通过Python SDK获取facebook OAuth access_token似乎不起作用，有什么想法吗？

Question

According to http://github.com/facebook/python-sdk/blob/master/src/facebook.py , In my canvas application, i can do the following call to get my access_token, which will work because my user has used facebook to login:

import facebook 

myDict = facebook.get_user_from_cookie(cookies, app_id, app_secret)
# my access_token is myDict["access_token"]

myDict is alwas None, any ideas?

EDIT: I am running on app engine, By "canvas", i mean a facebook app which is ran inside of the facebook platform. Ie, it is'nt on my webiste, iphone or a desktop app. I realize that it is up to the javascript SDK to set the cookie, but to my understanding, if the application is running inside of facebook, then the cookies should allready be set.

Answer 1

For this to work, you need to use the Javascript SDK to init the session at which point the python-sdk is able to read the cookies as set by the javascript-sdk.

Since you are using an IFrame canvas, the cookies set by facebook are not readable by you. In the python-sdk, there is a sample appengine oauth example that includes most of what you need to make it work.

Answer 2

You need to have the Facebook javascript SDK in the bottom of your html-file... the code is:

<!-- loads the facebook javascript API asyncroneously and saves the token in a cookie for use in the python code -->
    <div id="fb-root"></div>
    <script>
        window.fbAsyncInit = function() {
            FB.init({appId: '{{ facebook_app_id }}', status: true, cookie: true, xfbml: true});
        FB.Event.subscribe('auth.logout', function(response) {
        });
        FB.Event.subscribe('auth.login', function(response) {
        });
    };

    (function() {
        var e = document.createElement('script');
        e.type = 'text/javascript';
        e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js';
        e.async = true;
        document.getElementById('fb-root').appendChild(e);
    }());
</script>

Then, in your python handler you can do the

cookie = facebook.get_user_from_cookie(self.request.cookies, FACEBOOK_APP_ID, FACEBOOK_APP_SECRET)
graph = facebook.GraphAPI(cookie["access_token"])
current_user = graph.get_object("me")

This is a working example from my own app

Answer 3

In your facebook app, go to "Edit Settings" => "Migrations" and enable "Canvas Session Parameter". Now you can get the access token from request GET parameters. And, then use python-sdk to access graph API with the access token.

Answer 4

To use crossdomain cookies you must set P3P policies.

For app engine you must set header:

self.response.headers['P3P']='CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"'

And also you must use Facebook Javascript SDK with such params:

FB.init({
    appId  : '***********',
    status : true, // check login status
    cookie : true, // enable cookies to allow the server to access the session
    xfbml  : true,  // parse XFBML
    session: 'json_encoded_sessio_getted_on_backen',
    channelUrl : location.href+'/channel.html'
});

I found that if you do not session here, FB will not send cookies to you iframe.