453 lines
16 KiB
Python
453 lines
16 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Slixmpp OMEMO plugin
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Copyright (C) 2019 Maxime “pep” Buquet <pep@bouah.net>
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This file is part of slixmpp-omemo.
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See the file LICENSE for copying permission.
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"""
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import logging
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from typing import Any, Dict, List, Optional, Set, Tuple, Union
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import os
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import json
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import base64
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import asyncio
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from slixmpp.plugins.xep_0060.stanza import Items, EventItems
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from slixmpp.plugins.base import BasePlugin, register_plugin
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from slixmpp.exceptions import IqError, IqTimeout
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from slixmpp.stanza import Message, Iq
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from slixmpp.jid import JID
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from .version import __version__, __version_info__
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from .stanza import OMEMO_BASE_NS
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from .stanza import OMEMO_DEVICES_NS, OMEMO_BUNDLES_NS
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from .stanza import Bundle, Devices, Device, Encrypted, Key, PreKeyPublic
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log = logging.getLogger(__name__)
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HAS_OMEMO = True
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try:
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import omemo.exceptions
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from omemo import SessionManager, ExtendedPublicBundle, DefaultOTPKPolicy
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from omemo.util import generateDeviceID
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from omemo.implementations import JSONFileStorage
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from omemo.backends import Backend
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from omemo_backend_signal import BACKEND as SignalBackend
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except (ImportError,):
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class Backend:
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pass
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class DefaultOTPKPolicy:
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pass
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class SignalBackend:
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pass
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HAS_OMEMO = False
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TRUE_VALUES = {True, 'true', '1'}
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def b64enc(data: bytes) -> str:
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return base64.b64encode(bytes(bytearray(data))).decode('ASCII')
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def b64dec(data: str) -> bytes:
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return base64.b64decode(data)
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def _load_device_id(data_dir: str) -> int:
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filepath = os.path.join(data_dir, 'device_id.json')
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# Try reading file first, decoding, and if file was empty generate
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# new DeviceID
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try:
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with open(filepath, 'r') as f:
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did = json.load(f)
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except (FileNotFoundError, json.JSONDecodeError):
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did = generateDeviceID()
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with open(filepath, 'w') as f:
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json.dump(did, f)
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return did
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def _parse_bundle(backend: Backend, bundle: Bundle) -> ExtendedPublicBundle:
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identity_key = b64dec(bundle['identityKey']['value'].strip())
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spk = {
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'id': int(bundle['signedPreKeyPublic']['signedPreKeyId']),
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'key': b64dec(bundle['signedPreKeyPublic']['value'].strip()),
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}
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spk_signature = b64dec(bundle['signedPreKeySignature']['value'].strip())
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otpks = []
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for prekey in bundle['prekeys']:
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otpks.append({
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'id': int(prekey['preKeyId']),
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'key': b64dec(prekey['value'].strip()),
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})
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return ExtendedPublicBundle.parse(backend, identity_key, spk, spk_signature, otpks)
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def _generate_encrypted_payload(encrypted) -> Encrypted:
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tag = Encrypted()
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tag['header']['sid'] = str(encrypted['sid'])
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tag['header']['iv']['value'] = b64enc(encrypted['iv'])
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tag['payload']['value'] = b64enc(encrypted['payload'])
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for bare_jid, devices in encrypted['keys'].items():
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for rid, device in devices.items():
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key = Key()
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key['value'] = b64enc(device['data'])
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key['rid'] = str(rid)
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if device['pre_key']:
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key['prekey'] = '1'
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tag['header'].append(key)
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return tag
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# XXX: This should probably be moved in plugins/base.py?
