========
Tutorial
========

.. contents:: Table of Contents

Below is a set of example scripts showing some of the possible customizations
that can be done with pyftpdlib.  Some of them are included in the `demo
<https://github.com/giampaolo/pyftpdlib/blob/master/demo/>`__ directory.

A base FTP server
=================

This is probably the best starting point to understand how things work. We use
the base `DummyAuthorizer`_ for adding a bunch of virtual users, we set a limit
for `incoming connections`_ and a range of `passive ports`_. See
`demo/basic_ftpd.py`_.

.. code-block:: python

    import os

    from pyftpdlib.authorizers import DummyAuthorizer
    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer

    # Instantiate a dummy authorizer for managing 'virtual' users
    authorizer = DummyAuthorizer()

    # Define a new user having full r/w permissions and a read-only
    # anonymous user
    authorizer.add_user('user', '12345', '.', perm='elradfmwMT')
    authorizer.add_anonymous(os.getcwd())

    # Instantiate FTP handler class
    handler = FTPHandler
    handler.authorizer = authorizer

    # Define a customized banner (string returned when client connects)
    handler.banner = "pyftpdlib based FTP server ready."

    # Specify a masquerade address and the range of ports to use for
    # passive connections.  Decomment in case you're behind a NAT.
    #handler.masquerade_address = '151.25.42.11'
    #handler.passive_ports = range(60000, 65535)

    # Instantiate FTP server class and listen on all interfaces, port 2121
    address = ('', 2121)
    server = FTPServer(address, handler)

    # set a limit for connections
    server.max_cons = 256
    server.max_cons_per_ip = 5

    # start ftp server
    server.serve_forever()

Logging management
==================

pyftpdlib uses the stdlib `logging`_ module. If you don't configure logging
pyftpdlib will do it for you. In order to configure logging you should do it
*before* calling `FTPServer.serve_forever`_. Example which logs to a file:

.. code-block:: python

    import logging

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer

    authorizer = DummyAuthorizer()
    authorizer.add_user('user', '12345', '.', perm='elradfmwMT')
    handler = FTPHandler
    handler.authorizer = authorizer

    logging.basicConfig(filename='/var/log/pyftpd.log', level=logging.INFO)

    server = FTPServer(('', 2121), handler)
    server.serve_forever()

DEBUG logging
^^^^^^^^^^^^^

You may want to enable DEBUG logging to observe commands and responses
exchanged by client and server. DEBUG logging will also log internal errors
which may occur on socket related calls such as ``send()`` and ``recv()``. To
enable DEBUG logging from code use:

.. code-block:: python

    logging.basicConfig(level=logging.DEBUG)

To enable DEBUG logging from command line use:

.. code-block:: bash

    python3 -m pyftpdlib -D

DEBUG logs look like this:

::

    [I 2017-11-07 12:03:44] >>> starting FTP server on 0.0.0.0:2121, pid=22991 <<<
    [I 2017-11-07 12:03:44] concurrency model: async
    [I 2017-11-07 12:03:44] masquerade (NAT) address: None
    [I 2017-11-07 12:03:44] passive ports: None
    [D 2017-11-07 12:03:44] poller: 'pyftpdlib.ioloop.Epoll'
    [D 2017-11-07 12:03:44] authorizer: 'pyftpdlib.authorizers.DummyAuthorizer'
    [D 2017-11-07 12:03:44] use sendfile(2): True
    [D 2017-11-07 12:03:44] handler: 'pyftpdlib.handlers.FTPHandler'
    [D 2017-11-07 12:03:44] max connections: 512
    [D 2017-11-07 12:03:44] max connections per ip: unlimited
    [D 2017-11-07 12:03:44] timeout: 300
    [D 2017-11-07 12:03:44] banner: 'pyftpdlib 1.5.4 ready.'
    [D 2017-11-07 12:03:44] max login attempts: 3
    [I 2017-11-07 12:03:44] 127.0.0.1:37303-[] FTP session opened (connect)
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[] -> 220 pyftpdlib 1.0.0 ready.
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[] <- USER user
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[] -> 331 Username ok, send password.
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] <- PASS ******
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 230 Login successful.
    [I 2017-11-07 12:03:44] 127.0.0.1:37303-[user] USER 'user' logged in.
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] <- TYPE I
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 200 Type set to: Binary.
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] <- PASV
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 227 Entering passive mode (127,0,0,1,233,208).
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] <- RETR tmp-pyftpdlib
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 125 Data connection already open. Transfer starting.
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 226 Transfer complete.
    [I 2017-11-07 12:03:44] 127.0.0.1:37303-[user] RETR /home/giampaolo/IMG29312.JPG completed=1 bytes=1205012 seconds=0.003
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] <- QUIT
    [D 2017-11-07 12:03:44] 127.0.0.1:37303-[user] -> 221 Goodbye.
    [I 2017-11-07 12:03:44] 127.0.0.1:37303-[user] FTP session closed (disconnect).


Changing log line prefix
^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: python

    handler = FTPHandler
    handler.log_prefix = 'XXX [%(username)s]@%(remote_ip)s'
    server = FTPServer(('localhost', 2121), handler)
    server.serve_forever()

Logs will now look like this:

::

    [I 13-02-01 19:12:26] XXX []@127.0.0.1 FTP session opened (connect)
    [I 13-02-01 19:12:26] XXX [john]@127.0.0.1 USER 'john' logged in.


Storing passwords as hash digests
=================================

By using the default `DummyAuthorizer`_ you typically store passwords in
clear-text. A FTP server using the default dummy authorizer would typically
require a configuration file for authenticating users and their passwords, but
storing clear-text passwords is undesirable. You may want to store passwords as
hash digests into a file or a DB instead. The example below shows how to store
passwords as one-way hashes by using md5 algorithm. See `demo/md5_ftpd.py`_.

.. code-block:: python

    import os
    import hashlib

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer, AuthenticationFailed


    class DummyMD5Authorizer(DummyAuthorizer):

        def validate_authentication(self, username, password, handler):
            hash_ = hashlib.md5(password.encode('latin1')).hexdigest()
            try:
                if self.user_table[username]['pwd'] != hash_:
                    raise KeyError
            except KeyError:
                raise AuthenticationFailed


    def main():
        # get a hash digest from a clear-text password
        password = '12345'
        hash_ = hashlib.md5(password.encode('latin1')).hexdigest()
        authorizer = DummyMD5Authorizer()
        authorizer.add_user('user', hash_, os.getcwd(), perm='elradfmwMT')
        authorizer.add_anonymous(os.getcwd())
        handler = FTPHandler
        handler.authorizer = authorizer
        server = FTPServer(('', 2121), handler)
        server.serve_forever()


    if __name__ == "__main__":
        main()

UNIX FTP server
===============

If you're on UNIX you may want to configure your FTP server to include support
for "real" users existing on the system, and navigate the real filesystem. The
example below uses `UnixAuthorizer`_ and `UnixFilesystem`_ classes to do so.
See `demo/unix_ftpd.py`_.

.. code-block:: python

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import UnixAuthorizer
    from pyftpdlib.filesystems import UnixFilesystem

    def main():
        authorizer = UnixAuthorizer(rejected_users=["root"], require_valid_shell=True)
        handler = FTPHandler
        handler.authorizer = authorizer
        handler.abstracted_fs = UnixFilesystem
        server = FTPServer(('', 21), handler)
        server.serve_forever()

    if __name__ == "__main__":
        main()

Windows FTP server
==================

Same as above, but for Windows. This code requires `pywin32`_ extension to be
installed. See `demo/win_ftpd.py`_.

.. code-block:: python

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import WindowsAuthorizer

    def main():
        authorizer = WindowsAuthorizer()
        # Use Guest user with empty password to handle anonymous sessions.
        # Guest user must be enabled first, empty password set and profile
        # directory specified.
        #authorizer = WindowsAuthorizer(anonymous_user="Guest", anonymous_password="")
        handler = FTPHandler
        handler.authorizer = authorizer
        server = FTPServer(('', 2121), handler)
        server.serve_forever()

    if __name__ == "__main__":
        main()

.. _changing-the-concurrency-model:

Changing the concurrency model
==============================

By nature pyftpdlib is asynchronous. That means that it uses a single
process/thread to handle multiple client connections and file transfers. This
is why it is so fast, lightweight and scalable (see `benchmarks`_). The async
model has one big drawback though: the code cannot contain instructions that
block for a long period of time, otherwise the whole FTP server will hang. As
such, the user should avoid calls such as ``time.sleep(3)`` or heavy DB queries
at all costs.  There are cases where the async model is not appropriate, e.g.
if you're dealing with a particularly slow disk or a network filesystem. If the
calls that interact with the filesystem are slow (e.g., ``open(file,
'r').read(8192)`` takes 2 seconds to complete) then you are stuck. In such
cases you can change the concurrency model from async to multi processes or
multi threads. In practice this means that every time a client connects, a
separate thread or process is spawned, and internally it will run its own async
IO loop, which is free the block without affecting others.

