ICMP tunnel in c#?

Question

Computer networks

Hello, I need help with ICMP tunnel using c#.
The essence is simple, I need to enclose the payload in the Ping package. Create two applications or functions "client" and "server".
The "client" must send a packet with a payload (text) to a specific ip.
The "server" (more complicated) accepts all ICMP packets, takes the payload from them and issues (string) what is written in them.

Ps I did not work with the Internet, so I can not quickly figure it out. I checked githab, but there are 43 projects with ICMP and 1 with ICMP tunnel, while there is no "client-server". I found an example on the microsoft website, where the line with data seems to be like this load (but this is not accurate), it did not work.
Link: https://docs.microsoft.com/ru-ru/dotnet/api/system...

I looked again, stumbled upon another one, it seems that there is even an ip, but there is no payload and it also does not work.
Link: https://coderoad.ru/626541/Listening-ICMP-package...

Help please.
Thank you in advance.

Answer 1

There is no clarification in the description, but judging by the code fragment in the comment, we are talking only about transmission via ICMP Echo.
Customer:

using System;
using System.Net;
using System.Net.NetworkInformation;
using System.Text;

namespace icmp_client
{
    public class IcmpClient
    {
        // args[0] can be an IPaddress or host name.
        // args[1] message for send
        public static void Main (string[] args)
        {
            Ping pingSender = new Ping ();
            PingOptions options = new PingOptions ();

            // Use the default Ttl value which is 128,
            // but change the fragmentation behavior.
            options.DontFragment = true;

            // Create a buffer of 32 bytes of data to be transmitted.
            string data = args[1];
            byte[] buffer = Encoding.ASCII.GetBytes(data);

            int timeout = 120;
            PingReply reply = pingSender.Send(args[0], timeout, buffer, options);
            if (reply.Status == IPStatus.Success)
            {
                Console.WriteLine("Address: {0}", reply.Address.ToString ());
                Console.WriteLine("Message: {0}", data);
                Console.WriteLine("Buffer size: {0}", reply.Buffer.Length);
            }
        }
    }
}

Command line options:

1. IP address or name of the recipient of the message
   
2. Message text
   

For example: icmp_client.exe 127.0.0.1 "test msg"
Server:

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace icmp_server
{
    public class IcmpServer
    {
        private const int ICMP_TYPE_OFFSET = 20;
        private const int ICMP_TYPE_ECHO_REQUEST = 8;
        private const int PAYLOAD_OFFSET = 28;
        
        public static void Main(string[] args)
        {            
            IPAddress ipAddr = IPAddress.Parse(args[0]);
            IPEndPoint ipMyEndPoint = new IPEndPoint(ipAddr, 0);
            EndPoint myEndPoint = (ipMyEndPoint);
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);
            socket.Bind(myEndPoint);
            socket.IOControl(IOControlCode.ReceiveAll, BitConverter.GetBytes(1), null); 
            while (true)
            {
                Byte[] ReceiveBuffer = new Byte[socket.ReceiveBufferSize];
                var nBytes = socket.ReceiveFrom(ReceiveBuffer, ReceiveBuffer.Length, SocketFlags.None, ref myEndPoint);
                var icmpType = ReceiveBuffer[ICMP_TYPE_OFFSET];
                if (icmpType == ICMP_TYPE_ECHO_REQUEST)
                {
                    Console.WriteLine("Echo Request received");
                    Console.WriteLine("Received: {0} bytes", nBytes);
                    if(nBytes > PAYLOAD_OFFSET)
                    { 
                      var payLoadSize = nBytes - PAYLOAD_OFFSET;
                      byte[] payLoad = new byte[payLoadSize];
                      Array.Copy(ReceiveBuffer, PAYLOAD_OFFSET, payLoad, 0, payLoadSize);
                      string msg = Encoding.ASCII.GetString(payLoad);
                      Console.WriteLine("Data hex: {0}", BitConverter.ToString(payLoad));
                      Console.WriteLine("Data text: {0}", msg);
                    }
                    Console.WriteLine("---------------");
                }
            }

        }
    }
}

Command line options:

1. IP address of the message receiving interface
   

For example: icmp_server.exe 127.0.0.1 Please
note that the server will need to run with Administrator rights, more details: https://docs.microsoft.com/en-us/windows/win32/win... .
For a better understanding, I recommend (at least) to read:

• https://ru.wikipedia.org/wiki/IPv4
  
• https://ru.wikipedia.org/wiki/ICMP
  
• https://docs.microsoft.com/ru-ru/dotnet/api/system...