Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchange-07.txt

Brian Campbell <bcampbell@pingidentity.com> Mon, 27 March 2017 13:45 UTC

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From: Brian Campbell <bcampbell@pingidentity.com>
Date: Mon, 27 Mar 2017 08:44:33 -0500
Message-ID: <CA+k3eCTjmifjsbec80vGTE5Hw4ws7oARuaatDk4RYOLK26-87Q@mail.gmail.com>
To: Torsten Lodderstedt <torsten@lodderstedt.net>
Cc: oauth <oauth@ietf.org>
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Subject: Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchange-07.txt
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Thanks for the review and question, Torsten.

The desire to support multiple audience/resource values in the request came
up during a review and discussion among the authors of the document when
preparing the -03 draft. As I recall, it was said that both Salesforce and
Microsoft had use-cases for it. I incorporated support for it into the
draft acting in the role of editor.

>From an individual perspective, I tend to agree with you that allowing for
multiple audiences/resources adds a lot of complexity that's like not
needed in many (or most) cases. And I would personally be open to making
audience and resource mutual exclusive and single valued. A question for
the WG I suppose.

The "invalid_target" error code that was added in -07 was intended to give
the AS a standard way to deal with the complexity and reject request with
multiple audiences/resources that it doesn't understand or is unwilling or
unable to process. It was intended as a compromise, of sorts, to allow for
the multiples but provide an easy out of saying it can't be supported based
on whatever implementation or policy of the AS.




On Sun, Mar 26, 2017 at 9:00 AM, Torsten Lodderstedt <
torsten@lodderstedt.net> wrote:

> Hi Brian,
>
> thanks for the clarification around resource, audience and scope.
>
> Here are my comments on the draft:
>
> In section 2.1 it states: „Multiple "resource" parameters may be used to
> indicate
>       that the issued token is intended to be used at the multiple
>       resources listed.“
>
> Can you please explain the rational in more detail? I don’t understand why
> there is a need to ask for access tokens, which are good for multiple
> resources at once. This is a request type more or less exclusively used in
> server to server scenarios, right? So the only reason I can think of is
> call reduction.
>
> On the other side, this feature increases the AS's complexity, e.g. its
> policy may prohibit to issue tokens for multiple resources in general or
> the particular set the client is asking for. How shall the AS handles such
> cases?
>
> And it is getting even more complicated given there could also be multiple
> audience values and the client could mix them:
>
> "Multiple "audience" parameters
>       may be used to indicate that the issued token is intended to be
>       used at the multiple audiences listed.  The "audience" and
>       "resource" parameters may be used together to indicate multiple
>       target services with a mix of logical names and physical
>       locations.“
>
> And in the end the client may add some scope values to the „meal“, which
> brings us to
>
> „Effectively, the requested access rights of the
>    token are the cartesian product of all the scopes at all the target
>    services."
>
> I personally would suggest to drop support for multiple audience and
> resource parameters and make audience and resource mutual exclusive. I
> think this is sufficient and much easier to implement.
>
> kind regards,
> Torsten.
>
>
> Am 11.01.2017 um 20:04 schrieb Brian Campbell <bcampbell@pingidentity.com
> >:
>
> Draft -07 of "OAuth 2.0 Token Exchange" has been published. The primary
> change in -07 is the addition of a description of the relationship between
> audience/resource/scope, which was a request or comment that came up during
> the f2f meeting in Seoul.
>
> Excerpted from the Document History:
>
>    -07
>
>    o  Fixed typo (desecration -> discretion).
>    o  Added an explanation of the relationship between scope, audience
>       and resource in the request and added an "invalid_target" error
>       code enabling the AS to tell the client that the requested
>       audiences/resources were too broad.
>
>
> ---------- Forwarded message ----------
> From: <internet-drafts@ietf.org>
> Date: Wed, Jan 11, 2017 at 12:00 PM
> Subject: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchange-07.txt
> To: i-d-announce@ietf.org
> Cc: oauth@ietf.org
>
>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the Web Authorization Protocol of the IETF.
>
>         Title           : OAuth 2.0 Token Exchange
>         Authors         : Michael B. Jones
>                           Anthony Nadalin
>                           Brian Campbell
>                           John Bradley
>                           Chuck Mortimore
>         Filename        : draft-ietf-oauth-token-exchange-07.txt
>         Pages           : 31
>         Date            : 2017-01-11
>
> Abstract:
>    This specification defines a protocol for an HTTP- and JSON- based
>    Security Token Service (STS) by defining how to request and obtain
>    security tokens from OAuth 2.0 authorization servers, including
>    security tokens employing impersonation and delegation.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-oauth-token-exchange/
>
> There's also a htmlized version available at:
> https://tools.ietf.org/html/draft-ietf-oauth-token-exchange-07
>
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-oauth-token-exchange-07
>
>
> 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.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
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