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TarPyt: a Python ssh/http/smtp/etc. tarpit

TarPyt takes its inspiration from Endlessh: an SSH Tarpit. Specifically, the very last section about using Python's asyncio libtrary. There are two projects I can see like this one:

Both of them probably do a better job than me explaining the specifics of the problem, so I encourage you to read the blog post and the README's of those other projects.

!! WARNING !!

By design, this program will wait on an open port on your system and unconditionally accept random connections from anywhere on the internet. This is done without encryption, authorization, or authentication. Obviously, this is dangerous in almost all circumstances; especially if you don't know what you're doing! The design goals below go over the protections in place that make this "safe" to use, but make no mistake: this is a risk. You must accept that risk before running TarPyt! You have officially been warned.

Design Goals

This program is extremely opinionated in its design, extra features outside of the following goals will not be added.

  1. This program is designed to be run as a highly sandboxed systemd socket-activated service. This is because systemd will handle resource control, namespacing, privilege dropping, and most importantly binding to any port without running as root or using capabilities. TarPyt will merely accept a socket at instantiation, and use that socket for its entire lifetime. It does not handle anything beyond merely receiving this socket and being used as a tarpit.
  2. This program is written for Python >=3.11 and only uses the standard library. This allows for easy portability and installation on any system that runs systemd and Python, which should cover the vast majority of Linux installations. Older versions of Python will not work.
  3. Python is used for its easy of development and quick auditing, but typing will be strictly enforced. The combination of systemd sandboxing, Python's memory safety as an interpreted language, and typing makes TarPyt (in theory) very safe as a tarpit.

The supported platforms are exclusively any not-so-old Linux distribution that uses systemd >=247 and Python >=3.11.

Requirements

Building (configuring and installing) is done with meson. A version >= 1.1.0 is required.

For testing, a couple of other utils are needed:

  • curl: for HTTP testing
  • openssh: client only, for SSH testing

For runtime:

  • systemd >=247: as well as libsystemd.so which should be present on any system running systemd
  • Python >= 3.11: The standard library is all that is required

Building & Installing

Using meson:

meson setup --prefix="$prefix" "$builddir"
meson install -C "$buildtir"

Testing

Tests can be enabled with:

meson setup "$builddir" -Denable_tests=true

Which is on by default. Afterwards tests can be run with:

meson test -C "$builddir"

The tests are not very sophisticated and just make sure each protocol is stalled after 10 seconds.

Usage

TarPyt is supposed to be exclusively used as a systemd socket-activated service. To run an ssh tarpit you would do

systemctl enable --now [email protected]

To run an http tarpit you would do

systemctl enable --now [email protected]

Obviously, your filewall needs to have these ports open, or no connections will be received.

Configuration

Because systemd is handling the socket, there is very little to configure at this time. Though specific timeouts could be configured per connection type and per port.

License

TarPyt is licensed under the terms of the GNU Public License v3 (or Later) (GPLv3+). See LICENSE for more information.