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Diffstat (limited to 'src/leap/bitmask/mail/incoming/service.py')
| -rw-r--r-- | src/leap/bitmask/mail/incoming/service.py | 844 |
1 files changed, 844 insertions, 0 deletions
diff --git a/src/leap/bitmask/mail/incoming/service.py b/src/leap/bitmask/mail/incoming/service.py new file mode 100644 index 0000000..1e20862 --- /dev/null +++ b/src/leap/bitmask/mail/incoming/service.py @@ -0,0 +1,844 @@ +# -*- coding: utf-8 -*- +# service.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/>. +""" +Incoming mail fetcher. +""" +import copy +import logging +import shlex +import time +import warnings + +from email.parser import Parser +from email.utils import parseaddr +from email.utils import formatdate +from StringIO import StringIO +from urlparse import urlparse + +from twisted.application.service import Service +from twisted.python import log +from twisted.python.failure import Failure +from twisted.internet import defer, reactor +from twisted.internet.task import LoopingCall +from twisted.internet.task import deferLater + +from leap.common.events import emit_async, catalog +from leap.common.check import leap_assert, leap_assert_type +from leap.common.mail import get_email_charset +from leap.keymanager import errors as keymanager_errors +from leap.mail.adaptors import soledad_indexes as fields +from leap.mail.generator import Generator +from leap.mail.utils import json_loads, empty +from leap.soledad.client import Soledad +from leap.soledad.common.crypto import ENC_SCHEME_KEY, ENC_JSON_KEY +from leap.soledad.common.errors import InvalidAuthTokenError + + +logger = logging.getLogger(__name__) + +MULTIPART_ENCRYPTED = "multipart/encrypted" +MULTIPART_SIGNED = "multipart/signed" +PGP_BEGIN = "-----BEGIN PGP MESSAGE-----" +PGP_END = "-----END PGP MESSAGE-----" + +# The period between succesive checks of the incoming mail +# queue (in seconds) +INCOMING_CHECK_PERIOD = 60 + + +class MalformedMessage(Exception): + """ + Raised when a given message is not well formed. + """ + pass + + +class IncomingMail(Service): + """ + Fetches and process mail from the incoming pool. + + This object implements IService interface, has public methods + startService and stopService 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. + """ + # TODO implements IService? + + name = "IncomingMail" + + RECENT_FLAG = "\\Recent" + CONTENT_KEY = "content" + + LEAP_SIGNATURE_HEADER = 'X-Leap-Signature' + LEAP_ENCRYPTION_HEADER = 'X-Leap-Encryption' + """ + Header added to messages when they are decrypted by the 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' + + LEAP_ENCRYPTION_DECRYPTED = 'decrypted' + + def __init__(self, keymanager, soledad, inbox, userid, + check_period=INCOMING_CHECK_PERIOD): + + """ + Initialize IncomingMail.. + + :param keymanager: a keymanager instance + :type keymanager: keymanager.KeyManager + + :param soledad: a soledad instance + :type soledad: Soledad + + :param inbox: the collection for the inbox where the new emails will be + stored + :type inbox: MessageCollection + + :param check_period: the period to fetch new mail, in seconds. + :type check_period: int + """ + leap_assert(keymanager, "need a keymanager to initialize") + leap_assert_type(soledad, Soledad) + leap_assert(check_period, "need a period to check incoming mail") + leap_assert_type(check_period, int) + leap_assert(userid, "need a userid to initialize") + + self._keymanager = keymanager + self._soledad = soledad + self._inbox_collection = inbox + self._userid = userid + + self._listeners = [] + self._loop = None + self._check_period = check_period + + # initialize a mail parser only once + self._parser = Parser() + + def add_listener(self, listener): + """ + Add a listener to inbox insertions. + + This listener function will be called for each message