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Barry Warsaw7e0d9562001-01-31 22:51:35 +00001#! /usr/bin/env python
Barry Warsaw406d46e2001-08-13 21:18:01 +00002"""An RFC 2821 smtp proxy.
Barry Warsaw7e0d9562001-01-31 22:51:35 +00003
Barry Warsaw0e8427e2001-10-04 16:27:04 +00004Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]]
Barry Warsaw7e0d9562001-01-31 22:51:35 +00005
6Options:
7
8 --nosetuid
9 -n
10 This program generally tries to setuid `nobody', unless this flag is
11 set. The setuid call will fail if this program is not run as root (in
12 which case, use this flag).
13
14 --version
15 -V
16 Print the version number and exit.
17
18 --class classname
19 -c classname
20 Use `classname' as the concrete SMTP proxy class. Uses `SMTPProxy' by
21 default.
22
23 --debug
24 -d
25 Turn on debugging prints.
26
27 --help
28 -h
29 Print this message and exit.
30
31Version: %(__version__)s
32
Barry Warsaw0e8427e2001-10-04 16:27:04 +000033If localhost is not given then `localhost' is used, and if localport is not
34given then 8025 is used. If remotehost is not given then `localhost' is used,
35and if remoteport is not given, then 25 is used.
Barry Warsaw7e0d9562001-01-31 22:51:35 +000036"""
37
Barry Warsaw0e8427e2001-10-04 16:27:04 +000038
Barry Warsaw7e0d9562001-01-31 22:51:35 +000039# Overview:
40#
41# This file implements the minimal SMTP protocol as defined in RFC 821. It
42# has a hierarchy of classes which implement the backend functionality for the
43# smtpd. A number of classes are provided:
44#
Guido van Rossumb8b45ea2001-04-15 13:06:04 +000045# SMTPServer - the base class for the backend. Raises NotImplementedError
Barry Warsaw7e0d9562001-01-31 22:51:35 +000046# if you try to use it.
47#
48# DebuggingServer - simply prints each message it receives on stdout.
49#
50# PureProxy - Proxies all messages to a real smtpd which does final
51# delivery. One known problem with this class is that it doesn't handle
52# SMTP errors from the backend server at all. This should be fixed
53# (contributions are welcome!).
54#
55# MailmanProxy - An experimental hack to work with GNU Mailman
56# <www.list.org>. Using this server as your real incoming smtpd, your
57# mailhost will automatically recognize and accept mail destined to Mailman
58# lists when those lists are created. Every message not destined for a list
59# gets forwarded to a real backend smtpd, as with PureProxy. Again, errors
60# are not handled correctly yet.
61#
62# Please note that this script requires Python 2.0
63#
64# Author: Barry Warsaw <barry@digicool.com>
65#
66# TODO:
67#
68# - support mailbox delivery
69# - alias files
70# - ESMTP
71# - handle error codes from the backend smtpd
72
73import sys
74import os
75import errno
76import getopt
77import time
78import socket
79import asyncore
80import asynchat
81
Skip Montanaro0de65802001-02-15 22:15:14 +000082__all__ = ["SMTPServer","DebuggingServer","PureProxy","MailmanProxy"]
Barry Warsaw7e0d9562001-01-31 22:51:35 +000083
84program = sys.argv[0]
85__version__ = 'Python SMTP proxy version 0.2'
86
87
88class Devnull:
89 def write(self, msg): pass
90 def flush(self): pass
91
92
93DEBUGSTREAM = Devnull()
94NEWLINE = '\n'
95EMPTYSTRING = ''
Barry Warsaw0e8427e2001-10-04 16:27:04 +000096COMMASPACE = ', '
Barry Warsaw7e0d9562001-01-31 22:51:35 +000097
98
Barry Warsaw0e8427e2001-10-04 16:27:04 +000099
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000100def usage(code, msg=''):
101 print >> sys.stderr, __doc__ % globals()
102 if msg:
103 print >> sys.stderr, msg
104 sys.exit(code)
105
106
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000107
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000108class SMTPChannel(asynchat.async_chat):
109 COMMAND = 0
110 DATA = 1
111
112 def __init__(self, server, conn, addr):
113 asynchat.async_chat.__init__(self, conn)
114 self.__server = server
115 self.__conn = conn
116 self.__addr = addr
117 self.__line = []
