Baby Calculator

nc 20.169.252.240 4200

A good challenge to do writeup.

mj0ln1r@AHLinux:~/babycalc$ nc 20.169.252.240 4200
Welcome to the Baby Calculator! Answer 40 questions in a minute to get the flag.
The difference between your input and the correct answer must be less than 1e-6.
[+] Question 1:
Evaluate the integral of: 4/x from 3 to 7.
> Answer: 

It was asking us to do integral of 4/x from 3 to 7, It was easy to do with scipy module of python

from scipy.integrate import quad
def compute_integral(func, lower_limit, upper_limit):
    integral, error = quad(func, lower_limit, upper_limit)
    return integral
def f(x):
    return 4/x 
compute_integral(f,3,7)

But it was difficult to answer 40 questions in a minute. So, I used pwntools to automate this process.

This is my solution script.

from math import cos, exp, pi,sin
from scipy.integrate import quad
from pwn import *

def compute_integral(func, lower_limit, upper_limit):
    integral, error = quad(func, lower_limit, upper_limit)
    return integral
def f(x):
    return eval(exp)
conn = remote('20.169.252.240',4200)
for i in range(40):
    conn.recvuntil(b'Evaluate the integral of: ')
    exp = conn.recvuntil(b' ').decode()
    r = conn.recvuntil(b'.').decode().strip('.')
    r = r.split(" ")
    ranges = [int(r[1]),int(r[3])]
    integral = compute_integral(f, ranges[0], ranges[1])
    print(integral)
    conn.recv()
    conn.sendline(str(integral).encode())
    if i == 39:
        print(conn.recv())

# cvctf{B4by_m@7h_G14n7_5t3P}

Flag : cvctf{B4by_m@7h_G14n7_5t3P}

Original Writeup