| #! /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 | |
| 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 |