LXR 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
  30static 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
  58int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  59int 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        } /* switch */
 174
 175        /* Bump notification file.  Handle window where crond picks file up
 176         * before we can write our entry out.
 177         */
 178        while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
 179                struct stat st;
 180
 181                fdprintf(fd, "%s\n", pas->pw_name);
 182                if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
 183                        /*close(fd);*/
 184                        break;
 185                }
 186                /* st.st_nlink == 0:
 187                 * file was deleted, maybe crond missed our notification */
 188                close(fd);
 189                /* loop */
 190        }
 191        if (fd < 0) {
 192                bb_error_msg("can't append to %s/%s",
 193                                crontab_dir, CRONUPDATE);
 194        }
 195        return 0;
 196}
 197