#!/usr/bin/env python3

# SAT plugin for OMEMO encryption
# Copyright (C) 2009-2020 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero 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 Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from sat.core.i18n import _, D_
from sat.core.constants import Const as C
from sat.core.log import getLogger
from sat.core import exceptions
from twisted.internet import defer, reactor
from twisted.words.xish import domish
from twisted.words.protocols.jabber import jid
from twisted.words.protocols.jabber import error
from sat.memory import persistent
from functools import partial
from sat.tools import xml_tools
import logging
import random
import base64
try:
    import omemo
    from omemo import exceptions as omemo_excpt
    from omemo.extendedpublicbundle import ExtendedPublicBundle
except ImportError:
    raise exceptions.MissingModule(
        'Missing module omemo, please download/install it. You can use '
        '"pip install omemo"'
    )
try:
    from omemo_backend_signal import BACKEND as omemo_backend
except ImportError:
    raise exceptions.MissingModule(
        'Missing module omemo-backend-signal, please download/install it. You can use '
        '"pip install omemo-backend-signal"'
    )

log = getLogger(__name__)

PLUGIN_INFO = {
    C.PI_NAME: "OMEMO",
    C.PI_IMPORT_NAME: "XEP-0384",
    C.PI_TYPE: "SEC",
    C.PI_PROTOCOLS: ["XEP-0384"],
    C.PI_DEPENDENCIES: ["XEP-0163", "XEP-0280", "XEP-0334", "XEP-0060"],
    C.PI_RECOMMENDATIONS: ["XEP-0045", "XEP-0359"],
    C.PI_MAIN: "OMEMO",
    C.PI_HANDLER: "no",
    C.PI_DESCRIPTION: _("""Implementation of OMEMO"""),
}

OMEMO_MIN_VER = (0, 11, 0)
NS_OMEMO = "eu.siacs.conversations.axolotl"
NS_OMEMO_DEVICES = NS_OMEMO + ".devicelist"
NS_OMEMO_BUNDLE = NS_OMEMO + ".bundles:{device_id}"
KEY_STATE = "STATE"
KEY_DEVICE_ID = "DEVICE_ID"
KEY_SESSION = "SESSION"
KEY_TRUST = "TRUST"
KEY_ACTIVE_DEVICES = "DEVICES"
KEY_INACTIVE_DEVICES = "INACTIVE_DEVICES"
KEY_ALL_JIDS = "ALL_JIDS"
# time before plaintext cache for MUC is expired
# expressed in seconds, reset on each new MUC message
MUC_CACHE_TTL = 60 * 5


# we want to manage log emitted by omemo module ourselves

class SatHandler(logging.Handler):

    def emit(self, record):
        log.log(record.levelname, record.getMessage())

    @staticmethod
    def install():
        omemo_sm_logger = logging.getLogger("omemo.SessionManager")
        omemo_sm_logger.propagate = False
        omemo_sm_logger.addHandler(SatHandler())


SatHandler.install()


def b64enc(data):
    return base64.b64encode(bytes(bytearray(data))).decode("US-ASCII")


def promise2Deferred(promise_):
    """Create a Deferred and fire it when promise is resolved

    @param promise_(promise.Promise): promise to convert
    @return (defer.Deferred): deferred instance linked to the promise
    """
    d = defer.Deferred()
    promise_.then(d.callback, d.errback)
    return d


class OmemoStorage(omemo.Storage):

    def __init__(self, client, device_id, all_jids, persistent_dict):
        """
        @param persistent_dict(persistent.LazyPersistentBinaryDict): object which will
            store data in SàT database
        """
        self.own_bare_jid_s = client.jid.userhost()
        self.device_id = device_id
        self.all_jids = all_jids
        self.data = persistent_dict

    @property
    def is_async(self):
        return True

    def setCb(self, deferred, callback):
        """Associate Deferred and callback

        callback of omemo.Storage expect a boolean with success state then result
        Deferred on the other hand use 2 methods for callback and errback
        This method use partial to call callback with boolean then result when
        Deferred is called
        """
        deferred.addCallback(partial(callback, True))
        deferred.addErrback(partial(callback, False))

    def _checkJid(self, bare_jid):
        """Check if jid is know, and store it if not

        @param bare_jid(unicode): bare jid to check
        @return (D): Deferred fired when jid is stored
        """
        if bare_jid in self.all_jids:
            return defer.succeed(None)
        else:
            self.all_jids.add(bare_jid)
            d = self.data.force(KEY_ALL_JIDS, self.all_jids)
            return d

    def loadOwnData(self, callback):
        callback(True, {'own_bare_jid': self.own_bare_jid_s,
                        'own_device_id': self.device_id})

    def storeOwnData(self, callback, own_bare_jid, own_device_id):
        if own_bare_jid != self.own_bare_jid_s or own_device_id != self.device_id:
            raise exceptions.InternalError('bare jid or device id inconsistency!')
        callback(True, None)

    def loadState(self, callback):
        d = self.data.get(KEY_STATE)
        self.setCb(d, callback)

    def storeState(self, callback, state):
        d = self.data.force(KEY_STATE, state)
        self.setCb(d, callback)

    def loadSession(self, callback, bare_jid, device_id):
        key = '\n'.join([KEY_SESSION, bare_jid, str(device_id)])
        d = self.data.get(key)
        self.setCb(d, callback)

    def storeSession(self, callback, bare_jid, device_id, session):
        key = '\n'.join([KEY_SESSION, bare_jid, str(device_id)])
        d = self.data.force(key, session)
        self.setCb(d, callback)

