Internet DRAFT - draft-fv-rats-ear
draft-fv-rats-ear
Remote ATtestation ProcedureS T. Fossati
Internet-Draft Linaro
Intended status: Standards Track E. Voit
Expires: 25 April 2024 Cisco
S. Trofimov
Arm Limited
23 October 2023
EAT Attestation Results
draft-fv-rats-ear-02
Abstract
This document defines the EAT Attestation Result (EAR) message
format.
EAR is used by a verifier to encode the result of the appraisal over
an attester's evidence. It embeds an AR4SI's "trustworthiness
vector" to present a normalized view of the evaluation results, thus
easing the task of defining and computing authorization policies by
relying parties. Alongside the trustworthiness vector, EAR provides
contextual information bound to the appraisal process. This allows a
relying party (or an auditor) to reconstruct the frame of reference
in which the trustworthiness vector was originally computed. EAR
supports simple devices with one attester as well as composite
devices that are made of multiple attesters, allowing the state of
each attester to be separately examined. EAR can also accommodate
registered and unregistered extensions. It can be serialized and
protected using either CWT or JWT.
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://thomas-
fossati.github.io/draft-ear/draft-fv-rats-ear.html. Status
information for this document may be found at
https://datatracker.ietf.org/doc/draft-fv-rats-ear/.
Discussion of this document takes place on the Remote ATtestation
ProcedureS Working Group mailing list (mailto:rats@ietf.org), which
is archived at https://mailarchive.ietf.org/arch/browse/rats/.
Subscribe at https://www.ietf.org/mailman/listinfo/rats/.
Source for this draft and an issue tracker can be found at
https://github.com/thomas-fossati/draft-ear.
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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
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This Internet-Draft will expire on 25 April 2024.
Copyright Notice
Copyright (c) 2023 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
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. EAT Attestation Result . . . . . . . . . . . . . . . . . . . 4
3.1. Verifier Software Identification . . . . . . . . . . . . 5
3.2. EAR Appraisal Claims . . . . . . . . . . . . . . . . . . 6
3.2.1. Trustworthiness Vector . . . . . . . . . . . . . . . 7
3.2.2. Trust Tiers . . . . . . . . . . . . . . . . . . . . . 7
3.3. JSON Serialisation . . . . . . . . . . . . . . . . . . . 8
3.3.1. Examples . . . . . . . . . . . . . . . . . . . . . . 9
3.4. CBOR Serialisation . . . . . . . . . . . . . . . . . . . 11
3.4.1. Examples . . . . . . . . . . . . . . . . . . . . . . 12
4. EAR Extensions . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Unregistered claims . . . . . . . . . . . . . . . . . . . 13
4.2. Registered claims . . . . . . . . . . . . . . . . . . . . 13
4.3. Choosing between registered and unregistered claims . . . 13
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4.4. TEEP Extension . . . . . . . . . . . . . . . . . . . . . 14
4.4.1. JSON Serialization . . . . . . . . . . . . . . . . . 14
4.4.2. CBOR Serialization . . . . . . . . . . . . . . . . . 16
4.5. Project Veraison Extensions . . . . . . . . . . . . . . . 18
4.5.1. JSON Serialization . . . . . . . . . . . . . . . . . 19
4.5.2. CBOR Serialization . . . . . . . . . . . . . . . . . 21
5. Media Types . . . . . . . . . . . . . . . . . . . . . . . . . 23
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 23
6.1. Project Veraison . . . . . . . . . . . . . . . . . . . . 23
6.1.1. github.com/veraison/ear . . . . . . . . . . . . . . . 24
6.1.2. github.com/veraison/c-ear . . . . . . . . . . . . . . 24
6.1.3. github.com/veraison/rust-ear . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9.1. New EAT Claims . . . . . . . . . . . . . . . . . . . . . 25
9.1.1. EAR Status . . . . . . . . . . . . . . . . . . . . . 25
9.1.2. EAR Trustworthiness Vector . . . . . . . . . . . . . 25
9.1.3. EAR Raw Evidence . . . . . . . . . . . . . . . . . . 26
9.1.4. EAR Appraisal Policy Identifier . . . . . . . . . . . 26
9.1.5. EAR Verifier Software Identifier . . . . . . . . . . 26
9.1.6. EAR TEEP Claims . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.1. Normative References . . . . . . . . . . . . . . . . . . 27
10.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Common CDDL Types . . . . . . . . . . . . . . . . . 29
Appendix B. Open Policy Agent Example . . . . . . . . . . . . . 29
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . 31
Appendix D. Document History . . . . . . . . . . . . . . . . . . 31
D.1. draft-fv-rats-ear-00 . . . . . . . . . . . . . . . . . . 31
D.2. draft-fv-rats-ear-01 . . . . . . . . . . . . . . . . . . 32
D.3. draft-fv-rats-ear-02 . . . . . . . . . . . . . . . . . . 32
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
This document defines the EAT [I-D.ietf-rats-eat] Attestation Result
(EAR) message format.
