diff options
Diffstat (limited to 'src/basic/fs-util.c')
| -rw-r--r-- | src/basic/fs-util.c | 102 |
1 files changed, 63 insertions, 39 deletions
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c index d2c322a0de..5b23269109 100644 --- a/src/basic/fs-util.c +++ b/src/basic/fs-util.c @@ -17,7 +17,6 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ -#include <dirent.h> #include <errno.h> #include <stddef.h> #include <stdio.h> @@ -224,25 +223,25 @@ int readlink_and_make_absolute(const char *p, char **r) { return 0; } -int readlink_and_canonicalize(const char *p, char **r) { +int readlink_and_canonicalize(const char *p, const char *root, char **ret) { char *t, *s; - int j; + int r; assert(p); - assert(r); + assert(ret); - j = readlink_and_make_absolute(p, &t); - if (j < 0) - return j; + r = readlink_and_make_absolute(p, &t); + if (r < 0) + return r; - s = canonicalize_file_name(t); - if (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); + else { + *ret = s; free(t); - *r = s; - } else - *r = t; - - path_kill_slashes(*r); + } return 0; } @@ -446,6 +445,7 @@ int mkfifo_atomic(const char *path, mode_t mode) { 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; @@ -459,16 +459,7 @@ int get_files_in_directory(const char *path, char ***list) { if (!d) return -errno; - for (;;) { - struct dirent *de; - - errno = 0; - de = readdir(d); - if (!de && errno > 0) - return -errno; - if (!de) - break; - + FOREACH_DIRENT_ALL(de, d, return -errno) { dirent_ensure_type(d, de); if (!dirent_is_file(de)) @@ -598,10 +589,11 @@ 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; @@ -610,26 +602,39 @@ int chase_symlinks(const char *path, const char *_root, char **ret) { /* 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" matters only if we encounter an absolute symlink, it's unused otherwise. Most importantly - * this means the path parameter passed in is not prefixed by it. + * 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 - * at a minimum. */ - - r = path_make_absolute_cwd(path, &buffer); - if (r < 0) - return r; + * at 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. + * + * Note: there's also chase_symlinks_prefix() (see below), which as first step prefixes the passed path by the + * passed root. */ - 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; @@ -665,18 +670,20 @@ int chase_symlinks(const char *path, const char *_root, char **ret) { _cleanup_free_ char *parent = NULL; 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 (isempty(done) || path_equal(done, "/")) - return -EINVAL; + continue; parent = dirname_malloc(done); if (!parent) return -ENOMEM; - /* Don't allow this to leave the root dir */ + /* Don't allow this to leave the root dir. */ if (root && path_startswith(done, root) && !path_startswith(parent, root)) - return -EINVAL; + continue; free_and_replace(done, parent); @@ -692,8 +699,25 @@ 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; @@ -778,5 +802,5 @@ int chase_symlinks(const char *path, const char *_root, char **ret) { *ret = done; done = NULL; - return 0; + return exists; } |