synapse-product/synapse/handlers/e2e_keys.py
Sean Quah c73774467e
Fix bug in device list caching when remote users leave rooms (#13749)
When a remote user leaves the last room shared with the homeserver, we
have to mark their device list as unsubscribed, otherwise we would hold
on to a stale device list in our cache. Crucially, the device list would
remain cached even after the remote user rejoined the room, which could
lead to E2EE failures until the next change to the remote user's device
list.

Fixes #13651.

Signed-off-by: Sean Quah <seanq@matrix.org>
2022-09-14 10:42:57 +01:00

1440 lines
57 KiB
Python

# Copyright 2016 OpenMarket Ltd
# Copyright 2018-2019 New Vector Ltd
# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# 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 TYPE_CHECKING, Any, Dict, Iterable, List, Mapping, Optional, Tuple
import attr
from canonicaljson import encode_canonical_json
from signedjson.key import VerifyKey, decode_verify_key_bytes
from signedjson.sign import SignatureVerifyException, verify_signed_json
from unpaddedbase64 import decode_base64
from twisted.internet import defer
from synapse.api.constants import EduTypes
from synapse.api.errors import CodeMessageException, Codes, NotFoundError, SynapseError
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.logging.opentracing import log_kv, set_tag, tag_args, trace
from synapse.replication.http.devices import ReplicationUserDevicesResyncRestServlet
from synapse.types import (
JsonDict,
UserID,
get_domain_from_id,
get_verify_key_from_cross_signing_key,
)
from synapse.util import json_decoder, unwrapFirstError
from synapse.util.async_helpers import Linearizer, delay_cancellation
from synapse.util.cancellation import cancellable
from synapse.util.retryutils import NotRetryingDestination
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class E2eKeysHandler:
def __init__(self, hs: "HomeServer"):
self.store = hs.get_datastores().main
self.federation = hs.get_federation_client()
self.device_handler = hs.get_device_handler()
self.is_mine = hs.is_mine
self.clock = hs.get_clock()
self._edu_updater = SigningKeyEduUpdater(hs, self)
federation_registry = hs.get_federation_registry()
self._is_master = hs.config.worker.worker_app is None
if not self._is_master:
self._user_device_resync_client = (
ReplicationUserDevicesResyncRestServlet.make_client(hs)
)
else:
# Only register this edu handler on master as it requires writing
# device updates to the db
federation_registry.register_edu_handler(
EduTypes.SIGNING_KEY_UPDATE,
self._edu_updater.incoming_signing_key_update,
)
# also handle the unstable version
# FIXME: remove this when enough servers have upgraded
federation_registry.register_edu_handler(
EduTypes.UNSTABLE_SIGNING_KEY_UPDATE,
self._edu_updater.incoming_signing_key_update,
)
# doesn't really work as part of the generic query API, because the
# query request requires an object POST, but we abuse the
# "query handler" interface.
federation_registry.register_query_handler(
"client_keys", self.on_federation_query_client_keys
)
# Limit the number of in-flight requests from a single device.
self._query_devices_linearizer = Linearizer(
name="query_devices",
max_count=10,
)
@trace
@cancellable
async def query_devices(
self,
query_body: JsonDict,
timeout: int,
from_user_id: str,
from_device_id: Optional[str],
) -> JsonDict:
"""Handle a device key query from a client
{
"device_keys": {
"<user_id>": ["<device_id>"]
}
}
->
{
"device_keys": {
"<user_id>": {
"<device_id>": {
...
}
}
}
}
Args:
from_user_id: the user making the query. This is used when
adding cross-signing signatures to limit what signatures users
can see.
from_device_id: the device making the query. This is used to limit
the number of in-flight queries at a time.
"""
async with self._query_devices_linearizer.queue((from_user_id, from_device_id)):
device_keys_query: Dict[str, List[str]] = query_body.get("device_keys", {})
# separate users by domain.
# make a map from domain to user_id to device_ids
local_query = {}
remote_queries = {}
for user_id, device_ids in device_keys_query.items():
# we use UserID.from_string to catch invalid user ids
if self.is_mine(UserID.from_string(user_id)):
local_query[user_id] = device_ids
else:
remote_queries[user_id] = device_ids
set_tag("local_key_query", str(local_query))
set_tag("remote_key_query", str(remote_queries))
# First get local devices.
# A map of destination -> failure response.
failures: Dict[str, JsonDict] = {}
results = {}
if local_query:
local_result = await self.query_local_devices(local_query)
for user_id, keys in local_result.items():
if user_id in local_query:
results[user_id] = keys
# Get cached cross-signing keys
cross_signing_keys = await self.get_cross_signing_keys_from_cache(
device_keys_query, from_user_id
)
# Now attempt to get any remote devices from our local cache.
# A map of destination -> user ID -> device IDs.
remote_queries_not_in_cache: Dict[str, Dict[str, Iterable[str]]] = {}
if remote_queries:
query_list: List[Tuple[str, Optional[str]]] = []
for user_id, device_ids in remote_queries.items():
if device_ids:
query_list.extend(
(user_id, device_id) for device_id in device_ids
)
else:
query_list.append((user_id, None))
(
user_ids_not_in_cache,
remote_results,
) = await self.store.get_user_devices_from_cache(query_list)
# Check that the homeserver still shares a room with all cached users.
# Note that this check may be slightly racy when a remote user leaves a
# room after we have fetched their cached device list. In the worst case
# we will do extra federation queries for devices that we had cached.
cached_users = set(remote_results.keys())
valid_cached_users = (
await self.store.get_users_server_still_shares_room_with(
remote_results.keys()
)
)
invalid_cached_users = cached_users - valid_cached_users
if invalid_cached_users:
# Fix up results. If we get here, there is either a bug in device
# list tracking, or we hit the race mentioned above.
user_ids_not_in_cache.update(invalid_cached_users)
for invalid_user_id in invalid_cached_users:
remote_results.pop(invalid_user_id)
# This log message may be removed if it turns out it's almost
# entirely triggered by races.
logger.error(
"Devices for %s were cached, but the server no longer shares "
"any rooms with them. The cached device lists are stale.",
invalid_cached_users,
)
for user_id, devices in remote_results.items():
user_devices = results.setdefault(user_id, {})
for device_id, device in devices.items():
keys = device.get("keys", None)
device_display_name = device.get("device_display_name", None)
if keys:
result = dict(keys)
unsigned = result.setdefault("unsigned", {})
if device_display_name:
unsigned["device_display_name"] = device_display_name
user_devices[device_id] = result
# check for missing cross-signing keys.
for user_id in remote_queries.keys():
cached_cross_master = user_id in cross_signing_keys["master_keys"]
cached_cross_selfsigning = (
user_id in cross_signing_keys["self_signing_keys"]
)
# check if we are missing only one of cross-signing master or
# self-signing key, but the other one is cached.
# as we need both, this will issue a federation request.
# if we don't have any of the keys, either the user doesn't have
# cross-signing set up, or the cached device list
# is not (yet) updated.
if cached_cross_master ^ cached_cross_selfsigning:
user_ids_not_in_cache.add(user_id)
# add those users to the list to fetch over federation.
for user_id in user_ids_not_in_cache:
domain = get_domain_from_id(user_id)
r = remote_queries_not_in_cache.setdefault(domain, {})
r[user_id] = remote_queries[user_id]
# Now fetch any devices that we don't have in our cache
# TODO It might make sense to propagate cancellations into the
# deferreds which are querying remote homeservers.
await make_deferred_yieldable(
delay_cancellation(
defer.gatherResults(
[
run_in_background(
self._query_devices_for_destination,
results,
cross_signing_keys,
failures,
destination,
queries,
timeout,
)
for destination, queries in remote_queries_not_in_cache.items()
],
consumeErrors=True,
).addErrback(unwrapFirstError)
)
)
ret = {"device_keys": results, "failures": failures}
ret.update(cross_signing_keys)
return ret
@trace
async def _query_devices_for_destination(
self,
results: JsonDict,
cross_signing_keys: JsonDict,
failures: Dict[str, JsonDict],
destination: str,
destination_query: Dict[str, Iterable[str]],
timeout: int,
) -> None:
"""This is called when we are querying the device list of a user on
a remote homeserver and their device list is not in the device list
cache. If we share a room with this user and we're not querying for
specific user we will update the cache with their device list.
Args:
results: A map from user ID to their device keys, which gets
updated with the newly fetched keys.
cross_signing_keys: Map from user ID to their cross signing keys,
which gets updated with the newly fetched keys.
failures: Map of destinations to failures that have occurred while
attempting to fetch keys.
destination: The remote server to query
destination_query: The query dict of devices to query the remote
server for.
timeout: The timeout for remote HTTP requests.
"""
# We first consider whether we wish to update the device list cache with
# the users device list. We want to track a user's devices when the
# authenticated user shares a room with the queried user and the query
# has not specified a particular device.
# If we update the cache for the queried user we remove them from further
# queries. We use the more efficient batched query_client_keys for all
# remaining users
user_ids_updated = []
for (user_id, device_list) in destination_query.items():
if user_id in user_ids_updated:
continue
if device_list:
continue
room_ids = await self.store.get_rooms_for_user(user_id)
if not room_ids:
continue
# We've decided we're sharing a room with this user and should
# probably be tracking their device lists. However, we haven't
# done an initial sync on the device list so we do it now.
try:
if self._is_master:
resync_results = await self.device_handler.device_list_updater.user_device_resync(
user_id
)
else:
resync_results = await self._user_device_resync_client(
user_id=user_id
)
# Add the device keys to the results.
user_devices = resync_results["devices"]
user_results = results.setdefault(user_id, {})
for device in user_devices:
user_results[device["device_id"]] = device["keys"]
user_ids_updated.append(user_id)
# Add any cross signing keys to the results.
master_key = resync_results.get("master_key")
self_signing_key = resync_results.get("self_signing_key")
if master_key:
cross_signing_keys["master_keys"][user_id] = master_key
if self_signing_key:
cross_signing_keys["self_signing_keys"][user_id] = self_signing_key
except Exception as e:
failures[destination] = _exception_to_failure(e)
if len(destination_query) == len(user_ids_updated):
# We've updated all the users in the query and we do not need to
# make any further remote calls.
return
# Remove all the users from the query which we have updated
for user_id in user_ids_updated:
destination_query.pop(user_id)
try:
remote_result = await self.federation.query_client_keys(
destination, {"device_keys": destination_query}, timeout=timeout
)
for user_id, keys in remote_result["device_keys"].items():
if user_id in destination_query:
results[user_id] = keys
if "master_keys" in remote_result:
for user_id, key in remote_result["master_keys"].items():
if user_id in destination_query:
cross_signing_keys["master_keys"][user_id] = key
if "self_signing_keys" in remote_result:
for user_id, key in remote_result["self_signing_keys"].items():
if user_id in destination_query:
cross_signing_keys["self_signing_keys"][user_id] = key
except Exception as e:
failure = _exception_to_failure(e)
failures[destination] = failure
set_tag("error", True)
set_tag("reason", str(failure))
return
@cancellable
async def get_cross_signing_keys_from_cache(
self, query: Iterable[str], from_user_id: Optional[str]
) -> Dict[str, Dict[str, dict]]:
"""Get cross-signing keys for users from the database
Args:
query: an iterable of user IDs. A dict whose keys
are user IDs satisfies this, so the query format used for
query_devices can be used here.
from_user_id: the user making the query. This is used when
adding cross-signing signatures to limit what signatures users
can see.
Returns:
A map from (master_keys|self_signing_keys|user_signing_keys) -> user_id -> key
"""
master_keys = {}
self_signing_keys = {}
user_signing_keys = {}
user_ids = list(query)
keys = await self.store.get_e2e_cross_signing_keys_bulk(user_ids, from_user_id)
for user_id, user_info in keys.items():
if user_info is None:
continue
if "master" in user_info:
master_keys[user_id] = user_info["master"]
if "self_signing" in user_info:
self_signing_keys[user_id] = user_info["self_signing"]
# users can see other users' master and self-signing keys, but can
# only see their own user-signing keys
if from_user_id:
from_user_key = keys.get(from_user_id)
if from_user_key and "user_signing" in from_user_key:
user_signing_keys[from_user_id] = from_user_key["user_signing"]
return {
"master_keys": master_keys,
"self_signing_keys": self_signing_keys,
"user_signing_keys": user_signing_keys,
}
@trace
@cancellable
async def query_local_devices(
self, query: Mapping[str, Optional[List[str]]]
) -> Dict[str, Dict[str, dict]]:
"""Get E2E device keys for local users
Args:
query: map from user_id to a list
of devices to query (None for all devices)
Returns:
A map from user_id -> device_id -> device details
"""
set_tag("local_query", str(query))
local_query: List[Tuple[str, Optional[str]]] = []
result_dict: Dict[str, Dict[str, dict]] = {}
for user_id, device_ids in query.items():
# we use UserID.from_string to catch invalid user ids
if not self.is_mine(UserID.from_string(user_id)):
logger.warning("Request for keys for non-local user %s", user_id)
log_kv(
{
"message": "Requested a local key for a user which"
" was not local to the homeserver",
"user_id": user_id,
}
)
set_tag("error", True)
raise SynapseError(400, "Not a user here")
if not device_ids:
local_query.append((user_id, None))
else:
for device_id in device_ids:
local_query.append((user_id, device_id))
# make sure that each queried user appears in the result dict
result_dict[user_id] = {}
results = await self.store.get_e2e_device_keys_for_cs_api(local_query)
# Build the result structure
for user_id, device_keys in results.items():
for device_id, device_info in device_keys.items():
result_dict[user_id][device_id] = device_info
log_kv(results)
return result_dict
async def on_federation_query_client_keys(
self, query_body: Dict[str, Dict[str, Optional[List[str]]]]
) -> JsonDict:
"""Handle a device key query from a federated server"""
device_keys_query: Dict[str, Optional[List[str]]] = query_body.get(
"device_keys", {}
)
res = await self.query_local_devices(device_keys_query)
ret = {"device_keys": res}
# add in the cross-signing keys
cross_signing_keys = await self.get_cross_signing_keys_from_cache(
device_keys_query, None
)
ret.update(cross_signing_keys)
return ret
@trace
async def claim_one_time_keys(
self, query: Dict[str, Dict[str, Dict[str, str]]], timeout: Optional[int]
) -> JsonDict:
local_query: List[Tuple[str, str, str]] = []
remote_queries: Dict[str, Dict[str, Dict[str, str]]] = {}
for user_id, one_time_keys in query.get("one_time_keys", {}).items():
# we use UserID.from_string to catch invalid user ids
if self.is_mine(UserID.from_string(user_id)):
for device_id, algorithm in one_time_keys.items():
local_query.append((user_id, device_id, algorithm))
else:
domain = get_domain_from_id(user_id)
remote_queries.setdefault(domain, {})[user_id] = one_time_keys
set_tag("local_key_query", str(local_query))
set_tag("remote_key_query", str(remote_queries))
results = await self.store.claim_e2e_one_time_keys(local_query)
