Merge branch 'debian-0.3.8' into debian

9 files changed, 469 insertions, 117 deletions

diff --git a/src/leap/mail/_version.py b/src/leap/mail/_version.py
index caff696..7267b5b 100644
--- a/src/leap/mail/_version.py
+++ b/src/leap/mail/_version.py
@@ -5,8 +5,8 @@
 # unpacked source archive. Distribution tarballs contain a pre-generated copy
 # of this file.
 
-version_version = '0.3.7'
-version_full = 'e7945706608f5a75fe7baf9a3cb268ddb49773bc'
+version_version = '0.3.8'
+version_full = '790a6f3a5d2edeafcd1de8b4d2d32b861ef24a36'
 
 
 def get_versions(default={}, verbose=False):
diff --git a/src/leap/mail/imap/fetch.py b/src/leap/mail/imap/fetch.py
index 3422ed5..14f7a9b 100644
--- a/src/leap/mail/imap/fetch.py
+++ b/src/leap/mail/imap/fetch.py
@@ -22,8 +22,12 @@ import json
 import ssl
 import threading
 import time
+import copy
+from StringIO import StringIO
 
 from email.parser import Parser
+from email.generator import Generator
+from email.utils import parseaddr
 
 from twisted.python import log
 from twisted.internet.task import LoopingCall
@@ -57,7 +61,15 @@ class MalformedMessage(Exception):
 
 class LeapIncomingMail(object):
     """
-    Fetches mail from the incoming queue.
+    Fetches and process mail from the incoming pool.
+
+    This object has public methods start_loop and stop that will
+    actually initiate a LoopingCall with check_period recurrency.
+    The LoopingCall itself will invoke the fetch method each time
+    that the check_period expires.
+
+    This loop will sync the soledad db with the remote server and
+    process all the documents found tagged as incoming mail.
     """
 
     RECENT_FLAG = "\\Recent"
@@ -65,13 +77,23 @@ class LeapIncomingMail(object):
     INCOMING_KEY = "incoming"
     CONTENT_KEY = "content"
 
+    LEAP_SIGNATURE_HEADER = 'X-Leap-Signature'
+    """
+    Header added to messages when they are decrypted by the IMAP fetcher,
+    which states the validity of an eventual signature that might be included
+    in the encrypted blob.
+    """
+    LEAP_SIGNATURE_VALID = 'valid'
+    LEAP_SIGNATURE_INVALID = 'invalid'
+    LEAP_SIGNATURE_COULD_NOT_VERIFY = 'could not verify'
+
     fetching_lock = threading.Lock()
 
     def __init__(self, keymanager, soledad, imap_account,
                  check_period, userid):
 
         """
-        Initialize LeapIMAP.
+        Initialize LeapIncomingMail..
 
         :param keymanager: a keymanager instance
         :type keymanager: keymanager.KeyManager
@@ -148,6 +170,7 @@ class LeapIncomingMail(object):
             logger.warning("Tried to start an already running fetching loop.")
 
     def stop(self):
+        # XXX change the name to stop_loop, for consistency.
         """
         Stops the loop that fetches mail.
         """
@@ -171,7 +194,9 @@ class LeapIncomingMail(object):
         with self.fetching_lock:
             log.msg('syncing soledad...')
             self._soledad.sync()
+            log.msg('soledad synced.')
             doclist = self._soledad.get_from_index("just-mail", "*")
+
         return doclist
 
     def _signal_unread_to_ui(self):
@@ -235,6 +260,8 @@ class LeapIncomingMail(object):
         err = failure.value
         logger.error("error saving msg locally: %s" % (err,))
 
+    # process incoming mail.
+
     def _process_doclist(self, doclist):
         """
         Iterates through the doclist, checks if each doc
@@ -253,25 +280,21 @@ class LeapIncomingMail(object):
 
         docs_cb = []
         for index, doc in enumerate(doclist):
-            logger.debug("processing doc %d of %d" % (index, num_mails))
+            logger.debug("processing doc %d of %d" % (index + 1, num_mails))
             leap_events.signal(
                 IMAP_MSG_PROCESSING, str(index), str(num_mails))
             keys = doc.content.keys()
             if self._is_msg(keys):
                 # Ok, this looks like a legit msg.
                 # Let's process it!
-                encdata = doc.content[ENC_JSON_KEY]
-
                 # Deferred chain for individual messages
-                d = deferToThread(self._decrypt_msg, doc, encdata)
-                d.addCallback(self._process_decrypted)
+
+                # XXX use an IConsumer instead... ?
+                d = deferToThread(self._decrypt_doc, doc)
+                d.addCallback(self._process_decrypted_doc)
                 d.addErrback(self._log_err)
                 d.addCallback(self._add_message_locally)
                 d.addErrback(self._log_err)
-                # XXX check this, add_locally should not get called if we
-                # get an error in process
-                #d.addCallbacks(self._process_decrypted, self._decryption_error)
-                #d.addCallbacks(self._add_message_locally, self._saving_error)
                 docs_cb.append(d)
             else:
                 # Ooops, this does not.
@@ -293,34 +316,44 @@ class LeapIncomingMail(object):
         """
         return ENC_SCHEME_KEY in keys and ENC_JSON_KEY in keys
 
