Fix modded entities

src/main/java/me/libraryaddict/disguise/utilities/packets/packetlisteners/PacketListenerModdedClient.java

@@ -0,0 +1,161 @@
+package me.libraryaddict.disguise.utilities.packets.packetlisteners;
+
+import com.comphenix.protocol.PacketType;
+import com.comphenix.protocol.ProtocolLibrary;
+import com.comphenix.protocol.events.PacketAdapter;
+import com.comphenix.protocol.events.PacketContainer;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.wrappers.MinecraftKey;
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import com.mojang.authlib.GameProfile;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import io.netty.handler.codec.DecoderException;
+import me.libraryaddict.disguise.LibsDisguises;
+import me.libraryaddict.disguise.utilities.modded.ModdedManager;
+import net.minecraft.server.v1_15_R1.PacketDataSerializer;
+import org.bukkit.entity.Player;
+
+import java.lang.reflect.InvocationTargetException;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Created by libraryaddict on 11/06/2020.
+ */
+public class PacketListenerModdedClient extends PacketAdapter {
+    private final Cache<String, String> loginAttempts = CacheBuilder.newBuilder().expireAfterWrite(15, TimeUnit.SECONDS)
+            .build();
+    private final int packetId1 = 5555554, packetId2 = 5555555;
+
+    public PacketListenerModdedClient() {
+        super(LibsDisguises.getInstance(), PacketType.Login.Client.START, PacketType.Login.Client.CUSTOM_PAYLOAD);
+    }
+
+    private int getInt(ByteBuf buf) {
+        int i = 0;
+        int j = 0;
+
+        byte b0;
+        do {
+            b0 = buf.readByte();
+            i |= (b0 & 127) << j++ * 7;
+            if (j > 5) {
+                throw new RuntimeException("VarInt too big");
+            }
+        } while ((b0 & 128) == 128);
+
+        return i;
+    }
+
+    private void handleModlist(Player player, String name, byte[] data) {
+        ByteBuf buf = Unpooled.copiedBuffer(data);
+
+        int packetId = getInt(buf);
+
+        if (packetId != 2) {
+            return;
+        }
+
+        int count = getInt(buf);
+        ArrayList<String> mods = new ArrayList<>();
+
+        for (int i = 0; i < count; i++) {
+            mods.add(getString(buf));
+        }
+
+        ModdedManager.getForgeMods().put(name, mods);
+    }
+
+    public String getString(ByteBuf buf) {
+        int j = getInt(buf);
+        int size = 256;
+
+        if (j > size * 4) {
+            throw new DecoderException(
+                    "The received encoded string buffer length is longer than maximum allowed (" + j + " > " +
+                            size * 4 + ")");
+        } else if (j < 0) {
+            throw new DecoderException("The received encoded string buffer length is less than zero! Weird string!");
+        } else {
+            String s = buf.toString(buf.readerIndex(), j, StandardCharsets.UTF_8);
+            buf.readerIndex(buf.readerIndex() + j);
+            if (s.length() > size) {
+                throw new DecoderException(
+                        "The received string length is longer than maximum allowed (" + j + " > " + size + ")");
+            } else {
+                return s;
+            }
+        }
+    }
+
+    private void handleDataReceived(Player player, String name) {
+        // Continue
+        PacketContainer packet = new PacketContainer(PacketType.Login.Client.START);
+        packet.getModifier().write(0, new GameProfile(null, name));
+
+        try {
+            ProtocolLibrary.getProtocolManager().recieveClientPacket(player, packet, false);
+        }
+        catch (IllegalAccessException | InvocationTargetException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Override
+    public void onPacketReceiving(PacketEvent event) {
+        event.setCancelled(true);
+
+        if (event.getPacketType() != PacketType.Login.Client.START) {
+            String address = event.getPlayer().getAddress().toString();
+
+            String name = loginAttempts.getIfPresent(address);
+
+            if (name == null) {
+                return;
+            }
+
+            if (event.getPacket().getIntegers().read(0) == packetId2) {
+                loginAttempts.invalidate(address);
+                handleDataReceived(event.getPlayer(), name);
+                return;
+            } else if (event.getPacket().getIntegers().read(0) == packetId1) {
+                ByteBuf buf = (ByteBuf) event.getPacket().getModifier().read(1);
+
+                if (buf != null) {
+                    byte[] bytes = new byte[buf.readableBytes()];
+                    buf.readBytes(bytes);
+
+                    handleModlist(event.getPlayer(), name, bytes);
+                }
+            }
+
+            return;
+        }
+
+        loginAttempts
+                .put(event.getPlayer().getAddress().toString(), event.getPacket().getGameProfiles().read(0).getName());
+
+        PacketContainer packet1 = new PacketContainer(PacketType.Login.Server.CUSTOM_PAYLOAD);
+        packet1.getIntegers().write(0, packetId1);
+        packet1.getMinecraftKeys().write(0, new com.comphenix.protocol.wrappers.MinecraftKey("fml", "handshake"));
+        packet1.getModifier()
+                .write(2, new PacketDataSerializer(Unpooled.wrappedBuffer(ModdedManager.getFmlHandshake())));
+
+        PacketContainer packet2 = new PacketContainer(PacketType.Login.Server.CUSTOM_PAYLOAD);
+        packet2.getIntegers().write(0, packetId2);
+        packet2.getMinecraftKeys().write(0, new MinecraftKey("fml", "handshake"));
+        packet2.getModifier()
+                .write(2, new PacketDataSerializer(Unpooled.wrappedBuffer(ModdedManager.getFmlRegistries())));
+
+        try {
+            ProtocolLibrary.getProtocolManager().sendServerPacket(event.getPlayer(), packet1);
+            ProtocolLibrary.getProtocolManager().sendServerPacket(event.getPlayer(), packet2);
+        }
+        catch (InvocationTargetException e) {
+            e.printStackTrace();
+        }
+    }
+}