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libvirt/docs/manpages/virt-qemu-sev-validate.rst
Daniel P. Berrangé 3e7b7da9e0 tools: support validating SEV-ES initial vCPU state measurements 
With the SEV-ES policy the VMSA state of each vCPU must be included in
the measured data. The VMSA state can be generated using the 'sevctl'
tool, by telling it a QEMU VMSA is required, and passing the hypevisor's
CPU SKU (family, model, stepping).

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2022-11-15 11:09:30 +00:00

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======================
virt-qemu-sev-validate
======================
--------------------------------------------
validate a domain AMD SEV launch measurement
--------------------------------------------
:Manual section: 1
:Manual group: Virtualization Support
.. contents::
SYNOPSIS
========
``virt-qemu-sev-validate`` [*OPTIONS*]
DESCRIPTION
===========
This program validates the reported measurement for a domain launched with AMD
SEV. If the program exits with a status of zero, the guest owner can be
confident that their guest OS is running under the protection offered by the
SEV / SEV-ES platform.
Note that the level of protection varies depending on the AMD SEV platform
generation and describing the differences is outside the scope of this
document.
For the results of this program to be considered trustworthy, it is required to
be run on a machine that is already trusted by the guest owner. This could be a
machine that the guest owner has direct physical control over, or it could be
another virtual machine protected by AMD SEV that has already had its launch
measurement validated. Running this program on the virtualization host will not
produce an answer that can be trusted.
If told to connect to libvirt, it will refuse to use a libvirt connection that
is local to the machine, since that cannot be trusted. For the sake of testing
or demonstration purposes, however, it can be forced to run in this scenario
using the ``--insecure`` flag. The result will, of course, still not be
trustworthy.
OPTIONS
=======
Common options
--------------
``-h``, ``--help``
Display command line help usage then exit.
``-d``, ``--debug``
Show debug information while running
``-q``, ``--quiet``
Don't print information about the attestation result.
Guest state options
-------------------
These options provide information about the state of the guest that needs its
boot attested.
``--measurement BASE64-STRING``
The launch measurement reported by the hypervisor of the domain to be validated.
The measurement must be 48 bytes of binary data encoded as a base64 string.
``--api-major VERSION``
The SEV API major version of the hypervisor the domain is running on.
``--api-minor VERSION``
The SEV API major version of the hypervisor the domain is running on.
``--build-id ID``
The SEV build ID of the hypervisor the domain is running on.
``--policy POLiCY``
The policy bitmask associated with the session launch data of the domain to be
validated.
Guest config options
--------------------
These options provide items needed to calculate the expected domain launch
measurement. This will then be compared to the reported launch measurement.
``-f PATH``, ``--firmware=PATH``
Path to the firmware loader binary. This is the EDK2 build that knows how to
initialize AMD SEV. For the validation to be trustworthy it important that the
firmware build used has no support for loading non-volatile variables from
NVRAM, even if NVRAM is expose to the guest.
``-k PATH``, ``--kernel=PATH``
Path to the kernel binary if doing direct kernel boot.
``-r PATH``, ``--initrd=PATH``
Path to the initrd binary if doing direct kernel boot. Defaults to zero length
content if omitted.
``-e STRING``, ``--cmdline=STRING``
String containing any kernel command line parameters used during boot of the
domain. Defaults to the empty string if omitted.
``-n COUNT``, ``--num-cpus=COUNT``
The number of virtual CPUs for the domain. This is required when the
domain policy is set to require SEV-ES.
``-0 PATH``, ``--vmsa-cpu0=PATH``
Path to the VMSA initial state for the boot CPU. This is required when
the domain policy is set to require SEV-ES. The file contents must be
exactly 4096 bytes in length.
``-1 PATH``, ``--vmsa-cpu1=PATH``
Path to the VMSA initial state for the non-boot CPU. This is required when
the domain policy is set to require SEV-ES and the domain has more than one
CPU present. The file contents must be exactly 4096 bytes in length.
``--tik PATH``
TIK file for domain. This file must be exactly 16 bytes in size and contains the
unique transport integrity key associated with the domain session launch data.
This is mutually exclusive with the ``--tk`` argument.
