AsyncSSH: Asynchronous SSH for Python

AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python 3.6+ asyncio framework.

import asyncio, asyncssh, sys

async def run_client():
    async with asyncssh.connect('localhost') as conn:
        result = await conn.run('echo "Hello!"', check=True)
        print(result.stdout, end='')

try:
    asyncio.get_event_loop().run_until_complete(run_client())
except (OSError, asyncssh.Error) as exc:
    sys.exit('SSH connection failed: ' + str(exc))

Check out the examples to get started!

Features

• Full support for SSHv2, SFTP, and SCP client and server functions
  • Shell, command, and subsystem channels
  • Environment variables, terminal type, and window size
  • Direct and forwarded TCP/IP channels
  • OpenSSH-compatible direct and forwarded UNIX domain socket channels
  • OpenSSH-compatible TUN/TAP channels and packet forwarding
  • Local and remote TCP/IP port forwarding
  • Local and remote UNIX domain socket forwarding
  • Dynamic TCP/IP port forwarding via SOCKS
  • X11 forwarding support on both the client and the server
  • SFTP protocol version 3 with OpenSSH extensions
    • Experimental support for SFTP versions 4-6, when requested
  • SCP protocol support, including third-party remote to remote copies
• Multiple simultaneous sessions on a single SSH connection
• Multiple SSH connections in a single event loop
• Byte and string based I/O with settable encoding
• A variety of key exchange, encryption, and MAC algorithms
  • Including post-quantum kex algorithms ML-KEM and SNTRUP
• Support for gzip compression
  • Including OpenSSH variant to delay compression until after auth
• User and host-based public key, password, and keyboard-interactive authentication methods
• Many types and formats of public keys and certificates
  • Including OpenSSH-compatible support for U2F and FIDO2 security keys
  • Including PKCS#11 support for accessing PIV security tokens
  • Including support for X.509 certificates as defined in RFC 6187
• Support for accessing keys managed by ssh-agent on UNIX systems
  • Including agent forwarding support on both the client and the server
• Support for accessing keys managed by PuTTY's Pageant agent on Windows
• Support for accessing host keys via OpenSSH's ssh-keysign
• OpenSSH-style known_hosts file support
• OpenSSH-style authorized_keys file support
• Partial support for OpenSSH-style configuration files
• Compatibility with OpenSSH "Encrypt then MAC" option for better security
• Time and byte-count based session key renegotiation
• Designed to be easy to extend to support new forms of key exchange, authentication, encryption, and compression algorithms

License

This package is released under the following terms:

Copyright (c) 2013-2024 by Ron Frederick <[email protected]> and others.

This program and the accompanying materials are made available under the terms of the Eclipse Public License v2.0 which accompanies this distribution and is available at:

http://www.eclipse.org/legal/epl-2.0/

This program may also be made available under the following secondary licenses when the conditions for such availability set forth in the Eclipse Public License v2.0 are satisfied:

GNU General Public License, Version 2.0, or any later versions of that license

SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later

For more information about this license, please see the Eclipse Public License FAQ.

Prerequisites

To use AsyncSSH 2.0 or later, you need the following:

• Python 3.6 or later
• cryptography (PyCA) 3.1 or later

Installation

Install AsyncSSH by running:

pip install asyncssh

Optional Extras

There are some optional modules you can install to enable additional functionality:

• Install bcrypt from https://pypi.python.org/pypi/bcrypt if you want support for OpenSSH private key encryption.
• Install fido2 from https://pypi.org/project/fido2 if you want support for key exchange and authentication with U2F/FIDO2 security keys.
• Install python-pkcs11 from https://pypi.org/project/python-pkcs11 if you want support for accessing PIV keys on PKCS#11 security tokens.
• Install gssapi from https://pypi.python.org/pypi/gssapi if you want support for GSSAPI key exchange and authentication on UNIX.
• Install liboqs from https://github.com/open-quantum-safe/liboqs if you want support for the OpenSSH post-quantum key exchange algorithms based on ML-KEM and SNTRUP.
• Install libsodium from https://github.com/jedisct1/libsodium and libnacl from https://pypi.python.org/pypi/libnacl if you have a version of OpenSSL older than 1.1.1b installed and you want support for Curve25519 key exchange, Ed25519 keys and certificates, or the Chacha20-Poly1305 cipher.
• Install libnettle from http://www.lysator.liu.se/~nisse/nettle/ if you want support for UMAC cryptographic hashes.
• Install pyOpenSSL from https://pypi.python.org/pypi/pyOpenSSL if you want support for X.509 certificate authentication.
• Install pywin32 from https://pypi.python.org/pypi/pywin32 if you want support for using the Pageant agent or support for GSSAPI key exchange and authentication on Windows.

AsyncSSH defines the following optional PyPI extra packages to make it easy to install any or all of these dependencies:

bcrypt

fido2

gssapi

libnacl

pkcs11

pyOpenSSL

pywin32

For example, to install bcrypt, fido2, gssapi, libnacl, pkcs11, and pyOpenSSL on UNIX, you can run:

pip install 'asyncssh[bcrypt,fido2,gssapi,libnacl,pkcs11,pyOpenSSL]'

To install bcrypt, fido2, libnacl, pkcs11, pyOpenSSL, and pywin32 on Windows, you can run:

pip install 'asyncssh[bcrypt,fido2,libnacl,pkcs11,pyOpenSSL,pywin32]'

Note that you will still need to manually install the libsodium library listed above for libnacl to work correctly and/or libnettle for UMAC support. Unfortunately, since liboqs, libsodium, and libnettle are not Python packages, they cannot be directly installed using pip.

Installing the development branch

If you would like to install the development branch of asyncssh directly from Github, you can use the following command to do this:

pip install git+https://github.com/ronf/asyncssh@develop

Mailing Lists

Three mailing lists are available for AsyncSSH:

• [email protected]: Project announcements
• [email protected]: Development discussions
• [email protected]: End-user discussions