Re: [OAUTH-WG] [UNVERIFIED SENDER] Re: [UNVERIFIED SENDER] Re: PAR: pushed requests must become JWTs

["Richard Backman, Annabelle" <[e-mail]>]

We’ve already defined a request identifier parameter. We called it “request_uri”. That’s what the “I” in URI stands for. Let’s just fix the semantics on that one. It’s bad enough that we have request and request_uri, let’s not add a third one.

Sent from my iPhone

On Jan 16, 2020, at 9:33 AM, Justin Richer <[e-mail]> wrote:

 What you’ve described is exactly what happens in XYZ:

https://oauth.xyz/interaction/

And this is what we’re discussing as the basis in TxAuth. But in this case since you’re stuck with OAuth 2’s authorization endpoint syntax and semantics, you’re still limited with what’s happening there and it could come with its own security oddities (like maybe a new form of a mixup attack?) that we haven’t figured out yet. Like, is the AS allowed to send the client to something other than its own authorization endpoint? Is the client supposed to validate the syntax of the authorization endpoint URL against its discovery document? It deeply changes what OAuth 2 does, and that makes it really hard to add on.

Using request_uri to pass the artifact is clever, but I also like Torsten’s idea of using a new field defined by PAR to pass the artifact. Granted, in the Authlete implementation of PAR, we were able to re-use a whole bunch of code for processing request objects, and that was pretty nice. Still, the issues with JAR are non-zero, and so we need to figure out whether we should fully decouple or fix the issues. I’m in favor of fixing things and using these together, but there’s a lot of inertia against that.

 — Justin

On Jan 16, 2020, at 11:36 AM, Neil Madden <[e-mail]<mailto:[e-mail]>> wrote:

Why not have the PAR endpoint return a 30x redirect with the full URL to the authorization endpoint in the Location header? That way the AS can decide for itself how to communicate any id from the PAR endpoint to the authorization endpoint.

This also has the side effect that you can kick off an OAuth2 flow with a simple HTML form pointed at the PAR endpoint (with hidden fields for state/code_challenge etc).

If actually performing the redirect is a bit problematic then at least the idea of returning a full URL for the authorization endpoint (hyperlink) rather than returning an id/URI and requiring the client to construct one seems reasonable to me and would seem to avoid some of the difficulties being discussed with JAR etc as the exact mechanism of communication becomes an implementation detail that the client needn't know about.

-- Neil

On 16 Jan 2020, at 16:25, Torsten Lodderstedt <torsten=[e-mail]<mailto:torsten=[e-mail]>> wrote:

I just thought about another option. What if we change PAR to not use the request_uri parameter but a new parameter, e.g. request_id?

That would decouple both specs. The reason why we use request_uri was to make the life of clients easier since they can use the standard library function for request objects to pass the PAR reference to the AS. Is this worth the trouble?

Am 16.01.2020 um 16:48 schrieb Justin Richer <[e-mail]<mailto:[e-mail]>>:

+1 to this approach, and it sounds like JAR might need to come back to go through another round anyway thanks to the breaking changes the IESG pushed into it after it left WGLC.

I’d rather see us get this right than publish something many of us think is broken.

Maybe PAR and JAR (and JARM?) end up going out as a bundle of specs.

 — Justin

On Jan 15, 2020, at 8:30 PM, Richard Backman, Annabelle <[e-mail]<mailto:[e-mail]>> wrote:

The problem is the JWT requirement in JAR, not how we talk about PAR request_uri values in PAR. We need to either change the language in JAR (see my suggestions elsewhere in this thread), or add text in PAR that explicitly exempts PAR request_uri values (or preferably all AS-provided request_uri values) from this requirement (also see my suggestions elsewhere in this thread).

My preference remains the former. It strikes me as bad form for one extension to override normative requirements laid out in another document. Granted, the incompatibility scenarios introduced by this retcon are edge-case at best, but that just raises the question of why we can’t fix the draft that hasn’t actually been published yet.

