Attachment 9635 Details for Bug 40609 – milter that prevents forged from

milter that prevents forged from

no_forged_from_milter.py (text/x-python), 5.62 KB, created by Daniel Tröder on 2018-08-22 12:17:15 CEST

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Creator: Daniel Tröder

Created: 2018-08-22 12:17:15 CEST

Size: 5.62 KB

patch

obsolete

>#!/usr/bin/env python
># -*- coding: utf-8 -*-
>
>"""
>Milter that rejects mails with forged addresses in both
>	* the envelope (MAIL FROM protocol stage)
>	* the "From" header (DATA protocol stage)
>
>Legitimate email addresses are found as 'mailPrimaryAddress' and
>'mailAlternativeAddress' in LDAP.
>
>INSTALLATION:
>	1) This is intended to run on a UCS server and requires
>	univention-mail-postfix to be installed.
>	2) Install pythin-libmilter:
>	# wget https://raw.githubusercontent.com/crustymonkey/python-libmilter/master/libmilter.py \
>	-O /usr/local/lib/python2.7/site-packages/libmilter.py
>	3)Install the milter (this file):
>	# mkdir /usr/local/share/milters
>	# cp [this file] /usr/local/share/milters/
>	4) install, enable and start milter service:
>	# cp no_forged_from_milter.service /etc/systemd/system/
>	# systemctl daemon-reload
>	# systemctl enable no_forged_from_milter.service
>	# sytemctl start no_forged_from_milter.service
>	5) Check if installation worked:
>	# service no_forged_from_milter status
>	# grep no_forged_from /var/log/mail.log
>	5) Configure Postfix to use the milter:
>	# echo 'smtpd_milters = inet:localhost:5656' >> /etc/postfix/main.cf.local
>	# ucr commit /etc/postfix/main.cf
>	# service postfix restart
>
>Copyright (c) 2018 Daniel TrÃ¶der, daniel@admin-box.com
>Licensed under the MIT License (MIT)
>SPDX short identifier: MIT
>License text: https://opensource.org/licenses/MIT
>
>python-libmilter is licensed under the GPLv3 (https://www.gnu.org/licenses/gpl-3.0.en.html)
>"""
>import os
>import re
>import sys
>import signal
>import syslog
>import traceback
>
>from ldap.filter import filter_format
>import libmilter as lm
>import univention.uldap
>
>
>class NoForgedFromMilter(lm.ForkMixin, lm.MilterProtocol):
>	_lo = None
>	_ldap_secret_mtime = 0.0
>
>	def __init__(self, opts=0, protos=0):
>		lm.MilterProtocol.__init__(self, opts, protos)
>		lm.ForkMixin.__init__(self)
>		self.sasl_login_name = ''
>		self.legitimate_addresses = []
>		self.envelope_from = ''
>		self.header_from = ''
>		self.recipients = []
>
>	@classmethod
>	def log(cls, msg, level='INFO'):
>		if level == 'ERROR':
>			level = 'ERR'
>		try:
>			syslog_level = getattr(syslog, 'LOG_{}'.format(level))
>		except KeyError:
>			syslog_level = syslog.LOG_INFO
>		syslog.syslog(syslog_level, msg)
>
>	def clear_variables(self):
>		self.sasl_login_name = ''
>		self.legitimate_addresses = []
>		self.envelope_from = ''
>		self.header_from = ''
>		self.recipients = []
>
>	@classmethod
>	def get_lo(cls):
>		secret_mtime = os.stat('/etc/listfilter.secret').st_mtime
>		if not cls._lo or cls._ldap_secret_mtime < secret_mtime:
>			cls._lo = univention.uldap.getMachineConnection(
>				ldap_master=False,
>				secret_file='/etc/listfilter.secret'
>			)
>			cls._ldap_secret_mtime = os.stat('/etc/listfilter.secret').st_mtime
