/// <summary>
/// This method handles the response from Google and returns an <see cref="AuthenticationResponse"/> object
/// </summary>
/// <returns>AuthenticationResponse with details such as the IDTokenPayload</returns>
/// <exception cref="InvalidStateException">Thrown when the CSRF token is missing or there is a mismatch</exception>
/// <exception cref="AuthenticationException">Thrown when there was an error in the process of authentication at Google</exception>
/// <exception cref="HashAlgorithmNotSupportedException">Thrown when the used algorithm for hashing is not supported</exception>
/// <exception cref="SignatureVerificationException">Thrown when the signature seems to be broken</exception>
public static AuthenticationResponse HandleResponse()
{
string code = HttpContext.Current.Request.Params["code"];
string state = HttpContext.Current.Request.Params["state"];
string error = HttpContext.Current.Request.Params["error"];
NameValueCollection stateParameters = HttpUtility.ParseQueryString(state);
string responseState = stateParameters[ResponseStateParameter];
bool receiveProfileInformation = Boolean.Parse(stateParameters[ReceiveProfileInformation]);
if (!AuthenticationUtility.VerifyCsrfTokenInState(stateParameters))
{
throw new InvalidStateException(responseState);
}
if (!String.IsNullOrWhiteSpace(error))
{
throw new AuthenticationException(error, responseState);
}
NameValueCollection parameters = new NameValueCollection();
parameters.Add("code", code);
parameters.Add("client_id", Configuration.ClientID);
parameters.Add("client_secret", Configuration.ClientSecret);
parameters.Add("redirect_uri", Configuration.RedirectURI);
parameters.Add("grant_type", "authorization_code");
TokenInformation token = WebClientUtility.GetIDTokenPayload(parameters);
IDTokenPayload idTokenPayload = DecodeAndVerifyIDTokenPayload(token.IDToken, GetRSACryptoServiceProvider(), true);
UserInformation userInformation = (receiveProfileInformation)?WebClientUtility.GetUserInformation(token.AccessToken):null;
return(new AuthenticationResponse(responseState, idTokenPayload, userInformation));
}
/// <summary>
/// Converts the JWKs to a list of <see cref="RSACryptoServiceProvider"/>.
/// The JWKs are being downloaded directly from the link provided in
/// the OIDC Discovery Document.
/// </summary>
/// <returns>List of RSACryptoServiceProviders</returns>
private static List <RSACryptoServiceProvider> GetRSACryptoServiceProvider()
{
JsonWebKeyIndex jsonWebKeyIndex = WebClientUtility.GetJsonWebKeyIndex();
List <RSACryptoServiceProvider> providers = new List <RSACryptoServiceProvider>();
jsonWebKeyIndex.Keys.ForEach(jsonWebToken =>
{
RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
provider.ImportParameters(new RSAParameters
{
Exponent = ConversionUtility.Base64UrlDecode(jsonWebToken.Exponent),
Modulus = ConversionUtility.Base64UrlDecode(jsonWebToken.Modulus)
});
providers.Add(provider);
});
return(providers);
}