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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 synapse.api.errors import SynapseError
from synapse.crypto.event_signing import check_event_content_hash
from synapse.events import spamcheck
from synapse.events.utils import prune_event
from synapse.util import unwrapFirstError
from synapse.util.logcontext import preserve_context_over_deferred, preserve_fn
from twisted.internet import defer
logger = logging.getLogger(__name__)
class FederationBase(object):
def __init__(self, hs):
pass
@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)
def callback(pdu):
return pdu
def errback(failure, pdu):
failure.trap(SynapseError)
return None
def try_local_db(res, pdu):
if not res:
# Check local db.
return self.store.get_event(
pdu.event_id,
allow_rejected=True,
allow_none=True,
)
return res
def try_remote(res, pdu):
if not res and pdu.origin != origin:
return self.get_pdu(
destinations=[pdu.origin],
event_id=pdu.event_id,
outlier=outlier,
timeout=10000,
).addErrback(lambda e: None)
return res
def warn(res, pdu):
if not res:
logger.warn(
"Failed to find copy of %s with valid signature",
pdu.event_id,
)
return res
for pdu, deferred in zip(pdus, deferreds):
deferred.addCallbacks(
callback, errback, errbackArgs=[pdu]
).addCallback(
try_local_db, pdu
).addCallback(
try_remote, pdu
).addCallback(
warn, pdu
)
valid_pdus = yield preserve_context_over_deferred(defer.gatherResults(
deferreds,
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 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.
"""
redacted_pdus = [
prune_event(pdu)
for pdu in pdus
]
deferreds = preserve_fn(self.keyring.verify_json_objects_for_server)([
(p.origin, p.get_pdu_json())
for p in redacted_pdus
])
def callback(_, pdu, redacted):
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 redacted
if spamcheck.check_event_for_spam(pdu):
logger.warn(
"Event contains spam, redacting %s: %s",
pdu.event_id, pdu.get_pdu_json()
)
return redacted
return pdu
def errback(failure, pdu):
failure.trap(SynapseError)
logger.warn(
"Signature check failed for %s",
pdu.event_id,
)
return failure
for deferred, pdu, redacted in zip(deferreds, pdus, redacted_pdus):
deferred.addCallbacks(
callback, errback,
callbackArgs=[pdu, redacted],
errbackArgs=[pdu],
)
return deferreds
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