    def deleteSession(self, callback, bare_jid, device_id):
        key = '\n'.join([KEY_SESSION, bare_jid, str(device_id)])
        d = self.data.remove(key)
        self.setCb(d, callback)

    def loadActiveDevices(self, callback, bare_jid):
        key = '\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
        d = self.data.get(key, {})
        if callback is not None:
            self.setCb(d, callback)
        return d

    def loadInactiveDevices(self, callback, bare_jid):
        key = '\n'.join([KEY_INACTIVE_DEVICES, bare_jid])
        d = self.data.get(key, {})
        if callback is not None:
            self.setCb(d, callback)
        return d

    def storeActiveDevices(self, callback, bare_jid, devices):
        key = '\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
        d = self._checkJid(bare_jid)
        d.addCallback(lambda _: self.data.force(key, devices))
        self.setCb(d, callback)

    def storeInactiveDevices(self, callback, bare_jid, devices):
        key = '\n'.join([KEY_INACTIVE_DEVICES, bare_jid])
        d = self._checkJid(bare_jid)
        d.addCallback(lambda _: self.data.force(key, devices))
        self.setCb(d, callback)

    def storeTrust(self, callback, bare_jid, device_id, trust):
        key = '\n'.join([KEY_TRUST, bare_jid, str(device_id)])
        d = self.data.force(key, trust)
        self.setCb(d, callback)

    def loadTrust(self, callback, bare_jid, device_id):
        key = '\n'.join([KEY_TRUST, bare_jid, str(device_id)])
        d = self.data.get(key)
        if callback is not None:
            self.setCb(d, callback)
        return d

    def listJIDs(self, callback):
        d = defer.succeed(self.all_jids)
        if callback is not None:
            self.setCb(d, callback)
        return d

    def _deleteJID_logResults(self, results):
        failed = [success for success, __ in results if not success]
        if failed:
            log.warning(
                "delete JID failed for {failed_count} on {total_count} operations"
                .format(failed_count=len(failed), total_count=len(results)))
        else:
            log.info(
                "Delete JID operation succeed ({total_count} operations)."
                .format(total_count=len(results)))

    def _deleteJID_gotDevices(self, results, bare_jid):
        assert len(results) == 2
        active_success, active_devices = results[0]
        inactive_success, inactive_devices = results[0]
        d_list = []
        for success, devices in results:
            if not success:
                log.warning("Can't retrieve devices for {bare_jid}: {reason}"
                    .format(bare_jid=bare_jid, reason=active_devices))
            else:
                for device_id in devices:
                    for key in (KEY_SESSION, KEY_TRUST):
                        k = '\n'.join([key, bare_jid, str(device_id)])
                        d_list.append(self.data.remove(k))

        d_list.append(self.data.remove(KEY_ACTIVE_DEVICES, bare_jid))
        d_list.append(self.data.remove(KEY_INACTIVE_DEVICES, bare_jid))
        d_list.append(lambda __: self.all_jids.discard(bare_jid))
        # FIXME: there is a risk of race condition here,
        #        if self.all_jids is modified between discard and force)
        d_list.append(lambda __: self.data.force(KEY_ALL_JIDS, self.all_jids))
        d = defer.DeferredList(d_list)
        d.addCallback(self._deleteJID_logResults)
        return d

    def deleteJID(self, callback, bare_jid):
        """Retrieve all (in)actives of bare_jid, and delete all related keys"""
        d_list = []

        key = '\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
        d_list.append(self.data.get(key, []))

        key = '\n'.join([KEY_INACTIVE_DEVICES, bare_jid])
        d_inactive = self.data.get(key, {})
        # inactive devices are returned as a dict mapping from devices_id to timestamp
        # but we only need devices ids
        d_inactive.addCallback(lambda devices: [k for k, __ in devices])

        d_list.append(d_inactive)
        d = defer.DeferredList(d_list)
        d.addCallback(self._deleteJID_gotDevices, bare_jid)
        if callback is not None:
            self.setCb(d, callback)
        return d


class SatOTPKPolicy(omemo.DefaultOTPKPolicy):
    pass


class OmemoSession(object):
    """Wrapper to use omemo.OmemoSession with Deferred"""

    def __init__(self, session):
        self._session = session

    @property
    def republish_bundle(self):
        return self._session.republish_bundle

    @property
    def public_bundle(self):
        return self._session.public_bundle

    @classmethod
    def create(cls, client, storage, my_device_id = None):
        omemo_session_p = omemo.SessionManager.create(
            storage,
            SatOTPKPolicy,
            omemo_backend,
            client.jid.userhost(),
            my_device_id)
        d = promise2Deferred(omemo_session_p)
        d.addCallback(lambda session: cls(session))
        return d

    def newDeviceList(self, jid, devices):
        jid = jid.userhost()
        new_device_p = self._session.newDeviceList(jid, devices)
        return promise2Deferred(new_device_p)

    def getDevices(self, bare_jid=None):
        get_devices_p = self._session.getDevices(bare_jid=bare_jid)
        return promise2Deferred(get_devices_p)

    def buildSession(self, bare_jid, device, bundle):
        bare_jid = bare_jid.userhost()
        build_session_p = self._session.buildSession(bare_jid, device, bundle)
        return promise2Deferred(build_session_p)

    def encryptMessage(self, bare_jids, message, bundles=None, expect_problems=None):
        """Encrypt a message

