release/src/router/busybox/miscutils/crontab.c

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