From a207f67f73ea7790f9562b46843c5f83f72973de Mon Sep 17 00:00:00 2001 From: Will Thompson Date: Wed, 28 Aug 2019 15:39:44 +0100 Subject: [PATCH] global: Don't trust persistent/runtime state data An Endless OS system was found in the wild with a malformed .local/share/gnome-shell/notifications. When deserialized in Python, after passing trusted=True to g_variant_new_from_bytes(), the first element of the first struct in the array looks like this: In [41]: _38.get_child_value(0).get_child_value(0) Out[41]: GLib.Variant('s', '\Uffffffff\Uffffffff\Uffffffff\Uffffffff\Uffffffff') When deserialised in GJS, we get: gjs> v.get_child_value(0).get_child_value(0) [object variant of type "s"] gjs> v.get_child_value(0).get_child_value(0).get_string() typein:43:1 malformed UTF-8 character sequence at offset 0 @typein:43:1 @:1:34 While g_variant_new_from_bytes() doesn't have much to say about its 'trusted' parameter, g_variant_new_from_data() does: > If data is trusted to be serialised data in normal form then trusted > should be TRUE. This applies to serialised data created within this > process or read from a trusted location on the disk (such as a file > installed in /usr/lib alongside your application). You should set > trusted to FALSE if data is read from the network, a file in the > user's home directory, etc. Persistent state is read from the user's home directory, so it should not be trusted. With trusted=False, the string value above comes out as "". I don't have an explanation for how this file ended up being malformed. I also don't have an explanation for when this started crashing: my guess is that recent GJS became stricter about validating UTF-8 but I could be wrong! https://gitlab.gnome.org/GNOME/gnome-shell/issues/1552 --- src/shell-global.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/shell-global.c b/src/shell-global.c index 1556bf03d..80f251272 100644 --- a/src/shell-global.c +++ b/src/shell-global.c @@ -1577,7 +1577,7 @@ load_variant (GFile *dir, else { GBytes *bytes = g_mapped_file_get_bytes (mfile); - res = g_variant_new_from_bytes (G_VARIANT_TYPE (property_type), bytes, TRUE); + res = g_variant_new_from_bytes (G_VARIANT_TYPE (property_type), bytes, FALSE); g_bytes_unref (bytes); g_mapped_file_unref (mfile); }