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Systemd/src/basic/fs-util.c

1615 lines
55 KiB

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stddef.h>
#include <stdlib.h>
#include <linux/falloc.h>
#include <linux/magic.h>
#include <unistd.h>
#include "alloc-util.h"
#include "blockdev-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "locale-util.h"
#include "log.h"
#include "macro.h"
#include "missing_fcntl.h"
#include "missing_fs.h"
#include "missing_syscall.h"
#include "mkdir.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
#include "random-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strv.h"
#include "time-util.h"
#include "tmpfile-util.h"
#include "user-util.h"
#include "util.h"
int unlink_noerrno(const char *path) {
PROTECT_ERRNO;
int r;
r = unlink(path);
if (r < 0)
return -errno;
return 0;
}
int rmdir_parents(const char *path, const char *stop) {
size_t l;
int r = 0;
assert(path);
assert(stop);
l = strlen(path);
/* Skip trailing slashes */
while (l > 0 && path[l-1] == '/')
l--;
while (l > 0) {
char *t;
/* Skip last component */
while (l > 0 && path[l-1] != '/')
l--;
/* Skip trailing slashes */
while (l > 0 && path[l-1] == '/')
l--;
if (l <= 0)
break;
t = strndup(path, l);
if (!t)
return -ENOMEM;
if (path_startswith(stop, t)) {
free(t);
return 0;
}
r = rmdir(t);
free(t);
if (r < 0)
if (errno != ENOENT)
return -errno;
}
return 0;
}
int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
int r;
/* Try the ideal approach first */
if (renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE) >= 0)
return 0;
/* renameat2() exists since Linux 3.15, btrfs and FAT added support for it later. If it is not implemented,
* fall back to a different method. */
if (!IN_SET(errno, EINVAL, ENOSYS, ENOTTY))
return -errno;
/* Let's try to use linkat()+unlinkat() as fallback. This doesn't work on directories and on some file systems
* that do not support hard links (such as FAT, most prominently), but for files it's pretty close to what we
* want — though not atomic (i.e. for a short period both the new and the old filename will exist). */
if (linkat(olddirfd, oldpath, newdirfd, newpath, 0) >= 0) {
if (unlinkat(olddirfd, oldpath, 0) < 0) {
r = -errno; /* Backup errno before the following unlinkat() alters it */
(void) unlinkat(newdirfd, newpath, 0);
return r;
}
return 0;
}
if (!IN_SET(errno, EINVAL, ENOSYS, ENOTTY, EPERM)) /* FAT returns EPERM on link()… */
return -errno;
/* OK, neither RENAME_NOREPLACE nor linkat()+unlinkat() worked. Let's then fall back to the racy TOCTOU
* vulnerable accessat(F_OK) check followed by classic, replacing renameat(), we have nothing better. */
if (faccessat(newdirfd, newpath, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
return -EEXIST;
if (errno != ENOENT)
return -errno;
if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0)
return -errno;
return 0;
}
int readlinkat_malloc(int fd, const char *p, char **ret) {
size_t l = FILENAME_MAX+1;
int r;
assert(p);
assert(ret);
for (;;) {
char *c;
ssize_t n;
c = new(char, l);
if (!c)
return -ENOMEM;
n = readlinkat(fd, p, c, l-1);
if (n < 0) {
r = -errno;
free(c);
return r;
}
if ((size_t) n < l-1) {
c[n] = 0;
*ret = c;
return 0;
}
free(c);
l *= 2;
}
}
int readlink_malloc(const char *p, char **ret) {
return readlinkat_malloc(AT_FDCWD, p, ret);
}
int readlink_value(const char *p, char **ret) {
_cleanup_free_ char *link = NULL;
char *value;
int r;
r = readlink_malloc(p, &link);
if (r < 0)
return r;
value = basename(link);
if (!value)
return -ENOENT;
value = strdup(value);
if (!value)
return -ENOMEM;
*ret = value;
return 0;
}
int readlink_and_make_absolute(const char *p, char **r) {
_cleanup_free_ char *target = NULL;
char *k;
int j;
assert(p);
assert(r);
j = readlink_malloc(p, &target);
if (j < 0)
return j;
k = file_in_same_dir(p, target);
if (!k)
return -ENOMEM;
*r = k;
return 0;
}
int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
_cleanup_close_ int fd = -1;
assert(path);
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); /* Let's acquire an O_PATH fd, as precaution to change
* mode/owner on the same file */
if (fd < 0)
return -errno;
return fchmod_and_chown(fd, mode, uid, gid);
}
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
bool do_chown, do_chmod;
struct stat st;
int r;
/* Change ownership and access mode of the specified fd. Tries to do so safely, ensuring that at no
* point in time the access mode is above the old access mode under the old ownership or the new
* access mode under the new ownership. Note: this call tries hard to leave the access mode
* unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does
* on chown().
