TCPShield Fabric support (#40)

Adds Fabric support (huge, huge thanks to @Draylar)

README.md

@@ -6,7 +6,7 @@ It also parses passed IP addresses so the server is aware of the real player IP
 
 ### Compatibility
 
-TCPShield is compatible with Spigot / CraftBukkit, BungeeCord and Velocity.
+TCPShield is compatible with Spigot / CraftBukkit, BungeeCord, Velocity and Fabric.
 
 When using Spigot / CraftBukkit, [ProtocolLib](https://github.com/aadnk/ProtocolLib) needs to be installed.
 This does not apply when using Paper 1.16 build #503 or higher. 
@@ -30,4 +30,5 @@ See [Contact](https://docs.tcpshield.com/about-us)
 These wonderful contributors have helped TCPShield make this plugin better! 
 
 * [Paul Zhang](https://github.com/paulzhng)
+* [Draylar](https://github.com/Draylar)
 * [RyanDeLap](https://github.com/RyanDeLap)

build.gradle

@@ -19,6 +19,7 @@ buildscript {
 plugins {
     id 'java'
     id 'idea'
+    id 'fabric-loom' version '0.6-SNAPSHOT'
 }
 
 repositories {
@@ -40,6 +41,9 @@ repositories {
     maven {
         url = 'https://repo.velocitypowered.com/snapshots/'
     }
+    maven {
+        url = 'https://maven.fabricmc.net/'
+    }
     flatDir {
         dirs '/libs'
     }
@@ -59,6 +63,11 @@ dependencies {
     // Velocity
     compileOnly group: 'com.velocitypowered', name: 'velocity-api', version: '1.0.0-SNAPSHOT'
 
+    // Fabric
+    minecraft "com.mojang:minecraft:1.16.5"
+    mappings "net.fabricmc:yarn:1.16.5+build.5:v2"
+    modImplementation group: 'net.fabricmc', name: 'fabric-loader', version: '0.11.2'
+
     // Testing
     testImplementation group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.7.0-M1'
     testRuntimeOnly group: 'org.junit.jupiter', name: 'junit-jupiter-engine', version: '5.7.0-M1'

settings.gradle

@@ -0,0 +1,10 @@
+pluginManagement {
+    repositories {
+        jcenter()
+        maven {
+            name = 'Fabric'
+            url = 'https://maven.fabricmc.net/'
+        }
+        gradlePluginPortal()
+    }
+}

src/main/java/net/tcpshield/tcpshield/fabric/TCPShieldFabric.java

@@ -0,0 +1,18 @@
+package net.tcpshield.tcpshield.fabric;
+
+import net.fabricmc.api.ModInitializer;
+import net.tcpshield.tcpshield.HandshakePacketHandler;
+import net.tcpshield.tcpshield.fabric.impl.FabricConfigImpl;
+
+import java.util.logging.Logger;
+
+public class TCPShieldFabric implements ModInitializer {
+
+    public static final Logger LOGGER = Logger.getLogger("TCPShield");
+    public static final HandshakePacketHandler PACKET_HANDLER =  new HandshakePacketHandler(LOGGER, new FabricConfigImpl());
+
+    @Override
+    public void onInitialize() {
+        LOGGER.info("TCPShield has been loaded.");
+    }
+}

