/* vi: set sw=4 ts=4: */ /* * CRONTAB * * usually setuid root, -c option only works if getuid() == geteuid() * * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com) * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002 * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ //usage:#define crontab_trivial_usage //usage: "[-c DIR] [-u USER] [-ler]|[FILE]" //usage:#define crontab_full_usage "\n\n" //usage: " -c Crontab directory" //usage: "\n -u User" //usage: "\n -l List crontab" //usage: "\n -e Edit crontab" //usage: "\n -r Delete crontab" //usage: "\n FILE Replace crontab by FILE ('-': stdin)" #include "libbb.h" #define CRONTABS CONFIG_FEATURE_CROND_DIR "/crontabs" #ifndef CRONUPDATE #define CRONUPDATE "cron.update" #endif static void edit_file(const struct passwd *pas, const char *file) { const char *ptr; pid_t pid; pid = xvfork(); if (pid) { /* parent */ wait4pid(pid); return; } /* CHILD - change user and run editor */ /* initgroups, setgid, setuid */ change_identity(pas); setup_environment(pas->pw_shell, SETUP_ENV_CHANGEENV | SETUP_ENV_TO_TMP, pas); ptr = getenv("VISUAL"); if (!ptr) { ptr = getenv("EDITOR"); if (!ptr) ptr = "vi"; } BB_EXECLP(ptr, ptr, file, NULL); bb_perror_msg_and_die("can't execute '%s'", ptr); } static int open_as_user(const struct passwd *pas, const char *file) { pid_t pid; char c; pid = xvfork(); if (pid) { /* PARENT */ if (wait4pid(pid) == 0) { /* exitcode 0: child says it can read */ return open(file, O_RDONLY); } return -1; } /* CHILD */ /* initgroups, setgid, setuid */ change_identity(pas); /* We just try to read one byte. If it works, file is readable * under this user. We signal that by exiting with 0. */ _exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0); } int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int crontab_main(int argc UNUSED_PARAM, char **argv) { const struct passwd *pas; const char *crontab_dir = CRONTABS; char *tmp_fname; char *new_fname; char *user_name; /* -u USER */ int fd; int src_fd; int opt_ler; /* file [opts] Replace crontab from file * - [opts] Replace crontab from stdin * -u user User * -c dir Crontab directory * -l List crontab for user * -e Edit crontab for user * -r Delete crontab for user * bbox also supports -d == -r, but most other crontab * implementations do not. Deprecated. */ enum { OPT_u = (1 << 0), OPT_c = (1 << 1), OPT_l = (1 << 2), OPT_e = (1 << 3), OPT_r = (1 << 4), OPT_ler = OPT_l + OPT_e + OPT_r, }; opt_complementary = "?1:dr"; /* max one argument; -d implies -r */ opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir); argv += optind; if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */ /* Run by non-root */ if (opt_ler & (OPT_u|OPT_c)) bb_error_msg_and_die(bb_msg_you_must_be_root); } if (opt_ler & OPT_u) { pas = xgetpwnam(user_name); } else { pas = xgetpwuid(getuid()); } #define user_name DONT_USE_ME_BEYOND_THIS_POINT /* From now on, keep only -l, -e, -r bits */ opt_ler &= OPT_ler; if ((opt_ler - 1) & opt_ler) /* more than one bit set? */ bb_show_usage(); /* Read replacement file under user's UID/GID/group vector */ src_fd = STDIN_FILENO; if (!opt_ler) { /* Replace? */ if (!argv[0]) bb_show_usage(); if (NOT_LONE_DASH(argv[0])) { src_fd = open_as_user(pas, argv[0]); if (src_fd < 0) bb_error_msg_and_die("user %s cannot read %s", pas->pw_name, argv[0]); } } /* cd to our crontab directory */ xchdir(crontab_dir); tmp_fname = NULL; /* Handle requested operation */ switch (opt_ler) { default: /* case OPT_r: Delete */ unlink(pas->pw_name); break; case OPT_l: /* List */ { char *args[2] = { pas->pw_name, NULL }; return bb_cat(args); /* list exits, * the rest go play with cron update file */ } case OPT_e: /* Edit */ tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid()); /* No O_EXCL: we don't want to be stuck if earlier crontabs * were killed, leaving stale temp file behind */ src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600); fchown(src_fd, pas->pw_uid, pas->pw_gid); fd = open(pas->pw_name, O_RDONLY); if (fd >= 0) { bb_copyfd_eof(fd, src_fd); close(fd); xlseek(src_fd, 0, SEEK_SET); } close_on_exec_on(src_fd); /* don't want editor to see this fd */ edit_file(pas, tmp_fname); /* fall through */ case 0: /* Replace (no -l, -e, or -r were given) */ new_fname = xasprintf("%s.new", pas->pw_name); fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600); if (fd >= 0) { bb_copyfd_eof(src_fd, fd); close(fd); xrename(new_fname, pas->pw_name); } else { bb_error_msg("can't create %s/%s", crontab_dir, new_fname); } if (tmp_fname) unlink(tmp_fname); /*free(tmp_fname);*/ /*free(new_fname);*/ } /* switch */ /* Bump notification file. Handle window where crond picks file up * before we can write our entry out. */ while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) { struct stat st; fdprintf(fd, "%s\n", pas->pw_name); if (fstat(fd, &st) != 0 || st.st_nlink != 0) { /*close(fd);*/ break; } /* st.st_nlink == 0: * file was deleted, maybe crond missed our notification */ close(fd); /* loop */ } if (fd < 0) { bb_error_msg("can't append to %s/%s", crontab_dir, CRONUPDATE); } return 0; }