Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 | /* 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"
#define CRONTABS CONFIG_FEATURE_CROND_DIR "/crontabs"
#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 = 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("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;
}
|