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Chapter 19. Security for virtualization

When deploying virtualization technologies on your corporate infrastructure, you must ensure that the host cannot be compromised. The host, in the Xen hypervisor, is a privileged domain that handles system management and manages all virtual machines. If the host is insecure, all other domains in the system are vulnerable. There are several ways to enhance security on systems using virtualization. You or your organization should create a Deployment Plan containing the operating specifications and specifies which services are needed on your guests and host servers as well as what support is required for these services. Here are a few security issues to consider while developing a deployment plan:
  • Run only necessary services on hosts. The fewer processes and services running on the host, the higher the level of security and performance.
  • Enable Security-Enhanced Linux (SELinux) on the hypervisor. Read Section 19.2, “SELinux and virtualization” for more information on using SELinux and virtualization.
  • Use a firewall to restrict traffic to dom0. You can setup a firewall with default-reject rules that will help secure attacks on dom0. It is also important to limit network facing services.
  • Do not allow normal users to access dom0. If you do permit normal users dom0 access, you run the risk of rendering dom0 vulnerable. Remember, dom0 is privileged, and granting unprivileged accounts may compromise the level of security.

19.1. Storage security issues

Administrators of guests can change the partitions the host boots in certain circumstances. To prevent this administrators should follow these recommendations:
The host should not use disk labels to identify file systems in the fstab file, the initrd file or used by the kernel command line. If less privileged users, especially guests, have write access to whole partitions or LVM volumes.
Guest should not be given write access to whole disks or block devices (for example, /dev/sdb). Use partitions (for example, /dev/sdb1) or LVM volumes.