Facebook Oauth Logout

Question

I have an application that integrates with Facebook using Oauth 2.

I can authorize with FB and query their REST and Graph APIs perfectly well, but when I authorize an active browser session is created with FB. I can then log-out of my application just fine, but the session with FB persists, so if anyone else uses the browser they will see the previous users FB account (unless the previous user manually logs out of FB also).

The steps I take to authorize are:

1. Call [LINK: graph.facebook.com/oauth/authorize?client_id...]

This step opens a Facebook login/connect window if the user's browser doesn't already have an active FB session. Once they log-in to facebook they redirect to my site with a code I can exchange for an oauth token.

2. Call [LINK: graph.facebook.com/oauth/access_token?client_id..] with the code from (1)

Now I have an Oauth Token, and the user's browser is logged into my site, and into FB.

3. I call a bunch of APIs to do stuff: i.e. [LINK: graph.facebook.com/me?access_token=..]

Lets say my user wants to log out of my site. The FB terms and conditions demand that I perform Single Sign Off, so when the user logs out of my site, they also are logged out of Facebook. There are arguments that this is a bit daft, but I'm happy to comply if there is any way of actually achieving that.

I have seen suggestions that:

A. I use the Javascript API to logout: FB.Connect.logout(). Well I tried using that, but it didn't work, and I'm not sure exactly how it could, as I don't use the Javascript API in any way on my site. The session isn't maintained or created by the Javascript API so I'm not sure how it's supposed to expire it either.

B. Use [LINK: facebook.com/logout.php]. This was suggested by an admin in the Facebook forums some time ago. The example given related to the old way of getting FB sessions (non-oauth) so I don't think I can apply it in my case.

C. Use the old REST api expireSession or revokeAuthorization. I tried both of these and while they do expire the Oauth token they don't invalidate the session that the browser is currently using so it has no effect, the user is not logged out of Facebook.

I'm really at a bit of a loose end, the Facebook documentation is patchy, ambiguous and pretty poor. The support on the forums is non-existant, at the moment I can't even log in to the facebook forum, and aside from that, their own FB Connect integration doesn't even work on the forum itself. Doesn't inspire much confidence.

Ta for any help you can offer. Derek

ps. Had to change HTTPS to LINK, not enough karma to post links which is probably fair enough.

Answer 1

the mobile solution suggested by Sumit works perfectly for AS3 Air:

html.location = "http://m.facebook.com/logout.php?confirm=1&next=http://yoursitename.com"

Answer 2

This works as of now - and is documented on facebook's site @ http://developers.facebook.com/docs/authentication/. Not sure how recently it was added to the documentation, pretty sure it wasn't there when I checked Feb-2012

You can programmatically log the user our of Facebook by redirecting the user to

https://www.facebook.com/logout.php?next=YOUR_REDIRECT_URL&access_token=USER_ACCESS_TOKEN

Answer 3

I can programmatically log user out Facebook by redirecting user to

https://www.facebook.com/logout.php?next=YOUR_REDIRECT_URL&access_token=USER_ACCESS_TOKEN

The URL supplied in the next parameter must be a URL with the same base domain as your application as defined in your app's settings.

More details: https://developers.facebook.com/docs/authentication

Answer 4

it's simple just type : $facebook->setSession(null); for logout

Answer 5

For Python developers that want to log user out straight from the backend

At the moment I'm writing this, the trick with m.facebook.com no longer works (at least for me) and user is redirected to the mobile FB login page which obviously is not good for UX.

Fortunately, FB PHP SDK has a semi-documented solution (in case the link doesn't lead to getLogoutUrl() function, just search look for it on that page). This is also mentioned in at least one other on StackOverflow: Facebook php SDK getLogoutUrl() problem.

BTW I've just noticed that Zach Greenberg got it right in this question, but I'm adding my answer as a summary for Python developers.

Answer 6

I am having the same problem. I also login using oauth (I am using RubyOnRails), but for logout, I do it with JavaScript using a link like this:

<a href="/logout" onclick="FB.logout();">Logout</a> 

This first calls the onclick function and performs a logout on facebook, and then the normal /logout function of my site is called.

Though I would prefer a serverside solution as well, but at least it does what I want, it logs me out on both sites.

I am also quite new to the Facebook integration stuff and played around the first time with it, but my general feeling is that the documentation is pretty spread all over the place with lots of outdated stuff.