Hi all,
I'm planning on doing a small fork of the KVM tool to turn it into a
'Secure KVM' enabled hypervisor. Now you probably ask yourself, Huh?
The idea was discussed briefly couple of months ago, but never got off
the ground - which is a shame IMO.
It's easy to explain the problem: If an attacker finds a security hole
in any of the devices which are exposed to the guest, the attacker would
be able to either crash the guest, or possibly run code on the host
itself.
The solution is also simple to explain: Split the devices into different
processes and use seccomp to sandbox each device into the exact set of
resources it needs to operate, nothing more and nothing less.
Since I'll be basing it on the KVM tool, which doesn't really emulate
that many legacy devices, I'll focus first on the virtio family for the
sake of simplicity (and covering 90% of the options).
This is my basic overview of how I'm planning on implementing the
initial POC:
1. First I'll focus on the simple virtio-rng device, it's simple enough
to allow us to focus on the aspects which are important for the POC
while still covering most bases (i.e. sandbox to single file
- /dev/urandom and such).
2. Do it on a one process per device concept, where for each device
(notice - not device *type*) requested, a new process which handles it
will be spawned.
3. That process will be limited exactly to the resources it needs to
operate, for example - if we run a virtio-blk device, it would be able
to access only the image file which it should be using.
4. Connection between hypervisor and devices will be based on unix
sockets, this should allow for better separation compared to other
approaches such as shared memory.
5. While performance is an aspect, complete isolation is more important.
Security is primary, performance is secondary.
6. Share as much code as possible with current implementation of virtio
devices, make it possible to run virtio devices either like it's being
done now, or by spawning them as separate processes - the amount of
specific code for the separate process case should be minimal.
Thats all I have for now, comments are *very* welcome.