snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/xds/bootstrap/tlscreds/bundle.go

@@ -0,0 +1,194 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package tlscreds implements mTLS Credentials in xDS Bootstrap File.
+// See gRFC A65: github.com/grpc/proposal/blob/master/A65-xds-mtls-creds-in-bootstrap.md.
+package tlscreds
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/spiffe/go-spiffe/v2/bundle/spiffebundle"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/credentials/tls/certprovider"
+	"google.golang.org/grpc/credentials/tls/certprovider/pemfile"
+	"google.golang.org/grpc/internal/credentials/spiffe"
+	"google.golang.org/grpc/internal/envconfig"
+)
+
+// bundle is an implementation of credentials.Bundle which implements mTLS
+// Credentials in xDS Bootstrap File.
+type bundle struct {
+	transportCredentials credentials.TransportCredentials
+}
+
+// NewBundle returns a credentials.Bundle which implements mTLS Credentials in xDS
+// Bootstrap File. It delegates certificate loading to a file_watcher provider
+// if either client certificates or server root CA is specified. The second
+// return value is a close func that should be called when the caller no longer
+// needs this bundle.
+// See gRFC A65: github.com/grpc/proposal/blob/master/A65-xds-mtls-creds-in-bootstrap.md
+func NewBundle(jd json.RawMessage) (credentials.Bundle, func(), error) {
+	cfg := &struct {
+		CertificateFile          string `json:"certificate_file"`
+		CACertificateFile        string `json:"ca_certificate_file"`
+		PrivateKeyFile           string `json:"private_key_file"`
+		SPIFFETrustBundleMapFile string `json:"spiffe_trust_bundle_map_file"`
+	}{}
+
+	if jd != nil {
+		if err := json.Unmarshal(jd, cfg); err != nil {
+			return nil, nil, fmt.Errorf("failed to unmarshal config: %v", err)
+		}
+	} // Else the config field is absent. Treat it as an empty config.
+
+	if !envconfig.XDSSPIFFEEnabled {
+		cfg.SPIFFETrustBundleMapFile = ""
+	}
+	if cfg.CACertificateFile == "" && cfg.CertificateFile == "" && cfg.PrivateKeyFile == "" && cfg.SPIFFETrustBundleMapFile == "" {
+		// We cannot use (and do not need) a file_watcher provider in this case,
+		// and can simply directly use the TLS transport credentials.
+		// Quoting A65:
+		//
+		// > The only difference between the file-watcher certificate provider
+		// > config and this one is that in the file-watcher certificate
+		// > provider, at least one of the "certificate_file" or
+		// > "ca_certificate_file" fields must be specified, whereas in this
+		// > configuration, it is acceptable to specify neither one.
+		// Further, with the introduction of SPIFFE Trust Map support, we also
+		// check for this value.
+		return &bundle{transportCredentials: credentials.NewTLS(&tls.Config{})}, func() {}, nil
+	}
+	// Otherwise we need to use a file_watcher provider to watch the CA,
+	// private and public keys.
+
+	// The pemfile plugin (file_watcher) currently ignores BuildOptions.
+	provider, err := certprovider.GetProvider(pemfile.PluginName, jd, certprovider.BuildOptions{})
+	if err != nil {
+		return nil, nil, err
+	}
+	return &bundle{
+		transportCredentials: &reloadingCreds{provider: provider},
+	}, sync.OnceFunc(func() { provider.Close() }), nil
+}
+
+func (t *bundle) TransportCredentials() credentials.TransportCredentials {
+	return t.transportCredentials
+}
+
+func (t *bundle) PerRPCCredentials() credentials.PerRPCCredentials {
+	// mTLS provides transport credentials only. There are no per-RPC
+	// credentials.
+	return nil
+}
+
+func (t *bundle) NewWithMode(string) (credentials.Bundle, error) {
+	// This bundle has a single mode which only uses TLS transport credentials,
+	// so there is no legitimate case where callers would call NewWithMode.
+	return nil, fmt.Errorf("xDS TLS credentials only support one mode")
+}
+
+// reloadingCreds is a credentials.TransportCredentials for client
+// side mTLS that reloads the server root CA certificate and the client
+// certificates from the provider on every client handshake. This is necessary
+// because the standard TLS credentials do not support reloading CA
+// certificates.