# A map of user ID -> device ID -> key ID -> key.
json_result: Dict[str, Dict[str, Dict[str, JsonDict]]] = {}
failures: Dict[str, JsonDict] = {}
for user_id, device_keys in results.items():
for device_id, keys in device_keys.items():
for key_id, json_str in keys.items():
json_result.setdefault(user_id, {})[device_id] = {
key_id: json_decoder.decode(json_str)
}
@trace
async def claim_client_keys(destination: str) -> None:
set_tag("destination", destination)
device_keys = remote_queries[destination]
try:
remote_result = await self.federation.claim_client_keys(
destination, {"one_time_keys": device_keys}, timeout=timeout
)
for user_id, keys in remote_result["one_time_keys"].items():
if user_id in device_keys:
json_result[user_id] = keys
except Exception as e:
failure = _exception_to_failure(e)
failures[destination] = failure
set_tag("error", True)
set_tag("reason", str(failure))
await make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(claim_client_keys, destination)
for destination in remote_queries
],
consumeErrors=True,
)
)
logger.info(
"Claimed one-time-keys: %s",
",".join(
(
"%s for %s:%s" % (key_id, user_id, device_id)
for user_id, user_keys in json_result.items()
for device_id, device_keys in user_keys.items()
for key_id, _ in device_keys.items()
)
),
)
log_kv({"one_time_keys": json_result, "failures": failures})
return {"one_time_keys": json_result, "failures": failures}
@tag_args
async def upload_keys_for_user(
self, user_id: str, device_id: str, keys: JsonDict
) -> JsonDict:
time_now = self.clock.time_msec()
# TODO: Validate the JSON to make sure it has the right keys.
device_keys = keys.get("device_keys", None)
if device_keys:
logger.info(
"Updating device_keys for device %r for user %s at %d",
device_id,
user_id,
time_now,
)
log_kv(
{
"message": "Updating device_keys for user.",
"user_id": user_id,
"device_id": device_id,
}
)
# TODO: Sign the JSON with the server key
changed = await self.store.set_e2e_device_keys(
user_id, device_id, time_now, device_keys
)
if changed:
# Only notify about device updates *if* the keys actually changed
await self.device_handler.notify_device_update(user_id, [device_id])
else:
log_kv({"message": "Not updating device_keys for user", "user_id": user_id})
one_time_keys = keys.get("one_time_keys", None)
if one_time_keys:
log_kv(
{
"message": "Updating one_time_keys for device.",
"user_id": user_id,
"device_id": device_id,
}
)
await self._upload_one_time_keys_for_user(
user_id, device_id, time_now, one_time_keys
)
else:
log_kv(
{"message": "Did not update one_time_keys", "reason": "no keys given"}
)
fallback_keys = keys.get("fallback_keys") or keys.get(
"org.matrix.msc2732.fallback_keys"
)
if fallback_keys and isinstance(fallback_keys, dict):
log_kv(
{
"message": "Updating fallback_keys for device.",
"user_id": user_id,
"device_id": device_id,
}
)
await self.store.set_e2e_fallback_keys(user_id, device_id, fallback_keys)
elif fallback_keys:
log_kv({"message": "Did not update fallback_keys", "reason": "not a dict"})
else:
log_kv(
{"message": "Did not update fallback_keys", "reason": "no keys given"}
)
# the device should have been registered already, but it may have been
# deleted due to a race with a DELETE request. Or we may be using an
# old access_token without an associated device_id. Either way, we
# need to double-check the device is registered to avoid ending up with
# keys without a corresponding device.
await self.device_handler.check_device_registered(user_id, device_id)
result = await self.store.count_e2e_one_time_keys(user_id, device_id)
set_tag("one_time_key_counts", str(result))
return {"one_time_key_counts": result}
async def _upload_one_time_keys_for_user(
self, user_id: str, device_id: str, time_now: int, one_time_keys: JsonDict
) -> None:
logger.info(
"Adding one_time_keys %r for device %r for user %r at %d",
one_time_keys.keys(),
device_id,
user_id,
time_now,
)
# make a list of (alg, id, key) tuples
key_list = []
for key_id, key_obj in one_time_keys.items():
algorithm, key_id = key_id.split(":")
key_list.append((algorithm, key_id, key_obj))
# First we check if we have already persisted any of the keys.
existing_key_map = await self.store.get_e2e_one_time_keys(
user_id, device_id, [k_id for _, k_id, _ in key_list]
)
new_keys = [] # Keys that we need to insert. (alg, id, json) tuples.
