Mini Shell

# -*- test-case-name: twisted.mail.test.test_mail -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Support for relaying mail.
"""

import os
import pickle

from twisted.internet.address import UNIXAddress
from twisted.mail import smtp
from twisted.python import log


class DomainQueuer:
    """
    An SMTP domain which add messages to a queue intended for relaying.
    """

    def __init__(self, service, authenticated=False):
        self.service = service
        self.authed = authenticated

    def exists(self, user):
        """
        Check whether mail can be relayed to a user.

        @type user: L{User}
        @param user: A user.

        @rtype: no-argument callable which returns L{IMessage <smtp.IMessage>}
            provider
        @return: A function which takes no arguments and returns a message
            receiver for the user.

        @raise SMTPBadRcpt: When mail cannot be relayed to the user.
        """
        if self.willRelay(user.dest, user.protocol):
            # The most cursor form of verification of the addresses
            orig = filter(None, str(user.orig).split("@", 1))
            dest = filter(None, str(user.dest).split("@", 1))
            if len(orig) == 2 and len(dest) == 2:
                return lambda: self.startMessage(user)
        raise smtp.SMTPBadRcpt(user)

    def willRelay(self, address, protocol):
        """
        Check whether we agree to relay.

        The default is to relay for all connections over UNIX
        sockets and all connections from localhost.
        """
        peer = protocol.transport.getPeer()
        return self.authed or isinstance(peer, UNIXAddress) or peer.host == "127.0.0.1"

    def startMessage(self, user):
        """
        Create an envelope and a message receiver for the relay queue.

        @type user: L{User}
        @param user: A user.

        @rtype: L{IMessage <smtp.IMessage>}
        @return: A message receiver.
        """
        queue = self.service.queue
        envelopeFile, smtpMessage = queue.createNewMessage()
        with envelopeFile:
            log.msg(f"Queueing mail {str(user.orig)!r} -> {str(user.dest)!r}")
            pickle.dump([str(user.orig), str(user.dest)], envelopeFile)
        return smtpMessage


class RelayerMixin:

    # XXX - This is -totally- bogus
    # It opens about a -hundred- -billion- files
    # and -leaves- them open!

    def loadMessages(self, messagePaths):
        self.messages = []
        self.names = []
        for message in messagePaths:
            with open(message + "-H", "rb") as fp:
                messageContents = pickle.load(fp)
            fp = open(message + "-D")
            messageContents.append(fp)
            self.messages.append(messageContents)
            self.names.append(message)

    def getMailFrom(self):
        if not self.messages:
            return None
        return self.messages[0][0]

    def getMailTo(self):
        if not self.messages:
            return None
        return [self.messages[0][1]]

    def getMailData(self):
        if not self.messages:
            return None
        return self.messages[0][2]

    def sentMail(self, code, resp, numOk, addresses, log):
        """Since we only use one recipient per envelope, this
        will be called with 0 or 1 addresses. We probably want
        to do something with the error message if we failed.
        """
        if code in smtp.SUCCESS:
            # At least one, i.e. all, recipients successfully delivered
            os.remove(self.names[0] + "-D")
            os.remove(self.names[0] + "-H")
        del self.messages[0]
        del self.names[0]


class SMTPRelayer(RelayerMixin, smtp.SMTPClient):
    """
    A base class for SMTP relayers.
    """

    def __init__(self, messagePaths, *args, **kw):
        """
        @type messagePaths: L{list} of L{bytes}
        @param messagePaths: The base filename for each message to be relayed.

        @type args: 1-L{tuple} of (0) L{bytes} or 2-L{tuple} of
            (0) L{bytes}, (1) L{int}
        @param args: Positional arguments for L{SMTPClient.__init__}

        @type kw: L{dict}
        @param kw: Keyword arguments for L{SMTPClient.__init__}
        """
        smtp.SMTPClient.__init__(self, *args, **kw)
        self.loadMessages(messagePaths)


class ESMTPRelayer(RelayerMixin, smtp.ESMTPClient):
    """
    A base class for ESMTP relayers.
    """

    def __init__(self, messagePaths, *args, **kw):
        """
        @type messagePaths: L{list} of L{bytes}
        @param messagePaths: The base filename for each message to be relayed.

        @type args: 3-L{tuple} of (0) L{bytes}, (1) L{None} or
            L{ClientContextFactory
            <twisted.internet.ssl.ClientContextFactory>},
            (2) L{bytes} or 4-L{tuple} of (0) L{bytes}, (1) L{None}
            or L{ClientContextFactory
            <twisted.internet.ssl.ClientContextFactory>}, (2) L{bytes},
            (3) L{int}
        @param args: Positional arguments for L{ESMTPClient.__init__}

        @type kw: L{dict}
        @param kw: Keyword arguments for L{ESMTPClient.__init__}
        """
        smtp.ESMTPClient.__init__(self, *args, **kw)
        self.loadMessages(messagePaths)