1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 This file is part of systemd.
5 Copyright 2010 Lennart Poettering
7 systemd is free software; you can redistribute it and/or modify it
8 under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version.
12 systemd is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with systemd; If not, see <http://www.gnu.org/licenses/>.
27 #include <linux/magic.h>
31 #include "alloc-util.h"
32 #include "dirent-util.h"
38 //#include "missing.h"
40 #include "parse-util.h"
41 #include "path-util.h"
42 //#include "process-util.h"
43 #include "stat-util.h"
44 #include "stdio-util.h"
45 #include "string-util.h"
47 //#include "time-util.h"
48 #include "user-util.h"
51 /// Additional includes needed by elogind
52 #include "process-util.h"
54 int unlink_noerrno(const char *path) {
65 #if 0 /// UNNEEDED by elogind
66 int rmdir_parents(const char *path, const char *stop) {
75 /* Skip trailing slashes */
76 while (l > 0 && path[l-1] == '/')
82 /* Skip last component */
83 while (l > 0 && path[l-1] != '/')
86 /* Skip trailing slashes */
87 while (l > 0 && path[l-1] == '/')
97 if (path_startswith(stop, t)) {
113 int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
117 ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE);
121 /* renameat2() exists since Linux 3.15, btrfs added support for it later.
122 * If it is not implemented, fallback to another method. */
123 if (!IN_SET(errno, EINVAL, ENOSYS))
126 /* The link()/unlink() fallback does not work on directories. But
127 * renameat() without RENAME_NOREPLACE gives the same semantics on
128 * directories, except when newpath is an *empty* directory. This is
130 ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW);
131 if (ret >= 0 && S_ISDIR(buf.st_mode)) {
132 ret = renameat(olddirfd, oldpath, newdirfd, newpath);
133 return ret >= 0 ? 0 : -errno;
136 /* If it is not a directory, use the link()/unlink() fallback. */
137 ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0);
141 ret = unlinkat(olddirfd, oldpath, 0);
143 /* backup errno before the following unlinkat() alters it */
145 (void) unlinkat(newdirfd, newpath, 0);
154 int readlinkat_malloc(int fd, const char *p, char **ret) {
169 n = readlinkat(fd, p, c, l-1);
176 if ((size_t) n < l-1) {
187 int readlink_malloc(const char *p, char **ret) {
188 return readlinkat_malloc(AT_FDCWD, p, ret);
191 #if 0 /// UNNEEDED by elogind
192 int readlink_value(const char *p, char **ret) {
193 _cleanup_free_ char *link = NULL;
197 r = readlink_malloc(p, &link);
201 value = basename(link);
205 value = strdup(value);
215 int readlink_and_make_absolute(const char *p, char **r) {
216 _cleanup_free_ char *target = NULL;
223 j = readlink_malloc(p, &target);
227 k = file_in_same_dir(p, target);
235 #if 0 /// UNNEEDED by elogind
236 int readlink_and_make_absolute_root(const char *root, const char *path, char **ret) {
237 _cleanup_free_ char *target = NULL, *t = NULL;
241 full = prefix_roota(root, path);
242 r = readlink_malloc(full, &target);
246 t = file_in_same_dir(path, target);
257 int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
260 /* Under the assumption that we are running privileged we
261 * first change the access mode and only then hand out
262 * ownership to avoid a window where access is too open. */
264 if (mode != MODE_INVALID)
265 if (chmod(path, mode) < 0)
268 if (uid != UID_INVALID || gid != GID_INVALID)
269 if (chown(path, uid, gid) < 0)
275 int fchmod_umask(int fd, mode_t m) {
280 r = fchmod(fd, m & (~u)) < 0 ? -errno : 0;
286 int fd_warn_permissions(const char *path, int fd) {
289 if (fstat(fd, &st) < 0)
292 if (st.st_mode & 0111)
293 log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
295 if (st.st_mode & 0002)
296 log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
298 if (getpid_cached() == 1 && (st.st_mode & 0044) != 0044)
299 log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path);
304 int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
305 char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
306 _cleanup_close_ int fd = -1;
311 /* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink
312 * itself which is updated, not its target
314 * Returns the first error we encounter, but tries to apply as much as possible. */
317 (void) mkdir_parents(path, 0755);
319 /* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in
320 * case the path refers to an existing device or socket node, as we can open it successfully in all cases, and
321 * won't trigger any driver magic or so. */
322 fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
327 /* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file
328 * here, and nothing else */
329 fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