EAR is used by a verifier to encode the result of the appraisal over
an attester's evidence. It embeds an AR4SI's "trustworthiness
vector" [I-D.ietf-rats-ar4si] to present a normalized view of the
evaluation results, thus easing the task of defining and computing
authorization policies by relying parties. Alongside the
trustworthiness vector, EAR provides contextual information bound to
the appraisal process. This allows a relying party (or an auditor)
to reconstruct the frame of reference in which the trustworthiness
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vector was originally computed. EAR supports simple devices with one
attester as well as composite devices that are made of multiple
attesters (see Section 3.3 of [RFC9334]) allowing the state of each
attester to be separately examined. EAR can also accommodate
registered and unregistered extensions. It can be serialized and
protected using either CWT [RFC8392] or JWT [RFC7519].
2. Conventions and Definitions
This document uses terms and concepts defined by the RATS
architecture. For a complete glossary see Section 4 of [RFC9334].
The terminology from CBOR [STD94], CDDL [RFC8610] and COSE [STD96]
applies; in particular, CBOR diagnostic notation is defined in
Section 8 of [STD94] and Appendix G of [RFC8610].
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. EAT Attestation Result
EAR is an EAT token which can be serialized as JWT [RFC7519] or CWT
[RFC8392].
The EAR claims-set is as follows:
EAR = {
eat.profile => "tag:github.com,2023:veraison/ear"
iat => int
ear.verifier-id => ar4si.verifier-id
? ear.raw-evidence => ear-bytes
eat.submods => { + text => EAR-appraisal }
? eat.nonce => eat.nonce-type
* $$ear-extension
}
Figure 1: EAR (CDDL Definition)
Where:
eat.profile (mandatory) The EAT profile (Section 6 of
[I-D.ietf-rats-eat]) associated with the EAR claims-set and
encodings defined by this document. It MUST be the following tag
URI ([RFC4151]) tag:github.com,2023:veraison/ear.
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iat (mandatory) "Issued At" claim -- the time at which the EAR is
issued. See Section 4.1.6 of [RFC7519] and Section 4.3.1 of
[I-D.ietf-rats-eat] for the EAT-specific encoding restrictions
(i.e., disallowing the floating point representation).
ear.verifier-id (mandatory) Identifying information about the
appraising verifier. See Section 3.1 for further details on its
structure and serialization.
ear.raw-evidence (optional) The unabridged evidence submitted for
appraisal, including any signed container/envelope. This field
may be consumed by other Verifiers in multi-stage verification
scenarios or by auditors. There are privacy considerations
associated with this claim. See Section 8.
eat.submods (mandatory) A submodule map (Section 4.2.18 of
[I-D.ietf-rats-eat]) holding one EAR-appraisal for each separately
appraised attester. The map MUST contain at least one entry. For
each appraised attester the verifier chooses a unique label. For
example, when evidence is in EAT format, the label could be
constructed from the associated EAT profile. A verifier SHOULD
publicly and permanently document its labelling scheme for each
supported evidence type, unless EAR payloads are produced and
consumed entirely within a private deployment. See Section 3.2
for the details about the contents of an EAR-appraisal.
eat.nonce (optional) A user supplied nonce that is echoed by the
verifier to provide freshness. The nonce is a sequence of bytes
between 8 and 64 bytes long. When serialized as JWT, the nonce
MUST be base64 encoded, resulting in a string between 12 and 88
bytes long. See Section 4.1 of [I-D.ietf-rats-eat].
$$ear-extension (optional) Any registered or unregistered extension.
An EAR extension MUST be a map. See Section 4 for further
details.
3.1. Verifier Software Identification
Section 2.2.2 of [I-D.ietf-rats-ar4si] defines an information model
for identifying the software that runs the verifier. The
ar4si.verifier-id claim provides its serialization as follows:
ar4si.verifier-id = {
build => text
developer => text
}
Figure 2: Verifier Software Identification Claim (CDDL Definition)
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Where:
build (mandatory) A text string that uniquely identifies the
software build running the verifier.
developer (mandatory) A text string that uniquely identifies the
organizational unit responsible for this build.
3.2. EAR Appraisal Claims
EAR-appraisal = {
ear.status => $ar4si.trust-tier
? ear.trustworthiness-vector => ar4si.trustworthiness-vector
? ear.appraisal-policy-id => text
* $$ear-appraisal-extension
}
Figure 3: EAR Appraisal Claims (CDDL Definition)
ear.status (mandatory)
The overall appraisal status for this attester represented as one
of the four trustworthiness tiers (Section 3.2.2). The value of
this claim MUST be set to a tier of no higher trust than the tier
corresponding to the worst trustworthiness claim across the entire
trustworthiness vector.
ear.trustworthiness-vector (optional)
The AR4SI trustworthiness vector providing the breakdown of the
appraisal for this attester. See Section 3.2.1 for the details.
This claim MUST be present unless the party requesting Evidence
appraisal explicitly asks for it to be dropped, e.g., via an API
parameter or similar arrangement. Such consumer would therefore
rely entirely on the semantics of the ear.status claim. This
behaviour is NOT RECOMMENDED because of the resulting loss of
quality of the appraisal result.
ear.appraisal-policy-id (optional)
An unique identifier of the appraisal policy used to evaluate the
attestation result.
$$ear-appraisal-extension (optional)
Any registered or unregistered extension. An EAR appraisal
extension MUST be a map. See Section 4 for further details.
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3.2.1. Trustworthiness Vector
The ar4si-trustworthiness-vector claim is an embodiment of the AR4SI
trustworthiness vector (Section 2.3.5 of [I-D.ietf-rats-ar4si]) and
it is defined as follows:
ar4si.trustworthiness-vector = non-empty<{
? instance-identity => $ar4si.trustworthiness-claim
? configuration => $ar4si.trustworthiness-claim
? executables => $ar4si.trustworthiness-claim
? file-system => $ar4si.trustworthiness-claim
? hardware => $ar4si.trustworthiness-claim
? runtime-opaque => $ar4si.trustworthiness-claim
? storage-opaque => $ar4si.trustworthiness-claim
? sourced-data => $ar4si.trustworthiness-claim
}>
$ar4si.trustworthiness-claim = -128..127
Figure 4: Trustworthiness Vector (CDDL Definition)
It contains an entry for each one of the eight AR4SI appraisals that
have been conducted on the submitted evidence (Section 2.3.4 of
[I-D.ietf-rats-ar4si]). The value of each entry is chosen in the
-128..127 range according to the rules described in Sections 2.3.3
and 2.3.4 of [I-D.ietf-rats-ar4si]. All categories are optional. A
missing entry means that the verifier makes no claim about this
specific appraisal facet because the category is not applicable to
the submitted evidence. As required by the non-empty macro, at least
one entry MUST be present in the vector.
3.2.2. Trust Tiers
The trust tier type represents one of the equivalency classes in
which the $ar4si-trustworthiness-claim space is partitioned. See
Section 2.3.2 of [I-D.ietf-rats-ar4si] for the details. The allowed
values for the type are as follows:
$ar4si.trust-tier /= ar4si.trust-tier-none
$ar4si.trust-tier /= ar4si.trust-tier-affirming
$ar4si.trust-tier /= ar4si.trust-tier-warning
$ar4si.trust-tier /= ar4si.trust-tier-contraindicated
Figure 5: Trustworthiness Tiers (CDDL Definition)
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3.3. JSON Serialisation
To serialize the EAR claims-set in JSON format, the following
substitutions are applied to the encoding-agnostic CDDL definitions
in Section 3, Section 3.2.1 and Section 3.2.2:
; $ar4si.trust-tier choice
ar4si.trust-tier-none = "none"
ar4si.trust-tier-affirming = "affirming"
ar4si.trust-tier-warning = "warning"
ar4si.trust-tier-contraindicated = "contraindicated"
; EAR JWT claims
ear.status = "ear.status"
ear.trustworthiness-vector = "ear.trustworthiness-vector"
ear.raw-evidence = "ear.raw-evidence"
ear.appraisal-policy-id = "ear.appraisal-policy-id"
ear.verifier-id = "ear.verifier-id"
; EAT JWT claims
eat.profile = "eat_profile"
eat.nonce = "eat_nonce"
eat.submods = "submods"
; JWT claims
iat = "iat"
; ar4si.trustworthiness-vector
instance-identity = "instance-identity"
configuration = "configuration"
executables = "executables"
file-system = "file-system"
hardware = "hardware"
runtime-opaque = "runtime-opaque"
storage-opaque = "storage-opaque"
sourced-data = "sourced-data"
; JSON types mapping
ear-bytes = text .regexp "[A-Za-z0-9_=-]+"
ear-label = text
; ar4si.verifier-id labels
developer = "developer"
build = "build"
; EAT
eat.nonce-type = base64-url-text .size (12..88)
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3.3.1. Examples
The example in Figure 6 shows an EAR claims-set corresponding to a
"contraindicated" appraisal, meaning the verifier has found some
problems with the attester's state reported in the submitted
evidence. Specifically, the identified issue is related to
unauthorized code or configuration loaded in runtime memory (i.e.,
value 96 in the executables category). The appraisal is for a device
with one attester labelled "PSA". Note that in case there is only
one attester, the labelling can be freely chosen because there is no
ambiguity.
{
"eat_profile": "tag:github.com,2023:veraison/ear",
"iat": 1666529184,
"ear.verifier-id": {
"developer": "https://veraison-project.org",
"build": "vts 0.0.1"
},
"ear.raw-evidence": "NzQ3MjY5NzM2NTYzNzQK",
"submods": {
"PSA": {
"ear.status": "contraindicated",
"ear.trustworthiness-vector": {
"instance-identity": 2,
"executables": 96,
"hardware": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d"
}
}
}
Figure 6: JSON claims-set: contraindicated appraisal
The breakdown of the trustworthiness vector is as follows:
* Instance Identity (affirming): recognized and not compromised
* Configuration (warning): known vulnerabilities
* Executables (contraindicated): contraindicated run-time
* File System (none): no claim being made
* Hardware (affirming): genuine
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* Runtime Opaque (none): no claim being made
* Storage Opaque (none): no claim being made
* Sourced Data (none): no claim being made
The example in Figure 7 contains the appraisal for a composite device
with two attesters named "CCA Platform" and "CCA Realm" respectively.
