Merge tag '0.6.2'

Tag leap.mx version 0.6.2

6 files changed, 766 insertions, 290 deletions

diff --git a/src/leap/mx/alias_resolver.py b/src/leap/mx/alias_resolver.py
index 45a3ed2..c6f2acc 100644
--- a/src/leap/mx/alias_resolver.py
+++ b/src/leap/mx/alias_resolver.py
@@ -19,73 +19,62 @@
 """
 Classes for resolving postfix aliases.
 
+The resolver is queried by the mail server before delivery to the mail spool
+directory, and should return the user uuid. This way, we get rid from the user
+address early and the mail server will delivery the message to
+"<uuid>@<domain>". Later, the mail receiver part of MX will parse the
+"Delivered-To" header to extract the uuid and fetch the user's pgp public key.
+
 Test this with postmap -v -q "foo" tcp:localhost:4242
 
 TODO:
     o Look into using twisted.protocols.postfix.policies classes for
       controlling concurrent connections and throttling resource consumption.
+    o We should probably use twisted.mail.alias somehow.
 """
 
-try:
-    # TODO: we should probably use the system alias somehow
-    # from twisted.mail      import alias
-    from twisted.protocols import postfix
-    from twisted.python import log
-    from twisted.internet import defer
-except ImportError:
-    print "This software requires Twisted. Please see the README file"
-    print "for instructions on getting required dependencies."
-
 
-class LEAPPostFixTCPMapserver(postfix.PostfixTCPMapServer):
-    def _cbGot(self, value):
-        if value is None:
-            self.sendCode(500, postfix.quote("NOT FOUND SRY"))
-        else:
-            self.sendCode(200, postfix.quote(value))
+from twisted.protocols import postfix
 
+from leap.mx.tcp_map import LEAPPostfixTCPMapServerFactory
+from leap.mx.tcp_map import TCP_MAP_CODE_SUCCESS
+from leap.mx.tcp_map import TCP_MAP_CODE_PERMANENT_FAILURE
 
-class AliasResolverFactory(postfix.PostfixTCPMapDeferringDictServerFactory):
 
-    protocol = LEAPPostFixTCPMapserver
+class LEAPPostfixTCPMapAliasServer(postfix.PostfixTCPMapServer):
+    """
+    A postfix tcp map alias resolver server.
+    """
 
-    def __init__(self, couchdb, *args, **kwargs):
-        postfix.PostfixTCPMapDeferringDictServerFactory.__init__(
-            self, *args, **kwargs)
-        self._cdb = couchdb
-
-    def _to_str(self, result):
-        """
-        Properly encodes the result string if any.
+    def _cbGot(self, user_data):
         """
-        if isinstance(result, unicode):
-            result = result.encode("utf8")
-        if result is None:
-            log.msg("Result not found")
-        return result
+        Return a code and message depending on the result of the factory's
+        get().
 
-    def spit_result(self, result):
+        :param user_data: The user's uuid and pgp public key.
+        :type user_data: list
         """
-        Formats the return codes in a postfix friendly format.
-        """
-        if result is None:
-            return None
+        uuid, _ = user_data
+        if uuid is None:
+            self.sendCode(
+                TCP_MAP_CODE_PERMANENT_FAILURE,
+                postfix.quote("NOT FOUND SRY"))
         else:
-            return defer.succeed(result)
+            # properly encode uuid, otherwise twisted complains when replying
+            if isinstance(uuid, unicode):
+                uuid = uuid.encode("utf8")
+            self.sendCode(
+                TCP_MAP_CODE_SUCCESS,
+                postfix.quote(uuid))
 
-    def get(self, key):
-        """
-        Looks up the passed key, but only up to the username id of the key.
 
-        At some point we will have to consider the domain part too.
-        """
-        try:
-            log.msg("Query key: %s" % (key,))
-            d = self._cdb.queryByAddress(key)
+class AliasResolverFactory(LEAPPostfixTCPMapServerFactory):
+    """
+    A factory for postfix tcp map alias resolver servers.
+    """
+
+    protocol = LEAPPostfixTCPMapAliasServer
 
