strna(n1), path);
}
-int chase_symlinks(
+int chase_symlinks_at(
+ int dir_fd,
const char *path,
- const char *original_root,
ChaseSymlinksFlags flags,
char **ret_path,
int *ret_fd) {
- _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
- _cleanup_close_ int fd = -1;
+ _cleanup_free_ char *buffer = NULL, *done = NULL;
+ _cleanup_close_ int fd = -1, root_fd = -1;
unsigned max_follow = CHASE_SYMLINKS_MAX; /* how many symlinks to follow before giving up and returning ELOOP */
bool exists = true, append_trail_slash = false;
struct stat previous_stat;
int r;
assert(path);
+ assert(!FLAGS_SET(flags, CHASE_PREFIX_ROOT));
+ assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
/* 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 (isempty(path))
- return -EINVAL;
+ path = ".";
- /* 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.
+ /* This function resolves symlinks of the path relative to the given directory file descriptor. If
+ * CHASE_SYMLINKS_RESOLVE_IN_ROOT is specified, symlinks are resolved relative to the given directory
+ * file descriptor. Otherwise, they are resolved relative to the root directory 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.
+ * Note that when CHASE_SYMLINKS_RESOLVE_IN_ROOT is specified and we find an absolute symlink, it is
+ * resolved relative to given directory file descriptor and not the root of the host. Also, when
+ * following relative symlinks, this functions ensure they cannot be used to "escape" the given
+ * directory file descriptor. The "path" parameter is always interpreted relative to the given
+ * directory file descriptor. If the given directory file descriptor is AT_FDCWD and "path" is
+ * absolute, it is interpreted relative to the root directory of the host.
*
- * 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.
+ * If "dir_fd" is a valid directory fd, "path" is an absolute path and "ret_path" is not NULL, this
+ * functions returns a relative path in "ret_path" because openat() like functions generally ignore
+ * the directory fd if they are provided with an absolute path. On the other hand, if "dir_fd" is
+ * AT_FDCWD and "path" is an absolute path, we need to return an absolute path in "ret_path" because
+ * otherwise, if the caller passes the returned relative path to another openat() like function, it
+ * would be resolved relative to the current working directory instead of to "/".
*
- * 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.
+ * 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. 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
+ * "dir_fd" parameter to tell this function what to do when encountering a symlink with an absolute
+ * path as directory: resolve it relative to the given directory file descriptor.
*
* There are five ways to invoke this function:
*
*
* 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.
+ * 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.
+ * 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. CHASE_WARN cannot
- * be used in PID 1.
+ * 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.
+ * CHASE_WARN cannot be used in PID 1.
*
* 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. CHASE_WARN cannot be used in PID 1.
*/
- /* A root directory of "/" or "" is identical to none */
- if (empty_or_root(original_root))
- original_root = NULL;
+ if (!(flags & (CHASE_AT_RESOLVE_IN_ROOT|CHASE_NONEXISTENT|CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_STEP)) &&
+ !ret_path && ret_fd) {
- 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));
+ /* 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 = openat(dir_fd, path, O_PATH|O_CLOEXEC|((flags & CHASE_NOFOLLOW) ? O_NOFOLLOW : 0));
if (r < 0)
return -errno;
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);
+ buffer = strdup(path);
+ if (!buffer)
+ return -ENOMEM;
- if (flags & CHASE_PREFIX_ROOT) {
- buffer = path_join(root, path);
- if (!buffer)
- return -ENOMEM;
- }
+ bool need_absolute = !FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT) && path_is_absolute(path);
+ if (need_absolute) {
+ done = strdup("/");
+ if (!done)
+ return -ENOMEM;
}
- if (!buffer) {
- r = path_make_absolute_cwd(path, &buffer);
- if (r < 0)
- return r;
- }
+ if (FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT))
+ root_fd = openat(dir_fd, ".", O_CLOEXEC|O_DIRECTORY|O_PATH);
+ else
+ root_fd = open("/", O_CLOEXEC|O_DIRECTORY|O_PATH);
+ if (root_fd < 0)
+ return -errno;
- fd = open(empty_to_root(root), O_CLOEXEC|O_DIRECTORY|O_PATH);
+ if (FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT) || !path_is_absolute(path))
+ fd = openat(dir_fd, ".", O_CLOEXEC|O_DIRECTORY|O_PATH);
+ else
+ fd = open("/", O_CLOEXEC|O_DIRECTORY|O_PATH);
if (fd < 0)
return -errno;
- if (flags & CHASE_SAFE)
- if (fstat(fd, &previous_stat) < 0)
- return -errno;
+ if (fstat(fd, &previous_stat) < 0)
+ return -errno;
if (flags & CHASE_TRAIL_SLASH)
append_trail_slash = endswith(buffer, "/") || endswith(buffer, "/.");
- if (root) {
- /* If we are operating on a root directory, let's take the root directory as it is. */
-
- todo = path_startswith(buffer, root);
- if (!todo)
- 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);
- } else {
- todo = buffer;
- done = strdup("/");
- }
- if (!done)
- return -ENOMEM;
-
- for (;;) {
+ for (todo = buffer;;) {
_cleanup_free_ char *first = NULL;
_cleanup_close_ int child = -1;
struct stat st;
_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))
+ /* 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) && FLAGS_SET(flags, CHASE_AT_RESOLVE_IN_ROOT))
continue;
- r = path_extract_directory(done, &parent);
- if (r < 0)
- return r;
+ fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH|O_DIRECTORY);
+ if (fd_parent < 0)
+ return -errno;
+
+ if (fstat(fd_parent, &st) < 0)
+ return -errno;
- /* Don't allow this to leave the root dir. */
- if (root &&
- path_startswith(done, root) &&
- !path_startswith(parent, root))
+ /* If we opened the same directory, that means we're at the host root directory, so
+ * going up won't change anything. */
+ if (st.st_dev == previous_stat.st_dev && st.st_ino == previous_stat.st_ino)
continue;
- free_and_replace(done, parent);
+ r = path_extract_directory(done, &parent);
+ if (r >= 0 || r == -EDESTADDRREQ)
+ free_and_replace(done, parent);
+ else if (IN_SET(r, -EINVAL, -EADDRNOTAVAIL)) {
+ /* If we're at the top of "dir_fd", start appending ".." to "done". */
+ if (!path_extend(&done, ".."))
+ return -ENOMEM;
+ } else
+ return r;
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);
if (path_is_absolute(destination)) {
- /* An absolute destination. Start the loop from the beginning, but use the root
- * directory as base. */
+ /* An absolute destination. Start the loop from the beginning, but use the
+ * root file descriptor as base. */
safe_close(fd);
- fd = open(empty_to_root(root), O_CLOEXEC|O_DIRECTORY|O_PATH);
+ fd = fd_reopen(root_fd, O_CLOEXEC|O_PATH|O_DIRECTORY);
if (fd < 0)
- return -errno;
+ return fd;
if (flags & CHASE_SAFE) {
if (fstat(fd, &st) < 0)
previous_stat = st;
}
- /* Note that we do not revalidate the root, we take it as is. */
- r = free_and_strdup(&done, empty_to_root(root));
+ r = free_and_strdup(&done, need_absolute ? "/" : NULL);
if (r < 0)
return r;
}
return 0;
}
+int chase_symlinks(
+ const char *path,
+ const char *original_root,
+ ChaseSymlinksFlags flags,
+ char **ret_path,
+ int *ret_fd) {
+
+ _cleanup_free_ char *root = NULL, *absolute = NULL, *p = NULL;
+ _cleanup_close_ int fd = -1, pfd = -1;
+ int r;
+
+ assert(path);
+
+ if (isempty(path))
+ return -EINVAL;
+
+ /* A root directory of "/" or "" is identical to none */
+ if (empty_or_root(original_root))
+ original_root = NULL;
+
+ 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);
+
+ if (flags & CHASE_PREFIX_ROOT) {
+ absolute = path_join(root, path);
+ if (!absolute)
+ return -ENOMEM;
+ }
+ }
+
+ if (!absolute) {
+ r = path_make_absolute_cwd(path, &absolute);
+ if (r < 0)
+ return r;
+ }
+
+ if (root) {
+ path = path_startswith(absolute, root);
+ if (!path)
+ 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.",
+ absolute, root);
+ }
+
+ if (root) {
+ fd = open(root, O_CLOEXEC|O_DIRECTORY|O_PATH);
+ if (fd < 0)
+ return -errno;
+
+ flags |= CHASE_AT_RESOLVE_IN_ROOT;
+ } else
+ fd = AT_FDCWD;
+
+ r = chase_symlinks_at(fd, path, flags & ~CHASE_PREFIX_ROOT, ret_path ? &p : NULL, ret_fd ? &pfd : NULL);
+ if (r < 0)
+ return r;
+
+ if (ret_path) {
+ char *q = path_join(root, p);
+ if (!q)
+ return -ENOMEM;
+
+ *ret_path = TAKE_PTR(q);
+ }
+
+ if (ret_fd)
+ *ret_fd = TAKE_FD(pfd);
+
+ return r;
+}
+
int chase_symlinks_and_open(
const char *path,
const char *root,
projects / thirdparty / systemd.git / commitdiff