*
* This call is happy with O_PATH fds. */
if (fstat(fd, &st) < 0)
return -errno;
do_chown =
(uid != UID_INVALID && st.st_uid != uid) ||
(gid != GID_INVALID && st.st_gid != gid);
do_chmod =
!S_ISLNK(st.st_mode) && /* chmod is not defined on symlinks */
((mode != MODE_INVALID && ((st.st_mode ^ mode) & 07777) != 0) ||
do_chown); /* If we change ownership, make sure we reset the mode afterwards, since chown()
* modifies the access mode too */
if (mode == MODE_INVALID)
mode = st.st_mode; /* If we only shall do a chown(), save original mode, since chown() might break it. */
else if ((mode & S_IFMT) != 0 && ((mode ^ st.st_mode) & S_IFMT) != 0)
return -EINVAL; /* insist on the right file type if it was specified */
if (do_chown && do_chmod) {
mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */
if (((minimal ^ st.st_mode) & 07777) != 0) {
r = fchmod_opath(fd, minimal & 07777);
if (r < 0)
return r;
}
}
if (do_chown)
if (fchownat(fd, "", uid, gid, AT_EMPTY_PATH) < 0)
return -errno;
if (do_chmod) {
r = fchmod_opath(fd, mode & 07777);
if (r < 0)
return r;
}
return do_chown || do_chmod;
}
int fchmod_umask(int fd, mode_t m) {
mode_t u;
int r;
u = umask(0777);
r = fchmod(fd, m & (~u)) < 0 ? -errno : 0;
umask(u);
return r;
}
int fchmod_opath(int fd, mode_t m) {
char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
/* This function operates also on fd that might have been opened with
* O_PATH. Indeed fchmodat() doesn't have the AT_EMPTY_PATH flag like
* fchownat() does. */
xsprintf(procfs_path, "/proc/self/fd/%i", fd);
if (chmod(procfs_path, m) < 0) {
if (errno != ENOENT)
return -errno;
if (proc_mounted() == 0)
return -ENOSYS; /* if we have no /proc/, the concept is not implementable */
return -ENOENT;
}
return 0;
}
int futimens_opath(int fd, const struct timespec ts[2]) {
char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
/* Similar to fchmod_path() but for futimens() */
xsprintf(procfs_path, "/proc/self/fd/%i", fd);
if (utimensat(AT_FDCWD, procfs_path, ts, 0) < 0) {
if (errno != ENOENT)
return -errno;
if (proc_mounted() == 0)
return -ENOSYS; /* if we have no /proc/, the concept is not implementable */
return -ENOENT;
}
return 0;
}
int stat_warn_permissions(const char *path, const struct stat *st) {
assert(path);
assert(st);
/* Don't complain if we are reading something that is not a file, for example /dev/null */
if (!S_ISREG(st->st_mode))
return 0;
if (st->st_mode & 0111)
log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
if (st->st_mode & 0002)
log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
if (getpid_cached() == 1 && (st->st_mode & 0044) != 0044)
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);
return 0;
}
int fd_warn_permissions(const char *path, int fd) {
struct stat st;
assert(path);
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
return stat_warn_permissions(path, &st);
}
int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
_cleanup_close_ int fd = -1;
int r, ret = 0;
assert(path);
/* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink
* itself which is updated, not its target
*
* Returns the first error we encounter, but tries to apply as much as possible. */
if (parents)
(void) mkdir_parents(path, 0755);
/* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in
* case the path refers to an existing device or socket node, as we can open it successfully in all cases, and
* won't trigger any driver magic or so. */
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (fd < 0) {
if (errno != ENOENT)
return -errno;
/* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file
* here, and nothing else */
fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
if (fd < 0)
return -errno;
}
/* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode,
* ownership and time of the file node in all cases, even if the fd refers to an O_PATH object — which is
* something fchown(), fchmod(), futimensat() don't allow. */
xsprintf(fdpath, "/proc/self/fd/%i", fd);
ret = fchmod_and_chown(fd, mode, uid, gid);
if (stamp != USEC_INFINITY) {
struct timespec ts[2];
timespec_store(&ts[0], stamp);
ts[1] = ts[0];
r = utimensat(AT_FDCWD, fdpath, ts, 0);
} else
r = utimensat(AT_FDCWD, fdpath, NULL, 0);
if (r < 0 && ret >= 0)
return -errno;
return ret;
}
int touch(const char *path) {
return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
}
int symlink_idempotent(const char *from, const char *to, bool make_relative) {
_cleanup_free_ char *relpath = NULL;
int r;
assert(from);
assert(to);
if (make_relative) {
_cleanup_free_ char *parent = NULL;
parent = dirname_malloc(to);
if (!parent)
return -ENOMEM;
r = path_make_relative(parent, from, &relpath);
if (r < 0)
return r;
from = relpath;
}
