daemon.c revision 231909 
1/*-
2 * Copyright (c) 1999 Berkeley Software Design, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 *    promote products derived from this software without specific prior
14 *    written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 *	From BSDI: daemon.c,v 1.2 1996/08/15 01:11:09 jch Exp
29 */
30
31#include <sys/cdefs.h>
32__FBSDID("$FreeBSD: head/usr.sbin/daemon/daemon.c 231909 2012-02-19 10:20:37Z trociny $");
33
34#include <sys/param.h>
35#include <sys/wait.h>
36
37#include <err.h>
38#include <errno.h>
39#include <pwd.h>
40#include <libutil.h>
41#include <login_cap.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <unistd.h>
45
46static void restrict_process(const char *);
47static void wait_child(pid_t pid);
48static void usage(void);
49
50int
51main(int argc, char *argv[])
52{
53	struct pidfh *pfh = NULL;
54	int ch, nochdir, noclose;
55	const char *pidfile, *user;
56	pid_t otherpid, pid;
57
58	nochdir = noclose = 1;
59	pidfile = user = NULL;
60	while ((ch = getopt(argc, argv, "-cfp:u:")) != -1) {
61		switch (ch) {
62		case 'c':
63			nochdir = 0;
64			break;
65		case 'f':
66			noclose = 0;
67			break;
68		case 'p':
69			pidfile = optarg;
70			break;
71		case 'u':
72			user = optarg;
73			break;
74		default:
75			usage();
76		}
77	}
78	argc -= optind;
79	argv += optind;
80
81	if (argc == 0)
82		usage();
83
84	pfh = NULL;
85	/*
86	 * Try to open the pidfile before calling daemon(3),
87	 * to be able to report the error intelligently
88	 */
89	if (pidfile != NULL) {
90		pfh = pidfile_open(pidfile, 0600, &otherpid);
91		if (pfh == NULL) {
92			if (errno == EEXIST) {
93				errx(3, "process already running, pid: %d",
94				    otherpid);
95			}
96			err(2, "pidfile ``%s''", pidfile);
97		}
98	}
99
100	if (daemon(nochdir, noclose) == -1)
101		err(1, NULL);
102
103	pid = 0;
104	if (pidfile != NULL) {
105		/*
106		 * Spawn a child to exec the command, so in the parent
107		 * we could wait for it to exit and remove pidfile.
108		 */
109		pid = fork();
110		if (pid == -1) {
111			pidfile_remove(pfh);
112			err(1, "fork");
113		}
114	}
115	if (pid == 0) {
116		/* Now that we are the child, write out the pid. */
117		pidfile_write(pfh);
118
119		if (user != NULL)
120			restrict_process(user);
121
122		execvp(argv[0], argv);
123
124		/*
125		 * execvp() failed -- report the error. The child is
126		 * now running, so the exit status doesn't matter.
127		 */
128		err(1, "%s", argv[0]);
129	}
130	setproctitle("%s[%d]", argv[0], pid);
131	wait_child(pid);
132	pidfile_remove(pfh);
133	exit(0); /* Exit status does not matter. */
134}
135
136static void
137restrict_process(const char *user)
138{
139	struct passwd *pw = NULL;
140
141	pw = getpwnam(user);
142	if (pw == NULL)
143		errx(1, "unknown user: %s", user);
144
145	if (setusercontext(NULL, pw, pw->pw_uid, LOGIN_SETALL) != 0)
146		errx(1, "failed to set user environment");
147}
148
149static void
150wait_child(pid_t pid)
151{
152	int status;
153
154	while (waitpid(pid, &status, 0) == -1) {
155		if (errno != EINTR) {
156			warn("waitpid");
157			break;
158		}
159	}
160}
161
162static void
163usage(void)
164{
165	(void)fprintf(stderr,
166	    "usage: daemon [-cf] [-p pidfile] [-u user] command "
167		"arguments ...\n");
168	exit(1);
169}
170