HackTheBox Android-in-the-Middle Writeup

Explore the basics of cybersecurity in the Android-in-the-Middle 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.

import hashlib
from Crypto.Cipher import AES
from Crypto.Util.number import long_to_bytes
from pwn import *

def encrypt(data, shared_secret):
    key = hashlib.md5(long_to_bytes(shared_secret)).digest()
    cipher = AES.new(key, AES.MODE_ECB)
    padded_data = data.ljust(16 * ((len(data) + 15) // 16), b'\0')
    return cipher.encrypt(padded_data)

def main():
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} <ip:port>")
        sys.exit(1)
    host, port = sys.argv[1].split(':')
    port = int(port)
    p = remote(host, port)
    message = b'Initialization Sequence - Code 0'
    shared_secret = 1
    encrypted_message = encrypt(message, shared_secret)
    p.sendlineafter(b'Enter The Public Key of The Memory: ', b'1') 
    p.sendlineafter(b'Enter The Encrypted Initialization Sequence: ', encrypted_message.hex().encode())
    try:
        p.recvline()
        p.recvline()
        print(p.recv().decode())
    except EOFError:
        print("Connection closed by the server.")

if __name__ == '__main__':
    main()

Summary

The Android-in-the-Middle Challenge exploits a flawed Diffie-Hellman implementation, allowing users to simplify the shared secret, encrypt the required plaintext with AES, and submit it to retrieve the flag, highlighting cryptographic analysis and exploitation skills.