milter-nomix.py
## A very simple milter to prevent mixing of internal and external mail.
# Internal is defined as using one of a list of internal top level domains.
# This code is open-source on the same terms as Python.
import Milter
import time
import sys
from Milter.utils import parse_addr
internal_tlds = ["corp", "personal"]
## Determine if a hostname is internal or not.
# True if internal, False otherwise
def is_internal(hostname):
components = hostname.split(".")
return components.pop() in internal_tlds:
# Determine if internal and external hosts are mixed based on a list
# of hostnames
def are_mixed(hostnames):
hostnames_mapped = map(is_internal, hostnames)
# Num internals
num_internal_hosts = hostnames_mapped.count(True)
# Num externals
num_external_hosts = hostnames_mapped.count(False)
return num_external_hosts >= 1 and num_internal_hosts >= 1
class NoMixMilter(Milter.Base):
def __init__(self): # A new instance with each new connection.
self.id = Milter.uniqueID() # Integer incremented with each call.
## def envfrom(self,f,*str):
@Milter.noreply
def envfrom(self, mailfrom, *str):
self.mailfrom = mailfrom
self.domains = []
t = parse_addr(mailfrom)
if len(t) > 1:
self.domains.append(t[1])
else:
self.domains.append('local')
self.internal = False
return Milter.CONTINUE
## def envrcpt(self, to, *str):
def envrcpt(self, to, *str):
self.R.append(to)
t = parse_addr(to)
if len(t) > 1:
self.domains.append(t[1])
else:
self.domains.append('local')
if are_mixed(self.domains):
# FIXME: log recipients collected in self.mailfrom and self.R
self.setreply('550','5.7.1','Mixing internal and external TLDs')
return Milter.REJECT
return Milter.CONTINUE
def main():
socketname = "/var/run/nomixsock"
timeout = 600
# Register to have the Milter factory create instances of your class:
Milter.factory = NoMixMilter
print "%s milter startup" % time.strftime('%Y%b%d %H:%M:%S')
sys.stdout.flush()
Milter.runmilter("nomixfilter",socketname,timeout)
logq.put(None)
bt.join()
print "%s nomix milter shutdown" % time.strftime('%Y%b%d %H:%M:%S')
if __name__ == "__main__":
main()