/// <summary>
/// Validates the server's key by asking it to authenticate to the client.
/// </summary>
private async Task VerifyServer()
{
var token = GpgAuthToken.NewToken();
var encryptedToken = await _pgp.EncryptStringAsync(token.Token, _serverKey);
var auth = new Dictionary <string, dynamic>
{
{ "gpg_auth", new Dictionary <string, dynamic>
{
{ "keyid", _clientKey.Fingerprint },
{ "server_verify_token", encryptedToken }
} }
};
var result = await _session.Post(URL_LOGIN, auth).SendAsync();
result.ThrowIfFailed();
GpgAuthHeaders.Validate(result.Response.Headers, GpgAuthState.VerifyServer);
var verifyToken = new GpgAuthToken(result.Response.Headers.GetValue("X-GPGAuth-Verify-Response"));
if (verifyToken.Token != token.Token)
{
throw new Exception("The server failed to prove it can use the advertised OpenPGP key.");
}
}
/// <summary>
/// Sends the decrypted client token back to the server for verification.
/// </summary>
/// <param name="token">Decrypted client token, obtained from <see cref="GetAndDecryptToken"/>.</param>
private async Task VerifyToken(GpgAuthToken token)
{
var auth = new Dictionary <string, dynamic>
{
{ "gpg_auth", new Dictionary <string, dynamic>
{
{ "keyid", _clientKey.Fingerprint },
{ "user_token_result", token.Token }
} }
};
var result = await _session.Post(URL_LOGIN, auth).SendAsync();
GpgAuthHeaders.Validate(result.Response.Headers, GpgAuthState.Complete);
}
/// <summary>
/// Retrieves a token from the server, and decrypts it.
/// </summary>
/// <param name="passphrase">The passphrase to use to decrypt the client key.</param>
/// <returns>The decrypted token.</returns>
private async Task <GpgAuthToken> GetAndDecryptToken(SecureString passphrase)
{
var auth = new Dictionary <string, dynamic>
{
{ "gpg_auth", new Dictionary <string, dynamic>
{
{ "keyid", _clientKey.Fingerprint },
} }
};
var result = await _session.Post(URL_LOGIN, auth).SendAsync();
GpgAuthHeaders.Validate(result.Response.Headers, GpgAuthState.DecryptToken);
// Decrypt the token
var encrypted = result.Response.Headers.GetValue("X-GPGAuth-User-Auth-Token");
var decoded = WebUtility.UrlDecode(encrypted.Replace("\\+", " "));
var decrypted = await _pgp.DecryptStringAsync(decoded, _clientKey, passphrase);
// Validate the token
var token = new GpgAuthToken(decrypted);
return(token);
}