triggered by certain events or done   on a regular basis by a CA.  The recipient of the announcement only   replies with an HTTP status code acknowledging the receipt or   indicating an error, but not with a CMP response.Brockhaus, et al.         Expires 13 July 2025                  [Page 5]Internet-Draft            HTTP Transfer for CMP             January 2025   If the receipt of an HTTP request is not confirmed by receiving an   HTTP response, it MUST be assumed that the transferred CMP message   was not successfully delivered to its destination.3.4.  HTTP Request-URI   Each CMP server on a PKI management entity supporting HTTP or HTTPS   transfer MUST support the use of the path prefix '/.well-known/' as   defined in [RFC8615] and the registered name 'cmp' to ease   interworking in a multi-vendor environment.   CMP clients have to be configured with sufficient information to form   the CMP server URI.  This is at least the authority portion of the   URI, e.g., 'www.example.com:80', or the full operation path segment   of the PKI management entity.  Additionally, path segments MAY be   added after the registered application name as part of the full   operation path to provide further distinction.  The path segment 'p'   followed by an arbitraryLabel <name> could, for example, support the   differentiation of specific CAs or certificate profiles.  Further   path segments, e.g., as specified in the Lightweight CMP Profile   [RFC9483], could indicate PKI management operations using an   operationLabel <operation>.  The following list examples of valid   full CMP URIs:      http://www.example.com/.well-known/cmp      http://www.example.com/.well-known/cmp/<operation>      http://www.example.com/.well-known/cmp/p/<name>      http://www.example.com/.well-known/cmp/p/<name>/<operation>   Note that https can also be used instead of http, see item 5 in the   Security Considerations (Section 5).3.5.  Pushing of Announcements   A CMP server may create event-triggered announcements or generate   them on a regular basis.  It MAY utilize HTTP transfer to convey them   to a suitable recipient.  In this use case, the CMP server acts as an   HTTP client, and the recipient needs to utilize an HTTP server.  As   no request messages are specified for those announcements, they can   only be pushed to the recipient.   If an EE wants to poll for a potential CA Key Update Announcement or   the current CRL, a PKI Information Request using a General Message as   described in Appendix D.5 of [I-D.ietf-lamps-rfc4210bis] can be used.Brockhaus, et al.         Expires 13 July 2025                  [Page 6]Internet-Draft            HTTP Transfer for CMP             January 2025   When pushing announcement messages, PKIMessage structures MUST be   sent as the content of an HTTP POST request.   Suitable recipients for CMP announcements might, for example, be   repositories storing the announced information, such as directory   services.  Those services listen for incoming messages, utilizing the   same HTTP Request-URI scheme as defined in Section 3.4.   The following types of PKIMessage are announcements that may be   pushed by a CA.  The prefixed numbers reflect ASN.1 tags of the   PKIBody structure (Section 5.1.2 of [I-D.ietf-lamps-rfc4210bis]).      [15] CA Key Update Announcement      [16] Certificate Announcement      [17] Revocation Announcement      [18] CRL Announcement   CMP announcement messages do not require any CMP response.  However,   the recipient MUST acknowledge receipt with an HTTP response having   an appropriate status code and an empty content.  When not receiving   such a response, it MUST be assumed that the delivery was not   successful.  If applicable, the sending side MAY try sending the   announcement again after waiting for an appropriate time span.   If the announced issue was successfully stored in a database or was   already present, the answer MUST be an HTTP response with a 201   (Created) status code and an empty content.   In case the announced information was only accepted for further   processing, the status code of the returned HTTP response MAY also be   202 (Accepted).  After an appropriate delay, the sender may then try   to send the announcement again and may repeat this until it receives   a confirmation that it has been successfully processed.  The   appropriate duration of the delay and the option to increase it   between consecutive attempts should be carefully considered.   A receiver MUST answer with a suitable 4xx or 5xx error code when a   problem occurs.4.  Implementation Considerations   Implementers should be aware that other implementations might exist   that use a different approach for transferring CMP over HTTP.   Further, implementations based on earlier I-Ds that led to [RFC6712]   might use an unregistered "application/pkixcmp-poll" Media Type.   Conforming implementations MAY handle this type like "application/   pkixcmp".Brockhaus, et al.         Expires 13 July 2025                  [Page 7]Internet-Draft            HTTP Transfer for CMP             January 20255.  Security Considerations   All security considerations in HTTP [RFC9110] apply.  The following   items need to be considered by implementers and users:   1.  There is the risk for denial-of-service attacks through resource       consumption by opening many connections to an HTTP server.       Therefore, idle connections should be terminated after an       appropriate timeout; this may also depend on the available free       resources.   