daemon.c revision 231911 
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 231911 2012-02-19 10:36:29Z trociny $");
33
34#include <sys/param.h>
35#include <sys/wait.h>
36
37#include <err.h>
38#include <errno.h>
39#include <libutil.h>
40#include <login_cap.h>
41#include <pwd.h>
42#include <signal.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include <unistd.h>
46
47static void dummy_sighandler(int);
48static void restrict_process(const char *);
49static int  wait_child(pid_t pid, sigset_t *mask);
50static void usage(void);
51
52int
53main(int argc, char *argv[])
54{
55	struct pidfh *pfh = NULL;
56	sigset_t mask, oldmask;
57	int ch, nochdir, noclose, restart;
58	const char *pidfile, *user;
59	pid_t otherpid, pid;
60
61	nochdir = noclose = 1;
62	restart = 0;
63	pidfile = user = NULL;
64	while ((ch = getopt(argc, argv, "-cfp:ru:")) != -1) {
65		switch (ch) {
66		case 'c':
67			nochdir = 0;
68			break;
69		case 'f':
70			noclose = 0;
71			break;
72		case 'p':
73			pidfile = optarg;
74			break;
75		case 'r':
76			restart = 1;
77			break;
78		case 'u':
79			user = optarg;
80			break;
81		default:
82			usage();
83		}
84	}
85	argc -= optind;
86	argv += optind;
87
88	if (argc == 0)
89		usage();
90
91	pfh = NULL;
92	/*
93	 * Try to open the pidfile before calling daemon(3),
94	 * to be able to report the error intelligently
95	 */
96	if (pidfile != NULL) {
97		pfh = pidfile_open(pidfile, 0600, &otherpid);
98		if (pfh == NULL) {
99			if (errno == EEXIST) {
100				errx(3, "process already running, pid: %d",
101				    otherpid);
102			}
103			err(2, "pidfile ``%s''", pidfile);
104		}
105	}
106
107	if (daemon(nochdir, noclose) == -1)
108		err(1, NULL);
109
110	/*
111	 * If the pidfile or restart option is specified the daemon
112	 * executes the command in a forked process and wait on child
113	 * exit to remove the pidfile or restart the command. Normally
114	 * we don't want the monitoring daemon to be terminated
115	 * leaving the running process and the stale pidfile, so we
116	 * catch SIGTERM and forward it to the children expecting to
117	 * get SIGCHLD eventually.
118	 */
119	pid = -1;
120	if (pidfile != NULL || restart) {
121		/*
122		 * Restore default action for SIGTERM in case the
123		 * parent process decided to ignore it.
124		 */
125		if (signal(SIGTERM, SIG_DFL) == SIG_ERR)
126			err(1, "signal");
127		/*
128		 * Because SIGCHLD is ignored by default, setup dummy handler
129		 * for it, so we can mask it.
130		 */
131		if (signal(SIGCHLD, dummy_sighandler) == SIG_ERR)
132			err(1, "signal");
133		/*
134		 * Block interesting signals.
135		 */
136		sigemptyset(&mask);
137		sigaddset(&mask, SIGTERM);
138		sigaddset(&mask, SIGCHLD);
139		if (sigprocmask(SIG_SETMASK, &mask, &oldmask) == -1)
140			err(1, "sigprocmask");
141restart:
142		/*
143		 * Spawn a child to exec the command, so in the parent
144		 * we could wait for it to exit and remove pidfile.
145		 */
146		pid = fork();
147		if (pid == -1) {
148			pidfile_remove(pfh);
149			err(1, "fork");
150		}
151	}
152	if (pid <= 0) {
153		if (pid == 0) {
154			/* Restore old sigmask in the child. */
155			if (sigprocmask(SIG_SETMASK, &oldmask, NULL) == -1)
156				err(1, "sigprocmask");
157		}
158		/* Now that we are the child, write out the pid. */
159		pidfile_write(pfh);
160
161		if (user != NULL)
162			restrict_process(user);
163
164		execvp(argv[0], argv);
165
166		/*
167		 * execvp() failed -- report the error. The child is
168		 * now running, so the exit status doesn't matter.
169		 */
170		err(1, "%s", argv[0]);
171	}
172	setproctitle("%s[%d]", argv[0], pid);
173	if (wait_child(pid, &mask) == 0 && restart) {
174		sleep(1);
175		goto restart;
176	}
177	pidfile_remove(pfh);
178	exit(0); /* Exit status does not matter. */
179}
180
181static void
182dummy_sighandler(int sig __unused)
183{
184	/* Nothing to do. */
185}
186
187static void
188restrict_process(const char *user)
189{
190	struct passwd *pw = NULL;
191
192	pw = getpwnam(user);
193	if (pw == NULL)
194		errx(1, "unknown user: %s", user);
195
196	if (setusercontext(NULL, pw, pw->pw_uid, LOGIN_SETALL) != 0)
197		errx(1, "failed to set user environment");
198}
199
200static int
201wait_child(pid_t pid, sigset_t *mask)
202{
203	int terminate, signo;
204
205	terminate = 0;
206	for (;;) {
207		if (sigwait(mask, &signo) == -1) {
208			warn("sigwaitinfo");
209			return (-1);
210		}
211		switch (signo) {
212		case SIGCHLD:
213			return (terminate);
214		case SIGTERM:
215			terminate = 1;
216			if (kill(pid, signo) == -1) {
217				warn("kill");
218				return (-1);
219			}
220			continue;
221		default:
222			warnx("sigwaitinfo: invalid signal: %d", signo);
223			return (-1);
224		}
225	}
226}
227
228static void
229usage(void)
230{
231	(void)fprintf(stderr,
232	    "usage: daemon [-cf] [-p pidfile] [-u user] command "
233		"arguments ...\n");
234	exit(1);
235}
236