Constrained RESTful Environments M. S. Lenders Internet-Draft TU Dresden Intended status: Standards Track C. Amsüss Expires: 23 December 2024 T. C. Schmidt HAW Hamburg M. Wählisch TU Dresden & Barkhausen Institut 21 June 2024 Service Binding and Parameter Specification for CoAP over (D)TLS draft-lenders-core-coap-dtls-svcb-00 Abstract This document specifies the usage of Service Parameters as used in SVCB ("Service Binding") DNS resource records for the discovery of transport-layer-secured CoAP services. 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://anr-bmbf- pivot.github.io/draft-lenders-core-coap-dtls-svcb/draft-lenders-core- coap-dtls-svcb.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-lenders-core-coap- dtls-svcb/. Discussion of this document takes place on the Constrained RESTful Environments Working Group mailing list (mailto:core@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/core/. Subscribe at https://www.ietf.org/mailman/listinfo/core/. Source for this draft and an issue tracker can be found at https://github.com/anr-bmbf-pivot/draft-lenders-core-coap-dtls-svcb. 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/. Lenders, et al. Expires 23 December 2024 [Page 1] Internet-Draft CoRE SVCB June 2024 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 23 December 2024. 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application-Layer Protocol Negotiation (ALPN) IDs . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5.1. TLS ALPN for CoAP . . . . . . . . . . . . . . . . . . . . 3 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informative References . . . . . . . . . . . . . . . . . 4 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 5 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction [RFC9460] specifies the "SVCB" ("Service Binding") DNS resource records for looking up communication endpoints of a service. Service Parameters (SvcParams) are used to carry that information. This document specifies which information from SvcParams can be used with CoAP services that are secured by transport security, namely TLS and DTLS. As an example, this information can be obtained as part of the discovery of DNS over CoAP (DoC) servers (see [I-D.ietf-core-dns-over-coap]) that deploy TLS or DTLS to secure their messages. Lenders, et al. Expires 23 December 2024 [Page 2] Internet-Draft CoRE SVCB June 2024 2. Terminology SvcParams denotes the field in either DNS SVCB/HTTPS records as defined in [RFC9460], or DHCP and RA messages as defined in [RFC9463]. 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. Application-Layer Protocol Negotiation (ALPN) IDs [RFC9460] defines the "alpn" key, which is used to identify the service binding to a protocol suite using its Application-Layer Protocol Negotiation (ALPN) ID [RFC7301]. For CoAP over TLS an ALPN ID was defined in [RFC8323]. As it is not advisable to re-use the same ALPN ID for a different transport layer, an ALPN for CoAP over DTLS is also registered in Section 5. To discover CoAP services that secure their messages with TLS or DTLS, these ALPN IDs can be used in the same manner as for any other service secured with transport layer security, as described in [RFC9460]. Other authentication mechanisms are currently out of scope. 4. Security Considerations Any security considerations on SVCB resource records (see [RFC9460]), also apply to this document. 5. IANA Considerations 5.1. TLS ALPN for CoAP The following entry has been added to the "TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry, which is part of the "Transport Layer Security (TLS) Extensions" group. * Protocol: CoAP (over DTLS) * Identification sequence: 0x63 0x6f ("co") * Reference: [RFC7252] and [this document] Note that [RFC7252] does not define the use of the ALPN TLS extension during connection the DTLS handshake. This document does not change that, and thus does not establish any rules like those in Section 8.2 of [RFC8323]. Lenders, et al. Expires 23 December 2024 [Page 3] Internet-Draft CoRE SVCB June 2024 6. References 6.1. 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, . [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014, . [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, "Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, July 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9460] Schwartz, B., Bishop, M., and E. Nygren, "Service Binding and Parameter Specification via the DNS (SVCB and HTTPS Resource Records)", RFC 9460, DOI 10.17487/RFC9460, November 2023, . [RFC9463] Boucadair, M., Ed., Reddy.K, T., Ed., Wing, D., Cook, N., and T. Jensen, "DHCP and Router Advertisement Options for the Discovery of Network-designated Resolvers (DNR)", RFC 9463, DOI 10.17487/RFC9463, November 2023, . 6.2. Informative References [I-D.ietf-core-dns-over-coap] Lenders, M. S., Amsüss, C., Gündoğan, C., Schmidt, T. C., and M. Wählisch, "DNS over CoAP (DoC)", Work in Progress, Internet-Draft, draft-ietf-core-dns-over-coap-06, 4 March 2024, . [RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets", RFC 8323, DOI 10.17487/RFC8323, February 2018, . Lenders, et al. Expires 23 December 2024 [Page 4] Internet-Draft CoRE SVCB June 2024 Appendix A. Change Log Acknowledgments TODO acknowledge. Authors' Addresses Martine Sophie Lenders TUD Dresden University of Technology Helmholtzstr. 10 D-01069 Dresden Germany Email: martine.lenders@tu-dresden.de Christian Amsüss Email: christian@amsuess.com Thomas C. Schmidt HAW Hamburg Berliner Tor 7 D-20099 Hamburg Germany Email: t.schmidt@haw-hamburg.de Matthias Wählisch TUD Dresden University of Technology & Barkhausen Institut Helmholtzstr. 10 D-01069 Dresden Germany Email: m.waehlisch@tu-dresden.de Lenders, et al. Expires 23 December 2024 [Page 5]