internal async Task SendShortSingleMessageAsync(string messageText, UserCertificate senderUserCertificateWithPrivateKeys)
{
if (!DerivedDirectChannelSharedDhSecretsAE)
{
throw new InvalidOperationException("DerivedDirectChannelSharedDhSecretsAE = false");
}
if (Logger.WriteToLog_detail_enabled)
{
Logger.WriteToLog_detail(">> InviteSession.SendShortSingleMessageAsync()");
}
var messageSession = new MessageSession();
var messageStart = new MessageStartPacket()
{
MessageId32 = (uint)_insecureRandom.Next(),
DirectChannelToken32 = RemoteSessionDescription.DirectChannelToken32,
MessageTimestamp64 = _localDrpPeer.Engine.Timestamp64,
};
messageSession.DeriveKeys(_localDrpPeer.CryptoLibrary, SharedPingPongHmacKey, messageStart, DirectChannelSharedDhSecret);
messageStart.EncryptedMessageData = messageSession.EncryptShortSingleMessage(_localDrpPeer.CryptoLibrary, messageText);
// sign with HMAC
messageStart.MessageHMAC = GetMessageHMAC(w => messageStart.GetSignedFieldsForMessageHMAC(w, true));
// send msgstart, wait for msgack
var messageStartUdpData = messageStart.Encode();
if (Logger.WriteToLog_detail_enabled)
{
Logger.WriteToLog_detail("sending MSGSTART and waiting for MSGACK");
}
var messageAckUdpData = await _localDrpPeer.Engine.OptionallySendUdpRequestAsync_Retransmit_WaitForResponse("msgstart 4582", "remote user",
messageStartUdpData, RemoteSessionDescription.DirectChannelEndPoint,
MessageAckPacket.GetScanner(messageStart.MessageId32, this, MessageSessionStatusCode.encryptionDecryptionCompleted) // scanner also verifies HMAC
);
var messageAck = MessageAckPacket.Decode(messageAckUdpData);
if (Logger.WriteToLog_detail_enabled)
{
Logger.WriteToLog_detail("decoded MSGACK");
}
// send msgpart with status=encryptionDecryptionCompleted and signature
if (messageSession.Status != MessageSessionStatusCode.encryptionDecryptionCompleted)
{
throw new InvalidOperationException();
}
var messagePart = new MessagePartPacket
{
MessageId32 = messageStart.MessageId32,
SenderStatus = messageSession.Status,
SenderSignature = UserCertificateSignature.Sign(_localDrpPeer.CryptoLibrary, w =>
{
w.Write(MessageHMACkey);
w.Write(messageSession.AesKey);
w.Write(messageStart.EncryptedMessageData);
w.Write(messageAck.ReceiverFinalNonce);
}, senderUserCertificateWithPrivateKeys)
};
messagePart.MessageHMAC = GetMessageHMAC(messagePart.GetSignedFieldsForMessageHMAC);
var messagePartUdpData = messagePart.Encode();
// wait for msgack status=finalSignatureVerified
if (Logger.WriteToLog_detail_enabled)
{
Logger.WriteToLog_detail("sending MSGPART with message data, waiting for MSGACK");
}
await _localDrpPeer.Engine.OptionallySendUdpRequestAsync_Retransmit_WaitForResponse("msgpart 3681", "remote user", messagePartUdpData,
RemoteSessionDescription.DirectChannelEndPoint,
MessageAckPacket.GetScanner(messageStart.MessageId32, this, MessageSessionStatusCode.finalSignatureVerified) // scanner also verifies HMAC
);
}