busybox/miscutils/crontab.c

/* vi: set sw=4 ts=4: */
/*
 * CRONTAB
 *
 * usually setuid root, -c option only works if getuid() == geteuid()
 *
 * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
 * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "libbb.h"

#ifndef CRONTABS
#define CRONTABS        "/var/spool/cron/crontabs"
#endif
#ifndef CRONUPDATE
#define CRONUPDATE      "cron.update"
#endif

static void change_user(const struct passwd *pas)
{
	xsetenv("USER", pas->pw_name);
	xsetenv("HOME", pas->pw_dir);
	xsetenv("SHELL", DEFAULT_SHELL);

	/* initgroups, setgid, setuid */
	change_identity(pas);

	if (chdir(pas->pw_dir) < 0) {
		bb_perror_msg("chdir(%s) by %s failed",
				pas->pw_dir, pas->pw_name);
		xchdir("/tmp");
	}
}

static void edit_file(const struct passwd *pas, const char *file)
{
	const char *ptr;
	int pid = vfork();

	if (pid < 0) /* failure */
		bb_perror_msg_and_die("vfork");
	if (pid) { /* parent */
		wait4pid(pid);
		return;
	}

	/* CHILD - change user and run editor */
	change_user(pas);
	ptr = getenv("VISUAL");
	if (!ptr) {
		ptr = getenv("EDITOR");
		if (!ptr)
			ptr = "vi";
	}

	BB_EXECLP(ptr, ptr, file, NULL);
	bb_perror_msg_and_die("exec %s", ptr);
}

static int open_as_user(const struct passwd *pas, const char *file)
{
	pid_t pid;
	char c;

	pid = vfork();
	if (pid < 0) /* ERROR */
		bb_perror_msg_and_die("vfork");
	if (pid) { /* PARENT */
		if (wait4pid(pid) == 0) {
			/* exitcode 0: child says it can read */
			return open(file, O_RDONLY);
		}
		return -1;
	}

	/* CHILD */
	/* initgroups, setgid, setuid */
	change_identity(pas);
	/* We just try to read one byte. If it works, file is readable
	 * under this user. We signal that by exiting with 0. */
	_exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0);
}

int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int crontab_main(int argc UNUSED_PARAM, char **argv)
{
	const struct passwd *pas;
	const char *crontab_dir = CRONTABS;
	char *tmp_fname;
	char *new_fname;
	char *user_name;  /* -u USER */
	int fd;
	int src_fd;
	int opt_ler;

	/* file [opts]     Replace crontab from file
	 * - [opts]        Replace crontab from stdin
	 * -u user         User
	 * -c dir          Crontab directory
	 * -l              List crontab for user
	 * -e              Edit crontab for user
	 * -r              Delete crontab for user
	 * bbox also supports -d == -r, but most other crontab
	 * implementations do not. Deprecated.
	 */
	enum {
		OPT_u = (1 << 0),
		OPT_c = (1 << 1),
		OPT_l = (1 << 2),
		OPT_e = (1 << 3),
		OPT_r = (1 << 4),
		OPT_ler = OPT_l + OPT_e + OPT_r,
	};

	opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
	opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
	argv += optind;

	if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
		/* run by non-root? */
		if (opt_ler & (OPT_u|OPT_c))
			bb_error_msg_and_die("only root can use -c or -u");
	}

	if (opt_ler & OPT_u) {
		pas = getpwnam(user_name);
		if (!pas)
			bb_error_msg_and_die("user %s is not known", user_name);
	} else {
/* XXX: xgetpwuid */
		uid_t my_uid = getuid();
		pas = getpwuid(my_uid);
		if (!pas)
			bb_perror_msg_and_die("unknown uid %d", (int)my_uid);
	}

#define user_name DONT_USE_ME_BEYOND_THIS_POINT

	/* From now on, keep only -l, -e, -r bits */
	opt_ler &= OPT_ler;
	if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
		bb_show_usage();

	/* Read replacement file under user's UID/GID/group vector */
	src_fd = STDIN_FILENO;
	if (!opt_ler) { /* Replace? */
		if (!argv[0])
			bb_show_usage();
		if (NOT_LONE_DASH(argv[0])) {
			src_fd = open_as_user(pas, argv[0]);
			if (src_fd < 0)
				bb_error_msg_and_die("user %s cannot read %s",
						pas->pw_name, argv[0]);
		}
	}

	/* cd to our crontab directory */
	xchdir(crontab_dir);

	tmp_fname = NULL;

	/* Handle requested operation */
	switch (opt_ler) {

	default: /* case OPT_r: Delete */
		unlink(pas->pw_name);
		break;

	case OPT_l: /* List */
		{
			char *args[2] = { pas->pw_name, NULL };
			return bb_cat(args);
			/* list exits,
			 * the rest go play with cron update file */
		}

	case OPT_e: /* Edit */
		tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
		/* No O_EXCL: we don't want to be stuck if earlier crontabs
		 * were killed, leaving stale temp file behind */
		src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
		fchown(src_fd, pas->pw_uid, pas->pw_gid);
		fd = open(pas->pw_name, O_RDONLY);
		if (fd >= 0) {
			bb_copyfd_eof(fd, src_fd);
			close(fd);
			xlseek(src_fd, 0, SEEK_SET);
		}
		close_on_exec_on(src_fd); /* don't want editor to see this fd */
		edit_file(pas, tmp_fname);
		/* fall through */

	case 0: /* Replace (no -l, -e, or -r were given) */
		new_fname = xasprintf("%s.new", pas->pw_name);
		fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
		if (fd >= 0) {
			bb_copyfd_eof(src_fd, fd);
			close(fd);
			xrename(new_fname, pas->pw_name);
		} else {
			bb_error_msg("cannot create %s/%s",
					crontab_dir, new_fname);
		}
		if (tmp_fname)
			unlink(tmp_fname);
		/*free(tmp_fname);*/
		/*free(new_fname);*/

	} /* switch */

	/* Bump notification file.  Handle window where crond picks file up
	 * before we can write our entry out.
	 */
	while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
		struct stat st;