-    def _decrypt_msg(self, doc, encdata):
+    def _decrypt_doc(self, doc):
+        """
+        Decrypt the contents of a document.
+
+        :param doc: A document containing an encrypted message.
+        :type doc: SoledadDocument
+
+        :return: A tuple containing the document and the decrypted message.
+        :rtype: (SoledadDocument, str)
+        """
         log.msg('decrypting msg')
-        key = self._pkey
+        success = False
+
         try:
-            decrdata = (self._keymanager.decrypt(
-                encdata, key,
-                passphrase=self._soledad.passphrase))
-            ok = True
+            decrdata = self._keymanager.decrypt(
+                doc.content[ENC_JSON_KEY],
+                self._pkey)
+            success = True
         except Exception as exc:
             # XXX move this to errback !!!
-            logger.warning("Error while decrypting msg: %r" % (exc,))
+            logger.error("Error while decrypting msg: %r" % (exc,))
             decrdata = ""
-            ok = False
-        leap_events.signal(IMAP_MSG_DECRYPTED, "1" if ok else "0")
+        leap_events.signal(IMAP_MSG_DECRYPTED, "1" if success else "0")
         return doc, decrdata
 
-    def _process_decrypted(self, msgtuple):
+    def _process_decrypted_doc(self, msgtuple):
         """
-        Process a successfully decrypted message.
+        Process a document containing a succesfully decrypted message.
 
         :param msgtuple: a tuple consisting of a SoledadDocument
                          instance containing the incoming message
                          and data, the json-encoded, decrypted content of the
                          incoming message
         :type msgtuple: (SoledadDocument, str)
-        :returns: a SoledadDocument and the processed data.
+        :return: a SoledadDocument and the processed data.
         :rtype: (doc, data)
         """
+        log.msg('processing decrypted doc')
         doc, data = msgtuple
         msg = json.loads(data)
         if not isinstance(msg, dict):
@@ -332,14 +365,10 @@ class LeapIncomingMail(object):
         rawmsg = msg.get(self.CONTENT_KEY, None)
         if not rawmsg:
             return False
-        try:
-            data = self._maybe_decrypt_gpg_msg(rawmsg)
-            return doc, data
-        except keymanager_errors.EncryptionDecryptionFailed as exc:
-            logger.error(exc)
-            raise
+        data = self._maybe_decrypt_msg(rawmsg)
+        return doc, data
 
-    def _maybe_decrypt_gpg_msg(self, data):
+    def _maybe_decrypt_msg(self, data):
         """
         Tries to decrypt a gpg message if data looks like one.
 
@@ -348,80 +377,183 @@ class LeapIncomingMail(object):
         :return: data, possibly descrypted.
         :rtype: str
         """
-        # TODO split this method
+        log.msg('maybe decrypting doc')
         leap_assert_type(data, unicode)
 
+        # parse the original message
         parser = Parser()
         encoding = get_email_charset(data)
         data = data.encode(encoding)
-        origmsg = parser.parsestr(data)
-
-        # handle multipart/encrypted messages
-        if origmsg.get_content_type() == 'multipart/encrypted':
-            # sanity check
-            payload = origmsg.get_payload()
-            if len(payload) != 2:
-                raise MalformedMessage(
-                    'Multipart/encrypted messages should have exactly 2 body '
-                    'parts (instead of %d).' % len(payload))
-            if payload[0].get_content_type() != 'application/pgp-encrypted':
-                raise MalformedMessage(
-                    "Multipart/encrypted messages' first body part should "
-                    "have content type equal to 'application/pgp-encrypted' "
-                    "(instead of %s)." % payload[0].get_content_type())
-            if payload[1].get_content_type() != 'application/octet-stream':
-                raise MalformedMessage(
-                    "Multipart/encrypted messages' second body part should "
-                    "have content type equal to 'octet-stream' (instead of "
-                    "%s)." % payload[1].get_content_type())
-
-            # parse message and get encrypted content
-            pgpencmsg = origmsg.get_payload()[1]
-            encdata = pgpencmsg.get_payload()
-
-            # decrypt and parse decrypted message
-            decrdata = self._keymanager.decrypt(
-                encdata, self._pkey,
-                passphrase=self._soledad.passphrase)
+        msg = parser.parsestr(data)
+
+        # try to obtain sender public key
+        senderPubkey = None
+        fromHeader = msg.get('from', None)
+        if fromHeader is not None:
+            _, senderAddress = parseaddr(fromHeader)
             try:
-                decrdata = decrdata.encode(encoding)
-            except (UnicodeEncodeError, UnicodeDecodeError) as e:
-                logger.error("Unicode error {0}".format(e))
-                decrdata = decrdata.encode(encoding, 'replace')
-
-            decrmsg = parser.parsestr(decrdata)
-            # remove original message's multipart/encrypted content-type
-            del(origmsg['content-type'])
-            # replace headers back in original message
-            for hkey, hval in decrmsg.items():
-                try:
-                    # this will raise KeyError if header is not present
-                    origmsg.replace_header(hkey, hval)
-                except KeyError:
-                    origmsg[hkey] = hval
-
-            # replace payload by unencrypted payload
-            origmsg.set_payload(decrmsg.get_payload())
-            return origmsg.as_string(unixfrom=False)
+                senderPubkey = self._keymanager.get_key(
+                    senderAddress, OpenPGPKey)
+            except keymanager_errors.KeyNotFound:
+                pass
+
+        valid_sig = False  # we will add a header saying if sig is valid
+        if msg.get_content_type() == 'multipart/encrypted':
+            decrmsg, valid_sig = self._decrypt_multipart_encrypted_msg(
+                msg, encoding, senderPubkey)
         else:
-            PGP_BEGIN = "-----BEGIN PGP MESSAGE-----"
-            PGP_END = "-----END PGP MESSAGE-----"
-            # handle inline PGP messages
-            if PGP_BEGIN in data:
-                begin = data.find(PGP_BEGIN)
-                end = data.rfind(PGP_END)
-                pgp_message = data[begin:begin+end]
-                decrdata = (self._keymanager.decrypt(
-                    pgp_message, self._pkey,
-                    passphrase=self._soledad.passphrase))
+            decrmsg, valid_sig = self._maybe_decrypt_inline_encrypted_msg(
+                msg, encoding, senderPubkey)
+
+        # add x-leap-signature header
+        if senderPubkey is None:
+            decrmsg.add_header(
+                self.LEAP_SIGNATURE_HEADER,
+                self.LEAP_SIGNATURE_COULD_NOT_VERIFY)
+        else:
+            decrmsg.add_header(
+                self.LEAP_SIGNATURE_HEADER,
+                self.LEAP_SIGNATURE_VALID if valid_sig else
+                self.LEAP_SIGNATURE_INVALID,
+                pubkey=senderPubkey.key_id)
+
+        return decrmsg.as_string()
+
+    def _decrypt_multipart_encrypted_msg(self, msg, encoding, senderPubkey):
+        """
+        Decrypt a message with content-type 'multipart/encrypted'.
+
+        :param msg: The original encrypted message.
+        :type msg: Message
+        :param encoding: The encoding of the email message.
+        :type encoding: str
+        :param senderPubkey: The key of the sender of the message.
+        :type senderPubkey: OpenPGPKey
+
+        :return: A unitary tuple containing a decrypted message.
+        :rtype: (Message)
+        """
+        log.msg('decrypting multipart encrypted msg')
+        msg = copy.deepcopy(msg)
+        # sanity check
+        payload = msg.get_payload()
+        if len(payload) != 2:
+            raise MalformedMessage(
+                'Multipart/encrypted messages should have exactly 2 body '
+                'parts (instead of %d).' % len(payload))
+        if payload[0].get_content_type() != 'application/pgp-encrypted':
+            raise MalformedMessage(
+                "Multipart/encrypted messages' first body part should "
+                "have content type equal to 'application/pgp-encrypted' "
+                "(instead of %s)." % payload[0].get_content_type())
+        if payload[1].get_content_type() != 'application/octet-stream':
+            raise MalformedMessage(
+                "Multipart/encrypted messages' second body part should "
+                "have content type equal to 'octet-stream' (instead of "
+                "%s)." % payload[1].get_content_type())
+        # parse message and get encrypted content
+        pgpencmsg = msg.get_payload()[1]
+        encdata = pgpencmsg.get_payload()
+        # decrypt or fail gracefully
+        try:
+            decrdata, valid_sig = self._decrypt_and_verify_data(
+                encdata, senderPubkey)
+        except keymanager_errors.DecryptError as e:
+            logger.warning('Failed to decrypt encrypted message (%s). '
+                           'Storing message without modifications.' % str(e))
+            return msg, False  # return original message
+        # decrypted successully, now fix encoding and parse
+        try:
+            decrdata = decrdata.encode(encoding)
+        except (UnicodeEncodeError, UnicodeDecodeError) as e:
+            logger.error("Unicode error {0}".format(e))
+            decrdata = decrdata.encode(encoding, 'replace')
+        parser = Parser()
+        decrmsg = parser.parsestr(decrdata)
+        # remove original message's multipart/encrypted content-type
+        del(msg['content-type'])
+        # replace headers back in original message
+        for hkey, hval in decrmsg.items():
+            try:
+                # this will raise KeyError if header is not present
+                msg.replace_header(hkey, hval)
+            except KeyError:
+                msg[hkey] = hval
+        # replace payload by unencrypted payload
+        msg.set_payload(decrmsg.get_payload())
+        return msg, valid_sig
+
+    def _maybe_decrypt_inline_encrypted_msg(self, origmsg, encoding,
+                                            senderPubkey):
+        """
+        Possibly decrypt an inline OpenPGP encrypted message.
+
+        :param origmsg: The original, possibly encrypted message.
+        :type origmsg: Message
+        :param encoding: The encoding of the email message.
+        :type encoding: str
+        :param senderPubkey: The key of the sender of the message.
+        :type senderPubkey: OpenPGPKey
+
+        :return: A unitary tuple containing a decrypted message.
+        :rtype: (Message)
+        """
+        log.msg('maybe decrypting inline encrypted msg')
+        # serialize the original message
+        buf = StringIO()
+        g = Generator(buf)
+        g.flatten(origmsg)
+        data = buf.getvalue()
+        # handle exactly one inline PGP message
+        PGP_BEGIN = "-----BEGIN PGP MESSAGE-----"
+        PGP_END = "-----END PGP MESSAGE-----"
+        valid_sig = False
+        if PGP_BEGIN in data:
+            begin = data.find(PGP_BEGIN)
+            end = data.find(PGP_END)
+            pgp_message = data[begin:end+len(PGP_END)]
+            try:
+                decrdata, valid_sig = self._decrypt_and_verify_data(
+                    pgp_message, senderPubkey)
                 # replace encrypted by decrypted content
                 data = data.replace(pgp_message, decrdata)
+            except keymanager_errors.DecryptError:
+                logger.warning('Failed to decrypt potential inline encrypted '
+                               'message. Storing message as is...')
         # if message is not encrypted, return raw data
-
         if isinstance(data, unicode):
             data = data.encode(encoding, 'replace')
+        parser = Parser()
+        return parser.parsestr(data), valid_sig
 
-        return data
+    def _decrypt_and_verify_data(self, data, senderPubkey):
+        """
+        Decrypt C{data} using our private key and attempt to verify a
+        signature using C{senderPubkey}.
+
+        :param data: The text to be decrypted.
+        :type data: unicode
+        :param senderPubkey: The public key of the sender of the message.
+        :type senderPubkey: OpenPGPKey
+
+        :return: The decrypted data and a boolean stating whether the
+                 signature could be verified.
+        :rtype: (str, bool)
+
+        :raise DecryptError: Raised if failed to decrypt.
+        """
+        log.msg('decrypting and verifying data')
+        valid_sig = False
+        try:
+            decrdata = self._keymanager.decrypt(
+                data, self._pkey,
+                verify=senderPubkey)
+            if senderPubkey is not None:
+                valid_sig = True
+        except keymanager_errors.InvalidSignature:
+            decrdata = self._keymanager.decrypt(
+                data, self._pkey)
+        return decrdata, valid_sig
 
     def _add_message_locally(self, msgtuple):
         """
@@ -434,6 +566,7 @@ class LeapIncomingMail(object):
                          incoming message
         :type msgtuple: (SoledadDocument, str)
         """
+        log.msg('adding message to local db')
         doc, data = msgtuple
         self._inbox.addMessage(data, (self.RECENT_FLAG,))
         leap_events.signal(IMAP_MSG_SAVED_LOCALLY)
diff --git a/src/leap/mail/imap/server.py b/src/leap/mail/imap/server.py
index bb2830d..6320a51 100644
--- a/src/leap/mail/imap/server.py
+++ b/src/leap/mail/imap/server.py
@@ -27,6 +27,7 @@ from collections import defaultdict
 from email.parser import Parser
 
 from zope.interface import implements
+from zope.proxy import sameProxiedObjects
 
 from twisted.mail import imap4
 from twisted.internet import defer
@@ -36,6 +37,7 @@ from leap.common import events as leap_events
 from leap.common.events.events_pb2 import IMAP_UNREAD_MAIL
 from leap.common.check import leap_assert, leap_assert_type
 from leap.common.mail import get_email_charset
+from leap.mail.messageflow import IMessageConsumer, MessageProducer
 from leap.soledad.client import Soledad
 
 logger = logging.getLogger(__name__)
@@ -816,6 +818,32 @@ class LeapMessage(WithMsgFields):
         return self._doc.content.get(key, None)
 
 
+class SoledadDocWriter(object):
+    """
+    This writer will create docs serially in the local soledad database.
+    """
+
+    implements(IMessageConsumer)
+
+    def __init__(self, soledad):
+        """
+        Initialize the writer.
+
+        :param soledad: the soledad instance
+        :type soledad: Soledad
+        """
+        self._soledad = soledad
+
+    def consume(self, item):
+        """
+        Creates a new document in soledad db.
+
+        :param item: object to update. content of the document to be inserted.
+        :type item: dict
+        """
+        self._soledad.create_doc(item)
+
+
 class MessageCollection(WithMsgFields, IndexedDB):
     """
     A collection of messages, surprisingly.
@@ -875,6 +903,16 @@ class MessageCollection(WithMsgFields, IndexedDB):
         self.initialize_db()
         self._parser = Parser()
 
+        # I think of someone like nietzsche when reading this
+
+        # this will be the producer that will enqueue the content
+        # to be processed serially by the consumer (the writer). We just
+        # need to `put` the new material on its plate.
+
+        self._soledad_writer = MessageProducer(
+            SoledadDocWriter(soledad),
+            period=0.2)
+
     def _get_empty_msg(self):
         """
         Returns an empty message.
@@ -947,7 +985,9 @@ class MessageCollection(WithMsgFields, IndexedDB):
         # ...should get a sanity check here.
         content[self.UID_KEY] = uid
 
-        return self._soledad.create_doc(content)
+        self._soledad_writer.put(content)
+        # XXX have to decide what shall we do with errors with this change...
+        #return self._soledad.create_doc(content)
 
     def remove(self, msg):
         """
@@ -1041,7 +1081,11 @@ class MessageCollection(WithMsgFields, IndexedDB):
         :return: a list of u1db documents
         :rtype: list of SoledadDocument
         """
-        # XXX this should return LeapMessage instances
+        if sameProxiedObjects(self._soledad, None):
+            logger.warning('Tried to get messages but soledad is None!')
+            return []
+
+        #f XXX this should return LeapMessage instances
         all_docs = [doc for doc in self._soledad.get_from_index(
             SoledadBackedAccount.TYPE_MBOX_IDX,
             self.TYPE_MESSAGE_VAL, self.mbox)]
@@ -1438,12 +1482,14 @@ class SoledadMailbox(WithMsgFields):
         """
         # XXX we should treat the message as an IMessage from here
         uid_next = self.getUIDNext()
-        flags = tuple(str(flag) for flag in flags)
+        if flags is None:
+            flags = tuple()
+        else:
+            flags = tuple(str(flag) for flag in flags)
 
         self.messages.add_msg(message, flags=flags, date=date,
                               uid=uid_next)
 
-        # XXX recent should not include deleted...??
         exists = len(self.messages)
         recent = len(self.messages.get_recent())
         for listener in self.listeners:
@@ -1512,7 +1558,10 @@ class SoledadMailbox(WithMsgFields):
             except TypeError:
                 # looks like we cannot iterate
                 last = self.messages.get_last()
-                uid_last = last.getUID()
+                if last is None:
+                    uid_last = 1
+                else:
+                    uid_last = last.getUID()
                 messages.last = uid_last
 
         # for sequence numbers (uid = 0)
diff --git a/src/leap/mail/imap/service/imap.py b/src/leap/mail/imap/service/imap.py
index feb2593..8756ddc 100644
--- a/src/leap/mail/imap/service/imap.py
+++ b/src/leap/mail/imap/service/imap.py
@@ -41,7 +41,7 @@ IMAP_PORT = 1984
 
