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path: root/miscutils/crontab.c (plain)
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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 GPLv2 or later, see file LICENSE in this source tree.
11 */
12//config:config CRONTAB
13//config: bool "crontab"
14//config: default y
15//config: help
16//config: Crontab manipulates the crontab for a particular user. Only
17//config: the superuser may specify a different user and/or crontab directory.
18//config: Note that Busybox binary must be setuid root for this applet to
19//config: work properly.
20
21/* Needs to be run by root or be suid root - needs to change /var/spool/cron* files: */
22//applet:IF_CRONTAB(APPLET(crontab, BB_DIR_USR_BIN, BB_SUID_REQUIRE))
23
24//kbuild:lib-$(CONFIG_CRONTAB) += crontab.o
25
26//usage:#define crontab_trivial_usage
27//usage: "[-c DIR] [-u USER] [-ler]|[FILE]"
28//usage:#define crontab_full_usage "\n\n"
29//usage: " -c Crontab directory"
30//usage: "\n -u User"
31//usage: "\n -l List crontab"
32//usage: "\n -e Edit crontab"
33//usage: "\n -r Delete crontab"
34//usage: "\n FILE Replace crontab by FILE ('-': stdin)"
35
36#include "libbb.h"
37
38#define CRONTABS CONFIG_FEATURE_CROND_DIR "/crontabs"
39#ifndef CRONUPDATE
40#define CRONUPDATE "cron.update"
41#endif
42
43static void edit_file(const struct passwd *pas, const char *file)
44{
45 const char *ptr;
46 pid_t pid;
47
48 pid = xvfork();
49 if (pid) { /* parent */
50 wait4pid(pid);
51 return;
52 }
53
54 /* CHILD - change user and run editor */
55 /* initgroups, setgid, setuid */
56 change_identity(pas);
57 setup_environment(pas->pw_shell,
58 SETUP_ENV_CHANGEENV | SETUP_ENV_TO_TMP,
59 pas);
60 ptr = getenv("VISUAL");
61 if (!ptr) {
62 ptr = getenv("EDITOR");
63 if (!ptr)
64 ptr = "vi";
65 }
66
67 BB_EXECLP(ptr, ptr, file, NULL);
68 bb_perror_msg_and_die("can't execute '%s'", ptr);
69}
70
71int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
72int crontab_main(int argc UNUSED_PARAM, char **argv)
73{
74 const struct passwd *pas;
75 const char *crontab_dir = CRONTABS;
76 char *tmp_fname;
77 char *new_fname;
78 char *user_name; /* -u USER */
79 int fd;
80 int src_fd;
81 int opt_ler;
82
83 /* file [opts] Replace crontab from file
84 * - [opts] Replace crontab from stdin
85 * -u user User
86 * -c dir Crontab directory
87 * -l List crontab for user
88 * -e Edit crontab for user
89 * -r Delete crontab for user
90 * bbox also supports -d == -r, but most other crontab
91 * implementations do not. Deprecated.
92 */
93 enum {
94 OPT_u = (1 << 0),
95 OPT_c = (1 << 1),
96 OPT_l = (1 << 2),
97 OPT_e = (1 << 3),
98 OPT_r = (1 << 4),
99 OPT_ler = OPT_l + OPT_e + OPT_r,
100 };
101
102 opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
103 opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
104 argv += optind;
105
106 if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
107 /* Run by non-root */
108 if (opt_ler & (OPT_u|OPT_c))
109 bb_error_msg_and_die("%s", bb_msg_you_must_be_root);
110 }
111
112 if (opt_ler & OPT_u) {
113 pas = xgetpwnam(user_name);
114 } else {
115 pas = xgetpwuid(getuid());
116 }
117
118#define user_name DONT_USE_ME_BEYOND_THIS_POINT
119
120 /* From now on, keep only -l, -e, -r bits */
121 opt_ler &= OPT_ler;
122 if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
123 bb_show_usage();
124
125 /* Read replacement file under user's UID/GID/group vector */
126 src_fd = STDIN_FILENO;
127 if (!opt_ler) { /* Replace? */
128 if (!argv[0])
129 bb_show_usage();
130 if (NOT_LONE_DASH(argv[0])) {
131 src_fd = xopen_as_uid_gid(argv[0], O_RDONLY, pas->pw_uid, pas->pw_gid);
132 }
133 }
134
135 /* cd to our crontab directory */
136 xchdir(crontab_dir);
137
138 tmp_fname = NULL;
139
140 /* Handle requested operation */
141 switch (opt_ler) {
142
143 default: /* case OPT_r: Delete */
144 unlink(pas->pw_name);
145 break;
146
147 case OPT_l: /* List */
148 {
149 char *args[2] = { pas->pw_name, NULL };
150 return bb_cat(args);
151 /* list exits,
152 * the rest go play with cron update file */
153 }
154
155 case OPT_e: /* Edit */
156 tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
157 /* No O_EXCL: we don't want to be stuck if earlier crontabs
158 * were killed, leaving stale temp file behind */
159 src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
160 fchown(src_fd, pas->pw_uid, pas->pw_gid);
161 fd = open(pas->pw_name, O_RDONLY);
162 if (fd >= 0) {
163 bb_copyfd_eof(fd, src_fd);
164 close(fd);
165 xlseek(src_fd, 0, SEEK_SET);
166 }
167 close_on_exec_on(src_fd); /* don't want editor to see this fd */
168 edit_file(pas, tmp_fname);
169 /* fall through */
170
171 case 0: /* Replace (no -l, -e, or -r were given) */
172 new_fname = xasprintf("%s.new", pas->pw_name);
173 fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
174 if (fd >= 0) {
175 bb_copyfd_eof(src_fd, fd);
176 close(fd);
177 xrename(new_fname, pas->pw_name);
178 } else {
179 bb_error_msg("can't create %s/%s",
180 crontab_dir, new_fname);
181 }
182 if (tmp_fname)
183 unlink(tmp_fname);
184 /*free(tmp_fname);*/
185 /*free(new_fname);*/
186 } /* switch */
187
188 /* Bump notification file. Handle window where crond picks file up
189 * before we can write our entry out.
190 */
191 while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
192 struct stat st;
193
194 fdprintf(fd, "%s\n", pas->pw_name);
195 if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
196 /*close(fd);*/
197 break;
198 }
199 /* st.st_nlink == 0:
200 * file was deleted, maybe crond missed our notification */
201 close(fd);
202 /* loop */
203 }
204 if (fd < 0) {
205 bb_error_msg("can't append to %s/%s",
206 crontab_dir, CRONUPDATE);
207 }
208 return 0;
209}
210
generated by cgit at 2024-05-15 12:03:19 (GMT)