        @param bare_jids(iterable[jid.JID]): destinees of the message
        @param message(unicode): message to encode
        @param bundles(dict[jid.JID, dict[int, ExtendedPublicBundle]):
            entities => devices => bundles map
        @return D(dict): encryption data
        """
        bare_jids = [e.userhost() for e in bare_jids]
        if bundles is not None:
            bundles = {e.userhost(): v for e, v in bundles.items()}
        encrypt_mess_p = self._session.encryptMessage(
            bare_jids=bare_jids,
            plaintext=message.encode(),
            bundles=bundles,
            expect_problems=expect_problems)
        return promise2Deferred(encrypt_mess_p)

    def decryptMessage(self, bare_jid, device, iv, message, is_pre_key_message,
                       ciphertext, additional_information=None, allow_untrusted=False):
        bare_jid = bare_jid.userhost()
        decrypt_mess_p = self._session.decryptMessage(
            bare_jid=bare_jid,
            device=device,
            iv=iv,
            message=message,
            is_pre_key_message=is_pre_key_message,
            ciphertext=ciphertext,
            additional_information=additional_information,
            allow_untrusted=allow_untrusted
            )
        return promise2Deferred(decrypt_mess_p)

    def setTrust(self, bare_jid, device, key, trusted):
        bare_jid = bare_jid.userhost()
        setTrust_p = self._session.setTrust(
            bare_jid=bare_jid,
            device=device,
            key=key,
            trusted=trusted,
        )
        return promise2Deferred(setTrust_p)

    def getTrustForJID(self, bare_jid):
        bare_jid = bare_jid.userhost()
        get_trust_p = self._session.getTrustForJID(bare_jid=bare_jid)
        return promise2Deferred(get_trust_p)


class OMEMO(object):

    def __init__(self, host):
        log.info(_("OMEMO plugin initialization (omemo module v{version})").format(
            version=omemo.__version__))
        version = tuple(map(int, omemo.__version__.split('.')[:3]))
        if version < OMEMO_MIN_VER:
            log.warning(_(
                "Your version of omemo module is too old: {v[0]}.{v[1]}.{v[2]} is "
                "minimum required, please update.").format(v=OMEMO_MIN_VER))
            raise exceptions.CancelError("module is too old")
        self.host = host
        self._p_hints = host.plugins["XEP-0334"]
        self._p_carbons = host.plugins["XEP-0280"]
        self._p = host.plugins["XEP-0060"]
        self._m = host.plugins.get("XEP-0045")
        self._sid = host.plugins.get("XEP-0359")
        host.trigger.add("messageReceived", self._messageReceivedTrigger, priority=100050)
        host.trigger.add("sendMessageData", self._sendMessageDataTrigger)
        self.host.registerEncryptionPlugin(self, "OMEMO", NS_OMEMO, 100)
        pep = host.plugins['XEP-0163']
        pep.addPEPEvent("OMEMO_DEVICES", NS_OMEMO_DEVICES, self.onNewDevices)

    @defer.inlineCallbacks
    def trustUICb(self, xmlui_data, trust_data, expect_problems=None,
                  profile=C.PROF_KEY_NONE):
        if C.bool(xmlui_data.get('cancelled', 'false')):
            defer.returnValue({})
        client = self.host.getClient(profile)
        session = client._xep_0384_session
        answer = xml_tools.XMLUIResult2DataFormResult(xmlui_data)
        for key, value in answer.items():
            if key.startswith('trust_'):
                trust_id = key[6:]
            else:
                continue
            data = trust_data[trust_id]
            trust = C.bool(value)
            yield session.setTrust(
                data["jid"],
                data["device"],
                data["ik"],
                trusted=trust,
            )
            if not trust and expect_problems is not None:
                expect_problems.setdefault(data['jid'].userhost(), set()).add(
                    data['device']
                )
        defer.returnValue({})

    @defer.inlineCallbacks
    def getTrustUI(self, client, entity_jid=None, trust_data=None, submit_id=None):
        """Generate a XMLUI to manage trust

        @param entity_jid(None, jid.JID): jid of entity to manage
            None to use trust_data
        @param trust_data(None, dict): devices data:
            None to use entity_jid
            else a dict mapping from trust ids (unicode) to devices data,
            where a device data must have the following keys:
                - jid(jid.JID): bare jid of the device owner
                - device(int): device id
                - ik(bytes): identity key
            and may have the following key:
                - trusted(bool): True if device is trusted
        @param submit_id(None, unicode): submit_id to use
            if None set UI callback to trustUICb
        @return D(xmlui): trust management form
        """
        # we need entity_jid xor trust_data
        assert entity_jid and not trust_data or not entity_jid and trust_data
        if entity_jid and entity_jid.resource:
            raise ValueError("A bare jid is expected")

        session = client._xep_0384_session

        if trust_data is None:
            cache = client._xep_0384_cache.setdefault(entity_jid, {})
            trust_data = {}
            if self._m is not None and self._m.isJoinedRoom(client, entity_jid):
                trust_jids = self.getJIDsForRoom(client, entity_jid)
            else:
                trust_jids = [entity_jid]
            for trust_jid in trust_jids:
                trust_session_data = yield session.getTrustForJID(trust_jid)
                bare_jid_s = trust_jid.userhost()
                for device_id, trust_info in trust_session_data['active'].items():
                    if trust_info is None:
                        # device has never been (un)trusted, we have to retrieve its
                        # fingerprint (i.e. identity key or "ik") through public bundle
                        if device_id not in cache:
                            bundles, missing = yield self.getBundles(client,
                                                                     trust_jid,
                                                                     [device_id])
                            if device_id not in bundles:
                                log.warning(_(
                                    "Can't find bundle for device {device_id} of user "
                                    "{bare_jid}, ignoring").format(device_id=device_id,
                                                                    bare_jid=bare_jid_s))
                                continue
                            cache[device_id] = bundles[device_id]
                        # TODO: replace False below by None when undecided
                        #       trusts are handled
                        trust_info = {
                            "key": cache[device_id].ik,
                            "trusted": False
                        }

