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

Brian Campbell <bcampbell@pingidentity.com> Tue, 09 May 2017 15:13 UTC

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From: Brian Campbell <bcampbell@pingidentity.com>
Date: Tue, 9 May 2017 09:12:24 -0600
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To: Denis <denis.ietf@free.fr>
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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Yes, I omitted your comments in that post because I'd previously replied to
you in a separate message where I said that the "actor_token is a security
token so that's not an issue that needs to be addressed."
https://www.ietf.org/mail-archive/web/oauth/current/msg17247.html

The other point you've just made about having very precise semantics for a
field is a fair one. However, I wanted to avoid introducing yet another
field (or really two fields b/c of the associated *_type for each inbound
token field), for what felt like a minor semantic variation that could be
easily accommodated by the existing framework, to the draft that already
has a lot of options and parameters on the request. And Token Exchange
really is a framework. I think that, to some extent, the framework is a bit
of a Rorschach test for deployers and implementers to utilize to solve
their specific issues and needs. I expect that will be the case regardless.
And I am proposing to somewhat genericize the text around one request
parameter to be more reflective of that.

I would like to hear from others in the WG though.

On Tue, May 9, 2017 at 3:06 AM, Denis <denis.ietf@free.fr> wrote:

> Brian,
>
> You omitted to include my comments in this post. So here it is again:
>
> ===========================================================
>
> The current text is:
>
> actor_token OPTIONAL. A security token that represents the identity of the
> party that is authorized to use the requested security token and act on
> behalf of the subject.
>
> This sentence is indeed wrong since an actor-token is not a security token.
>
> So your proposed change does not solve this issue: actor_token
> OPTIONAL.  A security token that represents the identity of the acting
> party.
>
> The current text states:
>
> Typically, in the request, the subject_token represents the identity of
> the party on behalf of whom
> the token is being requested while the actor_token represents the identity
> of the party to whom the access
> rights of the issued token are being delegated.
>
> Logically, the definition should be along the following lines:
>
>  actor_token OPTIONAL. Indicates the identity of the party to whom the
> access rights of the issued token are being delegated.
>
> If there is no delegation, then this field (which is optional) will not be
> used.
>
> ===========================================================
>
> I read your argumentation, but I maintain my comment. Each field should
> have a precise semantics.
>
> If you want to have another semantics, you should propose to define
> another field with its precise meaning.
>
> Denis
>
> Let me throw out a bit more context about this. The "actor_token" might,
> in a delegation scenario, represent the identity of the party to whom the
> access rights of the issued token are being delegated. That's the typical
> delegation scenario that is discussed in the draft. However, the
> "actor_token" might also be utilized/needed by the AS in an impersonation
> scenario for policy or auditing reasons even when the resulting issued
> token doesn't contain info about the delegation or actor. Similarly, the
> actor might not be strictly doing the impersonation but rather just be a
> party (again maybe needed for policy or auditing) to the token exchange
> event itself.  When I wrote the "actor_token" text in section 2.1 some ~18
> months ago I had the delegation scenario at the front of my mind and
> (clearly) intended to accommodate it. However, I didn't intend to limit it
> to only that and, looking at the text again, I think what is there now is
> too prescriptive and narrow. Thus my proposing to generalize the text
> somewhat.
>
>
>
>
> On Mon, May 8, 2017 at 10:29 AM, Brian Campbell <
> bcampbell@pingidentity.com> wrote:
>
>> 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-exchang
>>>>>> e-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/
>>>>>>
>>>>>> _______________________________________________
>>>>>> OAuth mailing list
>>>>>> OAuth@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/oauth
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> OAuth mailing list
>>>>>> OAuth@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/oauth
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> OAuth mailing list
>>>>>> OAuth@ietf.org
>>>>>> 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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>>>>
>>>
>>
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