src/main/java/net/tcpshield/tcpshield/fabric/impl/FabricConfigImpl.java

@@ -0,0 +1,105 @@
+package net.tcpshield.tcpshield.fabric.impl;
+
+import net.fabricmc.loader.api.FabricLoader;
+import net.tcpshield.tcpshield.abstraction.TCPShieldConfig;
+import net.tcpshield.tcpshield.exception.TCPShieldInitializationException;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+public class FabricConfigImpl extends TCPShieldConfig {
+
+    private final Path configLocation = new File(FabricLoader.getInstance().getConfigDir().toString(), "tcpshield.yml").toPath();
+
+    public FabricConfigImpl() {
+        if(!configExists()) {
+            createDefaultConfig();
+        }
+
+        ConfigData config = loadConfig();
+
+        this.onlyProxy = config.onlyAllowProxyConnections;
+        this.ipWhitelistFolder = new File(FabricLoader.getInstance().getGameDirectory(), "ip-whitelist");
+        this.geyser = false;
+        this.debug = config.debugMode;
+    }
+
+    /**
+     * @return  whether the file specified in {@link FabricConfigImpl#configLocation} exists.
+     */
+    private boolean configExists() {
+        return Files.exists(configLocation);
+    }
+
+    /**
+     * Creates the default configuration file at the location specified in {@link FabricConfigImpl#configLocation}.
+     *
+     * <p>
+     * This operation will always override an existing configuration file if it exists.
+     * Callers should check {@link FabricConfigImpl#configExists()} if they wish to avoid this behavior.
+     */
+    private void createDefaultConfig() {
+        // Ensure the parent directory of our config file exists.
+        // If it does not exist, attempt to create it now.
+        Path parentDirectory = configLocation.getParent();
+        if (!Files.exists(parentDirectory) || !Files.isDirectory(parentDirectory)) {
+            parentDirectory.toFile().mkdirs();
+        }
+
+        // Copy the config.yml data from our mod jar to the loader config folder.
+        try (InputStream in = getClass().getClassLoader().getResourceAsStream("config.yml")) {
+            Files.copy(in, configLocation);
+        } catch (Exception e) {
+            throw new TCPShieldInitializationException(e);
+        }
+    }
+
+    private ConfigData loadConfig() {
+        try {
+            List<String> strings = Files.readAllLines(configLocation);
+
+            boolean onlyAllowProxyConnections = true;
+            boolean debugMode = false;
+
+            // Rudimentary config parsing
+            for (String line : strings) {
+                String[] keyValue = line.split(": ");
+
+                // A config option will only be valid if it is in the format 'a: b'.
+                // Ensure that is the case now.
+                if (keyValue.length == 2) {
+                    String key = keyValue[0];
+                    String value = keyValue[1];
+
+                    switch (key) {
+                        case "only-allow-proxy-connections":
+                            onlyAllowProxyConnections = Boolean.parseBoolean(value);
+                            break;
+                        case "debug-mode":
+                            debugMode = Boolean.parseBoolean(value);
+                            break;
+                    }
+                }
+            }
+
+            return new ConfigData(onlyAllowProxyConnections, debugMode);
+        } catch (Exception e) {
+            throw new TCPShieldInitializationException("Couldn't load config in config/tclshield.yml!");
+        }
+    }
+
+    private static class ConfigData {
+
+        protected boolean onlyAllowProxyConnections;
+        protected boolean debugMode;
+
+        public ConfigData(boolean onlyAllowProxyConnections, boolean debugMode) {
+            this.onlyAllowProxyConnections = onlyAllowProxyConnections;
+            this.debugMode = debugMode;
+        }
+    }
+}

src/main/java/net/tcpshield/tcpshield/fabric/impl/FabricPacketImpl.java

@@ -0,0 +1,24 @@
+package net.tcpshield.tcpshield.fabric.impl;
+
+import net.minecraft.network.packet.c2s.handshake.HandshakeC2SPacket;
+import net.tcpshield.tcpshield.abstraction.IPacket;
+import net.tcpshield.tcpshield.fabric.mixin.HandshakeC2SPacketAccessor;
+
+public class FabricPacketImpl implements IPacket {
+
+    private final HandshakeC2SPacket handshake;
+
+    public FabricPacketImpl(HandshakeC2SPacket handshake) {
+        this.handshake = handshake;
+    }
+
+    @Override
+    public String getRawPayload() {
+        return ((HandshakeC2SPacketAccessor) handshake).getAddress();
+    }
+
+    @Override
+    public void modifyOriginalPacket(String hostname) throws Exception {
+        // NO OPERATION
+    }
+}

src/main/java/net/tcpshield/tcpshield/fabric/impl/FabricPlayerImpl.java

@@ -0,0 +1,40 @@
+package net.tcpshield.tcpshield.fabric.impl;
+
+import net.minecraft.network.ClientConnection;
+import net.minecraft.network.packet.c2s.handshake.HandshakeC2SPacket;
+import net.minecraft.network.packet.s2c.login.LoginDisconnectS2CPacket;
+import net.minecraft.text.LiteralText;
+import net.tcpshield.tcpshield.abstraction.IPlayer;
+import net.tcpshield.tcpshield.exception.IPModificationFailureException;
+import net.tcpshield.tcpshield.fabric.mixin.ClientConnectionAccessor;
+
+import java.net.InetSocketAddress;
+
+public class FabricPlayerImpl implements IPlayer {
+
+    private final ClientConnection connection;
+    private String ip;
+
+    public FabricPlayerImpl(HandshakeC2SPacket packet, ClientConnection connection) {
+        this.connection = connection;
+        this.ip = ((InetSocketAddress) ((ClientConnectionAccessor) connection).getChannel().remoteAddress()).getAddress().getHostAddress();
+    }
+
+    @Override
+    public String getIP() {
+        return ip;
+    }
+
+    @Override
+    public void setIP(InetSocketAddress ip) throws IPModificationFailureException {
+        // At this point, the IP/connection believe the player has the IP of TCPShield.
+        // The ip passed into this method contains their CORRECT data, which we have to assign to the player network connection.
+        ((ClientConnectionAccessor) connection).setAddress(ip);
+        this.ip = ((InetSocketAddress) ((ClientConnectionAccessor) connection).getChannel().remoteAddress()).getAddress().getHostAddress();
+    }
+
+    @Override
+    public void disconnect() {
+        connection.disconnect(new LiteralText("Connection failed. Please try again or contact an administrator."));
+    }
+}

