alchemy - defcon 2017

alchemy.py

#!/usr/bin/python2
#
# alchemy - defcon 2017
#
# @_hugsy_
#
#
# The flag is: The flag is: end of the world sun clyigujheo
#

import os, base64, telnetlib
from  subprocess import *
import string, threading

DIR = "alchemy_dist"

lock = threading.Lock()
solutions = {}
T = []
N = 50

def crack(f):
    global solutions, lock
    pre = ""
    while True:
        found = False
        # for i in range(256):
        #     c = chr(i)
        for c in string.printable:
            #print("trying %s" % c.encode('hex'))
            p = Popen(["%s/%s" % (DIR,f),],
                      stdout=PIPE,
                      stdin=PIPE,
                      stderr=PIPE,
                      close_fds=True
            )

            res = p.stdout.read(11)
            p.stdin.write(pre+c + '\n')
            p.wait()


            if len(p.stderr.read(10)):
                print(pre)
                pre += c
                found = True
                break


            #print(p.returncode)

            if p.returncode == 0: return pre+c

            if p.returncode == len(pre)+1: continue

            if p.returncode < 0:  continue

            pre += c
            found = True
            break

        if not found:
            raise Exception("bye")

        lock.acquire()
        solutions[f] = pre
        lock.release()

    return pre

t = telnetlib.Telnet("cm2k-alchemy_c745e862098878b8052e1e9588c59bff.quals.shallweplayaga.me", 12004)
t.read_until('send your solution as base64, followed by a newline\n')

while True:
    h = t.read_until('\n').strip()
    print "<<< ", h
    #res = solutions[f]
    res = crack(h)
    t.write( base64.b64encode(res)  + '\n')
    print ">>> ", res