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from zope.interface import implements
from twisted.mail import smtp
from twisted.internet.protocol import ServerFactory
from twisted.internet import reactor
from twisted.internet import defer
from email.Header import Header
from StringIO import StringIO
import gnupg
import re
class SMTPFactory(ServerFactory):
"""
Factory for an SMTP server with encrypted relaying capabilities.
"""
def buildProtocol(self, addr):
"Return a protocol suitable for the job."
smtpProtocol = smtp.SMTP(SMTPDelivery())
smtpProtocol.factory = self
return smtpProtocol
class SMTPDelivery(object):
"""
Validate email addresses and handle message delivery.
"""
implements(smtp.IMessageDelivery)
def receivedHeader(self, helo, origin, recipients):
myHostname, clientIP = helo
headerValue = "by %s from %s with ESMTP ; %s" % (
myHostname, clientIP, smtp.rfc822date( ))
# email.Header.Header used for automatic wrapping of long lines
return "Received: %s" % Header(headerValue)
def validateTo(self, user):
"""Assert existence of GPG public key for a recipient."""
# for now just accept any receipient
print "Accepting mail for %s..." % user.dest
return lambda: EncryptedMessage(user)
def validateFrom(self, helo, originAddress):
# accept mail from anywhere. To reject an address, raise
# smtp.SMTPBadSender here.
return originAddress
class EncryptedMessage():
"""
Receive plaintext from client, encrypt it and send message to a
recipient.
"""
implements(smtp.IMessage)
SMTP_HOSTNAME = "mail.riseup.net"
SMTP_PORT = 25
def __init__(self, user):
self.user = user
self.getSMTPInfo()
self.lines = []
self.gpg = GPGWrapper()
def lineReceived(self, line):
"""Store email DATA lines as they arrive."""
self.lines.append(line)
def eomReceived(self):
"""Encrypt and send message."""
print "Message data complete."
self.lines.append('') # add a trailing newline
self.received = self.lines[0]
self.lines = self.lines[1:]
self.encrypt()
return self.sendMail()
def connectionLost(self):
print "Connection lost unexpectedly!"
# unexpected loss of connection; don't save
del(self.lines)
def sendSuccess(self, r):
print r
reactor.stop()
def sendError(self, e):
print e
reactor.stop()
def sendMail(self):
lines = [self.received] + \
["From: %s" % self.user.orig.addrstr] + \
["To: %s" % self.user.dest.addrstr] + \
[self.cyphertext]
msg = '\n'.join(lines)
d = defer.Deferred()
factory = smtp.ESMTPSenderFactory(self.smtp_username,
self.smtp_password,
self.smtp_username,
self.user.dest.addrstr,
StringIO(msg),
d)
# the next call is TSL-powered!
reactor.connectTCP(self.SMTP_HOSTNAME, self.SMTP_PORT, factory)
d.addCallback(self.sendSuccess)
d.addErrback(self.sendError)
return d
def encrypt(self):
fp = self.gpg.get_fingerprint(self.user.dest.addrstr)
self.cyphertext = str(self.gpg.encrypt('\n'.join(self.lines), [fp]))
# this will be replaced by some other mechanism of obtaining credentials
# for SMTP server.
def getSMTPInfo(self):
f = open('/media/smtp-info.txt', 'r')
self.smtp_host = f.readline().rstrip()
self.smtp_port = f.readline().rstrip()
self.smtp_username = f.readline().rstrip()
self.smtp_password = f.readline().rstrip()
f.close()
class GPGWrapper():
"""
This is a temporary class for handling GPG requests, and should be
replaced by a more general class used throughout the project.
"""
GNUPG_HOME = "~/.config/leap/gnupg"
GNUPG_BINARY = "/usr/bin/gpg" # this has to be changed based on OS
def __init__(self):
self.gpg = gnupg.GPG(gnupghome=self.GNUPG_HOME, gpgbinary=self.GNUPG_BINARY)
def get_fingerprint(self, email):
"""
Find user's fingerprint based on their email.
"""
for key in self.gpg.list_keys():
for uid in key['uids']:
if re.search(email, uid):
return key['fingerprint']
def encrypt(self, data, recipient):
return self.gpg.encrypt(data, recipient)
# run server
if __name__ == "__main__":
import sys
reactor.listenTCP(2500, SMTPFactory())
reactor.run()
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