system-proxy/dbus/org.chromium.SystemProxy.conf

<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<!--
  Copyright 2020 The Chromium OS Authors. All rights reserved.
  Use of this source code is governed by a BSD-style license that can be
  found in the LICENSE file.
-->

<busconfig>
  <policy user="system-proxy">
    <allow own="org.chromium.SystemProxy"/>
  </policy>

   <policy user="chronos">
    <!-- Kerberos -->
    <allow send_destination="org.chromium.SystemProxy"
           send_interface="org.chromium.SystemProxy"
           send_member="SetSystemTrafficCredentials"/>
    <allow send_destination="org.chromium.SystemProxy"
           send_interface="org.chromium.SystemProxy"
           send_member="ShutDownRequest"/>
  </policy>

  <!-- For testing.  -->
  <policy user="root">
    <allow send_destination="org.chromium.SystemProxy"
           send_interface="org.chromium.SystemProxy"/>
  </policy>
</busconfig>