Re: [OAUTH-WG] Fwd: New Version Notification for draft-lodderstedt-oauth-rar-02.txt

Hi Torsten,

Overall I am a fan of a way to provide more structure in authorization
requests, and I'm excited to see this draft, so thanks for that.

I do have some concerns about one aspect of this. Given its clear
intended use as a way to create authorization requests to do things
like transfer money between bank accounts, I don't think it's
appropriate for that kind of data to be sent in the front channel at
all. By encoding a rich authorization request with bank account
numbers and account names in a query string, that opens up several new
opportunities for an attacker to steal private/sensitive information
(browser extensions, proxy servers, etc).

This differs from the plain OAuth authorization request because
traditionally the request does not include any identifying information
about any user or even about the particular transaction. At most, the
request identifies the client and combination of coarse-grained scopes
the client is requesting, none of which can identify a user. However
with the examples provided in this document, as well as many
additional uses of this mechanism, it includes potentially a lot of
identifying information about users including their name, bank account
numbers, and even relationships to other parties (e.g. creditorName).
When the authorization request is sent to the AS in a URL, regardless
of whether it's in plaintext like the simple example here, or signed
as a JWT request, that data is visible to anything that can access the
URL between the user's device and the AS. This seems like a huge
potential for a privacy leak.

I realize this draft currently points to JWT Secured Authorization
Requests (JAR) in several places where these concerns come up. The
problem is that JAR doesn't actually *require* an encrypted JWT, so
the privacy implications aren't accounted for here.

I would much rather see this document require your other recent
submission, Pushed Authorization Requests. Given the privacy
implications, it makes sense to limit the use of rich authorization
requests to pushed authorization requests, so that this rich data is
never made available to intermediaries in the front channel.

If there is a good reason to continue allowing authorization requests
as a GET without the new pushed request step, then at least I would
want to see RAR require encrypted JWTs as described by JAR.

Thanks for considering this!

----
Aaron Parecki
aaronparecki.com

On Sat, Sep 21, 2019 at 7:51 PM Torsten Lodderstedt
<torsten@lodderstedt.net> wrote:
>
> Hi all,
>
> I just published a draft about “OAuth 2.0 Rich Authorization Requests” (formerly known as “structured scopes”).
>
> https://tools.ietf.org/html/draft-lodderstedt-oauth-rar-02
>
> It specifies a new parameter “authorization_details" that is used to carry fine grained authorization data in the OAuth authorization request. This mechanisms was designed based on experiences gathered in the field of open banking, e.g. PSD2, and is intended to make the implementation of rich and transaction oriented authorization requests much easier than with current OAuth 2.0.
>
> I’m happy that Justin Richer and Brian Campbell joined me as authors of this draft. We would would like to thank Daniel Fett, Sebastian Ebling, Dave Tonge, Mike Jones, Nat Sakimura, and Rob Otto for their valuable feedback during the preparation of this draft.
>
> We look forward to getting your feedback.
>
> kind regards,
> Torsten.
>
> Begin forwarded message:
>
> From: internet-drafts@ietf.org
> Subject: New Version Notification for draft-lodderstedt-oauth-rar-02.txt
> Date: 21. September 2019 at 16:10:48 CEST
> To: "Justin Richer" <ietf@justin.richer.org>, "Torsten Lodderstedt" <torsten@lodderstedt.net>, "Brian Campbell" <bcampbell@pingidentity.com>
>
>
> A new version of I-D, draft-lodderstedt-oauth-rar-02.txt
> has been successfully submitted by Torsten Lodderstedt and posted to the
> IETF repository.
>
> Name: draft-lodderstedt-oauth-rar
> Revision: 02
> Title: OAuth 2.0 Rich Authorization Requests
> Document date: 2019-09-20
> Group: Individual Submission
> Pages: 16
> URL:            https://www.ietf.org/internet-drafts/draft-lodderstedt-oauth-rar-02.txt
> Status:         https://datatracker.ietf.org/doc/draft-lodderstedt-oauth-rar/
> Htmlized:       https://tools.ietf.org/html/draft-lodderstedt-oauth-rar-02
> Htmlized:       https://datatracker.ietf.org/doc/html/draft-lodderstedt-oauth-rar
> Diff:           https://www.ietf.org/rfcdiff?url2=draft-lodderstedt-oauth-rar-02
>
> Abstract:
>   This document specifies a new parameter "authorization_details" that
>   is used to carry fine grained authorization data in the OAuth
>   authorization request.
>
>
>
>
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> The IETF Secretariat
>
>
> _______________________________________________
> OAuth mailing list
> OAuth@ietf.org
> https://www.ietf.org/mailman/listinfo/oauth