[Veserv]

Great, then falsify it. Point at a system with the same operational model as KVM-based multi-tenant systems with large numbers of platform vulnerabilitys.

Let us review a standard operational model:

Virtual machines are usually pre-allocated their total RAM. Virtual machines are usually pre-allocated a number of cores and pinned to them. Virtual machines are usually only allocated a small number of devices such as a virtual block storage device and virtual network device upon which they implement a in-VM filesystem and network stack. Virtual machines usually have no access to shared services provided by the hypervisor.

So we have a operational model where you have to pre-allocate RAM to a process. You have to pre-allocate a whole core and pin the process to it. The process has no access to a global filesystem, network stack, or devices. The process has access to exactly one file, which is logically similar to a virtual block storage device, and a single raw network socket, which is logically similar to a virtual network device. The process has no ability to form a socket to another process, form a new file, or even have any way of interacting with other processes at all. The process has no access to shared services of any kind.

The chasm between that operational model and any commercial IT operating system is immense, being basically the polar opposite in every dimension in the direction of security. Default-deny instead of default-allow. Shared-nothing instead of shared-everything. What you have there is a system even more static and simple than what runs on most microkernels. That is the comparable class of platforms with a similar operational model.

To demonstrate that virtualization is the key factor, you need to demonstrate that actually comparable systems with similar operational models like microkernels have more platform vulnerabilitys than comparable KVM-based, or even just hypervisor-based, systems. Which, again, flies against the face of evidence as the systems that are actually used in high security applications designed to protect against state actors are separation kernels instead of hypervisors.

[tptacek]

These are a lot of words that I think are trying to work around the fact that LPEs are commonplace and KVM escapes are very rare.

[Veserv]

Cool, show me a LPE in a seL4 deployment. Do you believe that is easier or harder than finding a KVM escape?

Since you are varying the security basis, implementation, and operational model simultaneously when you are comparing KVM to Linux to argue that the security basis is the important factor, I get to as well. Except mine is actually more fair because the design of a seL4-based system is actually much more similar to the design of a multi-tenant KVM-based system than the design of the KVM-based system is to the design of a Linux user environment.

[tptacek]

Amusingly, this is the 2nd time you've tried to argue with me about this Theo post. Last time, you yourself brought it up as a model of a good security argument.

https://news.ycombinator.com/item?id=41071954

Rather than replicating my response then, I'll just incorporate that link into my point.

I ported L4 to my ARM NUC a couple weeks ago. L4 is great. Of course, L4 is also principally a platform for virtualization, so it's a pretty odd bit of evidence to try to bring up. Where have you personally been using L4?

[Veserv]

Yes, you do enjoy evading the argument. You continuously point at implementation and operational model differences as proof that virtualization is the key factor. Theo's argument is literally that virtualization versus non-virtualization is irrelevant compared to implementation and operational model deficiencys. If you make garbage implementations and operational models, then you get garbage virtualization. If you have a good implementation and operational model then you do not need virtualization for "security".

As independent evidence for this point, virtualization is not the basis of security/isolation in seL4. You have isolation without any virtual machines. Virtual machines are just a feature on top that can leverage the existing isolation functionality to also provide isolated virtual machines. Of course, a secure deployment then requires you to leverage this foundation with a good operational model and system design since you can always make a insecure system even atop a good foundation. This demonstrates that virtualization is not necessary for a secure base, nor sufficient to achieve highly secure systems.

Just to hammer in the point that you are heavily misinterpreting Theo's response, this is the full sentence at the start of the post that Theo was responding to:

"Virtualization seems to have a lot of security benefits. Rootkits can lie to DomU but not Dom0, and of course snapshotting, migration etc is really nice."

Wow, amazing, rootkits can never be in Dom0 because Xen has "virtualization" magic pixie dust. Theo is pointing out how this is nonsense and virtualization will only provide security if you can create implementations without glaring security holes. Furthermore, you should not just listen to the people who brought you insecure system 1 when they tell you that this time for sure they are going to give you secure system 2; maybe have just a little bit of cynicism and ask for some evidence first.

[tptacek]

You keep mentioning seL4. I'm curious what work you've done with it. (I've done a bunch of L4 work.)