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# -*- coding: utf-8 -*-
# Copyright 2014 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 synapse.crypto.keyclient import fetch_server_key
from twisted.internet import defer
from syutil.crypto.jsonsign import verify_signed_json, signature_ids
from syutil.crypto.signing_key import (
is_signing_algorithm_supported, decode_verify_key_bytes
)
from syutil.base64util import decode_base64, encode_base64
from synapse.api.errors import SynapseError, Codes
from OpenSSL import crypto
import logging
logger = logging.getLogger(__name__)
class Keyring(object):
def __init__(self, hs):
self.store = hs.get_datastore()
self.clock = hs.get_clock()
self.hs = hs
@defer.inlineCallbacks
def verify_json_for_server(self, server_name, json_object):
logger.debug("Verifying for %s", server_name)
key_ids = signature_ids(json_object, server_name)
if not key_ids:
raise SynapseError(
400,
"Not signed with a supported algorithm",
Codes.UNAUTHORIZED,
)
try:
verify_key = yield self.get_server_verify_key(server_name, key_ids)
except IOError:
raise SynapseError(
502,
"Error downloading keys for %s" % (server_name,),
Codes.UNAUTHORIZED,
)
except:
raise SynapseError(
401,
"No key for %s with id %s" % (server_name, key_ids),
Codes.UNAUTHORIZED,
)
try:
verify_signed_json(json_object, server_name, verify_key)
except:
raise SynapseError(
401,
"Invalid signature for server %s with key %s:%s" % (
server_name, verify_key.alg, verify_key.version
),
Codes.UNAUTHORIZED,
)
@defer.inlineCallbacks
def get_server_verify_key(self, server_name, key_ids):
"""Finds a verification key for the server with one of the key ids.
Args:
server_name (str): The name of the server to fetch a key for.
keys_ids (list of str): The key_ids to check for.
"""
# Check the datastore to see if we have one cached.
cached = yield self.store.get_server_verify_keys(server_name, key_ids)
if cached:
defer.returnValue(cached[0])
return
# Try to fetch the key from the remote server.
# TODO(markjh): Ratelimit requests to a given server.
(response, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_context_factory
)
# Check the response.
x509_certificate_bytes = crypto.dump_certificate(
crypto.FILETYPE_ASN1, tls_certificate
)
if ("signatures" not in response
or server_name not in response["signatures"]):
raise ValueError("Key response not signed by remote server")
if "tls_certificate" not in response:
raise ValueError("Key response missing TLS certificate")
tls_certificate_b64 = response["tls_certificate"]
if encode_base64(x509_certificate_bytes) != tls_certificate_b64:
raise ValueError("TLS certificate doesn't match")
verify_keys = {}
for key_id, key_base64 in response["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_keys[key_id] = verify_key
for key_id in response["signatures"][server_name]:
if key_id not in response["verify_keys"]:
raise ValueError(
"Key response must include verification keys for all"
" signatures"
)
if key_id in verify_keys:
verify_signed_json(
response,
server_name,
verify_keys[key_id]
)
# Cache the result in the datastore.
time_now_ms = self.clock.time_msec()
self.store.store_server_certificate(
server_name,
server_name,
time_now_ms,
tls_certificate,
)
for key_id, key in verify_keys.items():
self.store.store_server_verify_key(
server_name, server_name, time_now_ms, key
)
for key_id in key_ids:
if key_id in verify_keys:
defer.returnValue(verify_keys[key_id])
return
raise ValueError("No verification key found for given key ids")
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