make outgoing a new submodule

1 files changed, 429 insertions, 0 deletions

diff --git a/src/leap/mail/outgoing/service.py b/src/leap/mail/outgoing/service.py
new file mode 100644
index 0000000..b70b3b1
--- /dev/null
+++ b/src/leap/mail/outgoing/service.py
@@ -0,0 +1,429 @@
+# -*- coding: utf-8 -*-
+# outgoing/service.py
+# Copyright (C) 2013-2015 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/>.
+import re
+from StringIO import StringIO
+from email.parser import Parser
+from email.mime.application import MIMEApplication
+
+from OpenSSL import SSL
+
+from twisted.mail import smtp
+from twisted.internet import reactor
+from twisted.internet import defer
+from twisted.protocols.amp import ssl
+from twisted.python import log
+
+from leap.common.check import leap_assert_type, leap_assert
+from leap.common.events import proto, signal
+from leap.keymanager import KeyManager
+from leap.keymanager.openpgp import OpenPGPKey
+from leap.keymanager.errors import KeyNotFound
+from leap.mail import __version__
+from leap.mail.utils import validate_address
+from leap.mail.smtp.rfc3156 import MultipartEncrypted
+from leap.mail.smtp.rfc3156 import MultipartSigned
+from leap.mail.smtp.rfc3156 import encode_base64_rec
+from leap.mail.smtp.rfc3156 import RFC3156CompliantGenerator
+from leap.mail.smtp.rfc3156 import PGPSignature
+from leap.mail.smtp.rfc3156 import PGPEncrypted
+
+# TODO
+# [ ] rename this module to something else, service should be the implementor
+#     of IService
+
+
+class SSLContextFactory(ssl.ClientContextFactory):
+    def __init__(self, cert, key):
+        self.cert = cert
+        self.key = key
+
+    def getContext(self):
+        # FIXME -- we should use sslv23 to allow for tlsv1.2
+        # and, if possible, explicitely disable sslv3 clientside.
+        # Servers should avoid sslv3
+        self.method = SSL.TLSv1_METHOD  # SSLv23_METHOD
+        ctx = ssl.ClientContextFactory.getContext(self)
+        ctx.use_certificate_file(self.cert)
+        ctx.use_privatekey_file(self.key)
+        return ctx
+
+
+class OutgoingMail:
+    """
+    A service for handling encrypted outgoing mail.
+    """
+
+    FOOTER_STRING = "I prefer encrypted email"
+
+    def __init__(self, from_address, keymanager, cert, key, host, port):
+        """
+        Initialize the mail service.
+
+        :param from_address: The sender address.
+        :type from_address: str
+        :param keymanager: A KeyManager for retrieving recipient's keys.
+        :type keymanager: leap.common.keymanager.KeyManager
+        :param cert: The client certificate for SSL authentication.
+        :type cert: str
+        :param key: The client private key for SSL authentication.
+        :type key: str
+        :param host: The hostname of the remote SMTP server.
+        :type host: str
+        :param port: The port of the remote SMTP server.
+        :type port: int
+        """
+
+        # assert params
+        leap_assert_type(from_address, str)
+        leap_assert('@' in from_address)
+        leap_assert_type(keymanager, KeyManager)
+        leap_assert_type(host, str)
+        leap_assert(host != '')
+        leap_assert_type(port, int)
+        leap_assert(port is not 0)
+        leap_assert_type(cert, unicode)
+        leap_assert(cert != '')
+        leap_assert_type(key, unicode)
+        leap_assert(key != '')
+
+        self._port = port
+        self._host = host
+        self._key = key
+        self._cert = cert
+        self._from_address = from_address
+        self._keymanager = keymanager
+
+    def send_message(self, raw, recipient):
+        """
+        Sends a message to a recipient. Maybe encrypts and signs.
