Remote ATtestation ProcedureS S. Frost Internet-Draft Arm Intended status: Standards Track T. Fossati Expires: 4 September 2024 Linaro H. Tschofenig Siemens 3 March 2024 EAT Measured Component draft-fft-rats-eat-measured-component-02 Abstract This document defines a "measured components" format that can be used with the EAT Measurements claim. 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 4 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. Frost, et al. Expires 4 September 2024 [Page 1] Internet-Draft EAT Measured Component March 2024 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 3. Information Model . . . . . . . . . . . . . . . . . . . . . . 3 4. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1.1. CWT . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1.2. JWT . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7.1. Media Types Registrations . . . . . . . . . . . . . . . . 8 7.1.1. application/measured-component+cbor . . . . . . . . . 9 7.1.2. application/measured-component+json . . . . . . . . . 9 7.2. Measured Component Content-Format Registrations . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . 12 Appendix A. Collected CDDL . . . . . . . . . . . . . . . . . . . 12 Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . 12 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction Section 4.2.16 of [I-D.ietf-rats-eat] defines a Measurements claim that: "[c]ontains descriptions, lists, evidence or measurements of the software that exists on the entity or any other measurable subsystem of the entity." This claim allows for different measurement formats, each identified by a different CoAP Content-Format (Section 12.3 of [RFC7252]). Initially, the only specified format is CoSWID of type "evidence", as per Section 2.9.4 of [RFC9393]. This document introduces the "measured components" format that can be used with the EAT Measurements claim in addition or as an alternative to CoSWID. Frost, et al. Expires 4 September 2024 [Page 2] Internet-Draft EAT Measured Component March 2024 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. In this document, CDDL [RFC8610] [RFC9165] [I-D.ietf-cbor-cddl-modules] [I-D.ietf-cbor-cddl-more-control] is used to describe the data formats. 3. Information Model A measured component information element includes the computed digest on the software or configuration payload, along with metadata that helps in identifying the measurement and the authorizing entity for component installation. Table 1 describes the information model of a measured component. Frost, et al. Expires 4 September 2024 [Page 3] Internet-Draft EAT Measured Component March 2024 +================+==================================+=============+ | IE | Description | Requirement | | | | Level | +================+==================================+=============+ | Component Name | The name given to a measured | REQUIRED | | | component. It is important that | | | | this name remains consistent | | | | across different releases to | | | | allow for better tracking of the | | | | same measured item across | | | | updates. When combined with a | | | | consistent versioning scheme, it | | | | enables better signaling from | | | | the appraisal procedure to the | | | | relying parties. | | +----------------+----------------------------------+-------------+ | Component | A value representing the | OPTIONAL | | Version | specific release or development | | | | version of the measured | | | | component. Using Semantic | | | | Versioning is RECOMMENDED. | | +----------------+----------------------------------+-------------+ | Digest Value | Hash of the invariant part of | REQUIRED | | | the component that is loaded in | | | | memory at startup time. | | +----------------+----------------------------------+-------------+ | Digest | Hash algorithm used to compute | REQUIRED | | Algorithm | the Digest Value. | | +----------------+----------------------------------+-------------+ | Signer | A unique identifier of the | REQUIRED | | | entity authorizing installation | | | | of the measured component. | | +----------------+----------------------------------+-------------+ | Countersigners | One or more unique identifiers | OPTIONAL | | | of further authorizing entities | | | | for component installation | | +----------------+----------------------------------+-------------+ Table 1: Measured Component Information Elements 4. Data Model The data model is inspired by the "PSA software component" claim (Section 4.4.1 of [I-D.tschofenig-rats-psa-token]), which has been slightly refactored to take into account the recommendations about new EAT claims design in Appendix E of [I-D.ietf-rats-eat]. The following types and semantics have been reused: Frost, et al. Expires 4 September 2024 [Page 4] Internet-Draft EAT Measured Component March 2024 * COSE Key Thumbprint [I-D.ietf-cose-key-thumbprint], for signer and countersigners; * CoSWID software name and version [RFC9393], for component name and version; * CoRIM digest [I-D.ietf-rats-corim], for digest value and algorithm. 