[alts] Add plumbing for the bound access token field in the ALTS StartClient request. (#8284)

credentials/alts/alts.go

@@ -133,10 +133,11 @@ func DefaultServerOptions() *ServerOptions {
 // altsTC is the credentials required for authenticating a connection using ALTS.
 // It implements credentials.TransportCredentials interface.
 type altsTC struct {
-	info      *credentials.ProtocolInfo
-	side      core.Side
-	accounts  []string
-	hsAddress string
+	info             *credentials.ProtocolInfo
+	side             core.Side
+	accounts         []string
+	hsAddress        string
+	boundAccessToken string
 }
 
 // NewClientCreds constructs a client-side ALTS TransportCredentials object.
@@ -198,6 +199,7 @@ func (g *altsTC) ClientHandshake(ctx context.Context, addr string, rawConn net.C
 		MaxRpcVersion: maxRPCVersion,
 		MinRpcVersion: minRPCVersion,
 	}
+	opts.BoundAccessToken = g.boundAccessToken
 	chs, err := handshaker.NewClientHandshaker(ctx, hsConn, rawConn, opts)
 	if err != nil {
 		return nil, nil, err

credentials/alts/alts_test.go

@@ -336,6 +336,28 @@ func (s) TestFullHandshake(t *testing.T) {
 	}
 }
 
+// TestHandshakeWithAccessToken performs an ALTS handshake between a test client and
+// server, where both client and server offload to a local, fake handshaker
+// service, and expects the StartClient request to include a bound access token.
+func (s) TestHandshakeWithAccessToken(t *testing.T) {
+	// Start the fake handshaker service and the server.
+	var wait sync.WaitGroup
+	defer wait.Wait()
+	boundAccessToken := "fake-bound-access-token"
+	stopHandshaker, handshakerAddress := startFakeHandshakerServiceWithExpectedBoundAccessToken(t, &wait, boundAccessToken)
+	defer stopHandshaker()
+	stopServer, serverAddress := startServer(t, handshakerAddress)
+	defer stopServer()
+
+	// Ping the server, authenticating with ALTS and a bound access token.
+	establishAltsConnectionWithBoundAccessToken(t, handshakerAddress, serverAddress, boundAccessToken)
+
+	// Close open connections to the fake handshaker service.
+	if err := service.CloseForTesting(); err != nil {
+		t.Errorf("service.CloseForTesting() failed: %v", err)
+	}
+}
+
 // TestConcurrentHandshakes performs a several, concurrent ALTS handshakes
 // between a test client and server, where both client and server offload to a
 // local, fake handshaker service.
@@ -385,7 +407,15 @@ func versions(minMajor, minMinor, maxMajor, maxMinor uint32) *altspb.RpcProtocol
 }
 
 func establishAltsConnection(t *testing.T, handshakerAddress, serverAddress string) {
+	establishAltsConnectionWithBoundAccessToken(t, handshakerAddress, serverAddress, "")
+}
+
+func establishAltsConnectionWithBoundAccessToken(t *testing.T, handshakerAddress, serverAddress, boundAccessToken string) {
 	clientCreds := NewClientCreds(&ClientOptions{HandshakerServiceAddress: handshakerAddress})
+	if boundAccessToken != "" {
+		altsCreds := clientCreds.(*altsTC)
+		altsCreds.boundAccessToken = boundAccessToken
+	}
 	conn, err := grpc.NewClient(serverAddress, grpc.WithTransportCredentials(clientCreds))
 	if err != nil {
 		t.Fatalf("grpc.NewClient(%v) failed: %v", serverAddress, err)
@@ -429,12 +459,20 @@ func establishAltsConnection(t *testing.T, handshakerAddress, serverAddress stri
 }
 
 func startFakeHandshakerService(t *testing.T, wait *sync.WaitGroup) (stop func(), address string) {
+	return startFakeHandshakerServiceWithExpectedBoundAccessToken(t, wait, "")
+}
+
+func startFakeHandshakerServiceWithExpectedBoundAccessToken(t *testing.T, wait *sync.WaitGroup, boundAccessToken string) (stop func(), address string) {
 	listener, err := testutils.LocalTCPListener()
 	if err != nil {
 		t.Fatalf("LocalTCPListener() failed: %v", err)
 	}
 	s := grpc.NewServer()
-	altsgrpc.RegisterHandshakerServiceServer(s, &testutil.FakeHandshaker{})
+	hs := &testutil.FakeHandshaker{}
+	if boundAccessToken != "" {
+		hs.ExpectedBoundAccessToken = boundAccessToken
+	}
+	altsgrpc.RegisterHandshakerServiceServer(s, hs)
 	wait.Add(1)
 	go func() {
 		defer wait.Done()

credentials/alts/internal/handshaker/handshaker.go

@@ -88,6 +88,8 @@ type ClientHandshakerOptions struct {
 	TargetServiceAccounts []string
 	// RPCVersions specifies the gRPC versions accepted by the client.
 	RPCVersions *altspb.RpcProtocolVersions
+	// BoundAccessToken is a bound access token to be sent to the server for authentication.
+	BoundAccessToken string
 }
 
 // ServerHandshakerOptions contains the server handshaker options that can
@@ -195,7 +197,9 @@ func (h *altsHandshaker) ClientHandshake(ctx context.Context) (net.Conn, credent
 			},
 		},
 	}
-
+	if h.clientOpts.BoundAccessToken != "" {
+		req.GetClientStart().AccessToken = h.clientOpts.BoundAccessToken
+	}
 	conn, result, err := h.doHandshake(req)
 	if err != nil {
 		return nil, nil, err

credentials/alts/internal/testutil/testutil.go

@@ -145,6 +145,8 @@ func MakeFrame(pl string) []byte {
 // FakeHandshaker is a fake implementation of the ALTS handshaker service.
 type FakeHandshaker struct {
 	altsgrpc.HandshakerServiceServer
+	// ExpectedBoundAccessToken is the expected bound access token in the ClientStart request.
+	ExpectedBoundAccessToken string
 }
 
 // DoHandshake performs a fake ALTS handshake.
@@ -221,6 +223,9 @@ func (h *FakeHandshaker) processStartClient(req *altspb.StartClientHandshakeReq)
 	if len(req.RecordProtocols) != 1 || req.RecordProtocols[0] != "ALTSRP_GCM_AES128_REKEY" {
 		return nil, fmt.Errorf("unexpected record protocols: %v", req.RecordProtocols)
 	}
+	if h.ExpectedBoundAccessToken != req.GetAccessToken() {
+		return nil, fmt.Errorf("unexpected access token: %v", req.GetAccessToken())
+	}
 	return &altspb.HandshakerResp{
 		OutFrames:     []byte("ClientInit"),
 		BytesConsumed: 0,