commit 3ca17ea15b0b4d7314e0bff3ff14e35e04e320c4
Author: David Herrmann <dh.herrmann@gmail.com>
Date:   Wed Jul 15 13:49:49 2015 +0200

    policy: don't prevent us from receiving signals
    
    By using:
        <deny send_destination="org.freedesktop.ModemManager1"/>
    
    ..we prevent anyone on the system from sending us signals, even if we
    subscribed to them. This is clearly not what this line intended. More
    importantly, we silently break mm-auth-provider-polkit, as we never
    receiver 'changed' signals via PolkitAuthority. Right now, this is not
    required by the implementation of PolkitAuthority, but ModemManager
    should not place restrictions on the implementation of external
    libraries.
    
    So make sure we only prevent Method-Calls to be sent to us. Any other
    message that we didn't expect is automatically discarded by gdbus,
    anyway.
    
    Without this change, debugging dbus policies constantly shows messages
    that Polkit couldn't send the 'changed' signal to ModemManager. This is
    suppressed in non-debugging mode. But it would make debugging a lot
    easier, if we'd avoid force-dropping those events and not clutter the
    debug-log.

diff --git a/data/org.freedesktop.ModemManager1.conf.polkit b/data/org.freedesktop.ModemManager1.conf.polkit
index d1ea166..6b90b4b 100644
--- a/data/org.freedesktop.ModemManager1.conf.polkit
+++ b/data/org.freedesktop.ModemManager1.conf.polkit
@@ -3,7 +3,8 @@
  "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
 <busconfig>
   <policy context="default">
-    <deny send_destination="org.freedesktop.ModemManager1"/>
+    <deny send_destination="org.freedesktop.ModemManager1"
+          send_type="method_call"/>
 
     <!-- Methods listed here are explicitly allowed or PolicyKit protected.
          The rest are restricted to root for security.