Paper added an option to disable username validation for a connection

Co-authored-by: Camotoy <20743703+camotoy@users.noreply.github.com>

spigot/src/main/java/org/geysermc/floodgate/SpigotPlugin.java

@@ -28,6 +28,7 @@ package org.geysermc.floodgate;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 import org.bukkit.plugin.java.JavaPlugin;
+import org.geysermc.floodgate.api.handshake.HandshakeHandlers;
 import org.geysermc.floodgate.api.logger.FloodgateLogger;
 import org.geysermc.floodgate.module.PluginMessageModule;
 import org.geysermc.floodgate.module.ServerCommonModule;
@@ -35,6 +36,7 @@ import org.geysermc.floodgate.module.SpigotAddonModule;
 import org.geysermc.floodgate.module.SpigotCommandModule;
 import org.geysermc.floodgate.module.SpigotListenerModule;
 import org.geysermc.floodgate.module.SpigotPlatformModule;
+import org.geysermc.floodgate.util.SpigotHandshakeHandler;
 import org.geysermc.floodgate.util.SpigotProtocolSupportHandler;
 import org.geysermc.floodgate.util.SpigotProtocolSupportListener;
 
@@ -66,6 +68,10 @@ public final class SpigotPlugin extends JavaPlugin {
                 new PluginMessageModule()
         );
 
+        //todo add proper support for disabling things on shutdown and enabling this on enable
+        injector.getInstance(HandshakeHandlers.class)
+                .addHandshakeHandler(injector.getInstance(SpigotHandshakeHandler.class));
+
         // add ProtocolSupport support (hack)
         if (getServer().getPluginManager().getPlugin("ProtocolSupport") != null) {
             injector.getInstance(SpigotProtocolSupportHandler.class);

spigot/src/main/java/org/geysermc/floodgate/addon/data/SpigotDataHandler.java

@@ -37,10 +37,12 @@ import org.geysermc.floodgate.config.FloodgateConfig;
 import org.geysermc.floodgate.player.FloodgateHandshakeHandler;
 import org.geysermc.floodgate.player.FloodgateHandshakeHandler.HandshakeResult;
 import org.geysermc.floodgate.util.ClassNames;
+import org.geysermc.floodgate.util.ProxyUtils;
 
 public final class SpigotDataHandler extends CommonDataHandler {
     private Object networkManager;
     private FloodgatePlayer player;
+    private boolean proxyData;
 
     public SpigotDataHandler(
             FloodgateHandshakeHandler handshakeHandler,
@@ -72,13 +74,18 @@ public final class SpigotDataHandler extends CommonDataHandler {
             return true;
         }
 
-        // Paper now has username validation, so we have to help Paper to bypass the check.
+        // the server will do all the work if BungeeCord mode is enabled,
-        // The username is only validated in the login start packet, and that packet doesn't reach
+        // otherwise we have to help the server.
-        // the server handler when we call our own login cycle.
+        proxyData = ProxyUtils.isProxyData();
 
-        // After internal discussion, we've decided to require assistance for all Spigot platforms,
+        if (!proxyData) {
-        // in case Spigot decides to add username validation as well.
+            // Use a spoofedUUID for initUUID (just like Bungeecord)
-        return false;
+            setValue(networkManager, "spoofedUUID", player.getCorrectUniqueId());
+        }
+
+        // we can only remove the handler if the data is proxy data and username validation doesn't
+        // exist. Otherwise, we need to wait and disable it.
+        return proxyData && ClassNames.PAPER_DISABLE_USERNAME_VALIDATION == null;
     }
 
     @Override
@@ -131,16 +138,22 @@ public final class SpigotDataHandler extends CommonDataHandler {
                 return true;
             }
 
+            if (ClassNames.PAPER_DISABLE_USERNAME_VALIDATION != null) {
+                // ensure that Paper will not be checking
+                setValue(packetListener, ClassNames.PAPER_DISABLE_USERNAME_VALIDATION, true);
+                if (proxyData) {
+                    // the server will handle the rest if we have proxy data
+                    ctx.pipeline().remove(this);
+                    return false;
+                }
+            }
+
             // set the player his GameProfile, we can't change the username without this
             GameProfile gameProfile = new GameProfile(
                     player.getCorrectUniqueId(), player.getCorrectUsername()
             );
             setValue(packetListener, ClassNames.LOGIN_PROFILE, gameProfile);
 
-            //todo we can remove this line + the initUUID line, but then if a skin has been sent
-            // from a proxy using bungee data, we won't be able to show it
-            setValue(networkManager, "spoofedUUID", player.getCorrectUniqueId());
-
             // we have to fake the offline player (login) cycle
             // just like on Spigot:
 

spigot/src/main/java/org/geysermc/floodgate/util/ClassNames.java

@@ -25,6 +25,7 @@
 
 package org.geysermc.floodgate.util;
 
