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# -*- coding: utf-8 -*-
# Copyright 2017 Vector Creations 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.api.errors import SynapseError
from synapse.types import get_domain_from_id
from synapse.util.logcontext import preserve_fn
from signedjson.sign import sign_json
# Default validity duration for new attestations we create
DEFAULT_ATTESTATION_LENGTH_MS = 3 * 24 * 60 * 60 * 1000
# Start trying to update our attestations when they come this close to expiring
UPDATE_ATTESTATION_TIME_MS = 1 * 24 * 60 * 60 * 1000
class GroupAttestationSigning(object):
"""Creates and verifies group attestations.
"""
def __init__(self, hs):
self.keyring = hs.get_keyring()
self.clock = hs.get_clock()
self.server_name = hs.hostname
self.signing_key = hs.config.signing_key[0]
@defer.inlineCallbacks
def verify_attestation(self, attestation, group_id, user_id, server_name=None):
"""Verifies that the given attestation matches the given parameters.
An optional server_name can be supplied to explicitly set which server's
signature is expected. Otherwise assumes that either the group_id or user_id
is local and uses the other's server as the one to check.
"""
if not server_name:
if get_domain_from_id(group_id) == self.server_name:
server_name = get_domain_from_id(user_id)
elif get_domain_from_id(user_id) == self.server_name:
server_name = get_domain_from_id(group_id)
else:
raise Exception("Expected either group_id or user_id to be local")
if user_id != attestation["user_id"]:
raise SynapseError(400, "Attestation has incorrect user_id")
if group_id != attestation["group_id"]:
raise SynapseError(400, "Attestation has incorrect group_id")
valid_until_ms = attestation["valid_until_ms"]
# TODO: We also want to check that *new* attestations that people give
# us to store are valid for at least a little while.
if valid_until_ms < self.clock.time_msec():
raise SynapseError(400, "Attestation expired")
yield self.keyring.verify_json_for_server(server_name, attestation)
def create_attestation(self, group_id, user_id):
"""Create an attestation for the group_id and user_id with default
validity length.
"""
return sign_json({
"group_id": group_id,
"user_id": user_id,
"valid_until_ms": self.clock.time_msec() + DEFAULT_ATTESTATION_LENGTH_MS,
}, self.server_name, self.signing_key)
class GroupAttestionRenewer(object):
"""Responsible for sending and receiving attestation updates.
"""
def __init__(self, hs):
self.clock = hs.get_clock()
self.store = hs.get_datastore()
self.assestations = hs.get_groups_attestation_signing()
self.transport_client = hs.get_federation_transport_client()
self.is_mine_id = hs.is_mine_id
self.attestations = hs.get_groups_attestation_signing()
self._renew_attestations_loop = self.clock.looping_call(
self._renew_attestations, 30 * 60 * 1000,
)
@defer.inlineCallbacks
def on_renew_attestation(self, group_id, user_id, content):
"""When a remote updates an attestation
"""
attestation = content["attestation"]
if not self.is_mine_id(group_id) and not self.is_mine_id(user_id):
raise SynapseError(400, "Neither user not group are on this server")
yield self.attestations.verify_attestation(
attestation,
user_id=user_id,
group_id=group_id,
)
yield self.store.update_remote_attestion(group_id, user_id, attestation)
defer.returnValue({})
@defer.inlineCallbacks
def _renew_attestations(self):
"""Called periodically to check if we need to update any of our attestations
"""
now = self.clock.time_msec()
rows = yield self.store.get_attestations_need_renewals(
now + UPDATE_ATTESTATION_TIME_MS
)
@defer.inlineCallbacks
def _renew_attestation(group_id, user_id):
attestation = self.attestations.create_attestation(group_id, user_id)
if self.is_mine_id(group_id):
destination = get_domain_from_id(user_id)
else:
destination = get_domain_from_id(group_id)
yield self.transport_client.renew_group_attestation(
destination, group_id, user_id,
content={"attestation": attestation},
)
yield self.store.update_attestation_renewal(
group_id, user_id, attestation
)
for row in rows:
group_id = row["group_id"]
user_id = row["user_id"]
preserve_fn(_renew_attestation)(group_id, user_id)
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