solve.py

#!/usr/bin/env python3
import os
import sys
import time
import socket
import hashlib
import re
import random

host = "chall.ctf.bamboofox.tw"
port = 10369

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host, port))
print('connect success')

def pow_solver(prefix, difficulty):
    zeros = '0' * difficulty
    def is_valid(digest):
        if sys.version_info.major == 2:
            digest = [ord(i) for i in digest]
        bits = ''.join(bin(i)[2:].zfill(8) for i in digest)
        return bits[:difficulty] == zeros
    i = 0
    while True:
        i += 1
        s = prefix + str(i)
        if is_valid(hashlib.sha256(s.encode()).digest()):
            return i

def main():
    print('main start')
    question = s.recv(4096)
    question = question.decode('ascii')
    print(question)
    question = question[58:74]
    print(question)

    ans = pow_solver(question, 20)
    print(str(ans) + '\n')
    s.send(bytes(str(ans) + '\n', 'ascii'))
    _ = s.recv(4096)
    print(_.decode('utf-8'))
    s.send(bytes('\n', 'utf-8'))
    with open('edges.txt', 'w') as f:
        while True:
            _ = s.recv(4096)
            if len(_) == 0:
                break
            content = _.decode('ascii')
            # print(content)
            content = re.sub("[^\d\s]", "", content)
            f.write(content)

            if _.decode('ascii').find("Enter") != -1:
                break;
    os.system("./solve < edges.txt > ans.txt")
    with open("ans.txt", "r") as f:
        ans = f.readlines();
        print(ans, len(ans))
        ans = ' '.join([x.strip() for x in ans])
    print(ans)
    s.send(bytes(str(ans) + '\n', 'ascii'))

    res = s.recv(1024)
    print(res.decode('utf-8'))
    # os.system("./solve")


main()