libervia-backend/libervia/backend/plugins/plugin_xep_0477.py

#!/usr/bin/env python3

# Libervia plugin for Pubsub Targeted Encryption
# Copyright (C) 2009-2022 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 typing import Any, Dict, List, Optional

from twisted.internet import defer
from twisted.words.protocols.jabber import jid, xmlstream
from twisted.words.xish import domish
from wokkel import disco, iwokkel
from wokkel import rsm
from zope.interface import implementer

from libervia.backend.core import exceptions
from libervia.backend.core.constants import Const as C
from libervia.backend.core.core_types import SatXMPPEntity
from libervia.backend.core.i18n import _
from libervia.backend.core.log import getLogger


log = getLogger(__name__)

IMPORT_NAME = "XEP-0477"

PLUGIN_INFO = {
    C.PI_NAME: "Pubsub Targeted Encryption",
    C.PI_IMPORT_NAME: IMPORT_NAME,
    C.PI_TYPE: C.PLUG_TYPE_XEP,
    C.PI_MODES: C.PLUG_MODE_BOTH,
    C.PI_PROTOCOLS: [],
    C.PI_DEPENDENCIES: ["XEP-0060", "XEP-0384"],
    C.PI_MAIN: "XEP_0477",
    C.PI_HANDLER: "yes",
    C.PI_DESCRIPTION: _("""Encrypt some items to specific entities"""),
}
NS_PTE = "urn:xmpp:pte:0"


class XEP_0477:
    namespace = NS_PTE

    def __init__(self, host):
        log.info(_("Pubsub Targeted Encryption plugin initialization"))
        host.register_namespace("pte", NS_PTE)
        self.host = host
        self._o = host.plugins["XEP-0384"]
        host.trigger.add("XEP-0060_publish", self._publish_trigger)
        host.trigger.add("XEP-0060_items", self._items_trigger)

    def get_handler(self, client):
        return XEP_0477_Handler()

    async def _publish_trigger(
        self,
        client: SatXMPPEntity,
        service: jid.JID,
        node: str,
        items: Optional[List[domish.Element]],
        options: Optional[dict],
        sender: jid.JID,
        extra: Dict[str, Any],
    ) -> bool:
        if not items or extra.get("encrypted_for") is None:
            return True
        encrypt_data = extra["encrypted_for"]
        try:
            targets = {jid.JID(t) for t in encrypt_data["targets"]}
        except (KeyError, RuntimeError):
            raise exceptions.DataError(f"Invalid encryption data: {encrypt_data}")
        for item in items:
            log.debug(
                f"encrypting item {item.getAttribute('id', '')} for "
                f"{', '.join(t.full() for t in targets)}"
            )
            encryption_type = encrypt_data.get("type", self._o.NS_TWOMEMO)
            if encryption_type != self._o.NS_TWOMEMO:
                raise NotImplementedError("only TWOMEMO is supported for now")
            await self._o.encrypt(
                client,
                self._o.NS_TWOMEMO,
                item,
                targets,
                is_muc_message=False,
                stanza_id=None,
            )
            item_elts = list(item.elements())
            if len(item_elts) != 1:
                raise ValueError(
                    f"there should be exactly one item payload: {item.toXml()}"
                )
            encrypted_payload = item_elts[0]
            item.children.clear()
            encrypted_elt = item.addElement((NS_PTE, "encrypted"))
            encrypted_elt["by"] = sender.userhost()
            encrypted_elt["type"] = encryption_type
            encrypted_elt.addChild(encrypted_payload)

        return True

    async def _items_trigger(
        self,
        client: SatXMPPEntity,
        service: Optional[jid.JID],
        node: str,
        items: List[domish.Element],
        rsm_response: rsm.RSMResponse,
        extra: Dict[str, Any],
    ) -> bool:
        if not extra.get(C.KEY_DECRYPT, True):
            return True
        if service is None:
            service = client.jid.userhostJID()
        for item in items:
            payload = item.firstChildElement()
            if (
                payload is not None
                and payload.name == "encrypted"
                and payload.uri == NS_PTE
            ):
                encrypted_elt = payload
                item.children.clear()
                try:
                    encryption_type = encrypted_elt.getAttribute("type")
                    encrypted_by = jid.JID(encrypted_elt["by"])
                except (KeyError, RuntimeError):
                    raise exceptions.DataError(
                        f"invalid <encrypted> element: {encrypted_elt.toXml()}"
                    )
                if encryption_type != self._o.NS_TWOMEMO:
                    raise NotImplementedError("only TWOMEMO is supported for now")
                log.debug(f"decrypting item {item.getAttribute('id', '')}")

                # FIXME: we do use _message_received_trigger now to decrypt the stanza, a
                #   cleaner separated decrypt method should be used
                encrypted_elt["from"] = encrypted_by.full()
                if (
                    not await self._o._message_received_trigger(
                        client, encrypted_elt, defer.Deferred()
                    )
                    or not encrypted_elt.children
                ):
                    raise exceptions.EncryptionError("can't decrypt the message")

                item.addChild(encrypted_elt.firstChildElement())

                extra.setdefault("encrypted", {})[item["id"]] = {
                    "type": NS_PTE,
                    "algorithm": encryption_type,
                }
        return True


@implementer(iwokkel.IDisco)
class XEP_0477_Handler(xmlstream.XMPPHandler):

    def getDiscoInfo(self, requestor, service, nodeIdentifier=""):
        return [disco.DiscoFeature(NS_PTE)]

    def getDiscoItems(self, requestor, service, nodeIdentifier=""):
        return []