+type reloadingCreds struct {
+	provider certprovider.Provider
+}
+
+func (c *reloadingCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	km, err := c.provider.KeyMaterial(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+	var config *tls.Config
+	if km.SPIFFEBundleMap != nil {
+		config = &tls.Config{
+			InsecureSkipVerify:    true,
+			VerifyPeerCertificate: buildSPIFFEVerifyFunc(km.SPIFFEBundleMap),
+			Certificates:          km.Certs,
+		}
+	} else {
+		config = &tls.Config{
+			RootCAs:      km.Roots,
+			Certificates: km.Certs,
+		}
+	}
+	return credentials.NewTLS(config).ClientHandshake(ctx, authority, rawConn)
+}
+
+func (c *reloadingCreds) Info() credentials.ProtocolInfo {
+	return credentials.ProtocolInfo{SecurityProtocol: "tls"}
+}
+
+func (c *reloadingCreds) Clone() credentials.TransportCredentials {
+	return &reloadingCreds{provider: c.provider}
+}
+
+func (c *reloadingCreds) OverrideServerName(string) error {
+	return errors.New("overriding server name is not supported by xDS client TLS credentials")
+}
+
+func (c *reloadingCreds) ServerHandshake(net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	return nil, nil, errors.New("server handshake is not supported by xDS client TLS credentials")
+}
+
+func buildSPIFFEVerifyFunc(spiffeBundleMap map[string]*spiffebundle.Bundle) func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+	return func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
+		rawCertList := make([]*x509.Certificate, len(rawCerts))
+		for i, asn1Data := range rawCerts {
+			cert, err := x509.ParseCertificate(asn1Data)
+			if err != nil {
+				return fmt.Errorf("spiffe: verify function could not parse input certificate: %v", err)
+			}
+			rawCertList[i] = cert
+		}
+		if len(rawCertList) == 0 {
+			return fmt.Errorf("spiffe: verify function has no valid input certificates")
+		}
+		leafCert := rawCertList[0]
+		roots, err := spiffe.GetRootsFromSPIFFEBundleMap(spiffeBundleMap, leafCert)
+		if err != nil {
+			return err
+		}
+
+		opts := x509.VerifyOptions{
+			Roots:         roots,
+			CurrentTime:   time.Now(),
+			Intermediates: x509.NewCertPool(),
+		}
+
+		for _, cert := range rawCertList[1:] {
+			opts.Intermediates.AddCert(cert)
+		}
+		// The verified chain is (surprisingly) unused.
+		if _, err = rawCertList[0].Verify(opts); err != nil {
+			return fmt.Errorf("spiffe: x509 certificate Verify failed: %v", err)
+		}
+		return nil
+	}
+}

internal/xds/bootstrap/tlscreds/bundle_ext_test.go

@@ -0,0 +1,520 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package tlscreds_test
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/internal/envconfig"
+	"google.golang.org/grpc/internal/grpctest"
+	"google.golang.org/grpc/internal/stubserver"
+	"google.golang.org/grpc/internal/testutils"
+	"google.golang.org/grpc/internal/xds/bootstrap/tlscreds"
+	testgrpc "google.golang.org/grpc/interop/grpc_testing"
+	testpb "google.golang.org/grpc/interop/grpc_testing"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/testdata"
+)
+
+const defaultTestTimeout = 5 * time.Second
+
+type s struct {
+	grpctest.Tester
+}
+
+func Test(t *testing.T) {
+	grpctest.RunSubTests(t, s{})
+}
+
+type Closable interface {
+	Close()
+}
+
+func (s) TestValidTlsBuilder(t *testing.T) {
+	caCert := testdata.Path("x509/server_ca_cert.pem")