                    ik = trust_info["key"]
                    trust_id = str(hash((bare_jid_s, device_id, ik)))
                    trust_data[trust_id] = {
                        "jid": trust_jid,
                        "device": device_id,
                        "ik": ik,
                        "trusted": trust_info["trusted"],
                        }

        if submit_id is None:
            submit_id = self.host.registerCallback(partial(self.trustUICb,
                                                           trust_data=trust_data),
                                                   with_data=True,
                                                   one_shot=True)
        xmlui = xml_tools.XMLUI(
            panel_type = C.XMLUI_FORM,
            title = D_("OMEMO trust management"),
            submit_id = submit_id
        )
        xmlui.addText(D_(
            "This is OMEMO trusting system. You'll see below the devices of your "
            "contacts, and a checkbox to trust them or not. A trusted device "
            "can read your messages in plain text, so be sure to only validate "
            "devices that you are sure are belonging to your contact. It's better "
            "to do this when you are next to your contact and her/his device, so "
            "you can check the \"fingerprint\" (the number next to the device) "
            "yourself. Do *not* validate a device if the fingerprint is wrong!"))

        xmlui.changeContainer("label")
        xmlui.addLabel(D_("This device ID"))
        xmlui.addText(str(client._xep_0384_device_id))
        xmlui.addLabel(D_("This device fingerprint"))
        ik_hex = session.public_bundle.ik.hex().upper()
        fp_human = ' '.join([ik_hex[i:i+8] for i in range(0, len(ik_hex), 8)])
        xmlui.addText(fp_human)
        xmlui.addEmpty()
        xmlui.addEmpty()


        for trust_id, data in trust_data.items():
            xmlui.addLabel(D_("Contact"))
            xmlui.addJid(data['jid'])
            xmlui.addLabel(D_("Device ID"))
            xmlui.addText(str(data['device']))
            xmlui.addLabel(D_("Fingerprint"))
            ik_hex = data['ik'].hex().upper()
            fp_human = ' '.join([ik_hex[i:i+8] for i in range(0, len(ik_hex), 8)])
            xmlui.addText(fp_human)
            xmlui.addLabel(D_("Trust this device?"))
            xmlui.addBool("trust_{}".format(trust_id),
                          value=C.boolConst(data.get('trusted', False)))

            xmlui.addEmpty()
            xmlui.addEmpty()

        defer.returnValue(xmlui)

    @defer.inlineCallbacks
    def profileConnected(self, client):
        if self._m is not None:
            # we keep plain text message for MUC messages we send
            # as we can't encrypt for our own device
            client._xep_0384_muc_cache = {}
            # and we keep them only for some time, in case something goes wrong
            # with the MUC
            client._xep_0384_muc_cache_timer = None

        # FIXME: is _xep_0384_ready needed? can we use profileConnecting?
        #        Workflow should be checked
        client._xep_0384_ready = defer.Deferred()
        # we first need to get devices ids (including our own)
        persistent_dict = persistent.LazyPersistentBinaryDict("XEP-0384", client.profile)
        # all known devices of profile
        devices = yield self.getDevices(client)
        # and our own device id
        device_id = yield persistent_dict.get(KEY_DEVICE_ID)
        if device_id is None:
            log.info(_("We have no identity for this device yet, let's generate one"))
            # we have a new device, we create device_id
            device_id = random.randint(1, 2**31-1)
            # we check that it's really unique
            while device_id in devices:
                device_id = random.randint(1, 2**31-1)
            # and we save it
            persistent_dict[KEY_DEVICE_ID] = device_id

        if device_id not in devices:
            devices.add(device_id)
            yield self.setDevices(client, devices)

        all_jids = yield persistent_dict.get(KEY_ALL_JIDS, set())

        omemo_storage = OmemoStorage(client, device_id, all_jids, persistent_dict)
        omemo_session = yield OmemoSession.create(client, omemo_storage, device_id)
        client._xep_0384_cache = {}
        client._xep_0384_session = omemo_session
        client._xep_0384_device_id = device_id
        yield omemo_session.newDeviceList(client.jid, devices)
        if omemo_session.republish_bundle:
            log.info(_("Saving public bundle for this device ({device_id})").format(
                device_id=device_id))
            yield self.setBundle(client, omemo_session.public_bundle, device_id)
        client._xep_0384_ready.callback(None)
        del client._xep_0384_ready

    ## XMPP PEP nodes manipulation

    # devices

    def parseDevices(self, items):
        """Parse devices found in items

        @param items(iterable[domish.Element]): items as retrieved by getItems
        @return set[int]: parsed devices
        """
        devices = set()
        if len(items) > 1:
            log.warning(_("OMEMO devices list is stored in more that one items, "
                          "this is not expected"))
        if items:
            try:
                list_elt = next(items[0].elements(NS_OMEMO, 'list'))
            except StopIteration:
                log.warning(_("no list element found in OMEMO devices list"))
                return
            for device_elt in list_elt.elements(NS_OMEMO, 'device'):
                try:
                    device_id = int(device_elt['id'])
                except KeyError:
                    log.warning(_('device element is missing "id" attribute: {elt}')
                                .format(elt=device_elt.toXml()))
                except ValueError:
                    log.warning(_('invalid device id: {device_id}').format(
                        device_id=device_elt['id']))
                else:
                    devices.add(device_id)
        return devices

    @defer.inlineCallbacks
    def getDevices(self, client, entity_jid=None):
        """Retrieve list of registered OMEMO devices

        @param entity_jid(jid.JID, None): get devices from this entity
            None to get our own devices
        @return (set(int)): list of devices
        """
        if entity_jid is not None:
            assert not entity_jid.resource
        try:
            items, metadata = yield self._p.getItems(client, entity_jid, NS_OMEMO_DEVICES)
        except exceptions.NotFound:
            log.info(_("there is no node to handle OMEMO devices"))
            defer.returnValue(set())

        devices = self.parseDevices(items)
        defer.returnValue(devices)

    def setDevicesEb(self, failure_):
        log.warning(_("Can't set devices: {reason}").format(reason=failure_))

    def setDevices(self, client, devices):
        list_elt = domish.Element((NS_OMEMO, 'list'))
        for device in devices:
            device_elt = list_elt.addElement('device')
            device_elt['id'] = str(device)
        d = self._p.sendItem(
            client, None, NS_OMEMO_DEVICES, list_elt, item_id=self._p.ID_SINGLETON)
        d.addErrback(self.setDevicesEb)
        return d

    # bundles

    @defer.inlineCallbacks
    def getBundles(self, client, entity_jid, devices_ids):
        """Retrieve public bundles of an entity devices

        @param entity_jid(jid.JID): bare jid of entity
        @param devices_id(iterable[int]): ids of the devices bundles to retrieve
        @return (tuple(dict[int, ExtendedPublicBundle], list(int))):
            - bundles collection:
                * key is device_id
                * value is parsed bundle
            - set of bundles not found
        """
        assert not entity_jid.resource
        bundles = {}
        missing = set()
        for device_id in devices_ids:
            node = NS_OMEMO_BUNDLE.format(device_id=device_id)
            try:
                items, metadata = yield self._p.getItems(client, entity_jid, node)
            except exceptions.NotFound:
                log.warning(_("Bundle missing for device {device_id}")
                    .format(device_id=device_id))
                missing.add(device_id)
                continue
            except error.StanzaError as e:
                log.warning(_("Can't get bundle for device {device_id}: {reason}")
                    .format(device_id=device_id, reason=e))
                continue
            if not items:
                log.warning(_("no item found in node {node}, can't get public bundle "
                              "for device {device_id}").format(node=node,
                                                                device_id=device_id))
                continue
            if len(items) > 1:
                log.warning(_("more than one item found in {node}, "
                              "this is not expected").format(node=node))
            item = items[0]
            try:
                bundle_elt = next(item.elements(NS_OMEMO, 'bundle'))
                signedPreKeyPublic_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'signedPreKeyPublic'))
                signedPreKeySignature_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'signedPreKeySignature'))
                identityKey_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'identityKey'))
                prekeys_elt =  next(bundle_elt.elements(
                    NS_OMEMO, 'prekeys'))
            except StopIteration:
                log.warning(_("invalid bundle for device {device_id}, ignoring").format(
                    device_id=device_id))
                continue

            try:
                spkPublic = base64.b64decode(str(signedPreKeyPublic_elt))
                spkSignature = base64.b64decode(
                    str(signedPreKeySignature_elt))

                ik = base64.b64decode(str(identityKey_elt))
                spk = {
                    "key": spkPublic,
                    "id": int(signedPreKeyPublic_elt['signedPreKeyId'])
                }
                otpks = []
                for preKeyPublic_elt in prekeys_elt.elements(NS_OMEMO, 'preKeyPublic'):
                    preKeyPublic = base64.b64decode(str(preKeyPublic_elt))
                    otpk = {
                        "key": preKeyPublic,
                        "id": int(preKeyPublic_elt['preKeyId'])
                    }
                    otpks.append(otpk)

            except Exception as e:
                log.warning(_("error while decoding key for device {device_id}: {msg}")
                            .format(device_id=device_id, msg=e))
                continue

            bundles[device_id] = ExtendedPublicBundle.parse(omemo_backend, ik, spk,
                                                            spkSignature, otpks)

        defer.returnValue((bundles, missing))

    def setBundleEb(self, failure_):
        log.warning(_("Can't set bundle: {reason}").format(reason=failure_))

    def setBundle(self, client, bundle, device_id):
        """Set public bundle for this device.

        @param bundle(ExtendedPublicBundle): bundle to publish
        """
        log.debug(_("updating bundle for {device_id}").format(device_id=device_id))
        bundle = bundle.serialize(omemo_backend)
        bundle_elt = domish.Element((NS_OMEMO, 'bundle'))
        signedPreKeyPublic_elt = bundle_elt.addElement(
            "signedPreKeyPublic",
            content=b64enc(bundle["spk"]['key']))
        signedPreKeyPublic_elt['signedPreKeyId'] = str(bundle["spk"]['id'])

        bundle_elt.addElement(
            "signedPreKeySignature",
            content=b64enc(bundle["spk_signature"]))

        bundle_elt.addElement(
            "identityKey",
            content=b64enc(bundle["ik"]))

        prekeys_elt = bundle_elt.addElement('prekeys')
        for otpk in bundle["otpks"]:
            preKeyPublic_elt = prekeys_elt.addElement(
                'preKeyPublic',
                content=b64enc(otpk["key"]))
            preKeyPublic_elt['preKeyId'] = str(otpk['id'])

        node = NS_OMEMO_BUNDLE.format(device_id=device_id)
        d = self._p.sendItem(client, None, node, bundle_elt, item_id=self._p.ID_SINGLETON)
        d.addErrback(self.setBundleEb)
        return d

