[libvirt PATCH v2 00/12] tools: provide virt-qemu-sev-validate for SEV(-ES) launch attestation

Cole Robinson crobinso at redhat.com
Tue Oct 25 18:59:47 UTC 2022

On 10/19/22 6:17 AM, Daniel P. Berrangé wrote:
> The libvirt QEMU driver provides all the functionality required for
> launching a guest on AMD SEV(-ES) platforms, with a configuration
> that enables attestation of the launch measurement. The documentation
> for how to actually perform an attestation is severely lacking and
> not suitable for mere mortals to understand. IOW, someone trying to
> implement attestation is in for a world of pain and suffering.
> This series doesn't fix the documentation problem, but it does
> provide a reference implementation of a tool for performing
> attestation of SEV(-ES) guests in the context of libvirt / KVM.
> There will be other tools and libraries that implement attestation
> logic too, but this tool is likely somewhat unique in its usage of
> libvirt. Now for a attestation to be trustworthy you don't want to
> perform it on the hypervisor host, since the goal is to prove that
> the hypervisor has not acted maliciously. None the less it is still
> beneficial to have libvirt integration to some extent.
> When running this tool on a remote (trusted) host, it can connect
> to the libvirt hypervisor and fetch the data provided by the
> virDomainLaunchSecurityInfo API, which is safe to trust as the
> key pieces are cryptographically measured.
> Attestation is a complex problem though and it is very easy to
> screw up and feed the wrong information and then waste hours trying
> to figure out what piece was wrong, to cause the hash digest to
> change. For debugging such problems, you can thus tell the tool
> to operate insecurely, by querying libvirt for almost all of the
> configuration information required to determine the expected
> measurement. By comparing these results,to the results obtained
> in offline mode it helps narrow down where the mistake lies.
> So I view this tool as being useful in a number of ways:
>  * Quality assurance engineers needing to test libvirt/QEMU/KVM
>    get a simple and reliable tool for automating tests with.
>  * Users running simple libvirt deployments without any large
>    management stack, get a standalone tool for attestation
>    they can rely on.
>  * Developers writing/integrating attestation support into
>    management stacks above libvirt, get a reference against
>    which they can debug their own tools.
>  * Users wanting to demonstrate the core SEV/SEV-ES functionality
>    get a simple and reliable tool to illustrate the core concepts
>    involved.
> Since I didn't fancy writing such complex logic in C, this tool is
> a python3 program. As such, we don't want to include it in the
> main libvirt-client RPM, nor any other existing RPM. THus, this
> series puts it in a new libvirt-client-qemu RPM which, through no
> co-inicidence at all, is the same RPM I invented a few days ago to
> hold the virt-qemu-qmp-proxy command.
> Note, people will have already seen an earlier version of this
> tool I hacked up some months ago. This code is very significantly
> changed since that earlier version, to make it more maintainable,
> and simpler to use (especially for SEV-ES) but the general theme
> is still the same.
> Changed in v2:
>  - All the suggestions from Cole and Kashyap
> Daniel P. Berrangé (12):
>   build-aux: only forbid gethostname in C files
>   tools: support validating SEV firmware boot measurements
>   tools: load guest config from libvirt
>   tools: support validating SEV direct kernel boot measurements
>   tools: load direct kernel config from libvirt
>   tools: support validating SEV-ES initial vCPU state measurements
>   tools: support automatically constructing SEV-ES vCPU state
>   tools: load CPU count and CPU SKU from libvirt
>   tools: support generating SEV secret injection tables
>   docs/kbase: describe attestation for SEV guests
>   scripts: add systemtap script for capturing SEV-ES VMSA
>   docs/manpages: add checklist of problems for SEV attestation
>  build-aux/syntax-check.mk                |    1 +
>  docs/kbase/launch_security_sev.rst       |  105 ++
>  docs/manpages/meson.build                |    1 +
>  docs/manpages/virt-qemu-sev-validate.rst |  647 +++++++++++
>  examples/systemtap/amd-sev-es-vmsa.stp   |   48 +
>  libvirt.spec.in                          |    2 +
>  tools/meson.build                        |    5 +
>  tools/virt-qemu-sev-validate             | 1292 ++++++++++++++++++++++
>  8 files changed, 2101 insertions(+)
>  create mode 100644 docs/manpages/virt-qemu-sev-validate.rst
>  create mode 100644 examples/systemtap/amd-sev-es-vmsa.stp
>  create mode 100755 tools/virt-qemu-sev-validate

Reviewed-by: Cole Robinson <crobinso at redhat.com>

- Cole

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