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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 FrozenEvent
from synapse.events.utils import prune_event
from synapse.http.servlet import assert_params_in_request
from synapse.util import unwrapFirstError, logcontext
from twisted.internet import defer
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.
"""
redacted_pdus = [
prune_event(pdu)
for pdu in pdus
]
deferreds = self.keyring.verify_json_objects_for_server([
(p.origin, p.get_pdu_json())
for p in redacted_pdus
])
ctx = logcontext.LoggingContext.current_context()
def callback(_, pdu, redacted):
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 redacted
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 redacted
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, redacted in zip(deferreds, pdus, redacted_pdus):
deferred.addCallbacks(
callback, errback,
callbackArgs=[pdu, redacted],
errbackArgs=[pdu],
)
return deferreds
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
"""
# we could probably enforce a bunch of other fields here (room_id, sender,
# origin, etc etc)
assert_params_in_request(pdu_json, ('event_id', 'type'))
event = FrozenEvent(
pdu_json
)
event.internal_metadata.outlier = outlier
return event
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