ssh2-python
============

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

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Installation
______________

Binary wheel packages are provided for Linux, OSX and Windows, all Python versions. Wheel packages have **no dependencies**.

``pip`` may need to be updated to be able to install binary wheel packages - ``pip install -U pip``.

.. code-block:: shell

   pip install ssh2-python

For from source installation instructions, including building against system provided libssh2, `see documentation <https://ssh2-python.readthedocs.io/en/latest/installation.html#installation-from-source>`_.

For creating native system packages for Centos/RedHat, Ubuntu, Debian and Fedora, see `instructions in the documentation <http://ssh2-python.readthedocs.io/en/latest/installation.html#system-binary-packages>`_.


Who Should Use This
___________________

Developers of bespoke SSH clients.


Who Should Not Use This
_______________________

Developers looking for ready made SSH clients.

This library is not an SSH client.

Developers looking for high level easy to use clients based on this library should use `parallel-ssh <https://github.com/ParallelSSH/parallel-ssh>`_. It provides both `single <https://parallel-ssh.readthedocs.io/en/latest/native_single.html>`_ and `parallel <https://parallel-ssh.readthedocs.io/en/latest/native_parallel.html>`_ clients.

This library provides bindings to libssh2 and its API closely matches libssh2.

If the examples seem long, this is not the right library. Use `parallel-ssh <https://github.com/ParallelSSH/parallel-ssh>`_.


API Feature Set
________________

At this time all of the `libssh2`_ API has been implemented up to the libssh2 version in the repository. Please report any missing implementation.

Complete example scripts for various operations can be found in the `examples directory`_.

In addition, as ``ssh2-python`` is a thin wrapper of ``libssh2`` with Python semantics, `its code examples <https://libssh2.org/examples/>`_ can be ported straight over to Python with only minimal changes.


Library Features
----------------

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

Extension features:

* Thread safe - GIL is released as much as possible. Note that libssh2 does not support sharing sessions across threads
* Very low overhead
* Super fast as a consequence of the excellent C library it uses and prodigious use of native code
* Object oriented - memory freed automatically and safely as objects are garbage collected by Python
* Use Python semantics where applicable, such as context manager and iterator support for opening and reading from SFTP file handles
* Raise errors as Python exceptions
* Provide access to ``libssh2`` error code definitions


Quick Start
_____________

Both byte and unicode strings are accepted as arguments and encoded appropriately. To change default encoding, ``utf-8``, change the value of ``ssh2.utils.ENCODING``. Output is always in byte strings.

See `Complete Example`_ for an example including socket connect.

Please use either the issue tracker for reporting issues with code or the `mail group`_ for discussion and questions.

Contributions are most welcome!


Authentication Methods
-------------------------


Connect and get available authentication methods.


.. code-block:: python

   from __future__ import print_function

   from ssh2.session import Session

   sock = <create and connect socket>

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


Output will vary depending on SSH server configuration. For example:

.. code-block:: python

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


Agent Authentication
------------------------

.. code-block:: python

   session.agent_auth(user)


Command Execution
------------------------

.. code-block:: python

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


Reading Output
---------------

.. code-block:: python

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

.. code-block:: python

   Hello


Exit Code
--------------

.. code-block:: python

   print("Exit status: %s" % (channel.get_exit_status()))


.. code-block:: python

   Exit status: 0


Public Key Authentication
----------------------------

.. code-block:: python

   session.userauth_publickey_fromfile(
       username, 'private_key_file')


Passphrase can be provided with the ``passphrase`` keyword param - see `API documentation <https://ssh2-python.readthedocs.io/en/latest/session.html#ssh2.session.Session.userauth_publickey_fromfile>`_.


Password Authentication
----------------------------

.. code-block:: python

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

SFTP Read
-----------

.. code-block:: python

   from ssh2.sftp import LIBSSH2_FXF_READ, LIBSSH2_SFTP_S_IRUSR

   sftp = session.sftp_init()
   with sftp.open(<remote file to read>,
		  LIBSSH2_FXF_READ, LIBSSH2_SFTP_S_IRUSR) as remote_fh, \
           open(<local file to write>, 'wb') as local_fh:
       for size, data in remote_fh:
           local_fh.write(data)


Complete Example
__________________

A simple usage example looks very similar to ``libssh2`` `usage examples <https://www.libssh2.org/examples/>`_.

See `examples directory <https://github.com/ParallelSSH/ssh2-python/tree/master/examples>`_ for more complete example scripts.

As mentioned, ``ssh2-python`` is intentionally 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.

.. code-block:: python

   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 functionality
* Public key authentication and management
* SFTP operations
* SFTP file handles and attributes
* SSH port forwarding and tunnelling
* Non-blocking mode
* SCP send and receive
* Listener for port forwarding
* Subsystem support
* Host key checking and manipulation

And more, as per `libssh2`_ functionality.


Comparison with other Python SSH libraries
-------------------------------------------

Performance of above example, compared with Paramiko.

.. code-block:: shell

   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


.. _libssh2: https://www.libssh2.org
.. _Cython: https://www.cython.org
.. _`examples directory`: https://github.com/ParallelSSH/ssh2-python/tree/master/examples
.. _`mail group`: https://groups.google.com/forum/#!forum/ssh2-python
