better detection of dead connection

added ability for proxy to limit destination hosts + host resolve to ip at client level

Author: force-net

AutoTunnel.Proxy.Node/proxy.js

@@ -1,6 +1,10 @@
 const dgram = require('dgram');
+const dns = require('dns');
 
 var logFunc = console.log;
+var checkFunc = function () {
+	return true;
+};
 
 var start = function (portNumber) {
 	var server = dgram.createSocket('udp4');
@@ -28,25 +32,40 @@ var start = function (portNumber) {
 				var spl = dstHostAndPort.split(':');
 				var dstHost = spl[0];
 				var dstPort = (spl[1] || 12017) * 1;
-				var socket = dgram.createSocket('udp4');
-				socket.on('message', function (bmsg, bep) {
-					var pair = proxyPairs[ep.address + ':' + ep.port];
-					if (pair) {
-						pair.lastActivity = new Date().getTime();
-						server.send(bmsg, 0, bep.size, ep.port, ep.address);
+
+				dns.lookup(dstHost, 4, function (err, addr) {
+					if (err !== null) {
+						logFunc('Cannot resolve host ' + dstHost, err);
+						return;
+					}
+
+					if (!checkFunc(addr, dstHost)) {
+						logFunc('Host ' + dstHost + " was considered as invalid for proxyfying");
+						return
 					}
+
+					dstHost = addr;
+
+					var socket = dgram.createSocket('udp4');
+					socket.on('message', function (bmsg, bep) {
+						var pair = proxyPairs[ep.address + ':' + ep.port];
+						if (pair) {
+							pair.lastActivity = new Date().getTime();
+							server.send(bmsg, 0, bep.size, ep.port, ep.address);
+						}
+					});
+					proxyPairs[ep.address + ':' + ep.port] = {
+						sourceHost: ep.address,
+						sourcePort: ep.port,
+						host: dstHost,
+						port: dstPort,
+						targetSocket: socket,
+						lastActivity: new Date().getTime()
+					};
+					logFunc('Estabilished tunnel ', ep.address + ':' + ep.port + '->' + dstHost + ':' + dstPort);
+
+					// TODO: think about answer
 				});
-				proxyPairs[ep.address + ':' + ep.port] = {
-					sourceHost: ep.address,
-					sourcePort: ep.port,
-					host: dstHost,
-					port: dstPort,
-					targetSocket: socket, 
-					lastActivity: new Date().getTime()
-				};
-				logFunc('Estabilished tunnel ', ep.address + ':' + ep.port + '->' + dstHost + ':' + dstPort);
-				
-				// TODO: think about answer
 			} else {
 				var pair = proxyPairs[ep.address + ':' + ep.port];
 
@@ -97,5 +116,8 @@ module.exports = {
 	},
 	setLogger: function (loggerFunc) {
 		logFunc = loggerFunc;
+	},
+	setAllowedTargetIpCheckFunc: function(checkingFunc) {
+		checkFunc = checkingFunc;
 	}
 };

AutoTunnel.Proxy.Node/proxyStarter.js

@@ -1,3 +1,9 @@
 var p = require('./proxy.js');
 
+p.setAllowedTargetIpCheckFunc(function (dstAddr, dstHost) {
+	// just for example
+	console.log(dstAddr)
+	return /192\.168\.\d+\.\d+/.test(dstAddr);
+});
+
 p.start(12018);

AutoTunnel/ClientSender.cs

@@ -43,8 +43,7 @@ public ClientSender(RemoteServerConfig config, TunnelStorage storage)
 			LogHelper.Log.WriteLine("Tunnel watcher was created for " + config.TunnelHost);
 
 			Task.Factory.StartNew(ReceiveCycle);
-			if (config.KeepAlive)
-				Task.Factory.StartNew(PingCycle);
+			Task.Factory.StartNew(PingCycle);
 			if (config.ConnectOnStart)
 				Init();
 			IPAddress dummy;
@@ -77,7 +76,6 @@ private void CheckHostChange()
 
 		private DateTime _lastInitRequest;
 
