There is no reason for the libvirt-dbus daemon to require root privileges. All
it actually needs is ability to connect to libvirtd, which can be achieved by
dropping in a polkit configuration file.

Now a libvirt connection to the system bus gives you privileges equivalent to
root, so this doesn't really improve security on its own. It relies on there
being a dbus policy that prevents users from issuing elevated APIs.

For example, a DBus policy could allow non-root users to list VMs on the
system bus and get their status (aka virsh list equiv). In this case, the
security isolation does give some benefit.

Security can be further improved if the admin uses the libvirt polkit file to
restrict what libvirt-dbus is permitted to do.

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>