Google OAuth2: Required parameter is missing: grant_type

Question

I have tried just about everything, read every StackOverflow post on this issue but I still can\'t get it to work. Interestingly enough, I am able to get 200 OK

Answer 1

Check the request Encoding.

in my case i was sending .json and was .url

Using Alamofire 3.0

Answer 2

As @BenFortune has already mentioned, I was sending GET parameters as a POST request. It's amazing such a trivial thing has gone unnoticed after trying to figure it out for over an hour.

Now, I blame inconsistencies across OAuth providers for this. In the same application I am doing a GET request to Facebook to obtain access_token: https://graph.facebook.com/oauth/access_token. But Google expects a POST request to obtain access_token: https://accounts.google.com/o/oauth2/token

Correct version:

  var url = 'https://accounts.google.com/o/oauth2/token';
  var payload = {
    grant_type: 'authorization_code',
    code: req.body.code,
    client_id: req.body.clientId,
    client_secret: 'HIDDEN',
    redirect_uri: req.body.redirectUri
  };

  request.post(url, { form: payload }, function(error, response, body) {
    console.log(body);
  });