Invalid OAuth token handling

[Zoë]

I'm writing directly against the v2 HTTP API and while testing our login and error handling, I found some unexpected results.  If I take a valid OAuth token and corrupt it (change the first character, for example), or just give it a garbage string (say, "abc") the response is either 500 Internal Server Error or 400 "The given OAuth2 access token is malformed".  I'm seeing it in both user authentication APIs (/files/list_folder) using OAuth2 credentials and in /auth/token/from_oauth1 if I corrupt the OAuth1 credentials.  While I suppose they are invalid inputs, I would have expected a 401 Authentication error for either case to tell me that I need to reauthenticate the user.

[Greg-DB]

Thanks for the report! The 500 response to an invalid access token would just be a bug on our side. We'll look into it

The 400 is expected if the supplied string doesn't match the expected pattern for an access token, for example when supplying "abc" as mentioned. You can check the response body for an error message:

Error in call to API function "users/get_current_account": The given OAuth 2 access token is malformed.

You will get a 401 on further calls for a revoked token, for example, if it was a real token revoked via /2/auth/token/revoke:

{"error_summary": "invalid_access_token/...", "error": {".tag": "invalid_access_token"}}

[Zoë]

Yes, the 400 response does say that the OAuth2 access token is malformed, but that only helps if someone looks at a log.  In code I can detect 401 errors or from_oauth1's 409 "invalid_oauth1_token_info" error, clear the access token, and automatically ask the user to re-authenticate, but if it's just a generic 400 there's no way for me to do that.  

[Greg-DB · Accepted solution]

Thanks for the feedback! The 400 error here with the plain text error message is more meant for the developer during development of the app. Generally, your app should be written such that a malformed access token like that wouldn't be able to make it into your released app, but you can catch the 400 and display the error to the user if you want.