334 /* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode,
335 * ownership and time of the file node in all cases, even if the fd refers to an O_PATH object — which is
336 * something fchown(), fchmod(), futimensat() don't allow. */
337 xsprintf(fdpath, "/proc/self/fd/%i", fd);
339 if (mode != MODE_INVALID)
340 if (chmod(fdpath, mode) < 0)
343 if (uid_is_valid(uid) || gid_is_valid(gid))
344 if (chown(fdpath, uid, gid) < 0 && ret >= 0)
347 if (stamp != USEC_INFINITY) {
348 struct timespec ts[2];
350 timespec_store(&ts[0], stamp);
352 r = utimensat(AT_FDCWD, fdpath, ts, 0);
354 r = utimensat(AT_FDCWD, fdpath, NULL, 0);
355 if (r < 0 && ret >= 0)
361 int touch(const char *path) {
362 return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
365 #if 0 /// UNNEEDED by elogind
366 int symlink_idempotent(const char *from, const char *to) {
372 if (symlink(from, to) < 0) {
373 _cleanup_free_ char *p = NULL;
378 r = readlink_malloc(to, &p);
379 if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */
381 if (r < 0) /* Any other error? In that case propagate it as is */
384 if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */
391 int symlink_atomic(const char *from, const char *to) {
392 _cleanup_free_ char *t = NULL;
398 r = tempfn_random(to, NULL, &t);
402 if (symlink(from, t) < 0)
405 if (rename(t, to) < 0) {
413 int mknod_atomic(const char *path, mode_t mode, dev_t dev) {
414 _cleanup_free_ char *t = NULL;
419 r = tempfn_random(path, NULL, &t);
423 if (mknod(t, mode, dev) < 0)
426 if (rename(t, path) < 0) {
434 int mkfifo_atomic(const char *path, mode_t mode) {
435 _cleanup_free_ char *t = NULL;
440 r = tempfn_random(path, NULL, &t);
444 if (mkfifo(t, mode) < 0)
447 if (rename(t, path) < 0) {
456 int get_files_in_directory(const char *path, char ***list) {
457 _cleanup_closedir_ DIR *d = NULL;
459 size_t bufsize = 0, n = 0;
460 _cleanup_strv_free_ char **l = NULL;
464 /* Returns all files in a directory in *list, and the number
465 * of files as return value. If list is NULL returns only the
472 FOREACH_DIRENT_ALL(de, d, return -errno) {
473 dirent_ensure_type(d, de);
475 if (!dirent_is_file(de))
479 /* one extra slot is needed for the terminating NULL */
480 if (!GREEDY_REALLOC(l, bufsize, n + 2))
483 l[n] = strdup(de->d_name);
494 l = NULL; /* avoid freeing */
500 static int getenv_tmp_dir(const char **ret_path) {
506 /* We use the same order of environment variables python uses in tempfile.gettempdir():
507 * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
508 FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
511 e = secure_getenv(n);
514 if (!path_is_absolute(e)) {
518 if (!path_is_normalized(e)) {
535 /* Remember first error, to make this more debuggable */
547 static int tmp_dir_internal(const char *def, const char **ret) {
554 r = getenv_tmp_dir(&e);
560 k = is_dir(def, true);
564 return r < 0 ? r : k;
570 #if 0 /// UNNEEDED by elogind
571 int var_tmp_dir(const char **ret) {
573 /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
574 * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
575 * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
576 * making it a variable that overrides all temporary file storage locations. */
578 return tmp_dir_internal("/var/tmp", ret);
582 int tmp_dir(const char **ret) {
584 /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
585 * backed by an in-memory file system: /tmp. */
587 return tmp_dir_internal("/tmp", ret);
590 #if 0 /// UNNEEDED by elogind
591 int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
592 char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
595 /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
596 xsprintf(path, "/proc/self/fd/%i", what);
598 r = inotify_add_watch(fd, path, mask);
606 static bool safe_transition(const struct stat *a, const struct stat *b) {
607 /* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to
608 * privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files
609 * making us believe we read something safe even though it isn't safe in the specific context we open it in. */
611 if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */
614 return a->st_uid == b->st_uid; /* Otherwise we need to stay within the same UID */
617 int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) {
618 _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
619 _cleanup_close_ int fd = -1;
620 unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
621 struct stat previous_stat;
628 /* Either the file may be missing, or we return an fd to the final object, but both make no sense */
629 if ((flags & (CHASE_NONEXISTENT|CHASE_OPEN)) == (CHASE_NONEXISTENT|CHASE_OPEN))
635 /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
636 * symlinks relative to a root directory, instead of the root of the host.
