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
237 int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
240 /* Under the assumption that we are running privileged we
241 * first change the access mode and only then hand out
242 * ownership to avoid a window where access is too open. */
244 if (mode != MODE_INVALID)
245 if (chmod(path, mode) < 0)
248 if (uid != UID_INVALID || gid != GID_INVALID)
249 if (chown(path, uid, gid) < 0)
255 int fchmod_umask(int fd, mode_t m) {
260 r = fchmod(fd, m & (~u)) < 0 ? -errno : 0;
266 int fd_warn_permissions(const char *path, int fd) {
269 if (fstat(fd, &st) < 0)
272 if (st.st_mode & 0111)
273 log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
275 if (st.st_mode & 0002)
276 log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
278 if (getpid_cached() == 1 && (st.st_mode & 0044) != 0044)
279 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);
284 int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
285 char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
286 _cleanup_close_ int fd = -1;
291 /* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink
292 * itself which is updated, not its target
294 * Returns the first error we encounter, but tries to apply as much as possible. */
297 (void) mkdir_parents(path, 0755);
299 /* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in
300 * case the path refers to an existing device or socket node, as we can open it successfully in all cases, and
301 * won't trigger any driver magic or so. */
302 fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
307 /* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file
308 * here, and nothing else */
309 fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
314 /* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode,
315 * ownership and time of the file node in all cases, even if the fd refers to an O_PATH object â which is
316 * something fchown(), fchmod(), futimensat() don't allow. */
317 xsprintf(fdpath, "/proc/self/fd/%i", fd);
319 if (mode != MODE_INVALID)
320 if (chmod(fdpath, mode) < 0)
323 if (uid_is_valid(uid) || gid_is_valid(gid))
324 if (chown(fdpath, uid, gid) < 0 && ret >= 0)
327 if (stamp != USEC_INFINITY) {
328 struct timespec ts[2];
330 timespec_store(&ts[0], stamp);
332 r = utimensat(AT_FDCWD, fdpath, ts, 0);
334 r = utimensat(AT_FDCWD, fdpath, NULL, 0);
335 if (r < 0 && ret >= 0)
341 int touch(const char *path) {
342 return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
345 #if 0 /// UNNEEDED by elogind
346 int symlink_idempotent(const char *from, const char *to) {
352 if (symlink(from, to) < 0) {
353 _cleanup_free_ char *p = NULL;
358 r = readlink_malloc(to, &p);
359 if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */
361 if (r < 0) /* Any other error? In that case propagate it as is */
364 if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */
371 int symlink_atomic(const char *from, const char *to) {
372 _cleanup_free_ char *t = NULL;
378 r = tempfn_random(to, NULL, &t);
382 if (symlink(from, t) < 0)
385 if (rename(t, to) < 0) {
393 int mknod_atomic(const char *path, mode_t mode, dev_t dev) {
394 _cleanup_free_ char *t = NULL;
399 r = tempfn_random(path, NULL, &t);
403 if (mknod(t, mode, dev) < 0)
406 if (rename(t, path) < 0) {
414 int mkfifo_atomic(const char *path, mode_t mode) {
415 _cleanup_free_ char *t = NULL;
420 r = tempfn_random(path, NULL, &t);
424 if (mkfifo(t, mode) < 0)
427 if (rename(t, path) < 0) {
436 int get_files_in_directory(const char *path, char ***list) {
437 _cleanup_closedir_ DIR *d = NULL;
439 size_t bufsize = 0, n = 0;
440 _cleanup_strv_free_ char **l = NULL;
444 /* Returns all files in a directory in *list, and the number
445 * of files as return value. If list is NULL returns only the
452 FOREACH_DIRENT_ALL(de, d, return -errno) {
453 dirent_ensure_type(d, de);
455 if (!dirent_is_file(de))
459 /* one extra slot is needed for the terminating NULL */
460 if (!GREEDY_REALLOC(l, bufsize, n + 2))
463 l[n] = strdup(de->d_name);
474 l = NULL; /* avoid freeing */
480 static int getenv_tmp_dir(const char **ret_path) {
486 /* We use the same order of environment variables python uses in tempfile.gettempdir():
487 * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
