[libvirt] Implementing VNC per VM access control lists

[Eric Blake]

On 01/06/2011 11:00 AM, Neil Wilson wrote:
> Having looked through this, I'm thinking that the simplest thing that
> would be useful at the moment is simply to have an option in
> the /etc/libvirt/qemu.conf that adds the acl option to the vnc switch in
> qemu.
> 
> It means that user will have to manipulate the acls directly via the
> monitor command for the time being until the access layer is designed,
> but at least you would be able to use acls on a machine launched by
> libvirt ('change vnc' doesn't appear to activate acls unless the option
> is active on the command line to start with.).
> 
> I can't find a way of doing it with 'qemu:commandline' either - since it
> is an option to an existing switch.

When we first designed qemu:commandline, we debated about making it
smart enough to allow rewriting of existing arguments (rather than only
allowing addition of new arguments).  This definitely sounds like a use
case worth revisiting that situation, and enhancing qemu:commandline to
have more features.

> 
> So I'm thinking a new option in qemu.conf (vnc_acl) which would add
> ',acl' to the vnc switch on the qemu command. By default this would bar
> access to VNC until you'd issued monitor commands to manipulate the
> access lists.
> 
> The option only really makes sense if either vnc_tls_x509_verify or
> vnc_sasl is set as well, so it may be worth only activating 'acl' in the
> code if either of those two are also on.

Should this be a per-XML setting, rather than a global qemu.conf setting?

Is this something that is forward-looking (ie. once we also have an
access layer designed, will it still make sense to keep and honor the
qemu.conf setting), or is it enough of a hack that we should instead try
to resolve it via the qemu:commandline approach (where we've explicitly
documented that use of the interface is the approved way to do hacks in
the absence of proper libvirt support)?

It's definitely a hack that would let us get to the point o

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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