From c856635ac580217638fd328eeb9468c665430ca7 Mon Sep 17 00:00:00 2001 From: Andrew Steinborn Date: Sun, 31 May 2020 08:14:33 -0400 Subject: [PATCH] Try two, with improved state maintenance and some bugs fixed --- .../netty/MinecraftVarintFrameDecoder.java | 82 +++++++++++++------ 1 file changed, 59 insertions(+), 23 deletions(-) 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 a4da29a76..6cf258e6b 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 @@ -1,15 +1,17 @@ package com.velocitypowered.proxy.protocol.netty; -import com.velocitypowered.proxy.protocol.ProtocolUtils; import com.velocitypowered.proxy.util.except.QuietException; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.ByteToMessageDecoder; +import io.netty.util.ByteProcessor; import java.util.List; public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder { private static final QuietException BAD_LENGTH_CACHED = new QuietException("Bad packet length"); + private static final QuietException VARINT_BIG_CACHED = new QuietException("VarInt too big"); + private final VarintByteDecoder reader = new VarintByteDecoder(); @Override protected void decode(ChannelHandlerContext ctx, ByteBuf in, List out) { @@ -18,31 +20,65 @@ public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder { return; } - read_lens: while (in.isReadable()) { - int origReaderIndex = in.readerIndex(); - for (int i = 0; i < 3; i++) { - if (!in.isReadable()) { - in.readerIndex(origReaderIndex); - return; - } + while (in.isReadable()) { + reader.reset(); - 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; - } - } + int varintEnd = in.forEachByte(reader); + if (varintEnd == -1) { + // We tried to go beyond the end of the buffer. This is probably a good sign that the + // buffer was too short to hold a proper varint. + return; } - throw BAD_LENGTH_CACHED; + if (reader.result == DecodeResult.SUCCESS) { + if (reader.readVarint < 0) { + throw BAD_LENGTH_CACHED; + } + + int minimumRead = reader.bytesRead + reader.readVarint; + if (in.isReadable(minimumRead)) { + out.add(in.retainedSlice(varintEnd + 1, reader.readVarint)); + in.skipBytes(minimumRead); + } else { + return; + } + } else if (reader.result == DecodeResult.TOO_BIG) { + throw VARINT_BIG_CACHED; + } else if (reader.result == DecodeResult.TOO_SHORT) { + // No-op: we couldn't get a useful result. + } } } + + private static class VarintByteDecoder implements ByteProcessor { + private int readVarint; + private int bytesRead; + private DecodeResult result = DecodeResult.TOO_SHORT; + + @Override + public boolean process(byte k) { + readVarint |= (k & 0x7F) << bytesRead++ * 7; + if (bytesRead > 3) { + result = DecodeResult.TOO_BIG; + return false; + } + if ((k & 0x80) != 128) { + result = DecodeResult.SUCCESS; + return false; + } + return true; + } + + void reset() { + readVarint = 0; + bytesRead = 0; + result = DecodeResult.TOO_SHORT; + } + } + + private enum DecodeResult { + SUCCESS, + TOO_SHORT, + TOO_BIG + } }