488 FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
491 e = secure_getenv(n);
494 if (!path_is_absolute(e)) {
498 if (!path_is_normalized(e)) {
515 /* Remember first error, to make this more debuggable */
527 static int tmp_dir_internal(const char *def, const char **ret) {
534 r = getenv_tmp_dir(&e);
540 k = is_dir(def, true);
544 return r < 0 ? r : k;
550 #if 0 /// UNNEEDED by elogind
551 int var_tmp_dir(const char **ret) {
553 /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
554 * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
555 * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
556 * making it a variable that overrides all temporary file storage locations. */
558 return tmp_dir_internal("/var/tmp", ret);
562 int tmp_dir(const char **ret) {
564 /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
565 * backed by an in-memory file system: /tmp. */
567 return tmp_dir_internal("/tmp", ret);
570 #if 0 /// UNNEEDED by elogind
571 int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
572 char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
575 /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
576 xsprintf(path, "/proc/self/fd/%i", what);
578 r = inotify_add_watch(fd, path, mask);
586 static bool safe_transition(const struct stat *a, const struct stat *b) {
587 /* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to
588 * privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files
589 * making us believe we read something safe even though it isn't safe in the specific context we open it in. */
591 if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */
594 return a->st_uid == b->st_uid; /* Otherwise we need to stay within the same UID */
597 int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) {
598 _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
599 _cleanup_close_ int fd = -1;
600 unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
601 struct stat previous_stat;
608 /* Either the file may be missing, or we return an fd to the final object, but both make no sense */
609 if ((flags & (CHASE_NONEXISTENT|CHASE_OPEN)) == (CHASE_NONEXISTENT|CHASE_OPEN))
615 /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
616 * symlinks relative to a root directory, instead of the root of the host.
618 * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
619 * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
620 * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
621 * prefixed accordingly.
623 * Algorithmically this operates on two path buffers: "done" are the components of the path we already
624 * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
625 * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
626 * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
627 * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
630 * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
631 * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
632 * function what to do when encountering a symlink with an absolute path as directory: prefix it by the
635 /* A root directory of "/" or "" is identical to none */
636 if (isempty(original_root) || path_equal(original_root, "/"))
637 original_root = NULL;
640 r = path_make_absolute_cwd(original_root, &root);
644 if (flags & CHASE_PREFIX_ROOT) {
646 /* We don't support relative paths in combination with a root directory */
647 if (!path_is_absolute(path))
650 path = prefix_roota(root, path);
654 r = path_make_absolute_cwd(path, &buffer);
658 fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
662 if (flags & CHASE_SAFE) {
663 if (fstat(fd, &previous_stat) < 0)
669 _cleanup_free_ char *first = NULL;
670 _cleanup_close_ int child = -1;
674 /* Determine length of first component in the path */
675 n = strspn(todo, "/"); /* The slashes */
676 m = n + strcspn(todo + n, "/"); /* The entire length of the component */
678 /* Extract the first component. */
679 first = strndup(todo, m);
685 /* Empty? Then we reached the end. */
689 /* Just a single slash? Then we reached the end. */
690 if (path_equal(first, "/")) {
691 /* Preserve the trailing slash */
692 if (!strextend(&done, "/", NULL))
698 /* Just a dot? Then let's eat this up. */
699 if (path_equal(first, "/."))
