WG Working Group M. Poirier Internet-Draft T. Fossati Intended status: Informational Linaro Expires: 23 November 2025 22 May 2025 An EAT Profile for Device Attestation draft-poirier-rats-eat-da-latest Abstract In confidential computing, device assignment (DA) is the method by which a device (e.g., network adapter, GPU), whether on-chip or behind a PCIe Root Port, is assigned to a Trusted Virtual Machine (TVM). For the TVM to trust the device, the device must provide the TVM with attestation Evidence confirming its identity and the state of its firmware and configuration. This document defines an attestation Evidence format for DA as an EAT (Entity Attestation Token) profile. 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://example.com/LATEST. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-poirier-rats-eat- da/. Discussion of this document takes place on the WG Working Group mailing list (mailto:WG@example.com), which is archived at https://example.com/WG. Source for this draft and an issue tracker can be found at https://github.com/USER/REPO. 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 23 November 2025. Copyright Notice Copyright (c) 2025 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. Table of Contents 1. Introduction 2. Conventions and Definitions 3. Device Attestation Claims 3.1. SPDM Claims 3.1.1. Measurement Claims 3.1.2. Certificate Claims 4. Collated CDDL 5. Security Considerations 6. IANA Considerations 6.1. New CWT Claims Registrations 6.2. New CBOR Tags Registrations 7. Normative References Appendix A. Examples Acknowledgments Authors' Addresses 1. Introduction In confidential computing, device assignment (DA) is the method by which a device (e.g., network adapter, GPU), whether on-chip or behind a PCIe Root Port, is assigned to a Trusted Virtual Machine (TVM). Most confidential computing platforms (e.g., Arm CCA, AMD SEV-SNP, Intel TDX) provide DA capabilities. Such capabilities prevent agents which are untrusted by the TVM (including other TVMs and the host hypervisor) from accessing or controlling a device that has been assigned to the TVM. This includes, for example, protection of device MMIO interfaces and device caches. From a trust perspective, DA allows a device to be included in the TVM's Trusted Computing Base (TCB). For the TVM to trust the device, the device must provide the TVM with attestation Evidence confirming its identity and the state of its firmware and configuration. This document defines an attestation Evidence format for DA as an EAT [RFC9711] profile. 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. Device Attestation Claims da-token = { &(eat_profile: 265) => "tag:linaro.org,2025:device#1.0.0" &(eat_nonce: 10) => bytes .size 64 ; same as realm nonce &(eat_submods: 266) => { + device-name => $device-claims } } device-name = text .regexp "dev-[A-Za-z0-9]+" $device-claims /= #6.1000000(spdm-claims) $device-claims /= #6.1000001(cxl-claims) $device-claims /= #6.1000002(chi-claims) 3.1. SPDM Claims spdm-claims = { &(measurements: 1) => { + block-id => spdm-measurement ? "signature" => spdm-measurement-blocks-signature } &(certificates: 2) => spdm-certificates } block-id = 0..239 3.1.1. Measurement Claims spdm-measurement = { &(component-type: 1) => component-type measurement } measurement //= ( &(digest-measurement: 2) => digest-measurement ) measurement //= ( &(raw-measurement: 3) => raw-measurement ) component-type /= &(immutable-rom: 0) component-type /= &(mutable-firmware: 1) component-type /= &(hardware-config: 2) component-type /= &(firmware-config: 3) component-type /= &(freeform-measurement-manifest: 4) component-type /= &(device-mode: 5) component-type /= &(mutable-firmware-version: 6) component-type /= &(mutable-firmware-svn: 7) component-type /= &(hash-extend-measurement: 8) component-type /= &(informational: 9) component-type /= &(structured-measurement-manifest: 10) raw-measurement = bytes digest-measurement = digest digest = [ alg: uint / text val: bytes ] 3.1.2. Certificate Claims spdm-certificates = { device-cert-slot => cert-chain ? aux-cert-slots => cert-chain } ; ASN.1 DER-encoded certificates concatenated with no intermediate ; padding. cert-chain = bytes device-cert-slot = 0 aux-cert-slots = 1..7 4. Collated CDDL =============== NOTE: '\' line wrapping per RFC 8792 ================ da-token = { &(eat_profile: 265) => "tag:linaro.org,2025:device#1.0.0", &(eat_nonce: 10) => bytes .size 64, &(eat_submods: 266) => {+ device-name => $device-claims}, } device-name = text .regexp "dev-[A-Za-z0-9]+" $device-claims /= #6.1000000(spdm-claims) / #6.1000001(cxl-claims) \ / #6.1000002(chi-claims) spdm-claims = { &(measurements: 1) => { + block-id => spdm-measurement, ? "signature" => spdm-measurement-blocks-signature, }, &(certificates: 2) => spdm-certificates, } block-id = 0 .. 239 spdm-measurement = { &(component-type: 1) => component-type, measurement, } measurement //= (&(digest-measurement: 2) => digest-measurement // &\ (raw-measurement: 3) => raw-measurement) component-type /= &(immutable-rom: 0) / &(mutable-firmware: 1) / &(\ hardware-config: 2) / &(firmware-config: 3) / &(freeform-measurement\ -manifest: 4) / &(device-mode: 5) / &(mutable-firmware-version: 6) \ / &(mutable-firmware-svn: 7) / &(hash-extend-measurement: 8) / &(\ informational: 9) / &(structured-measurement-manifest: 10) raw-measurement = bytes digest-measurement = digest digest = [ alg: uint / text, val: bytes, ] spdm-certificates = { device-cert-slot => cert-chain, ? aux-cert-slots => cert-chain, } cert-chain = bytes device-cert-slot = 0 aux-cert-slots = 1 .. 7 hash-algorithm-type /= &(tpm_alg_sha_256: 0) / &(tpm_alg_sha_384: 2\ ) / &(tpm_alg_sha_512: 4) / &(tpm_alg_sha3_256: 8) / &(\ tpm_alg_sha3_384: 16) / &(tpm_alg_sha3_512: 32) / &(tpm_alg_sm3_256\ : 64) spdm-measurement-blocks-signature = { &(slot: 1) => 0 .. 7, &(requester-nonce: 2) => bytes .size 32, &(responder-nonce: 3) => bytes .size 32, &(combined-spdm-prefix: 4) => bytes .size 100, &(IL1: 5) => bytes, &(base-hash-algo: 6) => hash-algorithm-type, &(signature: 7) => bytes, } cxl-claims = {} chi-claims = {} 5. Security Considerations TODO Security 6. IANA Considerations 6.1. New CWT Claims Registrations TODO IANA CWT allocations 6.2. New CBOR Tags Registrations TODO IANA CBOR Tag allocations 7. 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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9711] Lundblade, L., Mandyam, G., O'Donoghue, J., and C. Wallace, "The Entity Attestation Token (EAT)", RFC 9711, DOI 10.17487/RFC9711, April 2025, . Appendix A. Examples =============== NOTE: '\' line wrapping per RFC 8792 ================ { / profile / 265: "tag:linaro.org,2025:device#1.0.0", / nonce / 10: h'\ f9efc3341597f75f8d94432ad39566a8c5704b2004ba001c094f475bfc057f9f25d7\ aa40cd86cd30ebaae746fb19f008c1e6a1f23ad6a178e18dceda918f7f6e', / submods / 266: { "dev-a": 1000000({ / measurements / 1: { 1: { / component-type / 1: 2, / hardware config / / raw-measurement / 3: h'4f6d616861' } }, / certificates / 2: { / device certs / 0: h'\ 676f616e6e61747261646974696f6e6d6f6e676572' / no aux certs / } }), "dev-b": 1000000({ / measurements / 1: { 0: { / component-type / 1: 1, / mutable firmware / / digest-measurement / 2: [ / alg / 1, / val / h'6b656e6e656c6c79' ] }, 6: { / component-type / 1: 2, / hardware config / / digest measurement / 2: [ / alg / 0, / val / h'756e646572637279' ] } }, / certificates / 2: { / device certs / 0: h'61746865697A656178696C6C6172', / aux certs (slot=2) / 2: h'23451576923AE99106783948598A' } }) } } Acknowledgments TODO acknowledge. Authors' Addresses Mathieu Poirier Linaro Email: mathieu.poirier@linaro.org Thomas Fossati Linaro Email: thomas.fossati@linaro.org