-            d.addCallback(self._to_str)
-            d.addCallback(self.spit_result)
-            d.addErrback(log.err)
-            return d
-        except Exception as e:
-            log.err('exception in get: %r' % e)
+    @property
+    def _query_message(self):
+        return "Resolving alias for"
diff --git a/src/leap/mx/bounce.py b/src/leap/mx/bounce.py
new file mode 100644
index 0000000..2ece6df
--- /dev/null
+++ b/src/leap/mx/bounce.py
@@ -0,0 +1,526 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+# bounce.py
+# Copyright (C) 2015 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/>.
+
+
+"""
+Everything you need to correctly bounce a message!
+
+This is built from the following RFCs:
+
+  * The Multipart/Report Media Type for the Reporting of Mail System
+    Administrative Messages
+    https://tools.ietf.org/html/rfc6522
+
+  * Recommendations for Automatic Responses to Electronic Mail
+    https://tools.ietf.org/html/rfc3834
+
+  * An Extensible Message Format for Delivery Status Notifications
+    https://tools.ietf.org/html/rfc3464
+"""
+
+
+import re
+import socket
+
+from StringIO import StringIO
+from textwrap import wrap
+
+from email.errors import MessageError
+from email.message import Message
+from email.utils import formatdate
+from email.utils import parseaddr
+from email.mime.base import MIMEBase
+from email.mime.multipart import MIMEMultipart
+from email.mime.text import MIMEText
+from email.generator import Generator
+from email.generator import NL
+
+from twisted.internet import defer
+from twisted.internet import protocol
+from twisted.internet import reactor
+from twisted.internet.error import ProcessDone
+from twisted.python import log
+
+
+EMAIL_ADDRESS_REGEXP = re.compile("[^@]+@[^@]+\.[^@]+")
+HOSTNAME = socket.gethostbyaddr(socket.gethostname())[0]
+
+
+def _valid_address(address):
+    """
+    Return whether address is a valid email address.
+
+    :param address: An email address candidate.
+    :type address: str
+
+    :return: Whether address is valid.
+    :rtype: bool
+    """
+    return bool(EMAIL_ADDRESS_REGEXP.match(address))
+
+
+def bounce_message(bounce_from, bounce_subject, orig_msg, reason):
+    """
+    Bounce a message.
+
+    :param bounce_from: The sender of the bounce message.
+    :type bounce_from: str
+    :param bounce_subject: The subject of the bounce message.
+    :type bounce_subject: str
+    :param orig_msg: The original message that will be bounced.
+    :type orig_msg: email.message.Message
+    :param reason: The reason for bouncing the message.
+    :type reason: str
+
+    :return: A deferred that will fire with the output of the sendmail process
+             if it was successful or with a failure containing the reason for
+             the end of the process if it failed.
+    :rtype: Deferred
+    """
+    orig_rpath = orig_msg.get("Return-Path")
+
+    # do not bounce if sender address is invalid
+    _, addr = parseaddr(orig_rpath)
+    if not _valid_address(addr):
+        log.msg(
+            "Will not send a bounce message to an invalid address: %s"
+            % orig_rpath)
+        return
+
+    msg = _build_bounce_message(
+        bounce_from, bounce_subject, orig_msg, reason)
+    return _async_check_output(["/usr/sbin/sendmail", "-t"], msg.as_string())
+
+
+def _check_valid_return_path(return_path):
+    """
+    Check if a certain return path is valid.
+
+    From RFC 3834:
+
+      Responders MUST NOT generate any response for which the
+      destination of that response would be a null address (e.g., an
+      address for which SMTP MAIL FROM or Return-Path is <>), since the
+      response would not be delivered to a useful destination.
+      Responders MAY refuse to generate responses for addresses commonly
+      used as return addresses by responders - e.g., those with local-
+      parts matching "owner-*", "*-request", "MAILER-DAEMON", etc.
+      Responders are encouraged to check the destination address for
+      validity before generating the response, to avoid generating
+      responses that cannot be delivered or are unlikely to be useful.
+
+    :return: Whether the return_path is valid.
+    :rtype: bool
+    """
+    _, addr = parseaddr(return_path)
+
+    # check null address
+    if not addr:
+        return False
+
+    # check addresses commonly used as return addresses by responders
+    local, _ = addr.split("@", 1)
+    if local.startswith("owner-") \
+            or local.endswith("-request") \
+            or local.startswith("MAILER-DAEMON"):
+        return False
+
+    return True
+
+
+class DeliveryStatusNotificationMessage(MIMEBase):
+    """
+    A delivery status message, as per RFC 3464.
+    """
+
+    def __init__(self, orig_msg):
+        """
+        Initialize the DSN.
+        """
+        MIMEBase.__init__(self, "message", "delivery-status")
+        self.__delitem__("MIME-Version")
+        self._build_dsn(orig_msg)
+
+    def _build_dsn(self, orig_msg):
+        """
+        Build an RFC 3464 compliant delivery status message.
+
+        :param orig_msg: The original bouncing message.
+        :type orig_msg: email.message.Message
+        """
+        content = []
+
+        # Per-Message DSN fields
+        # ======================
+
+        # Original-Envelope-Id (optional)
+        envelope_id = orig_msg.get("Envelope-Id")
+        if envelope_id:
+            content.append("Original-Envelope-Id: %s" % envelope_id)
+
+        # Reporting-MTA (required)
+        content.append("Reporting-MTA: dns; %s" % HOSTNAME)
+
+        # XXX add Arrival-Date DSN field? (optional).
+
+        content.append("")
+
+        # Per-Recipient DSN fields
+        # ========================
+
+        # Original-Recipient (optional)
+        orig_to = orig_msg.get("X-Original-To")  # added by postfix
+        _, orig_addr = parseaddr(orig_to)
+        if orig_addr:
+            content.append("Original-Recipient: rfc822; %s" % orig_addr)
+
+        # Final-Recipient (required)
