math master [misc]

Python scripting development to calculate 100 math questions within 3 seconds each.

Challenge Description

Test your mathematical skills in this rapid-fire math challenge! Solve 100 math problems involving minimum, mode, maximum, average, and median calculations within 3 seconds for each question. Do you have what it takes to be a Math Master?

nc math.sibersiaga2023.myctf.io 8887

Flag format: sibersiaga{strings}

41.67 points, 12 solves

Connect the instance.

nc math.sibersiaga2023.myctf.io 8887

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Hi Cyber Troopers!
I made a math question generator and I would like you to solve every math question within 3 seconds with a total of 100. I will give you the flag when you are done.
Find: Min from [23, 45, 123, 1, 654, 700, 4]
<input>
<repeat your input>
Wrong answer.

Observation

The challenge aims to test your custom script development. When you connect to the instance, it will print out the banner together with the math question one at a time after you have solved it. The challenge description indicates the syllabus of the math questions (min, max, mod, average, and median). The flag will be printed out when your solve count equals 100.

To solve this kind of challenge, 3 requirements need to be met.

1. You must understand how to use pwntools. (It is by far the easiest tool to solve it.)
2. You must understand Python. :D
3. You must know how to deal with data types. (e.g., b'3', '3', and 3 are three different data types over here.)

Solution

Here is my shamless solve.py script.

#!/usr/bin/env python3
from pwn import *

def math_func(ques):
	li = [] # Always clear the list every time the function gets called.

	if "Min from " in ques:
		element = ques[10:-1]
		elements = list(element.split(', '))
		for num in elements:
			li.append(int(num))
		li.sort()
		return li[0] # Return first element.
			
	if "Max from " in ques:
		element = ques[10:-1]
		elements = list(element.split(', '))
		for num in elements:
			li.append(int(num))
		li.sort()
		return li[-1] # Return last element

	if "Median of " in ques:
		element = ques[11:-1]
		elements = list(element.split(', '))
		for num in elements:
			li.append(int(num))
		li.sort()
		if len(li) % 2 != 0:
			ans = li[len(li)//2]
		else:
			ans = (li[len(li)//2 - 1] + li[len(li)//2]) / 2 # Median calculation.
		return ans

	if "Average of " in ques:
		element = ques[12:-1]
		elements = list(element.split(', '))
		total = 0
		for num in elements:
			total += int(num)
		return total/len(elements) # Average calculation.

	if "mod" in ques:
		element = ques[1:-1]
		elements = list(element.split(' mod '))
		ans = int(elements[0]) % int(elements[1]) # Modulus calculation.
		return ans

s = remote('math.sibersiaga2023.myctf.io', 8887)
count = 0

while count != 100:
	s.recvuntil(b':')
	ques = s.recvline().decode().strip().replace('\r\n', '') # Math question.

	ans = math_func(ques)
	s.sendline(str(ans).encode())
	s.recvline() # Repeat the line we sent.
	s.recvline() # b'Correct! Next Question.'
	count += 1

print(s.recvline().decode().strip())
print(s.recvline().decode().strip())
s.close()

Output:

[x] Opening connection to math.sibersiaga2023.myctf.io on port 8887
[x] Opening connection to math.sibersiaga2023.myctf.io on port 8887: Trying 128.199.224.232
[+] Opening connection to math.sibersiaga2023.myctf.io on port 8887: Done
Congratulations! You are fast enough!
The flag is sibersiaga{7h1nk_f4573r_cyb3r_7hr00p3r5}
[*] Closed connection to math.sibersiaga2023.myctf.io port 8887

FLAG: sibersiaga{7h1nk_f4573r_cyb3r_7hr00p3r5}