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#! /usr/bin/env python
"""An RFC 2821 smtp proxy.

Usage: %(program)s [options] [localhost:localport [remotehost:remoteport]]


        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).

        Print the version number and exit.

    --class classname
    -c classname
        Use `classname' as the concrete SMTP proxy class.  Uses `SMTPProxy' by

        Turn on debugging prints.

        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@digicool.com>
# - support mailbox delivery
# - alias files
# - 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

NEWLINE = '\n'

def usage(code, msg=''):
    print >> sys.stderr, __doc__ % globals()
    if msg:
        print >> sys.stderr, msg

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__))

    # 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):

    # 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')
            method = None
            i = line.find(' ')
            if i < 0:
                command = line.upper()
                arg = None
                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)
            if self.__state != self.DATA:
                self.push('451 Internal confusion')
            # 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] == '.':
            self.__data = NEWLINE.join(data)
            status = self.__server.process_message(self.__peer,
            self.__rcpttos = []
            self.__mailfrom = None
            self.__state = self.COMMAND
            if not status:
                self.push('250 Ok')

    # SMTP and ESMTP commands
    def smtp_HELO(self, arg):
        if not arg:
            self.push('501 Syntax: HELO hostname')
        if self.__greeting:
            self.push('503 Duplicate HELO/EHLO')
            self.__greeting = arg
            self.push('250 %s' % self.__fqdn)

    def smtp_NOOP(self, arg):
        if arg:
            self.push('501 Syntax: NOOP')
            self.push('250 Ok')

    def smtp_QUIT(self, arg):
        # args is ignored
        self.push('221 Bye')

    # factored
    def __getaddr(self, keyword, arg):
        address = None
        keylen = len(keyword)
        if arg[:keylen].upper() == keyword:
            address = arg[keylen:].strip()
            if not address:
            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>')
        if self.__mailfrom:
            self.push('503 Error: nested MAIL command')
        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')
        address = self.__getaddr('TO:', arg)
        if not address:
            self.push('501 Syntax: RCPT TO: <address>')
        if address.lower().startswith('stimpy'):
            self.push('503 You suck %s' % address)
        print >> DEBUGSTREAM, 'recips:', self.__rcpttos
        self.push('250 Ok')

    def smtp_RSET(self, arg):
        if arg:
            self.push('501 Syntax: RSET')
        # 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')
        if arg:
            self.push('501 Syntax: DATA')
        self.__state = self.DATA
        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
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        # try to re-use a server port if possible
        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

        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

        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:
            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'

    def _deliver(self, mailfrom, rcpttos, data):
        import smtplib
        refused = {}
            s = smtplib.SMTP()
            s.connect(self._remoteaddr[0], self._remoteaddr[1])
                refused = s.sendmail(mailfrom, rcpttos, data)
        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:
            listname = parts[0]
            if len(parts) == 2:
                command = parts[1]
                command = ''
            if not Utils.list_exists(listname) or command not in (
                    '', 'admin', 'owner', 'request', 'join', 'leave'):
            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:
        # 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'
        # 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'
                    msg['Subject'] = 'unsubscribe'
                msg.Enqueue(mlist, torequest=1)

class Options:
    setuid = 1
    classname = 'PureProxy'

def parseargs():
    global DEBUGSTREAM
        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'):
        elif opt in ('-V', '--version'):
            print >> sys.stderr, __version__
        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]
        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]
        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]
        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:
            import pwd
        except ImportError:
            print >> sys.stderr, \
                  'Cannot import module "pwd"; try running with -n option.'
        nobody = pwd.getpwnam('nobody')[2]
        except OSError, e:
            if e.errno != errno.EPERM: raise
            print >> sys.stderr, \
                  'Cannot setuid "nobody"; try running with -n option.'
    import __main__
    class_ = getattr(__main__, options.classname)
    proxy = class_((options.localhost, options.localport),
                   (options.remotehost, options.remoteport))
    except KeyboardInterrupt:

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