Secure Boot

New in version 14.0.0: (Newton)

Changed in version 23.0.0: (Wallaby)

Added support for Secure Boot to the libvirt driver.

Nova supports configuring UEFI Secure Boot for guests. Secure Boot aims to ensure no unsigned kernel code runs on a machine.

Enabling Secure Boot

Currently the configuration of UEFI guest bootloaders is only supported when using the libvirt compute driver with a libvirt.virt_type of kvm or qemu or when using the Hyper-V compute driver with certain machine types. In both cases, it requires the guests also be configured with a UEFI bootloader.

With these requirements satisfied, you can verify UEFI Secure Boot support by inspecting the traits on the compute node’s resource provider:

$ COMPUTE_UUID=$(openstack resource provider list --name $HOST -f value -c uuid)
$ openstack resource provider trait list $COMPUTE_UUID | grep COMPUTE_SECURITY_UEFI_SECURE_BOOT
| COMPUTE_SECURITY_UEFI_SECURE_BOOT |

Configuring a flavor or image

Configuring UEFI Secure Boot for guests varies depending on the compute driver in use. In all cases, a UEFI guest bootloader must be configured for the guest but there are also additional requirements depending on the compute driver in use.

Libvirt

As the name would suggest, UEFI Secure Boot requires that a UEFI bootloader be configured for guests. When this is done, UEFI Secure Boot support can be configured using the os:secure_boot extra spec or equivalent image metadata property. For example, to configure an image that meets both of these requirements:

$ openstack image set \
    --property hw_firmware_type=uefi \
    --property os_secure_boot=required \
    $IMAGE

Note

On x86_64 hosts, enabling secure boot also requires configuring use of the Q35 machine type. This can be configured on a per-guest basis using the hw_machine_type image metadata property or automatically for all guests created on a host using the libvirt.hw_machine_type config option.

It is also possible to explicitly request that secure boot be disabled. This is the default behavior, so this request is typically useful when an admin wishes to explicitly prevent a user requesting secure boot by uploading their own image with relevant image properties. For example, to disable secure boot via the flavor:

$ openstack flavor set --property os:secure_boot=disabled $FLAVOR

Finally, it is possible to request that secure boot be enabled if the host supports it. This is only possible via the image metadata property. When this is requested, secure boot will only be enabled if the host supports this feature and the other constraints, namely that a UEFI guest bootloader is configured, are met. For example:

$ openstack image set --property os_secure_boot=optional $IMAGE

Note

If both the image metadata property and flavor extra spec are provided, they must match. If they do not, an error will be raised.

Hyper-V

Like libvirt, configuring a guest for UEFI Secure Boot support also requires that it be configured with a UEFI bootloader: As noted in UEFI, it is not possible to do this explicitly in Hyper-V. Rather, you should configure the guest to use the Generation 2 machine type. In addition to this, the Hyper-V compute driver also requires that the OS type be configured.

When both of these constraints are met, you can configure UEFI Secure Boot support using the os:secure_boot extra spec or equivalent image metadata property. For example, to configure an image that meets all the above requirements:

$ openstack image set \
    --property hw_machine_type=hyperv-gen2 \
    --property os_type=windows \
    --property os_secure_boot=required \
    $IMAGE

As with the libvirt driver, it is also possible to request that secure boot be disabled. This is the default behavior, so this is typically useful when an admin wishes to explicitly prevent a user requesting secure boot. For example, to disable secure boot via the flavor:

$ openstack flavor set --property os:secure_boot=disabled $IMAGE

However, unlike the libvirt driver, the Hyper-V driver does not respect the optional value for the image metadata property. If this is configured, it will be silently ignored.

References