+        delivered_to = orig_msg.get("Delivered-To")
+        content.append("Final-Recipient: rfc822; %s" % delivered_to)
+
+        # Action (required)
+        content.append("Action: failed")
+
+        # Status (required)
+        content.append("Status: 5.0.0")  # permanent failure
+
+        # XXX add other optional fields? (Remote-MTA, Diagnostic-Code,
+        #     Last-Attempt-Date, Final-Log-ID, Will-Retry-Until)
+
+        # return a "message/delivery-status" message
+        msg = Message()
+        msg.set_payload("\n".join(content))
+        self.attach(msg)
+
+
+class RFC822Headers(MIMEText):
+    """
+    A text/rfc822-headers mime message as defined in RFC 6522.
+    """
+
+    def __init__(self, _text, **kwargs):
+        """
+        Initialize the message.
+
+        :param _text: The contents of the message.
+        :type _text: str
+        """
+        MIMEText.__init__(
+            self, _text,
+            # set "text/rfc822-headers" mime type
+            _subtype='rfc822-headers',
+            **kwargs)
+
+
+BOUNCE_TEMPLATE = """
+This is the mail system at {0}.
+
+I'm sorry to have to inform you that your message could not
+be delivered to one or more recipients. It's attached below.
+
+For further assistance, please send mail to postmaster.
+
+If you do so, please include this problem report. You can
+delete your own text from the attached returned message.
+
+                   The mail system
+
+{1}
+""".strip()
+
+
+class InvalidReturnPathError(MessageError):
+    """
+    Exception raised when the return path is invalid.
+    """
+
+
+def _build_bounce_message(bounce_from, bounce_subject, orig_msg, reason):
+    """
+    Build a bounce message.
+
+    :param bounce_from: The sender address of the bounce message.
+    :type bounce_from: str
+    :param bounce_subject: The subject of the bounce message.
+    :type bounce_subject: str
+    :param orig_msg: The original bouncing message.
+    :type orig_msg: email.message.Message
+    :param reason: The reason for the bounce.
+    :type reason: str
+
+    :return: The bounce message.
+    :rtype: MIMEMultipartReport
+
+    :raise InvalidReturnPathError: Raised when the "Return-Path" header of the
+                                   original message is invalid for creating a
+                                   bounce message.
+    """
+    # abort creation if "Return-Path" header is invalid
+    orig_rpath = orig_msg.get("Return-Path")
+    if not _check_valid_return_path(orig_rpath):
+        raise InvalidReturnPathError
+
+    msg = MIMEMultipartReport()
+    msg['From'] = bounce_from
+    msg['To'] = orig_rpath
+    msg['Date'] = formatdate(localtime=True)
+    msg['Subject'] = bounce_subject
+    msg['Return-Path'] = "<>"  # prevent bounce message loop, see RFC 3834
+
+    # create and attach first required part
+    orig_to = orig_msg.get("X-Original-To")  # added by postfix
+    wrapped_reason = wrap(("<%s>: " % orig_to) + reason, 74)
+    for i in xrange(1, len(wrapped_reason)):
+        wrapped_reason[i] = "    " + wrapped_reason[i]
+    wrapped_reason = "\n".join(wrapped_reason)
+    text = BOUNCE_TEMPLATE.format(HOSTNAME, wrapped_reason)
+    msg.attach(MIMEText(text))
+
+    # create and attach second required part
+    msg.attach(DeliveryStatusNotificationMessage(orig_msg))
+
+    # attach third (optional) part.
+    #
+    # XXX From RFC 6522:
+    #
+    #       When 8-bit or binary data not encoded in a 7-bit form is to be
+    #       returned, and the return path is not guaranteed to be 8-bit or
+    #       binary capable, two options are available. The original message
+    #       MAY be re-encoded into a legal 7-bit MIME message or the
+    #       text/rfc822-headers media type MAY be used to return only the
+    #       original message headers.
+    #
+    #     This is not implemented yet, we should detect if content is 7bit and
+    #     use the class RFC822Headers if it is not.
+#     try:
+#        payload = orig_msg.get_payload()
+#        payload.encode("ascii")
+#    except UnicodeError:
+#        headers = []
+#        for k in orig_msg.keys():
+#            headers.append("%s: %s" % (k, orig_msg[k]))
+#        orig_msg = RFC822Headers("\n".join(headers))
+    msg.attach(orig_msg)
+
+    return msg
+
+
+class BouncerSubprocessProtocol(protocol.ProcessProtocol):
+    """
+    Bouncer subprocess protocol that will feed the msg contents to be
+    bounced through stdin
+    """
+
+    def __init__(self, msg):
+        """
+        Constructor for the BouncerSubprocessProtocol
+
+        :param msg: Message to send to stdin when the process has
+                    launched
+        :type msg: str
+        """
+        self._msg = msg
+        self._outBuffer = ""
+        self._errBuffer = ""
+        self._d = defer.Deferred()
+
+    @property
+    def deferred(self):
+        return self._d
+
+    def connectionMade(self):
+        self.transport.write(self._msg)
+        self.transport.closeStdin()
+
+    def outReceived(self, data):
+        self._outBuffer += data
+
+    def errReceived(self, data):
+        self._errBuffer += data
+
+    def processEnded(self, reason):
+        if reason.check(ProcessDone):
+            self._d.callback(self._outBuffer)
+        else:
+            self._d.errback(reason)
+
+
+def _async_check_output(args, msg):
+    """
+    Async spawn a process and return a defer to be able to check the
+    output with a callback/errback
+
+    :param args: the command to execute along with the params for it
+    :type args: list of str
+    :param msg: string that will be send to stdin of the process once
+                it's spawned
+    :type msg: str
+
+    :rtype: defer.Deferred
+    """
+    pprotocol = BouncerSubprocessProtocol(msg)
+    reactor.spawnProcess(pprotocol, args[0], args)
+    return pprotocol.deferred
+
+
+class DSNGenerator(Generator):
+    """
+    A slightly modified generator to correctly parse delivery status
+    notifications.
+    """
+