src/main/java/net/tcpshield/tcpshield/fabric/mixin/ClientConnectionAccessor.java

@@ -0,0 +1,20 @@
+package net.tcpshield.tcpshield.fabric.mixin;
+
+import io.netty.channel.Channel;
+import net.minecraft.network.ClientConnection;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+import java.net.SocketAddress;
+
+@Mixin(ClientConnection.class)
+public interface ClientConnectionAccessor {
+    @Accessor
+    void setAddress(SocketAddress address);
+
+    @Accessor
+    Channel getChannel();
+
+    @Accessor
+    SocketAddress getAddress();
+}

src/main/java/net/tcpshield/tcpshield/fabric/mixin/HandshakeC2SPacketAccessor.java

@@ -0,0 +1,11 @@
+package net.tcpshield.tcpshield.fabric.mixin;
+
+import net.minecraft.network.packet.c2s.handshake.HandshakeC2SPacket;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+@Mixin(HandshakeC2SPacket.class)
+public interface HandshakeC2SPacketAccessor {
+    @Accessor
+    String getAddress();
+}

src/main/java/net/tcpshield/tcpshield/fabric/mixin/ServerHandshakeMixin.java

@@ -0,0 +1,32 @@
+package net.tcpshield.tcpshield.fabric.mixin;
+
+import net.minecraft.network.ClientConnection;
+import net.minecraft.network.packet.c2s.handshake.HandshakeC2SPacket;
+import net.minecraft.server.network.ServerHandshakeNetworkHandler;
+import net.tcpshield.tcpshield.abstraction.IPacket;
+import net.tcpshield.tcpshield.abstraction.IPlayer;
+import net.tcpshield.tcpshield.fabric.TCPShieldFabric;
+import net.tcpshield.tcpshield.fabric.impl.FabricPacketImpl;
+import net.tcpshield.tcpshield.fabric.impl.FabricPlayerImpl;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(ServerHandshakeNetworkHandler.class)
+public class ServerHandshakeMixin {
+
+    @Shadow @Final private ClientConnection connection;
+
+    @Inject(
+            method = "onHandshake",
+            at = @At("HEAD"))
+    private void onHandshake(HandshakeC2SPacket handshake, CallbackInfo ci) {
+        IPacket packet = new FabricPacketImpl(handshake);
+        IPlayer player = new FabricPlayerImpl(handshake, connection);
+
+        TCPShieldFabric.PACKET_HANDLER.onHandshake(packet, player);
+    }
+}

src/main/resources/fabric.mod.json

@@ -0,0 +1,27 @@
+{
+  "schemaVersion": 1,
+  "id": "tcp-shield",
+  "version": "2.5",
+  "name": "TCPShield",
+  "description": "TCPShield IP parsing capabilities for Fabric",
+  "authors": [
+    "TCPShield"
+  ],
+  "contact": {
+    "homepage": "https://tcpshield.com"
+  },
+  "license": "MIT",
+  "environment": "*",
+  "entrypoints": {
+    "main": [
+      "net.tcpshield.tcpshield.fabric.TCPShieldFabric"
+    ]
+  },
+  "mixins": [
+    "tcpshield.mixins.json"
+  ],
+  "depends": {
+    "fabricloader": "*",
+    "minecraft": "*"
+  }
+}

src/main/resources/tcpshield.mixins.json

@@ -0,0 +1,14 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "net.tcpshield.tcpshield.fabric.mixin",
+  "compatibilityLevel": "JAVA_8",
+  "mixins": [
+    "ClientConnectionAccessor",
+    "HandshakeC2SPacketAccessor",
+    "ServerHandshakeMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}