/*
 *  sexecp by Davide Libenzi (single port inetd-like daemon)
 *  Copyright (C) 2000  Davide Libenzi
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 *
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>



#define SEXECP_PORT 8199




static void usage(char const *prg) {

	fprintf(stderr, "use: %s [-p PORT] [-u UID] [-g GID] PATH [ARGS ...]\n", prg);
}

int main (int ac, char **av) {
	int i, port = SEXECP_PORT, sfd, cfd, uid = -1, gid = -1, one = 1;
	pid_t pid;
	socklen_t alen;
	struct sockaddr_in addr, caddr;

	for (i = 1; i < ac; i++) {
		if (strcmp(av[i], "-p") == 0) {
			if (++i < ac)
				port = atoi(av[i]);
		} else if (strcmp(av[i], "-u") == 0) {
			if (++i < ac)
				uid = atoi(av[i]);
		} else if (strcmp(av[i], "-g") == 0) {
			if (++i < ac)
				gid = atoi(av[i]);
		} else
			break;
	}
	if (i == ac) {
		usage(av[0]);
		return 1;
	}
	if ((sfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		return 2;
	}
#ifdef SO_REUSEADDR
	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (char *) &one,
		       sizeof(one)) < 0) {
		perror("setsockopt(SO_REUSEADDR)");
		return 3;
	}
#endif
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_port = htons(port);
	if (bind(sfd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
		perror("bind");
		return 4;
	}
	listen(sfd, 128);

	for (;;) {
		alen = sizeof(caddr);
		if ((cfd = accept(sfd, (struct sockaddr *) &caddr, &alen)) == -1) {
			perror("accept");
			break;
		}
		if ((pid = fork()) != 0) {
			if (pid == -1)
				perror("fork");
			close(cfd);
			continue;
		}
		if (gid >= 0 && setgid(gid)) {
			perror("setgid");
			return 4;
		}
		if (uid >= 0 && setuid(uid)) {
			perror("setuid");
			return 5;
		}
		dup2(cfd, 0);
		dup2(cfd, 1);
		dup2(cfd, 2);
		close(cfd);
		execvp(av[i], &av[i]);
		exit(5);
	}

	return 0;
}