550 lines
18 KiB
Python
Executable file
550 lines
18 KiB
Python
Executable file
#! /usr/bin/env python
|
||
"""An RFC 2821 smtp proxy.
|
||
|
||
Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]]
|
||
|
||
Options:
|
||
|
||
--nosetuid
|
||
-n
|
||
This program generally tries to setuid `nobody', unless this flag is
|
||
set. The setuid call will fail if this program is not run as root (in
|
||
which case, use this flag).
|
||
|
||
--version
|
||
-V
|
||
Print the version number and exit.
|
||
|
||
--class classname
|
||
-c classname
|
||
Use `classname' as the concrete SMTP proxy class. Uses `PureProxy' by
|
||
default.
|
||
|
||
--debug
|
||
-d
|
||
Turn on debugging prints.
|
||
|
||
--help
|
||
-h
|
||
Print this message and exit.
|
||
|
||
Version: %(__version__)s
|
||
|
||
If localhost is not given then `localhost' is used, and if localport is not
|
||
given then 8025 is used. If remotehost is not given then `localhost' is used,
|
||
and if remoteport is not given, then 25 is used.
|
||
"""
|
||
|
||
|
||
# Overview:
|
||
#
|
||
# This file implements the minimal SMTP protocol as defined in RFC 821. It
|
||
# has a hierarchy of classes which implement the backend functionality for the
|
||
# smtpd. A number of classes are provided:
|
||
#
|
||
# SMTPServer - the base class for the backend. Raises NotImplementedError
|
||
# if you try to use it.
|
||
#
|
||
# DebuggingServer - simply prints each message it receives on stdout.
|
||
#
|
||
# PureProxy - Proxies all messages to a real smtpd which does final
|
||
# delivery. One known problem with this class is that it doesn't handle
|
||
# SMTP errors from the backend server at all. This should be fixed
|
||
# (contributions are welcome!).
|
||
#
|
||
# MailmanProxy - An experimental hack to work with GNU Mailman
|
||
# <www.list.org>. Using this server as your real incoming smtpd, your
|
||
# mailhost will automatically recognize and accept mail destined to Mailman
|
||
# lists when those lists are created. Every message not destined for a list
|
||
# gets forwarded to a real backend smtpd, as with PureProxy. Again, errors
|
||
# are not handled correctly yet.
|
||
#
|
||
# Please note that this script requires Python 2.0
|
||
#
|
||
# Author: Barry Warsaw <barry@python.org>
|
||
#
|
||
# TODO:
|
||
#
|
||
# - support mailbox delivery
|
||
# - alias files
|
||
# - ESMTP
|
||
# - handle error codes from the backend smtpd
|
||
|
||
import sys
|
||
import os
|
||
import errno
|
||
import getopt
|
||
import time
|
||
import socket
|
||
import asyncore
|
||
import asynchat
|
||
|
||
__all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"]
|
||
|
||
program = sys.argv[0]
|
||
__version__ = 'Python SMTP proxy version 0.2'
|
||
|
||
|
||
class Devnull:
|
||
def write(self, msg): pass
|
||
def flush(self): pass
|
||
|
||
|
||
DEBUGSTREAM = Devnull()
|
||
NEWLINE = '\n'
|
||
EMPTYSTRING = ''
|
||
COMMASPACE = ', '
|
||
|
||
|
||
|
||
def usage(code, msg=''):
|
||
print >> sys.stderr, __doc__ % globals()
|
||
if msg:
|
||
print >> sys.stderr, msg
|
||
sys.exit(code)
|
||
|
||
|
||
|
||
class SMTPChannel(asynchat.async_chat):
|
||
COMMAND = 0
|
||
DATA = 1
|
||
|
||
def __init__(self, server, conn, addr):
|
||
asynchat.async_chat.__init__(self, conn)
|
||
self.__server = server
|
||
self.__conn = conn
|
||
self.__addr = addr
|
||
self.__line = []
|
||
self.__state = self.COMMAND
|
||
self.__greeting = 0
|
||
