Remote ATtestation ProcedureS L. Lundblade Internet-Draft Security Theory LLC Intended status: Standards Track H. Birkholz Expires: 30 March 2025 Fraunhofer SIT T. Fossati Linaro 26 September 2024 EAT Media Types draft-ietf-rats-eat-media-type-10 Abstract Payloads used in Remote Attestation Procedures may require an associated media type for their conveyance, for example when used in RESTful APIs. This memo defines media types to be used for Entity Attestation Tokens (EAT). Discussion Venues This note is to be removed before publishing as an RFC. Discussion of this document takes place on the Remote ATtestation ProcedureS Working Group mailing list (rats@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/rats/. Source for this draft and an issue tracker can be found at https://github.com/thomas-fossati/draft-eat-mt. 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 30 March 2025. Lundblade, et al. Expires 30 March 2025 [Page 1] Internet-Draft EAT Media Types September 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. EAT Types . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. A Media Type Parameter for EAT Profiles . . . . . . . . . . . 5 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6.1. +cwt Structured Syntax Suffix . . . . . . . . . . . . . . 6 6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 7 6.2. Media Types . . . . . . . . . . . . . . . . . . . . . . . 7 6.3. application/eat+cwt Registration . . . . . . . . . . . . 7 6.4. application/eat+jwt Registration . . . . . . . . . . . . 8 6.5. application/eat-bun+cbor Registration . . . . . . . . . . 8 6.6. application/eat-bun+json Registration . . . . . . . . . . 9 6.7. application/eat-ucs+cbor Registration . . . . . . . . . . 9 6.8. application/eat-ucs+json Registration . . . . . . . . . . 10 6.9. CoAP Content-Format Registrations . . . . . . . . . . . . 11 7. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. -04 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.2. -03 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.3. -02 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.4. -01 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . 14 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Lundblade, et al. Expires 30 March 2025 [Page 2] Internet-Draft EAT Media Types September 2024 1. Introduction Payloads used in Remote Attestation Procedures [RATS-Arch] may require an associated media type for their conveyance, for example when used in RESTful APIs (Figure 1). .----. .----------. .----------. | RP | | Attester | | Verifier | '-+--' '----+-----' '-----+----' | | POST /verify | | | EAT(Evidence) | | +--------------------------->| | | 200 OK | | | EAT(Attestation Results) | | |<---------------------------+ | POST /auth | | | EAT(Attestation Results) | | |<---------------------------+ | | 201 Created | | +--------------------------->| | | | | | | | Figure 1: Conveying RATS conceptual messages in REST APIs using EAT This memo defines media types to be used for Entity Attestation Token (EAT) [EAT] payloads independently of the RATS Conceptual Message in which they manifest themselves. The objective is to give protocol, API and application designers a number of readily available and reusable media types for integrating EAT-based messages in their flows, for example when using HTTP [BUILD-W-HTTP] or CoAP [REST-IoT]. 1.1. Requirements Language This document uses the terms and concepts defined in [RATS-Arch]. 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. Lundblade, et al. Expires 30 March 2025 [Page 3] Internet-Draft EAT Media Types September 2024 2. EAT Types Figure 2 illustrates the six EAT wire formats and how they relate to each other. [EAT] defines four of them (CWT, JWT and Detached EAT Bundle in its JSON and CBOR flavours), whilst [UCCS] defines UCCS, and we use the abbreviation "UJCS" to refer to unprotected JWT Claims Sets as defined in Section 2 of [JWT]. .-----. .----+ UJCS |<-------------------------. | '-----' | | | | .-----. | +-----+ UCCS |<-----------------------. | | '-----' | | | | | | .------. | | +-----+ JWT |<------. | | | '------' .--+---. | | | | Crypto |<------. | | | .------. '--+---' | | | +-----+ CWT |<------' | | | | '------' .---+-+-+----. | | Claims-Set +--. | .------. '---+---+----' | +-----+ BUN-J |<------. | ^ | v | '------' .--+---. | | | .