Re: [GNAP] [Txauth] Revisiting the photo sharing example (a driving use case for the creation of OAuth)

Dick Hardt <dick.hardt@gmail.com> Thu, 13 August 2020 15:59 UTC

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From: Dick Hardt <dick.hardt@gmail.com>
Date: Thu, 13 Aug 2020 08:59:05 -0700
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To: Justin Richer <jricher@mit.edu>
Cc: Fabien Imbault <fabien.imbault@gmail.com>, Denis <denis.ietf@free.fr>, "txauth@ietf.org" <txauth@ietf.org>, Francis Pouatcha <fpo@adorsys.de>, Benjamin Kaduk <kaduk@mit.edu>
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Subject: Re: [GNAP] [Txauth] Revisiting the photo sharing example (a driving use case for the creation of OAuth)
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A browser redirect has not been the only way that OAuth has worked. I
presented about device flows at IETF when I presented OAuth WRAP.

I do think the terms back channel and front channel are unlikely to be
helpful in the GNAP work.

My point was user awareness rather than protocol.

For example, a site making back channel calls to verify a user from a
"source" vs a front channel where the user is involved in consenting to the
release of data from a "source".


ᐧ

On Thu, Aug 13, 2020 at 8:52 AM Justin Richer <jricher@mit.edu> wrote:

> That’s true when the front channel (redirects between parties) is used as
> the method for interaction, but the point I was making is that that method
> isn’t going to be the only way that interaction happens. I don’t think it’s
> helpful to conflate other interaction mechanisms that don’t use
> redirections with URIs and query parameters as “front channel” here. The
> security models and surrounding assumptions are very different.
>
>  — Justin
>
> On Aug 13, 2020, at 11:40 AM, Dick Hardt <dick.hardt@gmail.com> wrote:
>
> I've often thought of front channel as an interaction visible to the user,
> and back channel as being between two software systems, in this case, the
> client and GS.
>
> Consent from the user is the front channel, independent of how the user
> gets to the GS, or if an app is part of the GS, or is the GS.
> ᐧ
>
> On Thu, Aug 13, 2020 at 8:34 AM Fabien Imbault <fabien.imbault@gmail.com>
> wrote:
>
>> Indeed.
>>
>> On Thu, Aug 13, 2020 at 5:33 PM Justin Richer <jricher@mit.edu> wrote:
>>
>>> A point I forgot to make below: the “front channel” isn’t going to exist
>>> for a lot of systems anymore, where interaction happens through an app or
>>> communication happens through some separate communication fabric. So there
>>> are cases, just like in OAuth 2, where there’s only a “back channel” and
>>> the other aspect of the AS never comes into play.
>>>
>>>  — Justin
>>>
>>> On Aug 13, 2020, at 11:17 AM, Fabien Imbault <fabien.imbault@gmail.com>
>>> wrote:
>>>
>>> Without surprise, +1 to differentiate between the back-channel and the
>>> front-channel.
>>>
>>> On Thu, Aug 13, 2020 at 5:15 PM Justin Richer <jricher@mit.edu> wrote:
>>>
>>>> Denis, I want to focus on one point here:
>>>>
>>>> In OAuth 2.0, the user consent is performed by the AS using an
>>>> authorize endpoint where the user consent is solicited and captured.
>>>>
>>>> Since a user, with no prior experience, shall first connect to a RS to
>>>> perform an operation, the user consent shall be performed by the RS,
>>>> instead of the AS. This means that we should define a "consent"
>>>> endpoint at the RS.
>>>>
>>>>
>>>> One of my goals with XYZ’s design was to be able to separate the
>>>> interaction with the user from the web-based flows for the delegation
>>>> protocol, and that aspect is enshrined in the GNAP charter as well.
>>>>
>>>> It points to the reality that there are two different aspects of the
>>>> traditional AS that we might need to talk about separately now. One deals
>>>> with delegation, issuing tokens, returning data directly to the client (not
>>>> through a separate API, since that’s the RS), and other back-channel stuff.
>>>> The other aspect deals with interacting with the user and/or resource
>>>> owner.
>>>>
>>>> We already saw bits of this in OAuth 2: the AS is defined by the pair
>>>> of the token endpoint and authorization endpoint, each filling the
>>>> respective roles above. What if we formally separate these? Strawman names:
>>>>
>>>>
>>>> Delegation Server (DS) - handles the back-channel stuff
>>>>
>>>> Interaction Server (IS) - handles the front-channel stuff
>>>>
>>>>
>>>>  — Justin
>>>>
>>>> --
>>>> TXAuth mailing list
>>>> TXAuth@ietf.org
>>>> https://www.ietf.org/mailman/listinfo/txauth
>>>>
>>>
>>>
>