for algorithm, key_id, key in key_list:
ex_json = existing_key_map.get((algorithm, key_id), None)
if ex_json:
if not _one_time_keys_match(ex_json, key):
raise SynapseError(
400,
(
"One time key %s:%s already exists. "
"Old key: %s; new key: %r"
)
% (algorithm, key_id, ex_json, key),
)
else:
new_keys.append(
(algorithm, key_id, encode_canonical_json(key).decode("ascii"))
)
log_kv({"message": "Inserting new one_time_keys.", "keys": new_keys})
await self.store.add_e2e_one_time_keys(user_id, device_id, time_now, new_keys)
async def upload_signing_keys_for_user(
self, user_id: str, keys: JsonDict
) -> JsonDict:
"""Upload signing keys for cross-signing
Args:
user_id: the user uploading the keys
keys: the signing keys
"""
# if a master key is uploaded, then check it. Otherwise, load the
# stored master key, to check signatures on other keys
if "master_key" in keys:
master_key = keys["master_key"]
_check_cross_signing_key(master_key, user_id, "master")
else:
master_key = await self.store.get_e2e_cross_signing_key(user_id, "master")
# if there is no master key, then we can't do anything, because all the
# other cross-signing keys need to be signed by the master key
if not master_key:
raise SynapseError(400, "No master key available", Codes.MISSING_PARAM)
try:
master_key_id, master_verify_key = get_verify_key_from_cross_signing_key(
master_key
)
except ValueError:
if "master_key" in keys:
# the invalid key came from the request
raise SynapseError(400, "Invalid master key", Codes.INVALID_PARAM)
else:
# the invalid key came from the database
logger.error("Invalid master key found for user %s", user_id)
raise SynapseError(500, "Invalid master key")
# for the other cross-signing keys, make sure that they have valid
# signatures from the master key
if "self_signing_key" in keys:
self_signing_key = keys["self_signing_key"]
_check_cross_signing_key(
self_signing_key, user_id, "self_signing", master_verify_key
)
if "user_signing_key" in keys:
user_signing_key = keys["user_signing_key"]
_check_cross_signing_key(
user_signing_key, user_id, "user_signing", master_verify_key
)
# if everything checks out, then store the keys and send notifications
deviceids = []
if "master_key" in keys:
await self.store.set_e2e_cross_signing_key(user_id, "master", master_key)
deviceids.append(master_verify_key.version)
if "self_signing_key" in keys:
await self.store.set_e2e_cross_signing_key(
user_id, "self_signing", self_signing_key
)
try:
deviceids.append(
get_verify_key_from_cross_signing_key(self_signing_key)[1].version
)
except ValueError:
raise SynapseError(400, "Invalid self-signing key", Codes.INVALID_PARAM)
if "user_signing_key" in keys:
await self.store.set_e2e_cross_signing_key(
user_id, "user_signing", user_signing_key
)
# the signature stream matches the semantics that we want for
# user-signing key updates: only the user themselves is notified of
# their own user-signing key updates
await self.device_handler.notify_user_signature_update(user_id, [user_id])
# master key and self-signing key updates match the semantics of device
# list updates: all users who share an encrypted room are notified
if len(deviceids):
await self.device_handler.notify_device_update(user_id, deviceids)
return {}
async def upload_signatures_for_device_keys(
self, user_id: str, signatures: JsonDict
) -> JsonDict:
"""Upload device signatures for cross-signing
Args:
user_id: the user uploading the signatures
signatures: map of users to devices to signed keys. This is the submission
from the user; an exception will be raised if it is malformed.