		fdprintf(fd, "%s\n", pas->pw_name);
		if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
			/*close(fd);*/
			break;
		}
		/* st.st_nlink == 0:
		 * file was deleted, maybe crond missed our notification */
		close(fd);
		/* loop */
	}
	if (fd < 0) {
		bb_error_msg("cannot append to %s/%s",
				crontab_dir, CRONUPDATE);
	}
	return 0;
}
1	/* vi: set sw=4 ts=4: */
2	/*
3	* CRONTAB
4	*
5	* usually setuid root, -c option only works if getuid() == geteuid()
6	*
7	* Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
8	* Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
9	*
10	* Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
11	*/
12
13	#include "libbb.h"
14
15	#ifndef CRONTABS
16	#define CRONTABS "/var/spool/cron/crontabs"
17	#endif
18	#ifndef CRONUPDATE
19	#define CRONUPDATE "cron.update"
20	#endif
21
22	static void change_user(const struct passwd *pas)
23	{
24	xsetenv("USER", pas->pw_name);
25	xsetenv("HOME", pas->pw_dir);
26	xsetenv("SHELL", DEFAULT_SHELL);
27
28	/* initgroups, setgid, setuid */
29	change_identity(pas);
30
31	if (chdir(pas->pw_dir) < 0) {
32	bb_perror_msg("chdir(%s) by %s failed",
33	pas->pw_dir, pas->pw_name);
34	xchdir("/tmp");
35	}
36	}
37
38	static void edit_file(const struct passwd pas, const char file)
39	{
40	const char *ptr;
41	int pid = vfork();
42
43	if (pid < 0) /* failure */
44	bb_perror_msg_and_die("vfork");
45	if (pid) { /* parent */
46	wait4pid(pid);
47	return;
48	}
49
50	/* CHILD - change user and run editor */
51	change_user(pas);
52	ptr = getenv("VISUAL");
53	if (!ptr) {
54	ptr = getenv("EDITOR");
55	if (!ptr)
56	ptr = "vi";
57	}
58
59	BB_EXECLP(ptr, ptr, file, NULL);
60	bb_perror_msg_and_die("exec %s", ptr);
61	}
62
63	static int open_as_user(const struct passwd pas, const char file)
64	{
65	pid_t pid;
66	char c;
67
68	pid = vfork();
69	if (pid < 0) /* ERROR */
70	bb_perror_msg_and_die("vfork");
71	if (pid) { /* PARENT */
72	if (wait4pid(pid) == 0) {
73	/* exitcode 0: child says it can read */
74	return open(file, O_RDONLY);
75	}
76	return -1;
77	}
78
79	/* CHILD */
80	/* initgroups, setgid, setuid */
81	change_identity(pas);
82	/* We just try to read one byte. If it works, file is readable
83	* under this user. We signal that by exiting with 0. */
84	_exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0);
85	}
86
87	int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
88	int crontab_main(int argc UNUSED_PARAM, char **argv)
89	{
90	const struct passwd *pas;
91	const char *crontab_dir = CRONTABS;
92	char *tmp_fname;
93	char *new_fname;
94	char user_name; / -u USER */
95	int fd;
96	int src_fd;
97	int opt_ler;
98
99	/* file [opts] Replace crontab from file
100	* - [opts] Replace crontab from stdin
101	* -u user User
102	* -c dir Crontab directory
103	* -l List crontab for user
104	* -e Edit crontab for user
105	* -r Delete crontab for user
106	* bbox also supports -d == -r, but most other crontab
107	* implementations do not. Deprecated.
108	*/
109	enum {
110	OPT_u = (1 << 0),
111	OPT_c = (1 << 1),
112	OPT_l = (1 << 2),
113	OPT_e = (1 << 3),
114	OPT_r = (1 << 4),
115	OPT_ler = OPT_l + OPT_e + OPT_r,
116	};
117
118	opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
119	opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
120	argv += optind;
121
122	if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
123	/* run by non-root? */
124	if (opt_ler & (OPT_u\|OPT_c))
125	bb_error_msg_and_die("only root can use -c or -u");
126	}
127
128	if (opt_ler & OPT_u) {
129	pas = getpwnam(user_name);
130	if (!pas)
131	bb_error_msg_and_die("user %s is not known", user_name);
132	} else {
133	/* XXX: xgetpwuid */
134	uid_t my_uid = getuid();
135	pas = getpwuid(my_uid);
136	if (!pas)
137	bb_perror_msg_and_die("unknown uid %d", (int)my_uid);
138	}
139
140	#define user_name DONT_USE_ME_BEYOND_THIS_POINT
141
142	/* From now on, keep only -l, -e, -r bits */
143	opt_ler &= OPT_ler;
144	if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
145	bb_show_usage();
146
147	/* Read replacement file under user's UID/GID/group vector */
148	src_fd = STDIN_FILENO;
149	if (!opt_ler) { /* Replace? */
150	if (!argv[0])
151	bb_show_usage();
152	if (NOT_LONE_DASH(argv[0])) {
153	src_fd = open_as_user(pas, argv[0]);
154	if (src_fd < 0)
155	bb_error_msg_and_die("user %s cannot read %s",
156	pas->pw_name, argv[0]);
157	}
158	}
159
160	/* cd to our crontab directory */
161	xchdir(crontab_dir);
162
163	tmp_fname = NULL;
164
165	/* Handle requested operation */
166	switch (opt_ler) {
167
168	default: /* case OPT_r: Delete */
169	unlink(pas->pw_name);
170	break;
171
172	case OPT_l: /* List */
173	{
174	char *args[2] = { pas->pw_name, NULL };
175	return bb_cat(args);
176	/* list exits,
177	* the rest go play with cron update file */
178	}
179
180	case OPT_e: /* Edit */
181	tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
182	/* No O_EXCL: we don't want to be stuck if earlier crontabs
183	* were killed, leaving stale temp file behind */
184	src_fd = xopen3(tmp_fname, O_RDWR\|O_CREAT\|O_TRUNC, 0600);
185	fchown(src_fd, pas->pw_uid, pas->pw_gid);
186	fd = open(pas->pw_name, O_RDONLY);
187	if (fd >= 0) {
188	bb_copyfd_eof(fd, src_fd);
189	close(fd);
190	xlseek(src_fd, 0, SEEK_SET);
191	}
192	close_on_exec_on(src_fd); /* don't want editor to see this fd */
193	edit_file(pas, tmp_fname);
194	/* fall through */
195
196	case 0: /* Replace (no -l, -e, or -r were given) */
197	new_fname = xasprintf("%s.new", pas->pw_name);
198	fd = open(new_fname, O_WRONLY\|O_CREAT\|O_TRUNC\|O_APPEND, 0600);
199	if (fd >= 0) {
200	bb_copyfd_eof(src_fd, fd);
201	close(fd);
202	xrename(new_fname, pas->pw_name);
203	} else {
204	bb_error_msg("cannot create %s/%s",
205	crontab_dir, new_fname);
206	}
207	if (tmp_fname)
208	unlink(tmp_fname);
209	/free(tmp_fname);/
210	/free(new_fname);/
211
212	} /* switch */
213
214	/* Bump notification file. Handle window where crond picks file up
215	* before we can write our entry out.
216	*/
217	while ((fd = open(CRONUPDATE, O_WRONLY\|O_CREAT\|O_APPEND, 0600)) >= 0) {
218	struct stat st;
219
220	fdprintf(fd, "%s\n", pas->pw_name);
221	if (fstat(fd, &st) != 0 \|\| st.st_nlink != 0) {
222	/close(fd);/
223	break;
224	}
225	/* st.st_nlink == 0:
226	* file was deleted, maybe crond missed our notification */
227	close(fd);
228	/* loop */
229	}
230	if (fd < 0) {
231	bb_error_msg("cannot append to %s/%s",
232	crontab_dir, CRONUPDATE);
233	}
234	return 0;
235	}