#!/usr/bin/env python3 # -*- coding: utf-8 -*- """ Slixmpp OMEMO plugin Copyright (C) 2019 Maxime “pep” Buquet This file is part of slixmpp-omemo. See the file LICENSE for copying permission. """ import logging from typing import Any, Dict, List, Optional, Set, Tuple, Union import os import json import base64 import codecs import asyncio from slixmpp.plugins.xep_0060.stanza import Items, EventItems from slixmpp.plugins.xep_0004 import Form from slixmpp.plugins.base import BasePlugin, register_plugin from slixmpp.exceptions import IqError, IqTimeout from slixmpp.stanza import Message, Iq from slixmpp.jid import JID from .version import __version__, __version_info__ from .stanza import OMEMO_BASE_NS from .stanza import OMEMO_DEVICES_NS, OMEMO_BUNDLES_NS from .stanza import Bundle, Devices, Device, Encrypted, Key, PreKeyPublic log = logging.getLogger(__name__) HAS_OMEMO = True try: import omemo.exceptions from omemo import SessionManager, ExtendedPublicBundle, DefaultOTPKPolicy from omemo.util import generateDeviceID from omemo.implementations import JSONFileStorage from omemo.backends import Backend from omemo_backend_signal import BACKEND as SignalBackend except (ImportError,): class Backend: pass class DefaultOTPKPolicy: pass class SignalBackend: pass HAS_OMEMO = False TRUE_VALUES = {True, 'true', '1'} PUBLISH_OPTIONS_NODE = 'http://jabber.org/protocol/pubsub#publish-options' PUBSUB_ERRORS = 'http://jabber.org/protocol/pubsub#errors' def b64enc(data: bytes) -> str: return base64.b64encode(bytes(bytearray(data))).decode('ASCII') def b64dec(data: str) -> bytes: return base64.b64decode(data) def _load_device_id(data_dir: str) -> int: filepath = os.path.join(data_dir, 'device_id.json') # Try reading file first, decoding, and if file was empty generate # new DeviceID try: with open(filepath, 'r') as f: did = json.load(f) except (FileNotFoundError, json.JSONDecodeError): did = generateDeviceID() with open(filepath, 'w') as f: json.dump(did, f) return did def fp_from_ik(identity_key: bytes) -> str: """Convert identityKey to a string representation (fingerprint)""" return codecs.getencoder("hex")(identity_key)[0].decode("US-ASCII").upper() def _parse_bundle(backend: Backend, bundle: Bundle) -> ExtendedPublicBundle: identity_key = b64dec(bundle['identityKey']['value'].strip()) spk = { 'id': int(bundle['signedPreKeyPublic']['signedPreKeyId']), 'key': b64dec(bundle['signedPreKeyPublic']['value'].strip()), } spk_signature = b64dec(bundle['signedPreKeySignature']['value'].strip()) otpks = [] for prekey in bundle['prekeys']: otpks.append({ 'id': int(prekey['preKeyId']), 'key': b64dec(prekey['value'].strip()), }) return ExtendedPublicBundle.parse(backend, identity_key, spk, spk_signature, otpks) def _generate_encrypted_payload(encrypted) -> Encrypted: tag = Encrypted() tag['header']['sid'] = str(encrypted['sid']) tag['header']['iv']['value'] = b64enc(encrypted['iv']) tag['payload']['value'] = b64enc(encrypted['payload']) for bare_jid, devices in encrypted['keys'].items(): for rid, device in devices.items(): key = Key() key['value'] = b64enc(device['data']) key['rid'] = str(rid) if device['pre_key']: key['prekey'] = '1' tag['header'].append(key) return tag def _make_publish_options_form(fields: Dict[str, Any]) -> Form: options = Form() options['type'] = 'submit' options.add_field( var='FORM_TYPE', ftype='hidden', value='http://jabber.org/protocol/pubsub#publish-options', ) for var, value in fields.items(): options.add_field(var=var, value=value) return options # XXX: This should probably be moved in plugins/base.py? class PluginCouldNotLoad(Exception): pass # Generic exception class XEP0384(Exception): pass class MissingOwnKey(XEP0384): pass class NoAvailableSession(XEP0384): pass class EncryptionPrepareException(XEP0384): def __init__(self, errors): self.errors = errors class UntrustedException(XEP0384): def __init__(self, bare_jid, device, ik): self.bare_jid = JID(bare_jid) self.device = device self.ik = ik class UndecidedException(XEP0384): def __init__(self, bare_jid, device, ik): self.bare_jid = JID(bare_jid) self.device = device self.ik = ik class XEP_0384(BasePlugin): """ XEP-0384: OMEMO """ name = 'xep_0384' description = 'XEP-0384 