attestation: clear certificate cache in azure snp

The unittest was flacky as testcases with valid certs
in the getter property lead to those certs being cached
inside the trust module. Other testcases however,
may want to explicitly use invalid certs. The cache
interferes with this.

Co-authored-by: Moritz Sanft <ms@edgeless.systems>

internal/attestation/azure/snp/BUILD.bazel

@@ -60,6 +60,7 @@ go_test(
         "@com_github_google_go_sev_guest//proto/sevsnp",
         "@com_github_google_go_sev_guest//validate",
         "@com_github_google_go_sev_guest//verify",
+        "@com_github_google_go_sev_guest//verify/trust",
         "@com_github_google_go_tpm//legacy/tpm2",
         "@com_github_google_go_tpm_tools//client",
         "@com_github_google_go_tpm_tools//proto/attest",

internal/attestation/azure/snp/validator_test.go

@@ -34,6 +34,7 @@ import (
 	spb "github.com/google/go-sev-guest/proto/sevsnp"
 	"github.com/google/go-sev-guest/validate"
 	"github.com/google/go-sev-guest/verify"
+	"github.com/google/go-sev-guest/verify/trust"
 	"github.com/google/go-tpm-tools/client"
 	"github.com/google/go-tpm-tools/proto/attest"
 	"github.com/google/go-tpm/legacy/tpm2"
@@ -284,6 +285,9 @@ func TestInstanceInfoAttestation(t *testing.T) {
 			assert := assert.New(t)
 			require := require.New(t)
 
+			// This is important. Without this call, the trust module caches certificates across testcases.
+			defer trust.ClearProductCertCache()
+
 			instanceInfo := azureInstanceInfo{
 				AttestationReport: tc.report,
 				CertChain:         tc.certChain,
@@ -564,22 +568,21 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 	if cgo == "0" {
 		t.Skip("skipping test because CGO is disabled and tpm simulator requires it")
 	}
-	require := require.New(t)
 
 	tpm, err := simulator.OpenSimulatedTPM()
-	require.NoError(err)
+	require.NoError(t, err)
 	defer tpm.Close()
 	key, err := client.AttestationKeyRSA(tpm)
-	require.NoError(err)
+	require.NoError(t, err)
 	defer key.Close()
 	akPub, err := key.PublicArea().Encode()
-	require.NoError(err)
+	require.NoError(t, err)
 
 	defaultCfg := config.DefaultForAzureSEVSNP()
 	defaultReport := hex.EncodeToString(testdata.AttestationReport)
 	defaultRuntimeData := hex.EncodeToString(testdata.RuntimeData)
 	defaultIDKeyDigestOld, err := hex.DecodeString("57e229e0ffe5fa92d0faddff6cae0e61c926fc9ef9afd20a8b8cfcf7129db9338cbe5bf3f6987733a2bf65d06dc38fc1")
-	require.NoError(err)
+	require.NoError(t, err)
 	defaultIDKeyDigest := idkeydigest.NewList([][]byte{defaultIDKeyDigestOld})
 	defaultVerifier := &stubAttestationVerifier{}
 	skipVerifier := &stubAttestationVerifier{skipCheck: true}
@@ -588,12 +591,12 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 	// reportTransformer unpacks the hex-encoded report, applies the given transformations and re-encodes it.
 	reportTransformer := func(reportHex string, transformations func(*spb.Report)) string {
 		rawReport, err := hex.DecodeString(reportHex)
-		require.NoError(err)
+		require.NoError(t, err)
 		report, err := abi.ReportToProto(rawReport)
-		require.NoError(err)
+		require.NoError(t, err)
 		transformations(report)
 		reportBytes, err := abi.ReportToAbiBytes(report)
-		require.NoError(err)
+		require.NoError(t, err)
 		return hex.EncodeToString(reportBytes)
 	}
 
@@ -746,6 +749,7 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 				},
 				nil,
 			),
+			wantErr: true,
 		},
 		"invalid runtime data": {
 			report:               defaultReport,
@@ -821,7 +825,7 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 				defaultCfg.MicrocodeVersion.Value = 10
 				launchTcb.UcodeSpl = 9
 				newLaunchTcb, err := kds.ComposeTCBParts(launchTcb)
-				require.NoError(err)
+				require.NoError(t, err)
 				r.LaunchTcb = uint64(newLaunchTcb)
 			}),
 			runtimeData:          defaultRuntimeData,
@@ -845,7 +849,7 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 				reportedTcb := kds.DecomposeTCBVersion(kds.TCBVersion(r.ReportedTcb))
 				reportedTcb.UcodeSpl = defaultCfg.MicrocodeVersion.Value - 1
 				newReportedTcb, err := kds.ComposeTCBParts(reportedTcb)
-				require.NoError(err)
+				require.NoError(t, err)
 				r.ReportedTcb = uint64(newReportedTcb)
 			}),
 			runtimeData:          defaultRuntimeData,
@@ -889,7 +893,7 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 				currentTcb := kds.DecomposeTCBVersion(kds.TCBVersion(r.CurrentTcb))
 				currentTcb.UcodeSpl = 0x5c // testdata.AzureThimVCEK has ucode version 0x5d
 				newCurrentTcb, err := kds.ComposeTCBParts(currentTcb)
-				require.NoError(err)
+				require.NoError(t, err)
 				r.CurrentTcb = uint64(newCurrentTcb)
 			}),
 			runtimeData:          defaultRuntimeData,
@@ -976,14 +980,16 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 	for name, tc := range testCases {
 		t.Run(name, func(t *testing.T) {
 			assert := assert.New(t)
+			require := require.New(t)
+
+			// This is important. Without this call, the trust module caches certificates across testcases.
+			defer trust.ClearProductCertCache()
 
 			instanceInfo, err := newStubAzureInstanceInfo(tc.vcek, tc.certChain, tc.report, tc.runtimeData)
-			assert.NoError(err)
+			require.NoError(err)
 
 			statement, err := json.Marshal(instanceInfo)
-			if err != nil {
+			require.NoError(err)
-				assert.Error(err)
-			}
 
 			attDoc := vtpm.AttestationDocument{
 				InstanceInfo: statement,
@@ -1008,12 +1014,12 @@ func TestTrustedKeyFromSNP(t *testing.T) {
 
 			key, err := validator.getTrustedKey(context.Background(), attDoc, nil)
 			if tc.wantErr {
-				require.Error(err)
+				assert.Error(err)
 				if tc.assertion != nil {
 					tc.assertion(assert, err)
 				}
 			} else {
-				require.NoError(err)
+				assert.NoError(err)
 				assert.NotNil(key)
 			}
 		})