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During the migration the automated script to update the copyright headers accidentally got rid of some of the existing copyright lines. Reinstate them.
325 lines
12 KiB
Python
325 lines
12 KiB
Python
#
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# This file is licensed under the Affero General Public License (AGPL) version 3.
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#
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# Copyright 2020 The Matrix.org Foundation C.I.C.
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# Copyright 2015, 2016 OpenMarket Ltd
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# Copyright (C) 2023 New Vector, Ltd
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as
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# published by the Free Software Foundation, either version 3 of the
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# License, or (at your option) any later version.
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#
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# See the GNU Affero General Public License for more details:
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# <https://www.gnu.org/licenses/agpl-3.0.html>.
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#
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# Originally licensed under the Apache License, Version 2.0:
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# <http://www.apache.org/licenses/LICENSE-2.0>.
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#
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# [This file includes modifications made by New Vector Limited]
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#
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#
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import logging
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from typing import TYPE_CHECKING, Awaitable, Callable, Optional
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from synapse.api.constants import MAX_DEPTH, EventContentFields, EventTypes, Membership
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from synapse.api.errors import Codes, SynapseError
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from synapse.api.room_versions import EventFormatVersions, RoomVersion
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from synapse.crypto.event_signing import check_event_content_hash
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from synapse.crypto.keyring import Keyring
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from synapse.events import EventBase, make_event_from_dict
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from synapse.events.utils import prune_event, validate_canonicaljson
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from synapse.http.servlet import assert_params_in_dict
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from synapse.logging.opentracing import log_kv, trace
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from synapse.types import JsonDict, get_domain_from_id
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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class InvalidEventSignatureError(RuntimeError):
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"""Raised when the signature on an event is invalid.
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The stringification of this exception is just the error message without reference
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to the event id. The event id is available as a property.
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"""
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def __init__(self, message: str, event_id: str):
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super().__init__(message)
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self.event_id = event_id
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class FederationBase:
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def __init__(self, hs: "HomeServer"):
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self.hs = hs
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self._is_mine_server_name = hs.is_mine_server_name
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self.keyring = hs.get_keyring()
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self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
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self.store = hs.get_datastores().main
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self._clock = hs.get_clock()
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self._storage_controllers = hs.get_storage_controllers()
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@trace
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async def _check_sigs_and_hash(
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self,
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room_version: RoomVersion,
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pdu: EventBase,
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record_failure_callback: Optional[
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Callable[[EventBase, str], Awaitable[None]]
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] = None,
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) -> EventBase:
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"""Checks that event is correctly signed by the sending server.
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Also checks the content hash, and redacts the event if there is a mismatch.
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Also runs the event through the spam checker; if it fails, redacts the event
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and flags it as soft-failed.
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Args:
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room_version: The room version of the PDU
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pdu: the event to be checked
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record_failure_callback: A callback to run whenever the given event
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fails signature or hash checks. This includes exceptions
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that would be normally be thrown/raised but also things like
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checking for event tampering where we just return the redacted
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event.
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Returns:
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* the original event if the checks pass
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* a redacted version of the event (if the signature
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matched but the hash did not). In this case a warning will be logged.
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Raises:
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InvalidEventSignatureError if the signature check failed. Nothing
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will be logged in this case.
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"""
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try:
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await _check_sigs_on_pdu(self.keyring, room_version, pdu)
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except InvalidEventSignatureError as exc:
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if record_failure_callback:
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await record_failure_callback(pdu, str(exc))
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raise exc
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if not check_event_content_hash(pdu):
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# let's try to distinguish between failures because the event was
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# redacted (which are somewhat expected) vs actual ball-tampering
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# incidents.
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#
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# This is just a heuristic, so we just assume that if the keys are
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# about the same between the redacted and received events, then the
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# received event was probably a redacted copy (but we then use our
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# *actual* redacted copy to be on the safe side.)
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redacted_event = prune_event(pdu)
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if set(redacted_event.keys()) == set(pdu.keys()) and set(
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redacted_event.content.keys()
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) == set(pdu.content.keys()):
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logger.debug(
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"Event %s seems to have been redacted; using our redacted copy",
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pdu.event_id,
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)
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log_kv(
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{
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"message": "Event seems to have been redacted; using our redacted copy",
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"event_id": pdu.event_id,
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}
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)
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else:
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logger.warning(
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"Event %s content has been tampered, redacting",
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pdu.event_id,
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)
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log_kv(
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{
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"message": "Event content has been tampered, redacting",
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"event_id": pdu.event_id,
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}
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)
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if record_failure_callback:
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await record_failure_callback(
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pdu, "Event content has been tampered with"
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)
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return redacted_event
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spam_check = await self._spam_checker_module_callbacks.check_event_for_spam(pdu)
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if spam_check != self._spam_checker_module_callbacks.NOT_SPAM:
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logger.warning("Event contains spam, soft-failing %s", pdu.event_id)
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log_kv(
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{
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"message": "Event contains spam, redacting (to save disk space) "
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"as well as soft-failing (to stop using the event in prev_events)",
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"event_id": pdu.event_id,
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}
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)
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# we redact (to save disk space) as well as soft-failing (to stop
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# using the event in prev_events).
