English [Internetwache CTF 2016] [Code 50 – A numbers game] Write Up

Description

A numbers game
(code50, solved by 406)

Description: People either love or hate math. Do you love it? Prove it! You just need to solve a bunch of equations without a mistake.

Service: 188.166.133.53:11027

Resolution

When we connect to the service we get the following:

laxa:Challenges:18:03:38$ nc 188.166.133.53 11027
Hi, I heard that you're good in math. Prove it!
Level 1.: x - 2 = 6

So we make the following script:

#!/usr/bin/python

import telnetlib

t = telnetlib.Telnet("188.166.133.53", 11027)
print t.read_until('\n'),

while True:
    a = t.read_until('\n')
    print a,
    data = a.split(' ')
    a = int(data[4])
    b = int(data[6].strip())
    if data[3] == '-':
        res = a + b
    elif data[3] == '+':
        res = b - a
    elif data[3] == '*':
        res = b / a
    elif data[3] == '/':
        res = b * a
    print res
    t.write(str(res) + '\n')
    a = t.read_until('\n')
    print a,

After solving 100 equations we get the flag:
IW{M4TH_1S_34SY}

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