private void HandleExchangeFrame(ServerExchangeFrame frame)
{
if (frame.Success)
{
if (frame.Tag.Length > MAX_TAG_LENGTH)
{
OnExceptionThrown(new InvalidDataException("Invalid tag length."));
return;
}
HashPuzzle puzzle = new HashPuzzle(HashAlgorithmName.SHA256, ChallengeDifficulty, ServerNonce);
if (!puzzle.VerifySolution(frame.Solution))
{
OnExceptionThrown(new InvalidDataException("Challenge failed."));
return;
}
if (frame.Tag.Length == 0)
{
if (MutualAuthenticationRequired)
{
OnExceptionThrown(new InvalidDataException("Tag missing."));
return;
}
}
else
{
_remoteTag = Tag.Deserialize(frame.Tag);
if (TrustedIssuers != null && _remoteTag.Verify(TrustedIssuers))
{
IsMutuallyAuthenticated = true;
}
if (MutualAuthenticationRequired)
{
OnExceptionThrown(new InvalidDataException("Invalid tag."));
return;
}
}
ClientNonce = frame.Nonce;
BufferFrame(new ServerValidateFrame(), FrameState.ServerValidate);
SendExchangeFrame(GetPublicKey(), IsMutuallyAuthenticated);
}
else
{
OnChallengeFailed();
//TODO: check if we're disposed
ServerNonce = CreateNonce(NONCE_LENGTH);
BufferFrame(new ServerExchangeFrame(), FrameState.ServerExchange);
SendNegotiateFrame();
}
}
private void HandleNegotiateFrame(ClientNegotiateFrame frame)
{
if (frame.MinVersion > MAX_VERSION || frame.MaxVersion < MIN_VERSION)
{
OnExceptionThrown(new InvalidDataException("Invalid protocol version."));
return;
}
if (frame.Difficulty > MAX_DIFFICULTY)
{
OnExceptionThrown(new InvalidDataException("Challenge difficulty is too high."));
return;
}
if (frame.IsMutual && LocalTag == null)
{
OnExceptionThrown(new InvalidOperationException("Server requires mutual authentication."));
return;
}
HashPuzzle puzzle = new HashPuzzle(HashAlgorithmName.SHA256, frame.Difficulty, frame.Nonce);
bool success = puzzle.FindSolution();
if (success)
{
Version = Math.Min(frame.MaxVersion, MAX_VERSION);
ServerNonce = frame.Nonce;
ClientNonce = CreateNonce(NONCE_LENGTH);
BufferFrame(new ClientExchangeFrame(), FrameState.ClientExchange);
}
else
{
BufferFrame(new ClientNegotiateFrame(), FrameState.ClientNegotiate);
}
SendExchangeFrame(success, puzzle.Solution);
}