From 196ec0e1eefbd50860771de0c8d2b488c30c6506 Mon Sep 17 00:00:00 2001
From: drebs <drebs@leap.se>
Date: Wed, 31 Oct 2012 11:57:08 -0200
Subject: relay loops forever with twistd

---
 src/leap/email/smtp/smtprelay.tac | 159 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 src/leap/email/smtp/smtprelay.tac

(limited to 'src/leap/email/smtp/smtprelay.tac')

diff --git a/src/leap/email/smtp/smtprelay.tac b/src/leap/email/smtp/smtprelay.tac
new file mode 100644
index 00000000..b05edb7f
--- /dev/null
+++ b/src/leap/email/smtp/smtprelay.tac
@@ -0,0 +1,159 @@
+import re
+import gnupg
+from zope.interface import implements
+from StringIO import StringIO
+from twisted.mail import smtp
+from twisted.internet.protocol import ServerFactory
+from twisted.internet import reactor
+from twisted.internet import defer
+from twisted.application import internet, service
+from email.Header import Header
+
+
+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
+        self.lines = []
+
+    def sendSuccess(self, r):
+        print r
+
+    def sendError(self, e):
+        print e
+
+    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)
+        print "Encrypting to %s" % fp
+        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)
+
+
+# service configuration
+port = 25
+factory = SMTPFactory()
+
+# this enables the use of this application with twistd
+application = service.Application("LEAP SMTP Relay")  # create the Application
+service = internet.TCPServer(port, factory) # create the service
+# add the service to the application
+service.setServiceParent(application)
-- 
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