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redacted_event = prune_event(pdu)
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redacted_event.internal_metadata.soft_failed = True
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return redacted_event
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return pdu
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@trace
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async def _check_sigs_on_pdu(
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keyring: Keyring, room_version: RoomVersion, pdu: EventBase
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) -> None:
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"""Check that the given events are correctly signed
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Args:
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keyring: keyring object to do the checks
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room_version: the room version of the PDUs
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pdus: the events to be checked
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Raises:
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InvalidEventSignatureError if the event wasn't correctly signed.
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"""
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# we want to check that the event is signed by:
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#
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# (a) the sender's server
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#
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# - except in the case of invites created from a 3pid invite, which are exempt
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# from this check, because the sender has to match that of the original 3pid
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# invite, but the event may come from a different HS, for reasons that I don't
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# entirely grok (why do the senders have to match? and if they do, why doesn't the
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# joining server ask the inviting server to do the switcheroo with
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# exchange_third_party_invite?).
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#
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# That's pretty awful, since redacting such an invite will render it invalid
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# (because it will then look like a regular invite without a valid signature),
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# and signatures are *supposed* to be valid whether or not an event has been
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# redacted. But this isn't the worst of the ways that 3pid invites are broken.
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#
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# (b) for V1 and V2 rooms, the server which created the event_id
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#
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# let's start by getting the domain for each pdu, and flattening the event back
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# to JSON.
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# First we check that the sender event is signed by the sender's domain
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# (except if its a 3pid invite, in which case it may be sent by any server)
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sender_domain = get_domain_from_id(pdu.sender)
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if not _is_invite_via_3pid(pdu):
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try:
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await keyring.verify_event_for_server(
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sender_domain,
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pdu,
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pdu.origin_server_ts if room_version.enforce_key_validity else 0,
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)
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except Exception as e:
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raise InvalidEventSignatureError(
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f"unable to verify signature for sender domain {sender_domain}: {e}",
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pdu.event_id,
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) from None
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# now let's look for events where the sender's domain is different to the
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# event id's domain (normally only the case for joins/leaves), and add additional
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# checks. Only do this if the room version has a concept of event ID domain
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# (ie, the room version uses old-style non-hash event IDs).
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if room_version.event_format == EventFormatVersions.ROOM_V1_V2:
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event_domain = get_domain_from_id(pdu.event_id)
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if event_domain != sender_domain:
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try:
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await keyring.verify_event_for_server(
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event_domain,
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pdu,
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pdu.origin_server_ts if room_version.enforce_key_validity else 0,
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)
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except Exception as e:
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raise InvalidEventSignatureError(
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f"unable to verify signature for event domain {event_domain}: {e}",
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pdu.event_id,
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) from None
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# If this is a join event for a restricted room it may have been authorised
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# via a different server from the sending server. Check those signatures.
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if (
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room_version.restricted_join_rule
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and pdu.type == EventTypes.Member
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and pdu.membership == Membership.JOIN
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and EventContentFields.AUTHORISING_USER in pdu.content
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):
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authorising_server = get_domain_from_id(
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pdu.content[EventContentFields.AUTHORISING_USER]
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)
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try:
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await keyring.verify_event_for_server(
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authorising_server,
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pdu,
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pdu.origin_server_ts if room_version.enforce_key_validity else 0,
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)
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except Exception as e:
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raise InvalidEventSignatureError(
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f"unable to verify signature for authorising serve {authorising_server}: {e}",
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pdu.event_id,
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) from None
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def _is_invite_via_3pid(event: EventBase) -> bool:
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return (
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event.type == EventTypes.Member
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and event.membership == Membership.INVITE
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and "third_party_invite" in event.content
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)
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def event_from_pdu_json(pdu_json: JsonDict, room_version: RoomVersion) -> EventBase:
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"""Construct an EventBase from an event json received over federation
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Args:
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pdu_json: pdu as received over federation
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room_version: The version of the room this event belongs to
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Raises:
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SynapseError: if the pdu is missing required fields or is otherwise
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not a valid matrix event
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"""
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# we could probably enforce a bunch of other fields here (room_id, sender,
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# origin, etc etc)
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assert_params_in_dict(pdu_json, ("type", "depth"))
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# Strip any unauthorized values from "unsigned" if they exist
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if "unsigned" in pdu_json:
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_strip_unsigned_values(pdu_json)
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depth = pdu_json["depth"]
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if type(depth) is not int: # noqa: E721
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raise SynapseError(400, "Depth %r not an intger" % (depth,), Codes.BAD_JSON)
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if depth < 0:
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raise SynapseError(400, "Depth too small", Codes.BAD_JSON)
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elif depth > MAX_DEPTH:
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raise SynapseError(400, "Depth too large", Codes.BAD_JSON)
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# Validate that the JSON conforms to the specification.
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if room_version.strict_canonicaljson:
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validate_canonicaljson(pdu_json)
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event = make_event_from_dict(pdu_json, room_version)
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return event
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def _strip_unsigned_values(pdu_dict: JsonDict) -> None:
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"""
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Strip any unsigned values unless specifically allowed, as defined by the whitelist.
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pdu: the json dict to strip values from. Note that the dict is mutated by this
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function
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"""
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unsigned = pdu_dict["unsigned"]
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if not isinstance(unsigned, dict):
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pdu_dict["unsigned"] = {}
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if pdu_dict["type"] == "m.room.member":
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whitelist = ["knock_room_state", "invite_room_state", "age"]
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else:
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whitelist = ["age"]
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filtered_unsigned = {k: v for k, v in unsigned.items() if k in whitelist}
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pdu_dict["unsigned"] = filtered_unsigned
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