public async Task PerformAuthenticationAsync(Action activateCallback)
{
// Clear any previous tokens
this.AccessToken = null;
this.RefreshToken = null;
// Generates state and PKCE values.
string state = OAuthHelpers.RandomDataBase64url(32);
string codeVerifier = OAuthHelpers.RandomDataBase64url(32);
string codeChallenge = OAuthHelpers.Base64urlencodeNoPadding(OAuthHelpers.Sha256(codeVerifier));
// Creates a redirect URI using an available port on the loopback address.
string redirectURI = string.Format("http://{0}:{1}/", IPAddress.Loopback, OAuthHelpers.GetRandomUnusedPort());
Output("redirect URI: " + redirectURI);
// Creates an HttpListener to listen for requests on that redirect URI.
var http = new HttpListener();
http.Prefixes.Add(redirectURI);
Output("Listening..");
http.Start();
// Creates the OAuth 2.0 authorization request.
string authorizationRequest = string.Format("{0}?response_type=code&scope=openid%20profile&redirect_uri={1}&client_id={2}&state={3}&code_challenge={4}&code_challenge_method={5}",
AuthorizationEndpoint,
System.Uri.EscapeDataString(redirectURI),
ClientID,
state,
codeChallenge,
CodeChallengeMethod);
// Opens request in the browser.
System.Diagnostics.Process.Start(authorizationRequest);
// Waits for the OAuth authorization response.
var context = await http.GetContextAsync();
// Brings this app back to the foreground.
activateCallback?.Invoke();
// Sends an HTTP response to the browser.
var response = context.Response;
var buffer = Encoding.UTF8.GetBytes(ResponseString);
response.ContentLength64 = buffer.Length;
var responseOutput = response.OutputStream;
Task responseTask = responseOutput.WriteAsync(buffer, 0, buffer.Length).ContinueWith((task) =>
{
responseOutput.Close();
http.Stop();
Console.WriteLine("HTTP server stopped.");
});
// Checks for errors.
if (context.Request.QueryString.Get("error") != null)
{
throw new OAuthException(string.Format("OAuth authorization error: {0}.", context.Request.QueryString.Get("error")));
}
if (context.Request.QueryString.Get("code") == null ||
context.Request.QueryString.Get("state") == null)
{
throw new OAuthException("Malformed authorization response. " + context.Request.QueryString);
}
// extracts the code
var code = context.Request.QueryString.Get("code");
var incoming_state = context.Request.QueryString.Get("state");
// Compares the receieved state to the expected value, to ensure that
// this app made the request which resulted in authorization.
if (incoming_state != state)
{
throw new OAuthException(string.Format("Received request with invalid state ({0})", incoming_state));
}
Output("Authorization code: " + code);
// Starts the code exchange at the Token Endpoint.
await PerformCodeExchange(code, codeVerifier, redirectURI);
}