update_engine/UpdateEngine.conf

<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
  "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
  <policy user="root">
    <allow own="org.chromium.UpdateEngine" />
    <allow send_destination="org.chromium.UpdateEngine" />
  </policy>
  <policy user="chronos">
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="AttemptUpdate"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="AttemptUpdateWithFlags"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="AttemptRollback"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="CanRollback"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetRollbackPartition"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetKernelDevices"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="ResetStatus"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetStatus"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="RebootIfNeeded"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="SetChannel"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetChannel"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="SetP2PUpdatePermission"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetP2PUpdatePermission"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="SetUpdateOverCellularPermission"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetUpdateOverCellularPermission"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetDurationSinceUpdate"/>
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetPrevVersion"/>
    <allow send_interface="org.chromium.UpdateEngineLibcrosProxyResolvedInterface" />
  </policy>
  <policy user="power">
    <allow send_destination="org.chromium.UpdateEngine"
           send_interface="org.chromium.UpdateEngineInterface"
           send_member="GetStatus"/>
  </policy>
</busconfig>