Just use the token at your target API and see if it works. Your client’s going to need to be able to get a new token if this one expires mid-session anyway, so you’re not saving anything by doing an introspection request.
— Justin > On Jul 20, 2015, at 9:34 PM, Aaron Parecki <aa...@parecki.com> wrote: > > 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 > <mailto: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 > <mailto: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 <http://aaronparecki.com/> >> @aaronpk <http://twitter.com/aaronpk> >> >> >> On Sun, Jul 19, 2015 at 10:01 PM, Justin Richer <jric...@mit.edu >> <mailto: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 >>> <mailto: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 >>> <mailto: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 >>>> <mailto: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 <http://aaronparecki.com/> >>>> >>>> On Sat, Jul 18, 2015 at 10:04 PM Justin Richer <jric...@mit.edu >>>> <mailto: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 >>>>> <mailto: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 <http://aaronparecki.com/> >>>>> @aaronpk <http://twitter.com/aaronpk> >>>>> >>>>> _______________________________________________ >>>>> OAuth mailing list >>>>> OAuth@ietf.org <mailto:OAuth@ietf.org> >>>>> https://www.ietf.org/mailman/listinfo/oauth >>>>> <https://www.ietf.org/mailman/listinfo/oauth> >>>> >>> >>> >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org <mailto:OAuth@ietf.org> >>> https://www.ietf.org/mailman/listinfo/oauth >>> <https://www.ietf.org/mailman/listinfo/oauth> >>> >>> >> >> >> _______________________________________________ >> OAuth mailing list >> OAuth@ietf.org <mailto:OAuth@ietf.org> >> https://www.ietf.org/mailman/listinfo/oauth >> <https://www.ietf.org/mailman/listinfo/oauth>
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