[3320] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * CRONTAB
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| 4 | *
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| 5 | * usually setuid root, -c option only works if getuid() == geteuid()
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| 6 | *
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| 7 | * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
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| 8 | * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
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| 9 | *
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| 10 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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| 11 | */
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| 12 |
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| 13 | #include "libbb.h"
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| 14 |
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| 15 | #define CRONTABS CONFIG_FEATURE_CROND_DIR "/crontabs"
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| 16 | #ifndef CRONUPDATE
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| 17 | #define CRONUPDATE "cron.update"
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| 18 | #endif
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| 19 |
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| 20 | static void edit_file(const struct passwd *pas, const char *file)
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| 21 | {
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| 22 | const char *ptr;
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| 23 | int pid = xvfork();
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| 24 |
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| 25 | if (pid) { /* parent */
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| 26 | wait4pid(pid);
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| 27 | return;
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| 28 | }
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| 29 |
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| 30 | /* CHILD - change user and run editor */
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| 31 | /* initgroups, setgid, setuid */
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| 32 | change_identity(pas);
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| 33 | setup_environment(DEFAULT_SHELL,
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| 34 | SETUP_ENV_CHANGEENV | SETUP_ENV_TO_TMP,
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| 35 | pas);
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| 36 | ptr = getenv("VISUAL");
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| 37 | if (!ptr) {
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| 38 | ptr = getenv("EDITOR");
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| 39 | if (!ptr)
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| 40 | ptr = "vi";
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| 41 | }
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| 42 |
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| 43 | BB_EXECLP(ptr, ptr, file, NULL);
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| 44 | bb_perror_msg_and_die("exec %s", ptr);
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| 45 | }
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| 46 |
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| 47 | static int open_as_user(const struct passwd *pas, const char *file)
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| 48 | {
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| 49 | pid_t pid;
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| 50 | char c;
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| 51 |
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| 52 | pid = xvfork();
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| 53 | if (pid) { /* PARENT */
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| 54 | if (wait4pid(pid) == 0) {
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| 55 | /* exitcode 0: child says it can read */
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| 56 | return open(file, O_RDONLY);
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| 57 | }
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| 58 | return -1;
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| 59 | }
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| 60 |
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| 61 | /* CHILD */
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| 62 | /* initgroups, setgid, setuid */
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| 63 | change_identity(pas);
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| 64 | /* We just try to read one byte. If it works, file is readable
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| 65 | * under this user. We signal that by exiting with 0. */
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| 66 | _exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0);
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| 67 | }
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| 68 |
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| 69 | int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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| 70 | int crontab_main(int argc UNUSED_PARAM, char **argv)
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| 71 | {
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| 72 | const struct passwd *pas;
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| 73 | const char *crontab_dir = CRONTABS;
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| 74 | char *tmp_fname;
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| 75 | char *new_fname;
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| 76 | char *user_name; /* -u USER */
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| 77 | int fd;
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| 78 | int src_fd;
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| 79 | int opt_ler;
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| 80 |
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| 81 | /* file [opts] Replace crontab from file
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| 82 | * - [opts] Replace crontab from stdin
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| 83 | * -u user User
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| 84 | * -c dir Crontab directory
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| 85 | * -l List crontab for user
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| 86 | * -e Edit crontab for user
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| 87 | * -r Delete crontab for user
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| 88 | * bbox also supports -d == -r, but most other crontab
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| 89 | * implementations do not. Deprecated.