self.__mailfrom = None
|
||
self.__rcpttos = []
|
||
self.__data = ''
|
||
self.__fqdn = socket.getfqdn()
|
||
self.__peer = conn.getpeername()
|
||
print >> DEBUGSTREAM, 'Peer:', repr(self.__peer)
|
||
self.push('220 %s %s' % (self.__fqdn, __version__))
|
||
self.set_terminator('\r\n')
|
||
|
||
# Overrides base class for convenience
|
||
def push(self, msg):
|
||
asynchat.async_chat.push(self, msg + '\r\n')
|
||
|
||
# Implementation of base class abstract method
|
||
def collect_incoming_data(self, data):
|
||
self.__line.append(data)
|
||
|
||
# Implementation of base class abstract method
|
||
def found_terminator(self):
|
||
line = EMPTYSTRING.join(self.__line)
|
||
print >> DEBUGSTREAM, 'Data:', repr(line)
|
||
self.__line = []
|
||
if self.__state == self.COMMAND:
|
||
if not line:
|
||
self.push('500 Error: bad syntax')
|
||
return
|
||
method = None
|
||
i = line.find(' ')
|
||
if i < 0:
|
||
command = line.upper()
|
||
arg = None
|
||
else:
|
||
command = line[:i].upper()
|
||
arg = line[i+1:].strip()
|
||
method = getattr(self, 'smtp_' + command, None)
|
||
if not method:
|
||
self.push('502 Error: command "%s" not implemented' % command)
|
||
return
|
||
method(arg)
|
||
return
|
||
else:
|
||
if self.__state != self.DATA:
|
||
self.push('451 Internal confusion')
|
||
return
|
||
# Remove extraneous carriage returns and de-transparency according
|
||
# to RFC 821, Section 4.5.2.
|
||
data = []
|
||
for text in line.split('\r\n'):
|
||
if text and text[0] == '.':
|
||
data.append(text[1:])
|
||
else:
|
||
data.append(text)
|
||
self.__data = NEWLINE.join(data)
|
||
status = self.__server.process_message(self.__peer,
|
||
self.__mailfrom,
|
||
self.__rcpttos,
|
||
self.__data)
|
||
self.__rcpttos = []
|
||
self.__mailfrom = None
|
||
self.__state = self.COMMAND
|
||
self.set_terminator('\r\n')
|
||
if not status:
|
||
self.push('250 Ok')
|
||
else:
|
||
self.push(status)
|
||
|
||
# SMTP and ESMTP commands
|
||
def smtp_HELO(self, arg):
|
||
if not arg:
|
||
self.push('501 Syntax: HELO hostname')
|
||
return
|
||
if self.__greeting:
|
||
self.push('503 Duplicate HELO/EHLO')
|
||
else:
|
||
self.__greeting = arg
|
||
self.push('250 %s' % self.__fqdn)
|
||
|
||
def smtp_NOOP(self, arg):
|
||
if arg:
|
||
self.push('501 Syntax: NOOP')
|
||
else:
|
||
self.push('250 Ok')
|
||
|
||
def smtp_QUIT(self, arg):
|
||
# args is ignored
|
||
self.push('221 Bye')
|
||
self.close_when_done()
|
||
|
||
# factored
|
||
def __getaddr(self, keyword, arg):
|
||
address = None
|
||
keylen = len(keyword)
|
||
if arg[:keylen].upper() == keyword:
|
||
address = arg[keylen:].strip()
|
||
if not address:
|
||
pass
|
||
elif address[0] == '<' and address[-1] == '>' and address != '<>':
|
||
# Addresses can be in the form <person@dom.com> but watch out
|
||
# for null address, e.g. <>
|
||
address = address[1:-1]
|
||
return address
|
||
|
||
def smtp_MAIL(self, arg):
|
||
print >> DEBUGSTREAM, '===> MAIL', arg
|
||
address = self.__getaddr('FROM:', arg)
|
||
if not address:
|
||
self.push('501 Syntax: MAIL FROM:<address>')
|
||
return
|
||
if self.__mailfrom:
|
||
self.push('503 Error: nested MAIL command')
|
||
return
|
||
self.__mailfrom = address
|
||
print >> DEBUGSTREAM, 'sender:', self.__mailfrom
|
||
self.push('250 Ok')
|
||
|
||
def smtp_RCPT(self, arg):
|
||
print >> DEBUGSTREAM, '===> RCPT', arg
|
||
if not self.__mailfrom:
|
||
self.push('503 Error: need MAIL command')
|
||
