Re: [OAUTH-WG] OAuth 2.0 Token Introspection in RFC7662 : Refresh token?

[Bill Jung <[e-mail]>]

Yep, I agree. But that's just me agreeing with it. Unless the spec clearly
says it everybody will throw different ideas and use cases. That's why I
want the spec to clarify this.

On Wed, Mar 4, 2020, 1:42 PM Justin Richer, <[e-mail]> wrote:

> Why would the client need to know the refresh token’s expiry? Can’t they
> just use the refresh token and see? Either way it’s a single round trip to
> the AS and the client gets the same answer with the same recovery code path.
>
>  — Justin
>
> On Mar 4, 2020, at 2:01 PM, Bill Jung <
> bjung=[e-mail]> wrote:
>
> The question started when some RPs (client apps) asked that AS allow
> introspection endpoint to RPs so that RPs can check their refresh
> token's expiry. If AS allows this, which the spec is not clear about, then
> AS needs to know if the request is coming from RP or RS so that AS can
> allow the Access Token introspection to RS only. But then is that the right
> thing to do even?
>
> Surely some clarification will eliminate the time spent on unnecessary
> discussion among developers.
>
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> Bill Jung
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> On Sun, Mar 1, 2020 at 9:33 PM David Waite <david=
> [e-mail]> wrote:
>
>> On Mar 1, 2020, at 10:11 PM, Andrii Deinega <[e-mail]>
>> wrote:
>> >
>> > How would the authorization server know who actually uses the
>> > introspection endpoint assuming that a protected resource and a client
>> > application use the same credentials (client_id and client_secret)?
>>
>> In the external context, you have a client accessing a protected resource
>> with an access token. The client should treat the token as opaque, and
>> RFC7662 makes no allowances for that client to introspect its tokens.
>>
>> If you control both the client and protected resource, you may decide to
>> short-cut and have them share credentials. However, the client logic still
>> should never be introspecting the tokens.
>>
>> The security considerations also say that you must prove the
>> authentication of the protected resource, which I have interpreted to mean
>> that access tokens used to authorize the call to the introspection endpoint
>> must be issued to a confidential client - public clients cannot protect
>> credentials to perform an authentication. You want to limit introspection
>> to prevent denial of service and probing attacks, and to limit the amount
>> of information on viable attacks conveyed if someone steals a token.
>>
>> -DW
>>
>> >
>> > Regards,
>> > Andrii
>> >
>> > On Sun, Mar 1, 2020 at 7:38 PM David Waite <
>> [e-mail]> wrote:
>> >>
>> >> I would expect the AS to invalidate the refresh token in this case,
>> which would not require a refresh token mode nor necessarily any signaling
>> back to the resource.
>> >>
>> >> -DW
>> >>
>> >>> On Mar 1, 2020, at 12:12 AM, Andrii Deinega <[e-mail]>
>> wrote:
>> >>>
>> >>> Hello Bill,
>> >>>
>> >>> I'm just thinking out loud about possible scenarios for a protected
>> >>> resource here... It may decide to revoke a refresh token if a client
>> >>> application tried to use it instead of an access token when the
>> >>> protected resource is paranoid about security. In order to do that an
>> >>> introspection response should include a non-standard parameter which
>> >>> indicates that the requested token is refresh_token.
>> >>>
>> >>> A user of the introspection endpoint should rely only on a value of
>> >>> the active parameter (which is a boolean indicator) of the endpoint
>> >>> response. This applies to both types of tokens. Note, the expiration
>> >>> date, as well as other parameters, are defined as optional in the
>> >>> specification. Both token types can be revoked before the expiration
>> >>> date comes even if this parameter is presented as part of the
>> >>> response. In my opinion, there are a number of reasons why this check
>> >>> (for a refresh token) can be useful on the client application side.
>> >>>
>> >>> --
>> >>> Regards,
>> >>> Andrii
>> >>>
>> >>>
>> >>> On Fri, Feb 28, 2020 at 1:59 AM Bill Jung
>> >>> <bjung=[e-mail]> wrote:
>> >>>>
>> >>>> Hello, hopefully I am using the right email address.
>> >>>>
>> >>>> Simply put, can this spec be enhanced to clarify "Who can use the
>> introspection endpoint for a refresh token? A resource provider or a client
>> app or both?"
>> >>>>
>> >>>> RFC7662 clearly mentions that the user of introspection endpoint is
>> a 'protected resource' and that makes sense for an access token. If we
>> allow this to client apps, it'll give unnecessary token information to them.
>> >>>> However, the spec also mentions that refresh tokens can also be used
>> against the endpoint.
>> >>>> In case of refresh tokens, user of the endpoint should be a client
>> app because refresh tokens are used by clients to get another access token.
>> (Cannot imagine how/why a resource server would introspect a refresh token)
>> >>>>
>> >>>> Is it correct to assume that the endpoint should be allowed to
>> client apps if they want to examine refresh token's expiry time? Then the
>> RFC should clearly mention it.
>> >>>>
>> >>>> Thanks in advance.
>> >>>>
>> >>>> <Details from the spec>
>> >>>> In https://tools.ietf.org/html/rfc7662
>> >>>> In '1.  Introduction' section says,
>> >>>> "This specification defines a protocol that allows authorized
>> >>>> protected resources to query the authorization server to determine
>> >>>> the set of metadata for a given token that was presented to them by
>> >>>> an OAuth 2.0 client."
>> >>>> Above makes clear that user of the endpoint is a "protected
>> resource".
>> >>>>
>> >>>> And under 'token' in '2.1.  Introspection Request' section says,
>> >>>> "For refresh tokens,
>> >>>> this is the "refresh_token" value returned from the token endpoint
>> >>>> as defined in OAuth 2.0 [RFC6749], Section 5.1."
>> >>>> So looks like a refresh token is allowed for this endpoint..
>> >>>>
>> >>>>
>> >>>> Bill Jung
>> >>>> Manager, Response Engineering
>> >>>> [e-mail]
>> >>>> w: +1 604.697.7037
>> >>>> Connect with us:
>> >>>>
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