Both attesters have either "affirming" or (implicit) "none" values in
their associated trustworthiness vectors. Note that the "none"
values can refer to either an AR4SI category that is unapplicable for
the specific attester (ideally, the applicability should be specified
by the evidence format itself), or to the genuine lack of information
at the attester site regarding the specific category. For example,
the reference values for the "CCA Realm" executables (i.e., the
confidential computing workload) may not be known to the CCA platform
verifier. In such cases, it is up to the downstream entity
(typically, the relying party) to complete the partial appraisal.
{
"eat_profile": "tag:github.com,2023:veraison/ear",
"iat": 1666529300,
"ear.verifier-id": {
"developer": "https://veraison-project.org",
"build": "vts 0.0.1"
},
"ear.raw-evidence": "NzQ3MjY5NzM2NTYzNzQKNzQ3MjY5NzM2NTYzNzQK",
"submods": {
"CCA Platform": {
"ear.status": "affirming",
"ear.trustworthiness-vector": {
"instance-identity": 2,
"executables": 2,
"hardware": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d"
},
"CCA Realm": {
"ear.status": "affirming",
"ear.trustworthiness-vector": {
"instance-identity": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d"
}
}
}
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Figure 7: JSON claims-set: simple affirming appraisal
3.4. CBOR Serialisation
; $ar4si.trust-tier code-points
ar4si.trust-tier-none = 0
ar4si.trust-tier-affirming = 2
ar4si.trust-tier-warning = 32
ar4si.trust-tier-contraindicated = 96
; EAR CWT claims
ear.status = 1000
ear.trustworthiness-vector = 1001
ear.raw-evidence = 1002
ear.appraisal-policy-id = 1003
ear.verifier-id = 1004
; EAT CWT claims
eat.profile = 265
eat.nonce = 10
eat.submods= 266
; CWT claims
iat = 6
; ar4si.trustworthiness-vector keys
instance-identity = 0
configuration = 1
executables = 2
file-system = 3
hardware = 4
runtime-opaque = 5
storage-opaque = 6
sourced-data = 7
; CBOR type mappings
ear-bytes = bytes
ear-label = int / text
; ar4si.verifier-id keys
developer = 0
build = 1
; EAT
eat.nonce-type = bytes .size (8..64)
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3.4.1. Examples
The example in Figure 8 is semantically equivalent to that in
Figure 6. It shows the same "contraindicated" appraisal using the
more compact CBOR serialization of the EAR claims-set.
{
265: "tag:github.com,2023:veraison/ear",
6: 1666529184,
1004: {
0: "https://veraison-project.org",
1: "vts 0.0.1"
},
1002: h'6C696665626F61746D616E',
266: {
"PSA": {
1000: 96,
1001: {
0: 2,
2: 96,
4: 2
},
1003: "https://veraison.example/policy/1/60a0068d"
}
}
}
Figure 8: CBOR claims-set: contraindicated appraisal
4. EAR Extensions
EAR provides core semantics for describing the result of appraising
attestation evidence. However, a given application may offer extra
functionality to its relying parties, or tailor the attestation
result to the needs of the application (e.g., TEEP
[I-D.ietf-teep-protocol]). To accommodate such cases, both EAR and
EAR-appraisal claims-sets can be extended by plugging new claims into
the $$ear-extension (or $$ear-appraisal-extension, respectively) CDDL
socket.
The rules that govern extensibility of EAR are those defined in
[RFC8392] and [RFC7519] for CWTs and JWTs respectively.
An extension MUST NOT change the semantics of the EAR and EAR-
appraisal claims-sets.
A receiver MUST ignore any unknown claim.
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4.1. Unregistered claims
An application-specific extension will normally mint its claim from
the "private space" - using integer values less than -65536 for CWT,
and Public or Private Claim Names as defined in Sections 4.2 and 4.3
of [RFC7519] when serializing to JWT.
It is RECOMMENDED that JWT EARs use Collision-Resistant Public Claim
Names (Section 2 of [RFC7519]) rather than Private Claim Names.
4.2. Registered claims
If an extension will be used across multiple applications, or is
intended to be used across multiple environments, the associated
extension claims SHOULD be registered in one, or both, the CWT and
JWT claim registries.
In general, if the registration policy requires an accompanying
specification document (as it is the case for "specification
required" and "standards action"), such document SHOULD explicitly
say that the extension is expected to be used in EAR claims-sets
identified by this profile.
An up-to-date view of the registered claims can be obtained via the
[IANA.cwt] and [IANA.jwt] registries.
4.3. Choosing between registered and unregistered claims
If an extension supports functionality of a specific application
(e.g. Project Veraison Services), its claims MAY be registered.
If an extension supports a protocol that may be applicable across
multiple applications or environments (e.g., TEEP), its claims SHOULD
be registered.
Since, in general, there is no guarantee that an application will be
confined within an environment, it is RECOMMENDED that extension
claims that have meaning outside the application's context are always
registered.
