gnu: glib: Fix CVE-2021-28153.

* gnu/packages/patches/glib-CVE-2021-28153.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/glib.scm (glib/fixed): Add the new patch.

1 files changed, 283 insertions, 0 deletions

diff --git a/gnu/packages/patches/glib-CVE-2021-28153.patch b/gnu/packages/patches/glib-CVE-2021-28153.patch
new file mode 100644
index 0000000000..54443186d9
--- /dev/null
+++ b/gnu/packages/patches/glib-CVE-2021-28153.patch
@@ -0,0 +1,283 @@
+Backport of:
+
+From 317b3b587058a05dca95d56dac26568c5b098d33 Mon Sep 17 00:00:00 2001
+From: Philip Withnall <pwithnall@endlessos.org>
+Date: Wed, 24 Feb 2021 17:35:40 +0000
+Subject: [PATCH] glocalfileoutputstream: Fix CREATE_REPLACE_DESTINATION
+ with symlinks
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+The `G_FILE_CREATE_REPLACE_DESTINATION` flag is equivalent to unlinking
+the destination file and re-creating it from scratch. That did
+previously work, but in the process the code would call `open(O_CREAT)`
+on the file. If the file was a dangling symlink, this would create the
+destination file (empty). That’s not an intended side-effect, and has
+security implications if the symlink is controlled by a lower-privileged
+process.
+
+Fix that by not opening the destination file if it’s a symlink, and
+adjusting the rest of the code to cope with
+ - the fact that `fd == -1` is not an error iff `is_symlink` is true,
+ - and that `original_stat` will contain the `lstat()` results for the
+   symlink now, rather than the `stat()` results for its target (again,
+   iff `is_symlink` is true).
+
+This means that the target of the dangling symlink is no longer created,
+which was the bug. The symlink itself continues to be replaced (as
+before) with the new file — this is the intended behaviour of
+`g_file_replace()`.
+
+The behaviour for non-symlink cases, or cases where the symlink was not
+dangling, should be unchanged.
+
+Includes a unit test.
+
+Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
+
+Fixes: #2325
+---
+ gio/glocalfileoutputstream.c |  70 ++++++++++++++++-------
+ gio/tests/file.c             | 108 +++++++++++++++++++++++++++++++++++
+ 2 files changed, 158 insertions(+), 20 deletions(-)
+
+diff --git a/gio/glocalfileoutputstream.c b/gio/glocalfileoutputstream.c
+index a3dd62172..553fcbbae 100644
+--- a/gio/glocalfileoutputstream.c
++++ b/gio/glocalfileoutputstream.c
+@@ -874,16 +874,22 @@ handle_overwrite_open (const char    *filename,
+       /* Could be a symlink, or it could be a regular ELOOP error,
+        * but then the next open will fail too. */
+       is_symlink = TRUE;
+-      fd = g_open (filename, open_flags, mode);
++      if (!(flags & G_FILE_CREATE_REPLACE_DESTINATION))
++        fd = g_open (filename, open_flags, mode);
+     }
+-#else
+-  fd = g_open (filename, open_flags, mode);
+-  errsv = errno;
++#else  /* if !O_NOFOLLOW */
+   /* This is racy, but we do it as soon as possible to minimize the race */
+   is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
++
++  if (!is_symlink || !(flags & G_FILE_CREATE_REPLACE_DESTINATION))
++    {
++      fd = g_open (filename, open_flags, mode);
++      errsv = errno;
++    }
+ #endif
+ 
+-  if (fd == -1)
++  if (fd == -1 &&
++      (!is_symlink || !(flags & G_FILE_CREATE_REPLACE_DESTINATION)))
+     {
+       char *display_name = g_filename_display_name (filename);
+       g_set_error (error, G_IO_ERROR,
+@@ -893,13 +899,25 @@ handle_overwrite_open (const char    *filename,
+       g_free (display_name);
+       return -1;
+     }
+-  
++
++  if (!is_symlink)
++    {
+ #ifdef G_OS_WIN32
+-  res = GLIB_PRIVATE_CALL (g_win32_fstat) (fd, &original_stat);
++      res = GLIB_PRIVATE_CALL (g_win32_fstat) (fd, &original_stat);
+ #else
+-  res = fstat (fd, &original_stat);
++      res = fstat (fd, &original_stat);
+ #endif
+-  errsv = errno;
++      errsv = errno;
++    }
++  else
++    {
++#ifdef G_OS_WIN32
++      res = GLIB_PRIVATE_CALL (g_win32_lstat_utf8) (filename, &original_stat);
++#else
++      res = g_lstat (filename, &original_stat);
++#endif
++      errsv = errno;
++    }
+ 
+   if (res != 0)
+     {
+@@ -916,16 +934,27 @@ handle_overwrite_open (const char    *filename,
+   if (!S_ISREG (original_stat.st_mode))
+     {
+       if (S_ISDIR (original_stat.st_mode))
+-	g_set_error_literal (error,
+-                             G_IO_ERROR,
+-                             G_IO_ERROR_IS_DIRECTORY,
+-                             _("Target file is a directory"));
+-      else
+-	g_set_error_literal (error,
+-                             G_IO_ERROR,
+-                             G_IO_ERROR_NOT_REGULAR_FILE,
+-                             _("Target file is not a regular file"));
+-      goto err_out;
++        {
++          g_set_error_literal (error,
++                               G_IO_ERROR,
++                               G_IO_ERROR_IS_DIRECTORY,
++                               _("Target file is a directory"));
++          goto err_out;
++        }
++      else if (!is_symlink ||
++#ifdef S_ISLNK
++               !S_ISLNK (original_stat.st_mode)
++#else
++               FALSE
++#endif
++               )
++        {
++          g_set_error_literal (error,
++                               G_IO_ERROR,
++                               G_IO_ERROR_NOT_REGULAR_FILE,
++                               _("Target file is not a regular file"));
++          goto err_out;
++        }
+     }
+   
+   if (etag != NULL)
+@@ -1006,7 +1035,8 @@ handle_overwrite_open (const char    *filename,
+ 	    }
+ 	}
+ 
+-      g_close (fd, NULL);
++      if (fd >= 0)
++        g_close (fd, NULL);
+       *temp_filename = tmp_filename;
+       return tmpfd;
+     }
+diff --git a/gio/tests/file.c b/gio/tests/file.c
+index efb2eaadd..bc55f3af4 100644
+--- a/gio/tests/file.c
++++ b/gio/tests/file.c
+@@ -804,6 +804,113 @@ 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,
+@@ -1754,6 +1861,7 @@ 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);
+ #ifdef G_OS_UNIX
+   g_test_add_func ("/file/copy-preserve-mode", test_copy_preserve_mode);
+-- 
+2.30.1
+