return
|
||
address = self.__getaddr('TO:', arg)
|
||
if not address:
|
||
self.push('501 Syntax: RCPT TO: <address>')
|
||
return
|
||
self.__rcpttos.append(address)
|
||
print >> DEBUGSTREAM, 'recips:', self.__rcpttos
|
||
self.push('250 Ok')
|
||
|
||
def smtp_RSET(self, arg):
|
||
if arg:
|
||
self.push('501 Syntax: RSET')
|
||
return
|
||
# Resets the sender, recipients, and data, but not the greeting
|
||
self.__mailfrom = None
|
||
self.__rcpttos = []
|
||
self.__data = ''
|
||
self.__state = self.COMMAND
|
||
self.push('250 Ok')
|
||
|
||
def smtp_DATA(self, arg):
|
||
if not self.__rcpttos:
|
||
self.push('503 Error: need RCPT command')
|
||
return
|
||
if arg:
|
||
self.push('501 Syntax: DATA')
|
||
return
|
||
self.__state = self.DATA
|
||
self.set_terminator('\r\n.\r\n')
|
||
self.push('354 End data with <CR><LF>.<CR><LF>')
|
||
|
||
|
||
|
||
class SMTPServer(asyncore.dispatcher):
|
||
def __init__(self, localaddr, remoteaddr):
|
||
self._localaddr = localaddr
|
||
self._remoteaddr = remoteaddr
|
||
asyncore.dispatcher.__init__(self)
|
||
self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
|
||
# try to re-use a server port if possible
|
||
self.set_reuse_addr()
|
||
self.bind(localaddr)
|
||
self.listen(5)
|
||
print >> DEBUGSTREAM, \
|
||
'%s started at %s\n\tLocal addr: %s\n\tRemote addr:%s' % (
|
||
self.__class__.__name__, time.ctime(time.time()),
|
||
localaddr, remoteaddr)
|
||
|
||
def handle_accept(self):
|
||
conn, addr = self.accept()
|
||
print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
|
||
channel = SMTPChannel(self, conn, addr)
|
||
|
||
# API for "doing something useful with the message"
|
||
def process_message(self, peer, mailfrom, rcpttos, data):
|
||
"""Override this abstract method to handle messages from the client.
|
||
|
||
peer is a tuple containing (ipaddr, port) of the client that made the
|
||
socket connection to our smtp port.
|
||
|
||
mailfrom is the raw address the client claims the message is coming
|
||
from.
|
||
|
||
rcpttos is a list of raw addresses the client wishes to deliver the
|
||
message to.
|
||
|
||
data is a string containing the entire full text of the message,
|
||
headers (if supplied) and all. It has been `de-transparencied'
|
||
according to RFC 821, Section 4.5.2. In other words, a line
|
||
containing a `.' followed by other text has had the leading dot
|
||
removed.
|
||
|
||
This function should return None, for a normal `250 Ok' response;
|
||
otherwise it returns the desired response string in RFC 821 format.
|
||
|
||
"""
|
||
raise NotImplementedError
|
||
|
||
|
||
|
||
class DebuggingServer(SMTPServer):
|
||
# Do something with the gathered message
|
||
def process_message(self, peer, mailfrom, rcpttos, data):
|
||
inheaders = 1
|
||
lines = data.split('\n')
|
||
print '---------- MESSAGE FOLLOWS ----------'
|
||
for line in lines:
|
||
# headers first
|
||
if inheaders and not line:
|
||
print 'X-Peer:', peer[0]
|
||
inheaders = 0
|
||
print line
|
||
print '------------ END MESSAGE ------------'
|
||
|
||
|
||
|
||
class PureProxy(SMTPServer):
|
||
def process_message(self, peer, mailfrom, rcpttos, data):
|
||
lines = data.split('\n')
|
||
# Look for the last header
|
||
i = 0
|
||
for line in lines:
|
||
if not line:
|
||
break
|
||
i += 1
|
||
lines.insert(i, 'X-Peer: %s' % peer[0])
|
||
data = NEWLINE.join(lines)
|
||
refused = self._deliver(mailfrom, rcpttos, data)