if (symlink(from, to) < 0) {
_cleanup_free_ char *p = NULL;
if (errno != EEXIST)
return -errno;
r = readlink_malloc(to, &p);
if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */
return -EEXIST;
if (r < 0) /* Any other error? In that case propagate it as is */
return r;
if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */
return -EEXIST;
}
return 0;
}
int symlink_atomic(const char *from, const char *to) {
_cleanup_free_ char *t = NULL;
int r;
assert(from);
assert(to);
r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
if (symlink(from, t) < 0)
return -errno;
if (rename(t, to) < 0) {
unlink_noerrno(t);
return -errno;
}
return 0;
}
int mknod_atomic(const char *path, mode_t mode, dev_t dev) {
_cleanup_free_ char *t = NULL;
int r;
assert(path);
r = tempfn_random(path, NULL, &t);
if (r < 0)
return r;
if (mknod(t, mode, dev) < 0)
return -errno;
if (rename(t, path) < 0) {
unlink_noerrno(t);
return -errno;
}
return 0;
}
int mkfifo_atomic(const char *path, mode_t mode) {
_cleanup_free_ char *t = NULL;
int r;
assert(path);
r = tempfn_random(path, NULL, &t);
if (r < 0)
return r;
if (mkfifo(t, mode) < 0)
return -errno;
if (rename(t, path) < 0) {
unlink_noerrno(t);
return -errno;
}
return 0;
}
int mkfifoat_atomic(int dirfd, const char *path, mode_t mode) {
_cleanup_free_ char *t = NULL;
int r;
assert(path);
if (path_is_absolute(path))
return mkfifo_atomic(path, mode);
/* We're only interested in the (random) filename. */
r = tempfn_random_child("", NULL, &t);
if (r < 0)
return r;
if (mkfifoat(dirfd, t, mode) < 0)
return -errno;
if (renameat(dirfd, t, dirfd, path) < 0) {
unlink_noerrno(t);
return -errno;
}
return 0;
}
int get_files_in_directory(const char *path, char ***list) {
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
size_t bufsize = 0, n = 0;
_cleanup_strv_free_ char **l = NULL;
assert(path);
/* Returns all files in a directory in *list, and the number
* of files as return value. If list is NULL returns only the
* number. */
d = opendir(path);
if (!d)
return -errno;
FOREACH_DIRENT_ALL(de, d, return -errno) {
dirent_ensure_type(d, de);
if (!dirent_is_file(de))
continue;
if (list) {
/* one extra slot is needed for the terminating NULL */
if (!GREEDY_REALLOC(l, bufsize, n + 2))
return -ENOMEM;
l[n] = strdup(de->d_name);
if (!l[n])
return -ENOMEM;
l[++n] = NULL;
} else
n++;
}
if (list)
*list = TAKE_PTR(l);
return n;
}
static int getenv_tmp_dir(const char **ret_path) {
const char *n;
int r, ret = 0;
assert(ret_path);
/* We use the same order of environment variables python uses in tempfile.gettempdir():
* https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
const char *e;
e = secure_getenv(n);
if (!e)
continue;
if (!path_is_absolute(e)) {
r = -ENOTDIR;
goto next;
}
if (!path_is_normalized(e)) {
r = -EPERM;
goto next;
}
r = is_dir(e, true);
if (r < 0)
goto next;
if (r == 0) {
r = -ENOTDIR;
goto next;
}
*ret_path = e;
return 1;
next:
/* Remember first error, to make this more debuggable */
if (ret >= 0)
ret = r;
}
if (ret < 0)
return ret;
*ret_path = NULL;
return ret;
}
static int tmp_dir_internal(const char *def, const char **ret) {
const char *e;
int r, k;
assert(def);
assert(ret);
r = getenv_tmp_dir(&e);
if (r > 0) {
*ret = e;
return 0;
}
k = is_dir(def, true);
if (k == 0)
k = -ENOTDIR;
if (k < 0)
return r < 0 ? r : k;
*ret = def;
return 0;
}
int var_tmp_dir(const char **ret) {
/* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
* even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
* returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
* making it a variable that overrides all temporary file storage locations. */
return tmp_dir_internal("/var/tmp", ret);
}
int tmp_dir(const char **ret) {
/* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
* backed by an in-memory file system: /tmp. */
return tmp_dir_internal("/tmp", ret);
}
int unlink_or_warn(const char *filename) {
if (unlink(filename) < 0 && errno != ENOENT)
/* If the file doesn't exist and the fs simply was read-only (in which
* case unlink() returns EROFS even if the file doesn't exist), don't
* complain */
if (errno != EROFS || access(filename, F_OK) >= 0)
return log_error_errno(errno, "Failed to remove \"%s\": %m", filename);
return 0;
}
int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
int wd;
/* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
xsprintf(path, "/proc/self/fd/%i", what);
wd = inotify_add_watch(fd, path, mask);
if (wd < 0)
return -errno;
return wd;
}
int inotify_add_watch_and_warn(int fd, const char *pathname, uint32_t mask) {
int wd;
wd = inotify_add_watch(fd, pathname, mask);
if (wd < 0) {
if (errno == ENOSPC)
return log_error_errno(errno, "Failed to add a watch for %s: inotify watch limit reached", pathname);