–
Annabelle Richard Backman
AWS Identity


From: OAuth <[e-mail]<mailto:[e-mail]>> on behalf of Vladimir Dzhuvinov <[e-mail]<mailto:[e-mail]>>
Organization: Connect2id Ltd..
Date: Wednesday, January 15, 2020 at 12:34 PM
To: Justin Richer <[e-mail]<mailto:[e-mail]>>
Cc: oauth <[e-mail]<mailto:[e-mail]>>, Nat Sakimura <[e-mail]<mailto:[e-mail]>>, "Richard Backman, Annabelle" <richanna=[e-mail]<mailto:richanna=[e-mail]>>
Subject: Re: [OAUTH-WG] [UNVERIFIED SENDER] Re: PAR: pushed requests must become JWTs

On 13/01/2020 19:32, Justin Richer wrote:
To be clear, I’m not saying we suggest a particular form, and I agree that we shouldn’t specify that “it’s a JWT” or something of that nature. But if we call the result of PAR “thing X” and the target of request_uri “thing X” in JAR, then we’re compatible without saying what “thing X” needs to be in all cases.
Good, we're on the same page then.
How about simply saying that the result of PAR is an URI referencing the pushed authZ request; at the authZ endpoint its processing is completed.
No need is both clear and abstract enough to not require a form to be specified.

In cases where you do a remote look up, we want “thing X” to be formatted as a JWT.
But why?
Both PAR and authZ endpoints belong to the AS, which makes that impl specific. The URI is the contract, between client and AS.
The AS, if uService based, could choose to implement that as CBOR Web Token, or some other verifiable blob, resulting in the same essential function, and this isn't affecting the client <-> AS contract in any way.

We had a case of similarly unintentional limiting in JAR previously, saying that you had to do an HTTP lookup on the request_uri, but I believe that’s been backed off now and made conditional.
That was precisely my point.
Vladimir


 — Justin


On Jan 11, 2020, at 5:28 AM, Vladimir Dzhuvinov <[e-mail]<mailto:[e-mail]>> wrote:

My suggestion is to abstain from specifying the concrete form of the resource pointed to by the PAR URI. Regardless of URI type (URN, downloadable https URL or something else), and even if the PAR endpoint and the authZ endpoint are managed by two different entities (microservice or other scenario).
In the Connect2id implementation of PAR the returned URI doesn't point to a request object and it doesn't point to a JWT either. It points to an internally stored "pre-processed" authZ request, which the authZ endpoint then picks up to complete the authZ.
Even if we eventually end up in microservice world, or allow the PAR endpoint to be managed by some external entity, the PAR URI - its interpretation, validation and potentially resource retrieval (JWT or other blob), is an "internal contract" on the AS side. This doesn't concern the client, and in OAuth 2.0 the role of AS is indivisible.

I see PAR request + authZ request as one logical OAuth 2.0 authZ request: the client submits an authZ request and gets an authZ response at the end. The URI is necessary for the client to proceed from the 1st to the 2nd step. If we manage to frame / word the PAR URI in this logical way, without getting stuck in the JAR definition / framing of what the request_uri / object is, it would be great.

The normative language I think should focus on maintaining the OAuth 2.0 contract for the entire logical authZ request, together with the basic contracts of 1) JAR and the 2) authZ endpoint.

Vladimir

On 10/01/2020 22:55, Justin Richer wrote:
So we could solve this by saying the resulting data object of a PAR is a request object. Which might also contain a request object internally as well. In that case JAR should back off from saying it’s a JWT and instead say it’s a request object. Or we define a new term for this authorization request blob thing.

Or PAR could at least say that if it’s dereferenced over a remote protocol then it MUST be a JWT, but otherwise it can be whatever you want. That’s where the real interop concerns come in.

 — Justin


On Jan 10, 2020, at 3:41 PM, Richard Backman, Annabelle <richanna=[e-mail]<mailto:richanna=[e-mail]>> wrote:

Correct. The problem becomes pretty clear in the context of PAR, where the AS is generating and vending out the URI at the PAR endpoint, and consuming it at the authorization endpoint. From an interoperability standpoint, it’s analogous to the AS vending an authorization code at the authorization endpoint and consuming it at the token endpoint.
–
Annabelle Richard Backman
AWS Identity


From: John Bradley <[e-mail]<mailto:[e-mail]>>
Date: Friday, January 10, 2020 at 12:29 PM
To: Brian Campbell <[e-mail]<mailto:[e-mail]>>
Cc: Torsten Lodderstedt <[e-mail]<mailto:[e-mail]>>, Nat Sakimura <[e-mail]<mailto:[e-mail]>>, "Richard Backman, Annabelle" <[e-mail]<mailto:[e-mail]>>, oauth <[e-mail]<mailto:[e-mail]>>
Subject: [UNVERIFIED SENDER] Re: [OAUTH-WG] PAR: pushed requests must become JWTs

If we assume the client posts a JAR and gets back a reference.  Then the reference is to a JAR.