Multiple threads
^^^^^^^^^^^^^^^^

.. code-block:: python

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import ThreadedFTPServer  # <-
    from pyftpdlib.authorizers import DummyAuthorizer

    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', '.')
        handler = FTPHandler
        handler.authorizer = authorizer
        server = ThreadedFTPServer(('', 2121), handler)
        server.serve_forever()

    if __name__ == "__main__":
        main()


Multiple processes
^^^^^^^^^^^^^^^^^^

.. code-block:: python

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import MultiprocessFTPServer  # <-
    from pyftpdlib.authorizers import DummyAuthorizer

    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', '.')
        handler = FTPHandler
        handler.authorizer = authorizer
        server = MultiprocessFTPServer(('', 2121), handler)
        server.serve_forever()

    if __name__ == "__main__":
        main()

It must be noted that the multi-thread approach should NOT be used with
`UnixAuthorizer`_ and `WindowsAuthorizer`_ . Reason: every time the FTP server
accesses the filesystem (e.g. for creating or renaming a file) the authorizer
will temporarily impersonate the currently logged on user by changing effective
user or group ID of the current process.

.. _pre-fork-model:

Pre fork model
^^^^^^^^^^^^^^

There is also a third option (UNIX only): the pre-fork model. Pre-fork means
that a certain number of worker processes are ``spawn()``-ed before starting
the server. Each worker process will keep using a 1-thread, async concurrency
model, handling multiple concurrent connections, but the workload is split.
This way the delay introduced by a blocking function call is amortized and
divided by the number of workers, and thus also the disk I/O latency is
minimized. Every time a new connection comes in, the parent process will
automatically delegate the connection to one of the worker processes, so from
the app standpoint this is completely transparent. As a general rule, it is
always a good idea to use this model in production. The optimal value depends
on many factors including (but not limited to) the number of CPU cores, the
number of hard disk drives that store data, and load pattern. When one is in
doubt, setting it to the number of available CPU cores would be a good start.

.. code-block:: python

    import os

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer

    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', '.')
        handler = FTPHandler
        handler.authorizer = authorizer
        server = FTPServer(('', 2121), handler)
        server.serve_forever(worker_processes=os.cpu_count())  # <-

    if __name__ == "__main__":
        main()

.. _ftps-server:

FTPS (FTP over TLS/SSL) server
==============================

pyftpdlib implements FTP over TLS, also known as FTPS, as defined in
`RFC-4217`_. This requires installing `PyOpenSSL`_ third party module.
`TLS_FTPHandler`_ class requires a ``certfile`` and a ``keyfile``. You can
generate self-signed SSL certificates like this (see also `Apache FAQs`_):

.. code-block:: sh

    $ openssl req -x509 -newkey rsa:2048 -keyout ftpd.key -out ftpd.crt -nodes
    $ ls
    ftpd.crt  ftpd.key

If you don't care about having your personal self-signed certificates you can
use the one in the demo directory which include both and is available
`here <https://github.com/giampaolo/pyftpdlib/blob/master/demo/keycert.pem>`__
(not recommended). See `demo/tls_ftpd.py`_.

.. code-block:: python

    """
    An RFC-4217 asynchronous FTPS server supporting both SSL and TLS.
    Requires PyOpenSSL module (https://pypi.org/project/pyOpenSSL).
    """

    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer
    from pyftpdlib.handlers import TLS_FTPHandler

    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', '.', perm='elradfmwMT')
        authorizer.add_anonymous('.')
        handler = TLS_FTPHandler
        handler.certfile = '/path/to/ftpd.crt'  # <--
        handler.keyfile = '/path/to/ftpd.key'  # <--
        handler.authorizer = authorizer
        # optionally require SSL for both control and data channel
        #handler.tls_control_required = True
        #handler.tls_data_required = True
        server = FTPServer(('', 21), handler)
        server.serve_forever()

    if __name__ == '__main__':
        main()

Event callbacks
===============

Here's an example which shows how to use callback methods via `FTPHandler`_
subclassing:

