# 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 typing import Dict
from signedjson.sign import sign_json
from synapse.api.errors import Codes, SynapseError
from synapse.crypto.keyring import ServerKeyFetcher
from synapse.http.server import DirectServeJsonResource, respond_with_json
from synapse.http.servlet import parse_integer, parse_json_object_from_request
from synapse.util import json_decoder
logger = logging.getLogger(__name__)
class RemoteKey(DirectServeJsonResource):
"""HTTP resource for retrieving the TLS certificate and NACL signature
verification keys for a collection of servers. Checks that the reported
X.509 TLS certificate matches the one used in the HTTPS connection. Checks
that the NACL signature for the remote server is valid. Returns a dict of
JSON signed by both the remote server and by this server.
Supports individual GET APIs and a bulk query POST API.
Requests:
GET /_matrix/key/v2/query/remote.server.example.com HTTP/1.1
GET /_matrix/key/v2/query/remote.server.example.com/a.key.id HTTP/1.1
POST /_matrix/v2/query HTTP/1.1
Content-Type: application/json
{
"server_keys": {
"remote.server.example.com": {
"a.key.id": {
"minimum_valid_until_ts": 1234567890123
}
}
}
}
Response:
HTTP/1.1 200 OK
Content-Type: application/json
{
"server_keys": [
{
"server_name": "remote.server.example.com"
"valid_until_ts": # posix timestamp
"verify_keys": {
"a.key.id": { # The identifier for a key.
key: "" # base64 encoded verification key.
}
}
"old_verify_keys": {
"an.old.key.id": { # The identifier for an old key.
key: "", # base64 encoded key
"expired_ts": 0, # when the key stop being used.
}
}
"tls_fingerprints": [
{ "sha256": # fingerprint }
]
"signatures": {
"remote.server.example.com": {...}
"this.server.example.com": {...}
}
}
]
}
"""
isLeaf = True
def __init__(self, hs):
super().__init__()
self.fetcher = ServerKeyFetcher(hs)
self.store = hs.get_datastore()
self.clock = hs.get_clock()
self.federation_domain_whitelist = hs.config.federation_domain_whitelist
self.config = hs.config
async def _async_render_GET(self, request):
if len(request.postpath) == 1:
(server,) = request.postpath
query = {server.decode("ascii"): {}} # type: dict
elif len(request.postpath) == 2:
server, key_id = request.postpath
minimum_valid_until_ts = parse_integer(request, "minimum_valid_until_ts")
arguments = {}
if minimum_valid_until_ts is not None:
arguments["minimum_valid_until_ts"] = minimum_valid_until_ts
query = {server.decode("ascii"): {key_id.decode("ascii"): arguments}}
else:
raise SynapseError(404, "Not found %r" % request.postpath, Codes.NOT_FOUND)
await self.query_keys(request, query, query_remote_on_cache_miss=True)
async def _async_render_POST(self, request):
content = parse_json_object_from_request(request)
query = content["server_keys"]
await self.query_keys(request, query, query_remote_on_cache_miss=True)
async def query_keys(self, request, query, query_remote_on_cache_miss=False):
logger.info("Handling query for keys %r", query)
store_queries = []
for server_name, key_ids in query.items():
if (
self.federation_domain_whitelist is not None
and server_name not in self.federation_domain_whitelist
):
logger.debug("Federation denied with %s", server_name)
continue
if not key_ids:
key_ids = (None,)
for key_id in key_ids:
store_queries.append((server_name, key_id, None))
cached = await self.store.get_server_keys_json(store_queries)
json_results = set()
time_now_ms = self.clock.time_msec()
# Note that the value is unused.
cache_misses = {} # type: Dict[str, Dict[str, int]]
for (server_name, key_id, from_server), results in cached.items():
results = [(result["ts_added_ms"], result) for result in results]
if not results and key_id is not None:
cache_misses.setdefault(server_name, {})[key_id] = 0
continue
if key_id is not None:
ts_added_ms, most_recent_result = max(results)
ts_valid_until_ms = most_recent_result["ts_valid_until_ms"]
req_key = query.get(server_name, {}).get(key_id, {})
req_valid_until = req_key.get("minimum_valid_until_ts")
miss = False
if req_valid_until is not None:
if ts_valid_until_ms < req_valid_until:
logger.debug(
"Cached response for %r/%r is older than requested"
": valid_until (%r) < minimum_valid_until (%r)",
server_name,
key_id,
ts_valid_until_ms,
req_valid_until,
)
miss = True
else:
logger.debug(
"Cached response for %r/%r is newer than requested"
": valid_until (%r) >= minimum_valid_until (%r)",
server_name,
key_id,
ts_valid_until_ms,
req_valid_until,
)
elif (ts_added_ms + ts_valid_until_ms) / 2 < time_now_ms:
logger.debug(
"Cached response for %r/%r is too old"
": (added (%r) + valid_until (%r)) / 2 < now (%r)",
server_name,
key_id,
ts_added_ms,
ts_valid_until_ms,
time_now_ms,
)
# We more than half way through the lifetime of the
# response. We should fetch a fresh copy.
miss = True
else:
logger.debug(
"Cached response for %r/%r is still valid"
": (added (%r) + valid_until (%r)) / 2 < now (%r)",
server_name,
key_id,
ts_added_ms,
ts_valid_until_ms,
time_now_ms,
)
if miss:
cache_misses.setdefault(server_name, {})[key_id] = 0
# Cast to bytes since postgresql returns a memoryview.
json_results.add(bytes(most_recent_result["key_json"]))
else:
for ts_added, result in results:
# Cast to bytes since postgresql returns a memoryview.
json_results.add(bytes(result["key_json"]))
# If there is a cache miss, request the missing keys, then recurse (and
# ensure the result is sent).
if cache_misses and query_remote_on_cache_miss:
await self.fetcher.get_keys(cache_misses)
await self.query_keys(request, query, query_remote_on_cache_miss=False)
else:
signed_keys = []
for key_json in json_results:
key_json = json_decoder.decode(key_json.decode("utf-8"))
for signing_key in self.config.key_server_signing_keys:
key_json = sign_json(key_json, self.config.server_name, signing_key)
signed_keys.append(key_json)
results = {"server_keys": signed_keys}
respond_with_json(request, 200, results, canonical_json=True)