LAMPS WG R. Mahy Internet-Draft Rohan Mahy Consulting Services Intended status: Standards Track 9 December 2024 Expires: 12 June 2025 X.509 Certificate Extended Key Usage (EKU) for Instant Messaging URIs draft-ietf-lamps-im-keyusage-latest Abstract RFC 5280 specifies several extended key purpose identifiers (KeyPurposeIds) for X.509 certificates. This document defines Instant Messaging (IM) identity KeyPurposeId for inclusion in the Extended Key Usage (EKU) extension of X.509 v3 public key certificates About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://rohanmahy.github.io/mahy-lamps-im-keyusage/draft-ietf-lamps- im-keyusage.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-lamps-im-keyusage/. Discussion of this document takes place on the LAMPS WG Working Group mailing list (mailto:lamps@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/lamps/. Subscribe at https://www.ietf.org/mailman/listinfo/lamps/. Source for this draft and an issue tracker can be found at https://github.com/rohanmahy/mahy-lamps-im-keyusage. 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 12 June 2025. Copyright Notice 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 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. Conventions and Definitions 3. The IM URI Extended Key Usage 4. Security Considerations 5. IANA Considerations 6. References 6.1. Normative References 6.2. Informative References Appendix A. ASN.1 Module Appendix B. Change log Acknowledgments Author's Address 1. Introduction Instant Messaging (IM) systems using the Messaging Layer Security (MLS) [RFC9420] protocol can incorporate per-client identity certificate credentials. A subjectAltName in these certificates can be an IM URI [RFC3860] or XMPP URI [RFC6121], for example. Organizations may be unwilling to issue certificates for Instant Message client using a general KeyPurposeId such as id-kp-serverAuth or id-kp-clientAuth, because of the risk that such certificates could be abused in a cross-protocol attack. An explanation of MLS credentials as they apply to Instant Messaging is described in [I-D.barnes-mimi-identity-arch]. These credentials are expected to be heavily used in the More Instant Messaging Interoperability (MIMI) Working Group. 2. Conventions and Definitions 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. The IM URI Extended Key Usage This specification defines the KeyPurposeId id-kp-imUri, which may be included in certificates used to prove the identity of an Instant Messaging client. This EKU extension MAY, at the option of the certificate issuer, be either critical or non-critical. id-kp OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) kp(3) } id-kp-imUri OBJECT IDENTIFIER ::= { id-kp TBD1 } 4. Security Considerations The Security Considerations of [RFC5280] are applicable to this document. This extended key purpose does not introduce new security risks but instead reduces existing security risks by providing means to identify if the certificate is generated to sign IM identity credentials. Issuers SHOULD NOT set the id-kp-imUri extended key purpose and an id-kp-clientAuth or id-kp-serverAuth extended key purpose, as that would defeat the improved specificity offered by having an id-kp-imUri extended key purpose. 5. IANA Considerations IANA is requested to register the following OIDs in the "SMI Security for PKIX Extended Key Purpose" registry (1.3.6.1.5.5.7.3). These OIDs are defined in Section 4. +=========+=============+============+ | Decimal | Description | References | +=========+=============+============+ | TBD1 | id-kp-imUri | This-RFC | +---------+-------------+------------+ Table 1 IANA is also requested to register the following ASN.1 [ITU.X690.2021] module OID in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). This OID is defined in Appendix A. +=========+===============+============+ | Decimal | Description | References | +=========+===============+============+ | TBD2 | id-mod-im-eku | This-RFC | +---------+---------------+------------+ Table 2 6. References 6.1. Normative References [ITU.X680.2021] International Telecommunications Union, "Information Technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation", ITU-T Recommendation X.680, 2021. [ITU.X690.2021] 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, 2021. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 6.2. Informative References [I-D.barnes-mimi-identity-arch] Barnes, R. and R. Mahy, "Identity for E2E-Secure Communications", Work in Progress, Internet-Draft, draft- barnes-mimi-identity-arch-01, 23 October 2023, . [RFC3860] Peterson, J., "Common Profile for Instant Messaging (CPIM)", RFC 3860, DOI 10.17487/RFC3860, August 2004, . [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence", RFC 6121, DOI 10.17487/RFC6121, March 2011, . [RFC9420] Barnes, R., Beurdouche, B., Robert, R., Millican, J., Omara, E., and K. Cohn-Gordon, "The Messaging Layer Security (MLS) Protocol", RFC 9420, DOI 10.17487/RFC9420, July 2023, . Appendix A. ASN.1 Module The following module adheres to ASN.1 specifications [ITU.X680.2021] and [ITU.X690.2021]. IM-EKU { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-im-eku (TBD2) } DEFINITIONS IMPLICIT TAGS ::= BEGIN -- OID Arc id-kp OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) kp(3) } -- Extended Key Usage Values id-kp-imUri OBJECT IDENTIFIER ::= { id-kp TBD1 } END Appendix B. Change log RFC Editor, please remove this section on publication. * made Proposed Standard * added a MAY statement in Section 3 * corrected typo in registration of the ASN.1 module (Thanks Sean!) * updated author affiliation * added ASN.1 module * specified that eku is optionally critical Acknowledgments Thanks to Sean Turner and Russ Housley for reviews, suggestions, corrections, and encouragement. Author's Address Rohan Mahy Rohan Mahy Consulting Services Email: rohan.ietf@gmail.com