Kifurushi

A simple library to forge network packets.

Why?

I was playing with the DNS protocol using the excellent scapy library. It is very simple to forge network data with this library. I have always wondered why protocol libraries like h2 or aioquic don't use it to forge packets instead of doing it all by hands and then I thought maybe it is because it will be overkill to import the whole library containing many protocol implementations just for one thing you want to use (or maybe library authors don't know the scapy library...). It would be glad to just use the scapy ability to forge packets without importing the huge protocol library. This is where the idea of kifurushi comes from.

It is a simple library that will help you forge network data quickly. It is less capable than scapy because its specific goal is to implement a concrete protocol as opposed to scapy which makes it possible to give free rein to its imagination. So if you find that your needs cannot be simply express with kifurushi, you probably need to use scapy.

Installation

with pip:

pip install kifurushi

With poetry an alternative package manager:

poetry add kifurushi

kifurushi starts working from python3.7 and also supports pypy3. It has one dependency:

• attrs: A library helping to write classes without pain.

Documentation

The documentation is available at https://kifurushi.readthedocs.io

Usage

import socket
import enum
from kifurushi import Packet, ShortField, ByteField, IntEnumField

HOST = 'disney-stuff.com'
PORT = 14006


class Mood(enum.Enum):
  happy = 1
  cool = 2
  angry = 4


class Disney(Packet):
  __fields__ = [
    ShortField('mickey', 2),
    ByteField('minnie', 3, hex=True),
    IntEnumField('donald', 1, Mood)
  ]


with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
  disney = Disney()
  s.connect((HOST, PORT))
  disney.donald = Mood.cool.value
  # we send the packet data
  s.sendall(disney.raw)
  # we create another packet object from raw bytes
  received_packet = Disney.from_bytes(s.recv(1024))
  print(received_packet)

To see more protocol implementations check the folder examples of the project.

Warnings

• If you use the excellent Pycharm editor, you may notice weird warnings when instantiating kifurushi fields. At the moment I'm writing this documentation, I'm using Pycharm 2020.3 and there is an issue when subclassing attrs classes. So just ignore the warning saying to fill the format parameter if you don't need it.
• kifurushi is a young project, so it is expected to have breaking changes in the api without respecting the semver principle. It is recommended to pin the version you are using for now.