kurogai level 1.0

Overview

There are two github repositories that have inspired me to start doing these projects: kurogai’s 100-red-team-projects and kurogai’s 100-mitre-attack-projects. These repositories may look really similar, but they both contain different projects. The 100-red-team-projects seem to be aimed at students, while the 100-mitre-attack-projects seem to be aimed at both students and professionals.

Level 1.0

Task

TCP or UDP server just to receive messages.

• no client required
• just the server to receive TCP or UDP messages

Solutions

TCP Server

import socket

host = '127.0.0.1'
port = 58202 # arbitrary. pick the port you want
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind((host,port)) # pass in tuple with ip and port
sock.listen() # listen for incoming TCP connections
# wait...
connection, address = sock.accept()
message = b''
try:
	while True:
		data = connection.recv(1024)
		if len(data) < 1024: # kind of computationally inefficient... but whatever
			print(f'should be the last packet')
		message += data # handle partial receipts (i.e., len(data) < 1024)
		if not data:
			break # check if no data was sent. not data == b''
except Exception as e:
	print(f"error occured. socket closed.\n{e}")
finally:
	connection.close()

print(f"final message was {len(message)} bytes in length")
to = open('message.txt', 'wb')
to.write(message) # could do better. but this works
to.close()

Couple of things to note in this line:

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

• socket.SOCK_STREAM
  • We specify that we are creating a stream socket because TCP is a stream protocol. This means that data is sent in a byte stream
• socket.AF_INET
  • According to the documentation for socket, AF_INET specifies that the following arguments are necessary:
    • a IPv4 address or domain name will be used to identify the host as a string
    • a port number as an integer

UDP Server

With a few simple modifications, we can convert the TCP server to a UDP server

import socket

host = '127.0.0.1'
port = 58203

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
# UDP (User Datagram Protocol), therefore: socket.SOCK_DGRAM
sock.bind((host, port))

message = b''
try:
	while True:
		data, address = sock.recvfrom(1024)
		message += data
		if not data:
			break
except Exception as e:
	print(f"Exception occured. Socket closed.\n{e}")
finally:
	sock.close()

to = open('message.txt', 'wb')
to.write(message)
to.close()