# -*- coding: utf-8 -*-
"""
The :mod:`neurotic.datasets.ftpauth` module implements a
:mod:`urllib.request`-compatible FTP handler that prompts for and remembers
passwords.
.. autoclass:: FTPBasicAuthHandler
.. autofunction:: setup_ftpauth
"""
import ftplib
import urllib
from urllib.request import FTPHandler, HTTPPasswordMgr
from urllib.parse import splitport, splituser, unquote
import logging
logger = logging.getLogger(__name__)
[docs]class FTPBasicAuthHandler(FTPHandler):
"""
This subclass of :class:`urllib.request.FTPHandler` implements basic
authentication management for FTP connections. Like
:class:`urllib.request.HTTPBasicAuthHandler`, this handler for FTP connections
has a password manager that it checks for login credentials before
connecting to a server.
This subclass also ensures that file size is included in the response
header, which can fail for some FTP servers if the original
:class:`FTPHandler <urllib.request.FTPHandler>` is used.
This handler can be installed globally in a Python session so that calls
to :func:`urllib.request.urlopen('ftp://...') <urllib.request.urlopen>`
will use it automatically:
>>> handler = FTPBasicAuthHandler()
>>> handler.add_password(None, uri, user, passwd) # realm must be None
>>> opener = urllib.request.build_opener(handler)
>>> urllib.request.install_opener(opener)
"""
def __init__(self, password_mgr=None):
"""
Initialize a new FTPBasicAuthHandler.
"""
if password_mgr is None:
password_mgr = HTTPPasswordMgr()
self.passwd = password_mgr
self.add_password = self.passwd.add_password
return super().__init__()
def ftp_open(self, req):
"""
When ftp requests are made using this handler, this function gets
called at some point, and it in turn calls the ``connect_ftp`` method.
In this subclass's reimplementation of ``connect_ftp``, the FQDN of
the request's host is needed for looking up login credentials in the
password manager. However, by the time ``connect_ftp`` is called, that
information has been stripped away, and the host argument passed to
``connect_ftp`` contains only the host's IP address instead of the
FQDN. This reimplementation of ``ftp_open``, which is little more than
a copy-and-paste from the superclass's implementation, captures the
original host FQDN before it is replaced with the IP address and saves
it for later use.
This reimplementation also ensures that the file size appears in the
response header by querying for it directly. For some FTP servers the
original implementation should handle this (``retrlen`` should contain
the file size). However, for others this can fail silently due to the
server response not matching an anticipated regular expression.
"""
import sys
import email
import socket
from urllib.error import URLError
from urllib.parse import splitattr, splitpasswd, splitvalue
from urllib.response import addinfourl
####################################################
# COPIED FROM FTPHandler.ftp_open (PYTHON 3.6.6) #
# WITH JUST A FEW ADDITIONS #
####################################################
import ftplib
import mimetypes
host = req.host
if not host:
raise URLError('ftp error: no host given')
host, port = splitport(host)
if port is None:
port = ftplib.FTP_PORT
else:
port = int(port)
# username/password handling
user, host = splituser(host)
if user:
user, passwd = splitpasswd(user)
else:
passwd = None
host = unquote(host)
user = user or ''
passwd = passwd or ''
############################################
# DIFFERENT FROM FTPHandler.ftp_open
# save the host FQDN for later
self.last_req_host = host
############################################
try:
host = socket.gethostbyname(host)
except OSError as msg:
raise URLError(msg)
path, attrs = splitattr(req.selector)
dirs = path.split('/')
dirs = list(map(unquote, dirs))
dirs, file = dirs[:-1], dirs[-1]
if dirs and not dirs[0]:
dirs = dirs[1:]
try:
fw = self.connect_ftp(user, passwd, host, port, dirs, req.timeout)
type = file and 'I' or 'D'
for attr in attrs:
attr, value = splitvalue(attr)
if attr.lower() == 'type' and \
value in ('a', 'A', 'i', 'I', 'd', 'D'):
type = value.upper()
############################################
# DIFFERENT FROM FTPHandler.ftp_open
size = fw.ftp.size(file)
############################################
fp, retrlen = fw.retrfile(file, type)
headers = ""
mtype = mimetypes.guess_type(req.full_url)[0]
if mtype:
headers += "Content-type: %s\n" % mtype
if retrlen is not None and retrlen >= 0:
headers += "Content-length: %d\n" % retrlen
############################################
# DIFFERENT FROM FTPHandler.ftp_open
elif size is not None and size >= 0:
headers += "Content-length: %d\n" % size
############################################
headers = email.message_from_string(headers)
return addinfourl(fp, headers, req.full_url)
except ftplib.all_errors as exp:
exc = URLError('ftp error: %r' % exp)
raise exc.with_traceback(sys.exc_info()[2])
def connect_ftp(self, user, passwd, host, port, dirs, timeout):
"""
Unless authentication credentials are provided in the request URL
(``ftp://user:passwd@host/path``), this method will be called with
empty user and passwd arguments. In that case, this reimplementation of
``connect_ftp`` checks the password manager for credentials matching
the ``last_req_host`` (the host argument will be an IP address instead
of the FQDN and is thereby useless if the password manager is keyed by
FQDN).
"""
if not user and not passwd:
user, passwd = self.passwd.find_user_password(None, self.last_req_host)
return super().connect_ftp(user, passwd, host, port, dirs, timeout)
[docs]def setup_ftpauth():
"""
Install :class:`neurotic.datasets.ftpauth.FTPBasicAuthHandler` as the
global default FTP handler.
Note that :func:`urllib.request.install_opener` used here will remove all
other non-default handlers installed in a different opener, such as an
:class:`urllib.request.HTTPBasicAuthHandler`.
"""
handler = FTPBasicAuthHandler()
opener = urllib.request.build_opener(handler)
urllib.request.install_opener(opener)
return handler
