mirror of
https://github.com/sheumann/hush.git
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235 lines
5.6 KiB
C
235 lines
5.6 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* CRONTAB
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*
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* usually setuid root, -c option only works if getuid() == geteuid()
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*
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* Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
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* Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
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*
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* Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
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*/
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#include "libbb.h"
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#ifndef CRONTABS
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#define CRONTABS "/var/spool/cron/crontabs"
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#endif
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#ifndef CRONUPDATE
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#define CRONUPDATE "cron.update"
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#endif
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static void change_user(const struct passwd *pas)
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{
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setenv("USER", pas->pw_name, 1);
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setenv("HOME", pas->pw_dir, 1);
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setenv("SHELL", DEFAULT_SHELL, 1);
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/* initgroups, setgid, setuid */
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change_identity(pas);
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if (chdir(pas->pw_dir) < 0) {
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bb_perror_msg("chdir(%s) by %s failed",
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pas->pw_dir, pas->pw_name);
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xchdir("/tmp");
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}
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}
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static void edit_file(const struct passwd *pas, const char *file)
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{
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const char *ptr;
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int pid = vfork();
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if (pid < 0) /* failure */
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bb_perror_msg_and_die("vfork");
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if (pid) { /* parent */
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wait4pid(pid);
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return;
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}
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/* CHILD - change user and run editor */
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change_user(pas);
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ptr = getenv("VISUAL");
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if (!ptr) {
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ptr = getenv("EDITOR");
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if (!ptr)
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ptr = "vi";
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}
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BB_EXECLP(ptr, ptr, file, NULL);
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bb_perror_msg_and_die("exec %s", ptr);
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}
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static int open_as_user(const struct passwd *pas, const char *file)
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{
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pid_t pid;
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char c;
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pid = vfork();
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if (pid < 0) /* ERROR */
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bb_perror_msg_and_die("vfork");
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if (pid) { /* PARENT */
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if (wait4pid(pid) == 0) {
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/* exitcode 0: child says it can read */
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return open(file, O_RDONLY);
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}
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return -1;
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}
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/* CHILD */
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/* initgroups, setgid, setuid */
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change_identity(pas);
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/* We just try to read one byte. If it works, file is readable
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* under this user. We signal that by exiting with 0. */
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_exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0);
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}
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int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int crontab_main(int argc UNUSED_PARAM, char **argv)
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{
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const struct passwd *pas;
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const char *crontab_dir = CRONTABS;
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char *tmp_fname;
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char *new_fname;
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char *user_name; /* -u USER */
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int fd;
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int opt_ler;
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/* file [opts] Replace crontab from file
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* - [opts] Replace crontab from stdin
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* -u user User
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* -c dir Crontab directory
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* -l List crontab for user
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* -e Edit crontab for user
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* -r Delete crontab for user
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* bbox also supports -d == -r, but most other crontab
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* implementations do not. Deprecated.
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*/
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enum {
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OPT_u = (1 << 0),
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OPT_c = (1 << 1),
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OPT_l = (1 << 2),
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OPT_e = (1 << 3),
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OPT_r = (1 << 4),
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OPT_ler = OPT_l + OPT_e + OPT_r,
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};
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opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
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opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
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argv += optind;
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if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
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/* run by non-root? */
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if (opt_ler & (OPT_u|OPT_c))
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bb_error_msg_and_die("only root can use -c or -u");
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}
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if (opt_ler & OPT_u) {
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pas = getpwnam(user_name);
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if (!pas)
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bb_error_msg_and_die("user %s is not known", user_name);
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} else {
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/* XXX: xgetpwuid */
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uid_t my_uid = getuid();
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pas = getpwuid(my_uid);
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if (!pas)
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bb_perror_msg_and_die("unknown uid %d", (int)my_uid);
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}
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#define user_name DONT_USE_ME_BEYOND_THIS_POINT
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/* From now on, keep only -l, -e, -r bits */
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opt_ler &= OPT_ler;
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if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
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bb_show_usage();
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/* Read replacement file under user's UID/GID/group vector */
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if (!opt_ler) { /* Replace? */
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if (!argv[0])
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bb_show_usage();
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if (NOT_LONE_DASH(argv[0])) {
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fd = open_as_user(pas, argv[0]);
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if (fd < 0)
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bb_error_msg_and_die("user %s cannot read %s",
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pas->pw_name, argv[0]);
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xmove_fd(fd, STDIN_FILENO);
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}
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}
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/* cd to our crontab directory */
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xchdir(crontab_dir);
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tmp_fname = NULL;
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/* Handle requested operation */
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switch (opt_ler) {
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default: /* case OPT_r: Delete */
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unlink(pas->pw_name);
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break;
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case OPT_l: /* List */
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{
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char *args[2] = { pas->pw_name, NULL };
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return bb_cat(args);
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/* list exits,
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* the rest go play with cron update file */
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}
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case OPT_e: /* Edit */
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tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
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/* No O_EXCL: we don't want to be stuck if earlier crontabs
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* were killed, leaving stale temp file behind */
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fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
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xmove_fd(fd, STDIN_FILENO);
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fchown(STDIN_FILENO, pas->pw_uid, pas->pw_gid);
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fd = open(pas->pw_name, O_RDONLY);
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if (fd >= 0) {
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bb_copyfd_eof(fd, STDIN_FILENO);
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close(fd);
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}
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edit_file(pas, tmp_fname);
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xlseek(STDIN_FILENO, 0, SEEK_SET);
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/* fall through */
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case 0: /* Replace (no -l, -e, or -r were given) */
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new_fname = xasprintf("%s.new", pas->pw_name);
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fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
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if (fd >= 0) {
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bb_copyfd_eof(STDIN_FILENO, fd);
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close(fd);
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xrename(new_fname, pas->pw_name);
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} else {
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bb_error_msg("cannot create %s/%s",
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crontab_dir, new_fname);
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}
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if (tmp_fname)
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unlink(tmp_fname);
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/*free(tmp_fname);*/
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/*free(new_fname);*/
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} /* switch */
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/* Bump notification file. Handle window where crond picks file up
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* before we can write our entry out.
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*/
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while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
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struct stat st;
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fdprintf(fd, "%s\n", pas->pw_name);
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if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
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/*close(fd);*/
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break;
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}
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/* st.st_nlink == 0:
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* file was deleted, maybe crond missed our notification */
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close(fd);
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/* loop */
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}
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if (fd < 0) {
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bb_error_msg("cannot append to %s/%s",
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crontab_dir, CRONUPDATE);
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}
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return 0;
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}
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