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/* 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 the GPL v2 or later, see the file LICENSE in this tarball.
*/
#include "libbb.h"
#ifndef CRONTABS
#define CRONTABS "/var/spool/cron/crontabs"
#endif
#ifndef CRONUPDATE
#define CRONUPDATE "cron.update"
#endif
static void change_user(const struct passwd *pas)
{
xsetenv("USER", pas->pw_name);
xsetenv("HOME", pas->pw_dir);
xsetenv("SHELL", DEFAULT_SHELL);
/* initgroups, setgid, setuid */
change_identity(pas);
if (chdir(pas->pw_dir) < 0) {
bb_perror_msg("chdir(%s) by %s failed",
pas->pw_dir, pas->pw_name);
xchdir("/tmp");
}
}
static void edit_file(const struct passwd *pas, const char *file)
{
const char *ptr;
int pid = vfork();
if (pid < 0) /* failure */
bb_perror_msg_and_die("vfork");
if (pid) { /* parent */
wait4pid(pid);
return;
}
/* CHILD - change user and run editor */
change_user(pas);
ptr = getenv("VISUAL");
if (!ptr) {
ptr = getenv("EDITOR");
if (!ptr)
ptr = "vi";
}
BB_EXECLP(ptr, ptr, file, NULL);
bb_perror_msg_and_die("exec %s", ptr);
}
static int open_as_user(const struct passwd *pas, const char *file)
{
pid_t pid;
char c;
pid = vfork();
if (pid < 0) /* ERROR */
bb_perror_msg_and_die("vfork");
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("only root can use -c or -u");
}
if (opt_ler & OPT_u) {
pas = getpwnam(user_name);
if (!pas)
bb_error_msg_and_die("user %s is not known", user_name);
} else {
/* XXX: xgetpwuid */
uid_t my_uid = getuid();
pas = getpwuid(my_uid);
if (!pas)
bb_perror_msg_and_die("unknown uid %d", (int)my_uid);
}
#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("cannot 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("cannot append to %s/%s",
crontab_dir, CRONUPDATE);
}
return 0;
}
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