+
+        :param raw: The raw message
+        :type raw: str
+        :param recipient: The recipient for the message
+        :type recipient: smtp.User
+        :return: a deferred which delivers the message when fired
+        """
+        d = self._maybe_encrypt_and_sign(raw, recipient)
+        d.addCallback(self._route_msg)
+        d.addErrback(self.sendError)
+        return d
+
+    def sendSuccess(self, smtp_sender_result):
+        """
+        Callback for a successful send.
+
+        :param smtp_sender_result: The result from the ESMTPSender from
+                                   _route_msg
+        :type smtp_sender_result: tuple(int, list(tuple))
+        """
+        dest_addrstr = smtp_sender_result[1][0][0]
+        log.msg('Message sent to %s' % dest_addrstr)
+        signal(proto.SMTP_SEND_MESSAGE_SUCCESS, dest_addrstr)
+
+    def sendError(self, failure):
+        """
+        Callback for an unsuccessfull send.
+
+        :param e: The result from the last errback.
+        :type e: anything
+        """
+        # XXX: need to get the address from the exception to send signal
+        # signal(proto.SMTP_SEND_MESSAGE_ERROR, self._user.dest.addrstr)
+        err = failure.value
+        log.err(err)
+        raise err
+
+    def _route_msg(self, encrypt_and_sign_result):
+        """
+        Sends the msg using the ESMTPSenderFactory.
+
+        :param encrypt_and_sign_result: A tuple containing the 'maybe'
+                                        encrypted message and the recipient
+        :type encrypt_and_sign_result: tuple
+        """
+        message, recipient = encrypt_and_sign_result
+        log.msg("Connecting to SMTP server %s:%s" % (self._host, self._port))
+        msg = message.as_string(False)
+
+        # we construct a defer to pass to the ESMTPSenderFactory
+        d = defer.Deferred()
+        d.addCallbacks(self.sendSuccess, self.sendError)
+        # we don't pass an ssl context factory to the ESMTPSenderFactory
+        # because ssl will be handled by reactor.connectSSL() below.
+        factory = smtp.ESMTPSenderFactory(
+            "",  # username is blank because client auth is done on SSL protocol level
+            "",  # password is blank because client auth is done on SSL protocol level
+            self._from_address,
+            recipient.dest.addrstr,
+            StringIO(msg),
+            d,
+            heloFallback=True,
+            requireAuthentication=False,
+            requireTransportSecurity=True)
+        factory.domain = __version__
+        signal(proto.SMTP_SEND_MESSAGE_START, recipient.dest.addrstr)
+        reactor.connectSSL(
+            self._host, self._port, factory,
+            contextFactory=SSLContextFactory(self._cert, self._key))
+
+    def _maybe_encrypt_and_sign(self, raw, recipient):
+        """
+        Attempt to encrypt and sign the outgoing message.
+
+        The behaviour of this method depends on:
+
+            1. the original message's content-type, and
+            2. the availability of the recipient's public key.
+
+        If the original message's content-type is "multipart/encrypted", then
+        the original message is not altered. For any other content-type, the
+        method attempts to fetch the recipient's public key. If the
+        recipient's public key is available, the message is encrypted and
+        signed; otherwise it is only signed.
+
+        Note that, if the C{encrypted_only} configuration is set to True and
+        the recipient's public key is not available, then the recipient
+        address would have been rejected in SMTPDelivery.validateTo().
+
+        The following table summarizes the overall behaviour of the gateway:
+
+        +---------------------------------------------------+----------------+
+        | content-type        | rcpt pubkey | enforce encr. | action         |
+        +---------------------+-------------+---------------+----------------+
+        | multipart/encrypted | any         | any           | pass           |
+        | other               | available   | any           | encrypt + sign |
+        | other               | unavailable | yes           | reject         |
+        | other               | unavailable | no            | sign           |
+        +---------------------+-------------+---------------+----------------+
+
+        :param raw: The raw message
+        :type raw: str
+        :param recipient: The recipient for the message
+        :type: recipient: smtp.User
+
+        :return: A Deferred that will be fired with a MIMEMultipart message
+                 and the original recipient Message
+        :rtype: Deferred
+        """
+        # pass if the original message's content-type is "multipart/encrypted"
+        lines = raw.split('\r\n')
+        origmsg = Parser().parsestr(raw)
+
+        if origmsg.get_content_type() == 'multipart/encrypted':
+            return defer.success((origmsg, recipient))
+
+        from_address = validate_address(self._from_address)
+        username, domain = from_address.split('@')
+        to_address = validate_address(recipient.dest.addrstr)
+
+        # add a nice footer to the outgoing message
+        # XXX: footer will eventually optional or be removed
+        if origmsg.get_content_type() == 'text/plain':
+            lines.append('--')
+            lines.append('%s - https://%s/key/%s' %
+                         (self.FOOTER_STRING, domain, username))
+            lines.append('')
+
+        origmsg = Parser().parsestr('\r\n'.join(lines))
+
+        def signal_encrypt_sign(newmsg):
+            signal(proto.SMTP_END_ENCRYPT_AND_SIGN,
+                   "%s,%s" % (self._from_address, to_address))
+            return newmsg, recipient
+
+        def signal_sign(newmsg):
+            signal(proto.SMTP_END_SIGN, self._from_address)
+            return newmsg, recipient
+
+        def if_key_not_found_send_unencrypted(failure):
+            if failure.check(KeyNotFound):
+                log.msg('Will send unencrypted message to %s.' % to_address)
+                signal(proto.SMTP_START_SIGN, self._from_address)
+                d = self._sign(origmsg, from_address)
+                d.addCallback(signal_sign)
+                return d
+            else:
+                return failure
+
+        log.msg("Will encrypt the message with %s and sign with %s."
+                % (to_address, from_address))
+        signal(proto.SMTP_START_ENCRYPT_AND_SIGN,
+               "%s,%s" % (self._from_address, to_address))
+        d = self._encrypt_and_sign(origmsg, to_address, from_address)
+        d.addCallbacks(signal_encrypt_sign, if_key_not_found_send_unencrypted)
+        return d
+
+    def _encrypt_and_sign(self, origmsg, encrypt_address, sign_address):
+        """
+        Create an RFC 3156 compliang PGP encrypted and signed message using
+        C{encrypt_address} to encrypt and C{sign_address} to sign.
+
+        :param origmsg: The original message
+        :type origmsg: email.message.Message
+        :param encrypt_address: The address used to encrypt the message.
+        :type encrypt_address: str
+        :param sign_address: The address used to sign the message.
+        :type sign_address: str
+
+        :return: A Deferred with the MultipartEncrypted message
+        :rtype: Deferred
+        """
+        # create new multipart/encrypted message with 'pgp-encrypted' protocol
+
+        def encrypt(res):
+            newmsg, origmsg = res
+            d = self._keymanager.encrypt(
+                origmsg.as_string(unixfrom=False),
+                encrypt_address, OpenPGPKey, sign=sign_address)
+            d.addCallback(lambda encstr: (newmsg, encstr))
+            return d
+
+        def create_encrypted_message(res):
+            newmsg, encstr = res
+            encmsg = MIMEApplication(
+                encstr, _subtype='octet-stream', _encoder=lambda x: x)
+            encmsg.add_header('content-disposition', 'attachment',
+                              filename='msg.asc')
+            # create meta message
+            metamsg = PGPEncrypted()
+            metamsg.add_header('Content-Disposition', 'attachment')
+            # attach pgp message parts to new message
+            newmsg.attach(metamsg)
+            newmsg.attach(encmsg)
+            return newmsg
+
+        d = self._fix_headers(
+            origmsg,
+            MultipartEncrypted('application/pgp-encrypted'),
+            sign_address)
+        d.addCallback(encrypt)
+        d.addCallback(create_encrypted_message)
+        return d
+
+    def _sign(self, origmsg, sign_address):
+        """
+        Create an RFC 3156 compliant PGP signed MIME message using
+        C{sign_address}.
