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

[Vladimir Dzhuvinov <[e-mail]>]

Hi Warren,

On 08/02/2021 17:59, Warren Parad wrote:
> None of that justified explicitly stating that refresh token
> introspection shouldn't be done. At best it suggests that we should
> explicitly add language in the draft to directly encourage it.

Did you mean discourage?

> But if an AS wants to support it, we shouldn't stop them, or suggest
> that they can't do it.

The current draft doesn't mention refresh tokens at all. Its subject is
the introspection of access tokens by authenticated resource servers and
returning the response as a signed JWT. The use of refresh tokens at the
introspection endpoint, per RFC 7662, is not forbidden by the draft.


>
>     Allowing refresh tokens to be introspected can also create a
>     conflict with the sec recommendation to rotate them
>
>
> Not following, can you explain this further?

I just double checked the rotation spec. Use that triggers rotation is
clearly specified as "access token response", so there should actually
be no issues with confusing introspection as use.

https://tools.ietf.org/html/draft-ietf-oauth-security-topics-16#section-4.13.2

RFC 7662 also seems to imply that a public client with a refresh token
should not normally be able to introspect it, because it can't
authenticate to the AS.

> https://tools.ietf.org/html/rfc7662#section-2.2
>    To prevent token scanning attacks, the endpoint MUST also require
>    some form of authorization to access this endpoint, such as client
>    authentication as described in OAuth 2.0 [RFC6749 <https://tools.ietf.org/html/rfc6749>] or a separate
>    OAuth 2.0 access token such as the bearer token described in OAuth
>    2.0 Bearer Token Usage [RFC6750 <https://tools.ietf.org/html/rfc6750>].  The methods of managing and
>    validating these authentication credentials are out of scope of this
>    specification.

Vladimir


>
> 	
>
> Warren Parad
>
> Founder, CTO
>
> Secure your user data and complete your authorization architecture.
> Implement Authress <https://authress.io>.
>
>
> On Mon, Feb 8, 2021 at 4:13 PM Vladimir Dzhuvinov
> <[e-mail] <mailto:[e-mail]>> wrote:
>
>     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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>>>
>>
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>     -- 
>     Vladimir Dzhuvinov
>
-- 
Vladimir Dzhuvinov