-
 		private void Init()
 		{
 			_lastInitRequest = DateTime.UtcNow;
@@ -111,8 +109,8 @@ private void InitInternal()
 
 				_connectEP = destEP;
 
-				Storage.AddSession(new byte[16], destEP).IsClientSession = true;
 				Storage.IncrementEstabilishing();
+				Storage.AddSession(new byte[16], destEP).IsClientSession = true;
 
 				if (proxyEP != null)
 					LogHelper.Log.WriteLine("Initializing connection to " + _config.ConnectHost + " via proxy " + proxyEP);
@@ -179,13 +177,15 @@ private void InitInternal()
 				if (recLength < 4 || _receiveBuffer[0] != (byte)StateFlags.ConnectAnswer)
 				{
 					Console.Error.WriteLine("Invalid server response");
+					Storage.RemoveSession(destEP);
 					return;
 				}
 
 				var decLen = decryptHelper.Decrypt(_receiveBuffer, 4);
 				if (decLen < 9)
 				{
 					Console.Error.WriteLine("Invalid server response");
+					Storage.RemoveSession(destEP);
 					return;
 				}
 
@@ -207,9 +207,27 @@ private void InitInternal()
 
 		private void PingCycle()
 		{
+			DateTime lastReceiveLast = DateTime.MinValue;
 			while (!_disposed)
 			{
-				if (_isInited) _socket.Send(new byte[] { (byte)StateFlags.Ping, 0, 0, 0 }, 4, SocketFlags.None);
+				if (_isInited)
+				{
+					// problem with server? no answers, dropping connection
+					if (Session.LastActivity == lastReceiveLast)
+					{
+						_isInited = false;
+						lastReceiveLast = DateTime.MinValue;
+						if (_config.KeepAlive)
+							Init();
+					}
+
+					if (_config.KeepAlive || _lastSend.Subtract(Session.LastActivity).TotalSeconds > _config.PingInterval)
+					{
+						lastReceiveLast = Session.LastActivity;
+						_socket.Send(new byte[] { (byte)StateFlags.Ping, 0, 0, 0 }, 4, SocketFlags.None);
+						_lastSend = DateTime.UtcNow;
+					}
+				}
 				else
 				{
 					// force renew connection attepmt
@@ -233,12 +251,15 @@ protected override void Send(byte[] packet, int packetLen)
 			{
 				var lenToSend = _encryptHelper.Encrypt(packet, packetLen);
 				var packetToSend = _encryptHelper.InnerBuf;
+				_lastSend = DateTime.UtcNow;
 				_socket.Send(packetToSend, lenToSend, SocketFlags.None);
 			}
 		}
 
 		private readonly byte[] _receiveBuffer = new byte[65536];
 
+		private DateTime _lastSend;
+
 		private void ReceiveCycle()
 		{
 			byte[] buf = _receiveBuffer;
@@ -257,18 +278,20 @@ private void ReceiveCycle()
 				}
 				catch (Exception ex)
 				{
-					LogHelper.Log.WriteLine("Receive data error");
-					_isInited = false;
-					// LogHelper.Log.WriteLine(ex);
-					if (_socket != null)
+					if (_isIniting == 1 && _isInited)
 					{
-						_socket.Dispose();
-						_socket = null;
+						LogHelper.Log.WriteLine("Receive data error");
+						_isInited = false;
+						// LogHelper.Log.WriteLine(ex);
+						if (_socket != null)
+						{
+							_socket.Dispose();
+							_socket = null;
+						}
+
+						if (_config.KeepAlive) Init();
 					}
 