+    def _handle_message_delivery_status(self, msg):
+        """
+        Handle a message of type "message/delivery-status".
+
+        This is modified from upstream version in that it also removes empty
+        lines in the beginning of each part.
+
+        :param msg: The message to be handled.
+        :type msg: Message
+        """
+        # We can't just write the headers directly to self's file object
+        # because this will leave an extra newline between the last header
+        # block and the boundary.  Sigh.
+        blocks = []
+        for part in msg.get_payload():
+            s = StringIO()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False)
+            text = s.getvalue()
+            lines = text.split('\n')
+            # Strip off the unnecessary trailing empty line
+            if lines:
+                if lines[0] == '':
+                    lines.pop(0)
+                if lines[-1] == '':
+                    lines.pop()
+                blocks.append(NL.join(lines))
+            else:
+                blocks.append(text)
+        # Now join all the blocks with an empty line.  This has the lovely
+        # effect of separating each block with an empty line, but not adding
+        # an extra one after the last one.
+        self._fp.write(NL.join(blocks))
+
+
+class MIMEMultipartReport(MIMEMultipart):
+    """
+    Implement multipart/report MIME type as defined in RFC 6522.
+
+    The syntax of multipart/report is identical to the multipart/mixed
+    content type defined in https://tools.ietf.org/html/rfc2045.
+
+    The multipart/report media type contains either two or three sub-
+    parts, in the following order:
+
+      1. (REQUIRED) A human-readable message.
+      2. (REQUIRED) A machine-parsable body part containing an account of
+         the reported message handling event.
+      3. (OPTIONAL) A body part containing the returned message or a
+         portion thereof.
+    """
+
+    def __init__(
+            self, report_type="message/delivery-status", boundary=None,
+            _subparts=None):
+        """
+        Initialize the message.
+
+        As per RFC 6522, boundary and report_type are required parameters.
+
+        :param report_type: The type of report. This is set as a
+                            "Content-Type" parameter, and should match the
+                            MIME subtype of the second body part.
+        :type report_type: str
+
+        """
+        MIMEMultipart.__init__(
+            self,
+            # set mime type to "multipart/report"
+            _subtype="report",
+            boundary=boundary,
+            _subparts=_subparts,
+            # add "report-type" as a "Content-Type" parameter
+            report_type=report_type)
+        self._report_type = report_type
+
+    def attach(self, payload):
+        """
+        Add the given payload to the current payload, but first verify if it's
+        valid according to RFC6522.
+
+        :param payload: The payload to be attached.
+        :type payload: Message
+
+        :raise MessageError: Raised if the payload is invalid.
+        """
+        idx = len(self.get_payload()) + 1
+        self._check_valid_payload(idx, payload)
+        MIMEMultipart.attach(self, payload)
+
+    def _check_valid_payload(self, idx, payload):
+        """
+        Check that an attachment is valid according to RFC6522.
+
+        :param payload: The payload to be attached.
+        :type payload: Message
+
+        :raise MessageError: Raised if the payload is invalid.
+        """
+        if idx == 1:
+            # The text in the first section can use any IANA-registered MIME
+            # media type, charset, or language.
+            cond = lambda payload: isinstance(payload, MIMEBase)
+            error_msg = "The first attachment must be a MIME message."
+        elif idx == 2:
+            # RFC 6522 requires that the report-type parameter is equal to the
+            # MIME subtype of the second body type of the multipart/report.
+            cond = lambda payload: \
+                payload.get_content_type() == self._report_type
+            error_msg = "The second attachment's subtype must be %s." \
+                        % self._report_type
+        elif idx == 3:
+            # A body part containing the returned message or a portion thereof.
+            cond = lambda payload: isinstance(payload, Message)
+            error_msg = "The third attachment must be a message."
+        else:
+            # The multipart/report media type contains either two or three sub-
+            # parts.
+            cond = lambda _: False
+            error_msg = "The multipart/report media type contains either " \
+                        "two or three sub-parts."
+        if not cond(payload):
+            raise MessageError("Invalid attachment: %s" % error_msg)
+
+    def as_string(self, unixfrom=False):
+        """
+        Return the entire formatted message as string.
+
+        This is modified from upstream to use our own generator.
+
+        :param as_string: Whether to include the Unix From envelope heder.
+        :type as_string: bool
+
+        :return: The entire formatted message.
+        :rtype: str
+        """
+        fp = StringIO()
+        g = DSNGenerator(fp)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
diff --git a/src/leap/mx/check_recipient_access.py b/src/leap/mx/check_recipient_access.py
index b80ccfd..55460a6 100644
--- a/src/leap/mx/check_recipient_access.py
+++ b/src/leap/mx/check_recipient_access.py
@@ -17,26 +17,72 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 """
-Classes for resolving postfix recipient access
+Classes for resolving postfix recipient access.
+
+The resolver is queried by the mail server before delivery to the mail spool
+directory, and should check if the address is able to receive messages.
+Examples of reasons for denying delivery would be that the user is out of
+quota, is user, or have no pgp public key in the server.
 
