modified_nvar.go

// Copyright 2023 Meta Platforms, Inc. and affiliates.
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package testcase

import (
	"bytes"
	"context"
	"fmt"

	"github.com/immune-gmbh/attestation-sdk/tools/hwsecvalidator/testcase/errors"
	"github.com/immune-gmbh/attestation-sdk/tools/hwsecvalidator/testcase/types"
	"github.com/immune-gmbh/attestation-sdk/tools/hwsecvalidator/testcase/validator"

	"github.com/9elements/converged-security-suite/v2/pkg/uefi"
	"github.com/klauspost/cpuid/v2"
	"github.com/linuxboot/fiano/pkg/guid"
)

// ModifiedNVAR is the test case when NVAR is modified. It should not affect
// the behavior.
type ModifiedNVAR struct{}

var (
	nvarGUID = *guid.MustParse("CEF5B9A3-476D-497F-9FDC-E98143E0422C")
)

// Setup implements TestCase.
func (t ModifiedNVAR) Setup(ctx context.Context, image []byte) error {
	fw, err := uefi.ParseUEFIFirmwareBytes(image)
	if err != nil {
		return errors.ErrParseFirmware{Err: err}
	}

	nodes, err := fw.GetByGUID(nvarGUID)
	if err != nil {
		return errors.ErrLookupGUID{GUID: nvarGUID, Err: err}
	}

	if len(nodes) == 0 {
		return errors.ErrUnexpectedGUIDCount{GUID: nvarGUID, Expected: 1, Actual: len(nodes)}
	}
	nvarVolume := nodes[0]

	idx := t.findPadding(nvarVolume.Buf(), 64)
	if idx < 0 {
		return errors.ErrPaddingNotFound{}
	}

	image[nvarVolume.Offset+uint64(idx)+32] = ^image[nvarVolume.Offset+uint64(idx)+32]
	return nil
}

func (t ModifiedNVAR) findPadding(b []byte, size uint) int {
	magic := make([]byte, size)
	for idx := range magic {
		magic[idx] = 0xff
	}
	return bytes.Index(b, magic)
}

// Matches implements TestCase
func (ModifiedNVAR) Matches(fwInfo types.FirmwareInfoProvider) bool {
	isIntel, err := types.IsArchitecture(fwInfo, cpuid.Intel)
	if err != nil {
		panic(fmt.Sprintf("cannot determine if the architecture is Intel: %v", err))
	}
	return isIntel
}

// Validate implements TestCase.
func (t ModifiedNVAR) Validate(ctx context.Context, origImage []byte, opts ...types.Option) error {
	info, err := validator.GetValidationInfo(ctx, t, origImage, opts)
	if err != nil {
		return errors.ErrValidationInfo{Err: err}
	}

	return validator.CommonHostBootUpExpected().Validate(ctx, info)
}

// Severity implements TestCase.
func (ModifiedNVAR) Severity() types.Severity {
	return types.SeverityInfo
}

var _ types.TestCase = ModifiedNVAR{}