It is also possible that claims that start out as application-
specific acquire a more stable meaning over time. In such cases, it
is RECOMMENDED that new equivalent claims are created in the "public
space" and are registered as described in Section 4.2. The original
"private space" claims SHOULD then be deprecated by the application.
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4.4. TEEP Extension
The TEEP protocol [I-D.ietf-teep-protocol] specifies the required
claims that an attestation result must carry for a TAM (Trusted
Application Manager) to make decisions on how to remediate a TEE
(Trusted Execution Environment) that is out of compliance, or update
a TEE that is requesting an authorized change.
The list is provided in Section 4.3.1 of [I-D.ietf-teep-protocol].
EAR defines a TEEP application extension for the purpose of conveying
such claims.
$$ear-appraisal-extension //= (
ear.teep-claims => ear-teep-claims
)
ear-teep-claims = non-empty<{
? eat.nonce => eat.nonce-type
? eat.ueid => eat.ueid-type
? eat.oemid => eat.oemid-type
? eat.hardware-model => eat.hardware-model-type
? eat.hardware-version => eat.hardware-version-type
? eat.manifests => eat.manifests-type
}>
Figure 9: TEEP Extension (CDDL Definition)
4.4.1. JSON Serialization
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ear.teep-claims = "ear.teep-claims"
eat.ueid = "ueid"
eat.oemid = "oemid"
eat.hardware-model = "hwmodel"
eat.hardware-version = "hwversion"
eat.manifests = "manifests"
; cddl(1)-unsupported: .size (12..44)
eat.ueid-type = base64-url-text
eat.oemid-type = oemid-pen / oemid-ieee / oemid-random
; cddl(1)-unsupported: .size (4..44)
eat.hardware-model-type = base64-url-text
eat.hardware-version-type = [
version: tstr,
? scheme: $version-scheme
]
eat.manifests-type = [ + manifest-format ]
manifest-format = [
content-type: coap-content-format,
content-format: base64-url-text / text
]
coap-content-format = uint .le 65535
oemid-pen = int
; cddl(1)-unsupported: .size 4
oemid-ieee = base64-url-text
; cddl(1)-unsupported: .size 24
oemid-random = base64-url-text
Example:
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{
"eat_profile": "tag:github.com,2023:veraison/ear",
"iat": 1666529184,
"ear.verifier-id": {
"developer": "https://veraison-project.org",
"build": "vts 0.0.1"
},
"ear.raw-evidence": "NzQ3MjY5NzM2NTYzNzQK",
"submods": {
"PSA": {
"ear.status": "contraindicated",
"ear.trustworthiness-vector": {
"instance-identity": 2,
"executables": 96,
"hardware": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d",
"ear.teep-claims": {
"eat_nonce": "80FH7byS7VjfARIq0_KLqu6B9j-F79QtV6p",
"ueid": "AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyAh",
"oemid": "Av8B",
"hwmodel": "fJYq",
"hwversion": ["1.2.5", 16384]
}
}
}
}
4.4.2. CBOR Serialization
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ear.teep-claims = 65000
eat.ueid = 256
eat.oemid = 258
eat.hardware-model = 259
eat.hardware-version = 260
eat.manifests = 273 ; XXX provisional
eat.ueid-type = bytes .size (7..33)
eat.oemid-type = oemid-pen / oemid-ieee / oemid-random
eat.hardware-model-type = bytes .size (1..32)
eat.hardware-version-type = [
version: text
? scheme: $version-scheme
]
eat.manifests-type = [ + manifest-format ]
manifest-format = [
content-type: coap-content-format
content-format: bytes .cbor untagged-coswid
]
coap-content-format = uint .le 65535
untagged-coswid = bytes ; XXX should import coswid
oemid-pen = int
oemid-ieee = bytes .size 3
oemid-random = bytes .size 16
Example:
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{
265: "tag:github.com,2023:veraison/ear",
6: 1666529184,
1004: {
0: "https://veraison-project.org",
1: "vts 0.0.1"
},
1002: h'6C696665626F61746D616E',
266: {
"PSA": {
1000: 0,
1001: {
0: 2,
1: 2,
2: 2,
4: 2
},
1003: "https://veraison.example/policy/1/60a0068d",
65000: {
10: h'948f8860d13a463e',
256: h'0198f50a4ff6c05861c8860d13a638ea',
258: 64242,
259: h'ee80f5a66c1fb9742999a8fdab930893',
260: ["1.2.5", 16384]
}
}
}
}
4.5. Project Veraison Extensions
The Project Veraison verifier defines three private, application-
specific extensions:
ear.veraison.annotated-evidence
JSON representation of the evidence claims-set, including any
annotations provided by the Project Veraison verifier. There are
privacy considerations associated with this claim. See Section 8.
ear.veraison.policy-claims
any extra claims added by the policy engine in the Project
Veraison verifier.
ear.veraison.key-attestation
contains the public key part of a successfully verified attested
key. The key is a DER encoded ASN.1 SubjectPublicKeyInfo
structure (Section 4.1.2.7 of [RFC5280]).