+	clientCert := testdata.Path("x509/client1_cert.pem")
+	clientKey := testdata.Path("x509/client1_key.pem")
+	clientSpiffeBundle := testdata.Path("spiffe_end2end/client_spiffebundle.json")
+	tests := []struct {
+		name string
+		jd   string
+	}{
+		{
+			name: "Absent configuration",
+			jd:   `null`,
+		},
+		{
+			name: "Empty configuration",
+			jd:   `{}`,
+		},
+		{
+			name: "Only CA certificate chain",
+			jd:   fmt.Sprintf(`{"ca_certificate_file": "%s"}`, caCert),
+		},
+		{
+			name: "Only private key and certificate chain",
+			jd:   fmt.Sprintf(`{"certificate_file":"%s","private_key_file":"%s"}`, clientCert, clientKey),
+		},
+		{
+			name: "CA chain, private key and certificate chain",
+			jd:   fmt.Sprintf(`{"ca_certificate_file":"%s","certificate_file":"%s","private_key_file":"%s"}`, caCert, clientCert, clientKey),
+		},
+		{
+			name: "Only refresh interval", jd: `{"refresh_interval": "1s"}`,
+		},
+		{
+			name: "Refresh interval and CA certificate chain",
+			jd:   fmt.Sprintf(`{"refresh_interval": "1s","ca_certificate_file": "%s"}`, caCert),
+		},
+		{
+			name: "Refresh interval, private key and certificate chain",
+			jd:   fmt.Sprintf(`{"refresh_interval": "1s","certificate_file":"%s","private_key_file":"%s"}`, clientCert, clientKey),
+		},
+		{
+			name: "Refresh interval, CA chain, private key and certificate chain",
+			jd:   fmt.Sprintf(`{"refresh_interval": "1s","ca_certificate_file":"%s","certificate_file":"%s","private_key_file":"%s"}`, caCert, clientCert, clientKey),
+		},
+		{
+			name: "Refresh interval, CA chain, private key, certificate chain, spiffe bundle",
+			jd:   fmt.Sprintf(`{"refresh_interval": "1s","ca_certificate_file":"%s","certificate_file":"%s","private_key_file":"%s","spiffe_trust_bundle_map_file":"%s"}`, caCert, clientCert, clientKey, clientSpiffeBundle),
+		},
+		{
+			name: "Unknown field",
+			jd:   `{"unknown_field": "foo"}`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			msg := json.RawMessage(test.jd)
+			_, stop, err := tlscreds.NewBundle(msg)
+			if err != nil {
+				t.Fatalf("NewBundle(%s) returned error %s when expected to succeed", test.jd, err)
+			}
+			stop()
+		})
+	}
+}
+
+func (s) TestInvalidTlsBuilder(t *testing.T) {
+	tests := []struct {
+		name, jd, wantErrPrefix string
+	}{
+		{
+			name:          "Wrong type in json",
+			jd:            `{"ca_certificate_file": 1}`,
+			wantErrPrefix: "failed to unmarshal config:"},
+		{
+			name:          "Missing private key",
+			jd:            fmt.Sprintf(`{"certificate_file":"%s"}`, testdata.Path("x509/server_cert.pem")),
+			wantErrPrefix: "pemfile: private key file and identity cert file should be both specified or not specified",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			msg := json.RawMessage(test.jd)
+			_, stop, err := tlscreds.NewBundle(msg)
+			if err == nil || !strings.HasPrefix(err.Error(), test.wantErrPrefix) {
+				if stop != nil {
+					stop()
+				}
+				t.Fatalf("NewBundle(%s): got error %s, want an error with prefix %s", msg, err, test.wantErrPrefix)
+			}
+		})
+	}
+}
+
+func (s) TestCaReloading(t *testing.T) {
+	serverCa, err := os.ReadFile(testdata.Path("x509/server_ca_cert.pem"))
+	if err != nil {
+		t.Fatalf("Failed to read test CA cert: %s", err)
+	}
+
+	// Write CA certs to a temporary file so that we can modify it later.
+	caPath := t.TempDir() + "/ca.pem"
+	if err = os.WriteFile(caPath, serverCa, 0644); err != nil {
+		t.Fatalf("Failed to write test CA cert: %v", err)
+	}
+	cfg := fmt.Sprintf(`{
+		"ca_certificate_file": "%s",
+		"refresh_interval": ".01s"
+	}`, caPath)
+	tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+	if err != nil {
+		t.Fatalf("Failed to create TLS bundle: %v", err)
+	}
+	defer stop()
+
+	serverCredentials := grpc.Creds(testutils.CreateServerTLSCredentials(t, tls.NoClientCert))
+	server := stubserver.StartTestService(t, nil, serverCredentials)
+
+	conn, err := grpc.NewClient(
+		server.Address,
+		grpc.WithCredentialsBundle(tlsBundle),
+		grpc.WithAuthority("x.test.example.com"),
+	)
+	if err != nil {
+		t.Fatalf("Error dialing: %v", err)
+	}
+	defer conn.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	client := testgrpc.NewTestServiceClient(conn)
+	if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Errorf("Error calling EmptyCall: %v", err)
+	}
+	// close the server and create a new one to force client to do a new
+	// handshake.
+	server.Stop()
+
+	invalidCa, err := os.ReadFile(testdata.Path("ca.pem"))
+	if err != nil {
+		t.Fatalf("Failed to read test CA cert: %v", err)
+	}
+	// unload root cert
+	err = os.WriteFile(caPath, invalidCa, 0644)
+	if err != nil {
+		t.Fatalf("Failed to write test CA cert: %v", err)
+	}
+	for ; ctx.Err() == nil; <-time.After(10 * time.Millisecond) {
+		ss := stubserver.StubServer{
+			Address:    server.Address,
+			EmptyCallF: func(context.Context, *testpb.Empty) (*testpb.Empty, error) { return &testpb.Empty{}, nil },
+		}
+		server = stubserver.StartTestService(t, &ss, serverCredentials)
+
+		// Client handshake should eventually fail because the client CA was
+		// reloaded, and thus the server cert is signed by an unknown CA.
+		t.Log(server)
+		_, err = client.EmptyCall(ctx, &testpb.Empty{})
+		const wantErr = "certificate signed by unknown authority"
+		if status.Code(err) == codes.Unavailable && strings.Contains(err.Error(), wantErr) {
+			// Certs have reloaded.
+			server.Stop()
+			break
+		}
+		t.Logf("EmptyCall() got err: %s, want code: %s, want err: %s", err, codes.Unavailable, wantErr)
+		server.Stop()
+	}
+	if ctx.Err() != nil {
+		t.Errorf("Timed out waiting for CA certs reloading")
+	}
+}
+
+// Test_SPIFFE_Reloading sets up a client and server. The client is configured
+// to use a SPIFFE bundle map, and the server is configured to use TLS creds
+// compatible with this bundle. A handshake is performed and connection is
+// expected to be successful. Then we change the client's SPIFFE Bundle Map file
+// on disk to one that should fail with the server's credentials. This change
+// should be picked up by the client via our file reloading. Another handshake
+// is performed and checked for failure, ensuring that gRPC is correctly using
+// the changed-on-disk bundle map.
+func (s) Test_SPIFFE_Reloading(t *testing.T) {
+	testutils.SetEnvConfig(t, &envconfig.XDSSPIFFEEnabled, true)
+	clientSPIFFEBundle, err := os.ReadFile(testdata.Path("spiffe_end2end/client_spiffebundle.json"))
+	if err != nil {
+		t.Fatalf("Failed to read test SPIFFE bundle: %v", err)
+	}
+
+	// Write CA certs to a temporary file so that we can modify it later.
