Prevent connections to local addresses

Author: Lenni0451

src/main/java/net/lenni0451/miniconnect/server/LobbyServerHandler.java

@@ -14,6 +14,7 @@
 import net.raphimc.netminecraft.packet.Packet;
 import org.apache.commons.lang3.tuple.Pair;
 
+import java.nio.channels.ClosedChannelException;
 import java.util.concurrent.TimeUnit;
 
 public class LobbyServerHandler extends SimpleChannelInboundHandler<Packet> {
@@ -70,7 +71,8 @@ protected void channelRead0(ChannelHandlerContext ctx, Packet packet) {
     }
 
     @Override
-    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+        if (cause instanceof ClosedChannelException) return;
         cause.printStackTrace();
         ctx.close();
     }

src/main/java/net/lenni0451/miniconnect/server/states/play/screen/impl/MainScreen.java

@@ -17,11 +17,13 @@
 import net.lenni0451.miniconnect.server.states.play.screen.Screen;
 import net.lenni0451.miniconnect.server.states.play.screen.ScreenHandler;
 import net.lenni0451.miniconnect.utils.ChannelUtils;
+import net.lenni0451.miniconnect.utils.InetUtils;
 import net.raphimc.minecraftauth.MinecraftAuth;
 import net.raphimc.minecraftauth.step.msa.StepMsaDeviceCode;
 import net.raphimc.netminecraft.packet.impl.play.S2CPlayDisconnectPacket;
 import net.raphimc.viaproxy.saves.impl.accounts.MicrosoftAccount;
 
+import java.net.InetAddress;
 import java.util.concurrent.TimeoutException;
 
 import static net.lenni0451.miniconnect.server.states.play.screen.ItemBuilder.item;
@@ -52,7 +54,8 @@ public void init(ScreenHandler screenHandler, ItemList itemList) {
             playerConfig.chatListener = s -> {
                 try {
                     HostAndPort hostAndPort = HostAndPort.fromString(s);
-                    if (hostAndPort.getHost().isBlank()) throw new IllegalStateException();
+                    if (hostAndPort.getHost().isBlank()) throw new IllegalArgumentException();
+                    if (InetUtils.isLocal(InetAddress.getByName(hostAndPort.getHost()))) throw new IllegalArgumentException();
                     playerConfig.serverAddress = hostAndPort.getHost();
                     playerConfig.serverPort = hostAndPort.getPortOrDefault(-1);
                 } catch (Throwable t) {

src/main/java/net/lenni0451/miniconnect/utils/InetUtils.java

@@ -0,0 +1,22 @@
+package net.lenni0451.miniconnect.utils;
+
+import java.net.InetAddress;
+
+public class InetUtils {
+
+    public static boolean isLocal(final InetAddress address) {
+        if (address.isAnyLocalAddress() || address.isLoopbackAddress()) return true;
+        byte[] addressBytes = address.getAddress();
+
+        if (addressBytes.length == 4) { // Check for IPv4 local address ranges
+            if (addressBytes[0] == 10) return true; // 10.0.0.0/8
+            if (addressBytes[0] == (byte) 172 && addressBytes[1] >= 16 && addressBytes[1] <= 31) return true; // 172.16.0.0/12
+            if (addressBytes[0] == (byte) 192 && addressBytes[1] == (byte) 168) return true; // 192.168.0.0/16
+        }
+        if (addressBytes.length == 16) { // Check for IPv6 local address ranges
+            return (addressBytes[0] == (byte) 0xfe && (addressBytes[1] & (byte) 0xc0) == (byte) 0x80); // fe80::/10
+        }
+        return false;
+    }
+
+}