OMEMO' dependencies = {'xep_0004', 'xep_0060', 'xep_0163'} default_config = { 'data_dir': None, 'storage_backend': None, 'otpk_policy': DefaultOTPKPolicy, 'omemo_backend': SignalBackend, } backend_loaded = HAS_OMEMO # OMEMO Bundles used for encryption bundles = {} # type: Dict[str, Dict[int, ExtendedPublicBundle]] def plugin_init(self) -> None: if not self.backend_loaded: log.info("xep_0384 cannot be loaded as the backend omemo library " "is not available") raise PluginCouldNotLoad if not self.data_dir: log.info("xep_0384 cannot be loaded as there is not data directory " "specified") return None storage = self.storage_backend if self.storage_backend is None: storage = JSONFileStorage(self.data_dir) otpkpolicy = self.otpk_policy bare_jid = self.xmpp.boundjid.bare self._device_id = _load_device_id(self.data_dir) try: self._omemo = SessionManager.create( storage, otpkpolicy, self.omemo_backend, bare_jid, self._device_id, ) except: log.error("Couldn't load the OMEMO object; ¯\\_(ツ)_/¯") raise PluginCouldNotLoad self.xmpp.add_event_handler('session_start', self.session_start) self.xmpp['xep_0060'].map_node_event(OMEMO_DEVICES_NS, 'omemo_device_list') self.xmpp.add_event_handler('omemo_device_list_publish', self._receive_device_list) return None def plugin_end(self): if not self.backend_loaded: return self.xmpp.remove_event_handler('session_start', self.session_start) self.xmpp.remove_event_handler('omemo_device_list_publish', self._receive_device_list) self.xmpp['xep_0163'].remove_interest(OMEMO_DEVICES_NS) async def session_start(self, _jid): if self.backend_loaded: self.xmpp['xep_0163'].add_interest(OMEMO_DEVICES_NS) await asyncio.wait([ self._set_device_list(), self._publish_bundle(), ]) def my_device_id(self) -> int: return self._device_id def _set_node_config( self, node: str, persist_items: bool = True, access_model: Optional[str] = None, ) -> asyncio.Future: """ Sets OMEMO devicelist or bundle node configuration. This function is meant to be used once we've tried publish options and they came back with precondition-not-met. This means an existing node is not using our defaults. By default this function will be overwriting pubsub#persist_items only, leaving pubsub#access_model as it was. To be complete, the code using this function should probably set the bundle node to the same access_model as the devicelist node. """ form = Form() form['type'] = 'submit' form.add_field( var='FORM_TYPE', ftype='hidden', value='http://jabber.org/protocol/pubsub#node_config', ) if persist_items: form.add_field( var='pubsub#persist_items', ftype='boolean', value=True, ) if access_model is not None: form.add_field( var='FORM_TYPE', ftype='text-single', value=access_model, ) return self.xmpp['xep_0060'].set_node_config( self.xmpp.boundjid.bare, node, form, ) async def _generate_bundle_iq(self) -> Iq: bundle = self._omemo.public_bundle.serialize(self.omemo_backend) jid = self.xmpp.boundjid disco = await self.xmpp['xep_0030'].get_info(jid.bare) publish_options = PUBLISH_OPTIONS_NODE in disco['disco_info'].get_features() iq = self.xmpp.Iq(stype='set') publish = iq['pubsub']['publish'] publish['node'] = '%s:%d' % (OMEMO_BUNDLES_NS, self._device_id) payload = publish['item']['bundle'] signedPreKeyPublic = b64enc(bundle['spk']['key']) payload['signedPreKeyPublic']['value'] = signedPreKeyPublic payload['signedPreKeyPublic']['signedPreKeyId'] = str(bundle['spk']['id']) payload['signedPreKeySignature']['value'] = b64enc( bundle['spk_signature'] ) identityKey = b64enc(bundle['ik']) payload['identityKey']['value'] = identityKey prekeys = [] for otpk in bundle['otpks']: prekey = PreKeyPublic() prekey['preKeyId'] = str(otpk['id']) prekey['value'] = b64enc(otpk['key']) prekeys.append(prekey) payload['prekeys'] = prekeys if publish_options: options = _make_publish_options_form({ 'pubsub#persist_items': True, 'pubsub#access_model': 'open', }) iq['pubsub']['publish_options'] = options return iq async def _publish_bundle(self) -> None: if self._omemo.republish_bundle: iq = await self._generate_bundle_iq() try: await iq.send() except IqError as e: # TODO: Slixmpp should handle pubsub#errors so we don't have to # fish the element ourselves precondition = e.iq['error'].xml.find( '{%s}%s' % (PUBSUB_ERRORS, 