SIDROPS J. Snijders Internet-Draft Fastly Updates: 6487 (if approved) B. Maddison Intended status: Standards Track Workonline Expires: 14 March 2025 T. Buehler OpenBSD 10 September 2024 Relying Party Handling of Resource Public Key Infrastructure (RPKI) Certificate Revocation List (CRL) Number Extensions draft-ietf-sidrops-rpki-crl-numbers-00 Abstract This document clarifies how Resource Public Key Infrastructure (RPKI) Relying Parties (RPs) handle Certificate Revocation List (CRL) Number extensions. This document updates RFC 6487. 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 14 March 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Snijders, et al. Expires 14 March 2025 [Page 1] Internet-Draft RPKI CRL Number handling for RPs September 2024 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. 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. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Related Work . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Changes from RFC 6487 . . . . . . . . . . . . . . . . . . 3 2. Updates to RFC 6487 . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Normative References . . . . . . . . . . . . . . . . . . 4 4.2. Informative References . . . . . . . . . . . . . . . . . 4 Appendix A. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION . . . . . . . . . . . . . . . . . . . . . . . 5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Section 5.2.3 of [RFC5280] describes the value of the CRL Number extension as a monotonically increasing sequence number, which "allows users to easily determine when a particular CRL supersedes another CRL." In other words, in PKIs in which it is possible for RPs to encounter multiple usable CRLs, the CRL Number extension is a means for the RP to determine which CRL(s) to rely upon. In the RPKI, a well-formed Manifest FileList contains exactly one entry for its associated CRL, together with a collision-resistant message digest of that CRLs contents (see Section 2.2 of [RFC6481] and Section 2 of [RFC9286]). Additionally, the target of the CRL Distribution Points extension in an RPKI Resource Certificate is the same CRL object listed on the issuing CAs current manifest (see Section 4.8.6 of [RFC6487]). Together, these properties guarantee that RPKI RPs will always be able to unambiguously identify exactly one current CRL for each RPKI CA. Thus, in the RPKI, the ordering functionality provided by CRL Numbers is fully subsumed by monotonically increasing Manifest Numbers (Section 4.2.1 of [RFC9286]), thereby obviating the need for RPKI RPs to process CRL Number extensions at all. Snijders, et al. Expires 14 March 2025 [Page 2] Internet-Draft RPKI CRL Number handling for RPs September 2024 Therefore, although the CRL Number extension is mandatory in RPKI CRLs for compliance with the X.509 v2 CRL Profile (Section 5 of [RFC5280]), any use of this extension by RPKI RPs merely adds complexity and fragility to RPKI Resource Certificate path validation. This document mandates that RPKI RPs MUST ignore the CRL Number extension. This document updates [RFC6487] with clarifications for RP implementers. 1.1. Requirements Language 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. 1.2. Related Work It is assumed that the reader is familiar with the terms and concepts described in "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile" [RFC5280] and "A Profile for Resource Certificate Repository Structure" [RFC6481]. 1.3. Changes from RFC 6487 This section summarizes the significant changes between [RFC6487] this document. * Clarifications for handling of CRL Numbers for RPs. * Incorporated RFC 6487 Errata 3205. 2. Updates to RFC 6487 This section updates [RFC6487]. * In Section 5, this paragraph is removed. REMOVED | Where two or more CRLs are issued by the same CA, the CRL with | the highest value of the "CRL Number" field supersedes all | other CRLs issued by this CA. * In Section 5, this paragraph is changed. Snijders, et al. Expires 14 March 2025 [Page 3] Internet-Draft RPKI CRL Number handling for RPs September 2024 OLD | An RPKI CA MUST include the two extensions, Authority Key | Identifier and CRL Number, in every CRL that it issues. RPs | MUST be prepared to process CRLs with these extensions. No | other CRL extensions are allowed. NEW | An RPKI CA MUST include exactly two extensions in every CRL | that it issues: an Authority Key Identifier (AKI) and a CRL | Number. No other CRL extensions are allowed. RPs MUST process | the AKI extension, and MUST ignore the CRL Number extension. 3. IANA Considerations This document has no IANA actions. 4. References 4.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for Resource Certificate Repository Structure", RFC 6481, DOI 10.17487/RFC6481, February 2012, . [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for X.509 PKIX Resource Certificates", RFC 6487, DOI 10.17487/RFC6487, February 2012, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9286] Austein, R., Huston, G., Kent, S., and M. Lepinski, "Manifests for the Resource Public Key Infrastructure (RPKI)", RFC 9286, DOI 10.17487/RFC9286, June 2022, . 4.2. Informative References Snijders, et al. Expires 14 March 2025 [Page 4] Internet-Draft RPKI CRL Number handling for RPs September 2024 [FORT] Leiva, A., "FORT validator", . [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, . [routinator] NLnetLabs, "Routinator", . [rpki-client] Jeker, C., Snijders, J., Dzonsons, K., and T. Buehler, "rpki-client", June 2024, . Appendix A. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in RFC 7942. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to RFC 7942, "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". The following RP implementations check for the presence of the CRL Number extension and whether it is marked non-critical, and otherwise ignore it. * OpenBSD [rpki-client] * [FORT] Snijders, et al. Expires 14 March 2025 [Page 5] Internet-Draft RPKI CRL Number handling for RPs September 2024 * [routinator] additionally checks that the CRL Number is non- negative and fits into 20 octets. Acknowledgements The authors wish to thank Tom Harrison whose observations prompted this internet-draft proposal. Authors' Addresses Job Snijders Fastly Amsterdam The Netherlands Email: job@fastly.com Ben Maddison Workonline Cape Town South Africa Email: benm@workonline.africa Theo Buehler OpenBSD Switzerland Email: tb@openbsd.org Snijders, et al. Expires 14 March 2025 [Page 6]