http://forums.somethingawful.com/showthread.php?threadid=3803421

hack_the_puzzle_box.py

#!/usr/bin/env python3

import os

gdb_script = """
set pagination off
break check_{}
run < guessing.txt
quit
"""

result = []
for check_number_to_break in range(1, 12):
    with open('gdb_script', 'w') as fp:
        print(gdb_script.format(check_number_to_break), file=fp)
    for guess in map(chr, range(0, 256)):
        result.append(guess)
        with open('guessing.txt', 'w') as fp:
            print(''.join(result), file=fp)
        exit_status = os.system('gdb ./level2 --command=gdb_script | grep "Breakpoint 1, check_{}"'.format(check_number_to_break))
        if exit_status != 256:
            print(''.join(result))
            break
        result.pop()