+	spiffePath := t.TempDir() + "/client_spiffe.json"
+	if err = os.WriteFile(spiffePath, clientSPIFFEBundle, 0644); err != nil {
+		t.Fatalf("Failed to write test SPIFFE Bundle %v: %v", clientSPIFFEBundle, err)
+	}
+	cfg := fmt.Sprintf(`{
+		"spiffe_trust_bundle_map_file": "%s",
+		"refresh_interval": ".01s"
+	}`, spiffePath)
+	tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+	if err != nil {
+		t.Fatalf("Failed to create TLS bundle: %v", err)
+	}
+	defer stop()
+
+	l, err := testutils.LocalTCPListener()
+	if err != nil {
+		t.Fatalf("testutils.LocalTCPListener() failed: %v", err)
+	}
+	lis := testutils.NewRestartableListener(l)
+	defer lis.Close()
+	ss := stubserver.StubServer{
+		Listener:   lis,
+		EmptyCallF: func(context.Context, *testpb.Empty) (*testpb.Empty, error) { return &testpb.Empty{}, nil },
+	}
+
+	serverCredentials := grpc.Creds(testutils.CreateServerTLSCredentialsCompatibleWithSPIFFE(t, tls.NoClientCert))
+	server := stubserver.StartTestService(t, &ss, serverCredentials)
+
+	defer server.Stop()
+
+	conn, err := grpc.NewClient(
+		server.Address,
+		grpc.WithCredentialsBundle(tlsBundle),
+		grpc.WithAuthority("x.test.example.com"),
+	)
+	if err != nil {
+		t.Fatalf("grpc.NewClient(%q) failed: %v", server.Address, err)
+	}
+	defer conn.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	client := testgrpc.NewTestServiceClient(conn)
+	if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Errorf("Error calling EmptyCall: %v", err)
+	}
+
+	// Setup the wrong bundle to be reloaded
+	wrongBundle, err := os.ReadFile(testdata.Path("spiffe_end2end/server_spiffebundle.json"))
+	if err != nil {
+		t.Fatalf("Failed to read test spiffe bundle %v: %v", "spiffe_end2end/server_spiffebundle.json", err)
+	}
+	// Write the bundle that will fail to the tmp file path to be reloaded
+	err = os.WriteFile(spiffePath, wrongBundle, 0644)
+	if err != nil {
+		t.Fatalf("Failed to write test spiffe bundle %v: %v", "spiffe_end2end/server_spiffebundle.json", err)
+	}
+
+	for ; ctx.Err() == nil; <-time.After(10 * time.Millisecond) {
+		// Stop and restart the listener to force new handshakes
+		lis.Stop()
+		lis.Restart()
+		// Client handshake should eventually fail because the client CA was
+		// reloaded, and thus the server cert is signed by an unknown CA.
+		t.Log(server)
+		_, err = client.EmptyCall(ctx, &testpb.Empty{})
+		const wantErr = "no bundle found for peer certificates trust domain"
+		if status.Code(err) == codes.Unavailable && strings.Contains(err.Error(), wantErr) {
+			// Certs have reloaded.
+			server.Stop()
+			break
+		}
+		t.Logf("EmptyCall() got err: %s, want code: %s, want err: %s", err, codes.Unavailable, wantErr)
+	}
+	if ctx.Err() != nil {
+		t.Errorf("Timed out waiting for CA certs reloading")
+	}
+}
+
+func (s) TestMTLS(t *testing.T) {
+	s := stubserver.StartTestService(t, nil, grpc.Creds(testutils.CreateServerTLSCredentials(t, tls.RequireAndVerifyClientCert)))
+	defer s.Stop()
+
+	cfg := fmt.Sprintf(`{
+		"ca_certificate_file": "%s",
+		"certificate_file": "%s",
+		"private_key_file": "%s"
+	}`,
+		testdata.Path("x509/server_ca_cert.pem"),
+		testdata.Path("x509/client1_cert.pem"),
+		testdata.Path("x509/client1_key.pem"))
+	tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+	if err != nil {
+		t.Fatalf("Failed to create TLS bundle: %v", err)
+	}
+	defer stop()
+	conn, err := grpc.NewClient(s.Address, grpc.WithCredentialsBundle(tlsBundle), grpc.WithAuthority("x.test.example.com"))
+	if err != nil {
+		t.Fatalf("Error dialing: %v", err)
+	}
+	defer conn.Close()
+	client := testgrpc.NewTestServiceClient(conn)
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Errorf("EmptyCall(): got error %v when expected to succeed", err)
+	}
+}
+
+// Test_MTLS_SPIFFE configures a client and server. The server has a certificate
+// chain that is compatible with the client's configured SPIFFE bundle map. An
+// MTLS connection is attempted between the two and checked for success.
