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- # -*- coding: utf-8 -*-
- # Copyright 2015, 2016 OpenMarket Ltd
- #
- # Licensed under the Apache License, Version 2.0 (the "License");
- # you may not use this file except in compliance with the License.
- # You may obtain a copy of the License at
- #
- # http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- # See the License for the specific language governing permissions and
- # limitations under the License.
- import logging
- from collections import namedtuple
- import six
- from twisted.internet import defer
- from twisted.internet.defer import DeferredList
- from synapse.api.constants import MAX_DEPTH, EventTypes, Membership
- from synapse.api.errors import Codes, SynapseError
- from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, EventFormatVersions
- from synapse.crypto.event_signing import check_event_content_hash
- from synapse.events import event_type_from_format_version
- from synapse.events.utils import prune_event
- from synapse.http.servlet import assert_params_in_dict
- from synapse.logging.context import (
- LoggingContext,
- PreserveLoggingContext,
- make_deferred_yieldable,
- preserve_fn,
- )
- from synapse.types import get_domain_from_id
- from synapse.util import unwrapFirstError
- logger = logging.getLogger(__name__)
- class FederationBase(object):
- def __init__(self, hs):
- self.hs = hs
- self.server_name = hs.hostname
- self.keyring = hs.get_keyring()
- self.spam_checker = hs.get_spam_checker()
- self.store = hs.get_datastore()
- self._clock = hs.get_clock()
- @defer.inlineCallbacks
- def _check_sigs_and_hash_and_fetch(
- self, origin, pdus, room_version, outlier=False, include_none=False
- ):
- """Takes a list of PDUs and checks the signatures and hashs of each
- one. If a PDU fails its signature check then we check if we have it in
- the database and if not then request if from the originating server of
- that PDU.
- If a PDU fails its content hash check then it is redacted.
- The given list of PDUs are not modified, instead the function returns
- a new list.
- Args:
- origin (str)
- pdu (list)
- room_version (str)
- outlier (bool): Whether the events are outliers or not
- include_none (str): Whether to include None in the returned list
- for events that have failed their checks
- Returns:
- Deferred : A list of PDUs that have valid signatures and hashes.
- """
- deferreds = self._check_sigs_and_hashes(room_version, pdus)
- @defer.inlineCallbacks
- def handle_check_result(pdu, deferred):
- try:
- res = yield make_deferred_yieldable(deferred)
- except SynapseError:
- res = None
- if not res:
- # Check local db.
- res = yield self.store.get_event(
- pdu.event_id, allow_rejected=True, allow_none=True
- )
- if not res and pdu.origin != origin:
- try:
- res = yield self.get_pdu(
- destinations=[pdu.origin],
- event_id=pdu.event_id,
- room_version=room_version,
- outlier=outlier,
- timeout=10000,
- )
- except SynapseError:
- pass
- if not res:
- logger.warn(
- "Failed to find copy of %s with valid signature", pdu.event_id
- )
- return res
- handle = preserve_fn(handle_check_result)
- deferreds2 = [handle(pdu, deferred) for pdu, deferred in zip(pdus, deferreds)]
- valid_pdus = yield make_deferred_yieldable(
- defer.gatherResults(deferreds2, consumeErrors=True)
- ).addErrback(unwrapFirstError)
- if include_none:
- return valid_pdus
- else:
- return [p for p in valid_pdus if p]
- def _check_sigs_and_hash(self, room_version, pdu):
- return make_deferred_yieldable(
- self._check_sigs_and_hashes(room_version, [pdu])[0]
- )
- def _check_sigs_and_hashes(self, room_version, pdus):
- """Checks that each of the received events is correctly signed by the
- sending server.
- Args:
- room_version (str): The room version of the PDUs
- pdus (list[FrozenEvent]): the events to be checked
- Returns:
- list[Deferred]: for each input event, a deferred which:
- * returns the original event if the checks pass
- * returns a redacted version of the event (if the signature
- matched but the hash did not)
- * throws a SynapseError if the signature check failed.
- The deferreds run their callbacks in the sentinel
- """
- deferreds = _check_sigs_on_pdus(self.keyring, room_version, pdus)
- ctx = LoggingContext.current_context()
- def callback(_, pdu):
- with PreserveLoggingContext(ctx):
- if not check_event_content_hash(pdu):
- # let's try to distinguish between failures because the event was
- # redacted (which are somewhat expected) vs actual ball-tampering
- # incidents.
- #
- # This is just a heuristic, so we just assume that if the keys are
- # about the same between the redacted and received events, then the
- # received event was probably a redacted copy (but we then use our
- # *actual* redacted copy to be on the safe side.)
- redacted_event = prune_event(pdu)
- if set(redacted_event.keys()) == set(pdu.keys()) and set(
- six.iterkeys(redacted_event.content)
- ) == set(six.iterkeys(pdu.content)):
- logger.info(
- "Event %s seems to have been redacted; using our redacted "
- "copy",
- pdu.event_id,
- )
- else:
- logger.warning(
- "Event %s content has been tampered, redacting",
- pdu.event_id,
- )
- return redacted_event
- if self.spam_checker.check_event_for_spam(pdu):
- logger.warn(
- "Event contains spam, redacting %s: %s",
- pdu.event_id,
- pdu.get_pdu_json(),
- )
- return prune_event(pdu)
- return pdu
- def errback(failure, pdu):
- failure.trap(SynapseError)
- with PreserveLoggingContext(ctx):
- logger.warn(
- "Signature check failed for %s: %s",
- pdu.event_id,
- failure.getErrorMessage(),
- )
- return failure
- for deferred, pdu in zip(deferreds, pdus):
- deferred.addCallbacks(
- callback, errback, callbackArgs=[pdu], errbackArgs=[pdu]
- )
- return deferreds
- class PduToCheckSig(
- namedtuple(
- "PduToCheckSig", ["pdu", "redacted_pdu_json", "sender_domain", "deferreds"]
- )
- ):
- pass
- def _check_sigs_on_pdus(keyring, room_version, pdus):
- """Check that the given events are correctly signed
- Args:
- keyring (synapse.crypto.Keyring): keyring object to do the checks
- room_version (str): the room version of the PDUs
- pdus (Collection[EventBase]): the events to be checked
- Returns:
- List[Deferred]: a Deferred for each event in pdus, which will either succeed if
- the signatures are valid, or fail (with a SynapseError) if not.
- """
- # we want to check that the event is signed by:
- #
- # (a) the sender's server
- #
- # - except in the case of invites created from a 3pid invite, which are exempt
- # from this check, because the sender has to match that of the original 3pid
- # invite, but the event may come from a different HS, for reasons that I don't
- # entirely grok (why do the senders have to match? and if they do, why doesn't the
- # joining server ask the inviting server to do the switcheroo with
- # exchange_third_party_invite?).
- #
- # That's pretty awful, since redacting such an invite will render it invalid
- # (because it will then look like a regular invite without a valid signature),
- # and signatures are *supposed* to be valid whether or not an event has been
- # redacted. But this isn't the worst of the ways that 3pid invites are broken.
- #
- # (b) for V1 and V2 rooms, the server which created the event_id
- #
- # let's start by getting the domain for each pdu, and flattening the event back
- # to JSON.