4.1. CDDL The measured-component data item: measured-component = [ id: component-id measurement: corim.digest signer: ckt ? countersigners: [ + ckt ] ] ; COSE Key Thumbprint ckt = bytes component-id = [ name: text ? version: version ] ;# import $version-scheme from rfc9393 as coswid version = [ val: text ? scheme: coswid.$version-scheme ] ; eventually: ";#import digest from rfcxxxx as corim" corim.digest = [ alg: (int / text) val: bytes ] The CDDL extending the EAT Measurements format: Frost, et al. Expires 4 September 2024 [Page 5] Internet-Draft EAT Measured Component March 2024 mc-cbor = bstr .cbor measured-component mc-json = tstr .json measured-component ; EAT CBOR (`.feature "cbor"`) $measurements-body-cbor /= mc-cbor ; native $measurements-body-cbor /= tstr .b64u mc-json ; tunnel ; EAT JSON (`.feature "json"`) $measurements-body-json /= mc-json ; native $measurements-body-json /= tstr .b64u mc-cbor ; tunnel 4.1.1. CWT +=====================================+====================+ | content-type (CoAP C-F equivalent) | content-format | +=====================================+====================+ | application/measured-component+cbor | mc-cbor | +-------------------------------------+--------------------+ | application/measured-component+json | tstr .b64u mc-json | +-------------------------------------+--------------------+ Table 2 4.1.2. JWT +=====================================+====================+ | content-type (CoAP C-F equivalent) | content-format | +=====================================+====================+ | application/measured-component+json | mc-json | +-------------------------------------+--------------------+ | application/measured-component+cbor | tstr .b64u mc-cbor | +-------------------------------------+--------------------+ Table 3 5. Examples (The examples are CBOR only. JSON examples will be added in a future version of this document.) The example in Figure 1 is a measured component with all the fields populated. Frost, et al. Expires 4 September 2024 [Page 6] Internet-Draft EAT Measured Component March 2024 [ / id / [ / name / "boot loader X", / version / [ "1.2.3rc2", 16384 / semver / ] ], / measurement / [ / alg / "sha-256", / val / h'3996003d486fb91ffb056f7d03f2b2992b215b31dbe7af4b37 3431fc7d319da3' ], / signer / h'492e9b676c21f6012b1ceeb9032feb4141a880797355f6675 015ec59c51ca1ec', / countersigners / [ h'4277bb97ba7b51577a0d38151d3e08b40bdf946753f5b5bdeb814d6ff5 7a8a5e' ] ] Figure 1: Complete Measured Component The example in Figure 2 is the same measured component as above but used as the format of a measurements claim in a EAT claims-set. Note that the example uses a CoAP Content-Format value from the experimental range (65000), which will change to the value assigned by IANA for the application/measured-component+cbor Content-Format. Note also that the array contains only one measured component, but additional entries could be added if the measured TCB is made of multiple, individually measured components. Frost, et al. Expires 4 September 2024 [Page 7] Internet-Draft EAT Measured Component March 2024 { 273: [ [ 65000, / using a CoAP C-F from the experimental range / << [ / id / [ / name / "boot loader X", / version / [ "1.2.3rc2", 16384 / semver / ] ], / measurement / [ / alg / "sha-256", / val / h'3996003d486fb91ffb056f7d03f2b2992b215b31db e7af4b373431fc7d319da3' ], / signer / h'492e9b676c21f6012b1ceeb9032feb4141a880797 355f6675015ec59c51ca1ec', / countersigners / [ h'4277bb97ba7b51577a0d38151d3e08b40bdf946753f5b5bdeb 814d6ff57a8a5e' ] ] >> ] ] } Figure 2: EAT Measurements Claim using a Measured Component 6. Security Considerations TODO 7. IANA Considerations // RFC Editor: replace "RFCthis" with the RFC number assigned to this document. 7.1. Media Types Registrations IANA is requested to add the following media types to the "Media Types" registry [IANA.media-types]. Frost, et al. Expires 4 September 2024 [Page 8] Internet-Draft EAT Measured Component March 2024 +=========+=====================================+===========+ | Name | Template | Reference | +=========+=====================================+===========+ | mc+cbor | application/measured-component+cbor | RFCthis | +---------+-------------------------------------+-----------+ | mc+json | application/measured-component+json | RFCthis | +---------+-------------------------------------+-----------+ Table 4: Measured Component Media Types 7.1.1. application/measured-component+cbor Type name: application Subtype name: measured-component+cbor Required parameters: n/a Optional parameters: n/a Encoding considerations: binary (CBOR) Security considerations: Section 6 of RFCthis Interoperability considerations: n/a Published specification: RFCthis Applications that use this media type: Attesters, Verifiers and Relying Parties Fragment identifier considerations: The syntax and semantics of fragment identifiers are as specified for "application/cbor". (No fragment identification syntax is currently defined for "application/cbor".) 