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

Brian Campbell <bcampbell@pingidentity.com> Fri, 02 June 2017 19:20 UTC

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From: Brian Campbell <bcampbell@pingidentity.com>
Date: Fri, 2 Jun 2017 13:19:29 -0600
Message-ID: <CA+k3eCSeUaYDGTCG49TUMJ+KbgaSsALcqWj7sf66mvtON2ijWA@mail.gmail.com>
To: Rifaat Shekh-Yusef <rifaat.ietf@gmail.com>
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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Sure thing Rifaat, here it is:
https://mailarchive.ietf.org/arch/msg/oauth/svrY2VEiYAJClftN8y1oQ1p4rVw

On Fri, Jun 2, 2017 at 6:08 AM, Rifaat Shekh-Yusef <rifaat.ietf@gmail.com>
wrote:

> Brian,
>
> We did not see any objection to this latest proposal.
>
> Can you please go ahead and publish version -08 of the draft?
> We would like to start a WGLC on the new version.
>
> Regards,
>  Rifaat
>
>
> On Fri, May 26, 2017 at 6:21 PM, Brian Campbell <
> bcampbell@pingidentity.com> wrote:
>
>> Following up on this, I'd like to propose a different and less invasive
>> change to the "actor_token" text. The new wording is below and not much
>> different than the text in the current draft. Barring any solid objections
>> to this in the next week or so, I'll publish -08 at which point I believe
>> the document will be ready for WGLC.
>>
>> actor_token
>>
>> OPTIONAL.  A security token that represents the identity of the acting
>> party. Typically this will be the party that is authorized to use the
>> requested security token and act on behalf of the subject.
>>
>>
>>
>> On Thu, May 11, 2017 at 9:58 AM, Brian Campbell <
>> bcampbell@pingidentity.com> wrote:
>>
>>> The token exchange framework facilitates deployments like this one
>>> https://help.salesforce.com/articleView?id=remoteaccess_oaut
>>> h_asset_token_flow.htm or https://developer.box.com/docs
>>> /getting-started-with-new-box-view, for example, and I don't think pure
>>> plug and play interoperability is a realistic goal. The framework promotes
>>> interoperability in the form of common patterns and parameters that can be
>>> supported in libraries, products, and services.
>>>
>>> There's not one "other case" I have in mind but rather just broadening
>>> the text somewhat to more straightforwardly accommodate other cases.  One
>>> potential example is where the actor_token represents an authorizing party
>>> (again maybe needed for policy or auditing) to the token exchange event
>>> itself rather than the party that's having access rights assigned to it
>>> (implicitly with impersonation or explicitly with delegation).
>>>
>>>
>>>
>>> On Tue, May 9, 2017 at 9:55 AM, Denis <denis.ietf@free.fr> wrote:
>>>
>>>> Brian,
>>>>
>>>> Even if Token Exchange is a framework, the goal is to be finally able
>>>> to interoperate.
>>>>
>>>> Whether we have one or two parameters, would you be able to provide a
>>>> precise semantics for the "other case" you have in mind ?
>>>>
>>>> Denis
>>>>
>>>> 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-exchange-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
>>>>>>>>>>
>>>>>>>>>> ...
>
> [Message clipped]

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