- pdus_to_check = [
- PduToCheckSig(
- pdu=p,
- redacted_pdu_json=prune_event(p).get_pdu_json(),
- sender_domain=get_domain_from_id(p.sender),
- deferreds=[],
- )
- for p in pdus
- ]
- v = KNOWN_ROOM_VERSIONS.get(room_version)
- if not v:
- raise RuntimeError("Unrecognized room version %s" % (room_version,))
- # First we check that the sender event is signed by the sender's domain
- # (except if its a 3pid invite, in which case it may be sent by any server)
- pdus_to_check_sender = [p for p in pdus_to_check if not _is_invite_via_3pid(p.pdu)]
- more_deferreds = keyring.verify_json_objects_for_server(
- [
- (
- p.sender_domain,
- p.redacted_pdu_json,
- p.pdu.origin_server_ts if v.enforce_key_validity else 0,
- p.pdu.event_id,
- )
- for p in pdus_to_check_sender
- ]
- )
- def sender_err(e, pdu_to_check):
- errmsg = "event id %s: unable to verify signature for sender %s: %s" % (
- pdu_to_check.pdu.event_id,
- pdu_to_check.sender_domain,
- e.getErrorMessage(),
- )
- # XX not really sure if these are the right codes, but they are what
- # we've done for ages
- raise SynapseError(400, errmsg, Codes.UNAUTHORIZED)
- for p, d in zip(pdus_to_check_sender, more_deferreds):
- d.addErrback(sender_err, p)
- p.deferreds.append(d)
- # now let's look for events where the sender's domain is different to the
- # event id's domain (normally only the case for joins/leaves), and add additional
- # checks. Only do this if the room version has a concept of event ID domain
- # (ie, the room version uses old-style non-hash event IDs).
- if v.event_format == EventFormatVersions.V1:
- pdus_to_check_event_id = [
- p
- for p in pdus_to_check
- if p.sender_domain != get_domain_from_id(p.pdu.event_id)
- ]
- more_deferreds = keyring.verify_json_objects_for_server(
- [
- (
- get_domain_from_id(p.pdu.event_id),
- p.redacted_pdu_json,
- p.pdu.origin_server_ts if v.enforce_key_validity else 0,
- p.pdu.event_id,
- )
- for p in pdus_to_check_event_id
- ]
- )
- def event_err(e, pdu_to_check):
- errmsg = (
- "event id %s: unable to verify signature for event id domain: %s"
- % (pdu_to_check.pdu.event_id, e.getErrorMessage())
- )
- # XX as above: not really sure if these are the right codes
- raise SynapseError(400, errmsg, Codes.UNAUTHORIZED)
- for p, d in zip(pdus_to_check_event_id, more_deferreds):
- d.addErrback(event_err, p)
- p.deferreds.append(d)
- # replace lists of deferreds with single Deferreds
- return [_flatten_deferred_list(p.deferreds) for p in pdus_to_check]
- def _flatten_deferred_list(deferreds):
- """Given a list of deferreds, either return the single deferred,
- combine into a DeferredList, or return an already resolved deferred.
- """
- if len(deferreds) > 1:
- return DeferredList(deferreds, fireOnOneErrback=True, consumeErrors=True)
- elif len(deferreds) == 1:
- return deferreds[0]
- else:
- return defer.succeed(None)
- def _is_invite_via_3pid(event):
- return (
- event.type == EventTypes.Member
- and event.membership == Membership.INVITE
- and "third_party_invite" in event.content
- )
- def event_from_pdu_json(pdu_json, event_format_version, outlier=False):
- """Construct a FrozenEvent from an event json received over federation
- Args:
- pdu_json (object): pdu as received over federation
- event_format_version (int): The event format version
- outlier (bool): True to mark this event as an outlier
- Returns:
- FrozenEvent
- Raises:
- SynapseError: if the pdu is missing required fields or is otherwise
- not a valid matrix event
- """
- # we could probably enforce a bunch of other fields here (room_id, sender,
- # origin, etc etc)
- assert_params_in_dict(pdu_json, ("type", "depth"))
- depth = pdu_json["depth"]
- if not isinstance(depth, six.integer_types):
- raise SynapseError(400, "Depth %r not an intger" % (depth,), Codes.BAD_JSON)
- if depth < 0:
- raise SynapseError(400, "Depth too small", Codes.BAD_JSON)
- elif depth > MAX_DEPTH:
- raise SynapseError(400, "Depth too large", Codes.BAD_JSON)
- event = event_type_from_format_version(event_format_version)(pdu_json)
- event.internal_metadata.outlier = outlier
- return event
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