Modbus/TCP Security (#97)

Adds support for Modbus/TCP Security (Modbus over TLS).

See https://modbus.org/docs/MB-TCP-Security-v21_2018-07-24.pdf

modbus-serial/src/main/java/com/digitalpetri/modbus/serial/server/SerialPortServerTransport.java

@@ -8,6 +8,7 @@
 import com.digitalpetri.modbus.internal.util.ExecutionQueue;
 import com.digitalpetri.modbus.serial.SerialPortTransportConfig;
 import com.digitalpetri.modbus.serial.SerialPortTransportConfig.Builder;
+import com.digitalpetri.modbus.server.ModbusRequestContext.ModbusRtuRequestContext;
 import com.digitalpetri.modbus.server.ModbusRtuServerTransport;
 import com.fazecast.jSerialComm.SerialPort;
 import com.fazecast.jSerialComm.SerialPortDataListener;

modbus-tcp/src/main/java/com/digitalpetri/modbus/tcp/client/NettyClientTransportConfig.java

@@ -6,8 +6,11 @@
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.EventLoopGroup;
 import java.time.Duration;
+import java.util.Optional;
 import java.util.concurrent.ExecutorService;
 import java.util.function.Consumer;
+import javax.net.ssl.KeyManagerFactory;
+import javax.net.ssl.TrustManagerFactory;
 
 /**
  * Configuration for a {@link NettyTcpClientTransport}.
@@ -23,6 +26,9 @@
  *     {@link Bootstrap}.
  * @param pipelineCustomizer a {@link Consumer} that can be used to customize the Netty
  *     {@link ChannelPipeline}.
+ * @param tlsEnabled whether to enable TLS (Modbus/TCP Security).
+ * @param keyManagerFactory the {@link KeyManagerFactory} to use if TLS is enabled.
+ * @param trustManagerFactory the {@link TrustManagerFactory} to use if TLS is enabled.
  */
 public record NettyClientTransportConfig(
     String hostname,
@@ -33,9 +39,12 @@ public record NettyClientTransportConfig(
     EventLoopGroup eventLoopGroup,
     ExecutorService executor,
     Consumer<Bootstrap> bootstrapCustomizer,
-    Consumer<ChannelPipeline> pipelineCustomizer
+    Consumer<ChannelPipeline> pipelineCustomizer,
+    boolean tlsEnabled,
+    Optional<KeyManagerFactory> keyManagerFactory,
+    Optional<TrustManagerFactory> trustManagerFactory
 ) {
-
+  
   /**
    * Create a new {@link NettyClientTransportConfig} with a callback that allows customizing the
    * configuration.
@@ -59,7 +68,7 @@ public static class Builder {
     /**
      * The port to connect to.
      */
-    public int port = 502;
+    public int port = -1;
 
     /**
      * The connect timeout.
@@ -100,16 +109,42 @@ public static class Builder {
      */
     public Consumer<ChannelPipeline> pipelineCustomizer = p -> {};
 
+    /**
+     * Whether to enable TLS (Modbus/TCP Security).
+     */
+    public boolean tlsEnabled = false;
+
+    /**
+     * The {@link KeyManagerFactory} to use if TLS is enabled.
+     */
+    public KeyManagerFactory keyManagerFactory = null;
+
+    /**
+     * The {@link TrustManagerFactory} to use if TLS is enabled.
+     */
+    public TrustManagerFactory trustManagerFactory = null;
+
     public NettyClientTransportConfig build() {
       if (hostname == null) {
         throw new NullPointerException("hostname must not be null");
       }
+      if (port == -1) {
+        port = tlsEnabled ? 802 : 502;
+      }
       if (eventLoopGroup == null) {
         eventLoopGroup = Netty.sharedEventLoop();
       }
       if (executor == null) {
         executor = Modbus.sharedExecutor();
       }
+      if (tlsEnabled) {
+        if (keyManagerFactory == null) {
+          throw new NullPointerException("keyManagerFactory must not be null");
+        }
+        if (trustManagerFactory == null) {
+          throw new NullPointerException("trustManagerFactory must not be null");
+        }
+      }
 
       return new NettyClientTransportConfig(
           hostname,
@@ -120,7 +155,10 @@ public NettyClientTransportConfig build() {
           eventLoopGroup,
           executor,
           bootstrapCustomizer,
-          pipelineCustomizer
+          pipelineCustomizer,
+          tlsEnabled,
+          Optional.ofNullable(keyManagerFactory),
+          Optional.ofNullable(trustManagerFactory)
       );
     }
 

modbus-tcp/src/main/java/com/digitalpetri/modbus/tcp/client/NettyRtuClientTransport.java