+func (s) Test_MTLS_SPIFFE(t *testing.T) {
+	testutils.SetEnvConfig(t, &envconfig.XDSSPIFFEEnabled, true)
+	tests := []struct {
+		name         string
+		serverOption grpc.ServerOption
+	}{
+		{
+			name:         "MTLS SPIFFE",
+			serverOption: grpc.Creds(testutils.CreateServerTLSCredentialsCompatibleWithSPIFFE(t, tls.RequireAndVerifyClientCert)),
+		},
+		{
+			name:         "MTLS SPIFFE Chain",
+			serverOption: grpc.Creds(testutils.CreateServerTLSCredentialsCompatibleWithSPIFFEChain(t, tls.RequireAndVerifyClientCert)),
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			s := stubserver.StartTestService(t, nil, tc.serverOption)
+			defer s.Stop()
+
+			cfg := fmt.Sprintf(`{
+	"certificate_file": "%s",
+	"private_key_file": "%s",
+	"spiffe_trust_bundle_map_file": "%s"
+}`,
+				testdata.Path("spiffe_end2end/client_spiffe.pem"),
+				testdata.Path("spiffe_end2end/client.key"),
+				testdata.Path("spiffe_end2end/client_spiffebundle.json"))
+			tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+			if err != nil {
+				t.Fatalf("Failed to create TLS bundle: %v", err)
+			}
+			defer stop()
+			conn, err := grpc.NewClient(s.Address, grpc.WithCredentialsBundle(tlsBundle), grpc.WithAuthority("x.test.example.com"))
+			if err != nil {
+				t.Fatalf("Error dialing: %v", err)
+			}
+			defer conn.Close()
+			client := testgrpc.NewTestServiceClient(conn)
+			ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+			defer cancel()
+			if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+				t.Errorf("EmptyCall(): got error %v when expected to succeed", err)
+			}
+		})
+	}
+}
+
+// Test_MTLS_SPIFFE_FlagDisabled configures a client and server. The server has
+// a certificate chain that is compatible with the client's configured SPIFFE
+// bundle map. However, the XDS flag that enabled SPIFFE usage is disabled. An
+// MTLS connection is attempted between the two and checked for failure.
+func (s) Test_MTLS_SPIFFE_FlagDisabled(t *testing.T) {
+	testutils.SetEnvConfig(t, &envconfig.XDSSPIFFEEnabled, false)
+	serverOption := grpc.Creds(testutils.CreateServerTLSCredentialsCompatibleWithSPIFFE(t, tls.RequireAndVerifyClientCert))
+	s := stubserver.StartTestService(t, nil, serverOption)
+	defer s.Stop()
+
+	cfg := fmt.Sprintf(`{
+"certificate_file": "%s",
+"private_key_file": "%s",
+"spiffe_trust_bundle_map_file": "%s"
+}`,
+		testdata.Path("spiffe_end2end/client_spiffe.pem"),
+		testdata.Path("spiffe_end2end/client.key"),
+		testdata.Path("spiffe_end2end/client_spiffebundle.json"))
+	tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+	if err != nil {
+		t.Fatalf("Failed to create TLS bundle: %v", err)
+	}
+	defer stop()
+	conn, err := grpc.NewClient(s.Address, grpc.WithCredentialsBundle(tlsBundle), grpc.WithAuthority("x.test.example.com"))
+	if err != nil {
+		t.Fatalf("Error dialing: %v", err)
+	}
+	defer conn.Close()
+	client := testgrpc.NewTestServiceClient(conn)
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err == nil {
+		t.Errorf("EmptyCall(): got success want failure")
+	}
+}
+
+func (s) Test_MTLS_SPIFFE_Failure(t *testing.T) {
+	testutils.SetEnvConfig(t, &envconfig.XDSSPIFFEEnabled, true)
+	tests := []struct {
+		name             string
+		certFile         string
+		keyFile          string
+		spiffeBundleFile string
+		serverOption     grpc.ServerOption
+		wantErrContains  string
+		wantErrCode      codes.Code
+	}{
+		{
+			name:             "No matching trust domain in bundle",
+			certFile:         "spiffe_end2end/client_spiffe.pem",
+			keyFile:          "spiffe_end2end/client.key",
+			spiffeBundleFile: "spiffe_end2end/server_spiffebundle.json",
+			serverOption:     grpc.Creds(testutils.CreateServerTLSCredentialsCompatibleWithSPIFFE(t, tls.RequireAndVerifyClientCert)),
+			wantErrContains:  "spiffe: no bundle found for peer certificates",
+			wantErrCode:      codes.Unavailable,
+		},
+		{
+			name:             "Server cert has no valid SPIFFE URIs",
+			certFile:         "spiffe_end2end/client_spiffe.pem",