I think I see the problem.  If the server providing the reference is associated with the AS then the server dosen't need to dereference the object via HTTP, so it could be a URN as an example.

So yes it is not a interoperability issue for the client.

I will think about how I can finesse that.

I agree it is not a change in intent.

I will see if I can get our AD to accept that.

John B.




On Fri, Jan 10, 2020, 4:57 PM Brian Campbell <[e-mail]<mailto:[e-mail]>> wrote:
Sure but the text proposed (or something like it) qualifies it such that there aren't interoperability questions because it's only an implementation detail to the AS who both produces the URI and consumes its content.

On Fri, Jan 10, 2020 at 12:48 PM John Bradley <[e-mail]<mailto:[e-mail]>> wrote:
It may be a challenge to change text saying that the contents of the resource could be something other than a request object.

If not a request object then what and how is that interoperable are likely AD questions.

I could perhaps see changing it to must be a request object, or other format defined by a profile.

John B.


On Fri, Jan 10, 2020, 3:45 PM Brian Campbell <[e-mail]<mailto:[e-mail]>> wrote:
Agree and agree. But given that the change suggested by Annabelle has no impact on the client or interoperability, perhaps Nat or John could work the change into the draft during the edits that happen during the final stages of things?

On Thu, Jan 9, 2020 at 1:56 AM Torsten Lodderstedt <torsten=[e-mail]<mailto:[e-mail]>> wrote:
I would assume given the status of JAR, we don’t want to change it. And as I said, this difference does not impact interoperability from client perspective.



Am 09.01.2020 um 00:58 schrieb Richard Backman, Annabelle <richanna=[e-mail]<mailto:[e-mail]>>:
It would be more appropriate to add the text to JAR rather than PAR. It doesn't seem right for PAR to retcon rules in JAR. Moving the text to JAR also highlights the weirdness of giving PAR special treatment.

What if we changed this sentence in Section 5.2 of JAR:
The contents of the resource referenced by the URI MUST be a Request
Object.

To:
The contents of the resource referenced by the URI MUST be a Request
Object, unless the URI was provided to the client by the Authorization
Server.

This would allow for use cases such as an AS that provides pre-defined request URIs, or vends request URIs via a client management console, or bakes them into their client apps.

–
Annabelle Richard Backman
AWS Identity

On 1/8/20, 2:50 PM, "Torsten Lodderstedt" <torsten=[e-mail]<mailto:[e-mail]>> wrote:

    Hi,

    you are right, PAR does not require the AS to represent the request as a JWT-based request object. The URI is used as internal reference only. That why the draft states

    "There is no need to make the
          authorization request data available to other parties via this
          URI.”

    This difference matters from an AS implementation perspective, it doesn't matter from a client's (interop) perspective.

    We may add a statement to PAR saying that request_uris issued by the PAR mechanism (MAY) deviate from the JAR definition.

    best regards,
    Torsten.

    > On 8. Jan 2020, at 23:42, Richard Backman, Annabelle <richanna=[e-mail]<mailto:[e-mail]>> wrote:
    >
    > Hi all,
    >
    > The current drafts of PAR (-00) and JAR (-20) require that the AS transform all pushed requests into JWTs. This requirement arises from the following:
    >         • PAR uses the request_uri parameter defined in JAR to communicate the pushed request to the authorization endpoint.
    >         • According to JAR, the resource referenced by request_uri MUST be a Request Object. (Section 5.2)
    >         • Request Object is defined to be a JWT containing all the authorization request parameters. (Section 2.1)
    >
    > There is no need for this requirement to support interoperability, as this is internal to the AS. It is also inconsistent with the rest of JAR, which avoids attempting to define the internal communications between the two AS endpoints. Worse, this restriction makes it harder for the authorization endpoint to leverage validation and other work performed at the PAR endpoint, as the state or outcome of that work must be forced into the JWT format (or retrieved via a subsequent service call or database lookup).
    >
    > –
    > Annabelle Richard Backman
    > AWS Identity
    >
    > _______________________________________________
    > OAuth mailing list
    > OAuth@ietf..org<mailto:[e-mail]>
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