//get refresh token from file
private static bool trySetRefreshToken()
{
string refreshToken;
string refreshTokenFilePath = YoutubeAuthentication.getRefreshTokenFilePath();
if (File.Exists(refreshTokenFilePath))
{
refreshToken = File.ReadAllText(refreshTokenFilePath);
if (string.IsNullOrWhiteSpace(refreshToken))
{
return(false);
}
else
{
YoutubeAuthentication.refreshToken = refreshToken;
return(true);
}
}
else
{
return(false);
}
}
//initial authentication, get refresh token from API
private static async Task getRefreshToken()
{
// Generates state and PKCE values.
string state = randomDataBase64url(32);
string code_verifier = randomDataBase64url(32);
string code_challenge = base64urlencodeNoPadding(sha256(code_verifier));
const string code_challenge_method = "S256";
// Creates a redirect URI using an available port on the loopback address.
string redirectURI = string.Format("http://{0}:{1}/", IPAddress.Loopback, YoutubeAuthentication.getRandomUnusedPort());
// Creates an HttpListener to listen for requests on that redirect URI.
var http = new HttpListener();
http.Prefixes.Add(redirectURI);
http.Start();
// Creates the OAuth 2.0 authorization request.
string authorizationRequest = string.Format("{0}?response_type=code&scope={6}&redirect_uri={1}&client_id={2}&state={3}&code_challenge={4}&code_challenge_method={5}",
YoutubeAuthentication.authorizationEndpoint,
Uri.EscapeDataString(redirectURI),
Credentials.ClientId,
state,
code_challenge,
code_challenge_method,
Uri.EscapeDataString(YoutubeAuthentication.scopes));
var ps = new ProcessStartInfo(authorizationRequest)
{
UseShellExecute = true,
Verb = "open"
};
// Opens request in the browser.
Process.Start(ps);
// Waits for the OAuth authorization response.
var context = await http.GetContextAsync();
// Sends an HTTP response to the browser.
var response = context.Response;
string responseString = string.Format("<html><head><meta http-equiv='refresh' content='10;url=https://google.com'></head><body>Please return to the app.</body></html>");
var buffer = Encoding.UTF8.GetBytes(responseString);
response.ContentLength64 = buffer.Length;
var responseOutput = response.OutputStream;
responseOutput.Write(buffer, 0, buffer.Length);
responseOutput.Close();
http.Stop();
// Checks for errors.
if (context.Request.QueryString.Get("error") != null)
{
throw new AuthenticationException(string.Format("Authentication error: {0}", context.Request.QueryString.Get("error")));
}
if (context.Request.QueryString.Get("code") == null ||
context.Request.QueryString.Get("state") == null)
{
throw new AuthenticationException("Authentication error: Code or State is null.");
}
// 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 AuthenticationException("Authentication error: Code and State differ.");
}
// Starts the code exchange for refresh token at the token endpoint.
// builds the request
string tokenRequestBody = string.Format("code={0}&redirect_uri={1}&client_id={2}&code_verifier={3}&client_secret={4}&scope=&grant_type=authorization_code",
code,
System.Uri.EscapeDataString(redirectURI),
Credentials.ClientId,
code_verifier,
Credentials.ClientSecret
);
// sends the request
byte[] contentBytes = Encoding.ASCII.GetBytes(tokenRequestBody);
using (ByteArrayContent content = new ByteArrayContent(contentBytes))
{
content.Headers.ContentLength = contentBytes.Length;
content.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
using (HttpResponseMessage message = await YoutubeAuthentication.client.PostAsync(YoutubeAuthentication.tokenEndpoint, content))
{
message.EnsureSuccessStatusCode();
Dictionary <string, string> tokenEndpointDecoded = JsonConvert.DeserializeObject <Dictionary <string, string> >(await message.Content.ReadAsStringAsync());
YoutubeAuthentication.refreshToken = tokenEndpointDecoded["refresh_token"];
File.WriteAllText(YoutubeAuthentication.getRefreshTokenFilePath(), YoutubeAuthentication.refreshToken);
}
}
}