'precondition-not-met'), ) if precondition is not None: log.debug('The node we tried to publish was already ' 'existing with a different configuration. ' 'Trying to configure manually..') # TODO: We should attempt setting this node to the same # access_model as the devicelist node for completness. await self._set_node_config(OMEMO_BUNDLES_NS) async def _fetch_bundle(self, jid: str, device_id: int) -> Optional[ExtendedPublicBundle]: node = '%s:%d' % (OMEMO_BUNDLES_NS, device_id) try: iq = await self.xmpp['xep_0060'].get_items(jid, node) except (IqError, IqTimeout): return None bundle = iq['pubsub']['items']['item']['bundle'] return _parse_bundle(self.omemo_backend, bundle) async def _fetch_device_list(self, jid: JID) -> None: """Manually query PEP OMEMO_DEVICES_NS nodes""" jid = JID(jid) iq = await self.xmpp['xep_0060'].get_items(jid, OMEMO_DEVICES_NS) return await self._read_device_list(jid, iq['pubsub']['items']) def _store_device_ids(self, jid: str, items: Union[Items, EventItems]) -> None: """Store Device list""" device_ids = [] # type: List[int] items = list(items) if items: device_ids = [int(d['id']) for d in items[0]['devices']] return self._omemo.newDeviceList(str(jid), device_ids) def _receive_device_list(self, msg: Message) -> None: """Handler for received PEP OMEMO_DEVICES_NS payloads""" asyncio.ensure_future( self._read_device_list(msg['from'], msg['pubsub_event']['items']), ) async def _read_device_list(self, jid: JID, items: Union[Items, EventItems]) -> None: """Read items and devices if we need to set the device list again or not""" bare_jid = jid.bare self._store_device_ids(bare_jid, items) items = list(items) device_ids = [] if items: device_ids = [int(d['id']) for d in items[0]['devices']] if bare_jid == self.xmpp.boundjid.bare and \ self._device_id not in device_ids: await self._set_device_list() return None async def _set_device_list(self, device_ids: Optional[Set[int]] = None) -> None: own_jid = self.xmpp.boundjid try: iq = await self.xmpp['xep_0060'].get_items( own_jid.bare, OMEMO_DEVICES_NS, ) items = iq['pubsub']['items'] self._store_device_ids(own_jid.bare, items) except IqError as iq_err: if iq_err.condition == "item-not-found": self._store_device_ids(own_jid.bare, []) else: return # XXX: Handle this! if device_ids is None: device_ids = self.get_device_list(own_jid) devices = [] for i in device_ids: d = Device() d['id'] = str(i) devices.append(d) payload = Devices() payload['devices'] = devices jid = self.xmpp.boundjid disco = await self.xmpp['xep_0030'].get_info(jid.bare) publish_options = PUBLISH_OPTIONS_NODE in disco['disco_info'].get_features() if publish_options: options = _make_publish_options_form({ 'pubsub#persist_items': True, # Everybody will be able to encrypt for us, without having to add # us into their roster. This obviously leaks the number of devices # and the associated metadata of us pushing new device lists every # so often. 'pubsub#access_model': 'open', }) try: await self.xmpp['xep_0060'].publish( own_jid.bare, OMEMO_DEVICES_NS, payload=payload, options=options, ) except IqError as e: # TODO: Slixmpp should handle pubsub#errors so we don't have to # fish the element ourselves precondition = e.iq['error'].xml.find( '{%s}%s' % (PUBSUB_ERRORS, 'precondition-not-met'), ) if precondition is not None: log.debug('The node we tried to publish was already ' 'existing with a different configuration. ' 'Trying to configure manually..') await self._set_node_config(OMEMO_DEVICES_NS) def get_device_list(self, jid: JID) -> List[str]: """Return active device ids. Always contains our own device id.""" return self._omemo.getDevices(jid.bare).get('active', []) def trust(self, jid: JID, device_id: int, ik: bytes) -> None: self._omemo.setTrust(jid.bare, device_id, ik, True) def distrust(self, jid: JID, device_id: int, ik: bytes) -> None: self._omemo.setTrust(jid.bare, device_id, ik, False) def get_trust_for_jid(self, jid: JID) -> Dict[str, List[Optional[Dict[str, Any]]]]: """ Fetches trust for JID. The returned dictionary will contain active and inactive devices. Each of these dict will contain device ids as keys, and a dict with 'key', 'trust' as values that can also be None. Example: { 