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$$ear-appraisal-extension //= (
ear.veraison.annotated-evidence => ear-veraison-annotated-evidence
)
ear-veraison-annotated-evidence = {
+ ear-label => any
}
$$ear-appraisal-extension //= (
ear.veraison.policy-claims => ear-veraison-policy-claims
)
ear-veraison-policy-claims = {
+ ear-label => any
}
$$ear-appraisal-extension //= (
ear.veraison.key-attestation => ear-veraison-key-attestation
)
ear-veraison-key-attestation = {
ear.veraison.attested-key-public => ear-bytes
}
Figure 10: Project Veraison Extensions (CDDL Definition)
4.5.1. JSON Serialization
ear.veraison.annotated-evidence = "ear.veraison.annotated-evidence"
ear.veraison.policy-claims = "ear.veraison.policy-claims"
ear.veraison.key-attestation = "ear.veraison.key-attestation"
ear.veraison.attested-key-public = "akpub"
Example:
{
"eat_profile": "tag:github.com,2023:veraison/ear",
"iat": 1666529184,
"ear.verifier-id": {
"developer": "https://veraison-project.org",
"build": "vts 0.0.1"
},
"ear.raw-evidence": "NzQ3MjY5NzM2NTYzNzQK",
"submods": {
"PSA_IOT": {
"ear.status": "contraindicated",
"ear.trustworthiness-vector": {
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"instance-identity": 2,
"executables": 96,
"hardware": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d",
"ear.veraison.annotated-evidence": {
"eat-profile": "http://arm.com/psa/2.0.0",
"psa-client-id": 1,
"psa-security-lifecycle": 12288,
"psa-implementation-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"psa-software-components": [
{
"measurement-value":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"signer-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA="
},
{
"measurement-value":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"signer-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA="
}
],
"psa-nonce":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"psa-instance-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyAh",
"psa-certification-reference": "1234567890123-12345"
},
"ear.veraison.policy-claims": {
"psa-certified": {
"certificate-number": "1234567890123-12345",
"date-of-issue": "23/06/2022",
"test-lab": "Riscure",
"certification-holder": "ACME Inc.",
"certified-product": "RoadRunner",
"hardware-version": "Gizmo v1.0.2",
"software-version": "TrustedFirmware-M v1.0.6",
"certification-type": "PSA Certified Level 1 v2.1",
"developer-type": "PSA Certified – Device"
}
}
}
}
}
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Key attestation example:
{
"eat_profile": "tag:github.com,2023:veraison/ear",
"iat": 1666529184,
"ear.verifier-id": {
"developer": "https://veraison-project.org",
"build": "vts 0.0.1"
},
"ear.raw-evidence": "NzQ3MjY5NzM2NTYzNzQK",
"submods": {
"PARSEC_TPM": {
"ear.status": "affirming",
"ear.trustworthiness-vector": {
"instance-identity": 2,
"executables": 2,
"hardware": 2
},
"ear.appraisal-policy-id":
"https://veraison.example/policy/1/60a0068d",
"ear.veraison.key-attestation": {
"akpub":
"MFkwEwYHKoZIzj0CAQYIKoZIz___"
}
}
}
}
4.5.2. CBOR Serialization
ear.veraison.annotated-evidence = -70000
ear.veraison.policy-claims = -70001
ear.veraison.key-attestation = -70002
ear.veraison.attested-key-public = 0
Example:
{
265: "tag:github.com,2023:veraison/ear",
6: 1666529184,
1004: {
0: "https://veraison-project.org",
1: "vts 0.0.1"
},
1002: h'6C696665626F61746D616E',
266: {
"PSA_IOT": {
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1000: 0,
1001: {
0: 2,
1: 2,
2: 2,
4: 2
},
1003: "https://veraison.example/policy/1/60a0068d",
-70000: {
"eat-profile": "http://arm.com/psa/2.0.0",
"psa-client-id": 1,
"psa-security-lifecycle": 12288,
"psa-implementation-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"psa-software-components": [
{
"measurement-value":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"signer-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA="
},
{
"measurement-value":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"signer-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA="
}
],
"psa-nonce":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyA=",
"psa-instance-id":
"AQIDBAUGBwgJCgsMDQ4PEBESExQVFhcYGRobHB0eHyAh",
"psa-certification-reference": "1234567890123-12345"
},
-70001: {
"psa-certified": {
"certificate-number": "1234567890123-12345",
"date-of-issue": "23/06/2022",
"test-lab": "Riscure",
"certification-holder": "ACME Inc.",
"certified-product": "RoadRunner",
"hardware-version": "Gizmo v1.0.2",
"software-version": "TrustedFirmware-M v1.0.6",
"certification-type": "PSA Certified Level 1 v2.1",
"developer-type": "PSA Certified – Device"
}
}
}
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}
}
5. Media Types
Media types for EAR are automatically derived from the base EAT media
type [I-D.ietf-rats-eat-media-type] using the profile string defined
in Section 3.
