/* bounce v0.0.2 by Stok 28 Dec 1998
 * This is a complete rewrite of the patched-irc-bouncer-thingy
 * I wrote some years ago.
 *
 * Usage: bouncer locallistenport sockshost desthost destport
 * Example: 
 * ./bouncer 9999 wingate.blaha.com www.fbi.gov 23 ; telnet localhost 9999
 *
 */ 

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdlib.h>
#include <unistd.h>

#define BUFSIZE 512
#define SOCKSPORT 1080

const char portclosed[] = "socks: Port closed/Permission denyed/Something went wrong\n";

int
main (int argc, char **argv)
{
  int listensocket, insocket, outsocket;
  short listenport, destport;
  struct hostent *socks_he, *dest_he;
  struct sockaddr_in listen_sa, socks_sa;
  int sopts = 1, maxfd;
  char buffer[BUFSIZE];
  int length;
  fd_set rfds;

  if (argc != 5)
    {
      printf ("Usage: %s locallistenport sockshost desthost destport\n", argv[0]);
      exit (1);
    }

  if ((socks_he = gethostbyname (argv[2])) == NULL)
    {
      herror ("gethostbyname");
      exit (1);
    }
  memset (&socks_sa, 0, sizeof (struct sockaddr_in));
  memcpy (&socks_sa.sin_addr.s_addr, socks_he->h_addr_list[0], socks_he->h_length);
  if ((dest_he = gethostbyname (argv[3])) == NULL)
    {
      herror ("gethostbyname");
      exit (1);
    }

  /* no need for errorchecking. only fools mess these up */
  listenport = atoi (argv[1]);
  destport = atoi (argv[4]);

  listensocket = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
  setsockopt (listensocket, SOL_SOCKET, SO_REUSEADDR, &sopts, sizeof (int));

  memset (&listen_sa, 0, sizeof (struct sockaddr_in));

  listen_sa.sin_port = htons (listenport);
  listen_sa.sin_addr.s_addr = htonl (INADDR_ANY);

  socks_sa.sin_port = htons (SOCKSPORT);

  if ((bind (listensocket, (struct sockaddr *) &listen_sa, sizeof (struct sockaddr_in))) == -1)
    {
      perror ("bind");
      exit (1);
    }
  if ((listen (listensocket, 1)) == -1)
    {
      perror ("listen");
      exit (1);
    }

  /* background stuff */
  switch (fork ())
    {
    case -1:
      perror ("fork");
      exit (1);
      break;
    case 0:
#ifndef MYDEBUG
      close (STDIN_FILENO);
      close (STDOUT_FILENO);
      close (STDERR_FILENO);
#endif
      if (setsid () == -1)
        {
    perror ("setsid");
    exit (1);
  }
      break;
    default:
      return 0;
    }

  insocket = accept (listensocket, NULL, 0);
  if (insocket == -1)
    {
      perror ("accept");
      exit (1);
    }
  close (listensocket);
  outsocket = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if ((connect (outsocket, (struct sockaddr *) &socks_sa, sizeof (struct sockaddr_in))) == -1)
    {
      perror ("connect");
      exit (1);
    }

  snprintf (buffer, 8192, "\x04\x01%c%c%c%c%c%c", (destport >> 8) & 0xFF, destport & 0xFF, /* <-- port */
            (char) dest_he->h_addr[0], (char) dest_he->h_addr[1], (char) dest_he->h_addr[2], (char) dest_he->h_addr[3]); /* <-- ip# */

#ifdef MYDEBUG
  for (length = 0; length < 8; length++)
    printf ("%02X:", (unsigned char) buffer[length]);
  printf ("\n");
  for (length = 0; length < 8; length++)
    if (buffer[length] > 'A' && buffer[length] < 'z')
      printf (" %c:", (unsigned char) buffer[length]);
    else
      printf (" *:");
  printf ("\n");
#endif

  /* errorchecking sucks */
  send (outsocket, buffer, 9, 0);
  recv (outsocket, buffer, 8, 0);

  /* handle errors etc */
  if (buffer[1] == 0x5B)
    send (insocket, portclosed, sizeof (portclosed), 0);
#ifdef MYDEBUG
  for (length = 0; length < 8; length++)
    printf ("%02X:", (unsigned char) buffer[length]);
  printf ("\n");
  for (length = 0; length < 8; length++)
    if (buffer[length] > 'A' && buffer[length] < 'z')
      printf (" %c:", (unsigned char) buffer[length]);
    else
      printf (" *:");
  printf ("\n");
#endif

  maxfd = insocket>outsocket?insocket:outsocket;
  while (1)
    {
      FD_ZERO (&rfds);
      FD_SET (insocket, &rfds);
      FD_SET (outsocket, &rfds);
      select (maxfd+1, &rfds, NULL, NULL, NULL);
      if (FD_ISSET (insocket, &rfds))
        {
    length = recv (insocket, buffer, sizeof (buffer), 0);
    if (length == -1 || length == 0)
      break;
    if ((send (outsocket, buffer, length, 0)) == -1)
      break;
  }
      if (FD_ISSET (outsocket, &rfds))
        {
    length = recv (outsocket, buffer, sizeof (buffer), 0);
    if (length == -1 || length == 0)
      break;
    if ((send (insocket, buffer, length, 0)) == -1)
      break;
  }
    }

  close (listensocket);
  close (insocket);
  close (outsocket);
}