Re: [Qemu-devel] [PATCH v3 09/11] authz: add QAuthZListFile object type for a file access control list

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> On Wed, Jun 20, 2018 at 12:29:38PM +0100, Dr. David Alan Gilbert wrote:
> > * Daniel P. Berrangé (berrange@redhat.com) wrote:
> > > On Wed, Jun 20, 2018 at 11:58:01AM +0100, Dr. David Alan Gilbert wrote:
> > > > * Daniel P. Berrangé (berrange@redhat.com) wrote:
> > > > > Add a QAuthZListFile object type that implements the QAuthZ interface. This
> > > > > built-in implementation is a proxy around the QAtuhZList object type,
> > > > > initializing it from an external file, and optionally, automatically
> > > > > reloading it whenever it changes.
> > > > > 
> > > > > To create an instance of this object via the QMP monitor, the syntax
> > > > > used would be:
> > > > > 
> > > > >       {
> > > > >         "execute": "object-add",
> > > > >         "arguments": {
> > > > >           "qom-type": "authz-list-file",
> > > > >           "id": "authz0",
> > > > >           "parameters": {
> > > > >             "filename": "/etc/qemu/vnc.acl",
> > > > > 	    "refresh": "yes"
> > > > >           }
> > > > >         }
> > > > >       }
> > > > > 
> > > > > If "refresh" is "yes", inotify is used to monitor the file,
> > > > > automatically reloading changes. If an error occurs during reloading,
> > > > > all authorizations will fail until the file is next successfully
> > > > > loaded.
> > > > 
> > > > I'm curious about the 'refresh' stuff:
> > > >   a) If refresh=no is there a way to explicitly ask for a refresh
> > > >      when some tool knows it's finished with fiddling with the file.
> > > 
> > > If refresh=no, then you can still use  object_del + object_add to
> > > recreate the ACL object which will cause new content to be picked
> > > up.
> > 
> > But if I have a VNC/NBD/etc listening, won't it be bound to the old
> > object, so I can't delete the old object?
> 
> That's ok actually - the network servers merely record the ID of the
> authz object. They resolve that to an actual object instance at the
> time they do the authorization check, and failsafe to DENY if it is
> missing. So you can safely delete & recreate on the fly.

OK, that needs documenting; binding it at the time of parsing wouldn't
be surprising to anyone except for that use.

Dave

> Regards,
> Daniel
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Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK