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picoCTF: Nice netcat...

picoCTF, writeup, general-skills

Info #

Problem link - picoCTF: Python Wrangling

Solution #

Let’s go straight connecting to the mercury.picoctf.net at port 49039 and see what happens.

nc mercury.picoctf.net 49039

Running the above command gives you bunch of numbers and closes the connection.

112 
105 
99 
111 
67 
.
.
.
56 
125 
10

We can easily spot that 112 is the ASCII value for p and 105 translates to i.

Now we need to convert these bunch of numbers to its char value and print it. Doing that by hand can be tedious. Let’s use python to make it swift.

At first, we need to fetch these numbers from the server and save it in a list.

import socket

TCP_IP = 'mercury.picoctf.net'
TCP_PORT = 49039

def get_data():
	s = socket.socket(socket.AF_INET, 
		socket.SOCK_STREAM)
	s.connect((TCP_IP, TCP_PORT))
	data = s.recv(1024).decode("utf-8")
	s.close()
	
	data = data.replace("\n", "").split()
	return list(map(int, data))

Now, need to convert these ASCII values to its char value.

def int_to_ascii(int_list):
	final = ""
	for i in int_list:
		final += chr(i)
	return final

The complete code will look something like this -

import socket

TCP_IP = 'mercury.picoctf.net'
TCP_PORT = 49039

def get_data():
	s = socket.socket(socket.AF_INET, 
		socket.SOCK_STREAM)
	s.connect((TCP_IP, TCP_PORT))
	data = s.recv(1024).decode("utf-8")
	s.close()
	
	data = data.replace("\n", "").split()
	return list(map(int, data))

def int_to_ascii(int_list):
	final = ""
	for i in int_list:
		final += chr(i)
	return final

# Prints the flag
print(int_to_ascii(get_data()))

Flag #

Here is the flag -

picoCTF{g00d_k1tty!_n1c3_k1tty!_3d84edc8}