2.  Without being encapsulated in effective security protocols, such       as Transport Layer Security (TLS) [RFC5246] or [RFC8446], or       without using HTTP digest [RFC9530] there is no integrity       protection at the HTTP level.  Therefore, information from the       HTTP should not be used to change state of the transaction,       regardless of whether any mechanism was used to ensure the       authenticity or integrity of HTTP messages (e.g., TLS or HTTP       digests).   3.  Client users should be aware that storing the target location of       an HTTP response with the 301 (Moved Permanently) status code       could be exploited by a meddler-in-the-middle attacker trying to       block them permanently from contacting the correct server.   4.  If no measures to authenticate and protect the HTTP responses to       pushed announcement messages are in place, their information       regarding the announcement's processing state may not be trusted.       In that case, the overall design of the PKI system must not       depend on the announcements being reliably received and processed       by their destination.   5.  CMP provides inbuilt integrity protection and authentication.       The information communicated unencrypted in CMP messages does not       contain sensitive information endangering the security of the PKI       when intercepted.  However, it might be possible for an       eavesdropper to utilize the available information to gather       confidential personal, technical, or business critical       information.  The protection of the confidentiality of CMP       messages together with an initial authentication of the RA/CA       before the first CMP message is transmitted ensures the privacy       of the EE requesting certificates.  Therefore, users of the HTTP       transfer for CMP messages should consider using HTTP over TLS       according to [RFC9110] or using virtual private networks created,       for example, by utilizing Internet Protocol Security according to       [RFC7296].Brockhaus, et al.         Expires 13 July 2025                  [Page 8]Internet-Draft            HTTP Transfer for CMP             January 20256.  IANA Considerations   The reference to [RFC2510] at https://www.iana.org/assignments/media-   types/media-types.xhtml should be replaced with a reference to this   document.   The reference to [RFC4210] at https://www.iana.org/assignments/core-   parameters/core-parameters.xhtml should be replaced with a reference   to this document.   The reference to [RFC9480] at https://www.iana.org/assignments/well-   known-uris/well-known-uris.xhtml and   https://www.iana.org/assignments/cmp/cmp.xhtmlshould should be   replaced with a reference to this document.   No further action by the IANA is necessary for this document or any   anticipated updates.7.  Acknowledgments   The authors wish to thank Tomi Kause and Martin Peylo, the original   authors of [RFC6712], for their work.   We also thank all reviewers for their valuable feedback.8.  References8.1.  Normative References   [RFC1945]  Berners-Lee, T., Fielding, R., and H. Frystyk, "Hypertext              Transfer Protocol -- HTTP/1.0", RFC 1945,              DOI 10.17487/RFC1945, May 1996,              <https://www.rfc-editor.org/rfc/rfc1945>.   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,              <https://www.rfc-editor.org/rfc/rfc8615>.   [RFC9110]  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>.   [RFC9112]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,              Ed., "HTTP/1.1", STD 99, RFC 9112, DOI 10.17487/RFC9112,              June 2022, <https://www.rfc-editor.org/rfc/rfc9112>.Brockhaus, et al.         Expires 13 July 2025                  [Page 9]Internet-Draft            HTTP Transfer for CMP             January 2025   [I-D.ietf-lamps-rfc4210bis]              Brockhaus, H., von Oheimb, D., Ounsworth, M., and J. Gray,              "Internet X.509 Public Key Infrastructure -- Certificate              Management Protocol (CMP)", Work in Progress, Internet-              Draft, draft-ietf-lamps-rfc4210bis-15, 18 November 2024,              <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-              rfc4210bis-15>.   [ITU.X690.1994]              International Telecommunications Union, "Information              Technology - ASN.1 encoding rules: Specification of Basic              Encoding Rules (BER), Canonical Encoding Rules (CER) and              Distinguished Encoding Rules (DER)", ITU-T Recommendation              X.690, 1994.   [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>.8.2.  Informative References   [RFC9480]  Brockhaus, H., von Oheimb, D., and J. Gray, "Certificate              Management Protocol (CMP) Updates", RFC 9480,              DOI 10.17487/RFC9480, November 2023,              <https://www.rfc-editor.org/rfc/rfc9480>.   [RFC9483]  Brockhaus, H., von Oheimb, D., and S. Fries, "Lightweight              Certificate Management Protocol (CMP) Profile", RFC 9483,              DOI 10.17487/RFC9483, November 2023,              <https://www.rfc-editor.org/rfc/rfc9483>.   [RFC2510]  Adams, C. and S. Farrell, "Internet X.509 Public Key              Infrastructure Certificate Management Protocols",              RFC 2510, DOI 10.17487/RFC2510, March 1999,              <https://www.rfc-editor.org/rfc/rfc2510>.   [RFC4210]  Adams, C., Farrell, S., Kause, T., and T. Mononen,              "Internet X.509 Public Key Infrastructure Certificate              Management Protocol (CMP)", RFC 4210,              DOI 10.17487/RFC4210, September 2005,              <https://www.rfc-editor.org/rfc/rfc4210>.Brockhaus, et al.         Expires 13 July 2025                 [Page 10]Internet-Draft            HTTP Transfer for CMP             January 2025   [RFC5246]  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>.   [RFC6712]  Kause, T. and M. Peylo, "Internet X.509 Public Key              Infrastructure -- HTTP Transfer for the Certificate              Management Protocol (CMP)", RFC 6712,              DOI 10.17487/RFC6712, September 2012,              <https://www.rfc-editor.org/rfc/rfc6712>.   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.              Kivinen, "Internet Key Exchange Protocol Version 2              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October              2014, <https://www.rfc-editor.org/rfc/rfc7296>.   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,              <https://www.rfc-editor.org/rfc/rfc8446>.   [RFC9530]  Polli, R. and L. Pardue, "Digest Fields", RFC 9530,              DOI 10.17487/RFC9530, February 2024,              <https://www.rfc-editor.org/rfc/rfc9530>.   [RFC9205]  Nottingham, M., "Building Protocols with HTTP", BCP 56,              RFC 9205, DOI 10.17487/RFC9205, June 2022,              <https://www.rfc-editor.org/rfc/rfc9205>.   [RFC9293]  Eddy, W., Ed., "Transmission Control Protocol (TCP)",              STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,              <https://www.rfc-editor.org/rfc/rfc9293>.Appendix A.  History of Changes   Note: This appendix will be deleted in the final version of the   document.   From version 09 -> 10:   *  Addressed IESG review comments from Mahesh Jethanandani and      responded to comments from Orie Steele and Zaheduzzaman Sarker via      email   From version 08 -> 09:   *  Incorporated relevant text from former Sections 3.1 and 3.2 in the      introduction of Section 3 as proposed by HTTPDIR reviewBrockhaus, et al.         Expires 13 July 2025                 [Page 11]Internet-Draft            HTTP Transfer for CMP             January 2025   *  Added reference to HTTP Security Considerations to Section 5 and      updated the first item as proposed by HTTPDIR review   From version 07 -> 08:   *  Addressed HTTPDIR, SECDIR, OPSDIR and ARTART review comments   *  Aligned the terminology with https://httpwg.org/admin/editors/      style-guide   *  Implemented editorial changes proposed by OPSDIR reviewer   *  Removed requirement to support HTTP/1.0   *  Added normative language in Sections 3.3 and 3.7 for clarity   *  Added the requirement to provide any HTTP response message content      to the application   *  Removed the paragraph on the "Content-Length" header field and      Section 3.8 to reduce redundancy with current versions HTTP/1.1   From version 06 -> 07:   *  Updated the the page header to 'HTTP Transfer for CMP'   *  Removed one instruction to RFC Editors   *  Deprecated PKIMessages as plural of PKIMessage to prevent      confusion with ASN.1 type PKIMessages   *  Fixed some nits in Section 1   *  Aligned Section 3.6 and Section 5 with RFC 9483 and draft-ietf-      anima-brski-ae   From version 05 -> 06:   *  Updates IANA considerations addressing IANA early review (see      thread "[IANA #1368693] Early review: draft-ietf-lamps-      rfc4210bis-12 (IETF 120)").   From version 04 -> 05:   *  Added IANA considerations addressing IANA early review.   From version 03 -> 04:Brockhaus, et al.         Expires 13 July 2025                 [Page 12]Internet-Draft            HTTP Transfer for CMP             January 2025   *  Aligned with released RFC 9480 - RFC 9483.   From version 02 -> 03:   *  Fixing one formatting nit.   From version 01 -> 02:   *  Updated Section 3.4 including the requirement to add the content-      length filed into the HTTP header.   *  Added a reference to TLS 1.3.   *  Addressed idnits feedback, specifically changing the following RFC      references: RFC2616 -> RFC9112; RFC2818 -> RFC9110, and RFC5246 ->      RFC8446   From version 00 -> 01:   *  Performed all updates specified in CMP Updates Section 3.   Version 00:   This version consists of the text of RFC6712 with the following   changes:   *  Introduced the authors of this document and thanked the authors of      RFC6712 for their work.   *  Added a paragraph to the introduction explaining the background of      this document.   *  Added the change history to this appendix.Authors' Addresses   Hendrik Brockhaus   Siemens   Werner-von-Siemens-Strasse 1   80333 Munich   Germany   Email: hendrik.brockhaus@siemens.com   URI:   https://www.siemens.comBrockhaus, et al.         Expires 13 July 2025                 [Page 13]Internet-Draft            HTTP Transfer for CMP             January 2025   David von Oheimb   Siemens   Werner-von-Siemens-Strasse 1   80333 Munich   Germany   Email: david.von.oheimb@siemens.com   URI:   https://www.siemens.com   Mike Ounsworth   Entrust   1187 Park Place   Minneapolis, MN 55379   United States of America   Email: mike.ounsworth@entrust.com   URI:   https://www.entrust.com   John Gray   Entrust   1187 Park Place   Minneapolis, MN 55379   United States of America   Email: john.gray@entrust.com   URI:   https://www.entrust.comBrockhaus, et al.         Expires 13 July 2025                 [Page 14]