diff options
| -rw-r--r-- | synapse/federation/federation_base.py | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py new file mode 100644 index 0000000000..d26a2396ac --- /dev/null +++ b/synapse/federation/federation_base.py @@ -0,0 +1,126 @@ +# -*- coding: utf-8 -*- +# Copyright 2015 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. + + +from twisted.internet import defer + +from synapse.events.utils import prune_event, old_prune_event + +from syutil.jsonutil import encode_canonical_json + +from synapse.crypto.event_signing import check_event_content_hash + +from synapse.api.errors import SynapseError + +import logging + + +logger = logging.getLogger(__name__) + + +class FederationBase(object): + @defer.inlineCallbacks + def _check_sigs_and_hash_and_fetch(self, origin, pdus, outlier=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. + """ + signed_pdus = [] + for pdu in pdus: + try: + new_pdu = yield self._check_sigs_and_hash(pdu) + signed_pdus.append(new_pdu) + except SynapseError: + # FIXME: We should handle signature failures more gracefully. + + # Check local db. + new_pdu = yield self.store.get_event( + pdu.event_id, + allow_rejected=True + ) + if new_pdu: + signed_pdus.append(new_pdu) + continue + + # Check pdu.origin + if pdu.origin != origin: + new_pdu = yield self.get_pdu( + destinations=[pdu.origin], + event_id=pdu.event_id, + outlier=outlier, + ) + + if new_pdu: + signed_pdus.append(new_pdu) + continue + + logger.warn("Failed to find copy of %s with valid signature") + + defer.returnValue(signed_pdus) + + @defer.inlineCallbacks + def _check_sigs_and_hash(self, pdu): + """Throws a SynapseError if the PDU does not have the correct + signatures. + + Returns: + FrozenEvent: Either the given event or it redacted if it failed the + content hash check. + """ + # Check signatures are correct. + redacted_event = prune_event(pdu) + redacted_pdu_json = redacted_event.get_pdu_json() + + old_redacted = old_prune_event(pdu) + old_redacted_pdu_json = old_redacted.get_pdu_json() + + try: + try: + yield self.keyring.verify_json_for_server( + pdu.origin, old_redacted_pdu_json + ) + except SynapseError: + yield self.keyring.verify_json_for_server( + pdu.origin, redacted_pdu_json + ) + except SynapseError: + logger.warn( + "Signature check failed for %s redacted to %s", + encode_canonical_json(pdu.get_pdu_json()), + encode_canonical_json(redacted_pdu_json), + ) + raise + + if not check_event_content_hash(pdu): + logger.warn( + "Event content has been tampered, redacting %s, %s", + pdu.event_id, encode_canonical_json(pdu.get_dict()) + ) + defer.returnValue(redacted_event) + + defer.returnValue(pdu) \ No newline at end of file |