<?xml version='1.0' encoding='UTF-8'?><!-- draft submitted in xml v3 --><!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" docName="draft-ietf-sidrops-rpki-crl-numbers-05" number="9829" ipr="trust200902" xml:lang="en" sortRefs="true" submissionType="IETF" consensus="true" updates="6487" obsoletes="" symRefs="true" tocInclude="true" version="3"> <front> <title abbrev="RPKI CRL Numberhandling"> HandlingHandling">Handling of Resource Public Key Infrastructure (RPKI) Certificate Revocation List (CRL) NumberExtensions </title>Extensions</title> <seriesInfo name="RFC" value="9829"/> <author fullname="Job Snijders" initials="J." surname="Snijders"><organization /><address> <postal> <postalLine>Amsterdam</postalLine> <postalLine>The Netherlands</postalLine> </postal> <email>job@sobornost.net</email> </address> </author> <author fullname="Ben Maddison" initials="B." surname="Maddison"> <organization>Workonline</organization> <address> <postal><street/><city>Cape Town</city> <country>South Africa</country> </postal> <email>benm@workonline.africa</email> </address> </author> <author fullname="Theo Buehler" initials="T." surname="Buehler"> <organization>OpenBSD</organization> <address> <postal><country>CH</country><country>Switzerland</country> </postal> <email>tb@openbsd.org</email> </address> </author><date/> <area>Operations and Management Area (OPS)</area> <workgroup>SIDROPS</workgroup><date month="July" year="2025"/> <area>OPS</area> <workgroup>sidrops</workgroup> <keyword>RPKI</keyword> <keyword>Routing Security</keyword> <keyword>BGP</keyword> <keyword>X.509</keyword> <keyword>CRL</keyword> <abstract> <t> This document revises how the Resource Public Key Infrastructure (RPKI) handles Certificate Revocation List (CRL) Number extensions. This document updates RFC 6487. </t> </abstract> </front> <middle> <section anchor="intro"> <name>Introduction</name> <t> <xref target="RFC5280" section="5.2.3" /> describes the value of the Certificate Revocation List (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 Public Key Infrastructures (PKIs) in which it is possible for Relying Parties (RPs) to encounter multiple usable CRLs, the CRL Number extension is a means for an RP to determine which CRLs to rely upon. </t> <t> In the Resource Public Key Infrastructure (RPKI), a well-formed ManifestFileListfileList contains exactly one entry for its associated CRL, together with a collision-resistant message digest of that CRL's contents (see <xref target="RFC6481" section="2.2"/> and <xref target="RFC9286" section="2"/>). Additionally, the target of the CRL Distribution Points extension in an RPKI Resource Certificate is the same CRL object listed on the issuing Certification Authorities (CAs) current manifest (see <xref target="RFC6487" section="4.8.6"/>). 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 (<xref target="RFC9286" section="4.2.1"/>), thereby obviating the need for RPKI RPs to process CRL Number extensions at all. </t> <t> Therefore, although the CRL Number extension is mandatory in RPKI CRLs for compliance with the X.509 v2 CRL Profile (<xref target="RFC5280" section="5"/>), 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 ignore the CRL Number extension. </t> <t> This document updates <xref target="RFC6487"/>. Refer to <xref target="Updates"/> for more details. </t> <section anchor="reqs-lang"> <name>Requirements Language</name> <t> The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> </section> <section anchor="Related"> <name>Related Work</name> <t>It is assumed that theThe reader is assumed to be familiar with the terms and concepts described in"<xref target="RFC5280" format="title"/>""Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile" <xref target="RFC5280"format="default"/>, "<xref target="RFC6481" format="title"/>"/>, "A Profile for Resource Certificate Repository Structure" <xref target="RFC6481" format="default"/>, and"<xref target="RFC9286" format="title"/>""Manifests for the Resource Public Key Infrastructure (RPKI)" <xref target="RFC9286" format="default"/>. </t> </section> <section anchor="Changes"> <name>Changes from RFC 6487</name> <t> This section summarizes the significant changes between <xref target="RFC6487"/> and this document. </t> <!-- [rfced] We have added an informative reference to erratum 3206. Please let us know if you have any concerns. Original: * Integration of RFC 6487 Errata 3205. Current: * Integration of Errata 3205 [Err3205]. --> <ul> <li>Revision of CRL Number handling.</li> <li>Adjustment of step 5 of the Resource Certification Path Validation.