Crossing The Streams -- Virtually

Everywhere I go, virtualization is being used. No matter the size of the organization, virtualization has taken off with, what appears to be, very little concern about security. As security professionals, we know not to mix security domains across the same physical machines or cluster. Why? The answer is simple. A vulnerability could exist in the virtualization product that would allow an attacker to exploit a less secure, or lower value, guest VM allowing them to run arbitrary code on the host server. Far-fetched? Absolutely not!Take a look at the recent vulnerabilities in both Citrix XenServer and VMware ESX Server. XenServer suffered a vulnerability that allowed a local attacker to place code on a guest VM's file system, leading to execution of arbitrary code in the master domain (or host server). VMware patched numerous vulnerabilities that allowed both local and remote attackers to bypass security restrictions, cause denial-of-services conditions, and escalate privileges.

Does that make you feel warm and fuzzy about the safety of your data on the virtual infrastructure in your company? Yeah, I didn't think so. During Risky Business Podcast #89, Patrick Gray, Adam Pointon, and Neal Wise were discussing the XenServer vulnerability and brought up an idea I hadn't thought of before. It's essentially the idea of pivoting and exploiting other hosts like a typical pentest, but the variation is in taking advantage of the ability to migrate a VM from one physical server to another physical server.

From a pen-testing standpoint, this is a wicked idea. Imagine if you were able to exploit a lower value VM and gain control of the physical host server. If you could then migrate the lower value VM to a physical server that has a higher value or security domain, you could then re-exploit that lower value VM to gain control of the higher security domain host.

With appropriate separation and stop-gap measures, this attack is moot, but something I took away from the podcast is that although we infosec pros know better, it's not happening out in the real world. I think it was Neal who said he's seeing the mix of security domains occurring in the field with clients he's working with. Ouch!

If you've not read the "The Four Horsemen Of the Virtualization Security Apocalypse" from Chris Hoff, put it on your to do list. It'll open your eyes to some things that you probably haven't considered regarding the impact of virtualization in your environment.

John H. Sawyer is a Senior Security Engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.