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# 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
import re
from typing import TYPE_CHECKING, Dict, Optional, Set, Tuple
from signedjson.sign import sign_json
from twisted.web.server import Request
from synapse.crypto.keyring import ServerKeyFetcher
from synapse.http.server import HttpServer
from synapse.http.servlet import (
RestServlet,
parse_integer,
parse_json_object_from_request,
)
from synapse.types import JsonDict
from synapse.util import json_decoder
from synapse.util.async_helpers import yieldable_gather_results
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class RemoteKey(RestServlet):
"""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.
}
}
"signatures": {
"remote.server.example.com": {...}
"this.server.example.com": {...}
}
}
]
}
"""
def __init__(self, hs: "HomeServer"):
self.fetcher = ServerKeyFetcher(hs)
self.store = hs.get_datastores().main
self.clock = hs.get_clock()
self.federation_domain_whitelist = (
hs.config.federation.federation_domain_whitelist
)
self.config = hs.config
def register(self, http_server: HttpServer) -> None:
http_server.register_paths(
"GET",
(
re.compile(
"^/_matrix/key/v2/query/(?P<server>[^/]*)(/(?P<key_id>[^/]*))?$"
),
),
self.on_GET,
self.__class__.__name__,
)
http_server.register_paths(
"POST",
(re.compile("^/_matrix/key/v2/query$"),),
self.on_POST,
self.__class__.__name__,
)
async def on_GET(
self, request: Request, server: str, key_id: Optional[str] = None
) -> Tuple[int, JsonDict]:
if server and key_id:
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: {key_id: arguments}}
else:
query = {server: {}}
return 200, await self.query_keys(query, query_remote_on_cache_miss=True)
async def on_POST(self, request: Request) -> Tuple[int, JsonDict]:
content = parse_json_object_from_request(request)
query = content["server_keys"]
return 200, await self.query_keys(query, query_remote_on_cache_miss=True)
async def query_keys(
self, query: JsonDict, query_remote_on_cache_miss: bool = False
) -> JsonDict:
logger.info("Handling query for keys %r", query)
store_queries = []
for server_name, key_ids in query.items():
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[bytes] = set()
time_now_ms = self.clock.time_msec()
# Map server_name->key_id->int. Note that the value of the init is unused.
# XXX: why don't we just use a set?
cache_misses: Dict[str, Dict[str, int]] = {}
for (server_name, key_id, _), key_results in cached.items():
results = [(result["ts_added_ms"], result) for result in key_results]
if key_id is None:
# all keys were requested. Just return what we have without worrying
# about validity
for _, result in results:
# Cast to bytes since postgresql returns a memoryview.
json_results.add(bytes(result["key_json"]))
continue
miss = False
if not results:
miss = True
else:
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")
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,
)
# Cast to bytes since postgresql returns a memoryview.
json_results.add(bytes(most_recent_result["key_json"]))
if miss and query_remote_on_cache_miss:
# only bother attempting to fetch keys from servers on our whitelist
if (
self.federation_domain_whitelist is None
or server_name in self.federation_domain_whitelist
):
cache_misses.setdefault(server_name, {})[key_id] = 0
# If there is a cache miss, request the missing keys, then recurse (and
# ensure the result is sent).
if cache_misses:
await yieldable_gather_results(
lambda t: self.fetcher.get_keys(*t),
(
(server_name, list(keys), 0)
for server_name, keys in cache_misses.items()
),
)
return await self.query_keys(query, query_remote_on_cache_miss=False)
else:
signed_keys = []
for key_json_raw in json_results:
key_json = json_decoder.decode(key_json_raw.decode("utf-8"))
for signing_key in self.config.key.key_server_signing_keys:
key_json = sign_json(
key_json, self.config.server.server_name, signing_key
)
signed_keys.append(key_json)
return {"server_keys": signed_keys}
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