'active': { 123456: { 'key': bytes, 'trust': bool, } } 'inactive': { 234567: None, } } """ return self._omemo.getTrustForJID(jid.bare) def is_encrypted(self, msg: Message) -> bool: return msg.xml.find('{%s}encrypted' % OMEMO_BASE_NS) is not None def decrypt_message( self, encrypted: Encrypted, sender: JID, allow_untrusted: bool = False, ) -> Optional[str]: header = encrypted['header'] payload = b64dec(encrypted['payload']['value']) jid = sender.bare sid = int(header['sid']) key = header.xml.find("{%s}key[@rid='%s']" % ( OMEMO_BASE_NS, self._device_id)) if key is None: raise MissingOwnKey("Encrypted message is not for us") key = Key(key) isPrekeyMessage = key['prekey'] in TRUE_VALUES message = b64dec(key['value']) iv = b64dec(header['iv']['value']) # XXX: 'cipher' is part of KeyTransportMessages and is used when no payload # is passed. We do not implement this yet. try: body = self._omemo.decryptMessage( jid, sid, iv, message, isPrekeyMessage, payload, allow_untrusted=allow_untrusted, ) return body except (omemo.exceptions.NoSessionException,): # This might happen when the sender is sending using a session # that we don't know about (deleted session storage, etc.). In # this case we can't decrypt the message and it's going to be lost # in any case, but we want to tell the user, always. raise NoAvailableSession(jid, sid) except (omemo.exceptions.TrustException,) as exn: if exn.problem == 'undecided': raise UndecidedException(exn.bare_jid, exn.device, exn.ik) if exn.problem == 'untrusted': raise UntrustedException(exn.bare_jid, exn.device, exn.ik) raise finally: asyncio.ensure_future(self._publish_bundle()) async def encrypt_message( self, plaintext: str, recipients: List[JID], expect_problems: Optional[Dict[JID, List[int]]] = None, ) -> Encrypted: """ Returns an encrypted payload to be placed into a message. The API for getting an encrypted payload consists of trying first and fixing errors progressively. The actual sending happens once the application (us) thinks we're good to go. """ recipients = [jid.bare for jid in recipients] old_errors = None # type: Optional[List[Tuple[Exception, Any, Any]]] while True: # Try to encrypt and resolve errors until there is no error at all # or if we hit the same set of errors. errors = [] # type: List[omemo.exceptions.OMEMOException] if expect_problems is not None: expect_problems = {jid.bare: did for (jid, did) in expect_problems.items()} try: encrypted = self._omemo.encryptMessage( recipients, plaintext.encode('utf-8'), self.bundles, expect_problems=expect_problems, ) return _generate_encrypted_payload(encrypted) except omemo.exceptions.EncryptionProblemsException as exn: errors = exn.problems if errors == old_errors: raise EncryptionPrepareException(errors) old_errors = errors for exn in errors: if isinstance(exn, omemo.exceptions.NoDevicesException): await self._fetch_device_list(exn.bare_jid) elif isinstance(exn, omemo.exceptions.MissingBundleException): bundle = await self._fetch_bundle(exn.bare_jid, exn.device) if bundle is not None: devices = self.bundles.setdefault(exn.bare_jid, {}) devices[exn.device] = bundle elif isinstance(exn, omemo.exceptions.TrustException): # On TrustException, there are two possibilities. # Either trust has not been explicitely set yet, and is # 'undecided', or the device is explicitely not # trusted. When undecided, we need to ask our user to make # a choice. If untrusted, then we can safely tell the # OMEMO lib to not encrypt to this device if exn.problem == 'undecided': raise UndecidedException(exn.bare_jid, exn.device, exn.ik) expect_problems.setdefault(exn.bare_jid, []).append(exn.device) elif isinstance(exn, omemo.exceptions.NoEligibleDevicesException): # This error is returned by the library to specify that # encryption is not possible to any device of a user. # This always comes with a more specific exception, (empty # device list, missing bundles, trust issues, etc.). # This does the heavy lifting of state management, and # seeing if it's possible to encrypt at all, or not. # This exception is only passed to the user, that should # decide what to do with it, as there isn't much we can if # other issues can't be resolved. continue register_plugin(XEP_0384)