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Diffstat (limited to 'src/leap/mail/service.py')
| -rw-r--r-- | src/leap/mail/service.py | 384 |
1 files changed, 384 insertions, 0 deletions
diff --git a/src/leap/mail/service.py b/src/leap/mail/service.py new file mode 100644 index 0000000..d595067 --- /dev/null +++ b/src/leap/mail/service.py @@ -0,0 +1,384 @@ +# -*- coding: utf-8 -*- +# service.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/>. +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.internet.threads import deferToThread +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 + + +class SSLContextFactory(ssl.ClientContextFactory): + def __init__(self, cert, key): + self.cert = cert + self.key = key + + def getContext(self): + 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 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 + """ + + # XXX: should we keep these checks? + # assert params + 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 = deferToThread(lambda: 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 + + """ + # 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 origmsg + + from_address = validate_address(self._from_address) + username, domain = from_address.split('@') + + # 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)) + + # get sender and recipient data + signkey = self._keymanager.get_key(from_address, OpenPGPKey, private=True) + log.msg("Will sign the message with %s." % signkey.fingerprint) + to_address = validate_address(recipient.dest.addrstr) + try: + # try to get the recipient pubkey + pubkey = self._keymanager.get_key(to_address, OpenPGPKey) + log.msg("Will encrypt the message to %s." % pubkey.fingerprint) + signal(proto.SMTP_START_ENCRYPT_AND_SIGN, + "%s,%s" % (self._from_address, to_address)) + newmsg = self._encrypt_and_sign(origmsg, pubkey, signkey) + + signal(proto.SMTP_END_ENCRYPT_AND_SIGN, + "%s,%s" % (self._from_address, to_address)) + except KeyNotFound: + # at this point we _can_ send unencrypted mail, because if the + # configuration said the opposite the address would have been + # rejected in SMTPDelivery.validateTo(). + log.msg('Will send unencrypted message to %s.' % to_address) + signal(proto.SMTP_START_SIGN, self._from_address) + newmsg = self._sign(origmsg, signkey) + signal(proto.SMTP_END_SIGN, self._from_address) + return newmsg, recipient + + + def _encrypt_and_sign(self, origmsg, pubkey, signkey): + """ + Create an RFC 3156 compliang PGP encrypted and signed message using + C{pubkey} to encrypt and C{signkey} to sign. + + :param origmsg: The original message + :type origmsg: email.message.Message + :param pubkey: The public key used to encrypt the message. + :type pubkey: OpenPGPKey + :param signkey: The private key used to sign the message. + :type signkey: OpenPGPKey + :return: The encrypted and signed message + :rtype: MultipartEncrypted + """ + # create new multipart/encrypted message with 'pgp-encrypted' protocol + newmsg = MultipartEncrypted('application/pgp-encrypted') + # move (almost) all headers from original message to the new message + self._fix_headers(origmsg, newmsg, signkey) + # create 'application/octet-stream' encrypted message + encmsg = MIMEApplication( + self._keymanager.encrypt(origmsg.as_string(unixfrom=False), pubkey, + sign=signkey), + _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 + + + def _sign(self, origmsg, signkey): + """ + Create an RFC 3156 compliant PGP signed MIME message using C{signkey}. + + :param origmsg: The original message + :type origmsg: email.message.Message + :param signkey: The private key used to sign the message. + :type signkey: leap.common.keymanager.openpgp.OpenPGPKey + :return: The signed message. + :rtype: MultipartSigned + """ + # create new multipart/signed message + newmsg = MultipartSigned('application/pgp-signature', 'pgp-sha512') + # move (almost) all headers from original message to the new message + self._fix_headers(origmsg, newmsg, signkey) + # 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" + # calculate signature + signature = self._keymanager.sign(msgtext, signkey, digest_algo='SHA512', + clearsign=False, detach=True, binary=False) + sigmsg = PGPSignature(signature) + # attach original message and signature to new message + newmsg.attach(origmsg) + newmsg.attach(sigmsg) + return newmsg + + + def _fix_headers(self, origmsg, newmsg, signkey): + """ + 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 signkey: The key used to sign C{newmsg} + :type signkey: OpenPGPKey + """ + # 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()) + # add openpgp header to newmsg + username, domain = signkey.address.split('@') + newmsg.add_header( + 'OpenPGP', 'id=%s' % signkey.key_id, + url='https://%s/key/%s' % (domain, username), + preference='signencrypt') + # delete user-agent from origmsg + del (origmsg['user-agent']) |