Handle cookie responses inside Limbo (Player#requestCookie support)

api/src/main/java/net/elytrium/limboapi/api/LimboSessionHandler.java

@@ -8,6 +8,7 @@
 package net.elytrium.limboapi.api;
 
 import net.elytrium.limboapi.api.player.LimboPlayer;
+import net.kyori.adventure.key.Key;
 
 public interface LimboSessionHandler {
 
@@ -50,6 +51,19 @@ default void onGeneric(Object packet) {
 
   }
 
+  /**
+   * Called when the client sends a cookie response (reply to {@code Player#requestCookie}) while
+   * the player is still inside the Limbo. The response is also buffered and replayed as a
+   * {@code CookieReceiveEvent} when the player is handed back to Velocity, so this hook is meant
+   * for handlers that need the cookie value during the Limbo session itself.
+   *
+   * @param key  the cookie key
+   * @param data the cookie payload
+   */
+  default void onCookieResponse(Key key, byte[] data) {
+
+  }
+
   default void onDisconnect() {
 
   }

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.5.0-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

plugin/build.gradle

@@ -276,6 +276,43 @@ File getServerJar(String version) {
   return jarFile
 }
 
+// Some Minecraft versions require a newer JDK to run their data generator than the JDK running Gradle
+// (e.g. 26.1 needs Java 25). Pick a suitable installed JDK by reading sibling JDKs' "release" files.
+@SuppressWarnings('GrMethodMayBeStatic')
+File selectJavaHome(int requiredMajor) {
+  File current = new File(System.getProperty("java.home"))
+  if (requiredMajor <= Runtime.version().feature()) {
+    return current
+  }
+
+  boolean win = System.getProperty("os.name").toLowerCase().contains("win")
+  File jdksDir = current.getParentFile()
+  File best = null
+  int bestMajor = Integer.MAX_VALUE
+  jdksDir.listFiles()?.each { File dir ->
+    File release = new File(dir, "release")
+    File javaExe = new File(dir, win ? "bin/java.exe" : "bin/java")
+    if (!release.exists() || !javaExe.exists()) {
+      return
+    }
+    String verLine = release.readLines().find { it.startsWith("JAVA_VERSION=") }
+    if (verLine == null) {
+      return
+    }
+    String ver = verLine.substring(verLine.indexOf('=') + 1).replace('"', '').trim()
+    int major = ver.startsWith("1.") ? Integer.parseInt(ver.split("\\.")[1]) : Integer.parseInt(ver.split("[._-]")[0])
+    if (major >= requiredMajor && major < bestMajor) {
+      best = dir
+      bestMajor = major
+    }
+  }
+  if (best == null) {
+    throw new RuntimeException("No installed JDK satisfies required Java ${requiredMajor} (searched ${jdksDir}). Install JDK ${requiredMajor}+.")
+  }
+  this.println("> Using JDK ${bestMajor} at ${best} for data generation (version requires Java ${requiredMajor})")
+  return best
+}
+
 File generateData(MinecraftVersion version) {
   File cache = getGeneratedCache(version)
   if (cache != null) {
@@ -292,6 +329,10 @@ File generateData(MinecraftVersion version) {
     // Ignored.
   }
 
+  Object versionManifest = new JsonSlurper().parse(new File(parent, "manifest.json"))
+  int requiredJava = (versionManifest.javaVersion?.majorVersion ?: Runtime.version().feature()) as int
+  File javaHome = this.selectJavaHome(requiredJava)
+
   String command
   if (version >= MinecraftVersion.MINECRAFT_1_18) {
     command = "\"%s\" -DbundlerMainClass=net.minecraft.data.Main -jar \"${jarFile.getAbsolutePath()}\" --reports --server"
@@ -301,13 +342,15 @@ File generateData(MinecraftVersion version) {
 
   List<String> commandLine;
   if (System.getProperty("os.name").toLowerCase().contains("win")) {
-    File java = new File(System.getProperty("java.home"), "bin/java.exe")
+    File java = new File(javaHome, "bin/java.exe")
     commandLine = ["cmd", "/c", String.format(command, java)]
   } else {
-    File java = new File(System.getProperty("java.home"), "bin/java")
+    File java = new File(javaHome, "bin/java")
     commandLine = ["bash", "-c", String.format(command, java)]
   }
-  commandLine.execute([], parent).waitFor()
+  Process process = commandLine.execute([], parent)
+  process.consumeProcessOutput() // drain stdout/stderr so the generator can't deadlock on a full pipe buffer
+  process.waitFor()
 
