From c14ceb315dae5d623dab8679de3234a7f0f67321 Mon Sep 17 00:00:00 2001
From: Andrew Steinborn <git@steinborn.me>
Date: Wed, 1 Jan 2020 10:14:15 -0500
Subject: [PATCH] Return the magic-3 loop again... :(

---
 .../netty/MinecraftCompressDecoder.java       |  1 -
 .../netty/MinecraftVarintFrameDecoder.java    | 32 ++++++++++++++-----
 2 files changed, 24 insertions(+), 9 deletions(-)

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 ebf7f927..cf68e134 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
@@ -30,7 +30,6 @@ public class MinecraftCompressDecoder extends MessageToMessageDecoder<ByteBuf> {
     if (claimedUncompressedSize == 0) {
       // Strip the now-useless uncompressed size, this message is already uncompressed.
       out.add(in.retainedSlice());
-      in.skipBytes(in.readableBytes());
       return;
     }
 
diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java
index c8fec71a..3adc8ac3 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java
@@ -4,22 +4,38 @@ import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.ByteToMessageDecoder;
+import io.netty.handler.codec.CorruptedFrameException;
 import java.util.List;
 
 public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder {
 
   @Override
   protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
-    while (in.isReadable()) {
-      int ri = in.readerIndex();
-      int packetLength = ProtocolUtils.readVarInt(in);
+    read_lens: while (in.isReadable()) {
+      int origReaderIndex = in.readerIndex();
+      for (int i = 0; i < 3; i++) {
+        if (!in.isReadable()) {
+          in.readerIndex(origReaderIndex);
+          return;
+        }
 
-      if (in.readableBytes() >= packetLength) {
-        out.add(in.readBytes(packetLength));
-      } else {
-        in.readerIndex(ri);
-        break;
+        byte read = in.readByte();
+        if (read >= 0) {
+          // Make sure reader index of length buffer is returned to the beginning
+          in.readerIndex(origReaderIndex);
+          int packetLength = ProtocolUtils.readVarInt(in);
+
+          if (in.readableBytes() >= packetLength) {
+            out.add(in.readBytes(packetLength));
+            continue read_lens;
+          } else {
+            in.readerIndex(origReaderIndex);
+            return;
+          }
+        }
       }
+
+      throw new CorruptedFrameException("VarInt too big");
     }
   }
 }