702 /* Two dots? Then chop off the last bit of what we already found out. */
703 if (path_equal(first, "/..")) {
704 _cleanup_free_ char *parent = NULL;
705 _cleanup_close_ int fd_parent = -1;
707 /* If we already are at the top, then going up will not change anything. This is in-line with
708 * how the kernel handles this. */
709 if (isempty(done) || path_equal(done, "/"))
712 parent = dirname_malloc(done);
716 /* Don't allow this to leave the root dir. */
718 path_startswith(done, root) &&
719 !path_startswith(parent, root))
722 free_and_replace(done, parent);
724 fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
728 if (flags & CHASE_SAFE) {
729 if (fstat(fd_parent, &st) < 0)
732 if (!safe_transition(&previous_stat, &st))
745 /* Otherwise let's see what this is. */
746 child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
749 if (errno == ENOENT &&
750 (flags & CHASE_NONEXISTENT) &&
751 (isempty(todo) || path_is_normalized(todo))) {
753 /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
754 * what we got so far. But don't allow this if the remaining path contains "../ or "./"
755 * or something else weird. */
757 /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
758 if (streq_ptr(done, "/"))
761 if (!strextend(&done, first, todo, NULL))
771 if (fstat(child, &st) < 0)
773 if ((flags & CHASE_SAFE) &&
774 !safe_transition(&previous_stat, &st))
779 if ((flags & CHASE_NO_AUTOFS) &&
780 fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0)
783 if (S_ISLNK(st.st_mode)) {
786 _cleanup_free_ char *destination = NULL;
788 /* This is a symlink, in this case read the destination. But let's make sure we don't follow
789 * symlinks without bounds. */
790 if (--max_follow <= 0)
793 r = readlinkat_malloc(fd, first + n, &destination);
796 if (isempty(destination))
799 if (path_is_absolute(destination)) {
801 /* An absolute destination. Start the loop from the beginning, but use the root
802 * directory as base. */
805 fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
809 if (flags & CHASE_SAFE) {
810 if (fstat(fd, &st) < 0)
813 if (!safe_transition(&previous_stat, &st))
821 /* Note that we do not revalidate the root, we take it as is. */
830 /* Prefix what's left to do with what we just read, and start the loop again, but
831 * remain in the current directory. */
832 joined = strjoin(destination, todo);
834 joined = strjoin("/", destination, todo);
839 todo = buffer = joined;
844 /* If this is not a symlink, then let's just add the name we read to what we already verified. */
849 /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
850 if (streq(done, "/"))
853 if (!strextend(&done, first, NULL))
857 /* And iterate again, but go one directory further down. */
864 /* Special case, turn the empty string into "/", to indicate the root directory. */
875 if (flags & CHASE_OPEN) {
878 /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a proper fd by
879 * opening /proc/self/fd/xyz. */
891 int access_fd(int fd, int mode) {
892 char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1];
895 /* Like access() but operates on an already open fd */
897 xsprintf(p, "/proc/self/fd/%i", fd);
906 int unlinkat_deallocate(int fd, const char *name, int flags) {
907 _cleanup_close_ int truncate_fd = -1;
911 /* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other
912 * link to it. This is useful to ensure that other processes that might have the file open for reading won't be
913 * able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up
914 * jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and
915 * returned to the free pool.
917 * Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (đ) if supported, which means
918 * the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other
919 * programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes
920 * underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.)
921 * However if hole punching is not implemented in the kernel or file system we'll fall back to normal file
922 * truncation (đĒ), as our goal of deallocating the data space trumps our goal of being nice to readers (đ).
924 * Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the
925 * primary job â to delete the file â is accomplished. */
927 if ((flags & AT_REMOVEDIR) == 0) {
928 truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK);
929 if (truncate_fd < 0) {
931 /* If this failed because the file doesn't exist propagate the error right-away. Also,
932 * AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is
933 * returned when this is a directory but we are not supposed to delete those, hence propagate
934 * the error right-away too. */
935 if (IN_SET(errno, ENOENT, EISDIR))
938 if (errno != ELOOP) /* don't complain if this is a symlink */
939 log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name);
943 if (unlinkat(fd, name, flags) < 0)
946 if (truncate_fd < 0) /* Don't have a file handle, can't do more âšī¸ */
949 if (fstat(truncate_fd, &st) < 0) {
950 log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring.", name);
954 if (!S_ISREG(st.st_mode) || st.st_blocks == 0 || st.st_nlink > 0)
957 /* If this is a regular file, it actually took up space on disk and there are no other links it's time to
958 * punch-hole/truncate this to release the disk space. */
960 bs = MAX(st.st_blksize, 512);
961 l = DIV_ROUND_UP(st.st_size, bs) * bs; /* Round up to next block size */
963 if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0)
964 return 0; /* Successfully punched a hole! đ */
966 /* Fall back to truncation */
967 if (ftruncate(truncate_fd, 0) < 0) {
968 log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m");