For example, a JWT serialization would use:
application/eat-jwt; eat_profile="tag:github.com,2023:veraison/ear"
A CWT serialization would instead use:
application/eat-cwt; eat_profile="tag:github.com,2023:veraison/ear"
6. Implementation Status
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
6.1. Project Veraison
The organization responsible for this implementation is Project
Veraison, a Linux Foundation project hosted at the Confidential
Computing Consortium.
The organization currently provides two separate implementations: one
in Golang another in C17.
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The developers can be contacted on the Zulip channel:
https://veraison.zulipchat.com/#narrow/stream/357929-EAR/.
6.1.1. github.com/veraison/ear
The software, hosted at https://github.com/veraison/ear, provides a
Golang package that allows encoding, decoding, signing and
verification of EAR payloads together with a CLI (arc) to create,
verify and visualize EARs on the command line. The maturity level is
currently alpha, and only the JWT serialization is implemented. The
license is Apache 2.0. The package is used by the Project Veraison
verifier to produce attestation results.
6.1.2. github.com/veraison/c-ear
The software, hosted at https://github.com/veraison/c-ear, provides a
C17 library that allows verification and partial decoding of EAR
payloads. The maturity level is currently pre-alpha, and only the
JWT serialization is implemented. The license is Apache 2.0. The
library targets relying party applications that need to verify
attestation results.
6.1.3. github.com/veraison/rust-ear
The software, hosted at https://github.com/veraison/rust-ear,
provides a Rust (2021 edition) library that allows verification and
partial decoding of EAR payloads. The maturity level is currently
pre-alpha, with limitted algorithm support. Both JWT and COSE
serializations are implemented. The license is Apache 2.0. The
library targets verifiers that need to produce attestation results as
well as relying party applications that need to verify and consume
attestation results.
7. Security Considerations
TODO Security
8. Privacy Considerations
EAR is designed to expose as little identifying information as
possible about the attester. However, certain EAR claims have direct
privacy implications. Implementations should therefore allow
applying privacy-preserving techniques to those claims, for example
allowing their redaction, anonymisation or outright removal.
Specifically:
* It SHOULD be possible to disable inclusion of the optional
ear.raw-evidence claim
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* It SHOULD be possible to disable inclusion of the optional
ear.veraison.annotated-evidence claim
* It SHOULD be possible to allow redaction, anonymisation or removal
of specific claims from the ear.veraison.annotated-evidence object
EAR is an EAT, therefore the privacy considerations in Section 8 of
[I-D.ietf-rats-eat] apply.
9. IANA Considerations
9.1. New EAT Claims
This specification adds the following values to the "JSON Web Token
Claims" registry [IANA.jwt] and the "CBOR Web Token Claims" registry
[IANA.cwt].
Each entry below is an addition to both registries.
The "Claim Description", "Change Controller" and "Specification
Documents" are common and equivalent for the JWT and CWT registries.
The "Claim Key" and "Claim Value Types(s)" are for the CWT registry
only. The "Claim Name" is as defined for the CWT registry, not the
JWT registry. The "JWT Claim Name" is equivalent to the "Claim Name"
in the JWT registry.
9.1.1. EAR Status
* Claim Name: ear.status
* Claim Description: EAR Status
* JWT Claim Name: ear.status
* Claim Key: 1000
* Claim Value Type(s): unsigned integer (0, 2, 32, 96)
* Change Controller: IESG
* Specification Document(s): Section 3.2 of RFCthis
9.1.2. EAR Trustworthiness Vector
* Claim Name: ear.trustworthiness-vector
* Claim Description: EAR Trustworthiness Vector
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* JWT Claim Name: ear.trustworthiness-vector
* Claim Key: 1001
* Claim Value Type(s): map
* Change Controller: IESG
* Specification Document(s): Section 3.2.1 of RFCthis
9.1.3. EAR Raw Evidence
* Claim Name: ear.raw-evidence
* Claim Description: EAR Raw Evidence
* JWT Claim Name: ear.raw-evidence
* Claim Key: 1002
* Claim Value Type(s): bytes
* Change Controller: IESG
* Specification Document(s): Section 3 of RFCthis
9.1.4. EAR Appraisal Policy Identifier
* Claim Name: ear.appraisal-policy-id
* Claim Description: EAR Appraisal Policy Identifier
* JWT Claim Name: ear.appraisal-policy-id
* Claim Key: 1003
* Claim Value Type(s): text
* Change Controller: IESG
* Specification Document(s): Section 3.2 of RFCthis
9.1.5. EAR Verifier Software Identifier
* Claim Name: ear.verifier-id
* Claim Description: EAR Verifier Software Identifier
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* JWT Claim Name: ear.verifier-id
* Claim Key: 1004
* Claim Value Type(s): map
* Change Controller: IESG
* Specification Document(s): Section 3.1 of RFCthis
9.1.6. EAR TEEP Claims
TODO
10. References
10.1. Normative References
[I-D.ietf-rats-ar4si]
Voit, E., Birkholz, H., Hardjono, T., Fossati, T., and V.
Scarlata, "Attestation Results for Secure Interactions",
Work in Progress, Internet-Draft, draft-ietf-rats-ar4si-
05, 30 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
ar4si-05>.
