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

Sun Oct 16 19:06:17 UTC 2022

On 10/7/22 7:42 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.
> 
> 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

After the fix I mentioned on patch 7, the script worked for my sev,
sev-es, sev-es + kernel setup, with vmsa passed in and vmsa generated.

Attached is some pylint output, nothing really serious:

- Cole
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************* Module virt-qemu-sev-validate
tools/virt-qemu-sev-validate.py:88:35: W0622: Redefining built-in 'format' (redefined-builtin)
tools/virt-qemu-sev-validate.py:101:41: W0622: Redefining built-in 'format' (redefined-builtin)
tools/virt-qemu-sev-validate.py:151:16: C0200: Consider using enumerate instead of iterating with range and len (consider-using-enumerate)
tools/virt-qemu-sev-validate.py:351:8: W0201: Attribute 'cr0' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:352:8: W0201: Attribute 'rip' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:354:8: W0201: Attribute 'cs_selector' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:355:8: W0201: Attribute 'cs_base' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:356:8: W0201: Attribute 'cs_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:358:8: W0201: Attribute 'ds_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:360:8: W0201: Attribute 'es_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:361:8: W0201: Attribute 'fs_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:362:8: W0201: Attribute 'gs_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:363:8: W0201: Attribute 'ss_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:365:8: W0201: Attribute 'gdtr_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:366:8: W0201: Attribute 'idtr_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:368:8: W0201: Attribute 'ldtr_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:369:8: W0201: Attribute 'tr_limit' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:371:8: W0201: Attribute 'dr6' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:372:8: W0201: Attribute 'dr7' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:373:8: W0201: Attribute 'rflags' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:374:8: W0201: Attribute 'xcr0' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:379:8: W0201: Attribute 'cr4' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:382:8: W0201: Attribute 'efer' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:386:8: W0201: Attribute 'ldtr_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:403:8: W0201: Attribute 'ldtr_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:390:8: W0201: Attribute 'tr_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:405:8: W0201: Attribute 'tr_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:393:8: W0201: Attribute 'g_pat' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:433:8: W0201: Attribute 'g_pat' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:407:8: W0201: Attribute 'cs_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:412:8: W0201: Attribute 'ds_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:416:8: W0201: Attribute 'es_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:420:8: W0201: Attribute 'ss_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:424:8: W0201: Attribute 'fs_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:428:8: W0201: Attribute 'gs_attrib' defined outside __init__ (attribute-defined-outside-init)
tools/virt-qemu-sev-validate.py:542:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:564:12: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:569:12: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:571:27: W0622: Redefining built-in 'str' (redefined-builtin)
tools/virt-qemu-sev-validate.py:573:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:639:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:642:12: W0715: Exception arguments suggest string formatting might be intended (raising-format-tuple)
tools/virt-qemu-sev-validate.py:647:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:650:12: W0715: Exception arguments suggest string formatting might be intended (raising-format-tuple)
tools/virt-qemu-sev-validate.py:658:12: W0715: Exception arguments suggest string formatting might be intended (raising-format-tuple)
tools/virt-qemu-sev-validate.py:663:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:664:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:669:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:683:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:688:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:703:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:708:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:725:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:740:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:768:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:772:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:773:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:831:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:832:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:938:8: W1201: Use lazy % formatting in logging functions (logging-not-lazy)
tools/virt-qemu-sev-validate.py:947:14: I1101: Module 'lxml.etree' has no 'fromstring' member, but source is unavailable. Consider adding this module to extension-pkg-allow-list if you want to perform analysis based on run-time introspection of living objects. (c-extension-no-member)
tools/virt-qemu-sev-validate.py:1025:18: I1101: Module 'lxml.etree' has no 'fromstring' member, but source is unavailable. Consider adding this module to extension-pkg-allow-list if you want to perform analysis based on run-time introspection of living objects. (c-extension-no-member)
tools/virt-qemu-sev-validate.py:1122:16: W0621: Redefining name 'args' from outer scope (line 1251) (redefined-outer-name)
tools/virt-qemu-sev-validate.py:1186:11: W0621: Redefining name 'args' from outer scope (line 1251) (redefined-outer-name)
tools/virt-qemu-sev-validate.py:43:0: C0411: standard import "import logging" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:45:0: C0411: standard import "import os" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:46:0: C0411: standard import "import re" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:47:0: C0411: standard import "import socket" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:48:0: C0411: standard import "from struct import pack" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:49:0: C0411: standard import "import sys" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:50:0: C0411: standard import "import traceback" should be placed before "import libvirt" (wrong-import-order)
tools/virt-qemu-sev-validate.py:51:0: C0411: standard import "from uuid import UUID" should be placed before "import libvirt" (wrong-import-order)