Add qemu vTPM issuer and validator

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

coordinator/attestation/qemu/validator.go

@@ -0,0 +1,36 @@
+package qemu
+
+import (
+	"crypto"
+
+	"github.com/edgelesssys/constellation/coordinator/attestation/vtpm"
+	"github.com/edgelesssys/constellation/coordinator/oid"
+	"github.com/google/go-tpm/tpm2"
+)
+
+// Validator for QEMU VM attestation.
+type Validator struct {
+	oid.QEMU
+	*vtpm.Validator
+}
+
+// NewValidator initializes a new qemu validator with the provided PCR values.
+func NewValidator(pcrs map[uint32][]byte) *Validator {
+	return &Validator{
+		Validator: vtpm.NewValidator(
+			pcrs,
+			unconditionalTrust,
+			func(attestation vtpm.AttestationDocument) error { return nil },
+			vtpm.VerifyPKCS1v15,
+		),
+	}
+}
+
+// unconditionalTrust returns the given public key as the trusted attestation key.
+func unconditionalTrust(akPub, instanceInfo []byte) (crypto.PublicKey, error) {
+	pubArea, err := tpm2.DecodePublic(akPub)
+	if err != nil {
+		return nil, err
+	}
+	return pubArea.Key()
+}