[ovirt-devel] ovirt-guest-agent behavior on disconnect

[Michal Skrivanek]

On Sep 25, 2015, at 19:40 , David Mansfield <ovirt at dm.cobite.com> wrote:

> [cross-posted to devel at ovirt.org and spice-devel at lists.freedesktop.org]
> 
> Hi oVirt Devs,
> 
> I'm here from the spice-devel list where we were discussing some changes to the behavior of the spice guest agent reacting to a user disconnect (of the spice console).

Hi David,
great, any enhancement is good! Vinzenz, please add more details to my guesses below:)

> 
> Some information about how the ovirt-guest-agent works would be informative if you can spare a minute.
> 
> The functionality being discussed is locking the user session in the VM when the user disconnects from spice (either intentionally or unintentionally).
> 
> Also, peripherally, how does oVirt ensure secure access by authorized users of a VM and prevent "over-the-shoulder" snooping (spice graphics session stealing) or other forms of information leak from a VM shared by multiple users.
> 
> So here are some questions:
> 
> Can a VM be "shared" by multiple users in oVirt at all? Are there known security issues that would make this a non-recommended or fundamentally un-securable setup?

normally no, there is a semi-supported hook to allow that with VNC (and even that is slightly broken IIRC at the moment), but in general we do want so support that for specific usecases

> 
> Does the oVirt agent lock the session on disconnect? Always / unconditionally? If it's configurable, where does the configuration reside - in the vm guest, on the vm host (/engine) or on the client?

it's oVirt management UI configuration, it changes the host's behavior on spice disconnect per VM

> 
> Does the oVirt agent lock all sessions or the current active session?

just the active AFAIK

> 
> How does it lock the sessions?  I've looked at the code and it appears '/usr/bin/loginctl lock-sessions' is being used on machines it's provided on and something more complicated on older boxes.  Does the user have a way to customize this behavior? and if so, is it VM guest, VM host or client configuration?

> 
> Does the agent lock linux consoles (VC1, VC2) "sessions" (e.g. with vlock?)
> 
> As I understand it, console access in ovirt is managed by setting a temporary graphics password and then generating an .ini file which is launched by remote-viewer. This password expires after a short period of time.  So is there a mechanism where access is denied if a user is already connected or is this allowed?

connection is not allowed unless "strict user checking" disabled in UI
if it is disable or you use the same pwd then the previous session is terminated and replaced (unless using that hook I mentioned).
But we try to treat the .vv file as a one time thing, there's delete_this_file=1 which instructs virt-viewer to remove the file upon startup, so even when browser place them on a shared drive they shouldn't be there for too long


What kind of changes do you have in mind on the SPICE side?
It would certainly make it easier for us as currently we kind of guess when to lock…we receive multiple disconnecst(per channel) and don't really know what's going on…having a direct support for this inside the spice server would be better. But it needs to allow the flexibility of different actions except desktop lock (we have "nothing", "shutdown", "logoff" I think). Perhaps a way how to signal relevant information to vdsm is enough

Thanks,
michal

> 
> Enough questions for now, sorry for the battering.
> 
> -- 
> Thanks,
> David Mansfield
> Cobite, INC.
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