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pymilter-suspicious-from
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Code Issues Releases Wiki Activity

Use builtin python tools to do address/header parsing

This commit is contained in:
Jan Philipp Timme 2019-12-19 11:34:18 +01:00
parent e343be1862
commit 358ec62af6
1 changed files with 37 additions and 41 deletions
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72
main.py
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@ -6,6 +6,10 @@ import Milter
import re
from email.header import decode_header
from email.utils import getaddresses
# Basic logger that also logs to stdout
# TODO: Improve this a lot.
logger = logging.getLogger(__name__)
@ -18,36 +22,27 @@ handler.setFormatter(formatter)
logger.addHandler(handler)
split_from_regex = re.compile('(?P<from_label>.*)<(?P<from_address>.*)>$')
address_domain_regex = re.compile('.*@(?P<domain>[\.\w-]+)')
def get_decoded_header(value):
decoded_header_items = decode_header(value)
decoded_header_value = ''
for item in decoded_header_items:
decoded_item = item[0].decode(item[1]) if item[1] is not None else item[0]
if isinstance(decoded_item, bytes):
decoded_item = decoded_item.decode('ascii')
decoded_header_value += decoded_item
return getaddresses([decoded_header_value])[0]
def normalizeRawFromHeader(value):
return value.replace('\n', '').replace('\r', '').strip()
def parseFromHeader(value):
"""Split 'From:'-header into label and address values."""
match = split_from_regex.match(value)
if match is None:
return None
result = {
'label': match.group('from_label').strip(),
'address': match.group('from_address').strip()
}
result['label_domain'] = getDomainFromLabel(result['label'])
result['address_domain'] = getDomainFromAddress(result['address'])
return result
def getDomainFromLabel(label):
def getDomainFromValue(value):
""" Check whether given 'From:' header label contains something that looks like an email address."""
match = address_domain_regex.match(label)
return match.group('domain').strip() if match is not None else None
def getDomainFromAddress(address):
match = address_domain_regex.match(address)
match = address_domain_regex.match(value)
return match.group('domain').strip() if match is not None else None
@ -67,27 +62,28 @@ class SuspiciousFrom(Milter.Base):
logger.debug(f"({self.id}) Got \"From:\" header raw value: '{value}'")
value = normalizeRawFromHeader(value)
if value == '':
logger.info(f"Got empty from header value! WTF! Skipping.")
logger.warn(f"Got empty from header value! WTF! Skipping.")
return Milter.CONTINUE
data = parseFromHeader(value)
if data is None:
logger.info(f"Failed to parse given from header value! Skipping.")
return Milter.CONTINUE
logger.info(f"({self.id}) Label: '{data['label']}', Address: '{data['address']}'")
if data['label_domain'] is not None:
logger.debug(f"({self.id}) Label '{data['label']}' contains an address with domain '{data['label_domain']}'.")
if data['label_domain'].lower() == data['address_domain'].lower():
logger.info(f"({self.id}) Label domain '{data['label_domain']}' matches address domain '{data['address_domain']}'. Good!")
data = get_decoded_header(value)
logger.info(f"({self.id}) Label: '{data[0]}', Address: '{data[1]}'")
if data[0] == '':
logger.info(f"({self.id}) No label in from header, OK!")
self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - No label specified'})
else:
label_domain = getDomainFromValue(data[0])
address_domain = getDomainFromValue(data[1])
logger.info(f"({self.id})Extracted label_domain '{label_domain}' and address_domain '{address_domain}'")
if label_domain is not None:
logger.debug(f"({self.id}) Label '{data[0]}' contains an address with domain '{label_domain}'.")
if label_domain.lower() == address_domain.lower():
logger.info(f"({self.id}) Label domain '{label_domain}' matches address domain '{address_domain}'. Good!")
self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - Label domain matches address domain'})
else:
logger.info(f"({self.id}) Label domain '{data['label_domain']}' did NOT match address domain '{data['address_domain']}'. BAD!")
logger.info(f"({self.id}) Label domain '{label_domain}' did NOT match address domain '{address_domain}'. BAD!")
self.new_headers.append({'name': 'X-From-Checked', 'value': 'FAIL - Label domain does NOT match address domain'})
else:
# Supposedly no additional address in the label, accept it for now
# TODO: Also decode utf-8 weirdness and check in there
logger.info(f"({self.id}) Label '{data['label']}' probably did not contain an address. Everything is fine.")
self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - No address found in label'})
self.final_result = Milter.ACCEPT
logger.info(f"({self.id}) No domain found in label. Good!")
self.new_headers.append({'name': 'X-From-Checked', 'value': 'OK - No domain found in label.'})
# Use continue here, so we can reach eom hook.
# TODO: Log and react if multiple From-headers are found?
return Milter.CONTINUE