``--tek PATH``
TEK file for domain. This file must be exactly 16 bytes in size and contains the
unique transport encryption key associated with the domain session launch data.
This is mutually exclusive with the ``--tk`` argument.
``--tk PATH``
TEK/TIK combined file for the domain. This file must be exactly 32 bytes in
size, with the first 16 bytes containing the TEK and the last 16 bytes
containing the TIK. This is mutually exclusive with the ``--tik`` and ``--tek``
arguments.
Libvirt options
---------------
These options are used when connecting to libvirt to automatically obtain
state and configuration information about the domain to be attested.
``-c``, ``--connect URI``
Libvirt connection URI. For the validation to be trustworthy this must be a URI
resolving to a remote virtualization host. This requirement can be overridden
using the ``--insecure`` argument.
``-o``, ``--domain ID|NAME|UUID``
Domain ID, or domain name or domain UUID. Used to identify which libvirt domain
is to have its launch measured. The domain must be running, and would usually
have been started in a paused state, to allow validation to be performed before
guest CPUs begin execution.
``-i``, ``--insecure``
Proceed even if usage scenario is known to be insecure. This allows the program
to connect to a local libvirt hypervisor and rely on file content from the
virtualization host. It also allows the validation to proceed even if the
virtual machine CPUs are not in the initial paused state. The result of the
validation must not be trusted.
``-g``, ``--ignore-config``
Do not attempt to sanity check the domain config. The default behaviour is to
print out errors if identifying configuration elements in the guest XML that
would invalidate the launch measurement. This can help the guest owner to
understand any configuration mistakes that have been made. If the
``--ignore-config`` argument is given, this sanity checking of configuration
will be skipped. The result is that the validation will likely be reported as
failed.
EXAMPLES
========
Fully offline execution
-----------------------
This scenario allows a measurement to be securely validated in a completely
offline state without any connection to the hypervisor host. All required
data items must be provided as command line parameters. This usage model is
considered secure, because all input data is provided by the user.
Validate the measurement of a SEV guest booting from disk:
::
# virt-qemu-sev-validate \
--firmware OVMF.sev.fd \
--tk this-guest-tk.bin \
--measurement Zs2pf19ubFSafpZ2WKkwquXvACx9Wt/BV+eJwQ/taO8jhyIj/F8swFrybR1fZ2ID \
--api-major 0 \
--api-minor 24 \
--build-id 13 \
--policy 3
Validate the measurement of a SEV guest with direct kernel boot:
::
# virt-dom-sev-validate \
--firmware OVMF.sev.fd \
--kernel vmlinuz-5.11.12 \
--initrd initramfs-5.11.12 \
--cmdline "root=/dev/vda1" \
--tk this-guest-tk.bin \
--measurement Zs2pf19ubFSafpZ2WKkwquXvACx9Wt/BV+eJwQ/taO8jhyIj/F8swFrybR1fZ2ID \
--api-major 0 \
--api-minor 24 \
--build-id 13 \
--policy 3
Validate the measurement of a SEV-ES SMP guest booting from disk:
::
# virt-dom-sev-validate \
--firmware OVMF.sev.fd \
--num-cpus 2 \
--vmsa-cpu0 vmsa0.bin \
--vmsa-cpu1 vmsa1.bin \
--tk this-guest-tk.bin \
--measurement Zs2pf19ubFSafpZ2WKkwquXvACx9Wt/BV+eJwQ/taO8jhyIj/F8swFrybR1fZ2ID \
--api-major 0 \
--api-minor 24 \
--build-id 13 \
--policy 7
Fetch from remote libvirt
-------------------------
This scenario allows fetching certain data from a remote hypervisor via a
connection to libvirt. It will aid in debugging by analysing the guest
configuration and reporting anything that could invalidate the measurement
of the guest. This usage model is considered secure, because the limited
information obtained from the untrusted hypervisor cannot be used to change
the result.
