From 2f9ee3163c44a71c99fe104daf01d4d9ab51d2c9 Mon Sep 17 00:00:00 2001
From: Jan Synacek <jsynacek@redhat.com>
Date: Mon, 28 May 2018 10:52:52 +0200
Subject: [PATCH] tmpfiles: use safe_glob()

This filters out "." and ".." from glob results. Fixes #5655 and #5644.

Any judgements on whether the path is "safe" are removed. We will not remove
"/" under any name (including "/../" and such), but we will remove stuff that
is specified using paths that include "//", "/./" and "/../". Such paths can be
created when joining strings automatically, or for other reasons, and people
generally know what ".." and "." is.

Tests are added to make sure that the helper functions behave as expected.

Original commit: 84e72b5ef445ffb256bc4add4209c4c9c9855206
Resolves: #1436004
---
 src/shared/util.c       | 63 +++++++++++++++++++++++++++++++++++++++--
 src/shared/util.h       |  2 ++
 src/tmpfiles/tmpfiles.c | 11 ++-----
 3 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/src/shared/util.c b/src/shared/util.c
index 3216f004a..78967103a 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -49,7 +49,6 @@
 #include <dlfcn.h>
 #include <sys/wait.h>
 #include <sys/time.h>
-#include <glob.h>
 #include <grp.h>
 #include <sys/mman.h>
 #include <sys/vfs.h>
@@ -3370,7 +3369,7 @@ static int rm_rf_internal(const char *path, bool only_dirs, bool delete_root, bo
         /* We refuse to clean the root file system with this
          * call. This is extra paranoia to never cause a really
          * seriously broken system. */
-        if (path_equal(path, "/")) {
+        if (path_equal_or_files_same(path, "/")) {
                 log_error("Attempted to remove entire root file system, and we can't allow that.");
                 return -EPERM;
         }
@@ -5096,6 +5095,66 @@ int in_group(const char *name) {
         return in_gid(gid);
 }
 
+static void closedir_wrapper(void* v) {
+        (void) closedir(v);
+}
+
+static bool dot_or_dot_dot(const char *path) {
+        if (!path)
+                return false;
+        if (path[0] != '.')
+                return false;
+        if (path[1] == 0)
+                return true;
+        if (path[1] != '.')
+                return false;
+
+        return path[2] == 0;
+}
+
+static struct dirent* readdir_no_dot(DIR *dirp) {
+        struct dirent* d;
+
+        for (;;) {
+                d = readdir(dirp);
+                if (d && dot_or_dot_dot(d->d_name))
+                        continue;
+                return d;
+        }
+}
+
+int safe_glob(const char *path, int flags, glob_t *pglob) {
+        int k;
+
+        /* We want to set GLOB_ALTDIRFUNC ourselves, don't allow it to be set. */
+        assert(!(flags & GLOB_ALTDIRFUNC));
+
+        if (!pglob->gl_closedir)
+                pglob->gl_closedir = closedir_wrapper;
+        if (!pglob->gl_readdir)
+                pglob->gl_readdir = (struct dirent *(*)(void *)) readdir_no_dot;
+        if (!pglob->gl_opendir)
+                pglob->gl_opendir = (void *(*)(const char *)) opendir;
+        if (!pglob->gl_lstat)
+                pglob->gl_lstat = lstat;
+        if (!pglob->gl_stat)
+                pglob->gl_stat = stat;
+
+        errno = 0;
+        k = glob(path, flags | GLOB_ALTDIRFUNC, NULL, pglob);
+
+        if (k == GLOB_NOMATCH)
+                return -ENOENT;
+        if (k == GLOB_NOSPACE)
+                return -ENOMEM;
+        if (k != 0)
+                return errno > 0 ? -errno : -EIO;
+        if (strv_isempty(pglob->gl_pathv))
+                return -ENOENT;
+
+        return 0;
+}
+
 int glob_exists(const char *path) {
         _cleanup_globfree_ glob_t g = {};
         int k;
diff --git a/src/shared/util.h b/src/shared/util.h
index 998f882bb..cf096aa07 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -44,6 +44,7 @@
 #include <mntent.h>
 #include <sys/socket.h>
 #include <sys/inotify.h>
+#include <glob.h>
 
 #if SIZEOF_PID_T == 4
 #  define PID_PRI PRIi32
@@ -595,6 +596,7 @@ char* gid_to_name(gid_t gid);
 
 int glob_exists(const char *path);
 int glob_extend(char ***strv, const char *path);
+int safe_glob(const char *path, int flags, glob_t *pglob);
 
 int dirent_ensure_type(DIR *d, struct dirent *de);
 
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 5212d72f5..8a75efb22 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -1095,19 +1095,14 @@ static int item_do_children(Item *i, const char *path, action_t action) {
 
 static int glob_item(Item *i, action_t action, bool recursive) {
         _cleanup_globfree_ glob_t g = {
-                .gl_closedir = (void (*)(void *)) closedir,
-                .gl_readdir = (struct dirent *(*)(void *)) readdir,
                 .gl_opendir = (void *(*)(const char *)) opendir_nomod,
-                .gl_lstat = lstat,
-                .gl_stat = stat,
         };
         int r = 0, k;
         char **fn;
 
-        errno = 0;
-        k = glob(i->path, GLOB_NOSORT|GLOB_BRACE|GLOB_ALTDIRFUNC, NULL, &g);
-        if (k != 0 && k != GLOB_NOMATCH)
-                return log_error_errno(errno ?: EIO, "glob(%s) failed: %m", i->path);
+        k = safe_glob(i->path, GLOB_NOSORT|GLOB_BRACE, &g);
+        if (k < 0 && k != -ENOENT)
+                return log_error_errno(k, "glob(%s) failed: %m", i->path);
 
         STRV_FOREACH(fn, g.gl_pathv) {
                 k = action(i, *fn);