From b0ee8d82e470a6365bf7201cfd093f7b953ec899 Mon Sep 17 00:00:00 2001
From: Vaibhav Rustagi <vaibhavrustagi@google.com>
Date: Tue, 21 Sep 2021 15:56:04 -0700
Subject: [PATCH] Fixes for CVE-2021-28153.

Cherry-pick from
https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1982/diffs?commit_id=317b3b587058a05dca95d56dac26568c5b098d33
---
 gio/glocalfileoutputstream.c |  20 +++++--
 gio/tests/file.c             | 112 ++++++++++++++++++++++++++++++++++-
 2 files changed, 124 insertions(+), 8 deletions(-)

diff --git a/gio/glocalfileoutputstream.c b/gio/glocalfileoutputstream.c
index f34c3e439..f04180095 100644
--- a/gio/glocalfileoutputstream.c
+++ b/gio/glocalfileoutputstream.c
@@ -63,6 +63,12 @@
 #define O_BINARY 0
 #endif
 
+#ifndef O_CLOEXEC
+#define O_CLOEXEC 0
+#else
+#define HAVE_O_CLOEXEC 1
+#endif
+
 struct _GLocalFileOutputStreamPrivate {
   char *tmp_filename;
   char *original_filename;
@@ -850,6 +856,7 @@ handle_overwrite_open (const char    *filename,
   int res;
   int mode;
   int errsv;
+  gboolean replace_destination_set = (flags & G_FILE_CREATE_REPLACE_DESTINATION);
 
   mode = mode_from_flags_or_info (flags, reference_info);
 
@@ -960,7 +967,7 @@ handle_overwrite_open (const char    *filename,
    * to a backup file and rewrite the contents of the file.
    */
   
-  if ((flags & G_FILE_CREATE_REPLACE_DESTINATION) ||
+  if (replace_destination_set ||
       (!(_g_stat_nlink (&original_stat) > 1) && !is_symlink))
     {
       char *dirname, *tmp_filename;
@@ -979,7 +986,7 @@ handle_overwrite_open (const char    *filename,
       
       /* try to keep permissions (unless replacing) */
 
-      if ( ! (flags & G_FILE_CREATE_REPLACE_DESTINATION) &&
+      if ( !replace_destination_set &&
 	   (
 #ifdef HAVE_FCHOWN
 	    fchown (tmpfd, _g_stat_uid (&original_stat), _g_stat_gid (&original_stat)) == -1 ||
@@ -1120,7 +1127,7 @@ handle_overwrite_open (const char    *filename,
 	}
     }
 
-  if (flags & G_FILE_CREATE_REPLACE_DESTINATION)
+  if (replace_destination_set)
     {
       g_close (fd, NULL);
       
@@ -1205,7 +1212,7 @@ _g_local_file_output_stream_replace (const char        *filename,
   sync_on_close = FALSE;
 
   /* If the file doesn't exist, create it */
-  open_flags = O_CREAT | O_EXCL | O_BINARY;
+  open_flags = O_CREAT | O_EXCL | O_BINARY | O_CLOEXEC;
   if (readable)
     open_flags |= O_RDWR;
   else
@@ -1235,7 +1242,10 @@ _g_local_file_output_stream_replace (const char        *filename,
       set_error_from_open_errno (filename, error);
       return NULL;
     }
-  
+#if !defined(HAVE_O_CLOEXEC) && defined(F_SETFD)
+  else
+    fcntl (fd, F_SETFD, FD_CLOEXEC);
+#endif  
  
   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
   stream->priv->fd = fd;
diff --git a/gio/tests/file.c b/gio/tests/file.c
index d8769656c..ddd1ffcba 100644
--- a/gio/tests/file.c
+++ b/gio/tests/file.c
@@ -686,7 +686,7 @@ test_replace_cancel (void)
   guint count;
   GError *error = NULL;
 
-  g_test_bug ("629301");
+  g_test_bug ("https://bugzilla.gnome.org/629301");
 
   path = g_dir_make_tmp ("g_file_replace_cancel_XXXXXX", &error);
   g_assert_no_error (error);
@@ -805,6 +805,113 @@ test_replace_cancel (void)
   g_object_unref (tmpdir);
 }
 
