Wishful Coding

# Copyright (c) 2001-2004 Twisted Matrix Laboratories.
# See LICENSE for details.

# You can run this module directly with:
#    twistd -ny esmtpserver.tac


"""
A toy email server with authentication.
"""

from zope.interface import implements

from twisted.internet import defer
from twisted.mail import smtp
from twisted.mail.mail import MailService
# these challengers are located in imap4
from twisted.mail.imap4 import LOGINCredentials, PLAINCredentials

from twisted.cred.checkers import InMemoryUsernamePasswordDatabaseDontUse #except in examples and testing
from twisted.cred.portal import IRealm
from twisted.cred.portal import Portal

class ConsoleMessageDelivery:
    implements(smtp.IMessageDelivery)
    
    def receivedHeader(self, helo, origin, recipients):
        return "Received: ConsoleMessageDelivery"
    
    def validateFrom(self, helo, origin):
        # All addresses are accepted
        return origin
    
    def validateTo(self, user):
        # Only messages directed to the "console" user are accepted.
        if user.dest.local == "console":
            return lambda: ConsoleMessage()
        raise smtp.SMTPBadRcpt(user)

class ConsoleMessage:
    implements(smtp.IMessage)
    
    def __init__(self):
        self.lines = []
    
    def lineReceived(self, line):
        self.lines.append(line)
    
    def eomReceived(self):
        print "New message received:"
        print "\n".join(self.lines)
        self.lines = None
        return defer.succeed(None)
    
    def connectionLost(self):
        # There was an error, throw away the stored lines
        self.lines = None

class ConsoleSMTPFactory(smtp.SMTPFactory):
    def __init__(self, *a, **kw):
        smtp.SMTPFactory.__init__(self, *a, **kw)
        # make this factory make ESMTP servers
        self.protocol = smtp.ESMTP
    
    def buildProtocol(self, addr):
        p = smtp.SMTPFactory.buildProtocol(self, addr)
        # add the challengers from imap4, more secure and complicated challengers are available
        p.challengers = {"LOGIN": LOGINCredentials, "PLAIN": PLAINCredentials}
        return p

class SimpleRealm:
    implements(IRealm)

    def requestAvatar(self, avatarId, mind, *interfaces):
        # if we are authenticating a IMessageDelivery
        if smtp.IMessageDelivery in interfaces:
            # a tuple of the implemented interface, an instance implementing it and a logout callable
            return smtp.IMessageDelivery, ConsoleMessageDelivery(), lambda: None
        raise NotImplementedError()


def main():
    from twisted.application import internet
    from twisted.application import service    
    
    portal = Portal(SimpleRealm())
    # initiate a simple checker
    checker = InMemoryUsernamePasswordDatabaseDontUse()
    checker.addUser("guest", "password")
    portal.registerChecker(checker)
    
    a = service.Application("Console SMTP Server")
    internet.TCPServer(2500, ConsoleSMTPFactory(portal)).setServiceParent(a)
    
    return a

application = main()