My app is architected as follows: I have a web service (running on GAE, not very relevant to this question) and the data that this service contains is made available through a website and through mobile and desktop apps.
Currently, the user authenticates to the website via Google ClientLogin and the apps authenticate/get authorized via GAE's built-in oauth provider. (OAuth is being used here mostly for authentication, my app doesn't actually use any external data via OAuth other than the user's unique ID and email address.)
What I'd like to do is expand the number of services that users can use to login. Because of the complicating factor of the apps, it seems I need OAuth. But I can't really properly conceptualize how this flow should go.
Lets take Facebook as an example. When a mobile app goes through the Facebook oauth flow and acquires an access token, this isn't enough - because its my service, not the app, that actually needs to talk to facebook to retrieve contact info and a unique user ID. This leads me to think that the OAuth process needs to happen in the context of my service, and not the mobile app. My service then becomes the consumer and Facebook the oauth providor, and the service holds on to the oauth access token, this happens when a user sets up their account for the first time.
If this is the correct approach, where does that leave authentication for the apps? What happens when the user already has an account and installs a fresh instance of a mobile app? I imagine also going through the oauth process, matching up credentials with the data already stored by my service, and then issuing my own "access token" to the app from the service, to authorize that instance of the app. This seems convoluted and hackish.
I'm sure I can't be the only person who is in effect "borrowing" the account system of a third party for a mobile app with a backend, but I really don't see what the proper way to do this is.
What am I not seeing and/or getting conceptually wrong?
OAuth and OAuth 2.0 are widely used authentication protocols which alert resource providers (e.g. Facebook, Twitter, Google, Microsoft etc.) every time resource owners give permission to third parties to run HTTP applications without exposing user passwords.
A few colleagues and I once did a project quite similar in nature, back in university. We authenticated our users through either Facebook or Foursquare, using their respective OAuth APIs.
The native Android version of the app opened up a WebView
with the OAuth provider's start page, which redirected back to our service after authentication. Then our service did a request for the OAuth token from the OAuth provider (Foursquare has some pretty simple instructions). When we got that token, we set up a session using cookies, which we could access from the app.
To validate sessions, we just checked whether the access token was still valid with the provider. We also used the respective providers' unique user IDs to distinguish users.
So yes, what worked for us is: Make the app authenticate & authorise your service, not the app itself.
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