114 lines
4.6 KiB
Python
114 lines
4.6 KiB
Python
import time
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import sys
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import logging
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import Milter
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import re
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# Basic logger that also logs to stdout
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# TODO: Improve this a lot.
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logger = logging.getLogger(__name__)
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logger.setLevel(logging.DEBUG)
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handler = logging.StreamHandler(sys.stdout)
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handler.setLevel(logging.DEBUG)
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formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
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handler.setFormatter(formatter)
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logger.addHandler(handler)
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split_from_regex = re.compile('(?P<from_label>.*)<(?P<from_address>.*)>$')
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address_domain_regex = re.compile('.*@(?P<domain>[\.\w-]+)')
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def normalizeRawFromHeader(value):
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return value.replace('\n', '').replace('\r', '').strip()
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def parseFromHeader(value):
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"""Split 'From:'-header into label and address values."""
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match = split_from_regex.match(value)
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result = {
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'label': match.group('from_label').strip(),
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'address': match.group('from_address').strip()
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}
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result['label_domain'] = getDomainFromLabel(result['label'])
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result['address_domain'] = getDomainFromAddress(result['address'])
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return result
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def getDomainFromLabel(label):
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""" Check whether given 'From:' header label contains something that looks like an email address."""
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match = address_domain_regex.match(label)
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return match.group('domain').strip() if match is not None else None
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def getDomainFromAddress(address):
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match = address_domain_regex.match(address)
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return match.group('domain').strip() if match is not None else None
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class SuspiciousFrom(Milter.Base):
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def __init__(self):
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self.id = Milter.uniqueID()
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self.reset()
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logger.info(f"({self.id}) Instanciated.")
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def reset(self):
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self.final_result = Milter.ACCEPT
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self.new_headers = []
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def header(self, field, value):
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"""Header hook gets called for every header within the email processed."""
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if field.lower() == 'from':
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logger.debug(f"({self.id}) Got \"From:\" header raw value: '{value}'")
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value = normalizeRawFromHeader(value)
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if value == '':
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logger.info(f"Got empty from header value! WTF! Skipping.")
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return Milter.CONTINUE
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data = parseFromHeader(value)
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logger.info(f"({self.id}) Label: '{data['label']}', Address: '{data['address']}'")
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if data['label_domain'] is not None:
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logger.debug(f"({self.id}) Label '{data['label']}' contains an address with domain '{data['label_domain']}'.")
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if data['label_domain'].lower() == data['address_domain'].lower():
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logger.info(f"({self.id}) Label domain '{data['label_domain']}' matches address domain '{data['address_domain']}'. Good!")
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self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - Label domain matches address domain'})
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else:
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logger.info(f"({self.id}) Label domain '{data['label_domain']}' did NOT match address domain '{data['address_domain']}'. BAD!")
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self.new_headers.append({'name': 'X-From-Checked', 'value': 'FAIL - Label domain does NOT match address domain'})
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else:
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# Supposedly no additional address in the label, accept it for now
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# TODO: Also decode utf-8 weirdness and check in there
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logger.info(f"({self.id}) Label '{data['label']}' probably did not contain an address. Everything is fine.")
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self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - No address found in label'})
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self.final_result = Milter.ACCEPT
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# Use continue here, so we can reach eom hook.
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# TODO: Log and react if multiple From-headers are found?
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return Milter.CONTINUE
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def eom(self):
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"""EOM hook gets called at the end of message processed. Headers and final verdict are applied only here."""
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logger.info(f"({self.id}) EOM: Final verdict is {self.final_result}. New headers: {self.new_headers}")
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for new_header in self.new_headers:
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self.addheader(new_header['name'], new_header['value'])
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logger.info(f"({self.id}) EOM: Reseting self.")
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self.reset()
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return self.final_result
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def main():
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# TODO: Move this into configuration of some sort.
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milter_socket = "inet:7777@127.0.0.1"
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milter_timeout = 60
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Milter.factory = SuspiciousFrom
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logger.info(f"Starting Milter.")
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# This call blocks the main thread.
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# TODO: Improve handling CTRL+C
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Milter.runmilter("SuspiciousFromMilter", milter_socket, milter_timeout, rmsock=False)
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logger.info(f"Milter finished running.")
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if __name__ == "__main__":
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main()
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