 Test this with postmap -v -q "foo" tcp:localhost:2244
 """
 
 from twisted.protocols import postfix
 
-from leap.mx.alias_resolver import AliasResolverFactory
+from leap.mx.tcp_map import LEAPPostfixTCPMapServerFactory
+from leap.mx.tcp_map import TCP_MAP_CODE_SUCCESS
+from leap.mx.tcp_map import TCP_MAP_CODE_TEMPORARY_FAILURE
+from leap.mx.tcp_map import TCP_MAP_CODE_PERMANENT_FAILURE
+
+
+class LEAPPostFixTCPMapAccessServer(postfix.PostfixTCPMapServer):
+    """
+    A postfix tcp map recipient access checker server.
 
+    The server potentially receives the uuid and a PGP key for the user, which
+    are looked up by the factory, and will return a permanent or a temporary
+    failure in case either the user or the key don't exist, respectivelly.
+    """
 
-class LEAPPostFixTCPMapserverAccess(postfix.PostfixTCPMapServer):
     def _cbGot(self, value):
-        # For more info, see:
-        # http://www.postfix.org/tcp_table.5.html
-        # http://www.postfix.org/access.5.html
-        if value is None:
-            self.sendCode(500, postfix.quote("REJECT"))
+        """
+        Return a code and message depending on the result of the factory's
+        get().
+
+        If there's no pgp public key for the user, we currently return a
+        temporary failure saying that the user account is disabled.
+
+        For more info, see: http://www.postfix.org/access.5.html
+
+        :param value: The uuid and public key.
+        :type value: list
+        """
+        uuid, pubkey = value
+        if uuid is None:
+            self.sendCode(
+                TCP_MAP_CODE_PERMANENT_FAILURE,
+                postfix.quote("REJECT"))
+        elif pubkey is None:
+            self.sendCode(
+                TCP_MAP_CODE_TEMPORARY_FAILURE,
+                postfix.quote("4.7.13 USER ACCOUNT DISABLED"))
         else:
-            self.sendCode(200, postfix.quote("OK"))
+            self.sendCode(
+                TCP_MAP_CODE_SUCCESS,
+                postfix.quote("OK"))
+
+
+class CheckRecipientAccessFactory(LEAPPostfixTCPMapServerFactory):
+    """
+    A factory for the recipient access checker.
+
+    When queried, the factory looks up the user's uuid and a PGP key for that
+    user and returns the result to the server's _cbGot() method.
+    """
+
+    protocol = LEAPPostFixTCPMapAccessServer
 
+    @property
+    def _query_message(self):
+        return "Checking recipient access for"
 
-class CheckRecipientAccessFactory(AliasResolverFactory):
-    protocol = LEAPPostFixTCPMapserverAccess
diff --git a/src/leap/mx/couchdbhelper.py b/src/leap/mx/couchdbhelper.py
index f20f1dd..1752b4e 100644
--- a/src/leap/mx/couchdbhelper.py
+++ b/src/leap/mx/couchdbhelper.py
@@ -15,24 +15,15 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+
 """
 Classes for working with CouchDB or BigCouch instances which store email alias
 maps, user UUIDs, and GPG keyIDs.
 """
 
-from functools import partial
-
-try:
-    from paisley import client
-except ImportError:
-    print "This software requires paisley. Please see the README file"
-    print "for instructions on getting required dependencies."
 
