Peter Gonda 47894e0fa6 virt/sev-guest: Prevent IV reuse in the SNP guest driver ... The AMD Secure Processor (ASP) and an SNP guest use a series of AES-GCM keys called VMPCKs to communicate securely with each other. The IV to this scheme is a sequence number that both the ASP and the guest track. Currently, this sequence number in a guest request must exactly match the sequence number tracked by the ASP. This means that if the guest sees an error from the host during a request it can only retry that exact request or disable the VMPCK to prevent an IV reuse. AES-GCM cannot tolerate IV reuse, see: "Authentication Failures in NIST version of GCM" - Antoine Joux et al. In order to address this, make handle_guest_request() delete the VMPCK on any non successful return. To allow userspace querying the cert_data length make handle_guest_request() save the number of pages required by the host, then have handle_guest_request() retry the request without requesting the extended data, then return the number of pages required back to userspace. [ bp: Massage, incorporate Tom's review comments. ] Fixes: fce96cf044 ("virt: Add SEV-SNP guest driver") Reported-by: Peter Gonda <pgonda@google.com> Signed-off-by: Peter Gonda <pgonda@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Cc: stable@kernel.org Link: https://lore.kernel.org/r/20221116175558.2373112-1-pgonda@google.com		2022-11-21 11:03:40 +01:00
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efi_secret
sev-guest	virt/sev-guest: Prevent IV reuse in the SNP guest driver	2022-11-21 11:03:40 +01:00