When using virtual machines (VMs), multiple operating systems can be housed within a single host machine. These systems are connected with the host through the hypervisor, and usually also through a virtual network. As a consequence, each VM can be used as a vector for attacking the host with malicious software, and the host can be used as a vector for attacking any of the VMs.

Figure 15.1. A potential malware attack vector on a virtualization host

Because the hypervisor uses the host kernel to manage VMs, services running on the VM’s operating system are frequently used for injecting malicious code into the host system. However, you can protect your system against such security threats by using a number of security features on your host and your guest systems.

These features, such as SELinux or QEMU sandboxing, provide various measures that make it more difficult for malicious code to attack the hypervisor and transfer between your host and your VMs.

Figure 15.2. Prevented malware attacks on a virtualization host

Many of the features that RHEL 8 provides for VM security are always active and do not have to be enabled or configured. For details, see Section 15.4, “Automatic features for virtual machine security”.

In addition, you can adhere to a variety of best practices to minimize the vulnerability of your VMs and your hypervisor. For more information, see Section 15.2, “Best practices for securing virtual machines”.

Following the instructions below significantly decreases the risk of your virtual machines being infected with malicious code and used as attack vectors to infect your host system.

On the guest side:

On the host side:

The following provides instructions on creating a Linux virtual machine (VM) that uses the SecureBoot feature, which ensures that your VM is running a cryptographically signed OS. If the guest OS of a VM has been altered by malware, SecureBoot prevents the VM from booting, which stops the potential spread of the malware to your host machine.

In addition to manual means of improving the security of your virtual machines listed in Section 15.2, “Best practices for securing virtual machines”, a number of security features are provided by the libvirt software suite and are automatically enabled when using virtualization in RHEL 8. These include:

For fine-grained configuration of virtual machines security on a RHEL 8 system, you can configure SELinux booleans on the host to ensure the hypervisor acts in a specific way.

To list all virtualization-related booleans and their statuses, use the getsebool -a | grep virt command:

$ getsebool -a | grep virt
[...]
virt_sandbox_use_netlink --> off
virt_sandbox_use_sys_admin --> off
virt_transition_userdomain --> off
virt_use_comm --> off
virt_use_execmem --> off
virt_use_fusefs --> off
[...]

To enable a specific boolean, use the setsebool -P boolean_name on command as root. To disable a boolean, use setsebool -P boolean_name off.

The following table lists virtualization-related booleans available in RHEL 8 and what they do when enabled: