Attestation in OpenID-Connect

2.1. Terminology

This specification uses role names as defined by Remote ATtestation procedureS (RATS), [RFC9334] and OpenID Connect (OIDC), [OCC2014]. If role names conflict, (e.g., Relying Party), then the RATS role is qualified by prepending ‘RATS’ or ‘R’. For example, the RATS Relying Party is disambiguated as ‘RRP’.¶

A summary of roles used in this specification is provided here for convenience.¶

RATS roles are as follows:¶

• Attester (RA) - an endpoint that produces attestation Evidence.¶
• Reference Value Provider (RVP) - an endpoint that produces Reference Values used to appraise Evidence.¶
• Endorser (RE) - an endpoint that produces Endorsements used to assess the trustworthiness of the Attester's attestation capability.¶
• Verifier (RV) - an endpoint that consumes Evidence, Endorsements and Reference Values and produces Attestation Results.¶
• Relying Party (RRP) - an endpoint that consumes Attestation Results and applies them to an application or usage context.¶

OIDC roles are as follows:¶

• OpenID Provider (OP) - an endpoint that authenticates an End User, obtains authorization, and responds with an ID Token and (usually) an Access Token. (a.k.a., an OAuth 2.0 Authorization Server, [RFC6749]).¶
• Relying Party (RP) / Client - an endpoint that sends a request to an OpenID Provider.¶
• UserInfo Endpoint (UE) - an endpoint that receives an Access Token and sends Claims about an End User, also known as the User Agent (UA).¶
• End User (EU) - a human participant.¶

OAuth 2.0 roles are as follows:¶

• Resource Server (RS) - a service that controls a resource.¶

3.1. Protocol Endpoints

The example protocol message exchange involves four main endpoints:¶

1. Device - a RATS Attester that consists of two sub entities:¶

• A UserInfo Endpoint (UE) (e.g., browser) that supplies user information for OIDC authentication, and¶
• A lead Attesting Environment, that collects device attestation Evidence. When using RATS terminology, the device may be referred to as the RATS Attester (RA). The RA is technically an OAuth 2.0 Resource Server (RS) that performs attestation Evidence collection. The Attester device may consist of multiple components that typically include a root of trust, boot code, system software and the browser. The lead Attesting Environment typically seeks to collect Evidence that describes all the components, from the root of trust to the browser, that may influence browser behavior.¶

1. End User (EU/"Alice") - a native application that can engage the human user directly. This document may refer to the End User by name, namely: "Alice".¶
2. Relying Party (RP) - an endpoint that seeks UserInfo used to replay user authentication responses for OIDC exchanges, but also wants Attestation Results that describe the trustworthiness of the UE device. The RP is synonymous with the RATS Relying Party (RRP).¶
3. OpenID Provider (OP) - an Authorization Server (AS) that implements OIDC.¶
4. Verifier (RV) - a RATS attestation Verifier that processes device Evidence. If the Verifier is combined with the OP, the Verifier is synonymous with OP.¶

3.2. Setup Phase

The setup phase creates the various identity (‘id-token’) and access (‘access-token’) credentials that are used during the operational phase to authorize the exchange of the various OIDC protocol messages.¶

3.3. Operational Phase

The operational phase protocol builds on the abstract OIDC protocol in [OCC2014]. The five OIDC steps are described here for convenience and attestation related steps are described as sub-steps.¶

AuthN_Req = {
    "location": https://op.example.com/authn"
    "client_id": "s6BhdRkqt3",
    "scope": "device-attest"
}

AuthN_Rsp = {
    "client_id": "s6BhdRkqt3",
    "scope": "device-attest",
    "resp_type": "code",
    "authn_proof": "<tbd>"
}

access_token = {
    "iss": "https://jwt-op.example.com",
    "sub": "https://jwt-ra.example.com/24400320",
    "aud": "https://jwt-rp.example.com/s6BhdRkqt3",
    "nbf": 1300815780,
    "exp": 1300819380,
    "claims.example.com/attest-api": true
}

id_token = {
    "iss": "https://jwt-op.example.com",
    "sub": "https://jwt-ra.example.com/24400320",
    "aud": "https://jwt-rp.example.com/s6BhdRkqt3",
    "nbf": 1300815780,
    "exp": 1300819380,
    "name": "Alice"
}

evidence_cmw = [
    "application/eat+jwt",
    "<base64-string containing a JWT>"
]

access_token = {
    "iss": "https://jwt-op.example.com",
    "sub": "https://jwt-rv.example.com",
    "aud": "https://jwt-rp.example.com/s6BhdRkqt3",
    "nbf": 1300815780,
    "exp": 1300819380,
    "claims.example.com/appraisal-api": true
}

evidence_cmw = [
    "application/eat+jwt",
    "<base64-string containing a JWT>"
]

attestation_result_cmw = [
    "application/eat+jwt",
    "<base64-string containing a JWT>"
]