Simple SMTP relay using Twisted API.

2 files changed, 126 insertions, 0 deletions

diff --git a/src/leap/email/smtp/__init__.py b/src/leap/email/smtp/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/leap/email/smtp/__init__.py
diff --git a/src/leap/email/smtp/smtprelay.py b/src/leap/email/smtp/smtprelay.py
new file mode 100644
index 00000000..10020a54
--- /dev/null
+++ b/src/leap/email/smtp/smtprelay.py
@@ -0,0 +1,126 @@
+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
+
+
+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 __init__(self):
+        self.gpgkey = ''
+
+    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, self.gpgkey)
+
+    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
+    recipients.
+    """
+    implements(smtp.IMessage)
+
+    SMTP_HOSTNAME = "mail.riseup.net"
+    SMTP_PORT     = 25
+
+    def __init__(self, user, gpgkey):
+        self.user = user
+        self.gpgkey = gpgkey
+        self.getSMTPInfo()
+        self.lines = []
+
+    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
+        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):
+        self.lines = [self.lines[0]] + \
+                     ["From: %s" % self.user.orig.addrstr] + \
+                     ["To: %s" % self.user.dest.addrstr] + \
+                     self.lines[1:]
+        msg = '\n'.join(self.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)
+        #reactor.run()
+        return d
+
+    
+    # this will be replaced by some other mechanism of obtaining credentials
+    # for SMTP server.
+    def getSMTPInfo(self):
+        f = open('/var/tmp/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()
+
+
+# run server
+if __name__ == "__main__":
+    import sys
+    reactor.listenTCP(25, SMTPFactory())
+    reactor.run()