Bug in parsing of chunk data?

[artnaseef]

Getting this stack trace on call to MinecraftCodecHelper.readChunkSection() with data from ClientboundLevelChunkWithLightPacket.getChunkData(). The packet parse is coming from a stock, vanilla Minecraft 1.20.1 server:

java.lang.IndexOutOfBoundsException: readerIndex(36599) + length(1) exceeds writerIndex(36599): 
UnpooledHeapByteBuf(ridx: 36599, widx: 36599, cap: 36599/36599)
        at io.netty.buffer.AbstractByteBuf.checkReadableBytes0(AbstractByteBuf.java:1477)
        at io.netty.buffer.AbstractByteBuf.readByte(AbstractByteBuf.java:731)
        at com.github.steveice10.packetlib.codec.BasePacketCodecHelper.readVarInt(BasePacketCodecHelper.java:20)
        at com.github.steveice10.mc.protocol.codec.MinecraftCodecHelper.readDataPalette(MinecraftCodecHelper.java:689)
        at com.github.steveice10.mc.protocol.codec.MinecraftCodecHelper.readChunkSection(MinecraftCodecHelper.java:738)

Debugging it, the cause appears to be an attempt to read past the end of the buffer here:

https://github.com/GeyserMC/MCProtocolLib/blob/master/src/main/java/com/github/steveice10/mc/protocol/codec/MinecraftCodecHelper.java#L689

Noticed the following code is new:

// Eat up - can be seen on Hypixel as of 1.19.0
int length = this.readVarInt(buf);
for (int i = 0; i < length; i++) {
    buf.readLong();
}
storage = null;

Changing it as follows fixes my problem. Looking for advice here.

// Eat up - can be seen on Hypixel as of 1.19.0
if (buf.readableBytes() > 0) {
    int length = this.readVarInt(buf);
    for (int i = 0; i < length; i++) {
        buf.readLong();
    }
}

storage = null;

Thoughts?

[AlexProgrammerDE]

Still happening?

[artnaseef]

Honestly - not sure where this is now. I haven't looked at it in a year. This is the first feedback I've gotten.

[AlexProgrammerDE]

Recently someone has contributed some changes that fix some weird chunk behaviours. Maybe this is the same issue and it's fixed now. Or this is something else.

[artnaseef]

OK, I'll take a look. I need to try to get to the latest version of Minecraft, so this is a good time to check it out. I should be able to work on it this week.

[artnaseef]

Turned out to be a super busy week. Hoping this coming week is better.