crcFinder 0.0.4

A tool to find well known crc params that matches the input data and crc result (right or wrong)

CrcFinder

A tool to find well known crc params that matches the input data and crc result (right or wrong)

Install

pip install crcFinder

Usage

As Library

find zlib.crc32

from crcFinder import CrcFinder
import zlib

data = []
data.append((b"123456789", zlib.crc32(b'123456789')))
data.append((b"123456789xxxx", zlib.crc32(b'123456789xxxx')))
f = CrcFinder()
r = f.findCrc(data)
print([str(i) for i in r])

find something else

from crcFinder import CrcFinder
data = []
data.append((b"123456789\x09", b'\x11\x60\x7a\x37'))
data.append((b"1234567890\x0a", b'\xb3\x95\xcb\x46'))
f = CrcFinder()
r = f.findCrc(data)
print(r[0])

use CrcCalculator directly

from crcFinder import CrcCalculator, ShiftType
crc_pkzip = CrcCalculator(32, 0x04c11db7, 0xffffffff, True, True, 0xffffffff, ShiftType.LEFT, ShiftType.LEFT)
assert(crc_pkzip.check() == 0xcbf43926)

Solver

see tests/test_Solver.py

cli

# find crc poly and other params
python -m crcFinder find -d 616263646566,4b8e39ef
python -m crcFinder find -d 616263646566,0x4b8e39ef 313233343536373839,0xcbf43926
# calculate data crc
python -m crcFinder calculate --params "width=32 poly=0x04c11db7 init=0xffffffff refin=True refout=True xorout=0xffffffff check=0xcbf43926 name=None tableGenShiftType:ShiftType.LEFT calcShiftType:ShiftType.LEFT extra=None" -d 313233343536373839
# generate a padding to data for specified crc checksum value
python -m crcFinder solve --params "width=32 poly=0x04c11db7 init=0xffffffff refin=True refout=True xorout=0xffffffff check=0xcbf43926 name=None tableGenShiftType:ShiftType.LEFT calcShiftType:ShiftType.LEFT extra=None" --data 68656c6c6f --target 0x12345678

Reference

• https://reveng.sourceforge.io/crc-catalogue/all.htm
• https://github.com/Michaelangel007/crc32