Paper/patches/server/0047-Ensure-commands-are-not-ran-async.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 3 Mar 2016 01:17:12 -0600
Subject: [PATCH] Ensure commands are not ran async

Plugins calling Player.chat("/foo") or Server.dispatchCommand() could
trigger the server to execute a command while on another thread.

These commands would then process EXPECTING to be on the main thread, leaving to
very hard to trace concurrency issues.

This change will synchronize the command execution back to the main thread, causing a
big slowdown in execution but throwing an exception at same time to raise awareness
that it is happening so that plugin authors can fix their code to stop executing commands async.

This also properly splits up the chat and command handling to reflect the server now
having separate packets for both, and the client always using the correct packet. Text
from a chat packet should never be parsed into a command, even if it starts with the `/`
character.

Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 955902a36c01697999e08a218887e90946a04b3a..44e9edb76a518b12b1f20e73343ed720740d8662 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -2023,7 +2023,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         return true;
     }
 
-    private static boolean isChatMessageIllegal(String message) {
+    public static boolean isChatMessageIllegal(String message) { // Paper - private -> public
         for (int i = 0; i < message.length(); ++i) {
             if (!SharedConstants.isAllowedChatCharacter(message.charAt(i))) {
                 return true;
@@ -2040,7 +2040,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         }
         OutgoingPlayerChatMessage outgoing = OutgoingPlayerChatMessage.create(original);
 
-        if (!async && s.startsWith("/")) {
+        if (false && !async && s.startsWith("/")) { // Paper - don't handle commands in chat logic
             this.handleCommand(s);
         } else if (this.player.getChatVisibility() == ChatVisiblity.SYSTEM) {
             // Do nothing, this is coming from a plugin
@@ -2143,7 +2143,29 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         }
     }
 
-    private void handleCommand(String s) {
+    public void handleCommand(String s) { // Paper - private -> public
+        // Paper Start
+        if (!org.spigotmc.AsyncCatcher.shuttingDown && !org.bukkit.Bukkit.isPrimaryThread()) {
+            LOGGER.error("Command Dispatched Async: " + s);
+            LOGGER.error("Please notify author of plugin causing this execution to fix this bug! see: http://bit.ly/1oSiM6C", new Throwable());
+            Waitable<Void> wait = new Waitable<>() {
+                @Override
+                protected Void evaluate() {
+                    ServerGamePacketListenerImpl.this.handleCommand(s);
+                    return null;
+                }
+            };
+            server.processQueue.add(wait);
+            try {
+                wait.get();
+                return;
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt(); // This is proper habit for java. If we aren't handling it, pass it on!
+            } catch (Exception e) {
+                throw new RuntimeException("Exception processing chat command", e.getCause());
+            }
+        }
+        // Paper End
         co.aikar.timings.MinecraftTimings.playerCommandTimer.startTiming(); // Paper
         if ( org.spigotmc.SpigotConfig.logCommands ) // Spigot
         this.LOGGER.info(this.player.getScoreboardName() + " issued server command: " + s);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 415393e965c7253412ec4d893c3e62ad14dd69f2..846c5144fefd1dfd1bbd8e6f82bd9248be34ad1a 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -861,6 +861,28 @@ public final class CraftServer implements Server {
         Validate.notNull(commandLine, "CommandLine cannot be null");
         org.spigotmc.AsyncCatcher.catchOp("command dispatch"); // Spigot
 
+        // Paper Start
+        if (!org.spigotmc.AsyncCatcher.shuttingDown && !Bukkit.isPrimaryThread()) {
+            final CommandSender fSender = sender;
+            final String fCommandLine = commandLine;
+            Bukkit.getLogger().log(Level.SEVERE, "Command Dispatched Async: " + commandLine);
+            Bukkit.getLogger().log(Level.SEVERE, "Please notify author of plugin causing this execution to fix this bug! see: http://bit.ly/1oSiM6C", new Throwable());
+            org.bukkit.craftbukkit.util.Waitable<Boolean> wait = new org.bukkit.craftbukkit.util.Waitable<Boolean>() {
+                @Override
+                protected Boolean evaluate() {
+                    return dispatchCommand(fSender, fCommandLine);
+                }
+            };
+            net.minecraft.server.MinecraftServer.getServer().processQueue.add(wait);
+            try {
+                return wait.get();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt(); // This is proper habit for java. If we aren't handling it, pass it on!
+            } catch (Exception e) {
+                throw new RuntimeException("Exception processing dispatch command", e.getCause());
+            }
+        }
+        // Paper End
         if (this.commandMap.dispatch(sender, commandLine)) {
             return true;
         }
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 82a640887a75c360539c1787dbbb32750f6b1379..2666e55d72fd7731a2bde42d690762a2747dac90 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -461,7 +461,19 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     public void chat(String msg) {
         if (this.getHandle().connection == null) return;
 
-        this.getHandle().connection.chat(msg, PlayerChatMessage.system(new ChatMessageContent(msg)), false);
+        // Paper start - improve chat handling
+        if (ServerGamePacketListenerImpl.isChatMessageIllegal(msg)) {
+            this.getHandle().connection.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS);
+        } else {
+            if (msg.startsWith("/")) {
+                this.getHandle().connection.handleCommand(msg);
+            } else {
+                // TODO text filtering
+                // TODO chat decorating
+                this.getHandle().connection.chat(msg, PlayerChatMessage.system(new net.minecraft.network.chat.ChatMessageContent(msg)), false);
+            }
+        }
+        // Paper en
     }
 
     @Override
diff --git a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
index 19c44daaa407b7c1c7a7ffe56fef8c8814c6d5b2..6a073a9dc44d93eba296a0e18a9c7be8a7881725 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -13,6 +13,7 @@ public class ServerShutdownThread extends Thread {
     public void run() {
         try {
             org.spigotmc.AsyncCatcher.enabled = false; // Spigot
+            org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
             this.server.close();
         } finally {
             try {
diff --git a/src/main/java/org/spigotmc/AsyncCatcher.java b/src/main/java/org/spigotmc/AsyncCatcher.java
index 78669fa035b7537ff7e533cf32aaf2995625424f..7585a30e8f063ac2656b5de519b1e9edaceffbc7 100644
--- a/src/main/java/org/spigotmc/AsyncCatcher.java
+++ b/src/main/java/org/spigotmc/AsyncCatcher.java
@@ -6,6 +6,7 @@ public class AsyncCatcher
 {
 
     public static boolean enabled = true;
+    public static boolean shuttingDown = false; // Paper
 
     public static void catchOp(String reason)
     {
diff --git a/src/main/java/org/spigotmc/RestartCommand.java b/src/main/java/org/spigotmc/RestartCommand.java
index 882e93ad4471e3688f2fcfb1e6f16926786ee5e7..94d8ba376cd1f024b244654cac9bb62bb19e3060 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -43,6 +43,7 @@ public class RestartCommand extends Command
     private static void restart(final String restartScript)
     {
         AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
+        org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
         try
         {
             String[] split = restartScript.split( " " );