added to the + inbox with its uid as parameter. This function should not be blocking + or it will block the incoming queue. + + :param listener: the listener function + :type listener: callable + """ + self._listeners.append(listener) + + # + # Public API: fetch, start_loop, stop. + # + + def fetch(self): + """ + Fetch incoming mail, to be called periodically. + + Calls a deferred that will execute the fetch callback. + """ + def _sync_errback(failure): + log.err(failure) + + def syncSoledadCallback(_): + # XXX this should be moved to adaptors + d = self._soledad.get_from_index( + fields.JUST_MAIL_IDX, "1", "0") + d.addCallback(self._process_doclist) + d.addErrback(_sync_errback) + return d + + logger.debug("fetching mail for: %s %s" % ( + self._soledad.uuid, self._userid)) + d = self._sync_soledad() + d.addCallbacks(syncSoledadCallback, self._errback) + d.addCallbacks(self._signal_fetch_to_ui, self._errback) + return d + + def startService(self): + """ + Starts a loop to fetch mail. + + :returns: A Deferred whose callback will be invoked with + the LoopingCall instance when loop.stop is called, or + whose errback will be invoked when the function raises an + exception or returned a deferred that has its errback + invoked. + """ + Service.startService(self) + if self._loop is None: + self._loop = LoopingCall(self.fetch) + stop_deferred = self._loop.start(self._check_period) + return stop_deferred + else: + logger.warning("Tried to start an already running fetching loop.") + return defer.fail(Failure('Already running loop.')) + + def stopService(self): + """ + Stops the loop that fetches mail. + """ + if self._loop and self._loop.running is True: + self._loop.stop() + self._loop = None + Service.stopService(self) + + # + # Private methods. + # + + # synchronize incoming mail + + def _errback(self, failure): + log.err(failure) + + def _sync_soledad(self): + """ + Synchronize with remote soledad. + + :returns: a list of LeapDocuments, or None. + :rtype: iterable or None + """ + def _log_synced(result): + log.msg('FETCH soledad SYNCED.') + return result + + def _signal_invalid_auth(failure): + failure.trap(InvalidAuthTokenError) + # if the token is invalid, send an event so the GUI can + # disable mail and show an error message. + emit_async(catalog.SOLEDAD_INVALID_AUTH_TOKEN, self._userid) + + log.msg('FETCH: syncing soledad...') + d = self._soledad.sync() + d.addCallbacks(_log_synced, _signal_invalid_auth) + return d + + def _signal_fetch_to_ui(self, doclist): + """ + Send leap events to ui. + + :param doclist: iterable with msg documents. + :type doclist: iterable. + :returns: doclist + :rtype: iterable + """ + if doclist: + fetched_ts = time.mktime(time.gmtime()) + num_mails = len(doclist) if doclist is not None else 0 + if num_mails != 0: + log.msg("there are %s mails" % (num_mails,)) + emit_async(catalog.MAIL_FETCHED_INCOMING, self._userid, + str(num_mails), str(fetched_ts)) + return doclist + + def _signal_unread_to_ui(self, *args): + """ + Sends unread event to ui. + """ + emit_async(catalog.MAIL_UNREAD_MESSAGES, self._userid, + str(self._inbox_collection.count_unseen())) + + # process incoming mail. + + def _process_doclist(self, doclist): + """ + Iterates through the doclist, checks if each doc + looks like a message, and yields a deferred that will decrypt and + process the message. + + :param doclist: iterable with msg documents. + :type doclist: iterable. + :returns: a list of deferreds for individual messages. + """ + log.msg('processing doclist') + if not doclist: + logger.debug("no docs found") + return + num_mails = len(doclist) + + deferreds = [] + for index, doc in enumerate(doclist): + logger.debug("processing doc %d of %d" % (index + 1, num_mails)) + emit_async(catalog.MAIL_MSG_PROCESSING, self._userid, + str(index), str(num_mails)) + + keys = doc.content.keys() + + # TODO Compatibility check with the index in pre-0.6 mx + # that does not write the ERROR_DECRYPTING_KEY + # This should be removed in 0.7 + + has_errors = doc.content.get(fields.ERROR_DECRYPTING_KEY, None) + + if has_errors is None: + warnings.warn("JUST_MAIL_COMPAT_IDX will be deprecated!", + DeprecationWarning) + + if has_errors: + logger.debug("skipping msg with decrypting errors...") + elif self._is_msg(keys): + # TODO this pipeline is a bit obscure! + d = self._decrypt_doc(doc) + d.addCallback(self._maybe_extract_keys) + d.addCallbacks(self._add_message_locally, self._errback) + deferreds.append(d) + + d = defer.gatherResults(deferreds, consumeErrors=True) + d.addCallback(lambda _: doclist) + return d + + # + # operations on individual messages + # + + def _decrypt_doc(self, doc): + """ + Decrypt the contents of a document. + + :param doc: A document containing an encrypted message. + :type doc: SoledadDocument + + :return: A Deferred that will be fired with the document and the + decrypted message. + :rtype: SoledadDocument, str + """ + log.msg('decrypting msg') + + def process_decrypted(res): + if isinstance(res, tuple): + decrdata, _ = res + success = True + else: + decrdata = "" + success = False + + emit_async(catalog.MAIL_MSG_DECRYPTED, self._userid, + "1" if success else "0") + return self._process_decrypted_doc(doc, decrdata) + + d = self._keymanager.decrypt(doc.content[ENC_JSON_KEY], self._userid) + d.addErrback(self._errback) + d.addCallback(process_decrypted) + d.addCallback(lambda data: (doc, data)) + return d + + def _process_decrypted_doc(self, doc, data): + """ + Process a document containing a succesfully decrypted message. + + :param doc: the incoming message + :type doc: SoledadDocument + :param data: the json-encoded, decrypted content of the incoming + message + :type data: str + + :return: a Deferred that will be fired with an str of the proccessed + data. + :rtype: Deferred + """ + log.msg('processing decrypted doc') + + # XXX turn this into an errBack for each one of + # the deferreds that would process an individual document + try: + msg = json_loads(data) + except UnicodeError as exc: + logger.error("Error while decrypting %s" % (doc.doc_id,)) + logger.exception(exc) + + # we flag the message as "with decrypting errors", + # to avoid further decryption attempts during sync + # cycles until we're prepared to deal with that. + # What is the same, when Ivan deals with it... + # A new decrypting attempt event could be triggered by a + # future a library upgrade, or a cli flag to the client, + # we just `defer` that for now... :) + doc.content[fields.ERROR_DECRYPTING_KEY] = True + deferLater(reactor, 0, self._update_incoming_message, doc) + + # FIXME this is just a dirty hack to delay the proper + # deferred organization here... + # and remember, boys, do not do this at home. + return [] + + if not isinstance(msg, dict): + defer.returnValue(False) + if not msg.get(fields.INCOMING_KEY, False): + defer.returnValue(False) + + # ok, this is an incoming message + rawmsg = msg.get(self.CONTENT_KEY, None) + if rawmsg is None: + return "" + return self._maybe_decrypt_msg(rawmsg) + + def _update_incoming_message(self, doc): + """ + Do a put for a soledad document. This probably has been called only + in the case that we've needed to update the ERROR_DECRYPTING_KEY + flag in an incoming message, to get it out of the decrypting queue. + + :param doc: the SoledadDocument to update + :type doc: SoledadDocument + """ + log.msg("Updating Incoming MSG: SoledadDoc %s" % (doc.doc_id)) + return self._soledad.put_doc(doc) + + def _delete_incoming_message(self, doc): + """ + Delete document. + + :param doc: the SoledadDocument to delete + :type doc: SoledadDocument + """ + log.msg("Deleting Incoming message: %s" % (doc.doc_id,)) + return