@@ -25,6 +25,10 @@
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
+import io.netty.handler.ssl.ClientAuth;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import io.netty.handler.ssl.SslProtocols;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 import java.util.concurrent.atomic.AtomicReference;
@@ -158,7 +162,20 @@ public CompletableFuture<Channel> connect(FsmContext<State, Event> fsmContext) {
           .option(ChannelOption.TCP_NODELAY, Boolean.TRUE)
           .handler(new ChannelInitializer<SocketChannel>() {
             @Override
-            protected void initChannel(SocketChannel channel) {
+            protected void initChannel(SocketChannel channel) throws Exception {
+              if (config.tlsEnabled()) {
+                SslContext sslContext = SslContextBuilder.forClient()
+                    .clientAuth(ClientAuth.REQUIRE)
+                    .keyManager(config.keyManagerFactory().orElseThrow())
+                    .trustManager(config.trustManagerFactory().orElseThrow())
+                    .protocols(SslProtocols.TLS_v1_2, SslProtocols.TLS_v1_3)
+                    .build();
+
+                channel.pipeline().addLast(
+                    sslContext.newHandler(channel.alloc(), config.hostname(), config.port())
+                );
+              }
+
               channel.pipeline().addLast(new ModbusRtuClientFrameReceiver());
 
               config.pipelineCustomizer().accept(channel.pipeline());

modbus-tcp/src/main/java/com/digitalpetri/modbus/tcp/client/NettyTcpClientTransport.java

@@ -21,6 +21,11 @@
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
+import io.netty.handler.ssl.ClientAuth;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import io.netty.handler.ssl.SslHandler;
+import io.netty.handler.ssl.SslProtocols;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
@@ -163,6 +168,13 @@ protected void channelRead0(ChannelHandlerContext ctx, ModbusTcpFrame frame) {
         executionQueue.submit(() -> frameReceiver.accept(frame));
       }
     }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+      logger.error("Exception caught", cause);
+      ctx.close();
+    }
+
   }
 
   private class ModbusTcpChannelActions implements ChannelActions {
@@ -174,15 +186,7 @@ public CompletableFuture<Channel> connect(FsmContext<State, Event> fsmContext) {
           .group(config.eventLoopGroup())
           .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, (int) config.connectTimeout().toMillis())
           .option(ChannelOption.TCP_NODELAY, Boolean.TRUE)
-          .handler(new ChannelInitializer<SocketChannel>() {
-            @Override
-            protected void initChannel(SocketChannel channel) {
-              channel.pipeline().addLast(new ModbusTcpCodec());
-              channel.pipeline().addLast(new ModbusTcpFrameHandler());
-
-              config.pipelineCustomizer().accept(channel.pipeline());
-            }
-          });
+          .handler(newChannelInitializer());
 
       config.bootstrapCustomizer().accept(bootstrap);
 
@@ -191,7 +195,21 @@ protected void initChannel(SocketChannel channel) {
       bootstrap.connect(config.hostname(), config.port()).addListener(
           (ChannelFutureListener) channelFuture -> {
             if (channelFuture.isSuccess()) {
-              future.complete(channelFuture.channel());
+              Channel channel = channelFuture.channel();
+
+              if (config.tlsEnabled()) {
+                channel.pipeline().get(SslHandler.class).handshakeFuture().addListener(
+                    handshakeFuture -> {
+                      if (handshakeFuture.isSuccess()) {
+                        future.complete(channel);
+                      } else {
+                        future.completeExceptionally(handshakeFuture.cause());
+                      }
+                    }
+                );
+              } else {
+                future.complete(channel);
+              }
             } else {
               future.completeExceptionally(channelFuture.cause());
             }
@@ -201,6 +219,31 @@ protected void initChannel(SocketChannel channel) {
       return future;
     }
 
