Oauthlib: Invalid HTTP statuses on error response

The spec mention that 401 may be used with invalid client errors and must be used when the authentication was done via the authorization header field. Although oauthlib currently does nothing to suggest that the 'WWW-Authenticate' header field should be included in the response as the spec require. I reckon keeping 401 for this error is ok but we should add a header suggestion to the exception.

Regarding the other the spec does not explicitly say that 401 may be used and thus we should probably consider changing to 400. However it does seem more appropriate with a 401 in both invalid grant and especially unauthorized client errors.

@asteinlein, @lepture, @masci thoughts?

@ib-lundgren Hi - just stumbled into this very issue and would like to chime in. From reading the spec and looking around other answers, IMO a 400 is the correct response.

Firstly, the spec:

The authorization server responds with an HTTP 400 (Bad Request)
status code (unless specified otherwise) and includes the following
parameters with the response:

There's no MUST in the 400 requirements, but there's no MAY either.

Secondly, and the reason I stumbled into this was through a bug of sorts in the sun JDK on my client (see here: http://stackoverflow.com/a/7524681/1137254 )

Essentially, my client's HTTP stack would close the connection early for a 401, but the OAuth stack above (google-http-oauth-client) would attempt to continue reading and parse the results. I think this was written into OpenJDK per the definition and expectations around a 401 (UPDATE: it's actually to do with 'streaming' mode). IMO OpenJDK is wrong too and I think I'd hit this same issue if I were to get an "invalid_client" 401 during /token endpoint requests.

Adding another vote for 400 being the correct error code here. We used to use django-oauth2-provider for oauth2 authentication from mobile apps, and it returned 400 in this case. When switching to django-oauth-toolkit (which uses oauthlib) in order to upgrade to newer Django versions, we had to hack the token request view to return a 400 instead to keep the mobile apps working correctly.

Here's one of the authors of the spec specifically stating that a 400 is the intended response for invalid authentication credentials when requesting a token, and why: https://www.ietf.org/mail-archive/web/oauth/current/msg02127.html

And here's another example of a project that's having trouble coping with oauthlib using a 401 in these circumstances.

+1 for 400

Vote for 400

I'm reviving this old thread & start a PR with the changes suggested above.

Before making progress on this, I'd like to summarize the discussion which happen in the past.

• OAuth2.0 RFC6749 working group decided to adopt 400 for error HTTP status instead of 401, cuz it requires WWW-Authenticate to be set, and it's not always possible in all errors responses.
• @asteinlein proposed a PR at https://github.com/oauthlib/oauthlib/pull/247 to change oauthlib's errors from 400 to 401, because _some clients seem to expect 401 for API calls related to authorization_. While it had to be true, we don't know which clients were broken.
• Several bugs popup in 3rd parties librairies https://github.com/oauthjs/angular-oauth2/issues/31 https://github.com/oauthjs/angular-oauth2/issues/32#issuecomment-88888755 https://github.com/oauthjs/angular-oauth2/issues/36 . Issues are all closed now.
• The overall consensus of the current thread, and also RFC6749#5.2, is that all 401 in oauthlib must be 400. However, we have two cases with 401:

1. invalid_client, where it MUST be 401 if HTTP authentication is used, else it MAY be 401.
2. invalid_token, where it SHOULD be 401.

In any cases, if 401 is used, WWW-Authenticate MUST be set (RFC2616).

Other OAuth2.0 implementations

A quick overview of the most common OAuth2.0 implementations are similar to the overall consensus:

• Google returns 400 so-question / so-question.
• Salesforce returns 400 salesforce-forum.
• Azur returns 401 with WWW-Authenticate azur-docs.
• AWS returns 400 aws-cognito-docs. They broke the "MUST" of the RFC to be 401 when HTTP authentication is used.

Conlusion

We have to align with the RFC, however to not break any implementations, we must not include these changes in 2.x.x version, but wait until 3.x.x

Please, feel free to chim in.

I cannot remember the reason/the client(s) that made me push PR #247, but I see and understand the reasons for reverting this. Thanks for the awesome research @JonathanHuot, and doing this in 3.x sounds like the best approach.

Fixed in #561 / oauthlib>= 3.0.0

according to this RFC that mentioned above invalid client also should return status 400 but in package still is 401

Hi @esfandiaryfard, could you point the exact text of the RFC ? Thanks!