Using Google experimental implementation of OAuth 2.0 to access existing API endpoints

Question

According to this documentation, process of receiving OAuth access token is straightforward. I would like to see a list of all available API endpoints that is ready to accept OAuth 2.0 access token. But for my current needs i would like to somehow receive username and email of a user using OAuth 2.0 access token.

I successfully can receive, for example, data from this endpoint:

https://www.google.com/m8/feeds/contacts/default/full

But unable to receive data from this endpoint:

https://www.googleapis.com/userinfo/email

I tried both header-base and querystring-base approaches of passing single access token. Here is a header i tried:

Authorization: OAuth My_ACCESS_TOKEN

And I even tried OAuth 1.0 version of Authorization header, but... in OAuth 2.0 we do not have secret access token, for instance. Google use bearer tokens in his implementation of OAuth 2.0, so no additional credentials are required.

Anyone successfully received username and email using Google OAuth 2.0?

Answer 1

I found the answer I was looking for. I had to convert PHP to MVC, but pretty easy:

http://codecri.me/case/430/get-a-users-google-email-address-via-oauth2-in-php/

My MVC Login sandbox code looks like the following. (using JSON.Net http://json.codeplex.com/)

public ActionResult Login()
    {
        string url = "https://accounts.google.com/o/oauth2/auth?";
        url += "client_id=<google-clientid>";
        url += "&redirect_uri=" +
          // Development Server :P 
          HttpUtility.UrlEncode("http://localhost:61857/Account/OAuthVerify");
        url += "&scope=";
        url += HttpUtility.UrlEncode("http://www.google.com/calendar/feeds/ ");
        url += HttpUtility.UrlEncode("http://www.google.com/m8/feeds/ ");
        url += HttpUtility.UrlEncode("http://docs.google.com/feeds/ ");
        url += HttpUtility.UrlEncode("https://mail.google.com/mail/feed/atom ");
        url += HttpUtility.UrlEncode("https://www.googleapis.com/auth/userinfo.email ");
        url += HttpUtility.UrlEncode("https://www.googleapis.com/auth/userinfo.profile ");
        url += "&response_type=code";

        return new RedirectResult(url);
    }

The code returned is proof of Authorization token from the user, which then needs to be turn into a Authentication (accessToken) to access resources. My MVC OAuthVerify then looks like:

    public ActionResult AgentVerify(string code)
    {
        JObject json;

        if (!string.IsNullOrWhiteSpace(code))
        {
            NameValueCollection postData = new NameValueCollection();
            postData.Add("code", code);
            postData.Add("client_id", "<google-clientid>");
            postData.Add("client_secret", "<google-client-secret>");
            postData.Add("redirect_uri", "http://localhost:61857/Account/OAuthVerify");
            postData.Add("grant_type", "authorization_code");

            try
            {   
                json = JObject.Parse(
                  HttpClient.PostUrl(
                    new Uri("https://accounts.google.com/o/oauth2/token"), postData));
                string accessToken = json["access_token"].ToString();
                string refreshToken = json["refresh_token"].ToString();
                bool isBearer = 
                  string.Compare(json["token_type"].ToString(), 
                                 "Bearer", 
                                 true, 
                                 CultureInfo.CurrentCulture) == 0;

                if (isBearer)
                {
                    json = JObject.Parse(
                      HttpClient.GetUrl(
                        new Uri("https://www.googleapis.com/oauth2/v1/userinfo?alt=json"),
                      accessToken));
                    string userEmail = json["email"].ToString();
                }
                return View("LoginGood"); 
            }
            catch (Exception ex)
            {
                ErrorSignal.FromCurrentContext().Raise(ex); //ELMAH
            }
        }
        return View("LoginBad");
    }

To complete how everything works, I've included the HttpClient utility I created in case anyone needed it.

public class HttpClient
{
    public static string GetUrl(Uri url, string OAuth)
    {
        string result = string.Empty;

        using (WebClient httpClient = new WebClient())
        {
            httpClient.Headers.Add("Authorization","OAuth " + OAuth);
            result = httpClient.DownloadString(url.AbsoluteUri);
        }

        return result;
    }

    public static string PostUrl(Uri url, NameValueCollection formData)
    {
        string result = string.Empty;

        using (WebClient httpClient = new WebClient())
        {
            byte[] bytes = httpClient.UploadValues(url.AbsoluteUri, "POST", formData);
            result = Encoding.UTF8.GetString(bytes);
        }

        return result;
    }
}

Again, this is test code just to get it to function, I do not recommend using this as-is in a production environment.