</li> <li>Integration ofRFC 6487Errata3205.</li>3205 <xref target="Err3205"/>.</li> </ul> </section> </section> <section> <name>Summary</name> <t> This document clarifies that, in the RPKI, there is exactly one CRL that is appropriate and relevant for determining the revocation status of a given resource certificate. It is the unique CRL object that is simultaneously: </t> <ul> <li>the target of the certificate's CRL Distribution Points extension, and</li><li>listed<!-- [rfced] RFC 9286 defines "fileList" rather than "FileList". We have updated the document accordingly. Please let us know any corrections. Original: In the Resource Public Key Infrastructure (RPKI), a well-formed Manifest FileList contains exactly one entry for its associated CRL, ... Original: * listed in the issuing CA's current Manifest FileList and has matching hash (see Section 4.2.1 of [RFC9286]). Original: By way of the hash in the manifest's FileList this provides a cryptographic guarantee on the Certification Authority's ... In addition, note that the following terminology appears to be used inconsistently throughout the document. Please review these occurrences and let us know if/how they may be made consistent. Manifest FileList vs manifest's FileList (note that we will lowercase FileList as noted above.) Manifest vs manifest (6487 and 9286 seem to use "manifest" except where it's part of a specific name.) --> <li>listed in the issuing CA's current Manifest fileList and has a matching hash (see <xref target="RFC9286" section="4.2.1"/>).</li> </ul> <!-- [rfced] We are not sure what "without recourse" means here. Does it mean "without access to"? Please clarify. Original: In particular, a resource certificate cannot be validated without recourse to the current Manifest of the certificate's issuer. --> <t> In particular, a resource certificate cannot be validated without recourse to the current Manifest of the certificate's issuer. </t> </section> <section anchor="Updates"> <name>Updates to RFC 6487</name> <section> <name>Updates to Section 5</name> <t> This section updates <xref target="RFC6487" section="5"/> as follows: </t> <ul spacing="normal"> <li> <t>First change:</t> <t>OLD</t> <blockquote> <t> 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. </t> </blockquote> <t>NEW</t> <blockquote> <t> Per <xref target="RFC5280" section="5.2.3"/>, CAs issue new CRLs using a monotonically increasing sequence number in the "CRL Number" extension. It isRECOMMENDED<bcp14>RECOMMENDED</bcp14> that the "CRL Number"matchesmatch the "manifestNumber" of the manifest that will include this CRL (see <xref target="RFC9286" section="4.2.1" />). </t> </blockquote> </li> <li> <t>Second change:</t> <t>OLD</t> <blockquote> <t> An RPKI CAMUST<bcp14>MUST</bcp14> include the two extensions, Authority Key Identifier and CRL Number, in every CRL that it issues. RPsMUST<bcp14>MUST</bcp14> be prepared to process CRLs with these extensions. No other CRL extensions are allowed. </t> </blockquote> <t>NEW</t> <blockquote> <t> An RPKI CAMUST<bcp14>MUST</bcp14> 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. </t> <ul> <li>RPsMUST<bcp14>MUST</bcp14> process the AKI extension.</li> <!-- [rfced] We have updated the text to use superscript (see <https://authors.ietf.org/rfcxml-vocabulary#sup> for more information). Please let us know if this is incorrect or not desired. Original: 2^159-1 The HTML and PDF will display 159-1 as an exponent. The text will display as follows: 2^(159-1) --> <li>RPsMUST<bcp14>MUST</bcp14> ignore the CRL Number extension except for checking that it is marked as non-critical and contains a non-negative integer less than or equal to2^159-1.</li>2<sup>159-1</sup>.</li> </ul> </blockquote> </li> </ul> </section> <section> <name>Update to Section 7.2</name> <t> This section updates <xref target="RFC6487" section="7.2"/> as follows: </t> <t>OLD</t> <blockquote> <ol start="5"> <li>The issuer has not revoked the certificate. A revoked certificate is identified by the certificate's serial number being listed on the issuer's current CRL, as identified by the CRLDP of the certificate, the CRL is itself valid, and the public key used to verify the signature on the CRL is the same public key used to verify the certificate itself.</li> </ol> </blockquote> <t>NEW</t> <blockquote> <ol start="5"> <li>The issuer has not revoked the certificate. A revoked certificate is identified by the certificate's serial number being listed on the issuer's current CRL, as identified by the issuer's current Manifest and the CRLDP of the certificate. The CRL is itself valid and the public key used to verify the signature on the CRL is the same public key used to verify the certificate itself.