return log_error_errno(errno, "Failed to add a watch for %s: %m", pathname);
}
return wd;
}
static bool unsafe_transition(const struct stat *a, const struct stat *b) {
/* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to
* privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files
* making us believe we read something safe even though it isn't safe in the specific context we open it in. */
if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */
return false;
return a->st_uid != b->st_uid; /* Otherwise we need to stay within the same UID */
}
static int log_unsafe_transition(int a, int b, const char *path, unsigned flags) {
_cleanup_free_ char *n1 = NULL, *n2 = NULL;
if (!FLAGS_SET(flags, CHASE_WARN))
return -ENOLINK;
(void) fd_get_path(a, &n1);
(void) fd_get_path(b, &n2);
return log_warning_errno(SYNTHETIC_ERRNO(ENOLINK),
"Detected unsafe path transition %s %s %s during canonicalization of %s.",
strna(n1), special_glyph(SPECIAL_GLYPH_ARROW), strna(n2), path);
}
static int log_autofs_mount_point(int fd, const char *path, unsigned flags) {
_cleanup_free_ char *n1 = NULL;
if (!FLAGS_SET(flags, CHASE_WARN))
return -EREMOTE;
(void) fd_get_path(fd, &n1);
return log_warning_errno(SYNTHETIC_ERRNO(EREMOTE),
"Detected autofs mount point %s during canonicalization of %s.",
strna(n1), path);
}
int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret_path, int *ret_fd) {
_cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
_cleanup_close_ int fd = -1;
unsigned max_follow = CHASE_SYMLINKS_MAX; /* how many symlinks to follow before giving up and returning ELOOP */
struct stat previous_stat;
bool exists = true;
char *todo;
int r;
assert(path);
/* Either the file may be missing, or we return an fd to the final object, but both make no sense */
if ((flags & CHASE_NONEXISTENT) && ret_fd)
return -EINVAL;
if ((flags & CHASE_STEP) && ret_fd)
return -EINVAL;
if (isempty(path))
return -EINVAL;
/* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
* symlinks relative to a root directory, instead of the root of the host.
*
* Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
* relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
* assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
* prefixed accordingly.
*
* Algorithmically this operates on two path buffers: "done" are the components of the path we already
* processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
* process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
* each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
* slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
* to a minimum.
*
* Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
* as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
* function what to do when encountering a symlink with an absolute path as directory: prefix it by the
* specified path.
*
* There are five ways to invoke this function:
*
* 1. Without CHASE_STEP or ret_fd: in this case the path is resolved and the normalized path is
* returned in `ret_path`. The return value is < 0 on error. If CHASE_NONEXISTENT is also set, 0
* is returned if the file doesn't exist, > 0 otherwise. If CHASE_NONEXISTENT is not set, >= 0 is
* returned if the destination was found, -ENOENT if it wasn't.
*
* 2. With ret_fd: in this case the destination is opened after chasing it as O_PATH and this file
* descriptor is returned as return value. This is useful to open files relative to some root
* directory. Note that the returned O_PATH file descriptors must be converted into a regular one (using
* fd_reopen() or such) before it can be used for reading/writing. ret_fd may not be combined with
* CHASE_NONEXISTENT.
*
* 3. With CHASE_STEP: in this case only a single step of the normalization is executed, i.e. only the first
* symlink or ".." component of the path is resolved, and the resulting path is returned. This is useful if
* a caller wants to trace the path through the file system verbosely. Returns < 0 on error, > 0 if the
* path is fully normalized, and == 0 for each normalization step. This may be combined with
* CHASE_NONEXISTENT, in which case 1 is returned when a component is not found.
*
* 4. With CHASE_SAFE: in this case the path must not contain unsafe transitions, i.e. transitions from
* unprivileged to privileged files or directories. In such cases the return value is -ENOLINK. If
* CHASE_WARN is also set, a warning describing the unsafe transition is emitted.
*
* 5. With CHASE_NO_AUTOFS: in this case if an autofs mount point is encountered, path normalization
* is aborted and -EREMOTE is returned. If CHASE_WARN is also set, a warning showing the path of
* the mount point is emitted.
