Re: [OAUTH-WG] swapping a jwsreq/JAR JWT for a client authentication JWT

[Brian Campbell <[e-mail]>]

Because it wouldn't actually prevent it in this case due to JWT assertion
client authentication (a.k.a. private_key_jwt) having come about well
before the JWT BCP and the established concept of using the 'typ' header to
prevent cross-JWT confusion. Thus there's no validation rule regarding the
'typ' header defined in RFC 7523 for JWT client authentication. Explicitly
typing the request object JWT doesn't do anything to prevent it from being
used in the context of previously existing JWT applications like client
auth.

On Wed, Jul 22, 2020 at 10:32 AM Dominick Baier <[e-mail]>
wrote:

> Why not use a typ header as suggested by the JWT BCP?
>
> ———
> Dominick Baier
>
> On 22. July 2020 at 17:37:41, Brian Campbell (
> bcampbell=[e-mail]) wrote:
>
> The TL;DR here is a somewhat tentative suggestion that a brief security
> consideration be added to
> https://datatracker.ietf.org/doc/draft-ietf-oauth-jwsreq/
> <https://datatracker..ietf.org/doc/draft-ietf-oauth-jwsreq/> that
> prohibits the inclusion of a 'sub' claim containing the client id value in
> the request object JWT so as to prevent the request object JWT (which is
> exposed to the user agent) from being erroneously accepted as a valid JWT
> for client authentication.
>
> Some more details and the discussion that led to this here email can be
> found at https://github.com/oauthstuff/draft-oauth-par/issues/41
>
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