 # The period between succesive checks of the incoming mail
 # queue (in seconds)
-INCOMING_CHECK_PERIOD = 300
+INCOMING_CHECK_PERIOD = 60
 
 from leap.common.events.events_pb2 import IMAP_SERVICE_STARTED
 from leap.common.events.events_pb2 import IMAP_SERVICE_FAILED_TO_START
diff --git a/src/leap/mail/imap/tests/test_imap.py b/src/leap/mail/imap/tests/test_imap.py
index ad11315..ca73a11 100644
--- a/src/leap/mail/imap/tests/test_imap.py
+++ b/src/leap/mail/imap/tests/test_imap.py
@@ -923,7 +923,6 @@ class LeapIMAP4ServerTestCase(IMAP4HelperMixin, unittest.TestCase):
         """
         self.server.theAccount.addMailbox('test-mailbox-e',
                                           creation_ts=42)
-        #import ipdb; ipdb.set_trace()
 
         self.examinedArgs = None
 
@@ -1108,16 +1107,15 @@ class LeapIMAP4ServerTestCase(IMAP4HelperMixin, unittest.TestCase):
         mb = SimpleLEAPServer.theAccount.getMailbox('ROOT/SUBTHING')
         self.assertEqual(1, len(mb.messages))
 
-        #import ipdb; ipdb.set_trace()
         self.assertEqual(
             ['\\SEEN', '\\DELETED'],
-            mb.messages[1]['flags'])
+            mb.messages[1].content['flags'])
 
         self.assertEqual(
             'Tue, 17 Jun 2003 11:22:16 -0600 (MDT)',
-            mb.messages[1]['date'])
+            mb.messages[1].content['date'])
 
-        self.assertEqual(open(infile).read(), mb.messages[1]['raw'])
+        self.assertEqual(open(infile).read(), mb.messages[1].content['raw'])
 
     def testPartialAppend(self):
         """
@@ -1152,11 +1150,11 @@ class LeapIMAP4ServerTestCase(IMAP4HelperMixin, unittest.TestCase):
         self.assertEqual(1, len(mb.messages))
         self.assertEqual(
             ['\\SEEN',],
-            mb.messages[1]['flags']
+            mb.messages[1].content['flags']
         )
         self.assertEqual(
-            'Right now', mb.messages[1]['date'])
-        self.assertEqual(open(infile).read(), mb.messages[1]['raw'])
+            'Right now', mb.messages[1].content['date'])
+        self.assertEqual(open(infile).read(), mb.messages[1].content['raw'])
 
     def testCheck(self):
         """
@@ -1214,7 +1212,7 @@ class LeapIMAP4ServerTestCase(IMAP4HelperMixin, unittest.TestCase):
     def _cbTestClose(self, ignored, m):
         self.assertEqual(len(m.messages), 1)
         self.assertEqual(
-            m.messages[1]['subject'],
+            m.messages[1].content['subject'],
             'Message 2')
 
