Add MTA policy module

Milter/policy.py

@@ -0,0 +1,67 @@
+try:
+  from bsddb3 import db
+  class DB(object):
+    def open(self,fname,mode):
+      if mode == 'r': flags = db.DB_RDONLY
+      else: raise RuntimeException('unsupported mode')
+      self.f = db.DB()
+      self.f.open(fname,flags=flags)
+    def __getitem__(self,key):
+      v = self.f.get(key)
+      if not v: raise KeyError(key)
+      return v
+    def close(self):
+      self.f.close()
+  def dbmopen(fname,mode):
+    f = DB()
+    f.open(fname,mode)
+    return f
+except:
+  import anydbm as dbm
+  dbmopen = dbm.open
+
+class MTAPolicy(object):
+  "Get SPF policy by result from sendmail style access file."
+  def __init__(self,sender,conf,access_file=None):
+    if not access_file:
+      access_file = conf.access_file
+    self.use_nulls = conf.access_file_nulls
+    self.sender = sender
+    self.domain = sender.split('@')[-1].lower()
+    self.acf = None
+    self.access_file = access_file
+
+  def close(self):
+    if self.acf:
+      self.acf.close()
+
+  def __enter__(self): 
+    self.acf = None
+    if self.access_file:
+      try:
+        self.acf = dbmopen(self.access_file,'r')
+      except:
+        print('%s: Cannot open for reading'%self.access_file)
+        syslog.syslog('%s: Cannot open for reading'%self.access_file)
+    return self
+  def __exit__(self,t,v,b): self.close()
+
+  def getPolicy(self,pfx):
+    acf = self.acf
+    if not acf: return None
+    if self.use_nulls: sfx = b'\x00'
+    else: sfx = b''
+    pfx = pfx.encode() + b'!'
+    try:
+      return acf[pfx + self.sender.encode() + sfx].rstrip(b'\x00').decode()
+    except KeyError:
+      try:
+        return acf[pfx + self.domain.encode() + sfx].rstrip(b'\x00').decode()
+      except KeyError:
+        try:
+          return acf[pfx + sfx].rstrip(b'\x00').decode()
+        except KeyError:
+          try:
+            return acf[pfx[:-1] + sfx].rstrip(b'\x00').decode()
+          except KeyError:
+            return None