attestation: tdx issuer/validator (#1265)

* Add TDX validator

* Add TDX issuer

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

internal/attestation/tdx/validator.go

@@ -0,0 +1,94 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package tdx
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"github.com/edgelesssys/constellation/v2/internal/attestation"
+	"github.com/edgelesssys/constellation/v2/internal/attestation/measurements"
+	"github.com/edgelesssys/constellation/v2/internal/config"
+	"github.com/edgelesssys/constellation/v2/internal/variant"
+	"github.com/edgelesssys/go-tdx-qpl/verification"
+	"github.com/edgelesssys/go-tdx-qpl/verification/types"
+)
+
+type tdxVerifier interface {
+	Verify(ctx context.Context, quote []byte) (types.SGXQuote4, error)
+}
+
+// Validator is the TDX attestation validator.
+type Validator struct {
+	variant.QEMUTDX
+
+	tdx      tdxVerifier
+	expected measurements.M
+
+	log attestation.Logger
+}
+
+// NewValidator initializes a new TDX Validator.
+func NewValidator(cfg *config.QEMUTDX, log attestation.Logger) *Validator {
+	if log == nil {
+		log = attestation.NOPLogger{}
+	}
+
+	return &Validator{
+		tdx:      verification.New(),
+		expected: cfg.Measurements,
+		log:      log,
+	}
+}
+
+// Validate validates the given attestation document using TDX attestation.
+func (v *Validator) Validate(ctx context.Context, attDocRaw []byte, nonce []byte) (userData []byte, err error) {
+	v.log.Infof("Validating attestation document")
+	defer func() {
+		if err != nil {
+			v.log.Warnf("Failed to validate attestation document: %s", err)
+		}
+	}()
+
+	var attDoc tdxAttestationDocument
+	if err := json.Unmarshal(attDocRaw, &attDoc); err != nil {
+		return nil, fmt.Errorf("unmarshaling attestation document: %w", err)
+	}
+
+	// Verify the quote.
+	quote, err := v.tdx.Verify(ctx, attDoc.RawQuote)
+	if err != nil {
+		return nil, fmt.Errorf("verifying TDX quote: %w", err)
+	}
+
+	// Report data
+	extraData := attestation.MakeExtraData(attDoc.UserData, nonce)
+	if !attestation.CompareExtraData(quote.Body.ReportData[:], extraData) {
+		return nil, fmt.Errorf("report data in TDX quote does not match provided nonce")
+	}
+
+	// Convert RTMRs and MRTD to map.
+	tdMeasure := make(map[uint32][]byte, 5)
+	tdMeasure[0] = quote.Body.MRTD[:]
+	for idx := 0; idx < len(quote.Body.RTMR); idx++ {
+		tdMeasure[uint32(idx+1)] = quote.Body.RTMR[idx][:]
+	}
+
+	// Verify the quote against the expected measurements.
+	for idx, ex := range v.expected {
+		if !bytes.Equal(ex.Expected, tdMeasure[idx]) {
+			if !ex.ValidationOpt {
+				return nil, fmt.Errorf("untrusted TD measurement value at index %d", idx)
+			}
+			v.log.Warnf("Encountered untrusted TD measurement value at index %d", idx)
+		}
+	}
+
+	return attDoc.UserData, nil
+}