Google ClientLogin

gistfile1.cs

public static class ClientLogin
{
	/// <summary>
	/// Client login url where we'll post login data to.
	/// </summary>
	private static string clientLoginUrl =
		@"https://www.google.com/accounts/ClientLogin";

	/// <summary>
	/// Data to be sent with the post request.
	/// </summary>
	private static string postData =
		@"service={0}&continue=http://www.google.com/&Email={1}&Passwd={2}&source={3}";

	/// <summary>
	/// Get the Auth token you get after a successful login.
	/// You'll need to reuse this token in the header of each new request you make.
	/// </summary>
	/// <param name="service"></param>
	/// <param name="username"></param>
	/// <param name="password"></param>
	/// <param name="source"></param>
	/// <returns></returns>
	public static string GetAuthToken(
		string service, string username, string password, string source)
	{
		// Get the response that needs to be parsed.
		string response = PostRequest(service, username, password, source);

		// Get auth token.
		string auth = ParseAuthToken(response);
		return auth;
	}

	/// <summary>
	/// Parse the Auth token from the response.
	/// </summary>
	/// <param name="response"></param>
	/// <returns></returns>
	private static string ParseAuthToken(string response)
	{           
		// Get the auth token.
		string auth = "";
		try
		{
			auth = new Regex(@"Auth=(?<auth>\S+)").Match(response).Result("${auth}");
		}
		catch (Exception ex)
		{
			throw new AuthTokenException(ex.Message);
		}

		// Validate token.
		if (string.IsNullOrEmpty(auth))
		{
			throw new AuthTokenException("Missing or invalid 'Auth' token.");
		}

		// Use this token in the header of each new request.
		return auth;
	}

	/// <summary>
	/// Create a post request with all the login data. This will return something like:
	///
	/// SID=AQAAAH1234
	/// LSID=AQAAAH8AA5678
	/// Auth=AQAAAIAAAAB910
	///
	/// And we need the Auth token for each subsequent request.
	/// </summary>
	/// <param name="service"></param>
	/// <param name="email"></param>
	/// <param name="password"></param>
	/// <param name="source"></param>
	/// <returns></returns>
	private static string PostRequest(
		string service, string email, string password, string source)
	{
		// Get the current post data and encode.
		ASCIIEncoding ascii = new ASCIIEncoding();
		byte[] encodedPostData = ascii.GetBytes(
			String.Format(postData, service, email, password, source));

		// Prepare request.
		HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(clientLoginUrl);
		request.Method = "POST";
		request.ContentType = "application/x-www-form-urlencoded";
		request.ContentLength = encodedPostData.Length;

		// Write login info to the request.
		using (Stream newStream = request.GetRequestStream())
			newStream.Write(encodedPostData, 0, encodedPostData.Length);

		// Get the response that will contain the Auth token.
		HttpWebResponse response = null;
		try
		{
			response = (HttpWebResponse)request.GetResponse();
		}
		catch (WebException ex)
		{
			HttpWebResponse faultResponse = ex.Response as HttpWebResponse;
			if (faultResponse != null && faultResponse.StatusCode == HttpStatusCode.Forbidden)
				throw new IncorrectUsernameOrPasswordException(
					faultResponse.StatusCode, faultResponse.StatusDescription);
			else
				throw;
		}

		// Check for login failed.
		if (response.StatusCode != HttpStatusCode.OK)
			throw new LoginFailedException(
				response.StatusCode, response.StatusDescription);

		// Read.
		using (StreamReader reader = new StreamReader(response.GetResponseStream()))
			return reader.ReadToEnd();
	}
}