[Openid-specs-ab] Comments on Aggregated Claims/Credential Provider documents

Wed Feb 3 00:04:41 UTC 2021

The use-cases so far have been aggregation of claims of either of the credential formats and rather than combination of both. JWKs might not, but "Base64 url encoded representation of the thumbprint of the Client’s public key" should work for JSON-LD too?

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差出人: nadalin at prodigy.net <nadalin at prodigy.net>
送信日時: 2021年2月3日 7:25
宛先: 'Artifact Binding/Connect Working Group' <openid-specs-ab at lists.openid.net>
CC: Kristina Yasuda <Kristina.Yasuda at microsoft.com>
件名: RE: [Openid-specs-ab] Comments on Aggregated Claims/Credential Provider documents

So JWKs have a specific schema, its not the same schema ad JSON-LD, a goal of aggregated claims of different schemas may be problematic, so I’m not convinced that is a goal that we should undertake

From: Openid-specs-ab <openid-specs-ab-bounces at lists.openid.net> On Behalf Of Kristina Yasuda via Openid-specs-ab
Sent: Tuesday, February 2, 2021 3:41 AM
To: Artifact Binding/Connect Working Group <openid-specs-ab at lists.openid.net>
Cc: Kristina Yasuda <Kristina.Yasuda at microsoft.com>
Subject: [Openid-specs-ab] Comments on Aggregated Claims/Credential Provider documents

Hi,

Below are comments/questions after reading Aggregated Claims<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbitbucket.org%2Fopenid%2Fconnect%2Fsrc%2F00140ab1e32c7160ed2635ce871c555ce7c32b75%2Fopenid-connect-claims-aggregation%2Fopenid-connect-claims-aggregation-1_0.md&data=04%7C01%7CKristina.Yasuda%40microsoft.com%7C3ec448a58f00494e512508d8c7c969e5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637479015190931547%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=M0zDoGTVSNDnf7MT2l8mGrX7z9vSomBzKPtpOopGqic%3D&reserved=0> and Credential Provider<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmattrglobal.github.io%2Foidc-client-bound-assertions-spec%2F%23name-token-endpoint-response&data=04%7C01%7CKristina.Yasuda%40microsoft.com%7C3ec448a58f00494e512508d8c7c969e5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637479015190941499%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=jXvPgYfFyNUUeZV2YpMzJuTBVNfraFox6udZ4O7ujEs%3D&reserved=0> drafts as requested during today's Connect call:

Regarding core functionality of binding claims to the key material supplied by the Client, Aggregated Claims binds to `uid` - base64 url encoded representation of the thumbprint of the Client’s public key used for signing, while Credential Provider binds to `sub_jwk`- a raw key material that is a JSON object that is a valid JWK.

Usage of `uid` seems to be a simpler approach. What would be an advantage of using `sub_jwk` over encoded thumbprint of a public key? Assuming one of the requirements of Credential Provider is to expand to the usage of additional credential formats, would usage of `uid` be applicable to JSON-LD too or does `sub_jwk` has an advantage?

Credential Provider also defines a new scope `openid_credential`. Indicating in the request that binding is supported can be achieved through `credential_supported` OP metadata and could work without defining a new scope, like in Aggregated Claims document.

In addition to a binding mechanism, Aggregated Claims defines a mechanism to request claims building up on `claims` parameter and Aggregated Claims mechanism of OIDC, and Credential Provider defines support for additional credential and identifier formats (such as JSON-LD, DIDs). These are not mutually exclusive and it should be possible to fulfill requirement of both in one document, while staying true to the scope of defining mechanism for claims/credential binding (and of course semantics would have to align!).

Best Regards,

Kristina

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差出人: Openid-specs-ab <openid-specs-ab-bounces at lists.openid.net<mailto:openid-specs-ab-bounces at lists.openid.net>> が Takahiko Kawasaki via Openid-specs-ab <openid-specs-ab at lists.openid.net<mailto:openid-specs-ab at lists.openid.net>> の代理で送信
送信日時: 2020年11月17日 6:09
宛先: Artifact Binding/Connect Working Group <openid-specs-ab at lists.openid.net<mailto:openid-specs-ab at lists.openid.net>>
CC: Takahiko Kawasaki <taka at authlete.com<mailto:taka at authlete.com>>
件名: [Openid-specs-ab] Feedback to OpenID Connect Claims Aggregation 1.0

Hello,

This is the first feedback from me to "OpenID Connect Claims Aggregation 1.0" as requested in the last AB/Connect WG call on Nov 9.

- - - - - - - - - -

- Section 5.3: I'm not sure RS256 is appropriate as the default value for claims_signed_response_alg. FAPI Part 2 Section 8.6 explicitly prohibits the algorithm for security reasons.

- Section 5.4.2: Without diagrams and examples, it is difficult for me to understand how "uid" and "cp_sub" are used for what reasons.

- Section 5.6.1: Why is it necessary to define "uid" request parameter? It seems that the "uid" request parameter would make it possible to get information about an arbitrary end-user who is different from the legitimate one that is associated with the presented access token.

- Section 5.6.1: Why is it necessary to list "additional" client identifiers in "aud"? It seems that the "aud" request parameter would make it possible to add arbitrary client identifiers in addition to the legitimate one that is associated with the presented access token. It seems the description was added intentionally, but I'm not sure it's safe from a security perspective.

- "uid": In Section 5.4.2, "uid" is the thumbprint of a public key. On the other hand, in Section 5.6.1, "uid" is an end-user's identifier. Using the same parameter name with different meanings is confusing.

- Section 5.6.2: The 6th paragraph ("If the Aggregation Response is signed and/or encrypted...") contradicts with other parts in the specification itself. The specification requires that responses from Claims Endpoint always be signed and optionally encrypted.

Editorial Issues
- "http" is used in some links.
- Link to RFC 7636 is wrong.
- Links to JW* specifications are old. They should point to IETF RFCs.
- Link to MTLS is old. It should point to the IETF RFC 8705.
- Referenced OpenID.IDA specification is not the latest one. The published latest version is ID2.
- The list in Section 1 is not properly formatted in HTML.
- Parameter names should be monospace instead of italic.
- Section 5.4: s/Code Authorization Flow/Authorization Code Flow/
- Section 5.6.1: JSON object given to "aud" in the Aggregation Request is wrong.
- Section 5.6.2: s/MAY elect to/MAY select to/
- More diagrams and examples are needed for readers.

To be honest, I couldn't understand the specification well due to its complexity and lack of diagrams and examples. What is the essential difference between UserInfo Endpoint and Claims Endpoint?

Best Regards,
Takahiko Kawasaki
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