CPEN442 Assignment4 Q4c

patch_q4.py

from hashlib import sha1

import click  # pip install click


@click.command()
@click.option('-i', '--input-program', required=True,
              help="Path to 12563110.program2.exe", type=click.Path())
@click.option('-o', '--output-program', required=True,
              help="Path to new 12563110.program2.exe to write",
              type=click.Path())
@click.password_option()
def main(input_program, output_program, password):
    np_hash = sha1(password).digest()
    # In [31]: s.find('\x30\xa7\xf7\xbd')
    # Out[31]: 75795
    OFFSET = 75795

    # Read whole program into memory as a bytearray and patch the hash
    with open(input_program, "r+b") as f:
        program = bytearray(f.read())
    for i, byte in enumerate(np_hash):
        program[OFFSET+i] = byte

    # Write the patched program to the output path
    with open(output_program, "w+b") as f:
        f.write(program)


if __name__ == '__main__':
    main()