X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fbasic%2Ffs-util.c;h=4d494650cb916cfcd3fa697cb2884449d44f331a;hb=8622c1b84e198fb2d0626e622dfeaaa446e38f3a;hp=b97edb552c067c7b10b0c805e3aa7ccd8e2efad1;hpb=7b987da65ad4eacb30034519653a61457b688352;p=elogind.git

diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index b97edb552..4d494650c 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -236,7 +236,7 @@ int readlink_and_canonicalize(const char *p, const char *root, char **ret) {
         if (r < 0)
                 return r;
 
-        r = chase_symlinks(t, root, &s);
+        r = chase_symlinks(t, root, 0, &s);
         if (r < 0)
                 /* If we can't follow up, then let's return the original string, slightly cleaned up. */
                 *ret = path_kill_slashes(t);
@@ -603,10 +603,11 @@ int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
         return r;
 }
 
-int chase_symlinks(const char *path, const char *_root, char **ret) {
+int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) {
         _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
         _cleanup_close_ int fd = -1;
         unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
+        bool exists = true;
         char *todo;
         int r;
 
@@ -616,8 +617,9 @@ int chase_symlinks(const char *path, const char *_root, char **ret) {
          * 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
-         * shall *not* be prefixed by it.
+         * 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
@@ -634,16 +636,19 @@ int chase_symlinks(const char *path, const char *_root, char **ret) {
          * Note: there's also chase_symlinks_prefix() (see below), which as first step prefixes the passed path by the
          * passed root. */
 
-        r = path_make_absolute_cwd(path, &buffer);
-        if (r < 0)
-                return r;
-
-        if (_root) {
-                r = path_make_absolute_cwd(_root, &root);
+        if (original_root) {
+                r = path_make_absolute_cwd(original_root, &root);
                 if (r < 0)
                         return r;
+
+                if (flags & CHASE_PREFIX_ROOT)
+                        path = prefix_roota(root, path);
         }
 
+        r = path_make_absolute_cwd(path, &buffer);
+        if (r < 0)
+                return r;
+
         fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
         if (fd < 0)
                 return -errno;
@@ -708,8 +713,25 @@ int chase_symlinks(const char *path, const char *_root, char **ret) {
 
                 /* Otherwise let's see what this is. */
                 child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
-                if (child < 0)
+                if (child < 0) {
+
+                        if (errno == ENOENT &&
+                            (flags & CHASE_NONEXISTENT) &&
+                            (isempty(todo) || path_is_safe(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 (!strextend(&done, first, todo, NULL))
+                                        return -ENOMEM;
+
+                                exists = false;
+                                break;
+                        }
+
                         return -errno;
+                }
 
                 if (fstat(child, &st) < 0)
                         return -errno;
@@ -794,16 +816,6 @@ int chase_symlinks(const char *path, const char *_root, char **ret) {
         *ret = done;
         done = NULL;
 
-        return 0;
+        return exists;
 }
 #endif // 0
-
-int chase_symlinks_prefix(const char *path, const char *root, char **ret) {
-        const char *t;
-
-        /* Same as chase_symlinks(), but prefixes 'path' by 'root' first. */
-
-        t = prefix_roota(root, path);
-
-        return chase_symlinks(t, root, ret);
-}