1 files changed, 174 insertions, 0 deletions
diff --git a/src/shared/chown-recursive.c b/src/shared/chown-recursive.c
new file mode 100644
index 0000000..bbc270d
--- /dev/null
+++ b/src/shared/chown-recursive.c
@@ -0,0 +1,174 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/xattr.h>
+
+#include "chown-recursive.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "macro.h"
+#include "stdio-util.h"
+#include "strv.h"
+#include "user-util.h"
+
+static int chown_one(
+                int fd,
+                const struct stat *st,
+                uid_t uid,
+                gid_t gid,
+                mode_t mask) {
+
+        int r;
+
+        assert(fd >= 0);
+        assert(st);
+
+        /* We change ACLs through the /proc/self/fd/%i path, so that we have a stable reference that works
+         * with O_PATH. */
+
+        /* Drop any ACL if there is one */
+        FOREACH_STRING(n, "system.posix_acl_access", "system.posix_acl_default")
+                if (removexattr(FORMAT_PROC_FD_PATH(fd), n) < 0)
+                        if (!ERRNO_IS_XATTR_ABSENT(errno))
+                                return -errno;
+
+        r = fchmod_and_chown(fd, st->st_mode & mask, uid, gid);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int chown_recursive_internal(
+                int fd,
+                const struct stat *st,
+                uid_t uid,
+                gid_t gid,
+                mode_t mask) {
+
+        _cleanup_closedir_ DIR *d = NULL;
+        bool changed = false;
+        int r;
+
+        assert(fd >= 0);
+        assert(st);
+
+        d = fdopendir(fd);
+        if (!d) {
+                safe_close(fd);
+                return -errno;
+        }
+
+        FOREACH_DIRENT_ALL(de, d, return -errno) {
+                _cleanup_close_ int path_fd = -1;
+                struct stat fst;
+
+                if (dot_or_dot_dot(de->d_name))
+                        continue;
+
+                /* Let's pin the child inode we want to fix now with an O_PATH fd, so that it cannot be swapped out
+                 * while we manipulate it. */
+                path_fd = openat(dirfd(d), de->d_name, O_PATH|O_CLOEXEC|O_NOFOLLOW);
+                if (path_fd < 0)
+                        return -errno;
+
+                if (fstat(path_fd, &fst) < 0)
+                        return -errno;
+
+                if (S_ISDIR(fst.st_mode)) {
+                        int subdir_fd;
+
+                        /* Convert it to a "real" (i.e. non-O_PATH) fd now */
+                        subdir_fd = fd_reopen(path_fd, O_RDONLY|O_CLOEXEC|O_NOATIME);
+                        if (subdir_fd < 0)
+                                return subdir_fd;
+
+                        r = chown_recursive_internal(subdir_fd, &fst, uid, gid, mask); /* takes possession of subdir_fd even on failure */
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                changed = true;
+                } else {
+                        r = chown_one(path_fd, &fst, uid, gid, mask);
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                changed = true;
+                }
+        }
+
+        r = chown_one(dirfd(d), st, uid, gid, mask);
+        if (r < 0)
+                return r;
+
+        return r > 0 || changed;
+}
+
+int path_chown_recursive(
+                const char *path,
+                uid_t uid,
+                gid_t gid,
+                mode_t mask) {
+
+        _cleanup_close_ int fd = -1;
+        struct stat st;
+
+        fd = open(path, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
+        if (fd < 0)
+                return -errno;
+
+        if (!uid_is_valid(uid) && !gid_is_valid(gid) && FLAGS_SET(mask, 07777))
+                return 0; /* nothing to do */
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        /* Let's take a shortcut: if the top-level directory is properly owned, we don't descend into the
+         * whole tree, under the assumption that all is OK anyway. */
+        if ((!uid_is_valid(uid) || st.st_uid == uid) &&
+            (!gid_is_valid(gid) || st.st_gid == gid) &&
+            ((st.st_mode & ~mask & 07777) == 0))
+                return 0;
+
+        return chown_recursive_internal(TAKE_FD(fd), &st, uid, gid, mask); /* we donate the fd to the call, regardless if it succeeded or failed */
+}
+
+int fd_chown_recursive(
+                int fd,
+                uid_t uid,
+                gid_t gid,
+                mode_t mask) {
+
+        int duplicated_fd = -1;
+        struct stat st;
+
+        /* Note that the slightly different order of fstat() and the checks here and in
+         * path_chown_recursive(). That's because when we open the directory ourselves we can specify
+         * O_DIRECTORY and we always want to ensure we are operating on a directory before deciding whether
+         * the operation is otherwise redundant. */
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!S_ISDIR(st.st_mode))
+                return -ENOTDIR;
+
+        if (!uid_is_valid(uid) && !gid_is_valid(gid) && FLAGS_SET(mask, 07777))
+                return 0; /* nothing to do */
+
+        /* Shortcut, as above */
+        if ((!uid_is_valid(uid) || st.st_uid == uid) &&
+            (!gid_is_valid(gid) || st.st_gid == gid) &&
+            ((st.st_mode & ~mask & 07777) == 0))
+                return 0;
+
+        /* Let's duplicate the fd here, as opendir() wants to take possession of it and close it afterwards */
+        duplicated_fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+        if (duplicated_fd < 0)
+                return -errno;
+
+        return chown_recursive_internal(duplicated_fd, &st, uid, gid, mask); /* fd donated even on failure */
+}