automtls: fix bidirectional communication when AutoMTLS is enabled

client.go

@@ -574,6 +574,8 @@ func (c *Client) Start() (addr net.Addr, err error) {
 
 		c.config.TLSConfig = &tls.Config{
 			Certificates: []tls.Certificate{cert},
+			ClientAuth:   tls.RequireAndVerifyClientCert,
+			MinVersion:   tls.VersionTLS12,
 			ServerName:   "localhost",
 		}
 	}
@@ -774,7 +776,7 @@ func (c *Client) Start() (addr net.Addr, err error) {
 }
 
 // loadServerCert is used by AutoMTLS to read an x.509 cert returned by the
-// server, and load it as the RootCA for the client TLSConfig.
+// server, and load it as the RootCA and ClientCA for the client TLSConfig.
 func (c *Client) loadServerCert(cert string) error {
 	certPool := x509.NewCertPool()
 
@@ -791,6 +793,7 @@ func (c *Client) loadServerCert(cert string) error {
 	certPool.AddCert(x509Cert)
 
 	c.config.TLSConfig.RootCAs = certPool
+	c.config.TLSConfig.ClientCAs = certPool
 	return nil
 }
 

server.go

@@ -319,6 +319,8 @@ func Serve(opts *ServeConfig) {
 			ClientAuth:   tls.RequireAndVerifyClientCert,
 			ClientCAs:    clientCertPool,
 			MinVersion:   tls.VersionTLS12,
+			RootCAs:      clientCertPool,
+			ServerName:   "localhost",
 		}
 
 		// We send back the raw leaf cert data for the client rather than the

server_test.go

@@ -82,6 +82,75 @@ func TestServer_testMode(t *testing.T) {
 	t.Logf("HELLO")
 }
 
+func TestServer_testMode_AutoMTLS(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	closeCh := make(chan struct{})
+	go Serve(&ServeConfig{
+		HandshakeConfig: testVersionedHandshake,
+		VersionedPlugins: map[int]PluginSet{
+			2: testGRPCPluginMap,
+		},
+		GRPCServer: DefaultGRPCServer,
+		Logger:     hclog.NewNullLogger(),
+		Test: &ServeTestConfig{
+			Context:          ctx,
+			ReattachConfigCh: nil,
+			CloseCh:          closeCh,
+		},
+	})
+
+	// Connect!
+	process := helperProcess("test-mtls")
+	c := NewClient(&ClientConfig{
+		Cmd:             process,
+		HandshakeConfig: testVersionedHandshake,
+		VersionedPlugins: map[int]PluginSet{
+			2: testGRPCPluginMap,
+		},
+		AllowedProtocols: []Protocol{ProtocolGRPC},
+		AutoMTLS:         true,
+	})
+	client, err := c.Client()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Grab the impl
+	raw, err := client.Dispense("test")
+	if err != nil {
+		t.Fatalf("err should be nil, got %s", err)
+	}
+
+	tester, ok := raw.(testInterface)
+	if !ok {
+		t.Fatalf("bad: %#v", raw)
+	}
+
+	n := tester.Double(3)
+	if n != 6 {
+		t.Fatal("invalid response", n)
+	}
+
+	// ensure we can make use of bidirectional communication with AutoMTLS
+	// enabled
+	err = tester.Bidirectional()
+	if err != nil {
+		t.Fatal("invalid response", err)
+	}
+
+	// Pinging should work
+	if err := client.Ping(); err != nil {
+		t.Fatalf("should not err: %s", err)
+	}
+
+	c.Kill()
+	// Canceling should cause an exit
+	cancel()
+	<-closeCh
+}
+
 func TestRmListener_impl(t *testing.T) {
 	var _ net.Listener = new(rmListener)
 }
@@ -145,7 +214,6 @@ func TestProtocolSelection_no_server(t *testing.T) {
 	if protocol != ProtocolNetRPC {
 		t.Fatalf("bad protocol %s", protocol)
 	}
-
 }
 
 func TestServer_testStdLogger(t *testing.T) {