+static void
+test_replace_symlink (void)
+{
+#ifdef G_OS_UNIX
+  gchar *tmpdir_path = NULL;
+  GFile *tmpdir = NULL, *source_file = NULL, *target_file = NULL;
+  GFileOutputStream *stream = NULL;
+  const gchar *new_contents = "this is a test message which should be written to source and not target";
+  gsize n_written;
+  GFileEnumerator *enumerator = NULL;
+  GFileInfo *info = NULL;
+  gchar *contents = NULL;
+  gsize length = 0;
+  GError *local_error = NULL;
+
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2325");
+  g_test_summary ("Test that G_FILE_CREATE_REPLACE_DESTINATION doesn’t follow symlinks");
+
+  /* Create a fresh, empty working directory. */
+  tmpdir_path = g_dir_make_tmp ("g_file_replace_symlink_XXXXXX", &local_error);
+  g_assert_no_error (local_error);
+  tmpdir = g_file_new_for_path (tmpdir_path);
+
+  g_test_message ("Using temporary directory %s", tmpdir_path);
+  g_free (tmpdir_path);
+
+  /* Create symlink `source` which points to `target`. */
+  source_file = g_file_get_child (tmpdir, "source");
+  target_file = g_file_get_child (tmpdir, "target");
+  g_file_make_symbolic_link (source_file, "target", NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  /* Ensure that `target` doesn’t exist */
+  g_assert_false (g_file_query_exists (target_file, NULL));
+
+  /* Replace the `source` symlink with a regular file using
+   * %G_FILE_CREATE_REPLACE_DESTINATION, which should replace it *without*
+   * following the symlink */
+  stream = g_file_replace (source_file, NULL, FALSE  /* no backup */,
+                           G_FILE_CREATE_REPLACE_DESTINATION, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  g_output_stream_write_all (G_OUTPUT_STREAM (stream), new_contents, strlen (new_contents),
+                             &n_written, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_assert_cmpint (n_written, ==, strlen (new_contents));
+
+  g_output_stream_close (G_OUTPUT_STREAM (stream), NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  g_clear_object (&stream);
+
+  /* At this point, there should still only be one file: `source`. It should
+   * now be a regular file. `target` should not exist. */
+  enumerator = g_file_enumerate_children (tmpdir,
+                                          G_FILE_ATTRIBUTE_STANDARD_NAME ","
+                                          G_FILE_ATTRIBUTE_STANDARD_TYPE,
+                                          G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  info = g_file_enumerator_next_file (enumerator, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_assert_nonnull (info);
+
+  g_assert_cmpstr (g_file_info_get_name (info), ==, "source");
+  g_assert_cmpint (g_file_info_get_file_type (info), ==, G_FILE_TYPE_REGULAR);
+
+  g_clear_object (&info);
+
+  info = g_file_enumerator_next_file (enumerator, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_assert_null (info);
+
+  g_file_enumerator_close (enumerator, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_clear_object (&enumerator);
+
+  /* Double-check that `target` doesn’t exist */
+  g_assert_false (g_file_query_exists (target_file, NULL));
+
+  /* Check the content of `source`. */
+  g_file_load_contents (source_file,
+                        NULL,
+                        &contents,
+                        &length,
+                        NULL,
+                        &local_error);
+  g_assert_no_error (local_error);
+  g_assert_cmpstr (contents, ==, new_contents);
+  g_assert_cmpuint (length, ==, strlen (new_contents));
+  g_free (contents);
+
+  /* Tidy up. */
+  g_file_delete (source_file, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  g_file_delete (tmpdir, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  g_clear_object (&target_file);
+  g_clear_object (&source_file);
+  g_clear_object (&tmpdir);
+#else  /* if !G_OS_UNIX */
+  g_test_skip ("Symlink replacement tests can only be run on Unix")
+#endif
+}
+
 static void
 on_file_deleted (GObject      *object,
 		 GAsyncResult *result,
@@ -1785,8 +1892,6 @@ main (int argc, char *argv[])
 {
   g_test_init (&argc, &argv, NULL);
 
-  g_test_bug_base ("http://bugzilla.gnome.org/");
-
   g_test_add_func ("/file/basic", test_basic);
   g_test_add_func ("/file/build-filename", test_build_filename);
   g_test_add_func ("/file/parent", test_parent);
@@ -1800,6 +1905,7 @@ main (int argc, char *argv[])
   g_test_add_data_func ("/file/async-create-delete/4096", GINT_TO_POINTER (4096), test_create_delete);
   g_test_add_func ("/file/replace-load", test_replace_load);
   g_test_add_func ("/file/replace-cancel", test_replace_cancel);
+  g_test_add_func ("/file/replace-symlink", test_replace_symlink);
   g_test_add_func ("/file/async-delete", test_async_delete);
   g_test_add_func ("/file/copy-preserve-mode", test_copy_preserve_mode);
   g_test_add_func ("/file/measure", test_measure);
-- 
2.33.0.464.g1972c5931b-goog