parseEfiSignatureList() in attest/internal/events.go does not skip
SignatureHeaderSize vendor bytes before reading EFI_SIGNATURE_LIST
signature entries, violating UEFI specification section 31.4.1.
Impact
For hashSHA256SigGUID lists, attacker-controlled vendor header bytes are appended directly to the trusted SHA256 hash list. A crafted TPM event log can inject arbitrary SHA256 hashes into the verifier's trusted measurement database, allowing a remote attestation verifier to accept a compromised boot state as legitimate — breaking the core integrity guarantee of remote attestation.
Root Cause
After binary.Read(&signatures.Header) reads 28 bytes, buf points to the start of the SignatureHeaderSize vendor bytes. Both entry loops start at sigOffset := 0 instead of sigOffset := SignatureHeaderSize, causing vendor bytes to be read as signature entries.