.. code-block:: python

    from pyftpdlib.handlers import FTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer


    class MyHandler(FTPHandler):

        def on_connect(self):
            print("%s:%s connected" % (self.remote_ip, self.remote_port))

        def on_disconnect(self):
            # do something when client disconnects
            pass

        def on_login(self, username):
            # do something when user login
            pass

        def on_logout(self, username):
            # do something when user logs out
            pass

        def on_file_sent(self, file):
            # do something when a file has been sent
            pass

        def on_file_received(self, file):
            # do something when a file has been received
            pass

        def on_incomplete_file_sent(self, file):
            # do something when a file is partially sent
            pass

        def on_incomplete_file_received(self, file):
            # remove partially uploaded files
            import os
            os.remove(file)


    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', homedir='.', perm='elradfmwMT')
        authorizer.add_anonymous(homedir='.')

        handler = MyHandler
        handler.authorizer = authorizer
        server = FTPServer(('', 2121), handler)
        server.serve_forever()

    if __name__ == "__main__":
        main()

Throttle bandwidth
==================

If desired, you can limit the transfer speed for downloads and uploads by using
the `ThrottledDTPHandler`_ class. The basic idea behind ``ThrottledDTPHandler``
is to wrap sending and receiving in a data counter, and temporary "sleep" the
data channel so that you burst to no more than X Kb/sec on average.

.. code-block:: python

    import os

    from pyftpdlib.handlers import FTPHandler, ThrottledDTPHandler
    from pyftpdlib.servers import FTPServer
    from pyftpdlib.authorizers import DummyAuthorizer

    def main():
        authorizer = DummyAuthorizer()
        authorizer.add_user('user', '12345', os.getcwd(), perm='elradfmwMT')
        authorizer.add_anonymous(os.getcwd())

        dtp_handler = ThrottledDTPHandler
        dtp_handler.read_limit = 30720  # 30 Kb/sec (30 * 1024)
        dtp_handler.write_limit = 30720  # 30 Kb/sec (30 * 1024)

        ftp_handler = FTPHandler
        ftp_handler.authorizer = authorizer
        # have the ftp handler use the alternative dtp handler class
        ftp_handler.dtp_handler = dtp_handler

        server = FTPServer(('', 2121), ftp_handler)
        server.serve_forever()

    if __name__ == '__main__':
        main()

.. _`Apache FAQs`: https://httpd.apache.org/docs/2.4/ssl/ssl_faq.html#selfcert
.. _`benchmarks`: benchmarks.html
.. _`demo/basic_ftpd.py`: https://github.com/giampaolo/pyftpdlib/blob/master/demo/basic_ftpd.py
.. _`demo/md5_ftpd.py`: https://github.com/giampaolo/pyftpdlib/blob/master/demo/md5_ftpd.py
.. _`demo/tls_ftpd.py`: https://github.com/giampaolo/pyftpdlib/blob/master/demo/tls_ftpd.py
.. _`demo/unix_ftpd.py`: https://github.com/giampaolo/pyftpdlib/blob/master/demo/unix_ftpd.py
.. _`demo/win_ftpd.py`: https://github.com/giampaolo/pyftpdlib/blob/master/demo/win_ftpd.py
.. _`DummyAuthorizer`: api.html#pyftpdlib.authorizers.DummyAuthorizer
.. _`FTPHandler`: api.html#pyftpdlib.handlers.FTPHandler
.. _`FTPServer.serve_forever`: api.html#pyftpdlib.servers.FTPServer.serve_forever
.. _`incoming connections`: api.html#pyftpdlib.servers.FTPServer.max_cons
.. _`logging`: https://docs.python.org/3/library/logging.html
.. _`passive ports`: api.html#pyftpdlib.handlers.FTPHandler.passive_ports
.. _`PyOpenSSL`: https://pypi.org/project/pyOpenSSL
.. _`pywin32`: https://pypi.org/project/pywin32/
.. _`RFC-4217`: https://www.ietf.org/rfc/rfc4217.txt
.. _`ThrottledDTPHandler`: api.html#pyftpdlib.handlers.ThrottledDTPHandler
.. _`TLS_FTPHandler`: api.html#pyftpdlib.handlers.TLS_FTPHandler
.. _`UnixAuthorizer`: api.html#pyftpdlib.authorizers.UnixAuthorizer
.. _`UnixFilesystem`: api.html#pyftpdlib.filesystems.UnixFilesystem
.. _`WindowsAuthorizer`: api.html#pyftpdlib.authorizers.WindowsAuthorizer
