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//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(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