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

[Brian Campbell <[e-mail]>]

In hindsight, yeah, having explicit JWT typing everywhere would be nice..
But retrofitting would be a very major undertaking, which I don't think
could reasonably be justified considering cost–benefit.

I can't speak directly for the Jwsreq authors but I suspect considerations
around backward/forward compatibility with OIDC's JWT request and even
existing implementations of the Jwsreq draft that has been in draft forever
came into play.

On Wed, Jul 22, 2020 at 11:38 PM Dominick Baier <[e-mail]>
wrote:

> Even more. Jwsreq should have it. But the authors decided against it.
>
> ———
> Dominick Baier
>
> On 23. July 2020 at 07:38:04, Dominick Baier ([e-mail])
> wrote:
>
> Good point. Thanks, Brian.
>
> We should retrofit typs everywhere..in hindsight.
>
> ———
> Dominick Baier
>
> On 22. July 2020 at 23:55:20, Brian Campbell ([e-mail])
> wrote:
>
> 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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