Heinrich,
On Sat, May 30, 2020 at 09:09:30AM +0200, Heinrich Schuchardt wrote:
On 5/29/20 8:41 AM, AKASHI Takahiro wrote:
In case that a type of certificate in "db" or "dbx" is EFI_CERT_X509_SHA256_GUID, it is actually not a certificate which contains a public key for RSA decryption, but a digest of image to be loaded. If the value matches to a value calculated from a given binary image, it is granted for loading.
With this patch, common digest check code, which used to be used for unsigned image verification, will be extracted from efi_signature_verify_with_sigdb() into efi_signature_lookup_digest(), and extra step for digest check will be added to efi_image_authenticate().
Could you, please, add comments in the code describing this process flow.
All the necessary code is contained in efi_signature_lookup_digest(), but I'll add some comments in efi_image_authenticate().
Thanks, -Takahiro Akashi
Best regards
Heinrich