From d9f1016bd57d50f5052bb90222894adb40fd256c Mon Sep 17 00:00:00 2001
From: Jones <73846784+jonesdevelopment@users.noreply.github.com>
Date: Fri, 14 Mar 2025 10:26:59 -0500
Subject: [PATCH] Validate uncompressed packet size (#1527)

* Validate uncompressed packet size

* Fix debug using incorrect value
---
 .../proxy/protocol/netty/MinecraftCompressDecoder.java         | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java
index 6e7fb4d4..5321b6ac 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java
@@ -52,6 +52,9 @@ public class MinecraftCompressDecoder extends MessageToMessageDecoder<ByteBuf> {
   protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
     int claimedUncompressedSize = ProtocolUtils.readVarInt(in);
     if (claimedUncompressedSize == 0) {
+      int actualUncompressedSize = in.readableBytes();
+      checkFrame(actualUncompressedSize < threshold, "Actual uncompressed size %s is greater than"
+              + " threshold %s", actualUncompressedSize, threshold);
       // This message is not compressed.
       out.add(in.retain());
       return;