-					if (_config.KeepAlive)
-						Init();
-
 					Thread.Sleep(1000);
 					continue;
 				}
@@ -277,7 +300,7 @@ private void ReceiveCycle()
 				if (len % 16 != 0)
 				{
 					// in any case, this is error
-					// if (buf[0] == 0x3)
+					if (buf[0] != (byte)StateFlags.Pong)
 					{
 						LogHelper.Log.WriteLine("Received an error flag from " + _socket.RemoteEndPoint);
 						_isInited = false;
@@ -287,6 +310,8 @@ private void ReceiveCycle()
 					}
 				}
 
+				Session.UpdateLastActivity();
+
 				var decryptHelper = Session.Decryptor;
 				var decLen = decryptHelper.Decrypt(buf, 0);
 				_packetWriter.Write(decryptHelper.InnerBuf, decLen);

AutoTunnel/Config/MainConfig.cs

@@ -27,5 +27,9 @@ public class MainConfig
 		public int IdleSessionTime { get; set; }
 
 		public string LogFileName { get; set; }
+
+		[DefaultValue(15)]
+		[JsonProperty(DefaultValueHandling = DefaultValueHandling.Populate)]
+		public int PingBackTime { get; set; }
 	}
 }

AutoTunnel/Encryption/DecryptHelper.cs

@@ -34,8 +34,9 @@ public int Decrypt(byte[] data, int offset)
 			decryptor.TransformBlock(data, offset, 16, _headerBuf, 0);
 			var len = _headerBuf[0] | (_headerBuf[1] << 8) | (_headerBuf[2] << 16) | (_headerBuf[3] << 24);
 			if (len > data.Length) return -1;
-			if (_headerBuf[4] != 1 && _headerBuf[5] != 0 && _headerBuf[6] != 'A' && _headerBuf[7] != 'T') return -1;
+			if (_headerBuf[4] != 1 || _headerBuf[5] != 0 || _headerBuf[6] != 'A' || _headerBuf[7] != 'T') return -1;
 			var len16 = (len + 15) & ~15;
+			if (len < 0 || len > _innerBuf.Length) return -1;
 			decryptor.TransformBlock(data, offset + 16, len16, _innerBuf, 0);
 			return len;
 		}

AutoTunnel/Encryption/ServerHandshake.cs

@@ -13,7 +13,7 @@ public ServerHandshake()
 
 		public byte[] GetOutPacket(byte[] inPacket, int len)
 		{
-			if (inPacket[0] != 1 && inPacket[1] != 0 && inPacket[2] != 'A' && inPacket[3] != 'T') return null;
+			if (inPacket[0] != 1 || inPacket[1] != 0 || inPacket[2] != 'A' || inPacket[3] != 'T') return null;
 			var publicRsa = Encoding.UTF8.GetString(inPacket, 4, inPacket.Length - 4);
 			SessionKey = new byte[16];
 			using (var random = RandomNumberGenerator.Create())

AutoTunnel/Listener.cs

@@ -49,7 +49,7 @@ private void CleanupThread()
 					_storage.RemoveSession(os);
 				}
 
-				_stopEvent.WaitOne(10 * 60 * 1000);
+				_stopEvent.WaitOne(_config.IdleSessionTime * 1000);
 			}
 		}
 
@@ -124,6 +124,7 @@ private void StartInternal()
 							{
 								session = _storage.GetSession(ep);
 								if (session != null) session.UpdateLastActivity();
+								s.SendTo(new byte[] { (byte)StateFlags.Pong, 0, 0, 0 }, 4, SocketFlags.None, ep);
 								continue;
 							}
 							else

AutoTunnel/StateFlags.cs

@@ -3,10 +3,17 @@
 	public enum StateFlags : byte
 	{
 		Connecting = 1,
+
 		ConnectAnswer = 2,
+
 		ErrorFromServer = 3,
+
 		Ping = 5,
+
 		ProxyConnecting = 7,
-		ErrorFromProxy = 8
+
+		ErrorFromProxy = 8,
+
+		Pong = 9
 	}
 }