self._soledad.delete_doc(doc) + + def _maybe_decrypt_msg(self, data): + """ + Tries to decrypt a gpg message if data looks like one. + + :param data: the text to be decrypted. + :type data: str + + :return: a Deferred that will be fired with an str of data, possibly + decrypted. + :rtype: Deferred + """ + leap_assert_type(data, str) + log.msg('maybe decrypting doc') + + # parse the original message + encoding = get_email_charset(data) + msg = self._parser.parsestr(data) + + fromHeader = msg.get('from', None) + senderAddress = None + + if (fromHeader is not None and + (msg.get_content_type() == MULTIPART_ENCRYPTED or + msg.get_content_type() == MULTIPART_SIGNED)): + senderAddress = parseaddr(fromHeader)[1] + + def add_leap_header(ret): + decrmsg, signkey = ret + if (senderAddress is None or signkey is None or + isinstance(signkey, keymanager_errors.KeyNotFound)): + decrmsg.add_header( + self.LEAP_SIGNATURE_HEADER, + self.LEAP_SIGNATURE_COULD_NOT_VERIFY) + elif isinstance(signkey, keymanager_errors.InvalidSignature): + decrmsg.add_header( + self.LEAP_SIGNATURE_HEADER, + self.LEAP_SIGNATURE_INVALID) + else: + self._add_verified_signature_header(decrmsg, + signkey.fingerprint) + return decrmsg.as_string() + + if msg.get_content_type() == MULTIPART_ENCRYPTED: + d = self._decrypt_multipart_encrypted_msg( + msg, encoding, senderAddress) + elif msg.get_content_type() == MULTIPART_SIGNED: + d = self._verify_signature_not_encrypted_msg(msg, senderAddress) + else: + d = self._maybe_decrypt_inline_encrypted_msg( + msg, encoding, senderAddress) + d.addCallback(add_leap_header) + return d + + def _add_verified_signature_header(self, decrmsg, fingerprint): + decrmsg.add_header( + self.LEAP_SIGNATURE_HEADER, + self.LEAP_SIGNATURE_VALID, + pubkey=fingerprint) + + def _add_decrypted_header(self, msg): + msg.add_header(self.LEAP_ENCRYPTION_HEADER, + self.LEAP_ENCRYPTION_DECRYPTED) + + def _decrypt_multipart_encrypted_msg(self, msg, encoding, senderAddress): + """ + 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 senderAddress: The email address of the sender of the message. + :type senderAddress: str + + :return: A Deferred that will be fired with a tuple containing a + decrypted Message and the signing OpenPGPKey if the signature + is valid or InvalidSignature or KeyNotFound. + :rtype: Deferred + """ + log.msg('decrypting multipart encrypted msg') + msg = copy.deepcopy(msg) + self._msg_multipart_sanity_check(msg) + + # parse message and get encrypted content + pgpencmsg = msg.get_payload()[1] + encdata = pgpencmsg.get_payload() + + # decrypt or fail gracefully + def build_msg(res): + decrdata, signkey = res + + decrmsg = self._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 + + # all ok, replace payload by unencrypted payload + msg.set_payload(decrmsg.get_payload()) + self._add_decrypted_header(msg) + return (msg, signkey) + + def verify_signature_after_decrypt_an_email(res): + decrdata, signkey = res + if decrdata.get_content_type() == MULTIPART_SIGNED: + res = self._verify_signature_not_encrypted_msg(decrdata, + senderAddress) + return res + + d = self._keymanager.decrypt( + encdata, self._userid, verify=senderAddress) + d.addCallbacks(build_msg, self._decryption_error, errbackArgs=(msg,)) + d.addCallbacks(verify_signature_after_decrypt_an_email) + return d + + def _maybe_decrypt_inline_encrypted_msg(self, origmsg, encoding, + senderAddress): + """ + 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 senderAddress: The email address of the sender of the message. + :type senderAddress: str + + :return: A Deferred that will be fired with a tuple containing a + decrypted Message and the signing OpenPGPKey if the signature + is valid or InvalidSignature or KeyNotFound. + :rtype: Deferred + """ + log.msg('maybe decrypting inline encrypted msg') + + data = self._serialize_msg(origmsg) + + def