*/
/* A root directory of "/" or "" is identical to none */
if (empty_or_root(original_root))
original_root = NULL;
if (!original_root && !ret_path && !(flags & (CHASE_NONEXISTENT|CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_STEP)) && ret_fd) {
/* Shortcut the ret_fd case if the caller isn't interested in the actual path and has no root set
* and doesn't care about any of the other special features we provide either. */
r = open(path, O_PATH|O_CLOEXEC|((flags & CHASE_NOFOLLOW) ? O_NOFOLLOW : 0));
if (r < 0)
return -errno;
*ret_fd = r;
return 0;
}
if (original_root) {
r = path_make_absolute_cwd(original_root, &root);
if (r < 0)
return r;
/* Simplify the root directory, so that it has no duplicate slashes and nothing at the
* end. While we won't resolve the root path we still simplify it. Note that dropping the
* trailing slash should not change behaviour, since when opening it we specify O_DIRECTORY
* anyway. Moreover at the end of this function after processing everything we'll always turn
* the empty string back to "/". */
delete_trailing_chars(root, "/");
path_simplify(root, true);
if (flags & CHASE_PREFIX_ROOT) {
/* We don't support relative paths in combination with a root directory */
if (!path_is_absolute(path))
return -EINVAL;
path = prefix_roota(root, path);
}
}
r = path_make_absolute_cwd(path, &buffer);
if (r < 0)
return r;
fd = open(root ?: "/", O_CLOEXEC|O_DIRECTORY|O_PATH);
if (fd < 0)
return -errno;
if (flags & CHASE_SAFE) {
if (fstat(fd, &previous_stat) < 0)
return -errno;
}
if (root) {
_cleanup_free_ char *absolute = NULL;
const char *e;
/* If we are operating on a root directory, let's take the root directory as it is. */
e = path_startswith(buffer, root);
if (!e)
return log_full_errno(flags & CHASE_WARN ? LOG_WARNING : LOG_DEBUG,
SYNTHETIC_ERRNO(ECHRNG),
"Specified path '%s' is outside of specified root directory '%s', refusing to resolve.",
path, root);
done = strdup(root);
if (!done)
return -ENOMEM;
/* Make sure "todo" starts with a slash */
absolute = strjoin("/", e);
if (!absolute)
return -ENOMEM;
free_and_replace(buffer, absolute);
}
todo = buffer;
for (;;) {
_cleanup_free_ char *first = NULL;
_cleanup_close_ int child = -1;
struct stat st;
size_t n, m;
/* Determine length of first component in the path */
n = strspn(todo, "/"); /* The slashes */
if (n > 1) {
/* If we are looking at more than a single slash then skip all but one, so that when
* we are done with everything we have a normalized path with only single slashes
* separating the path components. */
todo += n - 1;
n = 1;
}
m = n + strcspn(todo + n, "/"); /* The entire length of the component */
/* Extract the first component. */
first = strndup(todo, m);
if (!first)
return -ENOMEM;
todo += m;
/* Empty? Then we reached the end. */
if (isempty(first))
break;
/* Just a single slash? Then we reached the end. */
if (path_equal(first, "/")) {
/* Preserve the trailing slash */
if (flags & CHASE_TRAIL_SLASH)
if (!strextend(&done, "/", NULL))
return -ENOMEM;
break;
}
/* Just a dot? Then let's eat this up. */
if (path_equal(first, "/."))
continue;
/* Two dots? Then chop off the last bit of what we already found out. */
if (path_equal(first, "/..")) {
_cleanup_free_ char *parent = NULL;
_cleanup_close_ int fd_parent = -1;
/* If we already are at the top, then going up will not change anything. This is in-line with
* how the kernel handles this. */
if (empty_or_root(done))
continue;
parent = dirname_malloc(done);
if (!parent)
return -ENOMEM;
/* Don't allow this to leave the root dir. */
if (root &&
path_startswith(done, root) &&
!path_startswith(parent, root))
continue;
free_and_replace(done, parent);
if (flags & CHASE_STEP)
goto chased_one;
fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (fd_parent < 0)
return -errno;
if (flags & CHASE_SAFE) {
if (fstat(fd_parent, &st) < 0)
return -errno;
if (unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(fd, fd_parent, path, flags);
previous_stat = st;
}
safe_close(fd);
fd = TAKE_FD(fd_parent);
continue;
}
/* Otherwise let's see what this is. */
child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (child < 0) {
if (errno == ENOENT &&
(flags & CHASE_NONEXISTENT) &&
(isempty(todo) || path_is_normalized(todo))) {
/* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
* what we got so far. But don't allow this if the remaining path contains "../ or "./"
* or something else weird. */
/* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
if (streq_ptr(done, "/"))
*done = '\0';
if (!strextend(&done, first, todo, NULL))
return -ENOMEM;
exists = false;
break;
}
return -errno;
}
if (fstat(child, &st) < 0)
return -errno;
if ((flags & CHASE_SAFE) &&
unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(fd, child, path, flags);
previous_stat = st;
if ((flags & CHASE_NO_AUTOFS) &&
fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0)
return log_autofs_mount_point(child, path, flags);
if (S_ISLNK(st.st_mode) && !((flags & CHASE_NOFOLLOW) && isempty(todo))) {
char *joined;
_cleanup_free_ char *destination = NULL;
/* This is a symlink, in this case read the destination. But let's make sure we don't follow
* symlinks without bounds. */
if (--max_follow <= 0)
return -ELOOP;
r = readlinkat_malloc(fd, first + n, &destination);
if (r < 0)
return r;
if (isempty(destination))
return -EINVAL;
if (path_is_absolute(destination)) {
/* An absolute destination. Start the loop from the beginning, but use the root
* directory as base. */
safe_close(fd);
fd = open(root ?: "/", O_CLOEXEC|O_DIRECTORY|O_PATH);
if (fd < 0)
return -errno;
if (flags & CHASE_SAFE) {
if (fstat(fd, &st) < 0)
return -errno;
if (unsafe_transition(&previous_stat, &st))
return log_unsafe_transition(child, fd, path, flags);
previous_stat = st;
}
free(done);
/* Note that we do not revalidate the root, we take it as is. */
if (isempty(root))
done = NULL;
else {
done = strdup(root);
if (!done)
return -ENOMEM;
}
/* Prefix what's left to do with what we just read, and start the loop again, but
* remain in the current directory. */
joined = path_join(destination, todo);
} else
joined = path_join("/", destination, todo);
if (!joined)
return -ENOMEM;
free(buffer);
todo = buffer = joined;
if (flags & CHASE_STEP)
goto chased_one;
continue;
}
/* If this is not a symlink, then let's just add the name we read to what we already verified. */
if (!done)
done = TAKE_PTR(first);
else {
/* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
if (streq(done, "/"))
*done = '\0';
if (!strextend(&done, first, NULL))
return -ENOMEM;
}
/* And iterate again, but go one directory further down. */
safe_close(fd);
fd = TAKE_FD(child);
}
if (!done) {
/* Special case, turn the empty string into "/", to indicate the root directory. */
done = strdup("/");
if (!done)
return -ENOMEM;
}
if (ret_path)
*ret_path = TAKE_PTR(done);
if (ret_fd) {
/* Return the O_PATH fd we currently are looking to the caller. It can translate it to a
* proper fd by opening /proc/self/fd/xyz. */
assert(fd >= 0);
*ret_fd = TAKE_FD(fd);
}
if (flags & CHASE_STEP)
return 1;
return exists;
chased_one:
if (ret_path) {
char *c;
c = strjoin(strempty(done), todo);
if (!c)
return -ENOMEM;
*ret_path = c;
}
return 0;
}
int chase_symlinks_and_open(
const char *path,
const char *root,
unsigned chase_flags,
int open_flags,
char **ret_path) {
_cleanup_close_ int path_fd = -1;
_cleanup_free_ char *p = NULL;
int r;
if (chase_flags & CHASE_NONEXISTENT)
return -EINVAL;
if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) {
/* Shortcut this call if none of the special features of this call are requested */
r = open(path, open_flags);
if (r < 0)
return -errno;
return r;
}
r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd);
if (r < 0)
return r;
assert(path_fd >= 0);
r = fd_reopen(path_fd, open_flags);
if (r < 0)
return r;
if (ret_path)
*ret_path = TAKE_PTR(p);
return r;
}
int chase_symlinks_and_opendir(
const char *path,
const char *root,
unsigned chase_flags,
char **ret_path,
DIR **ret_dir) {
char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
_cleanup_close_ int path_fd = -1;
_cleanup_free_ char *p = NULL;
DIR *d;
int r;
if (!ret_dir)
return -EINVAL;
if (chase_flags & CHASE_NONEXISTENT)
return -EINVAL;
if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) {
/* Shortcut this call if none of the special features of this call are requested */
d = opendir(path);
if (!d)
return -errno;
*ret_dir = d;
return 0;
}
r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd);
if (r < 0)
return r;
