Re: [OAUTH-WG] JWT Response for OAuth Token Introspection and types of tokens

[Vladimir Dzhuvinov <[e-mail]>]

At first it may appear that allowing refresh tokens at the introspection
endpoint may be a logical thing to do, but in practice there are issues
with that and from an OAuth 2.x perspective it's not easy to justify.

If the point is to let clients check what authorization they have been
given OAuth 2.0 already provides a std way to do that - in the access
token response - the "scope" parameter:

https://tools.ietf.org/html/rfc6749#section-5.1

RAR has a similar parameter:

https://tools.ietf.org/html/draft-ietf-oauth-rar-03#section-3.4.1

If the point is to find if a refresh token is still valid - this can be
found out by simply using it. Allowing refresh tokens to be introspected
can also create a conflict with the sec recommendation to rotate them.
So thus it may be a better idea to not let clients assume too much about
them.

https://tools.ietf.org/html/draft-ietf-oauth-security-topics-16#section-2.2.2

If the AS is going to expose refresh token data to a client it will also
have to make a careful judgement what data it exposes.

https://tools.ietf.org/html/rfc7662#section-2.2

For instance "sub". OAuth 2.x in the relation between AS and client
actually has no concept or definition of subject / end-user identifier.
And this is done for a good reason, because it's not a user
authentication protocol. OIDC was designed for that. And to prevent
tracking of users and other privacy issues OIDC also specifies pairwise
subject IDs. The plain OAuth 2.x world doesn't have this.

Vladimir

On 08/02/2021 11:07, Warren Parad wrote:
> It doesn't work that way. You suggested to add language to the draft,
> that means the burden of proof is on you to justify adding it.
>
> Otherwise I could just say why not?
>
> And I can go stronger, what's the purpose of nho introspection
> endpoint at all, and why encourage sending access tokens to the AS?
>
> Even if you can justify access tokens, there currently isn't evidence
> provided why we should explicity discourage.
>
>
> On Mon, Feb 8, 2021, 03:18 Torsten Lodderstedt
> <[e-mail] <mailto:[e-mail]>> wrote:
>
>
>
>>     Am 08.02.2021 um 00:56 schrieb Warren Parad <[e-mail]
>>     <mailto:[e-mail]>>:
>>
>>     
>>
>>         I‘m therefore leaning towards explicitly stating in our draft
>>         that it is not intended to be used with refresh tokens.
>>
>>     I'm not following, why explicitly state that it isn't intended.
>>     If an AS wants to provide a similar JSON response to a query with
>>     the refresh token, why not encourage that?
>
>     Why should we encourage it? 
>
>>
>>     	
>>
>>     Warren Parad
>>
>>     Founder, CTO
>>
>>     Secure your user data and complete your authorization
>>     architecture. Implement Authress
>>     <https://www.google.com/url?q=https://authress.io&source=gmail-imap&ust=1613346997000000&usg=AOvVaw267Z448csTGn3F6REIQ9pT>.
>>
>>
>>     On Sun, Feb 7, 2021 at 10:58 PM Torsten Lodderstedt
>>     <torsten=[e-mail]
>>     <mailto:[e-mail]>> wrote:
>>
>>         Hi Andrii,
>>
>>>         Am 07.02.2021 um 21:30 schrieb Andrii Deinega
>>>         <[e-mail] <mailto:[e-mail]>>:
>>>
>>>         
>>>         Hi Torsten,
>>>
>>>         thank you for your response.
>>>
>>>         My use case is pretty straight forward
>>>
>>>         An OAuth client queries the AS to determine the active state
>>>         of an access token and gets the introspection response which
>>>         indicates that this access token is active (using RFC7662).
>>>
>>>         An OAuth client queries the AS to determine the active state
>>>         of a refresh token and gets the introspection response which
>>>         indicates that this refresh token is active (using RFC7662).
>>>
>>>         An OAuth client queries the AS to determine the active state
>>>         of an access token and gets the introspection response (JWT)
>>>         which indicates that this access token is active (using this
>>>         draft).
>>>
>>>         Now, an OAuth client queries the AS to determine the active
>>>         state of a refresh token (using this draft)... How will the
>>>         introspection response look like assuming that the client
>>>         provides the valid refresh token and technically, nothing
>>>         stops it from doing so.
>>
>>         why should the state be provided as JWT?I think the plain
>>         JSON response is sufficient in that case.  I also think using
>>         token introspection for checking the state of a token from
>>         the client side has limited utility. The definitive decision
>>         is always made when the client tries to access a resource. 
>>
>>         I‘m therefore leaning towards explicitly stating in our draft
>>         that it is not intended to be used with refresh tokens.
>>
>>         best regards,
>>         Torsten.
>>
>>>
>>>         Regards,
>>>         Andrii
>>>
>>>
>>>         On Sun, Feb 7, 2021 at 4:14 AM Torsten Lodderstedt
>>>         <[e-mail] <mailto:[e-mail]>>
>>>         wrote:
>>>
>>>             Hi Andrii,
>>>
>>>             thanks for your post.
>>>
>>>             The draft is intended to provide AS and RS with a
>>>             solution to exchange signed (and optionally encrypted)
>>>             token introspection responses in order to provide
>>>             stronger assurance among those parties. This is
>>>             important in use cases where the RS acts upon the
>>>             introspection response data and wants the AS to take
>>>             liability re the data quality.
>>>
>>>             I’m not sure whether there are similar use cases if a
>>>             client introspects a refresh token. What is your use case?
>>>
>>>             best regards,
>>>             Torsten. 
>>>
>>>             > Am 07.02.2021 um 08:41 schrieb Andrii Deinega
>>>             <[e-mail]
>>>             <mailto:[e-mail]>>:
>>>             >
>>>             > Hi WG,
>>>             >
>>>             > draft-ietf-oauth-jwt-introspection-response-10 states
>>>             that "OAuth 2.0 Token Introspection [RFC7662] specifies
>>>             a method for a protected resource to query an OAuth 2.0
>>>             authorization server to determine the state of an access
>>>             token and obtain data associated with the access token."
>>>             which is true. Although, according to RFC7662, the
>>>             introspection endpoint allows to introspect a refresh
>>>             token as well. Hence, the question I have is how will a
>>>             token introspection response look like when the caller
>>>             provides a refresh token and sets the "Accept" HTTP
>>>             header to "application/token-introspection+jwt"?
>>>             >
>>>             > I expect there will be no differences, right?
>>>             >
>>>             > If so, I suggest to
>>>             >       • replace "a resource server" by "the caller" in
>>>             section 4 (Requesting a JWT Response)
>>>             >       • change "If the access token is invalid,
>>>             expired, revoked" by "If a given token is invalid,
>>>             expired, revoked" in section 5 (JWT Response)
>>>             > If not, my suggestion would be to clarify what the AS
>>>             should do when it asked to introspect the refresh token
>>>             in general and additionally, what should happen in the
>>>             same case based on the type of the caller from the AS's
>>>             point of view.
>>>             >
>>>             > Regards,
>>>             > Andrii
>>>             >
>>>
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-- 
Vladimir Dzhuvinov