Analyse Minecraft Wireshark YAML TCP stream dumps using pyCraft

parse.py

#!/usr/bin/env python

from __future__ import print_function

import sys
import os
import re
import io
import base64
import zlib

import yaml as y

from minecraft import SUPPORTED_PROTOCOL_VERSIONS
from minecraft.networking import types, packets, connection
from minecraft.networking.packets import clientbound, serverbound


CLIENT, SERVER = 0, 1
HANDSHAKE, STATUS, LOGIN, PLAY = 0, 1, 2, 3
PEER_RE = re.compile(r'peer(\d+)_(\d+)$')

def parse_file(file):
    events = y.parse(file, y.SafeLoader)
    for etype in y.StreamStartEvent, y.DocumentStartEvent, y.MappingStartEvent:
        event = next(events)
        assert isinstance(event, etype), 'not isinstance(%r, %r)' % (event, etype)

    streams = {CLIENT: io.BytesIO(), SERVER: io.BytesIO()}
    counts = {CLIENT: 0, SERVER: 0}

    context = connection.ConnectionContext(
        protocol_version=max(SUPPORTED_PROTOCOL_VERSIONS))
    compression = False
    state = HANDSHAKE
    packet_map = get_packets(context)

    for event1 in events:
        assert isinstance(event1, y.ScalarEvent), \
               'not isinstance(%r, y.ScalarEvent)' % event1
        peer, index = map(int, PEER_RE.match(event1.value).groups())
        assert counts[peer] == index, \
               'counts[%r] == %r != %r' % (peer, counts[peer], index)
        counts[peer] += 1       

        event2 = next(events)
        assert isinstance(event2, y.ScalarEvent), \
               'not isinstance(%r, y.ScalarEvent)' % event2
        assert event2.tag == 'tag:yaml.org,2002:binary'

        streams[peer].seek(len(streams[peer].getbuffer()))
        streams[peer].write(base64.b64decode(event2.value))
        streams[peer].seek(0)

        try:
            while True:
                for packet in read_packet(
                    stream = streams[peer],
                    compression = compression,
                    packet_map = packet_map[peer][state],
                    context = context
                ):
                    if packet is None: break
                    streams[peer] = io.BytesIO(streams[peer].read())
    
                    if isinstance(packet, serverbound.handshake.HandShakePacket):
                        assert state == HANDSHAKE
                        context.protocol_version = packet.protocol_version
                        packet_map = get_packets(context)
                        state = packet.next_state
                    elif isinstance(packet, clientbound.login.LoginSuccessPacket):
                        assert state == LOGIN
                        state = PLAY
                    elif packet.packet_name == 'set compression':
                        assert state in (LOGIN, PLAY)
                        compression = packet.threshold > 0
    
                    print('%s %s' % ('<--' if peer == CLIENT else '-->', packet))
    
                if packet is None: break
        except:
            print('<--' if peer == CLIENT else '-->', end=' ***Exception:\n')
            raise

    unused = { p: s.read() for (p, s) in stream }
    if any(len(s) > 0 for s in unused.values()):
        print('Unused data at end of stream: %r' % unused)

def read_packet(stream, compression, packet_map, context):
    try:
        for buffer in read_packet_buffer(stream, compression):
            if buffer is not None: break
            yield None
    except zlib.error as e:
        print('*** Exception: %s' % e)
        packet = packets.Packet(context)
    else:
        packet_id = next(read_varint(buffer))
        assert packet_id is not None
        if packet_id in packet_map:
            packet = packet_map[packet_id](context)
            packet.read(buffer)
        else:
            packet = packets.Packet(context, id=packet_id)
    yield packet

def read_packet_buffer(stream, compression):
    for length in read_varint(stream):
        if length is not None: break
        yield None
    buffer = packets.PacketBuffer()
    while True:
        buffer.send(stream.read(length - len(buffer.get_writable())))
        if len(buffer.get_writable()) >= length: break
        yield None
    assert len(buffer.get_writable()) == length
    buffer.reset_cursor()
    if compression:
        data_length = next(read_varint(buffer))
        assert data_length is not None
        if data_length > 0:
            data = zlib.decompress(buffer.read())
            assert len(data) == data_length
            buffer.reset()
            buffer.send(data)
            buffer.reset_cursor()
    yield buffer

def read_varint(stream):
    value = 0
    for n in range(5):
        while True:
            byte = stream.read(1)
            if len(byte) > 0: break
            yield None
        value |= (byte[0] & 0x7F) << 7*n
        if byte[0] & 0x80 == 0: break
    else:
        raise Exception('VarInt overflow.')
    yield value

def get_packets(context):
    return {bk: {sk: {p.get_id(context): p for p in sm.get_packets(context)}
                 for (sk,sm) in ((HANDSHAKE, bm.handshake),
                                 (LOGIN,     bm.login),
                                 (STATUS,    bm.status),
                                 (PLAY,      bm.play))}
            for (bk,bm) in ((CLIENT,serverbound), (SERVER,clientbound))}

def main(*args):
    if not args:
        parse_file(sys.stdin)
    for arg in args:
        print('%s:' % arg)
        with open(arg) as file:
            parse_file(file)

if __name__ == '__main__':
    main(*sys.argv[1:])