+			keyFile:          "spiffe_end2end/client.key",
+			spiffeBundleFile: "spiffe_end2end/client_spiffebundle.json",
+			serverOption:     grpc.Creds(testutils.CreateServerTLSCredentials(t, tls.RequireAndVerifyClientCert)),
+			wantErrContains:  "spiffe: could not get spiffe ID from peer leaf cert",
+			wantErrCode:      codes.Unavailable,
+		},
+		{
+			name:             "Server cert has valid spiffe ID but doesn't chain to the root CA",
+			certFile:         "spiffe_end2end/client_spiffe.pem",
+			keyFile:          "spiffe_end2end/client.key",
+			spiffeBundleFile: "spiffe_end2end/client_spiffebundle.json",
+			serverOption:     grpc.Creds(testutils.CreateServerTLSCredentialsValidSPIFFEButWrongCA(t, tls.RequireAndVerifyClientCert)),
+			wantErrContains:  "spiffe: x509 certificate Verify failed: x509: certificate signed by unknown authority",
+			wantErrCode:      codes.Unavailable,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			s := stubserver.StartTestService(t, nil, tc.serverOption)
+			defer s.Stop()
+			cfg := fmt.Sprintf(`{
+"certificate_file": "%s",
+"private_key_file": "%s",
+"spiffe_trust_bundle_map_file": "%s"
+}`,
+				testdata.Path(tc.certFile),
+				testdata.Path(tc.keyFile),
+				testdata.Path(tc.spiffeBundleFile))
+			tlsBundle, stop, err := tlscreds.NewBundle([]byte(cfg))
+			if err != nil {
+				t.Fatalf("Failed to create TLS bundle: %v", err)
+			}
+			defer stop()
+			conn, err := grpc.NewClient(s.Address, grpc.WithCredentialsBundle(tlsBundle), grpc.WithAuthority("x.test.example.com"))
+			if err != nil {
+				t.Fatalf("grpc.NewClient(%q) failed: %v", s.Address, err)
+			}
+			defer conn.Close()
+			client := testgrpc.NewTestServiceClient(conn)
+			ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+			defer cancel()
+			if _, err = client.EmptyCall(ctx, &testpb.Empty{}); err == nil {
+				t.Errorf("EmptyCall(): got success. want failure")
+			}
+			if status.Code(err) != tc.wantErrCode {
+				t.Errorf("EmptyCall(): failed with wrong error. got code %v. want code: %v", status.Code(err), tc.wantErrCode)
+			}
+			if !strings.Contains(err.Error(), tc.wantErrContains) {
+				t.Errorf("EmptyCall(): failed with wrong error. got %v. want contains: %v", err, tc.wantErrContains)
+			}
+		})
+	}
+}

internal/xds/bootstrap/tlscreds/bundle_test.go

@@ -0,0 +1,162 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package tlscreds
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/tls/certprovider"
+	"google.golang.org/grpc/internal/credentials/spiffe"
+	"google.golang.org/grpc/internal/grpctest"
+	"google.golang.org/grpc/internal/stubserver"
+	"google.golang.org/grpc/internal/testutils"
+	"google.golang.org/grpc/testdata"
+
+	testgrpc "google.golang.org/grpc/interop/grpc_testing"
+	testpb "google.golang.org/grpc/interop/grpc_testing"
+)
+
+const defaultTestTimeout = 5 * time.Second
+
+type s struct {
+	grpctest.Tester
+}
+
+func Test(t *testing.T) {
+	grpctest.RunSubTests(t, s{})
+}
+
+type failingProvider struct{}
+
+func (f failingProvider) KeyMaterial(context.Context) (*certprovider.KeyMaterial, error) {
+	return nil, errors.New("test error")
+}
+
+func (f failingProvider) Close() {}
+
+func (s) TestFailingProvider(t *testing.T) {
+	s := stubserver.StartTestService(t, nil, grpc.Creds(testutils.CreateServerTLSCredentials(t, tls.RequireAndVerifyClientCert)))
+	defer s.Stop()
+
+	cfg := fmt.Sprintf(`{
+               "ca_certificate_file": "%s",
+               "certificate_file": "%s",
+               "private_key_file": "%s",
+			   "spiffe_trust_bundle_map_file": "%s"
+       }`,
+		testdata.Path("x509/server_ca_cert.pem"),
+		testdata.Path("x509/client1_cert.pem"),
+		testdata.Path("x509/client1_key.pem"),
+		testdata.Path("spiffe_end2end/client_spiffebundle.json"))
+	tlsBundle, stop, err := NewBundle([]byte(cfg))
+	if err != nil {
+		t.Fatalf("Failed to create TLS bundle: %v", err)
+	}
+	stop()
+
+	// Force a provider that returns an error, and make sure the client fails
+	// the handshake.
