public NetworkCommand ProcessCommand()
{
NetworkCommand command = this.ReceiveCommand();
this.LastReceivedCommand = command;
switch (command)
{
case NetworkCommand.Ping:
{
long time = this.ReceiveLong();
this.SendCommand(NetworkCommand.PingBack, time);
}
break;
case NetworkCommand.PingBack:
{
long time = this.ReceiveLong();
TimeSpan elapsed = TimeSpan.FromTicks(DateTime.Now.Ticks - time);
this.LogString(this, "Returning ping time: " + elapsed.ToString() + "\r\n");
}
break;
case NetworkCommand.ComputeECPoint:
{
var factor = ecc.GetRandomFactorModN();
var multiplication = ecc.ECMultiplication(factor);
var factorBytes = factor.ToByteArray();
Array.Resize(ref factorBytes, ecc.BytesCount);
var eccBytes = multiplication.UncompressedBytes;
this.SendCommand(NetworkCommand.Response_ComputeECPoint, factorBytes.Concat(eccBytes));
}
break;
case NetworkCommand.Response_ComputeECPoint:
{
byte[] data = this.ReceiveBytes(ecc.BytesCount * 3);
var factor = data.Take(ecc.BytesCount).ToBigInteger();
var verification = ecc.ECMultiplication(factor).UncompressedBytes;
bool ok = Enumerable.Range(0, verification.Length).All(idx => data[ecc.BytesCount + idx] == verification[idx]);
if (!ok)
{
throw new InvalidOperationException("ECC verification failed!!");
}
}
break;
case NetworkCommand.RegisterClient:
{
var point = new ECC521Point(this.ReceiveBytes(ecc.CompressedBytesCount), true);
string clientIdentifiers = this.ReadString();
this.serverChallenge = ecc.GetRandomFactorModN();
var clientChallengePoint = point.Multiply(this.serverChallenge);
string userName = ConfigurationFile.LoadFromFile().GetUserName(clientIdentifiers);
var currentTime = DateTime.Now.Ticks;
this.SendCommand(NetworkCommand.SolveServerChallenge,
clientChallengePoint.UncompressedBytes.
Concat(BitConverter.GetBytes(currentTime)).
Concat(userName.StringToVariableLengthBytes()));
}
break;
case NetworkCommand.SolveServerChallenge:
{
var point = new ECC521Point(this.ReceiveBytes(ecc.BytesCount * 2), false);
var serverTimeBytes = this.ReceiveBytes(8);
this.RegisteredUserName = this.ReadString();
var secretPoint = point.Multiply(this.clientSecretKey.ModInverse(ecc.N));
var solution = RIPEMD160.Hash(secretPoint.CompressedBytes);
this.SendCommand(NetworkCommand.FollowsServerChallengeSolution, solution.Concat(serverTimeBytes));
this.SetSharedKey(SHA256.Hash(secretPoint.UncompressedBytes), solution.Take(128 / 8).ToArray());
}
break;
case NetworkCommand.FollowsServerChallengeSolution:
{
byte[] ripemd160Solution = this.ReceiveBytes(160 / 8);
var challengeDuration = TimeSpan.FromTicks(DateTime.Now.Ticks - BitConverter.ToInt64(this.ReceiveBytes(8), 0));
var secretPoint = ecc.G.Multiply(serverChallenge);
byte[] verification = RIPEMD160.Hash(secretPoint.CompressedBytes);
if (!ripemd160Solution.IsSameAs(verification))
{
throw new InvalidOperationException("Authentication failed.");
}
this.SetSharedKey(SHA256.Hash(secretPoint.UncompressedBytes), verification.Take(128 / 8).ToArray());
this.LogString(this, "Client challenge duration: " + challengeDuration.ToString() + "\r\n");
}
break;
case NetworkCommand.IncomingMessageReplyToAll:
case NetworkCommand.IncomingMessageNoReply:
{
string incomingMessage = this.DecodeIncomingMessage();
this.ProcessStringCommand(this, incomingMessage);
}
break;
case NetworkCommand.RegisterNewUserName:
{
string clientIdentifiers = this.ReadString();
string userName = this.ReadString();
UserInformation userInformation = new UserInformation()
{
ClientIdentifiers = clientIdentifiers,
UserName = userName
};
var configurationFile = ConfigurationFile.LoadFromFile();
configurationFile.AddUser(userInformation);
configurationFile.SaveToFile();
}
break;
}
return(command);
}
