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

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=40pingidentity.com@dmarc.ietf.org> 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
> bjung@pingidentity.com
> w: +1 604.697.7037
> Connect with us:
>
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