         self.failUnless(m.closed)
@@ -1257,7 +1255,7 @@ class LeapIMAP4ServerTestCase(IMAP4HelperMixin, unittest.TestCase):
     def _cbTestExpunge(self, ignored, m):
         self.assertEqual(len(m.messages), 1)
         self.assertEqual(
-            m.messages[1]['subject'],
+            m.messages[1].content['subject'],
             'Message 2')
         self.assertEqual(self.results, [0, 1])
         # XXX fix this thing with the indexes...
diff --git a/src/leap/mail/messageflow.py b/src/leap/mail/messageflow.py
new file mode 100644
index 0000000..21f6d62
--- /dev/null
+++ b/src/leap/mail/messageflow.py
@@ -0,0 +1,149 @@
+# -*- coding: utf-8 -*-
+# messageflow.py
+# Copyright (C) 2013 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+Message Producers and Consumers for flow control.
+"""
+import Queue
+
+from twisted.internet.task import LoopingCall
+
+from zope.interface import Interface, implements
+
+
+class IMessageConsumer(Interface):
+
+    def consume(self, item):
+        """
+        Consumes the passed item.
+
+        :param item: an object to be consumed.
+        :type item: object
+        """
+        # TODO we could add an optional type to be passed
+        # for doing type check.
+
+        # TODO in case of errors, we could return the object to
+        # the queue, maybe wrapped in an object with a retries attribute.
+
+
+class DummyMsgConsumer(object):
+
+    implements(IMessageConsumer)
+
+    def consume(self, item):
+        """
+        Just prints the passed item.
+        """
+        print "got item %s" % item
+
+
+class MessageProducer(object):
+    """
+    A Producer class that we can use to temporarily buffer the production
+    of messages so that different objects can consume them.
+
+    This is useful for serializing the consumption of the messages stream
+    in the case of an slow resource (db), or for returning early from a
+    deferred chain and leave further processing detached from the calling loop,
+    as in the case of smtp.
+    """
+    # TODO this can be seen as a first step towards properly implementing
+    # components that implement IPushProducer / IConsumer  interfaces.
+    # However, I need to think more about how to pause the streaming.
+    # In any case, the differential rate between message production
+    # and consumption is not likely (?) to consume huge amounts of memory in
+    # our current settings, so the need to pause the stream is not urgent now.
+
+    def __init__(self, consumer, queue=Queue.Queue, period=1):
+        """
+        Initializes the MessageProducer
+
+        :param consumer: an instance of a IMessageConsumer that will consume
+                         the new messages.
+        :param queue: any queue implementation to be used as the temporary
+                      buffer for new items. Default is a FIFO Queue.
+        :param period: the period to check for new items, in seconds.
+        """
+        # XXX should assert it implements IConsumer / IMailConsumer
+        # it should implement a `consume` method
+        self._consumer = consumer
+
+        self._queue = queue()
+        self._period = period
+
+        self._loop = LoopingCall(self._check_for_new)
+
+    # private methods
+
+    def _check_for_new(self):
+        """
+        Checks for new items in the internal queue, and calls the consume
+        method in the consumer.
+
+        If the queue is found empty, the loop is stopped. It will be started
+        again after the addition of new items.
+        """
+        # XXX right now I'm assuming that the period is good enough to allow
+        # a right pace of processing. but we could also pass the queue object
+        # to the consumer and let it choose whether process a new item or not.
+
+        if self._queue.empty():
+            self.stop()
+        else:
+            self._consumer.consume(self._queue.get())
+
+    # public methods
+
+    def put(self, item):
+        """
+        Puts a new item in the queue.
+
+        If the queue was empty, we will start the loop again.
+        """
+        was_empty = self._queue.empty()
+
+        # XXX this might raise if the queue does not accept any new
+        # items. what to do then?
+        self._queue.put(item)
+        if was_empty:
+            self.start()
+
+    def start(self):
+        """
+        Starts polling for new items.
+        """
+        if not self._loop.running:
+            self._loop.start(self._period)
+
+    def stop(self):
+        """
+        Stop polling for new items.
+        """
+        if self._loop.running:
+            self._loop.stop()
+
+
+if __name__ == "__main__":
+    from twisted.internet import reactor
+    producer = MessageProducer(DummyMsgConsumer())
+    producer.start()
+
+    for delay, item in ((2, 1), (3, 2), (4, 3),
+                        (6, 4), (7, 5), (8, 6), (8.2, 7),
+                        (15, 'a'), (16, 'b'), (17, 'c')):
+        reactor.callLater(delay, producer.put, item)
+    reactor.run()
diff --git a/src/leap/mail/smtp/gateway.py b/src/leap/mail/smtp/gateway.py
index f09ee14..a78bd55 100644
--- a/src/leap/mail/smtp/gateway.py
+++ b/src/leap/mail/smtp/gateway.py
@@ -333,6 +333,8 @@ class EncryptedMessage(object):
     """
     implements(smtp.IMessage)
 
+    FOOTER_STRING = "I prefer encrypted email"
+
     def __init__(self, fromAddress, user, keymanager, host, port, cert, key):
         """
         Initialize the encrypted message.
@@ -597,7 +599,16 @@ class EncryptedMessage(object):
             self._msg = self._origmsg
             return
 
+        # add a nice footer to the outgoing message
         from_address = validate_address(self._fromAddress.addrstr)
+        username, domain = from_address.split('@')
+        self.lines.append('--')
+        self.lines.append('%s - https://%s/key/%s.' %
+                          (self.FOOTER_STRING, domain, username))
+        self.lines.append('')
+        self._origmsg = self.parseMessage()
+
+        # get sender and recipient data
         signkey = self._km.get_key(from_address, OpenPGPKey, private=True)
         log.msg("Will sign the message with %s." % signkey.fingerprint)
         to_address = validate_address(self._user.dest.addrstr)
@@ -672,6 +683,7 @@ class EncryptedMessage(object):
         username, domain = signkey.address.split('@')
         newmsg.add_header(
             'OpenPGP', 'id=%s' % signkey.key_id,
-            url='https://%s/openpgp/%s' % (domain, username))
+            url='https://%s/key/%s' % (domain, username),
+            preference='signencrypt')
         # delete user-agent from origmsg
         del(origmsg['user-agent'])
diff --git a/src/leap/mail/smtp/tests/__init__.py b/src/leap/mail/smtp/tests/__init__.py
index 62b015f..1459cea 100644
--- a/src/leap/mail/smtp/tests/__init__.py
+++ b/src/leap/mail/smtp/tests/__init__.py
@@ -115,8 +115,8 @@ class TestCaseWithKeyManager(BaseLeapTest):
             'username': address,
             'password': '<password>',
             'encrypted_only': True,
-            'cert': 'src/leap/mail/smtp/tests/cert/server.crt',
-            'key': 'src/leap/mail/smtp/tests/cert/server.key',
+            'cert': u'src/leap/mail/smtp/tests/cert/server.crt',
+            'key': u'src/leap/mail/smtp/tests/cert/server.key',
         }
 
