279 lines
9.6 KiB
Diff
279 lines
9.6 KiB
Diff
From 6c10e8ce6905e8fcc3466eb8af707b5d0d3bdb85 Mon Sep 17 00:00:00 2001
|
||
From: Philip Withnall <pwithnall@endlessos.org>
|
||
Date: Wed, 24 Feb 2021 17:36:07 +0000
|
||
Subject: [PATCH 2/3] 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 | 63 ++++++++++++++-------
|
||
gio/tests/file.c | 107 ++++++++++++++++++++++++++++++++++-
|
||
2 files changed, 149 insertions(+), 21 deletions(-)
|
||
|
||
diff --git a/gio/glocalfileoutputstream.c b/gio/glocalfileoutputstream.c
|
||
index 6a70b2a04..4a7766f68 100644
|
||
--- a/gio/glocalfileoutputstream.c
|
||
+++ b/gio/glocalfileoutputstream.c
|
||
@@ -779,16 +779,22 @@ 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 (!replace_destination_set)
|
||
+ 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 || !replace_destination_set)
|
||
+ {
|
||
+ fd = g_open (filename, open_flags, mode);
|
||
+ errsv = errno;
|
||
+ }
|
||
#endif
|
||
|
||
- if (fd == -1)
|
||
+ if (fd == -1 &&
|
||
+ (!is_symlink || !replace_destination_set))
|
||
{
|
||
char *display_name = g_filename_display_name (filename);
|
||
g_set_error (error, G_IO_ERROR,
|
||
@@ -800,10 +806,17 @@ handle_overwrite_open (const char *filename,
|
||
}
|
||
|
||
#ifdef G_OS_WIN32
|
||
- res = GLIB_PRIVATE_CALL (g_win32_fstat) (fd, &original_stat);
|
||
-#else
|
||
- res = fstat (fd, &original_stat);
|
||
+#error This patch has not been ported to Windows, sorry
|
||
#endif
|
||
+
|
||
+ if (!is_symlink)
|
||
+ {
|
||
+ res = fstat (fd, &original_stat);
|
||
+ }
|
||
+ else
|
||
+ {
|
||
+ res = lstat (filename, &original_stat);
|
||
+ }
|
||
errsv = errno;
|
||
|
||
if (res != 0)
|
||
@@ -821,16 +834,27 @@ 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)
|
||
@@ -911,7 +935,8 @@ 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 98eeb85d4..44db6e295 100644
|
||
--- a/gio/tests/file.c
|
||
+++ b/gio/tests/file.c
|
||
@@ -671,8 +671,6 @@ test_replace_cancel (void)
|
||
guint count;
|
||
GError *error = NULL;
|
||
|
||
- g_test_bug ("629301");
|
||
-
|
||
path = g_dir_make_tmp ("g_file_replace_cancel_XXXXXX", &error);
|
||
g_assert_no_error (error);
|
||
tmpdir = g_file_new_for_path (path);
|
||
@@ -779,6 +777,110 @@ 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;
|
||
+
|
||
+ /* 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,
|
||
@@ -1170,6 +1272,7 @@ 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);
|
||
--
|
||
2.31.1
|
||
|