decrypted_data(res): + decrdata, signkey = res + replaced_data = data.replace(pgp_message, decrdata) + self._add_decrypted_header(origmsg) + return replaced_data, signkey + + def encode_and_return(res): + data, signkey = res + if isinstance(data, unicode): + data = data.encode(encoding, 'replace') + return (self._parser.parsestr(data), signkey) + + # handle exactly one inline PGP message + if PGP_BEGIN in data: + begin = data.find(PGP_BEGIN) + end = data.find(PGP_END) + pgp_message = data[begin:end + len(PGP_END)] + d = self._keymanager.decrypt( + pgp_message, self._userid, verify=senderAddress) + d.addCallbacks(decrypted_data, self._decryption_error, + errbackArgs=(data,)) + else: + d = defer.succeed((data, None)) + d.addCallback(encode_and_return) + return d + + def _verify_signature_not_encrypted_msg(self, origmsg, sender_address): + """ + Possibly decrypt an inline OpenPGP encrypted message. + + :param origmsg: The original, possibly encrypted message. + :type origmsg: Message + :param sender_address: The email address of the sender of the message. + :type sender_address: str + + :return: A Deferred that will be fired with a tuple containing a + signed Message and the signing OpenPGPKey if the signature + is valid or InvalidSignature. + :rtype: Deferred + """ + msg = copy.deepcopy(origmsg) + data = self._serialize_msg(msg.get_payload(0)) + detached_sig = self._extract_signature(msg) + d = self._keymanager.verify(data, sender_address, detached_sig) + + d.addCallback(lambda sign_key: (msg, sign_key)) + d.addErrback(lambda _: (msg, keymanager_errors.InvalidSignature())) + return d + + def _serialize_msg(self, origmsg): + buf = StringIO() + g = Generator(buf) + g.flatten(origmsg) + return buf.getvalue() + + def _extract_signature(self, msg): + body = msg.get_payload(0).get_payload() + + if isinstance(body, str): + body = msg.get_payload(0) + + detached_sig = msg.get_payload(1).get_payload() + msg.set_payload(body) + return detached_sig + + def _decryption_error(self, failure, msg): + """ + Check for known decryption errors + """ + if failure.check(keymanager_errors.DecryptError): + logger.warning('Failed to decrypt encrypted message (%s). ' + 'Storing message without modifications.' + % str(failure.value)) + return (msg, None) + elif failure.check(keymanager_errors.KeyNotFound): + logger.error('Failed to find private key for decryption (%s). ' + 'Storing message without modifications.' + % str(failure.value)) + return (msg, None) + else: + return failure + + @defer.inlineCallbacks + def _maybe_extract_keys(self, msgtuple): + """ + Retrieve attached keys to the mesage and parse message headers for an + *OpenPGP* header as described on the `IETF draft + <http://tools.ietf.org/html/draft-josefsson-openpgp-mailnews-header-06>` + only urls with https and the same hostname than the email are supported + for security reasons. + + :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) + + :return: A Deferred that will be fired with msgtuple when key + extraction finishes + :rtype: Deferred + """ + OpenPGP_HEADER = 'OpenPGP' + doc, data = msgtuple + + # XXX the parsing of the message is done in mailbox.addMessage, maybe + # we should do it in this module so we don't need to parse it again + # here + msg = self._parser.parsestr(data) + _, fromAddress = parseaddr(msg['from']) + + valid_attachment = False + if msg.is_multipart(): + valid_attachment = yield self._maybe_extract_attached_key( + msg.get_payload(), fromAddress) + + if not valid_attachment: + header = msg.get(OpenPGP_HEADER, None) + if header is not None: + yield self._maybe_extract_openpgp_header(header, fromAddress) + + defer.returnValue(msgtuple) + + def _maybe_extract_openpgp_header(self, header, address): + """ + Import keys from the OpenPGP header + + :param header: OpenPGP header string + :type header: str + :param address: email address in the from header + :type address: str + + :return: A Deferred that will be fired when header extraction is done + :rtype: Deferred + """ + d = defer.succeed(None) + fields = dict([f.strip(' ').split('=') for f in header.split(';')]) + if 'url' in fields: + url = shlex.split(fields['url'])[0] # remove quotations + urlparts = urlparse(url) + addressHostname = address.split('@')[1] + if ( + urlparts.scheme == 'https' and + urlparts.hostname == addressHostname + ): + def fetch_error(failure): + if failure.check(keymanager_errors.KeyNotFound): + logger.warning("Url from OpenPGP header %s failed" + % (url,)) + elif failure.check(keymanager_errors.KeyAttributesDiffer): + logger.warning("Key from OpenPGP header url %s didn't " + "match the from address %s" + % (url, address)) + else: + return failure + + d = self._keymanager.fetch_key(address, url) + d.addCallback( + lambda _: + logger.info("Imported key from header %s" % (url,))) + d.addErrback(fetch_error) + else: + logger.debug("No valid url on OpenPGP header %s" % (url,)) + else: + logger.debug("There is no url on the OpenPGP header: %s" + % (header,)) + return d + + def _maybe_extract_attached_key(self, attachments, address): + """ + Import keys from the attachments + + :param attachments: email attachment list + :type attachments: list(email.Message) + :param address: email address in the from header + :type address: str + + :return: A Deferred that will be fired when all the keys are stored + with a boolean: True if there was a valid key attached, or + False otherwise. + :rtype: Deferred + """ + MIME_KEY = "application/pgp-keys" + + def log_key_added(ignored): + logger.debug('Added key found in attachment for %s' % address) + return True + + def failed_put_key(failure): + logger.info("An error has ocurred adding attached key for %s: %s" + % (address, failure.getErrorMessage())) + return False + + deferreds = [] + for attachment in attachments: + if MIME_KEY == attachment.get_content_type(): + d = self._keymanager.put_raw_key( + attachment.get_payload(decode=True), address=address) + d.addCallbacks(log_key_added, failed_put_key) + deferreds.append(d) + d = defer.gatherResults(deferreds) + d.addCallback(lambda result: any(result)) + return d + + def _add_message_locally(self, msgtuple): + """ + Adds a message to local inbox and delete it from the incoming db + in soledad. + + :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) + + :return: A Deferred that will be fired when the messages is stored + :rtype: Defferred + """ + doc, raw_data = msgtuple + insertion_date = formatdate(time.time()) + log.msg('adding message %s to local db' % (doc.doc_id,)) + + def msgSavedCallback(result): + if empty(result): + return + + for listener in self._listeners: + listener(result) + + def signal_deleted(doc_id): + emit_async(catalog.MAIL_MSG_DELETED_INCOMING, + self._userid) + return doc_id + + emit_async(catalog.MAIL_MSG_SAVED_LOCALLY, self._userid) + d = self._delete_incoming_message(doc) + d.addCallback(signal_deleted) + return d + + d = self._inbox_collection.add_msg( + raw_data, (self.RECENT_FLAG,), date=insertion_date, + notify_just_mdoc=True) + d.addCallbacks(msgSavedCallback, self._errback) + return d + + # + # helpers + # + + def _msg_multipart_sanity_check(self, msg): + """ + Performs a sanity check against a multipart encrypted msg + + :param msg: The original encrypted message. + :type msg: Message + """ + # 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()) + + def _is_msg(self, keys): + """ + Checks if the keys of a dictionary match the signature + of the document type we use for messages. + + :param keys: iterable containing the strings to match. + :type keys: iterable of strings. + :rtype: bool + """ + return ENC_SCHEME_KEY in keys and ENC_JSON_KEY in keys |