From 88436c44a65f7984c114546255eab3674f5b7406 Mon Sep 17 00:00:00 2001
From: FlorianMichael <florian.michael07@gmail.com>
Date: Sun, 29 Jun 2025 21:45:47 +1000
Subject: [PATCH] #3854: Fix CustomClickAction read and write implementation

---
 .../md_5/bungee/protocol/DefinedPacket.java   | 32 +++++++++++++++++++
 .../net/md_5/bungee/protocol/TagUtil.java     |  2 ++
 .../protocol/packet/CustomClickAction.java    |  9 ++----
 3 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java b/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
index 0ee7b0de..1ccca2f0 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
@@ -48,6 +48,38 @@ public abstract class DefinedPacket
         }
     }
 
+    public <T> T readLengthPrefixed(Function<ByteBuf, T> reader, ByteBuf buf, int maxSize)
+    {
+        int size = readVarInt( buf );
+
+        if ( size > maxSize )
+        {
+            throw new OverflowPacketException( "Cannot read length prefixed with limit " + maxSize + " (got size of " + size + ")" );
+        }
+
+        return reader.apply( buf.readSlice( size ) );
+    }
+
+    public <T> void writeLengthPrefixed(T value, BiConsumer<T, ByteBuf> writer, ByteBuf buf, int maxSize)
+    {
+        ByteBuf tempBuffer = buf.alloc().buffer();
+        try
+        {
+            writer.accept( value, tempBuffer );
+
+            if ( tempBuffer.readableBytes() > maxSize )
+            {
+                throw new OverflowPacketException( "Cannot write length prefixed with limit " + maxSize + " (got size of " + tempBuffer.readableBytes() + ")" );
+            }
+
+            writeVarInt( tempBuffer.readableBytes(), buf );
+            buf.writeBytes( tempBuffer );
+        } finally
+        {
+            tempBuffer.release();
+        }
+    }
+
     public static void writeString(String s, ByteBuf buf)
     {
         writeString( s, buf, Short.MAX_VALUE );
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/TagUtil.java b/protocol/src/main/java/net/md_5/bungee/protocol/TagUtil.java
index b942d10b..74b963eb 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/TagUtil.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/TagUtil.java
@@ -323,6 +323,8 @@ public final class TagUtil
                 }
 
                 return jsonLongArray;
+            case Tag.END:
+                return JsonNull.INSTANCE;
             default:
                 throw new IllegalArgumentException( "Unknown NBT tag: " + tag );
         }
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/packet/CustomClickAction.java b/protocol/src/main/java/net/md_5/bungee/protocol/packet/CustomClickAction.java
index 9aa1e409..b1bbd4a5 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/packet/CustomClickAction.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/packet/CustomClickAction.java
@@ -26,19 +26,14 @@ public class CustomClickAction extends DefinedPacket
     public void read(ByteBuf buf, Protocol protocol, ProtocolConstants.Direction direction, int protocolVersion)
     {
         id = readString( buf );
-        data = readNullable( (buf0) -> (TypedTag) readTag( buf0, protocolVersion, new NBTLimiter( 32768L, 16 ) ), buf );
+        data = readLengthPrefixed( (buf0) -> (TypedTag) readTag( buf0, protocolVersion, new NBTLimiter( 32768L, 16 ) ), buf, 65536 );
     }
 
     @Override
     public void write(ByteBuf buf, Protocol protocol, ProtocolConstants.Direction direction, int protocolVersion)
     {
         writeString( id, buf );
-        writeNullable( data, (data0, buf0) -> writeTag( data0, buf0, protocolVersion ), buf );
-    }
-
-    @Override
-    public void write(ByteBuf buf)
-    {
+        writeLengthPrefixed( data, (data0, buf0) -> writeTag( data0, buf0, protocolVersion ), buf, 65536 );
     }
 
     @Override