The Count

Challenge:

Apparently DEADFACE is recruiting programmers, but spookyboi is a little apprehensive about recruiting amateurs. He's placed a password hash in the form of a flag for those able to solve his challenge. Solve the challenge and submit the flag as flag{SHA256_hash}.

Link to Thread

code.deadface.io:50000

Solution:

Connecting to the provided service produces a programming challenge:

$ nc code.deadface.io 50000

DEADFACE gatekeeper: Let us see how good your programming skills are.
If a = 0, b = 1, c = 2, etc.. Tell me what the sum of this word is:

 You have 5 seconds to give me an answer.

Your word is: wobble

This is essentially a A1Z26 Cipher, but A=0 instead of 1 (e.g BASE-26). It appeared that the provided "word" was always lowercase so we took a very simple approach of subtracting 97 from the ASCII decimal value of each character in the word (ex. ASCII character "b" = 98 decimal).

from pwn import *
context.log_level = 'critical'

r = remote('code.deadface.io', 50000)
r.recvuntil(b"\n\n")
r.recvuntil(b"\n\n")
r.recvuntil(b": ")
output = r.recvuntil(b"\n").strip(b'\n')

print(output)
numbers = [ord(letter) - 97 for letter in list(output.decode("utf-8"))]

print(numbers)

answr = sum(numbers)
print(answr)
r.sendline(str(answr))
print(r.recv().decode())

r.close()

$ python3 solve_count.py 
b'ethereal'
[4, 19, 7, 4, 17, 4, 0, 11]
66

flag{d1c037808d23acd0dc0e3b897f344571ddce4b294e742b434888b3d9f69d9944}