         class Response(object):
diff --git a/src/leap/mail/smtp/tests/test_gateway.py b/src/leap/mail/smtp/tests/test_gateway.py
index f9ea027..4c2f04f 100644
--- a/src/leap/mail/smtp/tests/test_gateway.py
+++ b/src/leap/mail/smtp/tests/test_gateway.py
@@ -22,7 +22,6 @@ SMTP gateway tests.
 
 
 import re
-
 from datetime import datetime
 from gnupg._util import _make_binary_stream
 from twisted.test import proto_helpers
@@ -131,6 +130,9 @@ class TestSmtpGateway(TestCaseWithKeyManager):
         for line in self.EMAIL_DATA[4:12]:
             m.lineReceived(line)
         m.eomReceived()
+        # we need to call the following explicitelly because it was deferred
+        # inside the previous method
+        m._maybe_encrypt_and_sign()
         # assert structure of encrypted message
         self.assertTrue('Content-Type' in m._msg)
         self.assertEqual('multipart/encrypted', m._msg.get_content_type())
@@ -146,7 +148,8 @@ class TestSmtpGateway(TestCaseWithKeyManager):
         decrypted = self._km.decrypt(
             m._msg.get_payload(1).get_payload(), privkey)
         self.assertEqual(
-            '\n' + '\r\n'.join(self.EMAIL_DATA[9:12]) + '\r\n',
+            '\n' + '\r\n'.join(self.EMAIL_DATA[9:12]) + '\r\n\r\n--\r\n' +
+            'I prefer encrypted email - https://leap.se/key/anotheruser.\r\n',
             decrypted,
             'Decrypted text differs from plaintext.')
 
@@ -168,6 +171,9 @@ class TestSmtpGateway(TestCaseWithKeyManager):
             m.lineReceived(line)
         # trigger encryption and signing
         m.eomReceived()
+        # we need to call the following explicitelly because it was deferred
+        # inside the previous method
+        m._maybe_encrypt_and_sign()
         # assert structure of encrypted message
         self.assertTrue('Content-Type' in m._msg)
         self.assertEqual('multipart/encrypted', m._msg.get_content_type())
@@ -185,7 +191,8 @@ class TestSmtpGateway(TestCaseWithKeyManager):
         decrypted = self._km.decrypt(
             m._msg.get_payload(1).get_payload(), privkey, verify=pubkey)
         self.assertEqual(
-            '\n' + '\r\n'.join(self.EMAIL_DATA[9:12]) + '\r\n',
+            '\n' + '\r\n'.join(self.EMAIL_DATA[9:12]) + '\r\n\r\n--\r\n' +
+            'I prefer encrypted email - https://leap.se/key/anotheruser.\r\n',
             decrypted,
             'Decrypted text differs from plaintext.')
 
@@ -208,6 +215,9 @@ class TestSmtpGateway(TestCaseWithKeyManager):
             m.lineReceived(line)
         # trigger signing
         m.eomReceived()
+        # we need to call the following explicitelly because it was deferred
+        # inside the previous method
+        m._maybe_encrypt_and_sign()
         # assert structure of signed message
         self.assertTrue('Content-Type' in m._msg)
         self.assertEqual('multipart/signed', m._msg.get_content_type())
@@ -216,8 +226,9 @@ class TestSmtpGateway(TestCaseWithKeyManager):
         self.assertEqual('pgp-sha512', m._msg.get_param('micalg'))
         # assert content of message
         self.assertEqual(
-            m._msg.get_payload(0).get_payload(decode=True),
-            '\r\n'.join(self.EMAIL_DATA[9:13]))
+            '\r\n'.join(self.EMAIL_DATA[9:13])+'\r\n--\r\n' +
+            'I prefer encrypted email - https://leap.se/key/anotheruser.\r\n',
+            m._msg.get_payload(0).get_payload(decode=True))
         # assert content of signature
         self.assertTrue(
             m._msg.get_payload(1).get_payload().startswith(