shairport-sync-dbus-policy.conf

<!-- initial version, based on /etc/dbus-1/system.d/avahi-dbus.conf, with thanks -->
<!DOCTYPE busconfig PUBLIC
          "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
          "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>

  <!-- Allow users "root" and "shairport-sync" to own the Shairport Sync service -->
  <policy user="root">
    <allow own="org.gnome.ShairportSync"/>
  </policy>
  <policy user="shairport-sync">
    <allow own="org.gnome.ShairportSync"/>
  </policy>


  <!-- Allow anyone to invoke methods on Shairport Sync server -->
  <policy context="default">
    <allow send_destination="org.gnome.ShairportSync"/>
    <allow receive_sender="org.gnome.ShairportSync"/>
  </policy>

</busconfig>