libvirt: make sysinfo serial number configurable

[OpenStack Infra]

https://review.openstack.org/113311
commit 4431eec1c94c4a353b45e5d873854b3fb1eaa11b
Author: Daniel P. Berrange <email address hidden>
Date: Mon Jul 28 15:15:44 2014 +0100

    libvirt: make sysinfo serial number configurable

    The 'serial' field in guest SMBIOS tables gets populated
    based on the libvirt reported UUID of the host hardware.
    The rationale is to allow correlation of guests running
    on the same host.

    Unfortunately some hardware vendors use a subset of the
    host UUID as a key for retrieving hardware support
    contract information without requiring any authentication.
    So exposing the host UUID to the guest is an information
    leak for those vendors. It is possible to override the
    use of SMBIOS data by libvirt in /etc/libvirt/libvirtd.conf
    by setting the 'host_uuid' parameter.

    As a way to reduce the configuration burden though, it is
    preferrable to use the /etc/machine-id UUID, instead of
    the host hardware UUID. The former is a recent standard
    for Linux distros introduced by systemd to provide a UUID
    that is unique per operating system install. This means
    that even containers will see a separate /etc/machine-id
    value. This /etc/machine-id can be expected to be widely
    available in current and future distros. If missing, it
    is still possible to fallback to the libvirt reported
    host UUID.

    The host UUID exposed could theoretically be leveraged
    by a cloud user to get an approximate count of the number
    of unique hosts available to them in the cloud by launching
    many short lived VMs. Administrators concerned about this
    may wish to disable reporting of any sysinfo serial field
    at all.

    Introduce a 'sysinfo_serial' config parameter to the libvirt
    driver to control behaviour, accepting values:

     - 'auto' - try /etc/machine-id, fallback to
       libvirt reported host UUID (new default)
     - 'hardware' - always use libvirt host UUID (old default)
     - 'os' - always use /etc/machine-id, error if missing
     - 'none' - do not report any value to the guest

    DocImpact: new libvirt.sysinfo_serial config parameter
    SecurityImpact
    Closes-bug: #1337349
    Change-Id: I7ba7dbd65e913a66efe35a1d6490a85bec8413da

[Andreas Jaeger (jaegerandi)]

Parameter has been added