+    private ChannelInitializer<SocketChannel> newChannelInitializer() {
+      return new ChannelInitializer<>() {
+        @Override
+        protected void initChannel(SocketChannel channel) throws Exception {
+          if (config.tlsEnabled()) {
+            SslContext sslContext = SslContextBuilder.forClient()
+                .clientAuth(ClientAuth.REQUIRE)
+                .keyManager(config.keyManagerFactory().orElseThrow())
+                .trustManager(config.trustManagerFactory().orElseThrow())
+                .protocols(SslProtocols.TLS_v1_2, SslProtocols.TLS_v1_3)
+                .build();
+
+            channel.pipeline().addLast(
+                sslContext.newHandler(channel.alloc(), config.hostname(), config.port())
+            );
+          }
+
+          channel.pipeline().addLast(new ModbusTcpCodec());
+          channel.pipeline().addLast(new ModbusTcpFrameHandler());
+
+          config.pipelineCustomizer().accept(channel.pipeline());
+        }
+      };
+    }
+
     @Override
     public CompletableFuture<Void> disconnect(
         FsmContext<State, Event> fsmContext, Channel channel) {

modbus-tcp/src/main/java/com/digitalpetri/modbus/tcp/security/SecurityUtil.java

@@ -0,0 +1,97 @@
+package com.digitalpetri.modbus.tcp.security;
+
+import java.io.IOException;
+import java.security.GeneralSecurityException;
+import java.security.KeyStore;
+import java.security.PrivateKey;
+import java.security.cert.X509Certificate;
+import javax.net.ssl.KeyManagerFactory;
+import javax.net.ssl.TrustManagerFactory;
+
+public class SecurityUtil {
+
+  /**
+   * Create a {@link KeyManagerFactory} from a private key and certificates.
+   *
+   * @param privateKey the private key.
+   * @param certificates the certificates.
+   * @return a {@link KeyManagerFactory}.
+   * @throws GeneralSecurityException if an error occurs.
+   * @throws IOException if an error occurs.
+   */
+  public static KeyManagerFactory createKeyManagerFactory(
+      PrivateKey privateKey,
+      X509Certificate... certificates
+  ) throws GeneralSecurityException, IOException {
+
+    KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
+    keyStore.load(null, null);
+
+    keyStore.setKeyEntry("key", privateKey, new char[0], certificates);
+
+    return createKeyManagerFactory(keyStore, new char[0]);
+  }
+
+  /**
+   * Create a {@link KeyManagerFactory} from a {@link KeyStore}.
+   *
+   * @param keyStore the {@link KeyStore}.
+   * @param keyStorePassword the password for the {@link KeyStore}.
+   * @return a {@link KeyManagerFactory}.
+   * @throws GeneralSecurityException if an error occurs.
+   */
+  public static KeyManagerFactory createKeyManagerFactory(
+      KeyStore keyStore,
+      char[] keyStorePassword
+  ) throws GeneralSecurityException {
+
+    KeyManagerFactory keyManagerFactory =
+        KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
+
+    keyManagerFactory.init(keyStore, keyStorePassword);
+
+    return keyManagerFactory;
+  }
+
+  /**
+   * Create a {@link TrustManagerFactory} from certificates.
+   *
+   * @param certificates the certificates.
+   * @return a {@link TrustManagerFactory}.
+   * @throws GeneralSecurityException if an error occurs.
+   * @throws IOException if an error occurs.
+   */
+  public static TrustManagerFactory createTrustManagerFactory(
+      X509Certificate... certificates
+  ) throws GeneralSecurityException, IOException {
+
+    KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
+    keyStore.load(null, null);
+
+    for (int i = 0; i < certificates.length; i++) {
+      keyStore.setCertificateEntry("cert" + i, certificates[i]);
+    }
+
+    return createTrustManagerFactory(keyStore);
+  }
+
+  /**
+   * Create a {@link TrustManagerFactory} from a {@link KeyStore}.
+   *
+   * @param keyStore the {@link KeyStore}.
+   * @return a {@link TrustManagerFactory}.
+   * @throws GeneralSecurityException if an error occurs.
+   */
+  public static TrustManagerFactory createTrustManagerFactory(
+      KeyStore keyStore
+  ) throws GeneralSecurityException {
+
+    TrustManagerFactory trustManagerFactory =
+        TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
+
+    trustManagerFactory.init(keyStore);
+
+    return trustManagerFactory;
+  }
+
+}