ssh2-python 0.3.0

Python bindings for libssh2 based on Cython

Super fast SSH2 protocol library. ssh2-python provides Python bindings for libssh2.

Installation

Install libssh2 and Python header files.

Ubuntu

apt-get install libssh2-1-dev python-dev
pip install ssh2-python

RedHat

yum install libssh2-devel python-dev
pip install ssh2-python

Feature Set

Majority of the libssh2 API has been implemented. ssh2-python is a thin wrapper of libssh2 - its code examples can be ported straight over to Python with only minimal changes.

Some parts are yet to be implemented though majority of the API is complete.

Library is at the moment available as source code only. Binary releases to follow.

Examples

Both byte and unicode strings are accepted as arguments and encoded appropriately. To change default encoding change the value of ssh2.utils.ENCODING. Channel output is always byte strings.

See Complete Example for a complete example including socket connect.

Authentication Methods

Connect and get available authentication methods.

from __future__ import print_function

from ssh2.session import Session

sock = <create and connect socket>

session = Session()
session.handshake(sock)
print(session.userauth_list())

['publickey', 'password', 'keyboard-interactive']

Agent Authentication

session.agent_auth(user)

Command Execution

channel = session.open_session()
channel.execute('echo Hello')

Reading Output

size, data = channel.read()
while(size > 0):
    print(data)
    size, data = channel.read()

Hello

Exit Code

print("Exit status: {}".format(channel.get_exit_status()))

Exit status: 0

Public Key Authentication

session.userauth_publickey_fromfile(
    username, 'my_pkey.pub', 'my_pkey', '')

Where '' can be a passphrase.

Password Authentication

session.userauth_password(
    username, '<my password>')

SFTP Read

sftp = session.sftp_init()
fh = sftp.open(<file path>, 0, 0)
with open(<file to write>, 'wb') as local_fh:
    for data in fh:
        local_fh.write(data)
fh.close()

Complete Example

A simple usage example looks very similar to libssh2 usage examples.

As mentioned, ssh2-python is intentially a thin wrapper over libssh2 and directly maps most of its API.

Clients using this library can be much simpler to use than interfacing with the libssh2 API directly.

from __future__ import print_function

import os
import socket

from ssh2.session import Session

host = 'localhost'
user = os.getlogin()

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((host, 22))

session = Session()
session.handshake(sock)
session.agent_auth(user)

channel = session.open_session()
channel.execute('echo me; exit 2')
size, data = channel.read()
while size > 0:
    print(data)
    size, data = channel.read()
channel.close()
print("Exit status: %s" % channel.get_exit_status())

Output:

me

Exit status: 2

SSH Functionality currently implemented

• SSH channel operations (exec,shell,subsystem) and methods

• SSH agent

• Public key authentication and management

• SFTP open, close, read

• SSH port forwarding and tunnelling

• Non-blocking mode

• Listener for port forwarding

And more, as per libssh2 functionality.

Native Code Extension Features

The library uses Cython based native code extensions as wrappers to libssh2.

Extension features:

• Thread safe - GIL is released as much as possible

• Very low overhead

• Super fast as a consequence of the excellent C library it uses and that it uses native code prodigiously

• Object oriented - memory freed automatically and safely as objects expire

• Use Python semantics where applicable, such as iterator support for SFTP file handles

• Expose errors as Python exceptions where possible

• Provide access to libssh2 error code definitions

Comparison with other Python SSH2 libraries

Performance of above example, compared with Paramiko.

time python examples/example_echo.py
time python examples/paramiko_comparison.py

Output:

ssh2-python:

real       0m0.141s
user       0m0.037s
sys        0m0.008s

paramiko:

real       0m0.592s
user       0m0.351s
sys        0m0.021s

See examples directory for more complete example scripts.