Re: [libvirt] Question about LSN-2016-0001

On Fri, Jul 29, 2016 at 02:16:16PM -0600, Jim Fehlig wrote: > I've noticed the behavior described by this LSN with libvirt+Xen. Config > containing <graphics type='vnc' passwd=''/> allows any client to > connect with no authentication check. I asked about this on the Xen security > list and was told that "libxl interprets an empty password in the caller's > configuration to mean that passwordless access should be permitted". The libvirt > domXML docs are not clear on semantics of empty vnc password, only stating "The > passwd attribute provides a VNC password in clear text". > > Should the libvirt domXML vnc passwd documentation be amended to define the > semantics of an empty string in the passwd attribute? Is the behavior > hypervisor-dependent as the documentation in qemu.conf suggests? I guess we've never clarified the semantics in any cross-hypervisor manner. I think the fixed QEMU behaviour is the most sane from a portability POV - the Xen (and broken QEMU) behaviour was effectively overloading 2 settings onto one attribute. ie it was (ab)using a zero length password as a way to change the authentication method.

We should always have distinct XML attributes for distinct settings. IOW, any toggle betweeen password and no-auth should an explicit setting and a zero length password should not magically change that.