------. | | Bundle |<------' | | | Digest | | .------. '--+---' | v '--+---' +-----+ BUN-C |<------' ^ .---+----. | | '------' | | submod |<---' | | '--------' v | ^ .--------------. | | | Nested-Token +-----------------+------------' '--------------' .-------. .---------. .------. Legenda: | Process | | Wire Fmt | | CDDL | '-------' '---------' '------' Figure 2: EAT Types Lundblade, et al. Expires 30 March 2025 [Page 4] Internet-Draft EAT Media Types September 2024 3. A Media Type Parameter for EAT Profiles EAT is an open and flexible format. To improve interoperability, Section 6 of [EAT] defines the concept of EAT profiles. Profiles are used to constrain the parameters that producers and consumers of a specific EAT profile need to understand in order to interoperate. For example: the number and type of claims, which serialisation format, the supported signature schemes, etc. EATs carry an in-band profile identifier using the eat_profile claim (see Section 4.3.2 of [EAT]). The value of the eat_profile claim is either an OID or a URI. The media types defined in this document include an optional eat_profile parameter that can be used to mirror the eat_profile claim of the transported EAT. Exposing the EAT profile at the API layer allows API routers to dispatch payloads directly to the profile-specific processor without having to snoop into the request bodies. This design also provides a finer-grained and scalable type system that matches the inherent extensibility of EAT. The expectation being that a certain EAT profile automatically obtains a media type derived from the base (e.g., application/eat+cwt) by populating the eat_profile parameter with the corresponding OID or URL. When the parameterised version of the EAT media type is used in HTTP (for example, with the "Content-Type" and "Accept" headers), and the value is an absolute URI (Section 4.3 of [URI]), the parameter-value (Appendix A of [HTTP]) MUST use the quoted-string encoding, e.g.: application/eat+jwt; eat_profile="tag:evidence.example,2022" Instead, when the EAT profile is an OID, the token encoding (i.e., without quotes) can be used, e.g.: application/eat+cwt; eat_profile=2.999.1. 4. Examples The example in Figure 3 illustrates the usage of EAT media types for transporting attestation evidence as well as negotiating the acceptable format of the attestation result. Lundblade, et al. Expires 30 March 2025 [Page 5] Internet-Draft EAT Media Types September 2024 # NOTE: '\' line wrapping per RFC 8792 POST /challenge-response/v1/session/1234567890 HTTP/1.1 Host: verifier.example Accept: application/eat+cwt; eat_profile="tag:ar4si.example,2021" Content-Type: application/eat+cwt; \ eat_profile="tag:evidence.example,2022" [ CBOR-encoded EAT w/ eat_profile="tag:evidence.example,2022" ] Figure 3: Example REST Verification API (request) The example in Figure 4 illustrates the usage of EAT media types for transporting attestation results. # NOTE: '\' line wrapping per RFC 8792 HTTP/1.1 200 OK Content-Type: application/eat+cwt; \ eat_profile="tag:ar4si.example,2021" [ CBOR-encoded EAT w/ eat_profile="tag:ar4si.example,2021" ] Figure 4: Example REST Verification API (response) In both cases, a tag URI [TAG] identifying the profile is carried as an explicit parameter. 5. Security Considerations The security consideration of [EAT] and [UCCS] apply in full. 6. IANA Considerations // RFC Editor: please replace RFCthis with this RFC number and remove // this note. 6.1. +cwt Structured Syntax Suffix IANA is requested to register the +cwt structured syntax suffix in the "Structured Syntax Suffixes" registry [IANA.media-type-structured-suffix] in the manner described in [MediaTypes], which can be used to indicate that the media type is encoded as a CWT. Lundblade, et al. Expires 30 March 2025 [Page 6] Internet-Draft EAT Media Types September 2024 6.1.1. Registry Contents Name: CBOR Web Token (CWT) +suffix: +cwt References: [CWT] Encoding Considerations: binary Interoperability Considerations: N/A Fragment Identifier Considerations: The syntax and semantics of fragment identifiers specified for +cwt SHOULD be as specified for application/cwt. (At publication of this document, there is no fragment identification syntax defined for application/cwt.) Security Considerations: See Section 8 of [CWT] Contact: RATS WG mailing list (rats@ietf.org), or IETF Security Area (saag@ietf.org) Author/Change Controller: Remote ATtestation ProcedureS (RATS) Working Group. The IETF has change control over this registration. 6.2. Media Types IANA is requested to add the following media types to the "Media Types" registry [IANA.media-types]. +==============+=====================+======================+ | Name | Template | Reference | +==============+=====================+======================+ | EAT CWT | application/eat+cwt | RFCthis, Section 6.3 | +--------------+---------------------+----------------------+ | EAT JWT | application/eat+jwt | RFCthis, Section 6.4 | +--------------+---------------------+----------------------+ | Detached EAT | application/eat- | RFCthis, Section 6.5 | | Bundle CBOR | bun+cbor | | +--------------+---------------------+----------------------+ | Detached EAT | application/eat- | RFCthis, Section 6.6 | | Bundle JSON | bun+json | | +--------------+---------------------+----------------------+ | EAT UCCS | application/eat- | RFCthis, Section 6.7 | | | ucs+cbor | | +--------------+---------------------+----------------------+ | EAT UJCS | application/eat- | RFCthis, Section 6.8 | | | ucs+json | | +--------------+---------------------+----------------------+ Table 1: New Media Types 6.3. application/eat+cwt Registration Type name: application Lundblade, et al. Expires 30 March 2025 [Page 7] Internet-Draft EAT Media Types September 2024 Subtype name: eat+cwt Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: binary Security considerations: Section 9 of [EAT] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type: Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no 6.4. application/eat+jwt Registration Type name: application Subtype name: eat+jwt Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: 8bit Security considerations: Section 9 of [EAT] and [BCP225] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no 6.5. application/eat-bun+cbor Registration Type name: application Lundblade, et al. Expires 30 March 2025 [Page 8] Internet-Draft EAT Media Types September 2024 Subtype name: eat-bun+cbor Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: binary Security considerations: Section 9 of [EAT] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type: Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no 6.6. application/eat-bun+json Registration Type name: application Subtype name: eat-bun+json Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: Same as [RFC7159] Security considerations: Section 9 of [EAT] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no 6.7. application/eat-ucs+cbor Registration Type name: application Lundblade, et al. Expires 30 March 2025 [Page 9] Internet-Draft EAT Media Types September 2024 Subtype name: eat-ucs+cbor Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: binary Security considerations: Section 7 of [UCCS] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type: Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no 6.8. application/eat-ucs+json Registration Type name: application Subtype name: eat-ucs+json Required parameters: n/a Optional parameters: "eat_profile" (EAT profile in string format. OIDs MUST use the dotted-decimal notation. The parameter value is case-insensitive.) Encoding considerations: Same as [RFC7159] Security considerations: Section 7 of [UCCS] Interoperability considerations: n/a Published specification: Section 6.2 of RFCthis Applications that use this media type Attesters, Verifiers, Endorsers and Reference-Value providers, Relying Parties that need to transfer EAT payloads over HTTP(S), CoAP(S), and other transports. Fragment identifier considerations: n/a Person & email address to contact for further information: RATS WG mailing list (rats@ietf.org) Intended usage: COMMON Restrictions on usage: none Author/Change controller: IETF Provisional registration: no Lundblade, et al. Expires 30 March 2025 [Page 10] Internet-Draft EAT Media Types September 2024 6.9. CoAP Content-Format Registrations IANA is requested to register the following Content-Format numbers in the "CoAP Content-Formats" sub-registry, within the "Constrained RESTful Environments (CoRE) Parameters" Registry [IANA.core-parameters]: +==========================+================+======+===========+ | Content-Type | Content Coding | ID | Reference | +==========================+================+======+===========+ | application/eat+cwt | - | TBD1 | RFCthis | +--------------------------+----------------+------+-----------+ | application/eat+jwt | - | TBD2 | RFCthis | +--------------------------+----------------+------+-----------+ | application/eat-bun+cbor | - | TBD3 | RFCthis | +--------------------------+----------------+------+-----------+ | application/eat-bun+json | - | TBD4 | RFCthis | +--------------------------+----------------+------+-----------+ | application/eat-ucs+cbor | - | TBD5 | RFCthis | +--------------------------+----------------+------+-----------+ | application/eat-ucs+json | - | TBD6 | RFCthis | +--------------------------+----------------+------+-----------+ Table 2: New Content-Formats TBD1..6 are to be assigned from the space 256..999. 7. Changelog // RFC editor: please remove this section 7.1. -04 * Early IANA review 7.2. -03 * Update references 7.3. -02 * Update references * Register +cwt SSS (Issue#14 (https://github.com/ietf-rats-wg/ draft-eat-mt/issues/14)) Lundblade, et al. Expires 30 March 2025 [Page 11] Internet-Draft EAT Media Types September 2024 * Move from eat-jwt to eat+jwt (Issue#14 (https://github.com/ietf- rats-wg/draft-eat-mt/issues/14)) * Move from eat-cwt to eat+cwt (Issue#14 (https://github.com/ietf- rats-wg/draft-eat-mt/issues/14)) 7.4. -01 * Rename profile to eat_profile for consistency with EAT (Issue#4 (https://github.com/ietf-rats-wg/draft-eat-mt/issues/4)) * The DEB acronym is gone: shorthand is now "bun" from bundle (Issue#8 (https://github.com/ietf-rats-wg/draft-eat-mt/issues/8)) * Incorporate editorial suggestions from Carl and Dave (Issue#7 (https://github.com/ietf-rats-wg/draft-eat-mt/issues/7), Issue#9 (https://github.com/ietf-rats-wg/draft-eat-mt/issues/9)) 8. References 8.1. Normative References [BCP225] Best Current Practice 225, . At the time of writing, this BCP comprises the following: Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best Current Practices", BCP 225, RFC 8725, DOI 10.17487/RFC8725, February 2020, . [CoAP] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014, . [CWT] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, . [EAT] Lundblade, L., Mandyam, G., O'Donoghue, J., and C. Wallace, "The Entity Attestation Token (EAT)", Work in Progress, Internet-Draft, draft-ietf-rats-eat-31, 6 September 2024, . Lundblade, et al. Expires 30 March 2025 [Page 12] Internet-Draft EAT Media Types September 2024 [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, . [IANA.core-parameters] IANA, "Constrained RESTful Environments (CoRE) Parameters", . [IANA.media-type-structured-suffix] IANA, "Structured Syntax Suffixes", . [IANA.media-types] IANA, "Media Types", . [JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [MediaTypes] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [UCCS] Birkholz, H., O'Donoghue, J., Cam-Winget, N., and C. Bormann, "A CBOR Tag for Unprotected CWT Claims Sets", Work in Progress, Internet-Draft, draft-ietf-rats-uccs-10, 4 July 2024, . Lundblade, et al. Expires 30 March 2025 [Page 13] Internet-Draft EAT Media Types September 2024 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . 8.2. Informative References [BUILD-W-HTTP] Best Current Practice 56, . At the time of writing, this BCP comprises the following: Nottingham, M., "Building Protocols with HTTP", BCP 56, RFC 9205, DOI 10.17487/RFC9205, June 2022, . [RATS-Arch] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, DOI 10.17487/RFC9334, January 2023, . [REST-IoT] Keränen, A., Kovatsch, M., and K. Hartke, "Guidance on RESTful Design for Internet of Things Systems", Work in Progress, Internet-Draft, draft-irtf-t2trg-rest-iot-14, 27 July 2024, . [TAG] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", RFC 4151, DOI 10.17487/RFC4151, October 2005, . Acknowledgments Thank you Carl Wallace, Carsten Bormann, Dave Thaler, Deb Cooley, Kathleen Moriarty, Michael Richardson, and Paul Howard for your comments and suggestions. Authors' Addresses Laurence Lundblade Security Theory LLC Email: lgl@securitytheory.com Lundblade, et al. Expires 30 March 2025 [Page 14] Internet-Draft EAT Media Types September 2024 Henk Birkholz Fraunhofer Institute for Secure Information Technology Rheinstrasse 75 64295 Darmstadt Germany Email: henk.birkholz@sit.fraunhofer.de Thomas Fossati Linaro Email: thomas.fossati@linaro.org Lundblade, et al. Expires 30 March 2025 [Page 15]