-try:
-    from twisted.python import log
-except ImportError:
-    print "This software requires Twisted. Please see the README file"
-    print "for instructions on getting required dependencies."
+from paisley import client
+from twisted.python import log
 
 
 class ConnectedCouchDB(client.CouchDB):
@@ -66,24 +57,8 @@ class ConnectedCouchDB(client.CouchDB):
                                 username=username,
                                 password=password,
                                 *args, **kwargs)
-
         self._cache = {}
 
-        if dbName is None:
-            databases = self.listDB()
-            databases.addCallback(self._print_databases)
-
-    def _print_databases(self, data):
-        """
-        Callback for listDB that prints the available databases
-
-        :param data: response from the listDB command
-        :type data: array
-        """
-        log.msg("Available databases:")
-        for database in data:
-            log.msg("  * %s" % (database,))
-
     def createDB(self, dbName):
         """
         Overrides ``paisley.client.CouchDB.createDB``.
@@ -96,110 +71,63 @@ class ConnectedCouchDB(client.CouchDB):
         """
         pass
 
-    def queryByAddress(self, address):
+    def getUuidAndPubkey(self, address):
         """
-        Check to see if a particular email or alias exists.
+        Query couch and return a deferred that will fire with the uuid and pgp
+        public key for address.
 
-        :param alias: A string representing the email or alias to check.
-        :type alias: str
-        :return: a deferred for this query
+        :param address: A string representing the email or alias to check.
+        :type address: str
+        :return: A deferred that will fire with the user's uuid and pgp public
+                 key.
         :rtype twisted.defer.Deferred
         """
-        assert isinstance(address, (str, unicode)), "Email or alias queries must be string"
-
         # TODO: Cache results
-
         d = self.openView(docId="Identity",
                           viewId="by_address/",
                           key=address,
                           reduce=False,
                           include_docs=True)
 
-        d.addCallbacks(partial(self._get_uuid, address), log.err)
-
+        def _get_uuid_and_pubkey_cbk(result):
+            uuid = None
+            pubkey = None
+            if result["rows"]:
+                doc = result["rows"][0]["doc"]
+                uuid = doc["user_id"]
+                if "keys" in doc:
+                    pubkey = doc["keys"]["pgp"]
+            return uuid, pubkey
+
+        d.addCallback(_get_uuid_and_pubkey_cbk)
         return d
 
-    def _get_uuid(self, address, result):
-        """
-        Parses the result of the by_address query and gets the uuid
-
-        :param address: alias looked up
-        :type address: string
-        :param result: result dictionary
-        :type result: dict
-        :return: The uuid for alias if available
-        :rtype: str
-        """
-        for row in result["rows"]:
-            if row["key"] == address:
-                uuid = row["doc"].get("user_id", None)
-                if uuid is None:
-                    log.msg("ERROR: Found doc for %s but there's not user_id!"
-                            % (address,))
-                return uuid
-        return None
-
-    def getPubKey(self, uuid):
+    def getPubkey(self, uuid):
         """
-        Returns a deferred that will return the pubkey for the uuid provided
+        Query couch and return a deferred that will fire with the pgp public
+        key for user with given uuid.
 
-        :param uuid: uuid for the user to query
+        :param uuid: The uuid of a user
         :type uuid: str
 
+        :return: A deferred that will fire with the pgp public key for
+                 the user.
         :rtype: Deferred
         """
         d = self.openView(docId="Identity",
-                          viewId="pgp_key_by_email/",
-                          user_id=uuid,
+                          viewId="by_user_id/",
+                          key=uuid,
                           reduce=False,
                           include_docs=True)
 
-        d.addCallbacks(partial(self._get_pgp_key, uuid), log.err)
+        def _get_pubkey_cbk(result):
+            pubkey = None
+            try:
+                doc = result["rows"][0]["doc"]
+                pubkey = doc["keys"]["pgp"]
+            except (KeyError, IndexError):
+                pass
+            return pubkey
 
+        d.addCallbacks(_get_pubkey_cbk, log.err)
         return d
-
-    def _get_pgp_key(self, uuid, result):
-        """
-        Callback used to filter the correct pubkey from the result of
-        the query to the couchdb
-
-        :param uuid: uuid for the user that was queried
-        :type uuid: str
-        :param result: result dictionary for the db query
-        :type result: dict
-
-        :rtype: str or None
-        """
-        for row in result["rows"]:
-            user_id = row["doc"].get("user_id")
-            if not user_id:
-                print("User %s is in an inconsistent state")
-                continue
-            if user_id == uuid:
-                return row["value"]
-        return None
-
-if __name__ == "__main__":
-    from twisted.internet import reactor
-    cdb = ConnectedCouchDB("localhost",
-                           port=6666,
-                           dbName="users",
-                           username="",
-                           password="")
-
-    d = cdb.queryByLoginOrAlias("test1")
-
-    @d.addCallback
-    def right(result):
-        print "Should be an actual uuid:", result
-        print "Public Key:"
-        print cdb.getPubKey(result)
-
-    d2 = cdb.queryByLoginOrAlias("asdjaoisdjoiqwjeoi")
-
-    @d2.addCallback
-    def wrong(result):
-        print "Should be None:", result
-
-    reactor.callLater(5, reactor.stop)
-    reactor.run()
diff --git a/src/leap/mx/mail_receiver.py b/src/leap/mx/mail_receiver.py
index 630c982..446fd38 100644
--- a/src/leap/mx/mail_receiver.py
+++ b/src/leap/mx/mail_receiver.py
@@ -39,13 +39,8 @@ import signal
 
