Summary: Has a DISCUSS. Needs 4 more YES or NO OBJECTION positions to pass.
Thank you for the updates in the -08; they address the bulk of the substantive issues! I have a few points remaining on the -08 text but I think there are more localized issues to resolve. [media-type expert review is only suggested, not mandatory, for IETF-stream standards actions] It looks like we need to register 'active' as a JWT claim? I don't think the new semantics for "jti" in the introspection response are compatible with the RFC 7519 definition. Specifically, we say that "jti" will be tied to the input access token, but 7519 says that "jti" has to change when the contents of the JWT change ("MUST be assigned in a manner that ensures that there is a negligible probability that the same value will be accidentally assigned to a different data object"), and we admit at least the possibility of "active" and "iat" changing. Section 5 says that: If the access token is considered active, it MUST contain the claims "iss" and "aud" in order to prevent misuse of the JWT as an ID or access token (see Section 8.1). But I don't think the predicate is correct -- misuse is still possible by services that do not check the "active" claim's value. Shouldn't the "iss"+"aud" requirements be unconditional?
[New comments on the added text in the diff from -07 to -08.] Section 3 To support encrypted token introspection response JWTs, the authorization server MUST also be provided with the respective resource server encryption keys and algorithms. IIRC, based on some list discussion this text was going to be tweaked to avoid implying that JWE is mandatory. (Unfortunately, this is the thread that evolved into "client certs and TLS Terminating Reverse Proxies", so it's hard to be sure whether I saw any other followups.) The AS MUST restrict the use of client credentials by a RS to the calls it requires, e.g. the AS MAY restrict such a client to call the token introspection endpoint only. How the AS implements this restriction is beyond the scope of this specification. This should probably be clarified a bit more, in the context of "client credentials tend to be used by privileged, fixed endpoints, and the default may just be to allow them all access to all endpoints". Right now it's not clear what's being restricted (and who "it" is that requires calls) Section 5 This specification registers the "application/token- introspection+jwt" media type, which is used as value of the "typ" header parameter of the JWT to indicate that the payload is a token introspection response. Do we also want to note that checking 'jti' is not mandatory and so this does not necessarily provide full protection? (I guess Section 8.1 covers this in more detail.) The value of the "aud" claims MUST identify the resource server receiving the token introspection response. We may want to dig into this a bit more: should there be any relationship between this "aud" value and the "client_id" that an RS might be using (as obtained from dynamic registration)? Does this value need to be different from the audience that is used in access tokens for which this RS is the audience? (Should it be the same?) My instincts lean towards "different" but I would like broader input. exp The "exp" claim indicates when the access token passed in the introspection request will expire. On the face of it this seems divergent from RFC 7519's "the expiration time on or after which the JWT MUST NOT be accepted for processing", though upon further examination the distinction is not quite so large. That is, it's in effect saying that the introspection response should not be accepted for processing after the base token has expired, which usually makes sense. There is a bit of a complication, though, in that the "active" claim implies that we might still have RSes that plan to use the introspection response after the "exp" date has passed, which sounds a lot like a DISCUSS-level internal inconsistency. If possible, the AS MUST narrow down the "scope" value to the scopes relevant to the particular RS. This sounds kind of like a "SHOULD"... The example response header contains the following JSON document: I think this is the JOSE header in the HTTP response (body), not the (HTTP) response header. Section 8.1 As an alternative approach, such an attack can be prevented like any other token substitution attack by restricting the audience of the I'd suggest avoiding describing these as "alternatives"; they seem more like complementary approaches as part of a defense-in-depth solution (especially since we are basically mandating both of them). "aud" value set to the resource server's identifier. Any recipient of an JWT MUST check these values in order to detect substitution attacks. This "MUST" might be out of place -- this is a requirement from RFC 7519, and not an attempt by this document to make new requirements on the behavior of all JWT consumers (if it was, that would be a DISCUSS point!). Resource servers MUST additionally apply the countermeasures against replay as described in [I-D.ietf-oauth-security-topics], section 3.2. In a similar vein, which set of resources servers is this normative "MUST" intended to be binding upon? Section 9 In any case, the AS MUST ensure that the scope of the legal basis is enforced throughout the whole process. The AS MUST retain the scope of the legal basis with the access token, e.g. in the scope value, and the AS MUST determine the data a resource server is allowed to receive based on the resource server's identity and suitable token data, e.g. the scope value. I suspect I'm just being dense, but could you walk me through how the access token "scope" value can encode the legal basis for data transfer?
I support Benjamin's DISCUSS point about the IESG being listed as the change controller for the registry entries. Overall I'd like to understand better the relationship between these registry entries and future updates to OpenID Connect (i.e., if the claims in the OpenID spec change, will this registry automatically need to change as well?). I also support Adam's DISCUSS. How are claims like preferred_username currently used for the described use case of verifying person data to create certificates? If the linkage with the OpenID Connect 1.0 claims remains in the document, I think it would be good to add a note in Section 1.1 or a new Section 1.2 to indicate that the document uses terminology as defined in that spec (e.g., "End-User," "Relying Party," etc.).
I am agreeing with what Alissa said: I support Benjamin's DISCUSS point about the IESG being listed as the change controller for the registry entries. Overall I'd like to understand better the relationship between these registry entries and future updates to OpenID Connect (i.e., if the claims in the OpenID spec change, will this registry automatically need to change as well?). I also support Adam's DISCUSS. How are claims like preferred_username currently used for the described use case of verifying person data to create certificates?
Thanks for addressing my discuss and comments.
Thank you for the hard work put into this easy to read document. I have one single COMMENT (which is more a question) Regards, -éric == COMMENTS == -- Section 1 -- " ... However, there are use cases where the resource server requires stronger assurance that the authorization server issued the access token, including cases where the authorization server assumes liability for the token's content... " C.1) The example given after the above text is not obvious to understand why this memo is required. While I am not an expert on OAuth, some more explanations would probably be useful.