+	creds, ok := tlsBundle.TransportCredentials().(*reloadingCreds)
+	if !ok {
+		t.Fatalf("Got %T, expected reloadingCreds", tlsBundle.TransportCredentials())
+	}
+	creds.provider = &failingProvider{}
+
+	conn, err := grpc.NewClient(s.Address, grpc.WithCredentialsBundle(tlsBundle), grpc.WithAuthority("x.test.example.com"))
+	if err != nil {
+		t.Fatalf("Error dialing: %v", err)
+	}
+	defer conn.Close()
+
+	client := testgrpc.NewTestServiceClient(conn)
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	_, err = client.EmptyCall(ctx, &testpb.Empty{})
+	if wantErr := "test error"; err == nil || !strings.Contains(err.Error(), wantErr) {
+		t.Errorf("EmptyCall() got err: %s, want err to contain: %s", err, wantErr)
+	}
+}
+
+func rawCertsFromFile(t *testing.T, filePath string) [][]byte {
+	t.Helper()
+	rawCert, err := os.ReadFile(testdata.Path(filePath))
+	if err != nil {
+		t.Fatalf("Reading certificate file failed: %v", err)
+	}
+	block, _ := pem.Decode(rawCert)
+	if block == nil || block.Type != "CERTIFICATE" {
+		t.Fatalf("pem.Decode() failed to decode certificate in file %q", "spiffe/server1_spiffe.pem")
+	}
+	return [][]byte{block.Bytes}
+}
+
+func (s) TestSPIFFEVerifyFuncMismatchedCert(t *testing.T) {
+	spiffeBundleBytes, err := os.ReadFile(testdata.Path("spiffe_end2end/client_spiffebundle.json"))
+	if err != nil {
+		t.Fatalf("Reading spiffebundle file failed: %v", err)
+	}
+	spiffeBundle, err := spiffe.BundleMapFromBytes(spiffeBundleBytes)
+	if err != nil {
+		t.Fatalf("spiffe.BundleMapFromBytes() failed: %v", err)
+	}
+	verifyFunc := buildSPIFFEVerifyFunc(spiffeBundle)
+	verifiedChains := [][]*x509.Certificate{}
+	tests := []struct {
+		name            string
+		rawCerts        [][]byte
+		wantErrContains string
+	}{
+		{
+			name:            "mismathed cert",
+			rawCerts:        rawCertsFromFile(t, "spiffe/server1_spiffe.pem"),
+			wantErrContains: "spiffe: x509 certificate Verify failed",
+		},
+		{
+			name:            "bad input cert",
+			rawCerts:        [][]byte{[]byte("NOT_GOOD_DATA")},
+			wantErrContains: "spiffe: verify function could not parse input certificate",
+		},
+		{
+			name:            "no input bytes",
+			rawCerts:        nil,
+			wantErrContains: "no valid input certificates",
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			err = verifyFunc(tc.rawCerts, verifiedChains)
+			if err == nil {
+				t.Fatalf("buildSPIFFEVerifyFunc call succeeded. want failure")
+			}
+			if !strings.Contains(err.Error(), tc.wantErrContains) {
+				t.Fatalf("buildSPIFFEVerifyFunc got err %v want err to contain %v", err, tc.wantErrContains)
+			}
+		})
+	}
+}