Question

I am using the “Server Side” flow to get a user’s permissions to access some information using Python on Google Appengine.

I am able to get the server generated code from Facebook after the user clicks on the “Allow” button.

However when I get the access token, I run into the following error:

Traceback (most recent call last):
File
“/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/init.py”,
line 515, in call
handler.get(*groups) File “/base/data/home/apps/finisherph/1.348502373491720746/controllers.py”,
line 21, in get
data = urllib2.urlopen(access_token_url)
File
“/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 124, in urlopen
return _opener.open(url, data) File
“/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 387, in open
response = meth(req, response) File
“/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 498, in http_response
‘http’, request, response, code, msg, hdrs) File
“/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 425, in error
return self._call_chain(*args) File
“/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 360, in _call_chain
result = func(*args) File “/base/python_runtime/python_dist/lib/python2.5/urllib2.py”,
line 506, in http_error_default
raise HTTPError(req.get_full_url(), code,
msg, hdrs, fp) HTTPError: HTTP Error
400: Bad Request

Here’s the code in my controller where the response from facebook goes after user clicks on the “Allow” button. It’s still a hack so the code is a little bit dirty. Still trying to make it work.

class Register(webapp.RequestHandler):
            def get(self):
                code=self.request.get('code')
                logging.debug("code: "+code)
                accesst_url=["https://graph.facebook.com/oauth/access_token?"]
                accesst_url.append("client_id=CLIENT_ID&")
                import urllib         
                accesst_url.append(urllib.urlencode
                    ({'redirect_uri':'http://my.website.com/register/facebook/'}))
                accesst_url.append('&')
                accesst_url.append("client_secret=CLIENT_SECRET&")
                accesst_url.append("".join(["code=",str(code)]))
                logging.debug(accesst_url)
                access_token_url="".join(accesst_url)
                logging.debug(access_token_url)
                import urllib2
                data = urllib2.urlopen(access_token_url)
                    ...
                    ...

The error occurs here:

data = urllib2.urlopen(access_token_url)

when I copy and paste the access_token_url from my logs, I get the following error:

{ “error”: {
“type”: “OAuthException”,
“message”: “Error validating verification code.” } }

What am I missing here?

Answer 1

It looks like you are trying to access the access_token as url, which is not quite right.

Here is an example which illustrates how OAuth authentication via FB is done over GAE.

• You go to the https://graph.facebook.com/oauth/authorize? with your client_id and redirect_uri
• Upon authorization, it gives a code and you use code and client_secret to get an access_token from https://graph.facebook.com/oauth/access_token
• And then you use that access_token to operate as the Facebook user.