    ## PEP node events callbacks

    @defer.inlineCallbacks
    def onNewDevices(self, itemsEvent, profile):
        client = self.host.getClient(profile)
        try:
            omemo_session = client._xep_0384_session
        except AttributeError:
            yield client._xep_0384_ready
            omemo_session = client._xep_0384_session
        entity = itemsEvent.sender

        devices = self.parseDevices(itemsEvent.items)
        omemo_session.newDeviceList(entity, devices)

        if entity == client.jid.userhostJID():
            own_device = client._xep_0384_device_id
            if own_device not in devices:
                log.warning(_("Our own device is missing from devices list, fixing it"))
                devices.add(own_device)
                yield self.setDevices(client, devices)

    ## triggers

    @defer.inlineCallbacks
    def handleProblems(self, client, feedback_jid, bundles, expect_problems, problems):
        """Try to solve problems found by EncryptMessage

        @param feedback_jid(jid.JID): bare jid where the feedback message must be sent
        @param bundles(dict): bundles data as used in EncryptMessage
            already filled with known bundles, missing bundles
            need to be added to it
            This dict is updated
        @param problems(list): exceptions raised by EncryptMessage
        @param expect_problems(dict): known problems to expect, used in encryptMessage
            This dict will list devices where problems can be ignored
            (those devices won't receive the encrypted data)
            This dict is updated
        """
        # FIXME: not all problems are handled yet
        undecided = {}
        missing_bundles = {}
        found_bundles = None
        cache = client._xep_0384_cache
        for problem in problems:
            if isinstance(problem, omemo_excpt.TrustException):
                if problem.problem == 'undecided':
                    undecided[str(hash(problem))] = problem
                elif problem.problem == 'untrusted':
                    expect_problems.setdefault(problem.bare_jid, set()).add(
                        problem.device)
                    log.info(_(
                        "discarding untrusted device {device_id} with key {device_key} "
                        "for {entity}").format(
                            device_id=problem.device,
                            device_key=problem.ik.hex().upper(),
                            entity=problem.bare_jid,
                        )
                    )
                else:
                    log.error(
                        f"Unexpected trust problem: {problem.problem!r} for device "
                        f"{problem.device} for {problem.bare_jid}, ignoring device")
                    expect_problems.setdefault(problem.bare_jid, set()).add(
                        problem.device)
            elif isinstance(problem, omemo_excpt.MissingBundleException):
                pb_entity = jid.JID(problem.bare_jid)
                entity_cache = cache.setdefault(pb_entity, {})
                entity_bundles = bundles.setdefault(pb_entity, {})
                if problem.device in entity_cache:
                    entity_bundles[problem.device] = entity_cache[problem.device]
                else:
                    found_bundles, missing = yield self.getBundles(
                        client, pb_entity, [problem.device])
                    entity_cache.update(bundles)
                    entity_bundles.update(found_bundles)
                    if problem.device in missing:
                        missing_bundles.setdefault(pb_entity, set()).add(
                            problem.device)
                        expect_problems.setdefault(problem.bare_jid, set()).add(
                            problem.device)
            elif isinstance(problem, omemo_excpt.NoEligibleDevicesException):
                if undecided or found_bundles:
                    # we may have new devices after this run, so let's continue for now
                    continue
                else:
                    raise problem
            else:
                raise problem

        for peer_jid, devices in missing_bundles.items():
            devices_s = [str(d) for d in devices]
            log.warning(
                _("Can't retrieve bundle for device(s) {devices} of entity {peer}, "
                  "the message will not be readable on this/those device(s)").format(
                    devices=", ".join(devices_s), peer=peer_jid.full()))
            client.feedback(
                feedback_jid,
                D_("You're destinee {peer} has missing encryption data on some of "
                   "his/her device(s) (bundle on device {devices}), the message won't  "
                   "be readable on this/those device.").format(
                   peer=peer_jid.full(), devices=", ".join(devices_s)))

        if undecided:
            trust_data = {}
            for trust_id, data in undecided.items():
                trust_data[trust_id] = {
                    'jid': jid.JID(data.bare_jid),
                    'device':  data.device,
                    'ik': data.ik}

            user_msg =  D_("Not all destination devices are trusted, we can't encrypt "
                           "message in such a situation. Please indicate if you trust "
                           "those devices or not in the trust manager before we can "
                           "send this message")
            client.feedback(feedback_jid, user_msg)
            xmlui = yield self.getTrustUI(client, trust_data=trust_data, submit_id="")

            answer = yield xml_tools.deferXMLUI(
                self.host,
                xmlui,
                action_extra={
                    "meta_encryption_trust": NS_OMEMO,
                },
                profile=client.profile)
            yield self.trustUICb(answer, trust_data, expect_problems, client.profile)