+import static org.geysermc.floodgate.util.ReflectionUtils.getField;
 import static org.geysermc.floodgate.util.ReflectionUtils.getFieldOfType;
 import static org.geysermc.floodgate.util.ReflectionUtils.getMethod;
 
@@ -37,6 +38,7 @@ import java.lang.reflect.Method;
 import java.net.SocketAddress;
 import org.bukkit.Bukkit;
 import org.bukkit.OfflinePlayer;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 @SuppressWarnings("PMD.SystemPrintln")
 public class ClassNames {
@@ -56,6 +58,8 @@ public class ClassNames {
     public static final Field HANDSHAKE_HOST;
     public static final Field LOGIN_PROFILE;
     public static final Field PACKET_LISTENER;
+    @Nullable
+    public static final Field PAPER_DISABLE_USERNAME_VALIDATION;
 
     public static final Method GET_PROFILE_METHOD;
     public static final Method LOGIN_DISCONNECT;
@@ -157,6 +161,13 @@ public class ClassNames {
 
         FIRE_LOGIN_EVENTS = getMethod(LOGIN_HANDLER, "fireEvents");
         checkNotNull(FIRE_LOGIN_EVENTS, "fireEvents from LoginHandler");
+
+        PAPER_DISABLE_USERNAME_VALIDATION = getField(LOGIN_LISTENER,
+                "iKnowThisMayNotBeTheBestIdeaButPleaseDisableUsernameValidation");
+        if (Constants.DEBUG_MODE) {
+            System.out.println("Paper disable username validation field exists? " +
+                    (PAPER_DISABLE_USERNAME_VALIDATION != null));
+        }
     }
 
     private static Class<?> getClassOrFallBack(String className, String fallbackName) {

spigot/src/main/java/org/geysermc/floodgate/util/ProxyUtils.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Floodgate
+ */
+
+package org.geysermc.floodgate.util;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.geysermc.floodgate.util.ReflectionUtils.getField;
+
+import java.lang.reflect.Field;
+
+@SuppressWarnings("ConstantConditions")
+public final class ProxyUtils {
+    private static final Field IS_BUNGEE_DATA;
+    private static final Field IS_MODERN_FORWARDING;
+
+    static {
+        Class<?> spigotConfig = ReflectionUtils.getClass("org.spigotmc.SpigotConfig");
+        IS_BUNGEE_DATA = getField(spigotConfig, "bungee");
+        checkNotNull(IS_BUNGEE_DATA, "bungee field cannot be null. Are you using CraftBukkit?");
+
+        Field velocitySupport;
+        try {
+            Class<?> paperConfig = Class.forName("com.destroystokyo.paper.PaperConfig");
+            velocitySupport = getField(paperConfig, "velocitySupport");
+        } catch (ClassNotFoundException e) {
+            // We're not on a platform that has modern forwarding
+            velocitySupport = null; // NOPMD - there's really not a better way around this unless you want to use an optional
+        }
+        IS_MODERN_FORWARDING = velocitySupport;
+    }
+
+    public static boolean isProxyData() {
+        return isBungeeData() || isVelocitySupport();
+    }
+
+    private static boolean isBungeeData() {
+        return ReflectionUtils.getCastedValue(null, IS_BUNGEE_DATA);
+    }
+
+    private static boolean isVelocitySupport() {
+        if (IS_MODERN_FORWARDING == null) {
+            return false;
+        }
+
+        return ReflectionUtils.getCastedValue(null, IS_MODERN_FORWARDING);
+    }
+}

spigot/src/main/java/org/geysermc/floodgate/util/SpigotHandshakeHandler.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2019-2022 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Floodgate
+ */
+
+package org.geysermc.floodgate.util;
+
+import com.google.inject.Inject;
+import java.util.UUID;
+import org.geysermc.floodgate.api.handshake.HandshakeData;
+import org.geysermc.floodgate.api.handshake.HandshakeHandler;
+import org.geysermc.floodgate.api.logger.FloodgateLogger;
+
+public class SpigotHandshakeHandler implements HandshakeHandler {
+    @Inject
+    private FloodgateLogger logger;
+
+    @Override
+    public void handle(HandshakeData data) {
+        BedrockData bedrockData = data.getBedrockData();
+        UUID correctUuid = data.getCorrectUniqueId();
+
+        // replace the ip and uuid with the Bedrock client IP and an uuid based of the xuid
+        String[] split = data.getHostname().split("\0");
+        if (split.length >= 3) {
+            if (logger.isDebug()) {
+                logger.info("Replacing hostname arg1 '{}' with '{}' and arg2 '{}' with '{}'",
+                        split[1], bedrockData.getIp(), split[2], correctUuid.toString()
+                );
+            }
+            split[1] = bedrockData.getIp();
+            split[2] = correctUuid.toString();
+        }
+        data.setHostname(String.join("\0", split));
+    }
+}