Re: [OAUTH-WG] [External Sender] Re: Transaction Tokens issuance in the absence of incoming token

[George Fletcher <[e-mail]>]

Atul has submitted this PR to address this issue.
https://github.com/oauth-wg/oauth-transaction-tokens/pull/90

On Fri, Apr 12, 2024 at 12:10 PM Atul Tulshibagwale <[e-mail]> wrote:

> Thanks all, for your input. We discussed alternatives on a call last week
> <https://urldefense.com/v3/__https://hackmd.io/@rpc-sec-wg/BkdOgipkA__;!!FrPt2g6CO4Wadw!IaritBR30A-OIqtvw3r5q6_aqkOROPghBPV4SoaRKASDbORVwY8WPRHKgkC7kPF3SIu2uOfYw3rthSUvjiHD$>,
> and arrived at using self-signed tokens with token exchange as a way
> forward.
>
> On Fri, Apr 5, 2024 at 10:58 AM Brian Campbell <[e-mail]>
> wrote:
>
>> One potential benefit of keeping the use of Token Exchange is that some
>> AS products/implementations have built a fair amount of configurability and
>> extensibility into their Token Exchange support, which might allow for
>> existing systems to be set up to do Transaction Tokens. Whereas a new
>> endpoint or new grant type are more likely to require code changes to the
>> core AS. Obviously this isn't universally true but something to consider
>> nonetheless.
>>
>> On Fri, Apr 5, 2024 at 4:13 AM Kai Lehmann <kai.lehmann=
>> [e-mail]> wrote:
>>
>>> Hi,
>>>
>>>
>>>
>>> that is my thought as well. It does not necessarily be a Token Exchange
>>> profile, but the Token endpoint makes sense as Tokens are issued. Defining
>>> a specific Token grant with the necessary input parameters would fit nicely.
>>>
>>>
>>>
>>> Best regards,
>>>
>>> Kai
>>>
>>>
>>>
>>> *From: *OAuth <[e-mail]> on behalf of Dmitry Telegin
>>> <dmitryt=[e-mail]>
>>> *Date: *Friday, 5. April 2024 at 00:41
>>> *To: *Atul Tulshibagwale <[e-mail]>
>>> *Cc: *oauth <[e-mail]>
>>> *Subject: *Re: [OAUTH-WG] Transaction Tokens issuance in the absence of
>>> incoming token
>>>
>>>
>>>
>>> Hello Atul,
>>>
>>>
>>>
>>> As an alternative to Token Exchange and separate (new) endpoint, have
>>> you ever considered OAuth 2.0 Extension Grants
>>> <https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/rfc6749*section-4.5__;Iw!!FrPt2g6CO4Wadw!IaritBR30A-OIqtvw3r5q6_aqkOROPghBPV4SoaRKASDbORVwY8WPRHKgkC7kPF3SIu2uOfYw3rthaF41vnj$>?
>>> This could give us more flexibility as will let us define our own set of
>>> input parameters and validation rules (opposite to Token Exchange that
>>> restricts us to subject_token and friends).
>>>
>>>
>>>
>>> Regards,
>>>
>>> Dmitry
>>>
>>>
>>>
>>> On Thu, Apr 4, 2024 at 11:02 PM Atul Tulshibagwale <[e-mail]> wrote:
>>>
>>> Thanks very much for your feedback, Joe!
>>>
>>>
>>>
>>> On Wed, Apr 3, 2024 at 10:16 AM Joseph Salowey <[e-mail]> wrote:
>>>
>>> Hi Atul,
>>>
>>>
>>>
>>> I'm just starting to review the transaction tokens draft and have only a
>>> minimal understanding of the token exchange document at this point so I'm
>>> lacking a little background, but I have a few comments and questions below.
>>>
>>>
>>>
>>> On Fri, Mar 29, 2024 at 10:39 AM Atul Tulshibagwale <[e-mail]>
>>> wrote:
>>>
>>> Hi all,
>>>
>>> We had a meeting today (notes here
>>> <https://urldefense.com/v3/__https://hackmd.io/@rpc-sec-wg/HJNXYKkk0__;!!FrPt2g6CO4Wadw!IaritBR30A-OIqtvw3r5q6_aqkOROPghBPV4SoaRKASDbORVwY8WPRHKgkC7kPF3SIu2uOfYw3rthSyWxSbV$>)
>>> in which we discussed the question of what we should do if there is no
>>> incoming (external) token in the request to issue a Transaction Token
>>> <https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-ietf-oauth-transaction-tokens/__;!!FrPt2g6CO4Wadw!IaritBR30A-OIqtvw3r5q6_aqkOROPghBPV4SoaRKASDbORVwY8WPRHKgkC7kPF3SIu2uOfYw3rthe6t5FmT$>
>>> (TraT). We identified a few circumstances under which this can happen:
>>>
>>>    - The requesting service is triggered by a non-OAuth based flow such
>>>    as email or an internal trigger
>>>    - The client of the requesting service uses means other than an
>>>    access token to authorize the call (e.g. MTLS)
>>>
>>> [Joe] I think there will be a fair number of systems that support means
>>> of authorizing non-oauth flows.
>>>
>>>
>>>
>>>
>>>
>>> We identified a few possibilities listed below. Please note that the
>>> Transaction Tokens draft assumes that the TraT Service trusts the
>>> requesting service, so all the possibilities below assume this.
>>>
>>>
>>>
>>>
>>>
>>> [Joe] yes, you are trusting another part of the system to perform some
>>> authorization and inform the token service of the result.
>>>
>>>
>>>
>>> Here are some possibilities we discussed:
>>>
>>>    1. *Request Details*: Put the subject information in the
>>>    request_details parameter of the TraT request, and the subject_token value
>>>    is set to "N_A"
>>>    2. *Self-Signed Token*: The requester generates a self-signed JWT
>>>    that has the subject information and puts that in the subject_token value
>>>
>>> [Joe] I like having signed tokens, but if this is really information
>>> just exchanged between two endpoints it may be more work than necessary.
>>>
>>>
>>>    1. *Separate Separate Endpoint*: The TraT service exposes a separate
>>>    endpoint to issue TraTs when there is no incoming token, and that endpoint
>>>    can be defined such that the request does not have a subject_token
>>>    parameter. This endpoint is not a profile of OAuth Token Exchange
>>>    2. *Separate Endpoint Only*: Extending the thought above, the
>>>    requester can always extract the content of the incoming token into the
>>>    "request_details" parameter, so why do we need the Token Exchange endpoint
>>>
>>> [Joe] What do we gain by using token exchange? While it seems that there
>>> is overlap between delegation/impersonation it seems that transaction
>>> tokens are sort of a superset and contain additional information about the
>>> context of the transaction.   If it looks like token exchange is too
>>> constraining then transaction tokens may just be a different use case.
>>> With the understanding I currently have I'd either go with 4. Separate
>>> Endpoint Only or 2. Self Signed token.  Splitting the endpoints could be
>>> valid, but it seems a bit weird for me, if we did decide to do that then
>>> probably we wouldn't need to sign the information unless the request is
>>> going to traverse multiple systems.
>>>
>>>
>>>
>>>
>>>
>>> We would like to understand how the group feels about these choices, or
>>> if you have other suggestions / thoughts on this topic.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Atul
>>>
>>>
>>>
>>> --
>>>
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>>>
>>> Atul Tulshibagwale
>>>
>>> CTO
>>>
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>>>
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