Thank you, Waren, Sorry that was misleading, I meant literally the 'null' as a string which may be because of a bug in the client. That was an example taken from Thomas Broyer letter: > For months, my AS received requests with token=Array, and now receives requests with token=null. Those are clearly bugs in the client code, and because I return a 200 OK, the developers aren't aware of it.
If you are interested here is the entire thread: https://mailarchive.ietf.org/arch/msg/oauth/w68pbTcp2jjk4tzldnS0gOS127Q/ In an ideal world the AS may store even revoked tokens (or JWT kid) and clearly return some error in case of unknown token. At least for a day, for example. But at least it on a spec level there must be few words added into "Security Considerations" section On Wed, 26 Jan 2022 at 20:13, Warren Parad <wpa...@rhosys.ch> wrote: > According to RFC7009, I don't see anywhere which says you have to return a > 200 for token=null. I interpret it as you return a 200, if the token passed > would never have been accepted as a valid token. *Null* isn't an invalid > token, it is an invalid value for the *token* parameter which is required. > > token REQUIRED. The token that the client wants to get revoked. > > > So the correct response is either an error immediately (returning a 4XX), > or feel free to return the 200 and then the AS should redirect the user to > a verified location with the *error *and *error_description* query > parameters. > > I do see some gray area for what to do with real invalid tokens, i.e. the > token signature is invalid. So some clarity on the definition of *invalid. > *Since the spec talks about invalidation lots of times we should > interpret it to mean *a token that has already been invalidated.* And I > would interpret all other tokens as justifications for returning a 4XX > status code. > > Warren Parad > > Founder, CTO > Secure your user data with IAM authorization as a service. Implement > Authress <https://authress.io/>. > > > On Wed, Jan 26, 2022 at 6:44 PM Sergey Ponomarev <stok...@gmail.com> > wrote: > >> Hi and sorry for raising the four years old topic. >> >> As a recup I reported a SECURITY VULNERABILITY on OAuth 2 >> specification level. It's minor (I hope) but still seen in the real >> world AS implementation. >> In short, to logout a user the revocation endpoint is called with the >> user's token. And by a the RFC7009 the AS must always return 200 Ok >> status code even if the token is invalid: >> >> > The authorization server responds with HTTP status code 200 if the >> token has been revoked successfully or if the client submitted an invalid >> token. >> > Note: invalid tokens do not cause an error response since the client >> cannot handle such an error in a reasonable way. Moreover, the purpose of >> the revocation request, invalidating the particular token, is already >> achieved. >> >> So if a client just made an incorrect call e.g. token=null then it >> will anyway receive a 200 OK and the user will think that logout was >> successful and a session closed. But internally the token may be >> stored in many places and even shared between microservices/UI and >> other parties and it will remain still working. >> >> Can anybody take some actions and at least make some errata to the spec? >> >> P.S. adding to CC authors of the spec >> >> On Tue, 22 May 2018 at 20:29, Sergey Ponomarev <stok...@gmail.com> wrote: >> > >> > What is also should be discussed and specified is revoking of expired >> token. For example in Keycloak you can invalidate a session by expired >> token: >> >> >> >> It should be possible to logout a session with a token that is >> expired. This is to make sure that a user can invalidate a session if >> there's a suspicion that the refresh/offline token has been leaked. In such >> a case it could be that the real user has an expired refresh token while an >> attacker has been able to refresh the token and obtain a new not expired >> refresh token. >> > >> > >> > KEYCLOAK-3302 >> > >> > Think this is doubtful but makes sense. >> > >> > To summarize: we have to create some threat model with description of >> possible use cases. >> > >> > >> > On Tue, 22 May 2018 at 18:18, Sergey Ponomarev <stok...