    @defer.inlineCallbacks
    def encryptMessage(self, client, entity_bare_jids, message, feedback_jid=None):
        if feedback_jid is None:
            if len(entity_bare_jids) != 1:
                log.error(
                    "feedback_jid must be provided when message is encrypted for more "
                    "than one entities")
                feedback_jid = entity_bare_jids[0]
        omemo_session = client._xep_0384_session
        expect_problems = {}
        bundles = {}
        loop_idx = 0
        try:
            while True:
                if loop_idx > 10:
                    msg = _("Too many iterations in encryption loop")
                    log.error(msg)
                    raise exceptions.InternalError(msg)
                # encryptMessage may fail, in case of e.g. trust issue or missing bundle
                try:
                    encrypted = yield omemo_session.encryptMessage(
                        entity_bare_jids,
                        message,
                        bundles,
                        expect_problems = expect_problems)
                except omemo_excpt.EncryptionProblemsException as e:
                    # we know the problem to solve, we can try to fix them
                    yield self.handleProblems(
                        client,
                        feedback_jid=feedback_jid,
                        bundles=bundles,
                        expect_problems=expect_problems,
                        problems=e.problems)
                    loop_idx += 1
                else:
                    break
        except Exception as e:
            msg = _("Can't encrypt message for {entities}: {reason}".format(
                entities=', '.join(e.full() for e in entity_bare_jids), reason=e))
            log.warning(msg)
            extra = {C.MESS_EXTRA_INFO: C.EXTRA_INFO_ENCR_ERR}
            client.feedback(feedback_jid, msg, extra)
            raise e

        defer.returnValue(encrypted)

    @defer.inlineCallbacks
    def _messageReceivedTrigger(self, client, message_elt, post_treat):
        try:
            encrypted_elt = next(message_elt.elements(NS_OMEMO, "encrypted"))
        except StopIteration:
            # no OMEMO message here
            defer.returnValue(True)

        # we have an encrypted message let's decrypt it

        from_jid = jid.JID(message_elt['from'])

        if message_elt.getAttribute("type") == C.MESS_TYPE_GROUPCHAT:
            # with group chat, we must get the real jid for decryption
            # and use the room as feedback_jid

            if self._m is None:
                # plugin XEP-0045 (MUC) is not available
                defer.returnValue(True)

            room_jid = from_jid.userhostJID()
            feedback_jid = room_jid
            if self._sid is not None:
                mess_id = self._sid.getOriginId(message_elt)
            else:
                mess_id = None

            if mess_id is None:
                mess_id = message_elt.getAttribute('id')
            cache_key = (room_jid, mess_id)

            try:
                room = self._m.getRoom(client, room_jid)
            except exceptions.NotFound:
                log.warning(
                    f"Received an OMEMO encrypted msg from a room {room_jid} which has "
                    f"not been joined, ignoring")
                defer.returnValue(True)

            user = room.getUser(from_jid.resource)
            if user is None:
                log.warning(f"Can't find user {user} in room {room_jid}, ignoring")
                defer.returnValue(True)
            if not user.entity:
                log.warning(
                    f"Real entity of user {user} in room {room_jid} can't be established,"
                    f" OMEMO encrypted message can't be decrypted")
                defer.returnValue(True)

            # now we have real jid of the entity, we use it instead of from_jid
            from_jid = user.entity.userhostJID()

        else:
            # we have a one2one message, we can user "from" and "to" normally

            if from_jid.userhostJID() == client.jid.userhostJID():
                feedback_jid = jid.JID(message_elt['to'])
            else:
                feedback_jid = from_jid


        if (message_elt.getAttribute("type") == C.MESS_TYPE_GROUPCHAT
            and mess_id is not None
            and cache_key in client._xep_0384_muc_cache):
            plaintext = client._xep_0384_muc_cache.pop(cache_key)
            if not client._xep_0384_muc_cache:
                client._xep_0384_muc_cache_timer.cancel()
                client._xep_0384_muc_cache_timer = None
        else:
            try:
                omemo_session = client._xep_0384_session
            except AttributeError:
                # on startup, message can ve received before session actually exists
                # so we need to synchronise here
                yield client._xep_0384_ready
                omemo_session = client._xep_0384_session

            device_id = client._xep_0384_device_id
            try:
                header_elt = next(encrypted_elt.elements(NS_OMEMO, 'header'))
                iv_elt = next(header_elt.elements(NS_OMEMO, 'iv'))
            except StopIteration:
                log.warning(_("Invalid OMEMO encrypted stanza, ignoring: {xml}")
                    .format(xml=message_elt.toXml()))
                defer.returnValue(False)
            try:
                s_device_id = header_elt['sid']
            except KeyError:
                log.warning(_("Invalid OMEMO encrypted stanza, missing sender device ID, "
                              "ignoring: {xml}")
                    .format(xml=message_elt.toXml()))
                defer.returnValue(False)
            try:
                key_elt = next((e for e in header_elt.elements(NS_OMEMO, 'key')
                                if int(e['rid']) == device_id))
            except StopIteration:
                log.warning(_("This OMEMO encrypted stanza has not been encrypted "
                              "for our device (device_id: {device_id}, fingerprint: "
                              "{fingerprint}): {xml}").format(
                              device_id=device_id,
                              fingerprint=omemo_session.public_bundle.ik.hex().upper(),
                              xml=encrypted_elt.toXml()))
                user_msg = (D_("An OMEMO message from {sender} has not been encrypted for "
                               "our device, we can't decrypt it").format(
                               sender=from_jid.full()))
                extra = {C.MESS_EXTRA_INFO: C.EXTRA_INFO_DECR_ERR}
                client.feedback(feedback_jid, user_msg, extra)
                defer.returnValue(False)
            except ValueError as e:
                log.warning(_("Invalid recipient ID: {msg}".format(msg=e)))
                defer.returnValue(False)
            is_pre_key = C.bool(key_elt.getAttribute('prekey', 'false'))
            payload_elt = next(encrypted_elt.elements(NS_OMEMO, 'payload'), None)
            additional_information = {
                "from_storage": bool(message_elt.delay)
            }

