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import socket
import time
from hashlib import *
from thread import *
from Crypto.Util.number import *
from os import urandom
from random import *
from string import *
from secret import password, flag
_port = int(sys.argv[1])
_timeout = 3
_host = ''
_bufsize = 4096
_logfile = open(str(sys.argv[0]) + '.log', 'a')
_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
_socket.bind((_host, _port))
_socket.listen(_bufsize)
_taskname = 'SRPP'
_hash = 'sha512'
def Hash(*args):
a = ':'.join(str(a) for a in args)
return int(sha256(a).hexdigest(), 16)
def getParams(nbit):
N = getPrime(nbit)
g = 2
k = Hash(N, g)
return(N, g, k)
def clientThread(client):
client.send('Bot detection: Are you ready?' + '\n')
A = ''.join([choice(printable[:62]) for x in range(26)])
print A[:4]
msg = 'ASIS needs proof of work to start the ' + _taskname + ' challenge.\n' + _hash.upper() + '(X + "%s").hexdigest() = "%s...",\nX is an alphanumeric string and |X| = 4\nEnter X: ' % (A[4:], sha512(A).hexdigest()[:32])
client.send(msg)
X = client.recv(_bufsize).strip()
if sha256(X + A[4:]).hexdigest() == sha256(A).hexdigest():
client.settimeout(_timeout)
client.send('Good work, Let\'s Go!' + '\n')
nbit = 1024
params = getParams(nbit)
N, g, k = params
email = 'admin@asis-ctf.ir'
client.send('Please login as "admin@asis-ctf.ir" and get the flag:' + '\n')
client.send('Sever is generating the parameters ...' + '\n')
client.send('params = (N, g, k) = ' + str(params) + '\n')
salt = urandom(32)
N, g, _ = params
x = Hash(salt, email, password)
verifier = pow(g, x, N)
while True:
try:
client.send('Send the email address and the public random positive value A seperated by "," as "email, A": ' + '\n')
ans = client.recv(_bufsize).strip()
print ans
try:
email, A = ans.split(',')
A = int(A)
assert (A != 0 and A != N), client.send('Are you kidding me?! :P' + '\n')
assert email == 'admin@asis-ctf.ir', client.send('You should login as admin@asis-ctf.ir' + '\n')
b = getRandomRange(1, N)
B = (k * verifier + pow(g, b, N)) % N
client.send('(salt, public_ephemeral) = (%s, %d) \n' % (salt.encode('base64')[:-1], B))
print gmpy.invert(B)
u = Hash(A, B)
client.send('Send the session key: ' + '\n')
K_client = client.recv(_bufsize).strip()
assert K_client.isdigit(), client.send('Please send a valid positive integer as session key.' + '\n')
K_client = int(K_client)
S_s = pow(A * pow(verifier, u, N), b, N)
K_server = Hash(S_s)
client.send('Send a POC of session key: ' + '\n')
M_client = client.recv(_bufsize).strip()
assert M_client.isdigit(), client.send('Please send valid positive integer as POC.' + '\n')
M_client = int(M_client)
assert (K_server == K_client), client.send('The session key is not correct!' + '\n')
assert (M_client == Hash(Hash(N) ^ Hash(g), Hash(email), salt, A, B, K_client)), client.send('The POC is not correct!' + '\n')
M_server = Hash(A, M_client, K_server)
client.send('Great, you got the flag: ' + flag + '\n')
client.close()
break
except:
client.send('Provided input is not valid.' + '\n')
client.send('Quiting ...' + '\n')
client.close()
break
except socket.timeout:
client.send('Timeout! Plase send faster ... \n')
client.close()
break
else:
client.send('Sorry, Bad proof of work! \n')
client.close()
while True:
client, addr = _socket.accept()
start_new_thread(clientThread ,(client,))
s.close()
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