Re: [GNAP] Authentication mechanisms discovery

[Tom Jones <[e-mail]>]

If anyone is interested in contributing to a Mobile Authentication
Assurance Statement, let me know.
We have one in process now in Kantara. It's our view that it would just be
a signed jwt that could be included anywhere it was needed.
Peace ..tom


On Mon, Aug 24, 2020 at 1:12 PM Justin Richer <[e-mail]> wrote:

> Denis, thanks for writing this up. I don’t think we want to get into the
> business of defining what an API should do for service and capability
> discovery, especially since there are a wide variety of API patterns and
> styles out there, each with their own discovery principles. I agree with
> Dick that the right way to approach this is likely to use the
> “WWW-Authenticate” header response, which is what I’ve proposed as a straw
> man in section 10.4 of XYZ:
>
>
> https://tools.ietf.org/html/draft-richer-transactional-authz-09#section-10.4
>
> For use cases like yours where the client starts at the RS, this makes a
> lot of sense and the RS can point the client toward the AS it should be
> using, and even tell it what kind of thing it needs to ask for next.
> There’s a lot of work we can do there to make that robust and useful.
>
> But, just like AS discovery, I think that’s an optimization for cases
> where that information isn’t known by some other means. It’s my stance
> that, wherever possible, discovery should be an optional add-on to let
> software optimize the experience, not something required for the protocol
> to work. “Discovery” and “registration” assume a mostly-static world, where
> sysadmins are making security decisions ahead of time and assigning
> identifiers to those decisions. I think that if we take a step back and
> look at the fundamentals of what we’re trying to solve here, we don’t
> actually need discovery or registration a lot of the time, and certainly
> not as add-ons like they are in OAuth 2.
>
> When I wrote XYZ, one of the goals was for it to be “dynamic first”, so
> that the client and server wouldn’t :need: to know anything about each
> other ahead of time in order for the core protocol to work. Now of course,
> in many cases, the AS is only going to trust calls from keys that it’s seen
> as part of a static registration record, and a client is going to be
> configured or programmed to only take actions that are available at the AS
> it’s been written to talk to. But it’s important to me that these cases are
> optimizations on the overall protocol, which (unlike OAuth) doesn’t assume
> a discovery or registration step happened out of band first.
>
> In today’s world, we’ve got so many signals that software can send each
> other at runtime that can be processed and likely trusted much more than a
> static discovery/registration ever could. The client can send over device
> posture, organizational affiliation attestations, verifiable credentials of
> the current user (without the AS ever seeing the user), derived credentials
> that are tied to some external trusted registry (think of a CA style model
> but for more than certificates), or any number of other signals that people
> are using and building. None of these lend themselves to OAuth’s “client_id
> is required everywhere” model, which was built around a notion of two web
> sites talking to each other. That’s why I think we should not only be
> getting away from the discovery/registration mindset and towards a
> dynamic-first negotiated protocol which can, in turn, be optimized in a
> secure and clean fashion.
>
>  — Justin
>
> On Aug 24, 2020, at 4:16 AM, Denis <[e-mail]> wrote:
>
>
> Hi Dick
> *, *
>
> The following comments have been elaborated after an analysis of your
> draft: draft-hardt-xauth-protocol-13.
>
> *1 ) Authentication mechanisms discovery at the GS*
>
> Sections 3 and 3.7 from draft-hardt-xauth-protocol-13 are proposing to
> support an HTTP OPTIONS request which would be the first request
> when talking to a GS. The goal is to be able to query the authentication
> mechanisms supported by the GS. This would indeed be very useful.
>
> The HTTP OPTIONS request has been first defined in RFC 2616 and refined in
> RFC 7231 (see https://tools.ietf.org/html/rfc7231#section-4.3.7).
>
> RFC 7231 mentions:
>
>       A standard format for such a representation is not defined by this
> specification, but might be defined by future extensions to HTTP.
>       A client that generates an OPTIONS request containing a payload body
> MUST send a valid Content-Type header field describing
>       the representation media type.  Although this specification does
> not define any use for such a payload, future extensions to HTTP
>       might use the OPTIONS body to make more detailed queries about the
> target resource.
>
> RFC 7231 also mentions:
>
>       A server generating a successful response to OPTIONS SHOULD send an
> header fields that might indicate optional features
>       implemented by the server and applicable to the target resource,
> including potential extensions not defined by this specification.
>
> However, two types of authentication are possible: user authentication and
> client authentication. If both are supported by the GS, it would be
> possible
> to address this concern either by returning two lists of authentication
> methods or even better by using two different Content-Type header fields
> describing
> the representation media type, since the client is knowing whether it is
> acting or not on behalf of a User.
>
> *2) Authentication mechanisms discovery at the RS*
>
> This HTTP OPTIONS request should also be supported by a RS. When a client
> first contacts a RS, it does not necessarily know the authentication
> methods that are *currently* supported by the RS. This means that the
> same request as the one used for the GS should be available for a RS as
> well.
>
> Denis
>
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