From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Dreeam <61569423+Dreeam-qwq@users.noreply.github.com>
Date: Sat, 9 Mar 2024 10:54:59 -0500
Subject: [PATCH] Block log4j rce exploit in chat


diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index bf14f2a0eef3d3964d4ce1f09473e5106f20ebb8..0cbfa34b5750bb253a51ffdf19ff76301927aeae 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -2234,6 +2234,9 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             return;
         }
         // CraftBukkit end
+
+        if (ServerGamePacketListenerImpl.isLog4jExploit(packet.message())) return; // Leaf - Block log4j rce exploit in chat
+
         if (ServerGamePacketListenerImpl.isChatMessageIllegal(packet.message())) {
             this.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS); // Paper - add cause
         } else {
@@ -2409,6 +2412,15 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         }
     }
 
+    // Leaf start - Block log4j rce exploit in chat
+    public static boolean isLog4jExploit(String message) {
+        java.util.regex.Pattern pattern = java.util.regex.Pattern.compile(".*\\$\\{[^}]*}.*");
+        java.util.regex.Matcher matcher = pattern.matcher(message);
+
+        return matcher.find();
+    }
+    // Leaf end
+
     public static boolean isChatMessageIllegal(String message) {
         for (int i = 0; i < message.length(); ++i) {
             if (!SharedConstants.isAllowedChatCharacter(message.charAt(i))) {
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 80ce7779fc2437444ea16db3d09250f82cef0ed5..4eda6d6f6e9fc34852d4b32a26c4f5a564a28f5d 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -670,6 +670,8 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
         if (this.getHandle().connection == null) return;
 
+        if (ServerGamePacketListenerImpl.isLog4jExploit(msg)) return; // Leaf - Block log4j rce exploit in chat
+
         // 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); // Paper - kick event causes