freebsd-skq/usr.sbin/daemon/daemon.c

/*-
 * Copyright (c) 1999 Berkeley Software Design, Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Berkeley Software Design Inc's name may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``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 BERKELEY SOFTWARE DESIGN INC 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.
 *
 *	From BSDI: daemon.c,v 1.2 1996/08/15 01:11:09 jch Exp
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>

#include <err.h>
#include <errno.h>
#include <pwd.h>
#include <grp.h>
#include <libutil.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static void restrict_process(const char *, const char *);
static void usage(void);

int
main(int argc, char *argv[])
{
	struct pidfh *pfh;
	int ch, nochdir, noclose, errcode;
	const char *pidfile, *user, *group;
	pid_t otherpid;

	nochdir = noclose = 1;
	pidfile = user = group = NULL;
	while ((ch = getopt(argc, argv, "-cfg:p:u:")) != -1) {
		switch (ch) {
		case 'c':
			nochdir = 0;
			break;
		case 'f':
			noclose = 0;
			break;
		case 'u':
			user = optarg;
			break;
		case 'g':
			group = optarg;
			break;
		case 'p':
			pidfile = optarg;
			break;
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;

	if (argc == 0)
		usage();

	if (user || group) {
		if (getuid() != 0)
			errx(1, "only root user is allowed to chroot "
			    "and change UID/GID");
		restrict_process(user, group);
	}

	/*
	 * Try to open the pidfile before calling daemon(3),
	 * to be able to report the error intelligently
	 */
	if (pidfile) {
		pfh = pidfile_open(pidfile, 0600, &otherpid);
		if (pfh == NULL) {
			if (errno == EEXIST) {
				errx(3, "process already running, pid: %d",
				    otherpid);
			}
			err(2, "pidfile ``%s''", pidfile);
		}
	}

	if (daemon(nochdir, noclose) == -1)
		err(1, NULL);

	/* Now that we are the child, write out the pid */
	if (pidfile)
		pidfile_write(pfh);

	execvp(argv[0], argv);

	/*
	 * execvp() failed -- unlink pidfile if any, and
	 * report the error
	 */
	errcode = errno; /* Preserve errcode -- unlink may reset it */
	if (pidfile)
		pidfile_remove(pfh);

	/* The child is now running, so the exit status doesn't matter. */
	errc(1, errcode, "%s", argv[0]);
}

static void
restrict_process(const char *user, const char *group)
{
	struct group *gr = NULL;
	struct passwd *pw = NULL;
	errno = 0;

	if (group != NULL) {
		if (initgroups(user, gr->gr_gid) == -1)
			errx(1, "User not in group list");
		if ((gr = getgrnam(group)) == NULL)
			errx(1, "Group %s does not exist", group);
		if (setgid(gr->gr_gid) == -1)
			err(1, "%s", group);
	}

	if (user != NULL) {
		if ((pw = getpwnam(user)) == NULL)
			errx(1, "User %s does not exist", user);
		if (setuid(pw->pw_uid) == -1)
			err(1, "%s", user);
	}
}

static void
usage(void)
{
	(void)fprintf(stderr,
	    "usage: daemon [-cf] [-g group] [-p pidfile] [-u user] command "
		"arguments ...\n");
	exit(1);
}