156 lines
5.2 KiB
Python
156 lines
5.2 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from synapse.crypto.keyclient import fetch_server_key
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from twisted.internet import defer
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from syutil.crypto.jsonsign import verify_signed_json, signature_ids
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from syutil.crypto.signing_key import (
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is_signing_algorithm_supported, decode_verify_key_bytes
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)
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from syutil.base64util import decode_base64, encode_base64
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from synapse.api.errors import SynapseError, Codes
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from OpenSSL import crypto
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import logging
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logger = logging.getLogger(__name__)
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class Keyring(object):
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def __init__(self, hs):
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self.store = hs.get_datastore()
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self.clock = hs.get_clock()
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self.hs = hs
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@defer.inlineCallbacks
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def verify_json_for_server(self, server_name, json_object):
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logger.debug("Verifying for %s", server_name)
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key_ids = signature_ids(json_object, server_name)
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if not key_ids:
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raise SynapseError(
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400,
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"Not signed with a supported algorithm",
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Codes.UNAUTHORIZED,
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)
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try:
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verify_key = yield self.get_server_verify_key(server_name, key_ids)
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except IOError:
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raise SynapseError(
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502,
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"Error downloading keys for %s" % (server_name,),
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Codes.UNAUTHORIZED,
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)
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except:
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raise SynapseError(
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401,
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"No key for %s with id %s" % (server_name, key_ids),
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Codes.UNAUTHORIZED,
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)
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try:
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verify_signed_json(json_object, server_name, verify_key)
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except:
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raise SynapseError(
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401,
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"Invalid signature for server %s with key %s:%s" % (
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server_name, verify_key.alg, verify_key.version
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),
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Codes.UNAUTHORIZED,
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)
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@defer.inlineCallbacks
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def get_server_verify_key(self, server_name, key_ids):
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"""Finds a verification key for the server with one of the key ids.
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Args:
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server_name (str): The name of the server to fetch a key for.
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keys_ids (list of str): The key_ids to check for.
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"""
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# Check the datastore to see if we have one cached.
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cached = yield self.store.get_server_verify_keys(server_name, key_ids)
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if cached:
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defer.returnValue(cached[0])
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return
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# Try to fetch the key from the remote server.
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# TODO(markjh): Ratelimit requests to a given server.
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(response, tls_certificate) = yield fetch_server_key(
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server_name, self.hs.tls_context_factory
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)
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# Check the response.
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x509_certificate_bytes = crypto.dump_certificate(
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crypto.FILETYPE_ASN1, tls_certificate
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)
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if ("signatures" not in response
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or server_name not in response["signatures"]):
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raise ValueError("Key response not signed by remote server")
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if "tls_certificate" not in response:
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raise ValueError("Key response missing TLS certificate")
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tls_certificate_b64 = response["tls_certificate"]
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if encode_base64(x509_certificate_bytes) != tls_certificate_b64:
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raise ValueError("TLS certificate doesn't match")
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verify_keys = {}
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for key_id, key_base64 in response["verify_keys"].items():
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if is_signing_algorithm_supported(key_id):
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key_bytes = decode_base64(key_base64)
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verify_key = decode_verify_key_bytes(key_id, key_bytes)
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verify_keys[key_id] = verify_key
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for key_id in response["signatures"][server_name]:
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if key_id not in response["verify_keys"]:
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raise ValueError(
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"Key response must include verification keys for all"
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" signatures"
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)
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if key_id in verify_keys:
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verify_signed_json(
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response,
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server_name,
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verify_keys[key_id]
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)
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# Cache the result in the datastore.
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time_now_ms = self.clock.time_msec()
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self.store.store_server_certificate(
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server_name,
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server_name,
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time_now_ms,
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tls_certificate,
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)
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for key_id, key in verify_keys.items():
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self.store.store_server_verify_key(
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server_name, server_name, time_now_ms, key
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)
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for key_id in key_ids:
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if key_id in verify_keys:
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defer.returnValue(verify_keys[key_id])
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return
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raise ValueError("No verification key found for given key ids")
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