Greylisting

Milter/greylist.py

@@ -0,0 +1,73 @@
+import time
+import shelve
+import thread
+import logging
+import urllib
+
+log = logging.getLogger('milter.greylist')
+
+def quoteAddress(s):
+  '''Quote an address so that it's safe to store in the file-system.
+  Address can either be a domain name, or local part.
+  Returns the quoted address.'''
+
+  s = urllib.quote(s, '@_-+~!.%')
+  if s.startswith('.'): s = '%2e' + s[1:]
+  return s
+
+class Record(object):
+  __slots__ = ( 'firstseen', 'lastseen', 'umis', 'cnt' )
+
+  def __init__(self):
+    now = time.time()
+    self.firstseen = now
+    self.lastseen = now
+    self.cnt = 0
+    self.umis = None
+
+class Greylist(object):
+
+  def __init__(self,dbname,grey_time=10,grey_expire=4,grey_retain=36):
+    self.ignoreLastByte = False
+    self.greylist_time = grey_time * 60         # minutes
+    self.greylist_expire = grey_expire * 3600   # hours
+    self.greylist_retain = grey_retain * 24 * 3600   # days
+    self.dbp = shelve.open(dbname,'c',protocol=2)
+    self.lock = thread.allocate_lock()
+  
+  def check(self,ip,sender,recipient):
+    "Return number of allowed messages for greylist triple."
+    sender = quoteAddress(sender)
+    recipient = quoteAddress(recipient)
+    key = ip + ':' + sender + ':' + recipient
+    self.lock.acquire()
+    try:
+      dbp = self.dbp
+      try:
+        r = dbp[key]
+        now = time.time()
+        if now > r.lastseen + self.greylist_retain:
+          # expired
+          log.debug('Expired greylist: %s',key)
+          r = Record()
+        elif now < r.firstseen + self.greylist_time:
+          # still greylisted
+          log.debug('Reset greylist: %s',key)
+          r = Record()
+        elif r.cnt or now < r.firstseen + self.greylist_expire:
+          # in greylist window or active
+          r.lastseen = now
+          r.cnt += 1
+          log.debug('Active greylist(%d): %s',r.cnt,key)
+        else:
+          # passed greylist window
+          log.debug('Late greylist: %s',key)
+          r = Record()
+        dbp[key] = r
+      except:
+        r = Record()
+        dbp[key] = r
+      dbp.sync()
+    finally:
+      self.lock.release()
+    return r.cnt