We directly get the length of the secret from the g_variant
and use it in a following g_strndup which ensures that the
resulting string is terminated.
This fixes reading secrets which were stored by system-config-printer.
https://bugzilla.gnome.org/show_bug.cgi?id=740612
When a printer requires auth_info (e.g. a printer connected
over the samba protocol) it is now possible to save the
credentials necessary for printing if a secrets service
is available over dbus.
The auth_info is then stored / loaded from the default
collection of that secrets service.
If no such service is available the user is not shown
the option to remember the password and the behavior
remains the same as before.
https://bugzilla.gnome.org/show_bug.cgi?id=674264