|
||
# TBD: what to do with refused addresses?
|
||
print >> DEBUGSTREAM, 'we got some refusals:', refused
|
||
|
||
def _deliver(self, mailfrom, rcpttos, data):
|
||
import smtplib
|
||
refused = {}
|
||
try:
|
||
s = smtplib.SMTP()
|
||
s.connect(self._remoteaddr[0], self._remoteaddr[1])
|
||
try:
|
||
refused = s.sendmail(mailfrom, rcpttos, data)
|
||
finally:
|
||
s.quit()
|
||
except smtplib.SMTPRecipientsRefused, e:
|
||
print >> DEBUGSTREAM, 'got SMTPRecipientsRefused'
|
||
refused = e.recipients
|
||
except (socket.error, smtplib.SMTPException), e:
|
||
print >> DEBUGSTREAM, 'got', e.__class__
|
||
# All recipients were refused. If the exception had an associated
|
||
# error code, use it. Otherwise,fake it with a non-triggering
|
||
# exception code.
|
||
errcode = getattr(e, 'smtp_code', -1)
|
||
errmsg = getattr(e, 'smtp_error', 'ignore')
|
||
for r in rcpttos:
|
||
refused[r] = (errcode, errmsg)
|
||
return refused
|
||
|
||
|
||
|
||
class MailmanProxy(PureProxy):
|
||
def process_message(self, peer, mailfrom, rcpttos, data):
|
||
from cStringIO import StringIO
|
||
from Mailman import Utils
|
||
from Mailman import Message
|
||
from Mailman import MailList
|
||
# If the message is to a Mailman mailing list, then we'll invoke the
|
||
# Mailman script directly, without going through the real smtpd.
|
||
# Otherwise we'll forward it to the local proxy for disposition.
|
||
listnames = []
|
||
for rcpt in rcpttos:
|
||
local = rcpt.lower().split('@')[0]
|
||
# We allow the following variations on the theme
|
||
# listname
|
||
# listname-admin
|
||
# listname-owner
|
||
# listname-request
|
||
# listname-join
|
||
# listname-leave
|
||
parts = local.split('-')
|
||
if len(parts) > 2:
|
||
continue
|
||
listname = parts[0]
|
||
if len(parts) == 2:
|
||
command = parts[1]
|
||
else:
|
||
command = ''
|
||
if not Utils.list_exists(listname) or command not in (
|
||
'', 'admin', 'owner', 'request', 'join', 'leave'):
|
||
continue
|
||
listnames.append((rcpt, listname, command))
|
||
# Remove all list recipients from rcpttos and forward what we're not
|
||
# going to take care of ourselves. Linear removal should be fine
|
||
# since we don't expect a large number of recipients.
|
||
for rcpt, listname, command in listnames:
|
||
rcpttos.remove(rcpt)
|
||
# If there's any non-list destined recipients left,
|
||
print >> DEBUGSTREAM, 'forwarding recips:', ' '.join(rcpttos)
|
||
if rcpttos:
|
||
refused = self._deliver(mailfrom, rcpttos, data)
|
||
# TBD: what to do with refused addresses?
|
||
print >> DEBUGSTREAM, 'we got refusals:', refused
|
||
# Now deliver directly to the list commands
|
||
mlists = {}
|
||
s = StringIO(data)
|
||
msg = Message.Message(s)
|
||
# These headers are required for the proper execution of Mailman. All
|
||
# MTAs in existance seem to add these if the original message doesn't
|
||
# have them.
|
||
if not msg.getheader('from'):
|
||
msg['From'] = mailfrom
|
||
if not msg.getheader('date'):
|
||
msg['Date'] = time.ctime(time.time())
|
||
for rcpt, listname, command in listnames:
|
||
print >> DEBUGSTREAM, 'sending message to', rcpt
|
||
mlist = mlists.get(listname)
|
||
if not mlist:
|
||
mlist = MailList.MailList(listname, lock=0)
|
||
mlists[listname] = mlist
|
||
# dispatch on the type of command
|
||
if command == '':
|
||
# post
|
||
msg.Enqueue(mlist, tolist=1)
|
||
elif command == 'admin':
|
||
msg.Enqueue(mlist, toadmin=1)
|
||
elif command == 'owner':
|
||
msg.Enqueue(mlist, toowner=1)
|
||
elif command == 'request':
|
||
msg.Enqueue(mlist, torequest=1)
|
||
elif command in ('join', 'leave'):