assert(path_fd >= 0);
xsprintf(procfs_path, "/proc/self/fd/%i", path_fd);
d = opendir(procfs_path);
if (!d)
return -errno;
if (ret_path)
*ret_path = TAKE_PTR(p);
*ret_dir = d;
return 0;
}
int chase_symlinks_and_stat(
const char *path,
const char *root,
unsigned chase_flags,
char **ret_path,
struct stat *ret_stat,
int *ret_fd) {
_cleanup_close_ int path_fd = -1;
_cleanup_free_ char *p = NULL;
int r;
assert(path);
assert(ret_stat);
if (chase_flags & CHASE_NONEXISTENT)
return -EINVAL;
if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) {
/* Shortcut this call if none of the special features of this call are requested */
if (stat(path, ret_stat) < 0)
return -errno;
return 1;
}
r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd);
if (r < 0)
return r;
assert(path_fd >= 0);
if (fstat(path_fd, ret_stat) < 0)
return -errno;
if (ret_path)
*ret_path = TAKE_PTR(p);
if (ret_fd)
*ret_fd = TAKE_FD(path_fd);
return 1;
}
int access_fd(int fd, int mode) {
char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1];
/* Like access() but operates on an already open fd */
xsprintf(p, "/proc/self/fd/%i", fd);
if (access(p, mode) < 0) {
if (errno != ENOENT)
return -errno;
/* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's
* make things debuggable and distinguish the two. */
if (proc_mounted() == 0)
return -ENOSYS; /* /proc is not available or not set up properly, we're most likely in some chroot
* environment. */
return -EBADF; /* The directory exists, hence it's the fd that doesn't. */
}
return 0;
}
void unlink_tempfilep(char (*p)[]) {
/* If the file is created with mkstemp(), it will (almost always)
* change the suffix. Treat this as a sign that the file was
* successfully created. We ignore both the rare case where the
* original suffix is used and unlink failures. */
if (!endswith(*p, ".XXXXXX"))
(void) unlink_noerrno(*p);
}
int unlinkat_deallocate(int fd, const char *name, UnlinkDeallocateFlags flags) {
_cleanup_close_ int truncate_fd = -1;
struct stat st;
off_t l, bs;
assert((flags & ~(UNLINK_REMOVEDIR|UNLINK_ERASE)) == 0);
/* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other
* link to it. This is useful to ensure that other processes that might have the file open for reading won't be
* able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up
* jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and
* returned to the free pool.
*
* Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (👊) if supported, which means
* the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other
* programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes
* underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.)
* However if hole punching is not implemented in the kernel or file system we'll fall back to normal file
* truncation (🔪), as our goal of deallocating the data space trumps our goal of being nice to readers (💐).
*
* Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the
* primary job – to delete the file – is accomplished. */
if (!FLAGS_SET(flags, UNLINK_REMOVEDIR)) {
truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK);
if (truncate_fd < 0) {
/* If this failed because the file doesn't exist propagate the error right-away. Also,
* AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is
* returned when this is a directory but we are not supposed to delete those, hence propagate
* the error right-away too. */
if (IN_SET(errno, ENOENT, EISDIR))
return -errno;
if (errno != ELOOP) /* don't complain if this is a symlink */
log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name);
}
}
if (unlinkat(fd, name, FLAGS_SET(flags, UNLINK_REMOVEDIR) ? AT_REMOVEDIR : 0) < 0)
return -errno;
if (truncate_fd < 0) /* Don't have a file handle, can't do more ☹ */
return 0;
if (fstat(truncate_fd, &st) < 0) {
log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name);
return 0;
}
if (!S_ISREG(st.st_mode))
return 0;
if (FLAGS_SET(flags, UNLINK_ERASE) && st.st_size > 0 && st.st_nlink == 0) {
uint64_t left = st.st_size;
char buffer[64 * 1024];
/* If erasing is requested, let's overwrite the file with random data once before deleting
* it. This isn't going to give you shred(1) semantics, but hopefully should be good enough
* for stuff backed by tmpfs at least.
