Re: [OAUTH-WG] WGLC for DPoP Document

Thanks for an excellent work.
I am happy that the public key confirmation method in JPOP [1] presented at
IETF OAuth WG in 2017 somewhat morphed into DPOP after 5 years. Also, I was
very happy to see the

[1] https://datatracker.ietf.org/doc/html/draft-sakimura-oauth-jpop-00

I also apologize that due to circumstances, I was not able to contribute
much to the work during the time. It is almost the first read for me so
perhaps I could be completely off, but it may also provide the questions
that a new reader may pose.

Here is a set of comments that came to my mind while reading the draft.

   1. It was not immediately clear how the client_id is found from the DPoP
   token request. In the case of JWT Client Authentication, it has `iss` in it
   showing the client_id. In DPoP, it does not, so I am wondering how. Some
   explanatory text would help.
   2. It was not immediately clear how the binding between the key material
   presented in the DPoP header in the token request and the client_id is
   checked. This is critical from the security point of view so if it could be
   explained early on, perhaps in the first paragraph of section 5, it would
   be great.
   3. In Figure 8, it would be great if "cnf" member is formatted as an
   indented JSON member rather than an inline one as it stands.
   4. In Figure 10, it would be great if "cnf" member is formatted as an
   indented JSON member rather than an inline one as it stands.
   5. DPoP Proof Replay described in 11.1 talks about limiting the validity
   period as the mitigation. However, in the case of DPoP Proof Phishing via
   MITM adversary, it is entirely possible that it is only used once, in time,
   by the adversary. So, adding some guidance on server authentication might
   be good to add.

I might come up with some additional ones by the deadline, but for now, the
above is what I have.

Cheers,

Nat Sakimura

On Mon, Mar 28, 2022 at 9:01 PM Rifaat Shekh-Yusef <rifaat.s.ietf@gmail.com>
wrote:

> All,
>
> As discussed during the IETF meeting in *Vienna* last week, this is a *WG
> Last Call *for the *DPoP* document:
> https://datatracker.ietf.org/doc/draft-ietf-oauth-dpop/
>
> Please, provide your feedback on the mailing list by April 11th.
>
> Regards,
>  Rifaat & Hannes
>
> _______________________________________________
> OAuth mailing list
> OAuth@ietf.org
> https://www.ietf.org/mailman/listinfo/oauth
>

-- 
Nat Sakimura (=nat)
Chairman, OpenID Foundation
http://nat.sakimura.org/
@_nat_en