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class PluginCouldNotLoad(Exception): pass
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# Generic exception
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class XEP0384(Exception): pass
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class MissingOwnKey(XEP0384): pass
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class NoAvailableSession(XEP0384): pass
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class EncryptionPrepareException(XEP0384): pass
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class UntrustedException(XEP0384):
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def __init__(self, bare_jid, device, ik):
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self.bare_jid = JID(bare_jid)
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self.device = device
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self.ik = ik
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class UndecidedException(XEP0384):
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def __init__(self, bare_jid, device, ik):
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self.bare_jid = JID(bare_jid)
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self.device = device
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self.ik = ik
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class XEP_0384(BasePlugin):
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"""
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XEP-0384: OMEMO
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"""
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name = 'xep_0384'
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description = 'XEP-0384 OMEMO'
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dependencies = {'xep_0163'}
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default_config = {
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'data_dir': None,
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'storage_backend': None,
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'otpk_policy': DefaultOTPKPolicy,
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'omemo_backend': SignalBackend,
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}
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backend_loaded = HAS_OMEMO
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def plugin_init(self) -> None:
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if not self.backend_loaded:
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log.info("xep_0384 cannot be loaded as the backend omemo library "
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"is not available")
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raise PluginCouldNotLoad
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if not self.data_dir:
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log.info("xep_0384 cannot be loaded as there is not data directory "
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"specified")
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return None
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storage = self.storage_backend
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if self.storage_backend is None:
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storage = JSONFileStorage(self.data_dir)
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otpkpolicy = self.otpk_policy
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bare_jid = self.xmpp.boundjid.bare
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self._device_id = _load_device_id(self.data_dir)
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try:
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self._omemo = SessionManager.create(
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storage,
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otpkpolicy,
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self.omemo_backend,
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bare_jid,
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self._device_id,
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)
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except:
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log.error("Couldn't load the OMEMO object; ¯\\_(ツ)_/¯")
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raise PluginCouldNotLoad
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self.xmpp['xep_0060'].map_node_event(OMEMO_DEVICES_NS, 'omemo_device_list')
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self.xmpp.add_event_handler('omemo_device_list_publish', self._receive_device_list)
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return None
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def plugin_end(self):
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if not self.backend_loaded:
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return
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self.xmpp.remove_event_handler('omemo_device_list_publish', self._receive_device_list)
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self.xmpp['xep_0163'].remove_interest(OMEMO_DEVICES_NS)
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def session_bind(self, _jid):
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if self.backend_loaded:
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self.xmpp['xep_0163'].add_interest(OMEMO_DEVICES_NS)
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asyncio.ensure_future(self._set_device_list())
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asyncio.ensure_future(self._publish_bundle())
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def my_device_id(self) -> int:
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return self._device_id
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def _generate_bundle_iq(self) -> Iq:
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bundle = self._omemo.public_bundle.serialize(self.omemo_backend)
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iq = self.xmpp.Iq(stype='set')
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publish = iq['pubsub']['publish']
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publish['node'] = '%s:%d' % (OMEMO_BUNDLES_NS, self._device_id)
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payload = publish['item']['bundle']
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signedPreKeyPublic = b64enc(bundle['spk']['key'])
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payload['signedPreKeyPublic']['value'] = signedPreKeyPublic
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payload['signedPreKeyPublic']['signedPreKeyId'] = str(bundle['spk']['id'])
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payload['signedPreKeySignature']['value'] = b64enc(
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bundle['spk_signature']
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)
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identityKey = b64enc(bundle['ik'])
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payload['identityKey']['value'] = identityKey
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prekeys = []
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for otpk in bundle['otpks']:
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prekey = PreKeyPublic()
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prekey['preKeyId'] = str(otpk['id'])
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prekey['value'] = b64enc(otpk['key'])
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prekeys.append(prekey)
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payload['prekeys'] = prekeys
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return iq
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async def _publish_bundle(self) -> None:
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if self._omemo.republish_bundle:
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iq = self._generate_bundle_iq()
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await iq.send()
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async def _fetch_bundle(self, jid: str, device_id: int) -> Optional[ExtendedPublicBundle]:
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node = '%s:%d' % (OMEMO_BUNDLES_NS, device_id)
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try:
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iq = await self.xmpp['xep_0060'].get_items(jid, node)
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except (IqError, IqTimeout):
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return None
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bundle = iq['pubsub']['items']['item']['bundle']
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return _parse_bundle(self._omemo, bundle)
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async def _fetch_device_list(self, jid: JID) -> None:
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"""Manually query PEP OMEMO_DEVICES_NS nodes"""
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jid = JID(jid)
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iq = await self.xmpp['xep_0060'].get_items(jid, OMEMO_DEVICES_NS)
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return await self._read_device_list(jid, iq['pubsub']['items'])
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def _store_device_ids(self, jid: str, items: Union[Items, EventItems]) -> None:
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"""Store Device list"""
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device_ids = [] # type: List[int]
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items = list(items)
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device_ids = [int(d['id']) for d in items[0]['devices']]
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return self._omemo.newDeviceList(str(jid), device_ids)
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def _receive_device_list(self, msg: Message) -> None:
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"""Handler for received PEP OMEMO_DEVICES_NS payloads"""
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asyncio.ensure_future(
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self._read_device_list(msg['from'],
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msg['pubsub_event']['items']),
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)
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async def _read_device_list(self, jid: JID, items: Union[Items, EventItems]) -> None:
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"""Read items and devices if we need to set the device list again or not"""
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bare_jid = jid.bare
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self._store_device_ids(bare_jid, items)
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items = list(items)
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device_ids = [int(d['id']) for d in items[0]['devices']]
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if bare_jid == self.xmpp.boundjid.bare and \
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self._device_id not in device_ids:
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await self._set_device_list()
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return None
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async def _set_device_list(self, device_ids: Optional[Set[int]] = None) -> None:
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own_jid = self.xmpp.boundjid
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try:
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iq = await self.xmpp['xep_0060'].get_items(
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own_jid.bare, OMEMO_DEVICES_NS,
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)
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items = iq['pubsub']['items']
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self._store_device_ids(own_jid.bare, items)
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except IqError as iq_err:
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if iq_err.condition == "item-not-found":
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self._store_device_ids(own_jid.bare, [])
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else:
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return # XXX: Handle this!
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if device_ids is None:
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device_ids = self.get_device_list(own_jid)
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devices = []
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for i in device_ids:
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d = Device()
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d['id'] = str(i)
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devices.append(d)
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payload = Devices()
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payload['devices'] = devices
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await self.xmpp['xep_0060'].publish(
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own_jid.bare, OMEMO_DEVICES_NS, payload=payload,
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)
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def get_device_list(self, jid: JID) -> List[str]:
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"""Return active device ids. Always contains our own device id."""
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return self._omemo.getDevices(jid.bare).get('active', [])
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def trust(self, jid: JID, device_id: int, ik: bytes) -> None:
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self._omemo.trust(jid.bare, device_id, ik)
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def distrust(self, jid: JID, device_id: int, ik: bytes) -> None:
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self._omemo.distrust(jid.bare, device_id, ik)
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def is_encrypted(self, msg: Message) -> bool:
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return msg.xml.find('{%s}encrypted' % OMEMO_BASE_NS) is not None
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def decrypt_message(self, msg: Message, allow_untrusted: bool = False) -> Optional[str]:
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header = msg['omemo_encrypted']['header']
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payload = b64dec(msg['omemo_encrypted']['payload']['value'])
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jid = msg['from'].bare
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sid = int(header['sid'])
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key = header.xml.find("{%s}key[@rid='%s']" % (
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OMEMO_BASE_NS, self._device_id))
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if key is None:
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raise MissingOwnKey("Encrypted message is not for us")
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key = Key(key)
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isPrekeyMessage = key['prekey'] in TRUE_VALUES
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message = b64dec(key['value'])
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iv = b64dec(header['iv']['value'])
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# XXX: 'cipher' is part of KeyTransportMessages and is used when no payload
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# is passed. We do not implement this yet.