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| 90 | */
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| 91 | enum {
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| 92 | OPT_u = (1 << 0),
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| 93 | OPT_c = (1 << 1),
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| 94 | OPT_l = (1 << 2),
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| 95 | OPT_e = (1 << 3),
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| 96 | OPT_r = (1 << 4),
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| 97 | OPT_ler = OPT_l + OPT_e + OPT_r,
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| 98 | };
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| 99 |
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| 100 | opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
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| 101 | opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
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| 102 | argv += optind;
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| 103 |
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| 104 | if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
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| 105 | /* Run by non-root */
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| 106 | if (opt_ler & (OPT_u|OPT_c))
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| 107 | bb_error_msg_and_die(bb_msg_you_must_be_root);
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| 108 | }
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| 109 |
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| 110 | if (opt_ler & OPT_u) {
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| 111 | pas = xgetpwnam(user_name);
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| 112 | } else {
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| 113 | pas = xgetpwuid(getuid());
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| 114 | }
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| 115 |
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| 116 | #define user_name DONT_USE_ME_BEYOND_THIS_POINT
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| 117 |
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| 118 | /* From now on, keep only -l, -e, -r bits */
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| 119 | opt_ler &= OPT_ler;
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| 120 | if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
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| 121 | bb_show_usage();
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| 122 |
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| 123 | /* Read replacement file under user's UID/GID/group vector */
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| 124 | src_fd = STDIN_FILENO;
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| 125 | if (!opt_ler) { /* Replace? */
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| 126 | if (!argv[0])
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| 127 | bb_show_usage();
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| 128 | if (NOT_LONE_DASH(argv[0])) {
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| 129 | src_fd = open_as_user(pas, argv[0]);
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| 130 | if (src_fd < 0)
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| 131 | bb_error_msg_and_die("user %s cannot read %s",
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| 132 | pas->pw_name, argv[0]);
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| 133 | }
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| 134 | }
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| 135 |
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| 136 | /* cd to our crontab directory */
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| 137 | xchdir(crontab_dir);
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| 138 |
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| 139 | tmp_fname = NULL;
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| 140 |
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| 141 | /* Handle requested operation */
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| 142 | switch (opt_ler) {
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| 143 |
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| 144 | default: /* case OPT_r: Delete */
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| 145 | unlink(pas->pw_name);
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| 146 | break;
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| 147 |
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| 148 | case OPT_l: /* List */
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| 149 | {
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| 150 | char *args[2] = { pas->pw_name, NULL };
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| 151 | return bb_cat(args);
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| 152 | /* list exits,
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| 153 | * the rest go play with cron update file */
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| 154 | }
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| 155 |
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| 156 | case OPT_e: /* Edit */
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| 157 | tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
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| 158 | /* No O_EXCL: we don't want to be stuck if earlier crontabs
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| 159 | * were killed, leaving stale temp file behind */
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| 160 | src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
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| 161 | fchown(src_fd, pas->pw_uid, pas->pw_gid);
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| 162 | fd = open(pas->pw_name, O_RDONLY);
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| 163 | if (fd >= 0) {
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| 164 | bb_copyfd_eof(fd, src_fd);
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| 165 | close(fd);
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| 166 | xlseek(src_fd, 0, SEEK_SET);
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| 167 | }
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| 168 | close_on_exec_on(src_fd); /* don't want editor to see this fd */
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| 169 | edit_file(pas, tmp_fname);
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| 170 | /* fall through */
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| 171 |
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| 172 | case 0: /* Replace (no -l, -e, or -r were given) */
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| 173 | new_fname = xasprintf("%s.new", pas->pw_name);
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| 174 | fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
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| 175 | if (fd >= 0) {
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| 176 | bb_copyfd_eof(src_fd, fd);
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| 177 | close(fd);
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| 178 | xrename(new_fname, pas->pw_name);
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| 179 | } else {
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| 180 | bb_error_msg("can't create %s/%s",
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| 181 | crontab_dir, new_fname);
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| 182 | }
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| 183 | if (tmp_fname)
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| 184 | unlink(tmp_fname);
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| 185 | /*free(tmp_fname);*/
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| 186 | /*free(new_fname);*/
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| 187 |
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| 188 | } /* switch */
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| 189 |
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| 190 | /* Bump notification file. Handle window where crond picks file up
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| 191 | * before we can write our entry out.
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| 192 | */
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| 193 | while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
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| 194 | struct stat st;
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| 195 |
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| 196 | fdprintf(fd, "%s\n", pas->pw_name);
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| 197 | if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
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| 198 | /*close(fd);*/
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| 199 | break;
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| 200 | }
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| 201 | /* st.st_nlink == 0:
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| 202 | * file was deleted, maybe crond missed our notification */
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| 203 | close(fd);
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| 204 | /* loop */
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| 205 | }
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| 206 | if (fd < 0) {
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| 207 | bb_error_msg("can't append to %s/%s",
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| 208 | crontab_dir, CRONUPDATE);
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| 209 | }
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| 210 | return 0;
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| 211 | }
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