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@suse.com> ---
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@redhat.com>
Regards, Daniel