   // Remove/compact files, reduces disk usage from ~2.9gb to ~92mb (or ~9.5mb on a compressed filesystem)
   jarFile.delete()

plugin/src/main/java/net/elytrium/limboapi/injection/login/LoginTasksQueue.java

@@ -39,6 +39,7 @@
 import com.velocitypowered.api.event.connection.LoginEvent;
 import com.velocitypowered.api.event.connection.PostLoginEvent;
 import com.velocitypowered.api.event.permission.PermissionsSetupEvent;
+import com.velocitypowered.api.event.player.CookieReceiveEvent;
 import com.velocitypowered.api.event.player.GameProfileRequestEvent;
 import com.velocitypowered.api.event.player.PlayerClientBrandEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
@@ -48,13 +49,15 @@
 import com.velocitypowered.api.util.GameProfile;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
+import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.connection.client.AuthSessionHandler;
 import com.velocitypowered.proxy.connection.client.ClientConfigSessionHandler;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.connection.client.InitialConnectSessionHandler;
 import com.velocitypowered.proxy.network.Connections;
 import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.packet.LegacyPlayerListItemPacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.UpsertPlayerInfoPacket;
 import com.velocitypowered.proxy.protocol.packet.chat.ComponentHolder;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
@@ -77,6 +80,7 @@
 import net.elytrium.limboapi.injection.login.confirmation.LoginConfirmHandler;
 import net.elytrium.limboapi.server.LimboSessionHandlerImpl;
 import net.elytrium.limboapi.utils.LambdaUtil;
+import net.kyori.adventure.key.Key;
 import net.kyori.adventure.text.Component;
 import org.slf4j.Logger;
 
@@ -272,6 +276,26 @@ private void connectToServer(Logger logger, ConnectedPlayer player, MinecraftCon
             throw new ReflectionException(e);
           }
         }
+
+        for (ServerboundCookieResponsePacket cookie : sessionHandler.getCookies()) {
+          // Replay cookie responses buffered while in the Limbo, now that the player is being
+          // handed back to Velocity. Mirrors ClientPlaySessionHandler: fire CookieReceiveEvent
+          // and forward the (possibly rewritten) response to the backend when one is connected.
+          this.server.getEventManager()
+              .fire(new CookieReceiveEvent(this.player, cookie.getKey(), cookie.getPayload()))
+              .thenAcceptAsync(event -> {
+                if (event.getResult().isAllowed()) {
+                  VelocityServerConnection serverConnection = this.player.getConnectedServer();
+                  if (serverConnection != null) {
+                    Key resultedKey = event.getResult().getKey() == null
+                        ? event.getOriginalKey() : event.getResult().getKey();
+                    byte[] resultedData = event.getResult().getData() == null
+                        ? event.getOriginalData() : event.getResult().getData();
+                    serverConnection.ensureConnected().write(new ServerboundCookieResponsePacket(resultedKey, resultedData));
+                  }
+                }
+              }, this.player.getConnection().eventLoop());
+        }
       }
 
       this.plugin.setActiveSessionHandler(connection, StateRegistry.CONFIG, configHandler);

plugin/src/main/java/net/elytrium/limboapi/server/LimboSessionHandlerImpl.java

@@ -31,6 +31,7 @@
 import com.velocitypowered.proxy.protocol.packet.ClientSettingsPacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.chat.keyed.KeyedPlayerChatPacket;
 import com.velocitypowered.proxy.protocol.packet.chat.keyed.KeyedPlayerCommandPacket;
 import com.velocitypowered.proxy.protocol.packet.chat.legacy.LegacyChatPacket;
@@ -47,6 +48,8 @@
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.ThreadLocalRandom;
@@ -88,6 +91,7 @@ public class LimboSessionHandlerImpl implements MinecraftSessionHandler {
   private LimboPlayer limboPlayer;
   private ClientSettingsPacket settings;
   private String brand;
+  private final List<ServerboundCookieResponsePacket> cookies = new ArrayList<>();
   private ScheduledFuture<?> keepAliveTask;
   private ScheduledFuture<?> chatSessionTimeoutTask;
   private ScheduledFuture<?> respawnTask;
@@ -118,6 +122,7 @@ public LimboSessionHandlerImpl(LimboAPI plugin, LimboImpl limbo, ConnectedPlayer
     if (originalHandler instanceof LimboSessionHandlerImpl sessionHandler) {
       this.settings = sessionHandler.getSettings();
       this.brand = sessionHandler.getBrand();
+      this.cookies.addAll(sessionHandler.getCookies());
     }
   }
 
@@ -324,6 +329,18 @@ public boolean handle(SessionPlayerCommandPacket packet) {
     return this.handleChat("/" + packet.getCommand());
   }
 
+  @Override
+  public boolean handle(ServerboundCookieResponsePacket packet) {
+    // The player is usually not attached to a backend while inside a Limbo, so the cookie
+    // response can't be delivered here. Buffer it (just like ClientSettings/brand) and let
+    // LoginTasksQueue replay it once the player is handed back to Velocity's session handling.
+    this.cookies.add(packet);
+    // Also surface it live to the Limbo handler so plugins can use the cookie value during the
+    // session (the buffered CookieReceiveEvent only fires later, on hand-back to Velocity).
+    this.callback.onCookieResponse(packet.getKey(), packet.getPayload());
+    return true;
+  }
+
   private boolean handleChat(String message) {
     int messageLength = message.length();
     if (messageLength > Settings.IMP.MAIN.MAX_CHAT_MESSAGE_LENGTH) {
@@ -501,6 +518,10 @@ public String getBrand() {
     return this.brand;
   }
 
+  public List<ServerboundCookieResponsePacket> getCookies() {
+    return this.cookies;
+  }
+
   static {
     try {
       TEARDOWN_METHOD = MethodHandles.privateLookupIn(ConnectedPlayer.class, MethodHandles.lookup())