 import json
 import email.utils
-import socket
 
 from email import message_from_string
-from email.MIMEMultipart import MIMEMultipart
-from email.MIMEText import MIMEText
-from email.Utils import formatdate
-from email.header import decode_header
 
 from twisted.application.service import Service, IService
 from twisted.internet import inotify, defer, task, reactor
@@ -53,84 +48,15 @@ from twisted.python import filepath, log
 
 from zope.interface import implements
 
-from leap.soledad.common.crypto import (
-    EncryptionSchemes,
-    ENC_JSON_KEY,
-    ENC_SCHEME_KEY,
-)
+from leap.soledad.common.crypto import EncryptionSchemes
+from leap.soledad.common.crypto import ENC_JSON_KEY
+from leap.soledad.common.crypto import ENC_SCHEME_KEY
 from leap.soledad.common.couch import CouchDatabase, CouchDocument
-from leap.keymanager import openpgp
-
-BOUNCE_TEMPLATE = """
-Delivery to the following recipient failed:
-    {0}
-
-Reasons:
-    {1}
-
-Original message:
-    {2}
-""".strip()
-
-
-from twisted.internet import protocol
-from twisted.internet.error import ProcessDone
-
-
-class BouncerSubprocessProtocol(protocol.ProcessProtocol):
-    """
-    Bouncer subprocess protocol that will feed the msg contents to be
-    bounced through stdin
-    """
-
-    def __init__(self, msg):
-        """
-        Constructor for the BouncerSubprocessProtocol
-
-        :param msg: Message to send to stdin when the process has
-                    launched
-        :type msg: str
-        """
-        self._msg = msg
-        self._outBuffer = ""
-        self._errBuffer = ""
-        self._d = None
-
-    def connectionMade(self):
-        self._d = defer.Deferred()
-
-        self.transport.write(self._msg)
-        self.transport.closeStdin()
-
-    def outReceived(self, data):
-        self._outBuffer += data
 
-    def errReceived(self, data):
-        self._errBuffer += data
-
-    def processEnded(self, reason):
-        if reason.check(ProcessDone):
-            self._d.callback(self._outBuffer)
-        else:
-            self._d.errback(reason)
-
-
-def async_check_output(args, msg):
-    """
-    Async spawn a process and return a defer to be able to check the
-    output with a callback/errback
-
-    :param args: the command to execute along with the params for it
-    :type args: list of str
-    :param msg: string that will be send to stdin of the process once
-                it's spawned
-    :type msg: str
+from leap.keymanager import openpgp
 
-    :rtype: defer.Deferred
-    """
-    pprotocol = BouncerSubprocessProtocol(msg)
-    reactor.spawnProcess(pprotocol, args[0], args)
-    return pprotocol.d
+from leap.mx.bounce import bounce_message
+from leap.mx.bounce import InvalidReturnPathError
 
 
 class MailReceiver(Service):
@@ -177,8 +103,6 @@ class MailReceiver(Service):
         self._directories = directories
         self._bounce_from = bounce_from
         self._bounce_subject = bounce_subject
-
-        self._domain = socket.gethostbyaddr(socket.gethostname())[0]
         self._processing_skipped = False
 
     def startService(self):
@@ -353,7 +277,7 @@ class MailReceiver(Service):
 
     def _get_owner(self, mail):
         """
-        Given an email, returns the uuid of the owner.
+        Given an email, return the uuid of the owner.
 
         :param mail: mail to analyze
         :type mail: email.message.Message
@@ -361,25 +285,24 @@ class MailReceiver(Service):
         :returns: uuid
         :rtype: str or None
         """
-        uuid = None
-
+        # we expect the topmost "Delivered-To" header to indicate the correct
+        # final delivery address. It should consist of <uuid>@<domain>, as the
+        # earlier alias resolver query should have translated the username to
+        # the user id. See https://leap.se/code/issues/6858 for more info.
         delivereds = mail.get_all("Delivered-To")
         if delivereds is None:
+            # XXX this should not happen! see the comment above
             return None
-        for to in delivereds:
-            name, addr = email.utils.parseaddr(to)
-            parts = addr.split("@")
-            if len(parts) > 1 and parts[1] == self._domain:
-                uuid = parts[0]
-                break
-
+        final_address = delivereds.pop(0)
+        _, addr = email.utils.parseaddr(final_address)
+        uuid, _ = addr.split("@")
         return uuid
 
     @defer.inlineCallbacks
-    def _bounce_mail(self, orig_msg, filepath, reason):
+    def _bounce_message(self, orig_msg, filepath, reason):
         """
-        Bounces the email contained in orig_msg to it's sender and
-        removes it from the queue.
+        Bounce the message contained in orig_msg to it's sender and
+        remove it from the queue.
 
