#! /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 notgiven 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 sysimport osimport errnoimport getoptimport timeimport socketimport asyncoreimport 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)

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