638 * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
639 * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
640 * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
641 * prefixed accordingly.
643 * Algorithmically this operates on two path buffers: "done" are the components of the path we already
644 * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
645 * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
646 * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
647 * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
650 * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
651 * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
652 * function what to do when encountering a symlink with an absolute path as directory: prefix it by the
655 /* A root directory of "/" or "" is identical to none */
656 if (isempty(original_root) || path_equal(original_root, "/"))
657 original_root = NULL;
660 r = path_make_absolute_cwd(original_root, &root);
664 if (flags & CHASE_PREFIX_ROOT) {
666 /* We don't support relative paths in combination with a root directory */
667 if (!path_is_absolute(path))
670 path = prefix_roota(root, path);
674 r = path_make_absolute_cwd(path, &buffer);
678 fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
682 if (flags & CHASE_SAFE) {
683 if (fstat(fd, &previous_stat) < 0)
689 _cleanup_free_ char *first = NULL;
690 _cleanup_close_ int child = -1;
694 /* Determine length of first component in the path */
695 n = strspn(todo, "/"); /* The slashes */
696 m = n + strcspn(todo + n, "/"); /* The entire length of the component */
698 /* Extract the first component. */
699 first = strndup(todo, m);
705 /* Empty? Then we reached the end. */
709 /* Just a single slash? Then we reached the end. */
710 if (path_equal(first, "/")) {
711 /* Preserve the trailing slash */
712 if (!strextend(&done, "/", NULL))
718 /* Just a dot? Then let's eat this up. */
719 if (path_equal(first, "/."))
722 /* Two dots? Then chop off the last bit of what we already found out. */
723 if (path_equal(first, "/..")) {
724 _cleanup_free_ char *parent = NULL;
725 _cleanup_close_ int fd_parent = -1;
727 /* If we already are at the top, then going up will not change anything. This is in-line with
728 * how the kernel handles this. */
729 if (isempty(done) || path_equal(done, "/"))
732 parent = dirname_malloc(done);
736 /* Don't allow this to leave the root dir. */
738 path_startswith(done, root) &&
739 !path_startswith(parent, root))
742 free_and_replace(done, parent);
744 fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
748 if (flags & CHASE_SAFE) {
749 if (fstat(fd_parent, &st) < 0)
752 if (!safe_transition(&previous_stat, &st))
765 /* Otherwise let's see what this is. */
766 child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
769 if (errno == ENOENT &&
770 (flags & CHASE_NONEXISTENT) &&
771 (isempty(todo) || path_is_normalized(todo))) {
773 /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
774 * what we got so far. But don't allow this if the remaining path contains "../ or "./"
775 * or something else weird. */
777 /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
778 if (streq_ptr(done, "/"))
781 if (!strextend(&done, first, todo, NULL))
791 if (fstat(child, &st) < 0)
793 if ((flags & CHASE_SAFE) &&
794 !safe_transition(&previous_stat, &st))
799 if ((flags & CHASE_NO_AUTOFS) &&
800 fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0)
803 if (S_ISLNK(st.st_mode)) {
806 _cleanup_free_ char *destination = NULL;
808 /* This is a symlink, in this case read the destination. But let's make sure we don't follow
809 * symlinks without bounds. */
810 if (--max_follow <= 0)
813 r = readlinkat_malloc(fd, first + n, &destination);
816 if (isempty(destination))
819 if (path_is_absolute(destination)) {
821 /* An absolute destination. Start the loop from the beginning, but use the root
822 * directory as base. */
825 fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
829 if (flags & CHASE_SAFE) {
830 if (fstat(fd, &st) < 0)
833 if (!safe_transition(&previous_stat, &st))
841 /* Note that we do not revalidate the root, we take it as is. */
850 /* Prefix what's left to do with what we just read, and start the loop again, but
851 * remain in the current directory. */
852 joined = strjoin(destination, todo);
854 joined = strjoin("/", destination, todo);
859 todo = buffer = joined;
864 /* If this is not a symlink, then let's just add the name we read to what we already verified. */
869 /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
870 if (streq(done, "/"))
873 if (!strextend(&done, first, NULL))
877 /* And iterate again, but go one directory further down. */
884 /* Special case, turn the empty string into "/", to indicate the root directory. */
895 if (flags & CHASE_OPEN) {
898 /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a proper fd by
899 * opening /proc/self/fd/xyz. */
911 int access_fd(int fd, int mode) {
912 char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1];
915 /* Like access() but operates on an already open fd */
917 xsprintf(p, "/proc/self/fd/%i", fd);