         :param orig_msg: Message that is going to be bounced
         :type orig_msg: email.message.Message
@@ -388,22 +311,12 @@ class MailReceiver(Service):
         :param reason: Brief explanation about why it's being bounced
         :type reason: str
         """
-        to = orig_msg.get("From")
-
-        msg = MIMEMultipart()
-        msg['From'] = self._bounce_from
-        msg['To'] = to
-        msg['Date'] = formatdate(localtime=True)
-        msg['Subject'] = self._bounce_subject
-
-        decoded_to = " ".join([x[0] for x in decode_header(to)])
-        text = BOUNCE_TEMPLATE.format(decoded_to,
-                                      reason,
-                                      orig_msg.as_string())
-
-        msg.attach(MIMEText(text))
-
-        yield async_check_output(["/usr/sbin/sendmail", "-t"], msg.as_string())
+        try:
+            yield bounce_message(
+                self._bounce_from, self._bounce_subject, orig_msg, reason)
+        except InvalidReturnPathError:
+            # give up bouncing this message!
+            log.msg("Will not bounce message because of invalid return path.")
         yield self._conditional_remove(True, filepath)
 
     def sleep(self, secs):
@@ -478,7 +391,7 @@ class MailReceiver(Service):
                         (filepath.path,))
                 bounce_reason = "Missing UUID: There was a problem " \
                                 "locating the user in our database."
-                yield self._bounce_mail(msg, filepath, bounce_reason)
+                yield self._bounce_message(msg, filepath, bounce_reason)
                 defer.returnValue(None)
             log.msg("Mail owner: %s" % (uuid,))
 
@@ -486,13 +399,15 @@ class MailReceiver(Service):
                 log.msg("BUG: There was no uuid!")
                 defer.returnValue(None)
 
-            pubkey = yield self._users_cdb.getPubKey(uuid)
+            pubkey = yield self._users_cdb.getPubkey(uuid)
             if pubkey is None or len(pubkey) == 0:
-                log.msg("No public key, stopping the processing chain")
-                bounce_reason = "Missing PubKey: There was a problem " \
-                                "locating the user's public key in our " \
-                                "database."
-                yield self._bounce_mail(msg, filepath, bounce_reason)
+                log.msg(
+                    "No public key for %s, stopping the processing chain."
+                    % uuid)
+                bounce_reason = "Missing PGP public key: There was a " \
+                                "problem locating the user's public key in " \
+                                "our database."
+                yield self._bounce_message(msg, filepath, bounce_reason)
                 defer.returnValue(None)
 
             log.msg("Encrypting message to %s's pubkey" % (uuid,))
diff --git a/src/leap/mx/tcp_map.py b/src/leap/mx/tcp_map.py
new file mode 100644
index 0000000..597c830
--- /dev/null
+++ b/src/leap/mx/tcp_map.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+# tcpmap.py
+# Copyright (C) 2015 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/>.
+
+
+from abc import ABCMeta
+from abc import abstractproperty
+
+from twisted.internet.protocol import ServerFactory
+from twisted.python import log
+
+
+# For info on codes, see: http://www.postfix.org/tcp_table.5.html
+TCP_MAP_CODE_SUCCESS = 200
+TCP_MAP_CODE_TEMPORARY_FAILURE = 400
+TCP_MAP_CODE_PERMANENT_FAILURE = 500
+
+
+# we have to also extend from object here to make the class a new-style class.
+# If we don't, we get a TypeError because "new-style classes can't have only
+# classic bases". This has to do with the way abc.ABCMeta works and the old
+# and new style of python classes.
+class LEAPPostfixTCPMapServerFactory(ServerFactory, object):
+    """
+    A factory for postfix tcp map servers.
+    """
+
+    __metaclass__ = ABCMeta
+
+
+    def __init__(self, couchdb):
+        """
+        Initialize the factory.
+
+        :param couchdb: A CouchDB client.
+        :type couchdb: leap.mx.couchdbhelper.ConnectedCouchDB
+        """
+        self._cdb = couchdb
+
+    @abstractproperty
+    def _query_message(self):
+        pass
+
+    def get(self, lookup_key):
+        """
+        Look up user based on lookup_key.
+
+        :param lookup_key: The lookup key.
+        :type lookup_key: str
+
+        :return: A deferred that will be fired with the user's address, uuid
+                 and pgp key.
+        :rtype: Deferred
+        """
+        log.msg("%s %s" % (self._query_message, lookup_key,))
+        d = self._cdb.getUuidAndPubkey(lookup_key)
+        d.addErrback(log.err)
+        return d