Allow rough configuration to take place

README.md

+# pymilter-suspicious-from
+
+This is a very rough python milter implementation which is supposed to parse `From:` header values and mark suspicious ones.
+
+```
+From: "Totally Official <totally.official@example.com>" <nope-its-fake@fake.example.net>
+```
+

config.py

+import logging
+
+log_level = logging.INFO
+milter_socket = "inet:7777@127.0.0.1"
+milter_timeout = 60

main.py

-import time
 import sys
 import logging
 
 import Milter
 
-import re
-
 from email.header import decode_header
 from email.utils import getaddresses
 
+import re
+
+import config
 
 # Basic logger that also logs to stdout
 # TODO: Improve this a lot.
 logger = logging.getLogger(__name__)
-logger.setLevel(logging.DEBUG)
+logger.setLevel(config.log_level)
 
 handler = logging.StreamHandler(sys.stdout)
-handler.setLevel(logging.DEBUG)
+handler.setLevel(config.log_level)
 formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
 handler.setFormatter(formatter)
 
 logger.addHandler(handler)
 
+# Rough regex to fetch domain values from address-like text
 address_domain_regex = re.compile('.*@(?P<domain>[\.\w-]+)')
 
 
 def get_decoded_header(value):
+    """Use python builtins to decode from header properly."""
     decoded_header_items = decode_header(value)
     decoded_header_value = ''
     for item in decoded_header_items:
@@ -37,6 +39,7 @@ def get_decoded_header(value):
 
 
 def normalizeRawFromHeader(value):
+    """Clean up linebreaks and spaces that are not needed."""
     return value.replace('\n', '').replace('\r', '').strip()
 
 
@@ -53,6 +56,8 @@ class SuspiciousFrom(Milter.Base):
         logger.debug(f"({self.id}) Instanciated.")
 
     def reset(self):
+        """It looks like one milter instance can reach eom hook multiple times.
+           This allows to re-use an instance in a more clean way."""
         self.final_result = Milter.ACCEPT
         self.new_headers = []
 
@@ -69,6 +74,7 @@ class SuspiciousFrom(Milter.Base):
             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'})
+                self.new_headers.append({'name': 'X-From-Suspicious', 'value': 'NO'})
             else:
                 label_domain = getDomainFromValue(data[0])
                 address_domain = getDomainFromValue(data[1])
@@ -78,12 +84,15 @@ class SuspiciousFrom(Milter.Base):
                     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'})
+                        self.new_headers.append({'name': 'X-From-Suspicious', 'value': 'NO'})
                     else:
                         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'})
+                        self.new_headers.append({'name': 'X-From-Suspicious', 'value': 'YES'})
                 else:
                     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.'})
+                    self.new_headers.append({'name': 'X-From-Suspicious', 'value': 'NO'})
         # Use continue here, so we can reach eom hook.
         # TODO: Log and react if multiple From-headers are found?
         return Milter.CONTINUE
@@ -100,13 +109,11 @@ class SuspiciousFrom(Milter.Base):
 
 def main():
     # TODO: Move this into configuration of some sort.
-    milter_socket = "inet:7777@127.0.0.1"
-    milter_timeout = 60
     Milter.factory = SuspiciousFrom
     logger.info(f"Starting Milter.")
     # This call blocks the main thread.
     # TODO: Improve handling CTRL+C
-    Milter.runmilter("SuspiciousFromMilter", milter_socket, milter_timeout, rmsock=False)
+    Milter.runmilter("SuspiciousFromMilter", config.milter_socket, config.milter_timeout, rmsock=False)
     logger.info(f"Milter finished running.")