118 self.__state = self.COMMAND
119 self.__greeting = 0
120 self.__mailfrom = None
121 self.__rcpttos = []
122 self.__data = ''
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000123 self.__fqdn = socket.getfqdn()
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000124 self.__peer = conn.getpeername()
125 print >> DEBUGSTREAM, 'Peer:', repr(self.__peer)
126 self.push('220 %s %s' % (self.__fqdn, __version__))
127 self.set_terminator('\r\n')
128
129 # Overrides base class for convenience
130 def push(self, msg):
131 asynchat.async_chat.push(self, msg + '\r\n')
132
133 # Implementation of base class abstract method
134 def collect_incoming_data(self, data):
135 self.__line.append(data)
136
137 # Implementation of base class abstract method
138 def found_terminator(self):
139 line = EMPTYSTRING.join(self.__line)
Barry Warsaw406d46e2001-08-13 21:18:01 +0000140 print >> DEBUGSTREAM, 'Data:', repr(line)
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000141 self.__line = []
142 if self.__state == self.COMMAND:
143 if not line:
144 self.push('500 Error: bad syntax')
145 return
146 method = None
147 i = line.find(' ')
148 if i < 0:
149 command = line.upper()
150 arg = None
151 else:
152 command = line[:i].upper()
153 arg = line[i+1:].strip()
154 method = getattr(self, 'smtp_' + command, None)
155 if not method:
156 self.push('502 Error: command "%s" not implemented' % command)
157 return
158 method(arg)
159 return
160 else:
Guido van Rossum4ba3d652001-03-02 06:42:34 +0000161 if self.__state != self.DATA:
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000162 self.push('451 Internal confusion')
163 return
164 # Remove extraneous carriage returns and de-transparency according
165 # to RFC 821, Section 4.5.2.
166 data = []
167 for text in line.split('\r\n'):
168 if text and text[0] == '.':
169 data.append(text[1:])
170 else:
171 data.append(text)
172 self.__data = NEWLINE.join(data)
173 status = self.__server.process_message(self.__peer,
174 self.__mailfrom,
175 self.__rcpttos,
176 self.__data)
177 self.__rcpttos = []
178 self.__mailfrom = None
179 self.__state = self.COMMAND
180 self.set_terminator('\r\n')
181 if not status:
182 self.push('250 Ok')
183 else:
184 self.push(status)
185
186 # SMTP and ESMTP commands
187 def smtp_HELO(self, arg):
188 if not arg:
189 self.push('501 Syntax: HELO hostname')
190 return
191 if self.__greeting:
192 self.push('503 Duplicate HELO/EHLO')
193 else:
194 self.__greeting = arg
195 self.push('250 %s' % self.__fqdn)
196
197 def smtp_NOOP(self, arg):
198 if arg:
199 self.push('501 Syntax: NOOP')
200 else:
201 self.push('250 Ok')
202
203 def smtp_QUIT(self, arg):
204 # args is ignored
205 self.push('221 Bye')
206 self.close_when_done()
207
208 # factored
209 def __getaddr(self, keyword, arg):
210 address = None
211 keylen = len(keyword)
212 if arg[:keylen].upper() == keyword:
213 address = arg[keylen:].strip()
Barry Warsawebf54272001-11-04 03:04:25 +0000214 if not address:
215 pass
216 elif address[0] == '<' and address[-1] == '>' and address != '<>':
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000217 # Addresses can be in the form <person@dom.com> but watch out
218 # for null address, e.g. <>
219 address = address[1:-1]
220 return address
221
222 def smtp_MAIL(self, arg):
223 print >> DEBUGSTREAM, '===> MAIL', arg
224 address = self.__getaddr('FROM:', arg)
225 if not address:
226 self.push('501 Syntax: MAIL FROM:<address>')
227 return
228 if self.__mailfrom:
229 self.push('503 Error: nested MAIL command')
230 return
231 self.__mailfrom = address
232 print >> DEBUGSTREAM, 'sender:', self.__mailfrom
233 self.push('250 Ok')
234
235 def smtp_RCPT(self, arg):
236 print >> DEBUGSTREAM, '===> RCPT', arg
237 if not self.__mailfrom:
238 self.push('503 Error: need MAIL command')
239 return
240 address = self.__getaddr('TO:', arg)
241 if not address:
242 self.push('501 Syntax: RCPT TO: <address>')
243 return
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000244 self.__rcpttos.append(address)
245 print >> DEBUGSTREAM, 'recips:', self.__rcpttos
246 self.push('250 Ok')
247
248 def smtp_RSET(self, arg):
249 if arg:
250 self.push('501 Syntax: RSET')
251 return
252 # Resets the sender, recipients, and data, but not the greeting
253 self.__mailfrom = None
254 self.__rcpttos = []
255 self.__data = ''
256 self.__state = self.COMMAND
257 self.push('250 Ok')
258
259 def smtp_DATA(self, arg):
260 if not self.__rcpttos:
261 self.push('503 Error: need RCPT command')
262 return
263 if arg:
264 self.push('501 Syntax: DATA')
265 return
266 self.__state = self.DATA
267 self.set_terminator('\r\n.\r\n')
268 self.push('354 End data with <CR><LF>.<CR><LF>')
269
270
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000271
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000272class SMTPServer(asyncore.dispatcher):
273 def __init__(self, localaddr, remoteaddr):
274 self._localaddr = localaddr
275 self._remoteaddr = remoteaddr
276 asyncore.dispatcher.__init__(self)
277 self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
278 # try to re-use a server port if possible
Barry Warsaw93a63272001-10-09 15:46:31 +0000279 self.set_reuse_addr()
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000280 self.bind(localaddr)
281 self.listen(5)
Barry Warsaw4a8e9f42001-10-05 17:10:31 +0000282 print >> DEBUGSTREAM, \
283 '%s started at %s\n\tLocal addr: %s\n\tRemote addr:%s' % (
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000284 self.__class__.__name__, time.ctime(time.time()),
285 localaddr, remoteaddr)
286
287 def handle_accept(self):
288 conn, addr = self.accept()
289 print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
290 channel = SMTPChannel(self, conn, addr)
291
292 # API for "doing something useful with the message"
293 def process_message(self, peer, mailfrom, rcpttos, data):
294 """Override this abstract method to handle messages from the client.
295
296 peer is a tuple containing (ipaddr, port) of the client that made the
297 socket connection to our smtp port.
298
299 mailfrom is the raw address the client claims the message is coming
300 from.
301
302 rcpttos is a list of raw addresses the client wishes to deliver the
303 message to.
304
305 data is a string containing the entire full text of the message,
306 headers (if supplied) and all. It has been `de-transparencied'
307 according to RFC 821, Section 4.5.2. In other words, a line
308 containing a `.' followed by other text has had the leading dot
309 removed.
310
311 This function should return None, for a normal `250 Ok' response;
312 otherwise it returns the desired response string in RFC 821 format.
313
314 """
Guido van Rossumb8b45ea2001-04-15 13:06:04 +0000315 raise NotImplementedError
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000316
Tim Peters658cba62001-02-09 20:06:00 +0000317
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000318
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000319class DebuggingServer(SMTPServer):
320 # Do something with the gathered message
321 def process_message(self, peer, mailfrom, rcpttos, data):
322 inheaders = 1
323 lines = data.split('\n')
324 print '---------- MESSAGE FOLLOWS ----------'
325 for line in lines:
326 # headers first
327 if inheaders and not line:
328 print 'X-Peer:', peer[0]
329 inheaders = 0
330 print line
331 print '------------ END MESSAGE ------------'
332
333
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000334
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000335class PureProxy(SMTPServer):
336 def process_message(self, peer, mailfrom, rcpttos, data):
337 lines = data.split('\n')
338 # Look for the last header
339 i = 0
340 for line in lines:
341 if not line:
342 break
343 i += 1
344 lines.insert(i, 'X-Peer: %s' % peer[0])
345 data = NEWLINE.join(lines)
346 refused = self._deliver(mailfrom, rcpttos, data)
347 # TBD: what to do with refused addresses?
Neal Norwitzf1516252002-02-11 18:05:05 +0000348 print >> DEBUGSTREAM, 'we got some refusals:', refused
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000349
350 def _deliver(self, mailfrom, rcpttos, data):
351 import smtplib
352 refused = {}
353 try:
354 s = smtplib.SMTP()
355 s.connect(self._remoteaddr[0], self._remoteaddr[1])
356 try:
357 refused = s.sendmail(mailfrom, rcpttos, data)
358 finally:
359 s.quit()
360 except smtplib.SMTPRecipientsRefused, e:
361 print >> DEBUGSTREAM, 'got SMTPRecipientsRefused'
362 refused = e.recipients
363 except (socket.error, smtplib.SMTPException), e:
364 print >> DEBUGSTREAM, 'got', e.__class__
365 # All recipients were refused. If the exception had an associated
366 # error code, use it. Otherwise,fake it with a non-triggering
367 # exception code.
368 errcode = getattr(e, 'smtp_code', -1)
369 errmsg = getattr(e, 'smtp_error', 'ignore')
370 for r in rcpttos:
371 refused[r] = (errcode, errmsg)
372 return refused
373
374
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000375
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000376class MailmanProxy(PureProxy):
377 def process_message(self, peer, mailfrom, rcpttos, data):
378 from cStringIO import StringIO
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000379 from Mailman import Utils
380 from Mailman import Message
381 from Mailman import MailList
382 # If the message is to a Mailman mailing list, then we'll invoke the
383 # Mailman script directly, without going through the real smtpd.
384 # Otherwise we'll forward it to the local proxy for disposition.
385 listnames = []
386 for rcpt in rcpttos:
387 local = rcpt.lower().split('@')[0]
388 # We allow the following variations on the theme
389 # listname
390 # listname-admin
391 # listname-owner
392 # listname-request
393 # listname-join
394 # listname-leave
395 parts = local.split('-')
396 if len(parts) > 2:
397 continue
398 listname = parts[0]
399 if len(parts) == 2:
400 command = parts[1]
401 else:
402 command = ''
403 if not Utils.list_exists(listname) or command not in (
404 '', 'admin', 'owner', 'request', 'join', 'leave'):
405 continue
406 listnames.append((rcpt, listname, command))
407 # Remove all list recipients from rcpttos and forward what we're not
408 # going to take care of ourselves. Linear removal should be fine
409 # since we don't expect a large number of recipients.
410 for rcpt, listname, command in listnames:
411 rcpttos.remove(rcpt)
Tim Peters658cba62001-02-09 20:06:00 +0000412 # If there's any non-list destined recipients left,
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000413 print >> DEBUGSTREAM, 'forwarding recips:', ' '.join(rcpttos)
414 if rcpttos:
415 refused = self._deliver(mailfrom, rcpttos, data)
416 # TBD: what to do with refused addresses?
Neal Norwitzf1516252002-02-11 18:05:05 +0000417 print >> DEBUGSTREAM, 'we got refusals:', refused
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000418 # Now deliver directly to the list commands
419 mlists = {}
420 s = StringIO(data)
421 msg = Message.Message(s)
422 # These headers are required for the proper execution of Mailman. All
423 # MTAs in existance seem to add these if the original message doesn't
424 # have them.
425 if not msg.getheader('from'):
426 msg['From'] = mailfrom
427 if not msg.getheader('date'):
428 msg['Date'] = time.ctime(time.time())
429 for rcpt, listname, command in listnames:
430 print >> DEBUGSTREAM, 'sending message to', rcpt
431 mlist = mlists.get(listname)
432 if not mlist:
433 mlist = MailList.MailList(listname, lock=0)
434 mlists[listname] = mlist
435 # dispatch on the type of command
436 if command == '':
437 # post
438 msg.Enqueue(mlist, tolist=1)
439 elif command == 'admin':
440 msg.Enqueue(mlist, toadmin=1)
441 elif command == 'owner':
442 msg.Enqueue(mlist, toowner=1)
443 elif command == 'request':
444 msg.Enqueue(mlist, torequest=1)
445 elif command in ('join', 'leave'):
446 # TBD: this is a hack!
447 if command == 'join':
448 msg['Subject'] = 'subscribe'
449 else:
450 msg['Subject'] = 'unsubscribe'
451 msg.Enqueue(mlist, torequest=1)
452
453
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000454
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000455class Options:
456 setuid = 1
457 classname = 'PureProxy'
458
459
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000460
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000461def parseargs():
462 global DEBUGSTREAM
463 try:
464 opts, args = getopt.getopt(
465 sys.argv[1:], 'nVhc:d',
466 ['class=', 'nosetuid', 'version', 'help', 'debug'])
467 except getopt.error, e:
468 usage(1, e)
469
470 options = Options()
471 for opt, arg in opts:
472 if opt in ('-h', '--help'):
473 usage(0)
474 elif opt in ('-V', '--version'):
475 print >> sys.stderr, __version__
476 sys.exit(0)
477 elif opt in ('-n', '--nosetuid'):
478 options.setuid = 0
479 elif opt in ('-c', '--class'):
480 options.classname = arg
481 elif opt in ('-d', '--debug'):
482 DEBUGSTREAM = sys.stderr
483
484 # parse the rest of the arguments
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000485 if len(args) < 1:
486 localspec = 'localhost:8025'
487 remotespec = 'localhost:25'
488 elif len(args) < 2:
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000489 localspec = args[0]
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000490 remotespec = 'localhost:25'
Barry Warsawebf54272001-11-04 03:04:25 +0000491 elif len(args) < 3:
492 localspec = args[0]
493 remotespec = args[1]
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000494 else:
495 usage(1, 'Invalid arguments: %s' % COMMASPACE.join(args))
496
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000497 # split into host/port pairs
498 i = localspec.find(':')
499 if i < 0:
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000500 usage(1, 'Bad local spec: %s' % localspec)
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000501 options.localhost = localspec[:i]
502 try:
503 options.localport = int(localspec[i+1:])
504 except ValueError:
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000505 usage(1, 'Bad local port: %s' % localspec)
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000506 i = remotespec.find(':')
507 if i < 0:
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000508 usage(1, 'Bad remote spec: %s' % remotespec)
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000509 options.remotehost = remotespec[:i]
510 try:
511 options.remoteport = int(remotespec[i+1:])
512 except ValueError:
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000513 usage(1, 'Bad remote port: %s' % remotespec)
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000514 return options
515
516
Barry Warsaw0e8427e2001-10-04 16:27:04 +0000517
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000518if __name__ == '__main__':
519 options = parseargs()
520 # Become nobody
521 if options.setuid:
522 try:
523 import pwd
524 except ImportError:
525 print >> sys.stderr, \
526 'Cannot import module "pwd"; try running with -n option.'
527 sys.exit(1)
528 nobody = pwd.getpwnam('nobody')[2]
529 try:
530 os.setuid(nobody)
531 except OSError, e:
Guido van Rossum4ba3d652001-03-02 06:42:34 +0000532 if e.errno != errno.EPERM: raise
Barry Warsaw7e0d9562001-01-31 22:51:35 +0000533 print >> sys.stderr, \
534 'Cannot setuid "nobody"; try running with -n option.'
535 sys.exit(1)
536 import __main__
537 class_ = getattr(__main__, options.classname)
538 proxy = class_((options.localhost, options.localport),
539 (options.remotehost, options.remoteport))
540 try:
541 asyncore.loop()
542 except KeyboardInterrupt:
543 pass