+
+        :param origmsg: The original message
+        :type origmsg: email.message.Message
+        :param sign_address: The address used to sign the message.
+        :type sign_address: str
+
+        :return: A Deferred with the MultipartSigned message.
+        :rtype: Deferred
+        """
+        # apply base64 content-transfer-encoding
+        encode_base64_rec(origmsg)
+        # get message text with headers and replace \n for \r\n
+        fp = StringIO()
+        g = RFC3156CompliantGenerator(
+            fp, mangle_from_=False, maxheaderlen=76)
+        g.flatten(origmsg)
+        msgtext = re.sub('\r?\n', '\r\n', fp.getvalue())
+        # make sure signed message ends with \r\n as per OpenPGP stantard.
+        if origmsg.is_multipart():
+            if not msgtext.endswith("\r\n"):
+                msgtext += "\r\n"
+
+        def create_signed_message(res):
+            (msg, _), signature = res
+            sigmsg = PGPSignature(signature)
+            # attach original message and signature to new message
+            msg.attach(origmsg)
+            msg.attach(sigmsg)
+            return msg
+
+        dh = self._fix_headers(
+            origmsg,
+            MultipartSigned('application/pgp-signature', 'pgp-sha512'),
+            sign_address)
+        ds = self._keymanager.sign(
+            msgtext, sign_address, OpenPGPKey, digest_algo='SHA512',
+            clearsign=False, detach=True, binary=False)
+        d = defer.gatherResults([dh, ds])
+        d.addCallback(create_signed_message)
+        return d
+
+    def _fix_headers(self, origmsg, newmsg, sign_address):
+        """
+        Move some headers from C{origmsg} to C{newmsg}, delete unwanted
+        headers from C{origmsg} and add new headers to C{newms}.
+
+        Outgoing messages are either encrypted and signed or just signed
+        before being sent. Because of that, they are packed inside new
+        messages and some manipulation has to be made on their headers.
+
+        Allowed headers for passing through:
+
+            - From
+            - Date
+            - To
+            - Subject
+            - Reply-To
+            - References
+            - In-Reply-To
+            - Cc
+
+        Headers to be added:
+
+            - Message-ID (i.e. should not use origmsg's Message-Id)
+            - Received (this is added automatically by twisted smtp API)
+            - OpenPGP (see #4447)
+
+        Headers to be deleted:
+
+            - User-Agent
+
+        :param origmsg: The original message.
+        :type origmsg: email.message.Message
+        :param newmsg: The new message being created.
+        :type newmsg: email.message.Message
+        :param sign_address: The address used to sign C{newmsg}
+        :type sign_address: str
+
+        :return: A Deferred with a touple:
+                 (new Message with the unencrypted headers,
+                  original Message with headers removed)
+        :rtype: Deferred
+        """
+        # move headers from origmsg to newmsg
+        headers = origmsg.items()
+        passthrough = [
+            'from', 'date', 'to', 'subject', 'reply-to', 'references',
+            'in-reply-to', 'cc'
+        ]
+        headers = filter(lambda x: x[0].lower() in passthrough, headers)
+        for hkey, hval in headers:
+            newmsg.add_header(hkey, hval)
+            del (origmsg[hkey])
+        # add a new message-id to newmsg
+        newmsg.add_header('Message-Id', smtp.messageid())
+        # delete user-agent from origmsg
+        del (origmsg['user-agent'])
+
+        def add_openpgp_header(signkey):
+            username, domain = sign_address.split('@')
+            newmsg.add_header(
+                'OpenPGP', 'id=%s' % signkey.key_id,
+                url='https://%s/key/%s' % (domain, username),
+                preference='signencrypt')
+            return newmsg, origmsg
+
+        d = self._keymanager.get_key(sign_address, OpenPGPKey, private=True)
+        d.addCallback(add_openpgp_header)
+        return d