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 7.1.2. application/measured-component+json Type name: application Subtype name: measured-component+json Required parameters: n/a Optional parameters: n/a Encoding considerations: binary (JSON is UTF-8-encoded text) Security considerations: Section 6 of RFCthis Interoperability considerations: n/a Published specification: RFCthis Applications that use this media type: Attesters, Verifiers and Relying Parties Fragment identifier considerations: The syntax and semantics of Frost, et al. Expires 4 September 2024 [Page 9] Internet-Draft EAT Measured Component March 2024 fragment identifiers are as specified for "application/json". (No fragment identification syntax is currently defined for "application/json".) 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 7.2. Measured Component Content-Format Registrations IANA is requested to register two Content-Format numbers in the "CoAP Content-Formats" sub-registry, within the "Constrained RESTful Environments (CoRE) Parameters" Registry [IANA.core-parameters], as follows: +=========================+================+======+===========+ | Content-Type | Content Coding | ID | Reference | +=========================+================+======+===========+ | application/measured- | - | TBD1 | RFCthis | | component+cbor | | | | +-------------------------+----------------+------+-----------+ | application/measured- | - | TBD2 | RFCthis | | component+json | | | | +-------------------------+----------------+------+-----------+ Table 5 8. References 8.1. Normative References [I-D.ietf-cbor-cddl-modules] Bormann, C., "CDDL Module Structure", Work in Progress, Internet-Draft, draft-ietf-cbor-cddl-modules-01, 18 December 2023, . [I-D.ietf-cbor-cddl-more-control] Bormann, C., "More Control Operators for CDDL", Work in Progress, Internet-Draft, draft-ietf-cbor-cddl-more- control-03, 26 February 2024, . Frost, et al. Expires 4 September 2024 [Page 10] Internet-Draft EAT Measured Component March 2024 [I-D.ietf-cose-key-thumbprint] Isobe, K., Tschofenig, H., and O. Steele, "CBOR Object Signing and Encryption (COSE) Key Thumbprint", Work in Progress, Internet-Draft, draft-ietf-cose-key-thumbprint- 04, 23 October 2023, . [I-D.ietf-rats-corim] Birkholz, H., Fossati, T., Deshpande, Y., Smith, N., and W. Pan, "Concise Reference Integrity Manifest", Work in Progress, Internet-Draft, draft-ietf-rats-corim-03, 23 October 2023, . [I-D.ietf-rats-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-25, 15 January 2024, . [IANA.core-parameters] IANA, "Constrained RESTful Environments (CoRE) Parameters", . [IANA.media-types] IANA, "Media Types", . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Frost, et al. Expires 4 September 2024 [Page 11] Internet-Draft EAT Measured Component March 2024 [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, . [RFC9165] Bormann, C., "Additional Control Operators for the Concise Data Definition Language (CDDL)", RFC 9165, DOI 10.17487/RFC9165, December 2021, . [RFC9393] Birkholz, H., Fitzgerald-McKay, J., Schmidt, C., and D. Waltermire, "Concise Software Identification Tags", RFC 9393, DOI 10.17487/RFC9393, June 2023, . 8.2. Informative References [I-D.tschofenig-rats-psa-token] Tschofenig, H., Frost, S., Brossard, M., Shaw, A. L., and T. Fossati, "Arm's Platform Security Architecture (PSA) Attestation Token", Work in Progress, Internet-Draft, draft-tschofenig-rats-psa-token-22, 21 February 2024, . Appendix A. Collected CDDL TODO Appendix B. Open Issues The list of currently open issues for this documents can be found at https://github.com/thomas-fossati/draft-fft-rats-eat-measured- component/issues. // Note to RFC Editor: please remove before publication. Acknowledgments The authors would like to thank Carsten Bormann for comments, reviews and suggestions. Authors' Addresses Simon Frost Arm Frost, et al. Expires 4 September 2024 [Page 12] Internet-Draft EAT Measured Component March 2024 Email: Simon.Frost@arm.com Thomas Fossati Linaro Email: Thomas.Fossati@linaro.org Hannes Tschofenig Siemens Email: Hannes.Tschofenig@siemens.com Frost, et al. Expires 4 September 2024 [Page 13]