Validate the measurement of a SEV guest booting from disk:
::
# virt-qemu-sev-validate \
--connect qemu+ssh://root@some.remote.host/system \
--firmware OVMF.sev.fd \
--tk this-guest-tk.bin \
--domain fedora34x86_64
Validate the measurement of a SEV guest with direct kernel boot:
::
# virt-dom-sev-validate \
--connect qemu+ssh://root@some.remote.host/system \
--firmware OVMF.sev.fd \
--kernel vmlinuz-5.11.12 \
--initrd initramfs-5.11.12 \
--cmdline "root=/dev/vda1" \
--tk this-guest-tk.bin \
--domain fedora34x86_64
Validate the measurement of a SEV-ES SMP guest booting from disk:
::
# virt-dom-sev-validate \
--connect qemu+ssh://root@some.remote.host/system \
--firmware OVMF.sev.fd \
--num-cpus 2 \
--vmsa-cpu0 vmsa0.bin \
--vmsa-cpu1 vmsa1.bin \
--tk this-guest-tk.bin \
--domain fedora34x86_64
Fetch from local libvirt
------------------------
This scenario allows fetching all data from the local hypervisor via a
connection to libvirt. It is only to be used for the purpose of testing,
debugging, or demonstrations, because running on the local hypervisor is not
a secure scenario. To enable this usage, the ``--insecure`` flag must be
specified. Given a pointer to the libvirt guest to validate, all information
needed to perform a validation, except the TIK/TEK pair can be acquired
automatically.
Validate the measurement of a SEV guest booting from disk:
::
# virt-qemu-sev-validate \
--insecure \
--tk this-guest-tk.bin \
--domain fedora34x86_64
Validate the measurement of a SEV guest with direct kernel boot:
::
# virt-dom-sev-validate \
--insecure \
--tk this-guest-tk.bin \
--domain fedora34x86_64
Validate the measurement of a SEV-ES SMP guest booting from disk:
::
# virt-dom-sev-validate \
--insecure \
--num-cpus 2 \
--vmsa-cpu0 vmsa0.bin \
--vmsa-cpu1 vmsa1.bin \
--tk this-guest-tk.bin \
--domain fedora34x86_64
EXIT STATUS
===========
Upon successful attestation of the launch measurement, an exit status of 0 will
be set.
Upon failure to attest the launch measurement one of the following codes will
be set:
* **1** - *Guest measurement did not validate*
Assuming the inputs to this program are correct, the virtual machine launch
has been compromised and it should not be trusted henceforth.
* **2** - *Usage scenario cannot be supported*
The way in which this program has been invoked prevent it from being able to
validate the launch measurement.
* **3** - *Usage scenario is not secure*
The way in which this program has been invoked means that the result of any
launch measurement validation will not be secure.
The program can be reinvoked with ``--insecure`` argument to force a
validation, however, the results of this should not be trusted. This should
only be used for testing, debugging or demonstration purposes, never in a
production deployment.
* **4** - *Domain has incorrect configuration to be measured*
The way in which the guest has been configured prevent this program from being
able to validate the launch measurement. Note that in general the guest
configuration reported by the hypervisor is not trustworthy, so it is
possible this error could be a false positive designed to cause a denial of
service.
This program can be reinvoked with the ``--ignore-config`` argument to skip
the sanity checks on the domain XML. This will likely result in it failing
with an exit code of **1** indicating the measurement is invalid
* **5** - *Domain is in incorrect state to be measured*
The domain has to be running in order to validate a launch measurement.
* **6** - *unexpected error occurred in the code*
A logic flaw in this program means it is unable to complete the validation of
the measurement. This is a bug which should be reported to the maintainers.
AUTHOR
======
Daniel P. Berrangé
BUGS
====
Please report all bugs you discover. This should be done via either:
#. the mailing list
`https://libvirt.org/contact.html <https://libvirt.org/contact.html>`_
#. the bug tracker
`https://libvirt.org/bugs.html <https://libvirt.org/bugs.html>`_
Alternatively, you may report bugs to your software distributor / vendor.
COPYRIGHT
=========
Copyright (C) 2022 by Red Hat, Inc.
LICENSE
=======
``virt-qemu-sev-validate`` is distributed under the terms of the GNU LGPL v2.1+.
This is free software; see the source for copying conditions. There
is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE
SEE ALSO
========
virsh(1), `SEV launch security usage <https://libvirt.org/kbase/launch_security_sev.html>`_,
`https://www.libvirt.org/ <https://www.libvirt.org/>`_
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