/*
 * Program: bindcmd
 *
 * Description:
 *	This program binds to the given network address and executes the
 *	given command upon accepting a connection.

 * Copyright (c) 2003, John T. Criswell
 * 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 the author nor the 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 OWNER 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.
 *
 * RCS_ID: $Header: /u/jcriswel/src/bindshell/RCS/bindcmd.c,v 1.1 2003/04/11 21:53:56 jcriswel Exp $
 */

#include <stdio.h>
#include <stdlib.h>

#include <unistd.h>
#include <sys/types.h>

#include <sys/socket.h>
#include <netinet/in.h>

int
main (int argc, char ** argv)
{
	/* Network Addresses */
	struct sockaddr_in in_address;
	struct sockaddr *  address;

	/* Network address size */
	int address_size;

	/* Socket file descriptor */
	int s;

	/* New connection socket file descriptor */
	int connfd;

	/* Child process ID */
	int pid;

	/* Variable for setting socket options */
	int yes=1;

	/*
	 * First, determine whether the number of command line arguments is
	 * correct.
	 */
	if (argc < 3)
	{
		usage (argv[0]);
		exit (1);
	}

	/*
	 * Next, construct the network address.
	 */
	in_address.sin_family = AF_INET;
	in_address.sin_addr.s_addr = htonl (0);
	in_address.sin_port = htons (atoi (argv[1]));
	address = (void *) &(in_address);
	address_size = sizeof (in_address);

	/*
	 * Create a socket and bind it to the specified address.
	 */
	if ((s = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
	{
		perror (argv[0]);
		exit (2);
	}

	setsockopt (s, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof (yes));
	if ((bind (s, address, address_size)) == -1)
	{
		perror (argv[0]);
		exit (2);
	}


	if (listen (s, 5))
	{
		perror (argv[0]);
		exit (2);
	}

	while (1)
	{
		if ((connfd = accept (s, NULL, NULL)) == -1)
		{
			perror (argv[0]);
			exit (3);
		}

		/*
		 * Create a new child process.
		 */
		switch (pid = fork())
		{
			case -1:
				perror (argv[0]);
				exit (4);
				break;

			case 0:
				break;

			default:
				close (connfd);
				continue;
		}

		/*
		 * Close the parent's accepting socket.
		 */
		close (s);

		/*
		 * Close stdin and stdout and make them the new socket.
		 */
		close (STDIN_FILENO);
		close (STDOUT_FILENO);
		close (STDERR_FILENO);

		dup (connfd);
		dup (connfd);
		dup (connfd);

		/*
		 * Execute the new program.
		 */
		execvp (argv[2], &(argv[2]));
		perror (argv[0]);
		exit (5);
	}
}

int
usage (char * name)
{
	fprintf (stderr, "%s: <mode> file [file ...]\n", name);
	fprintf (stderr, "\t<mode> can be any combination of r,w,x where:");
	fprintf (stderr, "\t\tr=read access");
	fprintf (stderr, "\t\tw=write access");
	fprintf (stderr, "\t\tx=execute access");
	return 0;
}