PaperMC/patches/server/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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -0,0 +0,0 @@ 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;
@@ -0,0 +0,0 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         }
         OutgoingChatMessage outgoing = OutgoingChatMessage.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
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -0,0 +0,0 @@ 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(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 {
+                final PlayerChatMessage playerChatMessage = PlayerChatMessage.system(msg).withResult(new net.minecraft.network.chat.ChatDecorator.ModernResult(Component.literal(msg), true, false));
+                // TODO chat decorating
+                // TODO text filtering
+                this.getHandle().connection.chat(msg, playerChatMessage, false);
+            }
+        }
+        // Paper end
     }
 
     @Override
diff --git a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/spigotmc/AsyncCatcher.java
+++ b/src/main/java/org/spigotmc/AsyncCatcher.java
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -0,0 +0,0 @@ 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( " " );