On 12/16/21 08:02, Daniel P. Berrangé wrote:
On Tue, Dec 14, 2021 at 09:46:06PM -0700, Jim Fehlig wrote:
After attesting a domain with the help of domlaunchsecinfo,
domsetlaunchsecstate can be used to set a secret in the guest
domain's memory prior to running the vcpus.
Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---
Some questions and RFC regarding this patch:
I'm not really fond of the command and function names and would appreciate
suggestions :-).
I'm honestly not too fussed about the naming. THis command is really
just about feature complete API coverage. I doubt many people will
actually use virsh for this, instead they'll want a program that
queries the measurement, verifies it and injects secret all in one
go.
Also, is reading the secret header and secret from a file sufficient? The
sev-tool 'package_secret' command writes the secret to a file.
Fine IMHO.
Lastly, I'm not sure what sizes to expect for secret and secret header. I
may have overlooked it, but didn't find anything related to the size in the
docs. I've temporarily set it to VSH_MAX_XML_FILE until we know a reasonable
value.
I took another look at the API spec and section "6.6 LAUNCH_SECRET", subsection
"6.6.2 Parameters" describes the parameters to the LUANCH_SECRET command and the
layout the the secret header. IIUC, GUEST_PADDR and GUEST_LENGTH tell where to
put the secret. GUEST_LENGTH cannot be greater than 16KB. And the secret header
looks to be 104 bytes.
https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf
I'm not too sure either, but as a general point, IMHO, almost all
our use of virFileReadAll has no functional or security need for
us to supply a limit at all.
We really ought to just make it accept '-1' as a limit and treat
that as unlimited. Meanwhile I'd suggest just letting it be
1 MB which is way bigger than i expect this data will be.
Given the above, 1MB is overkill. But still go with it as a safer, more
future-proof value?
Regards,
Jim
You can only DoS yourself with virsh, and you'll be limited by
the RPC protocol wire limit.
docs/manpages/virsh.rst | 25 ++++++++++
tools/virsh-domain.c | 107 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 132 insertions(+)
With a 1 MB or similar size limit
Reviewed-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
Regards,
Daniel