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try:
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body = self._omemo.decryptMessage(
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jid,
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sid,
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iv,
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message,
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isPrekeyMessage,
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payload,
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allow_untrusted=allow_untrusted,
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)
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return body
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except (omemo.exceptions.NoSessionException,):
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# This might happen when the sender is sending using a session
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# that we don't know about (deleted session storage, etc.). In
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# this case we can't decrypt the message and it's going to be lost
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# in any case, but we want to tell the user, always.
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raise NoAvailableSession(jid, sid)
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except (omemo.exceptions.TrustException,) as exn:
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if exn.problem == 'undecided':
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raise UndecidedException(exn.bare_jid, exn.device, exn.ik)
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elif exn.problem == 'untrusted':
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raise UntrustedException(exn.bare_jid, exn.device, exn.ik)
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raise
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finally:
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asyncio.ensure_future(self._publish_bundle())
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async def encrypt_message(
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self,
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plaintext: str,
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recipients: List[JID],
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expect_problems: Optional[Dict[JID, List[int]]] = None,
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) -> Encrypted:
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"""
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Returns an encrypted payload to be placed into a message.
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The API for getting an encrypted payload consists of trying first
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and fixing errors progressively. The actual sending happens once the
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application (us) thinks we're good to go.
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"""
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recipients = [jid.bare for jid in recipients]
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bundles = {} # type: Dict[str, Dict[int, ExtendedPublicBundle]]
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old_errors = None # type: Optional[List[Tuple[Exception, Any, Any]]]
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while True:
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# Try to encrypt and resolve errors until there is no error at all
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# or if we hit the same set of errors.
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errors = [] # type: List[omemo.exceptions.OMEMOException]
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if expect_problems is not None:
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expect_problems = {jid.bare: did for (jid, did) in expect_problems.items()}
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try:
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encrypted = self._omemo.encryptMessage(
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recipients,
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plaintext.encode('utf-8'),
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bundles,
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expect_problems=expect_problems,
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)
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return _generate_encrypted_payload(encrypted)
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except omemo.exceptions.EncryptionProblemsException as e:
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errors = e.problems
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if errors == old_errors:
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raise EncryptionPrepareException(errors)
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old_errors = errors
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no_eligible_devices = set() # type: Set[str]
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for exn in errors:
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if isinstance(exn, omemo.exceptions.NoDevicesException):
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await self._fetch_device_list(exn.bare_jid)
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elif isinstance(exn, omemo.exceptions.MissingBundleException):
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bundle = await self._fetch_bundle(exn.bare_jid, exn.device)
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if bundle is not None:
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devices = bundles.setdefault(exn.bare_jid, {})
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devices[exn.device] = bundle
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elif isinstance(exn, omemo.exceptions.TrustException):
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# On TrustException, there are two possibilities.
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# Either trust has not been explicitely set yet, and is
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# 'undecided', or the device is explicitely not
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# trusted. When undecided, we need to ask our user to make
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# a choice. If untrusted, then we can safely tell the
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# OMEMO lib to not encrypt to this device
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if exn.problem == 'undecided':
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raise UndecidedException(exn.bare_jid, exn.device, exn.ik)
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expect_problems.setdefault(exn.bare_jid, []).append(exn.device)
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elif isinstance(exn, omemo.exceptions.NoEligibleDevicesException):
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# This error is returned by the library to specify that
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# encryption is not possible to any device of a user.
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# This always comes with a more specific exception, (empty
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# device list, missing bundles, trust issues, etc.).
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# This does the heavy lifting of state management, and
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# seeing if it's possible to encrypt at all, or not.
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# This exception is only passed to the user, that should
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# decide what to do with it, as there isn't much we can if
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# other issues can't be resolved.
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continue
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register_plugin(XEP_0384)
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