            kwargs = {
                "bare_jid": from_jid.userhostJID(),
                "device": s_device_id,
                "iv": base64.b64decode(bytes(iv_elt)),
                "message": base64.b64decode(bytes(key_elt)),
                "is_pre_key_message": is_pre_key,
                "ciphertext": base64.b64decode(bytes(payload_elt))
                    if payload_elt is not None else None,
                "additional_information":  additional_information,
            }

            try:
                try:
                    plaintext = yield omemo_session.decryptMessage(**kwargs)
                except omemo_excpt.TrustException:
                    post_treat.addCallback(client.encryption.markAsUntrusted)
                    kwargs['allow_untrusted'] = True
                    plaintext = yield omemo_session.decryptMessage(**kwargs)
                else:
                    post_treat.addCallback(client.encryption.markAsTrusted)
                plaintext = plaintext.decode()
            except Exception as e:
                log.warning(_("Can't decrypt message: {reason}\n{xml}").format(
                    reason=e, xml=message_elt.toXml()))
                user_msg = (D_(
                    "An OMEMO message from {sender} can't be decrypted: {reason}")
                    .format(sender=from_jid.full(), reason=e))
                extra = {C.MESS_EXTRA_INFO: C.EXTRA_INFO_DECR_ERR}
                client.feedback(feedback_jid, user_msg, extra)
                defer.returnValue(False)
            finally:
                if omemo_session.republish_bundle:
                    # we don't wait for the Deferred (i.e. no yield) on purpose
                    # there is no need to block the whole message workflow while
                    # updating the bundle
                    self.setBundle(client, omemo_session.public_bundle, device_id)

        message_elt.children.remove(encrypted_elt)
        if plaintext:
            message_elt.addElement("body", content=plaintext)
        post_treat.addCallback(client.encryption.markAsEncrypted)
        defer.returnValue(True)

    def getJIDsForRoom(self, client, room_jid):
        if self._m is None:
            exceptions.InternalError("XEP-0045 plugin missing, can't encrypt for group chat")
        room = self._m.getRoom(client, room_jid)
        return [u.entity.userhostJID() for u in room.roster.values()]

    def _expireMUCCache(self, client):
        client._xep_0384_muc_cache_timer = None
        for (room_jid, uid), msg in client._xep_0384_muc_cache.items():
            client.feedback(
                room_jid,
                D_("Our message with UID {uid} has not been received in time, it has "
                   "probably been lost. The message was: {msg!r}").format(
                    uid=uid, msg=str(msg)))

        client._xep_0384_muc_cache.clear()
        log.warning("Cache for OMEMO MUC has expired")

    @defer.inlineCallbacks
    def _sendMessageDataTrigger(self, client, mess_data):
        encryption = mess_data.get(C.MESS_KEY_ENCRYPTION)
        if encryption is None or encryption['plugin'].namespace != NS_OMEMO:
            return
        message_elt = mess_data["xml"]
        if mess_data['type'] == C.MESS_TYPE_GROUPCHAT:
            feedback_jid = room_jid = mess_data['to']
            to_jids = self.getJIDsForRoom(client, room_jid)
        else:
            feedback_jid = to_jid = mess_data["to"].userhostJID()
            to_jids = [to_jid]
        log.debug("encrypting message")
        body = None
        for child in list(message_elt.children):
            if child.name == "body":
                # we remove all unencrypted body,
                # and will only encrypt the first one
                if body is None:
                    body = child
                message_elt.children.remove(child)
            elif child.name == "html":
                # we don't want any XHTML-IM element
                message_elt.children.remove(child)

        if body is None:
            log.warning("No message found")
            return

        body = str(body)

        if mess_data['type'] == C.MESS_TYPE_GROUPCHAT:
            key = (room_jid, mess_data['uid'])
            # XXX: we can't encrypt message for our own device for security reason
            #      so we keep the plain text version in cache until we receive the
            #      message. We don't send it directly to bridge to keep a workflow
            #      similar to plain text MUC, so when we see it in frontend we know
            #      that it has been sent correctly.
            client._xep_0384_muc_cache[key] = body
            timer = client._xep_0384_muc_cache_timer
            if timer is None:
                client._xep_0384_muc_cache_timer = reactor.callLater(
                    MUC_CACHE_TTL, self._expireMUCCache, client)
            else:
                timer.reset(MUC_CACHE_TTL)
            # we use origin-id when possible, to identifiy the message in a stable way
            if self._sid is not None:
                self._sid.addOriginId(message_elt, mess_data['uid'])

        encryption_data = yield self.encryptMessage(
            client, to_jids, body, feedback_jid=feedback_jid)

        encrypted_elt = message_elt.addElement((NS_OMEMO, 'encrypted'))
        header_elt = encrypted_elt.addElement('header')
        header_elt['sid'] = str(encryption_data['sid'])

        for to_jid in to_jids:
            bare_jid_s = to_jid.userhost()

            for rid, data in encryption_data['keys'][bare_jid_s].items():
                key_elt = header_elt.addElement(
                    'key',
                    content=b64enc(data['data']))
                key_elt['rid'] = str(rid)
                if data['pre_key']:
                    key_elt['prekey'] = 'true'

        header_elt.addElement(
            'iv',
            content=b64enc(encryption_data['iv']))
        try:
            encrypted_elt.addElement(
                'payload',
                content=b64enc(encryption_data['payload']))
        except KeyError:
            pass