Re: [OAUTH-WG] Robert Wilton's No Objection on draft-ietf-oauth-par-08: (with COMMENT)

[Brian Campbell <[e-mail]>]

Thanks for the review Rob. I've endeavored to reply to your comments inline
below.

On Tue, Jun 29, 2021 at 2:54 AM Robert Wilton via Datatracker <noreply@ietf
.org> wrote:

> Robert Wilton has entered the following ballot position for
> draft-ietf-oauth-par-08: No Objection
>
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-oauth-par/
>
>
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> Hi,
>
> Thanks for this document.  Outside my area of expertise, but I have a
> couple of
> questions/comments:
>
> Section 2:
>    Due to historical reasons there is potential ambiguity regarding the
>    appropriate audience value to use when employing JWT client assertion
>    based authentication (defined in Section 2.2 of [RFC7523] with
>    "private_key_jwt" or "client_secret_jwt" authentication method names
>    per Section 9 of [OIDC]).  To address that ambiguity the issuer
>    identifier URL of the authorization server according to [RFC8414]
>    SHOULD be used as the value of the audience.  In order to facilitate
>    interoperability the authorization server MUST accept its issuer
>    identifier, token endpoint URL, or pushed authorization request
>    endpoint URL as values that identify it as an intended audience.
>
> I may be misunderstanding this text, but I note that by giving flexibility
> to
> the client (i.e., the SHOULD) and being strict on the receiver (MUST
> support x,
> y, z), this seems to encourage a proliferation.  Hence, I was wondering
> whether
> this might be better the other way round.  I.e., be strict with what is
> sent,
> and less strict with what is received: MUST send 'issuer identifier', MUST
> receive 'issuer identifier', SHOULD receive 'token endpoint URL' and
> 'pushed
> authorization request endpoint URL'?
>

While definitely not trying to encourage proliferation, the text is aiming
to help interoperability while also accounting for the treatment in other
documents (RFC7523/21) and existing implementations while also allowing for
consistent processing to be implemented across the different endpoints
where JWT client assertion based authentication can be employed. It's kinda
tricky and I don't know for sure that the current text is exactly right but
it's made it through the WG process and seen a number of implementations.



> 2.
>    *  "expires_in" : A JSON number that represents the lifetime of the
>       request URI in seconds as a positive integer.  The request URI
>       lifetime is at the discretion of the authorization server but will
>       typically be relatively short (e.g., between 5 and 600 seconds).
>
> JSON numbers are doubles, but the value is a positive integer.  Does it
> make
> sense to put in a hard limit of 2^53, or given that these are expected to
> be
> small numbers, 2^31 - 1?
>

 I think the soft general guidance is enough and don't believe a hard upper
limit is needed.


3. The success and error examples both define:
>     Content-Type: application/json
>     Cache-Control: no-cache, no-store
>
> The document states that the response should be JSON, but should it more
> specifically specify the content type as "application/json"?


Yeah, it probably should be that specific. I'll add the content type
specificity to the document.



> Similarly, the
> cache control makes sense, but should the document mandate that the
> response
> must include "Cache-Control: no-cache, no-store"?
>

Although it makes sense not to cache I'm less comfortable mandating cache
control stuff - particularly for a response to a POST (that I'm not sure is
ever cacheable anyway) and for a client that is most likely not doing any
caching at all and would immediately encounter failures if it were.


Regards,
> Rob
>
>
>
>

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