I'm looking for a way to check if an existing token is still valid. Imagine a client is holding on to a token between user sessions, for example if it's making API requests for the user on a cron job. When the user returns to the site, I want to check if the token is still valid, and make them sign in again if not.
Aaron On Mon, Jul 20, 2015 at 12:11 PM John Bradley <ve7...@ve7jtb.com> wrote: > If you want the resource owner/user then get a id_token from the token > endpoint. That saves another call to a introspection endpoint. > > Sent from my iPhone > > On Jul 20, 2015, at 7:49 PM, Aaron Parecki <aa...@parecki.com> wrote: > > Okay, if the intent is for this endpoint to be used by the resource > server, this all makes sense. I was under the impression that it could also > be used by clients to verify if the token is valid. Is there some other > spec I could look at that is intended to be used by clients to verify if a > token is valid and find out the user ID associated with it? > > ---- > Aaron Parecki > aaronparecki.com > @aaronpk <http://twitter.com/aaronpk> > > > On Sun, Jul 19, 2015 at 10:01 PM, Justin Richer <jric...@mit.edu> wrote: > >> Because the target isn’t the client, it’s the protected resource. We’re >> re-using OAuth’s client credentialing mechanisms (optionally, you can use >> whatever you deem necessary), but it’s not a client that’s doing it. That’s >> why it was changed to a MUST — there may be public clients out there (which >> could also use RFC7591 to become non-public), but public resource servers >> don’t make nearly as much sense. >> >> Additionally, the discussion for this was back in December during the >> WGLC, and the time for normative changes to this particular spec is largely >> over at this stage. >> >> — Justin >> >> On Jul 20, 2015, at 12:03 AM, William Denniss <wdenn...@google.com> >> wrote: >> >> I see in earlier drafts that client authentication MUST was a SHOULD. >> >> Why not put it back to a SHOULD, and make these arguments in the Security >> Considerations? By the sound of it in some implementations there are good >> reasons for doing client authentication, but they may not apply to >> everyone, so do we need to be so prescriptive? An error response can be >> added for requests the server deems require client authentication. >> >> It wouldn't have to be an all-or-nothing policy choice either, a server >> could chose to reject requests from confidential clients where client >> authentication is not provided, but accept requests without client >> authentication from non-confidential clients. A server that has >> sufficiently high entropy in the tokens, abuse protection on the endpoint, >> and is not concerned about an unrelated party (that happens to have a token >> intended for a different party) learning the token metadata, could simply >> not require any client authentication at all. >> >> Apart from anything, it is really trivial to support non-confidential >> client usage, so why not? Perhaps there are some use-cases that will turn >> up in the future (especially since as defined the introspection response is >> extensible). One I can think of now is debugging: it's useful during >> development to be able to inspect the tokens you get back from the AS. >> >> Best, >> William >> >> >> On Sun, Jul 19, 2015 at 9:14 PM, Justin Richer <jric...@mit.edu> wrote: >> >>> In the case of a “public client” using a token, the authorization is the >>> token that the resource server uses to call the introspection endpoint, >>> along side the token that it is introspecting. This is exactly how the UMA >>> protocol works: the resource server has a “Protection API Token” that it >>> uses to call several endpoints at the AS, including the introspection >>> endpoint. In UMA, this PAT is given to the resource server through a normal >>> OAuth transaction with an end user who facilitates the RS->AS introduction. >>> >>> And I think this is all actually a moot point because *clients* >>> shouldn’t be doing the introspection in the first place — the whole spec is >>> there to support *resource servers* introspecting at the auth server. >>> So you probably don’t have “public client resource servers” out there. We >>> simply re-used OAuth’s existing client authentication mechanism, that >>> doesn’t make them clients. This decision is based on development and >>> deployment experience (as in, several people independently built it exactly >>> this way). Do you have a use case where you’ve got a protected resource >>> that can’t hold credentials (either a client secret or a public/private >>> keypair) to authenticate with, and can’t be introduced using OAuth to the >>> AS as in UMA? >>> >>> To your other point: An attacker has less of a chance of getting >>> information about a token by fishing at a protected resource with tokens, >>> since they’re not being returned information about the token other than the >>> fact that the token worked. (Or at least it seemed to work because a result >>> came back — you could easily give a suspected attacker >>> valid-looking-but-fake data as one mitigation mechanism.) The introspection >>> response can give you information about where else the token could be used, >>> potentially. Additionally, the RS really ought to be preventing >>> data-fishing attacks like this just for its own sake anyway. There are lots >>> of techniques for doing this, but they tend to be specific to the kind of >>> API that’s being served. >>> >>> Requiring the resource server to authenticate with the authorization >>> server also allows you to do a few other useful things. Our implementation, >>> for example, limits the token information that is returned to a particular >>> AS. This allows us to have tokens that can be used in multiple RS’s without >>> those RS’s ever even knowing the token is powerful enough to be used >>> elsewhere. It prevents information about the authorization from leaking to >>> parties who have no business knowing. >>> >>> Hope this helps clarify it, >>> — Justin >>> >>> On Jul 19, 2015, at 7:59 PM, Aaron Parecki <aa...@parecki.com> wrote: >>> >>> How are public clients supposed to authenticate if there is no secret? >>> >>> Isn't "fishing for valid tokens" just as much of an issue at the >>> resource server? I don't see how having the introspection endpoint require >>> client authentication actually solves the fishing problem since attackers >>> could just fish against the resource server. In fact, if the resource >>> server queries the introspection endpoint to check if tokens are valid, >>> then that effectively gives an attacker a way to fish for tokens using the >>> resource server's credentials. >>> >>> --- >>> Aaron Parecki >>> http://aaronparecki.com >>> >>> On Sat, Jul 18, 2015 at 10:04 PM Justin Richer <jric...@mit.edu> wrote: >>> >>>> Public clients can use the token-based auth mechanism, can’t they? If >>>> you don’t have some form of authentication on the introspection endpoint, >>>> you end up with a way for people to anonymously and programmatically fish >>>> for valid token values. >>>> >>>> — Justin >>>> >>>> On Jul 19, 2015, at 6:30 AM, Aaron Parecki <aa...@parecki.com> wrote: >>>> >>>> The introspection draft states that the introspection endpoint MUST >>>> require authentication of clients. It mentions either client authentication >>>> (id+secret) or a separate bearer token. >>>> >>>> How are public clients expected to use the token introspection >>>> endpoint? I didn't see a note in the document about that at all. >>>> >>>> ---- >>>> Aaron Parecki >>>> aaronparecki.com >>>> @aaronpk <http://twitter.com/aaronpk> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>> >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org >>> https://www.ietf.org/mailman/listinfo/oauth >>> >>> >> >> > _______________________________________________ > OAuth mailing list > OAuth@ietf.org > https://www.ietf.org/mailman/listinfo/oauth > >
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