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

Thanks very much for your feedback, Joe!

On Wed, Apr 3, 2024 at 10:16 AM Joseph Salowey <joe@salowey.net> 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 <atul@sgnl.ai> wrote:
>
>> Hi all,
>> We had a meeting today (notes here
>> <https://hackmd.io/@rpc-sec-wg/HJNXYKkk0>) 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://datatracker.ietf.org/doc/draft-ietf-oauth-transaction-tokens/>
>> (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
>>
>> --
>>
>> <https://sgnl.ai>
>>
>> Atul Tulshibagwale
>>
>> CTO
>>
>> <https://linkedin.com/in/tulshi> <https://twitter.com/zirotrust>
>> <atul@sgnl.ai>
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>