</li> </ol> </blockquote> </section> </section> <section anchor="operational"> <name>Operational Considerations</name> <!-- [rfced] For clarity, may we update the text as follows? Original: This document has no additional operational considerations compared to Section 9 of [RFC6487]. Perhaps: This document has no additional operational considerations beyond those described in Section 9 of [RFC6487]. --> <t> This document has no additional operational considerations compared to <xref target="RFC6487" section="9"/>. </t> </section> <section anchor="security"> <name>Security Considerations</name> <t> The Security Considerations of <xref target="RFC3779"/>, <xref target="RFC5280"/>, and <xref target="RFC6487"/> apply to Resource Certificates and CRLs. </t> <t> This document explicates that, in the RPKI, the CRL listed on the certificate issuer's current Manifest is the one relevant and appropriate for determining the revocation status of a resource certificate. <!-- [rfced] This sentence uses "this" twice in the second sentence and they seemingly refer to different things. What does each instance of "this" refer to? Please review. Note that the first sentence is provided for context. Original: This document explicates that, in the RPKI, the CRL listed on the certificate issuer's current Manifest is the one relevant and appropriate for determining the revocation status of a resource certificate. By way of the hash in the manifest's FileList this provides a cryptographic guarantee on the Certification Authority's intent that this is the most recent CRL and removes possible replay vectors. --> By way of the hash in the manifest's fileList this provides a cryptographic guarantee on the Certification Authority's intent that this is the most recent CRL and removes possible replay vectors. </t> </section> <section anchor="iana"> <name>IANA Considerations</name> <t> This document has no IANA actions. </t> </section> </middle> <back> <references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6481.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6487.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9286.xml"/> </references> <references> <name>Informative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3779.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5280.xml"/> <referenceanchor="rpki-client" target="https://www.rpki-client.org/">anchor="Err3205" target="https://www.rfc-editor.org/errata/eid3205" quoteTitle="false"> <front><title>rpki-client</title><title>RFC Errata, Erratum ID 3205</title> <authorfullname="Claudio Jeker"/> <author fullname="Job Snijders"/> <author fullname="Kristaps Dzonsons"/> <author fullname="Theo Buehler"/> <date month="June" year="2024"initials="" surname="" fullname=""> <organization /> </author> </front></reference> <reference anchor="FORT" target="https://fortproject.net/en/validator"> <front> <title>FORT validator</title> <author fullname="Alberto Leiva"/> <date/> </front> </reference> <reference anchor="routinator" target="https://github.com/NLnetLabs/routinator"> <front> <title>Routinator</title> <author fullname="NLnetLabs"/> <date/> </front><seriesInfo name="RFC" value="6487" /> </reference> </references> </references> <sectiontitle="Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION"> <t> 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. </t> <t> 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". </t> <ul> <li> OpenBSD <xref target="rpki-client"/> </li> <li> <xref target="FORT"/> </li> <li> <xref target="routinator"/> </li> </ul> </section> <sectionanchor="acknowledgements" numbered="false"> <name>Acknowledgements</name> <t> The authors wish to thank <contact fullname="Tom Harrison"/> whose observations prompted this document, <contact fullname="Alberto Leiva"/>, <contact fullname="Tim Bruijnzeels"/>, <contact fullname="Mohamed Boucadair"/>, <contact fullname="Geoff Huston"/>, and the IESG for their valuable comments and feedback. </t> </section> <!-- [rfced] Please review the "Inclusive Language" portion of the online Style Guide <https://www.rfc-editor.org/styleguide/part2/#inclusive_language> and let us know if any changes are needed. Updates of this nature typically result in more precise language, which is helpful for readers. Note that our script did not flag any words in particular, but this should still be reviewed as a best practice. --> </back> </rfc>