vw_dataset_xor_calculator.py

#!/usr/bin/env python3

'''
VW XOR Calculator

How to use:

$ python3 vw_xor_calculator.py --file Car/extract/FD_7100FLASHDATA --start 0x32C --end 0x1234 --key 0xA5A5A5A5

Arguments:
--file  = dataset binary file
--start = start byte (hex)
--end   = end byte (hex)
--key   = XOR key (hex)

Processing:
- The script processes the XOR checksum in **4-byte blocks**.
- It reads the specified binary range and applies the XOR operation sequentially.
- If the last block is incomplete (less than 4 bytes), it is skipped.

Example Output:
Manual XOR result: D0C21A2E (hex) | 3502381614 (decimal)
'''

import argparse
import struct

def calculate_xor(bin_file, start, end, xor_key):
    """Calculates XOR checksum over a specified range in the binary file."""
    
    # Read the binary file
    with open(bin_file, "rb") as f:
        data = f.read()

    xor_result = xor_key

    # Process XOR in 4-byte blocks
    for i in range(start, end + 1, 4):
        block = data[i:i+4]
        if len(block) < 4:
            continue  # Skip incomplete blocks
        block_value = struct.unpack(">I", block)[0]  # Read as Big Endian
        xor_result ^= block_value  # Apply XOR operation

    print(f"Manual XOR result: {xor_result:08X} (hex) | {xor_result} (decimal)")

if __name__ == "__main__":
    # Argument parser setup
    parser = argparse.ArgumentParser(description="Calculate XOR over a specified binary range.")
    parser.add_argument("--file", type=str, required=True, help="Path to the binary file.")
    parser.add_argument("--start", type=lambda x: int(x, 16), required=True, help="Start offset (hex).")
    parser.add_argument("--end", type=lambda x: int(x, 16), required=True, help="End offset (hex).")
    parser.add_argument("--key", type=lambda x: int(x, 16), required=True, help="XOR key (hex).")

    args = parser.parse_args()

    # Run XOR calculation
    calculate_xor(args.file, args.start, args.end, args.key)