>		return cls._lo
>
>	@classmethod
>	def get_legitimate_addresses_for_username(cls, sasl_login_name):
>		lo = cls.get_lo()
>		ldap_attr = ['mailPrimaryAddress', 'mailAlternativeAddress']
>		ldap_filter = filter_format('(&(uid=%s)(objectclass=univentionMail))', (sasl_login_name,))
>		ldap_result = lo.search(filter=ldap_filter, attr=ldap_attr)
>		try:
>			return ldap_result[0][1]['mailPrimaryAddress'] + ldap_result[0][1].get('mailAlternativeAddress', [])
>		except IndexError:
>			cls.log('Found no email address for sasl_login_name={!r}.'.format(sasl_login_name), 'ERROR')
>			return ''
>
>	@lm.noReply
>	def connect(self, hostname, family, ip, port, cmdDict):
>		self.clear_variables()
>		return lm.CONTINUE
>
>	def mailFrom(self, frAddr, cmdDict):
>		self.envelope_from = frAddr
>		try:
>			self.sasl_login_name = cmdDict['auth_authen']
>		except KeyError:
>			# not a submission
>			pass
>		else:
>			if not self.legitimate_addresses:
>				self.legitimate_addresses = self.get_legitimate_addresses_for_username(self.sasl_login_name)
>			if self.envelope_from in self.legitimate_addresses:
>				return lm.CONTINUE
>			else:
>				self.log('REJECT: envelope_from ({}) not in legitimate addresses ({}).'.format(
>					self.envelope_from, ', '.join(self.legitimate_addresses)))
>				return lm.REJECT
>		return lm.CONTINUE
>
>	def header(self, key, val, cmdDict):
>		if self.sasl_login_name and key.lower() == 'from':
>			m = re.match(r'.*<(.+@.+\..+)>$', val)
>			if not m:
>				m = re.match(r'(.+@.+\..+)$', val)
>			if m:
>				self.header_from = m.groups()[0]
>				if not self.legitimate_addresses:
>					self.legitimate_addresses = self.get_legitimate_addresses_for_username(self.sasl_login_name)
>				if self.header_from in self.legitimate_addresses:
>					return lm.CONTINUE
>				else:
>					self.log('REJECT: {!r} in "From" header ({}) not in legitimate addresses ({!s}).'.format(
>						self.header_from, val, ', '.join(self.legitimate_addresses)))
>					return lm.REJECT
>			else:
>				self.log('Cannot parse header: {!r}: {!r}.'.format(key, val), 'ERROR')
>		return lm.CONTINUE
>
>	def eob(self, cmdDict):
>		# don't log unnecessarily
>		return lm.CONTINUE
>
>	def close(self):
>		# don't log unnecessarily
>		pass
>
>
>def run_milter():
>	syslog.openlog(ident="no_forged_from", logoption=syslog.LOG_PID, facility=syslog.LOG_MAIL)
>	NoForgedFromMilter.log('Starting NoForgedFromMilter.')
>	# test LDAP connection
>	NoForgedFromMilter.get_lo()
>
>	opts = lm.SMFIP_NOHELO | lm.SMFIP_NORCPT | lm.SMFIP_NOBODY | lm.SMFIP_NOEOH | lm.SMFIP_NODATA
>	milter_factory = lm.ForkFactory('inet:127.0.0.1:5656', NoForgedFromMilter, opts)
>
>	def sig_handler(num, frame):
>		NoForgedFromMilter.log('Stopping NoForgedFromMilter.')
>		milter_factory.close()
>		sys.exit(0)
>	signal.signal(signal.SIGINT, sig_handler)
>	signal.signal(signal.SIGTERM, sig_handler)
>
>	try:
>		milter_factory.run()
>	except Exception as exc:
>		milter_factory.close()
>		print('EXCEPTION OCCURRED: {}'.format(exc))
>		traceback.print_tb(sys.exc_traceback)
>		sys.exit(3)
>
>
>if __name__ == '__main__':
>	run_milter()

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Attachments on bug 40609: 9630 | 9631 | 9635