|
||
# TBD: this is a hack!
|
||
if command == 'join':
|
||
msg['Subject'] = 'subscribe'
|
||
else:
|
||
msg['Subject'] = 'unsubscribe'
|
||
msg.Enqueue(mlist, torequest=1)
|
||
|
||
|
||
|
||
class Options:
|
||
setuid = 1
|
||
classname = 'PureProxy'
|
||
|
||
|
||
|
||
def parseargs():
|
||
global DEBUGSTREAM
|
||
try:
|
||
opts, args = getopt.getopt(
|
||
sys.argv[1:], 'nVhc:d',
|
||
['class=', 'nosetuid', 'version', 'help', 'debug'])
|
||
except getopt.error, e:
|
||
usage(1, e)
|
||
|
||
options = Options()
|
||
for opt, arg in opts:
|
||
if opt in ('-h', '--help'):
|
||
usage(0)
|
||
elif opt in ('-V', '--version'):
|
||
print >> sys.stderr, __version__
|
||
sys.exit(0)
|
||
elif opt in ('-n', '--nosetuid'):
|
||
options.setuid = 0
|
||
elif opt in ('-c', '--class'):
|
||
options.classname = arg
|
||
elif opt in ('-d', '--debug'):
|
||
DEBUGSTREAM = sys.stderr
|
||
|
||
# parse the rest of the arguments
|
||
if len(args) < 1:
|
||
localspec = 'localhost:8025'
|
||
remotespec = 'localhost:25'
|
||
elif len(args) < 2:
|
||
localspec = args[0]
|
||
remotespec = 'localhost:25'
|
||
elif len(args) < 3:
|
||
localspec = args[0]
|
||
remotespec = args[1]
|
||
else:
|
||
usage(1, 'Invalid arguments: %s' % COMMASPACE.join(args))
|
||
|
||
# split into host/port pairs
|
||
i = localspec.find(':')
|
||
if i < 0:
|
||
usage(1, 'Bad local spec: %s' % localspec)
|
||
options.localhost = localspec[:i]
|
||
try:
|
||
options.localport = int(localspec[i+1:])
|
||
except ValueError:
|
||
usage(1, 'Bad local port: %s' % localspec)
|
||
i = remotespec.find(':')
|
||
if i < 0:
|
||
usage(1, 'Bad remote spec: %s' % remotespec)
|
||
options.remotehost = remotespec[:i]
|
||
try:
|
||
options.remoteport = int(remotespec[i+1:])
|
||
except ValueError:
|
||
usage(1, 'Bad remote port: %s' % remotespec)
|
||
return options
|
||
|
||
|
||
|
||
if __name__ == '__main__':
|
||
options = parseargs()
|
||
# Become nobody
|
||
if options.setuid:
|
||
try:
|
||
import pwd
|
||
except ImportError:
|
||
print >> sys.stderr, \
|
||
'Cannot import module "pwd"; try running with -n option.'
|
||
sys.exit(1)
|
||
nobody = pwd.getpwnam('nobody')[2]
|
||
try:
|
||
os.setuid(nobody)
|
||
except OSError, e:
|
||
if e.errno != errno.EPERM: raise
|
||
print >> sys.stderr, \
|
||
'Cannot setuid "nobody"; try running with -n option.'
|
||
sys.exit(1)
|
||
classname = options.classname
|
||
if "." in classname:
|
||
lastdot = classname.rfind(".")
|
||
mod = __import__(classname[:lastdot], globals(), locals(), [""])
|
||
classname = classname[lastdot+1:]
|
||
else:
|
||
import __main__ as mod
|
||
class_ = getattr(mod, classname)
|
||
proxy = class_((options.localhost, options.localport),
|
||
(options.remotehost, options.remoteport))
|
||
try:
|
||
asyncore.loop()
|
||
except KeyboardInterrupt:
|
||
pass
|