*
* Note that we only erase like this if the link count of the file is zero. If it is higher it
* is still linked by someone else and we'll leave it to them to remove it securely
* eventually! */
random_bytes(buffer, sizeof(buffer));
while (left > 0) {
ssize_t n;
n = write(truncate_fd, buffer, MIN(sizeof(buffer), left));
if (n < 0) {
log_debug_errno(errno, "Failed to erase data in file '%s', ignoring.", name);
break;
}
assert(left >= (size_t) n);
left -= n;
}
/* Let's refresh metadata */
if (fstat(truncate_fd, &st) < 0) {
log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name);
return 0;
}
}
/* Don't dallocate if there's nothing to deallocate or if the file is linked elsewhere */
if (st.st_blocks == 0 || st.st_nlink > 0)
return 0;
/* If this is a regular file, it actually took up space on disk and there are no other links it's time to
* punch-hole/truncate this to release the disk space. */
bs = MAX(st.st_blksize, 512);
l = DIV_ROUND_UP(st.st_size, bs) * bs; /* Round up to next block size */
if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0)
return 0; /* Successfully punched a hole! 😊 */
/* Fall back to truncation */
if (ftruncate(truncate_fd, 0) < 0) {
log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m");
return 0;
}
return 0;
}
int fsync_directory_of_file(int fd) {
_cleanup_free_ char *path = NULL;
_cleanup_close_ int dfd = -1;
int r;
r = fd_verify_regular(fd);
if (r < 0)
return r;
r = fd_get_path(fd, &path);
if (r < 0) {
log_debug_errno(r, "Failed to query /proc/self/fd/%d%s: %m",
fd,
r == -ENOSYS ? ", ignoring" : "");
if (r == -ENOSYS)
/* If /proc is not available, we're most likely running in some
* chroot environment, and syncing the directory is not very
* important in that case. Let's just silently do nothing. */
return 0;
return r;
}
if (!path_is_absolute(path))
return -EINVAL;
dfd = open_parent(path, O_CLOEXEC, 0);
if (dfd < 0)
return dfd;
if (fsync(dfd) < 0)
return -errno;
return 0;
}
int fsync_full(int fd) {
int r, q;
/* Sync both the file and the directory */
r = fsync(fd) < 0 ? -errno : 0;
q = fsync_directory_of_file(fd);
return r < 0 ? r : q;
}
int fsync_path_at(int at_fd, const char *path) {
_cleanup_close_ int opened_fd = -1;
int fd;
if (isempty(path)) {
if (at_fd == AT_FDCWD) {
opened_fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC);
if (opened_fd < 0)
return -errno;
fd = opened_fd;
} else
fd = at_fd;
} else {
opened_fd = openat(at_fd, path, O_RDONLY|O_CLOEXEC);
if (opened_fd < 0)
return -errno;
fd = opened_fd;
}
if (fsync(fd) < 0)
return -errno;
return 0;
}
int syncfs_path(int atfd, const char *path) {
_cleanup_close_ int fd = -1;
assert(path);
fd = openat(atfd, path, O_CLOEXEC|O_RDONLY|O_NONBLOCK);
if (fd < 0)
return -errno;
if (syncfs(fd) < 0)
return -errno;
return 0;
}
int open_parent(const char *path, int flags, mode_t mode) {
_cleanup_free_ char *parent = NULL;
int fd;
if (isempty(path))
return -EINVAL;
if (path_equal(path, "/")) /* requesting the parent of the root dir is fishy, let's prohibit that */
return -EINVAL;
parent = dirname_malloc(path);
if (!parent)
return -ENOMEM;
/* Let's insist on O_DIRECTORY since the parent of a file or directory is a directory. Except if we open an
* O_TMPFILE file, because in that case we are actually create a regular file below the parent directory. */
if (FLAGS_SET(flags, O_PATH))
flags |= O_DIRECTORY;
else if (!FLAGS_SET(flags, O_TMPFILE))
flags |= O_DIRECTORY|O_RDONLY;
fd = open(parent, flags, mode);
if (fd < 0)
return -errno;
return fd;
}
static int blockdev_is_encrypted(const char *sysfs_path, unsigned depth_left) {
_cleanup_free_ char *p = NULL, *uuids = NULL;
_cleanup_closedir_ DIR *d = NULL;
int r, found_encrypted = false;
assert(sysfs_path);
if (depth_left == 0)
return -EINVAL;
p = path_join(sysfs_path, "dm/uuid");
if (!p)
return -ENOMEM;
r = read_one_line_file(p, &uuids);
if (r != -ENOENT) {
if (r < 0)
return r;
/* The DM device's uuid attribute is prefixed with "CRYPT-" if this is a dm-crypt device. */
if (startswith(uuids, "CRYPT-"))
return true;
}
/* Not a dm-crypt device itself. But maybe it is on top of one? Follow the links in the "slaves/"
* subdir. */
p = mfree(p);
p = path_join(sysfs_path, "slaves");
if (!p)
return -ENOMEM;
d = opendir(p);
if (!d) {
if (errno == ENOENT) /* Doesn't have underlying devices */
return false;
return -errno;
}
for (;;) {
_cleanup_free_ char *q = NULL;
struct dirent *de;
errno = 0;
de = readdir_no_dot(d);
if (!de) {
if (errno != 0)
return -errno;
break; /* No more underlying devices */
}
q = path_join(p, de->d_name);
if (!q)
return -ENOMEM;
r = blockdev_is_encrypted(q, depth_left - 1);
if (r < 0)
return r;
if (r == 0) /* we found one that is not encrypted? then propagate that immediately */
return false;
found_encrypted = true;
}
return found_encrypted;
}
int path_is_encrypted(const char *path) {
char p[SYS_BLOCK_PATH_MAX(NULL)];
dev_t devt;
int r;
r = get_block_device(path, &devt);
if (r < 0)
return r;
if (r == 0) /* doesn't have a block device */
return false;
xsprintf_sys_block_path(p, NULL, devt);
return blockdev_is_encrypted(p, 10 /* safety net: maximum recursion depth */);
}