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

Brian Campbell <bcampbell@pingidentity.com> Mon, 08 May 2017 16:30 UTC

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From: Brian Campbell <bcampbell@pingidentity.com>
Date: Mon, 8 May 2017 10:29:56 -0600
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To: Rifaat Shekh-Yusef <rifaat.ietf@gmail.com>
Cc: Nat Sakimura <sakimura@gmail.com>, 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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I do have one minor issue I'd like to raise that relates to some
conversations I've been a party to recently about implementations and
applications of token exchange.

I think that the current text in §2.1 for the "actor_token" is overly
specific towards the delegation scenario. I'd propose the language be
generalized somewhat to allow more versatility in applications/deployments
of the token exchange framework. Here's that text:

   actor_token
      OPTIONAL.  A security token that represents the identity of the
      acting party.




On Mon, May 8, 2017 at 8:01 AM, Rifaat Shekh-Yusef <rifaat.ietf@gmail.com>
wrote:

> Hi All,
>
> The last email from Brian addresses the multiple audiences/resources issue
> with an error code, and we did not see any objection to this approach so
> far.
>
>
> *Authors,*
>
> Are there any other open issues with this draft?
> Do you believe it is ready for WGLC?
>
> Thanks,
>  Rifaat & Hannes
>
>
>
> On Fri, Mar 31, 2017 at 11:03 AM, Brian Campbell <
> bcampbell@pingidentity.com> wrote:
>
>> As mentioned during the Chicago meeting the "invalid_target" error code
>> that was added in -07 was intended to give the AS a standard way to reject
>> request with multiple audiences/resources that it doesn't understand or is
>> unwilling or unable to process based on policy or whatever criteria . It
>> was intended as a compromise, of sorts, to allow for the multiple
>> resources/audiences in the request but provide an easy out for the AS of
>> saying it can't be supported based on whatever implementation or security
>> or policy it has.
>>
>> On Tue, Mar 28, 2017 at 1:32 AM, Nat Sakimura <sakimura@gmail.com> wrote:
>>
>>> There are cases where tokens are supposed to be consumed at multiple
>>> places and the `aud` needed to capture them. That's why `aud` is a
>>> multi-valued field.
>>>
>>> On Mon, Mar 27, 2017 at 11:35 AM Torsten Lodderstedt <
>>> torsten@lodderstedt.net> wrote:
>>>
>>>> May I ask you to explain this reason?
>>>>
>>>> Am 27.03.2017 um 08:48 schrieb Mike Jones <Michael.Jones@microsoft.com
>>>> >:
>>>>
>>>> For the same reason that the “aud” claim is multi-valued in JWTs, the
>>>> audience needs to stay multi-valued in Token Exchange.  Ditto for resources.
>>>>
>>>>
>>>>
>>>>                                                        Thanks,
>>>>
>>>>                                                        -- Mike
>>>>
>>>>
>>>>
>>>> *From:* OAuth [mailto:oauth-bounces@ietf.org <oauth-bounces@ietf.org>] *On
>>>> Behalf Of *Brian Campbell
>>>> *Sent:* Monday, March 27, 2017 8:45 AM
>>>> *To:* Torsten Lodderstedt <torsten@lodderstedt.net>
>>>> *Cc:* oauth <oauth@ietf.org>
>>>> *Subject:* Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchang
>>>> e-07.txt
>>>>
>>>>
>>>>
>>>> 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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>>>>
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>> https://www.ietf.org/mailman/listinfo/oauth
>>>>
>>> --
>>>
>>> Nat Sakimura
>>>
>>> Chairman of the Board, OpenID Foundation
>>>
>>> _______________________________________________
>>> OAuth mailing list
>>> OAuth@ietf.org
>>> https://www.ietf.org/mailman/listinfo/oauth
>>>
>>>
>>
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>>
>