Get user authentication using browser with Restsharp and OAUTH

Question

The API of Khan Academy requires that the user will authenticate using his/her web browser. Here is Khan Academy's authentication manual

When trying to getting a request token, the request fails because the user himself did not approve it.

Here's my code:

string _server_url = "http://www.khanacademy.org";
string _consumer_key = "key";
string _consumer_secret = "secret";

//Request token
RestClient client = new RestClient();
client.BaseUrl = _server_url;
client.Authenticator = OAuth1Authenticator.ForRequestToken(_consumer_key, _consumer_secret);
RestRequest request = new RestRequest("api/auth/request_token", Method.GET);

var response = client.Execute(request);

var qs = HttpUtility.ParseQueryString(response.Content);
var oauth_token = qs["oauth_token"];
var oauth_token_secret = qs["oauth_token_secret"];

both oauth_token and oauth_token_secret are returned as null.

Is there any way to start the browser and ask the user to authenticate while using RestSharp?

Answer 1

Eventually I used a WebBrowser object in WinForms to solve this issue. Here's my code:

    public Authenticate()
    {
        InitializeComponent();
        //Request token
        Client.BaseUrl = Server_url;
        Client.Authenticator = OAuth1Authenticator.ForRequestToken(Consumer_key, Consumer_secret);
        RestRequest request = new RestRequest("api/auth/request_token", Method.GET);


        //request response
        var response = Client.Execute(request);

        //pull out the google url out of the response (which is a HTML page)
        int index = response.Content.IndexOf("/api/auth/request_token_callback/google/") + "/api/auth/request_token_callback/google/".Length;
        string key = response.Content.Substring(index, 10);
        if (response.StatusDescription.Equals("OK"))
        {
            var url = response.ResponseUri.AbsoluteUri;
            webBrowser.Navigate(new Uri(url));
        }
        else
            throw new Exception();
    }

And when the user finishes to authenticate through Google/Facebook/Email, I can pull out his oauth_token and oauth_token_secret using webBrowser.Url:

            string source = webBrowser.Url.ToString();
            var qs = HttpUtility.ParseQueryString(source);
            var oauth_token_secret = HttpUtility.ParseQueryString(source).Get(0);

            var oauth_token = qs["oauth_token"];
            Client.BaseUrl = Server_url;
            Client.Authenticator = OAuth1Authenticator.ForAccessToken(Consumer_key, Consumer_secret, oauth_token, oauth_token_secret);

By the way, there's a bug with HttpUtility.ParseQueryString(source). see this post for a solution (that's also implemented here)