| #! /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() |
| try: |
| self.__peer = conn.getpeername() |
| except socket.error, err: |
| # a race condition may occur if the other end is closing |
| # before we can get the peername |
| self.close() |
| if err[0] != errno.ENOTCONN: |
| raise |
| return |
| 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 arg else None |
| 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 arg else None |
| 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) |
| try: |
| 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) |
| except: |
| # cleanup asyncore.socket_map before raising |
| self.close() |
| raise |
| else: |
| 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): |
| pair = self.accept() |
| if pair is not None: |
| conn, addr = pair |
| 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 existence 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 |
| 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)) |
| 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) |
| try: |
| asyncore.loop() |
| except KeyboardInterrupt: |
| pass |
