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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.crypto.event_signing import check_event_content_hash
- from synapse.events import FrozenEvent
- from synapse.events.utils import prune_event
- from synapse.http.servlet import assert_params_in_dict
- from synapse.types import get_domain_from_id
- from synapse.util import logcontext, 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, 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:
- pdu (list)
- outlier (bool)
- Returns:
- Deferred : A list of PDUs that have valid signatures and hashes.
- """
- deferreds = self._check_sigs_and_hashes(pdus)
- @defer.inlineCallbacks
- def handle_check_result(pdu, deferred):
- try:
- res = yield logcontext.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,
- outlier=outlier,
- timeout=10000,
- )
- except SynapseError:
- pass
- if not res:
- logger.warn(
- "Failed to find copy of %s with valid signature",
- pdu.event_id,
- )
- defer.returnValue(res)
- handle = logcontext.preserve_fn(handle_check_result)
- deferreds2 = [
- handle(pdu, deferred)
- for pdu, deferred in zip(pdus, deferreds)
- ]
- valid_pdus = yield logcontext.make_deferred_yieldable(
- defer.gatherResults(
- deferreds2,
- consumeErrors=True,
- )
- ).addErrback(unwrapFirstError)
- if include_none:
- defer.returnValue(valid_pdus)
- else:
- defer.returnValue([p for p in valid_pdus if p])
- def _check_sigs_and_hash(self, pdu):
- return logcontext.make_deferred_yieldable(
- self._check_sigs_and_hashes([pdu])[0],
- )
- def _check_sigs_and_hashes(self, pdus):
- """Checks that each of the received events is correctly signed by the
- sending server.
- Args:
- 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 logcontext.
- """
- deferreds = _check_sigs_on_pdus(self.keyring, pdus)
- ctx = logcontext.LoggingContext.current_context()
- def callback(_, pdu):
- with logcontext.PreserveLoggingContext(ctx):
- if not check_event_content_hash(pdu):
- logger.warn(
- "Event content has been tampered, redacting %s: %s",
- pdu.event_id, pdu.get_pdu_json()
- )
- return prune_event(pdu)
- 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 logcontext.PreserveLoggingContext(ctx):
- logger.warn(
- "Signature check failed for %s",
- pdu.event_id,
- )
- 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", "event_id_domain", "sender_domain", "deferreds",
- ])):
- pass
- def _check_sigs_on_pdus(keyring, pdus):
- """Check that the given events are correctly signed
- Args:
- keyring (synapse.crypto.Keyring): keyring object to do the checks
- 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.
- """
- # (currently this is written assuming the v1 room structure; we'll probably want a
- # separate function for checking v2 rooms)
- # we want to check that the event is signed by:
- #
- # (a) the server which created the event_id
- #
- # (b) 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.
- #
- # 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(),
- event_id_domain=get_domain_from_id(p.event_id),
- sender_domain=get_domain_from_id(p.sender),
- deferreds=[],
- )
- for p in pdus
- ]
- # first make sure that the event is signed by the event_id's domain
- deferreds = keyring.verify_json_objects_for_server([
- (p.event_id_domain, p.redacted_pdu_json)
- for p in pdus_to_check
- ])
- for p, d in zip(pdus_to_check, deferreds):
- 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.
- pdus_to_check_sender = [
- p for p in pdus_to_check
- if p.sender_domain != p.event_id_domain and not _is_invite_via_3pid(p.pdu)
- ]
- more_deferreds = keyring.verify_json_objects_for_server([
- (p.sender_domain, p.redacted_pdu_json)
- for p in pdus_to_check_sender
- ])
- for p, d in zip(pdus_to_check_sender, more_deferreds):
- 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 one or more deferreds, either return the single deferred, or
- combine into a DeferredList.
- """
- if len(deferreds) > 1:
- return DeferredList(deferreds, fireOnOneErrback=True, consumeErrors=True)
- else:
- assert len(deferreds) == 1
- return deferreds[0]
- 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, outlier=False):
- """Construct a FrozenEvent from an event json received over federation
- Args:
- pdu_json (object): pdu as received over federation
- 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, ('event_id', '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 = FrozenEvent(
- pdu_json
- )
- event.internal_metadata.outlier = outlier
- return event
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