const ushort Magic16_responderToRequester = 0x60C1; // is used to validate decrypted data
/// <summary>
/// when sending ACK1
/// </summary>
public byte[] Encrypt_ack1_ToResponderTxParametersEncrypted_AtResponder_DeriveSharedDhSecret(Logger logger, RegisterRequestPacket req, RegisterAck1Packet ack1, ConnectionToNeighbor neighbor)
{
IPEndPoint localResponderEndpoint;
if (neighbor != null)
{
localResponderEndpoint = neighbor.LocalEndpoint;
}
else
{
localResponderEndpoint = req.EpEndpoint;
}
if (localResponderEndpoint.Address.AddressFamily != System.Net.Sockets.AddressFamily.InterNetwork)
{
throw new NotImplementedException();
}
SharedDhSecret = _engine.CryptoLibrary.DeriveEcdh25519SharedSecret(LocalEcdhe25519PrivateKey, req.RequesterEcdhePublicKey.Ecdh25519PublicKey);
#region key, iv
BinaryProcedures.CreateBinaryWriter(out var ms, out var writer);
req.GetSharedSignedFields(writer, true);
ack1.GetSharedSignedFields(writer, false, false);
var iv = _engine.CryptoLibrary.GetHashSHA256(ms.ToArray()).Take(16).ToArray();;
ms.Write(SharedDhSecret, 0, SharedDhSecret.Length);
var aesKey = _engine.CryptoLibrary.GetHashSHA256(ms.ToArray()); // here SHA256 is used as KDF, together with common fields from packets, including both ECDH public keys and timestamp
#endregion
// encode localRxParameters
BinaryProcedures.CreateBinaryWriter(out var msRxParameters, out var wRxParameters);
BinaryProcedures.EncodeIPEndPoint(wRxParameters, localResponderEndpoint); // max 19
LocalNeighborToken32.Encode(wRxParameters); // +4 max 23
_engine.LocalNatBehaviour.Encode(wRxParameters); // +2 max 25
if (logger.WriteToLog_detail_enabled)
{
logger.WriteToLog_detail($"encrypting local responder endpoint={localResponderEndpoint}, localNeighborToken={LocalNeighborToken32} into ACK1");
}
wRxParameters.Write(Magic16_responderToRequester); // +2 max 27
var bytesRemaining = RegisterAck1Packet.ToResponderTxParametersEncryptedLength - (int)msRxParameters.Length;
wRxParameters.Write(_engine.CryptoLibrary.GetRandomBytes(bytesRemaining));
var localRxParametersDecrypted = msRxParameters.ToArray(); // total 32 bytes = RegisterAck1Packet.ToResponderTxParametersEncryptedLength
var localRxParametersEncrypted = new byte[localRxParametersDecrypted.Length];
_engine.CryptoLibrary.ProcessAesCbcBlocks(true, aesKey, iv, localRxParametersDecrypted, localRxParametersEncrypted);
if (localRxParametersEncrypted.Length != RegisterAck1Packet.ToResponderTxParametersEncryptedLength)
{
throw new Exception();
}
return(localRxParametersEncrypted);
}
/// <summary>
/// when sending ACK
/// </summary>
public byte[] Encrypt_ack2_ToRequesterTxParametersEncrypted_AtRequester(Logger logger, RegisterRequestPacket req, RegisterAck1Packet ack1, RegisterAck2Packet ack2)
{
if (SharedDhSecret == null)
{
throw new InvalidOperationException();
}
#region aes key, iv
PacketProcedures.CreateBinaryWriter(out var ms, out var writer);
req.GetSharedSignedFields(writer, true);
ack1.GetSharedSignedFields(writer, true, true);
ack2.GetSharedSignedFields(writer, false, false);
var iv = _engine.CryptoLibrary.GetHashSHA256(ms.ToArray()).Take(16).ToArray();
ms.Write(SharedDhSecret, 0, SharedDhSecret.Length);
var aesKey = _engine.CryptoLibrary.GetHashSHA256(ms.ToArray()); // here SHA256 is used as KDF, together with common fields from packets, including both ECDH public keys and timestamp
#endregion
// encode localRxParameters
PacketProcedures.CreateBinaryWriter(out var msRxParameters, out var wRxParameters);
PacketProcedures.EncodeIPEndPoint(wRxParameters, LocalEndpoint); // max 19
LocalNeighborToken32.Encode(wRxParameters); // +4 max 23
if (logger.WriteToLog_detail_enabled)
{
logger.WriteToLog_detail($"encrypting local requester endpoint={LocalEndpoint}, localNeighborToken={LocalNeighborToken32} into ACK2");
}
wRxParameters.Write(Magic16_ipv4_requesterToResponder); // +2 max 25
var bytesRemaining = RegisterAck2Packet.ToRequesterTxParametersEncryptedLength - (int)msRxParameters.Length;
wRxParameters.Write(_engine.CryptoLibrary.GetRandomBytes(bytesRemaining));
var localRxParametersDecrypted = msRxParameters.ToArray();
var localRxParametersEncrypted = new byte[localRxParametersDecrypted.Length];
_engine.CryptoLibrary.ProcessAesCbcBlocks(true, aesKey, iv, localRxParametersDecrypted, localRxParametersEncrypted);
if (localRxParametersEncrypted.Length != RegisterAck2Packet.ToRequesterTxParametersEncryptedLength)
{
throw new Exception();
}
return(localRxParametersEncrypted);
}