[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-22, 14
October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-rats-eat-22>.
[I-D.ietf-rats-eat-media-type]
Lundblade, L., Birkholz, H., and T. Fossati, "EAT Media
Types", Work in Progress, Internet-Draft, draft-ietf-rats-
eat-media-type-04, 23 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
eat-media-type-04>.
[I-D.ietf-teep-protocol]
Tschofenig, H., Pei, M., Wheeler, D. M., Thaler, D., and
A. Tsukamoto, "Trusted Execution Environment Provisioning
(TEEP) Protocol", Work in Progress, Internet-Draft, draft-
ietf-teep-protocol-17, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teep-
protocol-17>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/rfc/rfc4648>.
[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,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/rfc/rfc7519>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
[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, <https://www.rfc-editor.org/rfc/rfc8610>.
[STD94] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[STD96] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
10.2. Informative References
[IANA.cwt] IANA, "CBOR Web Token (CWT) Claims",
<http://www.iana.org/assignments/cwt>.
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[IANA.jwt] IANA, "JSON Web Token (JWT)",
<http://www.iana.org/assignments/jwt>.
[RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme",
RFC 4151, DOI 10.17487/RFC4151, October 2005,
<https://www.rfc-editor.org/rfc/rfc4151>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/rfc/rfc7942>.
[RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote ATtestation procedureS (RATS)
Architecture", RFC 9334, DOI 10.17487/RFC9334, January
2023, <https://www.rfc-editor.org/rfc/rfc9334>.
Appendix A. Common CDDL Types
non-empty
A CDDL generic that can be used to ensure the presence of at least
one item in an object with only optional fields.
non-empty<M> = (M) .within ({ + any => any })
base64-url-text
Base64 encoding using the URL- and filename-safe character set
defined in Section 5 of [RFC4648], with all trailing '='
characters omitted (as permitted by Section 3.2) and without the
inclusion of any line breaks, whitespace, or other additional
characters.
base64-url-text = tstr .regexp "[A-Za-z0-9_-]+"
Appendix B. Open Policy Agent Example
Open Policy Agent OPA (https://www.openpolicyagent.org) is a popular
and flexible policy engine that is used in a variety of contexts,
from cloud to IoT. OPA policies are written using a purpose-built,
declarative programming language called Rego
(https://www.openpolicyagent.org/docs/latest/policy-language/). Rego
has been designed to handle JSON claim-sets and their JWT envelopes
as first class objects, which makes it an excellent fit for dealing
with JWT EARs.
The following example illustrates an OPA policy that a Relying Party
would use to make decisions based on a JWT EAR received from a
trusted verifier.
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package ear
ear_appraisal = {
"verified": signature_verified,
"appraisal-status": status,
"trustworthiness-vector": trust_vector,
} {
# verify EAR signature is correct and from one of the known and
# trusted verifiers
signature_verified := io.jwt.verify_es256(
input.ear_token,
json.marshal(input.trusted_verifiers)
)
# extract the EAR claims-set
[_, payload, _] := io.jwt.decode(input.ear_token)
# access the attester-specific appraisal record
app_rec := payload.submods.PARSEC_TPM
status := app_rec["ear.status"] == "affirming"
# extract the trustworhiness vector for further inspection
trust_vector := app_rec["ear.trustworthiness-vector"]
}
# add further conditions on the trust_vector here
# ...
The result of the policy appraisal is the following JSON object:
{
"ear_appraisal": {
"appraisal-status": true,
"trustworthiness-vector": {
"executables": 2,
"hardware": 2,
"instance-identity": 2
},
"verified": true
}
}
For completeness, the trusted verifier public key and the EAR JWT
used in the example are provided below.
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=============== NOTE: '\' line wrapping per RFC 8792 ================
{
"ear_token": "eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJlYXIucmF3L\
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",
"trusted_verifiers": {
"keys": [
{
"alg": "ES256",
"crv": "P-256",
"kty": "EC",
"x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
"y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4"
}
]
}
}
Appendix C. Open Issues
// Note to RFC Editor: please remove before publication.
The list of currently open issues for this documents can be found at
https://github.com/thomas-fossati/draft-ear/issues.
Appendix D. Document History
// Note to RFC Editor: please remove before publication.
D.1. draft-fv-rats-ear-00
Initial release.
Fossati, et al. Expires 25 April 2024 [Page 31]
Internet-Draft EAR October 2023
D.2. draft-fv-rats-ear-01
* privacy considerations
* OPA policy example
* add rust-ear crate to the implementation status section
D.3. draft-fv-rats-ear-02
* align JWT and CWT representations of eat_nonce
Acknowledgments
Many thanks to Dave Thaler, Greg Kostal, Simon Frost, Yogesh
Deshpande for helpful comments and discussions that have shaped this
document.
Authors' Addresses
Thomas Fossati
Linaro
Email: thomas.fossati@linaro.org
Eric Voit
Cisco
Email: evoit@cisco.com
Sergei Trofimov
Arm Limited
Email: sergei.trofimov@arm.com
Fossati, et al. Expires 25 April 2024 [Page 32]
