PoC masterdata unpacker/repacker for Yohane the Parhelion - NUMAZU in the MIRAGE

masterdata_repack.py

import msgpack
import glob
import json
import pathlib

out_file = open('masterdata_repacked', 'wb')
jsons = [pathlib.Path(i) for i in glob.glob("unpacked/*.json")]
header = {}
buf = bytearray()

i = 0
for json_path in jsons:
    name = json_path.stem
    with open(json_path, 'r') as f:
        data = msgpack.packb(json.load(f))
        size = len(data)
        header[name] = [i, size]
        i += size
        buf += data

out_file.write(msgpack.packb(header))
out_file.write(buf)

masterdata_unpack.py

import lz4.block
import msgpack
import json
import os


def unlz4_hook(code, data):
    if code == 99:
        size = int.from_bytes(data[1:5], 'big')
        return msgpack.unpackb(lz4.block.decompress(data[5:], size))
    return msgpack.ExtType(code, data)


with open('masterdata', 'rb') as f:
    unpacker = msgpack.Unpacker(f, ext_hook=unlz4_hook)
    info = unpacker.unpack()

    os.makedirs('unpacked', exist_ok=True)
    for name, (offset, size) in info.items():
        with open(f'unpacked/{name}.json', 'w') as g:
            data = unpacker.read_bytes(size)
            json.dump(msgpack.unpackb(data, ext_hook=unlz4_hook), g)