@gmail.com> >> wrote: >> >> >> >> From OAuth perspective we can't say that the token should have some >> structure: they can be any random value in case of reference (opaque) >> tokens. But the Google's OAuth Server responds in this case with 400 error >> "invalid_token". >> >> The same can be used for JWTs with invalid sign or issuer. >> >> So it would be better if specification allow OAuth servers to respond >> with this error code if it clearly know that token was invalid by format. >> >> >> >> On Tue, 22 May 2018 at 17:51, Thomas Broyer <t.bro...@gmail.com> >> wrote: >> >>> >> >>> IFF the server processes it! >> >>> RFC 7009 says “An authorization server MAY ignore this parameter, >> particularly if it is able to detect the token type automatically.” which >> BTW is exactly my case. >> >>> >> >>> For months, my AS received requests with token=Array, and now >> receives requests with token=null. Those are clearly bugs in the client >> code, and because I return a 200 OK, the developers aren't aware of it. >> >>> >> >>> If tokens have an expected "structure", I think AS should probably >> return an error when the token value clearly is not a token (at one point I >> may change my implementation to do just that). As soon as it looks like a >> potential token though, then 200 OK sounds good to me. >> >>> >> >>> On Tue, May 22, 2018 at 4:34 PM Justin Richer <jric...@mit.edu> >> wrote: >> >>>> >> >>>> In that specific case, the token_type_hint value is invalid and can >> be rejected as an invalid_request. >> >>>> >> >>>> — Justin >> >>>> >> >>>> >> >>>> On May 22, 2018, at 5:27 AM, Joseph Heenan <jos...@authlete.com> >> wrote: >> >>>> >> >>>> >> >>>> I think one important point Sergey raised was that the response to >> the client from submitting the wrong token is the same 200 response as >> submitting a valid token, and that hugely increases the chance that the >> developer of the client app might submit the wrong token and never realise. >> Making it easier for the developer of the client app to see that they've >> done something wrong and need to fix their implementation seems like a >> worthwhile goal to me, and that would appear to explain what google are >> thinking with their responses. >> >>>> >> >>>> An example of an easy to make error that would get a 200 response is >> getting the values the wrong way around, i.e. a body of: >> >>>> >> >>>> token=refresh_token&token_type_hint=45ghiukldjahdnhzdauz >> >>>> >> >>>> (as token_type_hint may be ignored by the server.) >> >>>> >> >>>> The example Sergey gave of the developer accidentally sending the id >> token instead of the intended token seems quite likely to happen in the >> real world too, and a 200 response in that case does seem wrong to me. >> >>>> >> >>>> >> >>>> Joseph >> >>>> >> >>>> >> >>>> On 21 May 2018, at 22:29, Justin Richer <jric...@mit.edu> wrote: >> >>>> >> >>>> I’m with George here: revocation is almost a best-effort request >> from the client’s perspective. It sends a message to the server saying “hey >> I’m done with this token, you can throw it out too”. If the server does >> revoke the token, the client throws it out. If the server doesn’t revoke >> the token? Then the client still throws it out. Either way the results from >> the client’s perspective are the same: it’s already decided that it’s done >> with the token before it talks to the server. It’s an optional cleanup step >> in most OAuth systems. >> >>>> >> >>>> — Justin >> >>>> >> >>>> On May 21, 2018, at 5:08 PM, George Fletcher <gffletch= >> 40aol....@dmarc.ietf.org> wrote: >> >>>> >> >>>> I'm not understanding how these different cases matter to the >> client? I doubt that the running code will be able to dynamically handle >> the error. So it seems this information is only relevant to the developers >> and not relevant from an end user and the client perspective. >> >>>> >> >>>> Also, for the 5 states you define, the effect of calling revocation >> is still that the token is "revoked" because the token is already not valid. >> >>>> >> >>>> So from an implementation perspective, where is the concern that >> developer will do the "wrong thing" without these more detailed error >> responses? >> >>>> >> >>>> Thanks, >> >>>> George >> >>>> >> >>>> On 5/19/18 5:41 PM, Sergey Ponomarev wrote: >> >>>> >> >>>> Hi, >> >>>> >> >>>> I developing an implementation of back channel token revocation >> endpoint. And I think we should reconsider and probably change the >> specification to improve error handling. >> >>>> >> >>>> Here we see several situations of error state: >> >>>> 1. token wasn't sent in request. >> >>>> 2. token is invalid by format i.e. not JWT or JWT with invalid >> signature >> >>>> 3. token is expired or token is even unknown >> >>>> 4. token was already revoked >> >>>> 5. token type is unsupported >> >>>> >> >>>> According to RFC7009 OAuth 2.0 Token Revocation section 2.2 >> Revocation Response: >> >>>> >> >>>>> The authorization server responds with HTTP status code 200 if the >> token has been revoked successfully or if the client submitted an invalid >> token. >> >>>>> Note: invalid tokens do not cause an error response since the >> client cannot handle such an error in a reasonable way. Moreover, the >> purpose of the revocation request, invalidating the particular token, is >> already achieved.. >> >>>> >> >>>> >> >>>> As you may see this section covers only case 3 and case 4 but it's >> very unclear: calling token as "invalid" is very broad definition. >> >>>> I think we should take a look on each case separately: >> >>>> >> >>>> 1. token wasn't sent in request. >> >>>> Most implementations returns 400 status code, error: >> "invalid_request", error_description": "Missing required parameter: token". >> >>>> Note that returned error is not "invalid_token" but >> "invalid_request" and I think this should be correct behavior and should be >> clearly specified. >> >>>> >> >>>> 2. token is invalid by format i.e. not JWT or JWT with invalid >> signature >> >>>> This error is mostly related to JWT but for reference (opaque) >> tokens can be also applied (e.g. token is too long). >> >>>> Goolge OAuth returns 400 code with "error": "invalid_token" and I >> think this is correct behavior. >> >>>> The client can have a bug and sends invalid tokens so we should >> return an error response instead of 200 status. >> >>>> >> >>>> 3. token is expired or even unknown >> >>>> Spec says that IdP should return 200 in this case but in case of >> unknown token this may be a symptom of a bug on client side. Even if IdP >> can clearly determine that token is expired (in case of JWT) this is hard >> to determine in case of reference token that was removed from DB. >> >>>> So personally I think that from security perspective it's better to >> response with 400 status because client can have a bug when it's sends some >> unknown token and think that it was revoked while it wasn't. >> >>>> >> >>>> For example Google OAuth revocation endpoint implementation do not >> follow the spec and returns 400 Bad Request with error message "Token is >> revoked or expired". >> >>>> >> >>>> 4. token was already revoked >> >>>> The same as above: this can be a bug in a client and we should >> return 400 status. In case of reference token which was removed from DB we >> can't distinguish that the token was revoked or even existed so this >> situation is the same as unknown token. >> >>>> >> >>>> 5. token type is unsupported >> >>>> For this case specification introduces a new error code for case 5 >> in section 2.2.1. Error Response : >> >>>>> >> >>>>> unsupported_token_type: The authorization server does not support >> the revocation of the presented token type. That is, the client tried to >> revoke an access token on a server not supporting this feature. >> >>>> >> >>>> But it would be better to mention that revocation of ID token (which >> can be is considered as "public" and not used to auth) definitely should >> cause this error. >> >>>> >> >>>> It would be great if we discuss this cases and improve specification. >> >>>> >> >>>> P.S. Also it may be worse to mention that specification says that >> content of successful response is empty but status code is 200 instead of >> 201 "No Content". >> >>>> >> >>>> Regards, >> >>>> Sergey Ponomarev >> >>>> >> >>>> >> >>>> _______________________________________________ >> >>>> 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 >> >>>> >> >>>> >> >>>> _______________________________________________ >> >>>> 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 >> >> >> >> >> >> >> >> -- >> >> Sergey Ponomarev, skype:stokito >> > >> > >> > >> > -- >> > Sergey Ponomarev, skype:stokito >> >> >> >> -- >> Sergey Ponomarev, >> stokito.com >> >> _______________________________________________ >> OAuth mailing list >> OAuth@ietf.org >> https://www.ietf.org/mailman/listinfo/oauth >> > -- Sergey Ponomarev <https://linkedin.com/in/stokito>, stokito.com
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