Returns:
The response to be sent back to the client. The response will have
a "failures" key, which will be a dict mapping users to devices
to errors for the signatures that failed.
Raises:
SynapseError: if the signatures dict is not valid.
"""
failures = {}
# signatures to be stored. Each item will be a SignatureListItem
signature_list = []
# split between checking signatures for own user and signatures for
# other users, since we verify them with different keys
self_signatures = signatures.get(user_id, {})
other_signatures = {k: v for k, v in signatures.items() if k != user_id}
self_signature_list, self_failures = await self._process_self_signatures(
user_id, self_signatures
)
signature_list.extend(self_signature_list)
failures.update(self_failures)
other_signature_list, other_failures = await self._process_other_signatures(
user_id, other_signatures
)
signature_list.extend(other_signature_list)
failures.update(other_failures)
# store the signature, and send the appropriate notifications for sync
logger.debug("upload signature failures: %r", failures)
await self.store.store_e2e_cross_signing_signatures(user_id, signature_list)
self_device_ids = [item.target_device_id for item in self_signature_list]
if self_device_ids:
await self.device_handler.notify_device_update(user_id, self_device_ids)
signed_users = [item.target_user_id for item in other_signature_list]
if signed_users:
await self.device_handler.notify_user_signature_update(
user_id, signed_users
)
return {"failures": failures}
async def _process_self_signatures(
self, user_id: str, signatures: JsonDict
) -> Tuple[List["SignatureListItem"], Dict[str, Dict[str, dict]]]:
"""Process uploaded signatures of the user's own keys.
Signatures of the user's own keys from this API come in two forms:
- signatures of the user's devices by the user's self-signing key,
- signatures of the user's master key by the user's devices.
Args:
user_id (string): the user uploading the keys
signatures (dict[string, dict]): map of devices to signed keys
Returns:
A tuple of a list of signatures to store, and a map of users to
devices to failure reasons
Raises:
SynapseError: if the input is malformed
"""
signature_list: List["SignatureListItem"] = []
failures: Dict[str, Dict[str, JsonDict]] = {}
if not signatures:
return signature_list, failures
if not isinstance(signatures, dict):
raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM)
try:
# get our self-signing key to verify the signatures
(
_,
self_signing_key_id,
self_signing_verify_key,
) = await self._get_e2e_cross_signing_verify_key(user_id, "self_signing")
# get our master key, since we may have received a signature of it.
# We need to fetch it here so that we know what its key ID is, so
# that we can check if a signature that was sent is a signature of
# the master key or of a device
(
master_key,
_,
master_verify_key,
) = await self._get_e2e_cross_signing_verify_key(user_id, "master")
# fetch our stored devices. This is used to 1. verify
# signatures on the master key, and 2. to compare with what
# was sent if the device was signed
devices = await self.store.get_e2e_device_keys_for_cs_api([(user_id, None)])
if user_id not in devices:
raise NotFoundError("No device keys found")
devices = devices[user_id]
except SynapseError as e:
failure = _exception_to_failure(e)
failures[user_id] = {device: failure for device in signatures.keys()}
return signature_list, failures
for device_id, device in signatures.items():
# make sure submitted data is in the right form
if not isinstance(device, dict):
raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM)
try:
if "signatures" not in device or user_id not in device["signatures"]:
# no signature was sent
raise SynapseError(
400, "Invalid signature", Codes.INVALID_SIGNATURE
)
if device_id == master_verify_key.version:
# The signature is of the master key. This needs to be
# handled differently from signatures of normal devices.
master_key_signature_list = self._check_master_key_signature(
user_id, device_id, device, master_key, devices
)
signature_list.extend(master_key_signature_list)
continue
# at this point, we have a device that should be signed
# by the self-signing key
if self_signing_key_id not in device["signatures"][user_id]:
# no signature was sent
raise SynapseError(
400, "Invalid signature", Codes.INVALID_SIGNATURE
)
try:
stored_device = devices[device_id]
except KeyError:
raise NotFoundError("Unknown device")
if self_signing_key_id in stored_device.get("signatures", {}).get(
user_id, {}
):
# we already have a signature on this device, so we
# can skip it, since it should be exactly the same
continue
_check_device_signature(
user_id, self_signing_verify_key, device, stored_device
)
signature = device["signatures"][user_id][self_signing_key_id]
signature_list.append(
SignatureListItem(
self_signing_key_id, user_id, device_id, signature
)
)
except SynapseError as e:
failures.setdefault(user_id, {})[device_id] = _exception_to_failure(e)
return signature_list, failures
def _check_master_key_signature(
self,
user_id: str,
master_key_id: str,
signed_master_key: JsonDict,
stored_master_key: JsonDict,
devices: Dict[str, Dict[str, JsonDict]],
) -> List["SignatureListItem"]:
"""Check signatures of a user's master key made by their devices.
Args:
user_id: the user whose master key is being checked
master_key_id: the ID of the user's master key
signed_master_key: the user's signed master key that was uploaded
stored_master_key: our previously-stored copy of the user's master key
devices: the user's devices
Returns:
A list of signatures to store
Raises:
SynapseError: if a signature is invalid
"""
# for each device that signed the master key, check the signature.
master_key_signature_list = []
sigs = signed_master_key["signatures"]
for signing_key_id, signature in sigs[user_id].items():
_, signing_device_id = signing_key_id.split(":", 1)
if (
signing_device_id not in devices
or signing_key_id not in devices[signing_device_id]["keys"]
):
# signed by an unknown device, or the
# device does not have the key
raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE)
# get the key and check the signature
pubkey = devices[signing_device_id]["keys"][signing_key_id]
verify_key = decode_verify_key_bytes(signing_key_id, decode_base64(pubkey))
_check_device_signature(
user_id, verify_key, signed_master_key, stored_master_key
)
master_key_signature_list.append(
SignatureListItem(signing_key_id, user_id, master_key_id, signature)
)
return master_key_signature_list
async def _process_other_signatures(
self, user_id: str, signatures: Dict[str, dict]
) -> Tuple[List["SignatureListItem"], Dict[str, Dict[str, dict]]]:
"""Process uploaded signatures of other users' keys. These will be the
target user's master keys, signed by the uploading user's user-signing
key.
Args:
user_id: the user uploading the keys
signatures: map of users to devices to signed keys
Returns:
A list of signatures to store, and a map of users to devices to failure
reasons
Raises:
SynapseError: if the input is malformed
"""
signature_list: List["SignatureListItem"] = []
failures: Dict[str, Dict[str, JsonDict]] = {}
if not signatures:
return signature_list, failures
try:
# get our user-signing key to verify the signatures
(
user_signing_key,
user_signing_key_id,
user_signing_verify_key,
) = await self._get_e2e_cross_signing_verify_key(user_id, "user_signing")
except SynapseError as e:
failure = _exception_to_failure(e)
for user, devicemap in signatures.items():
failures[user] = {device_id: failure for device_id in devicemap.keys()}
return signature_list, failures
for target_user, devicemap in signatures.items():
# make sure submitted data is in the right form
if not isinstance(devicemap, dict):
raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM)
for device in devicemap.values():
if not isinstance(device, dict):
raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM)
device_id = None
try:
# get the target user's master key, to make sure it matches
# what was sent
(
master_key,
master_key_id,
_,
) = await self._get_e2e_cross_signing_verify_key(
target_user, "master", user_id
)
# make sure that the target user's master key is the one that
# was signed (and no others)
device_id = master_key_id.split(":", 1)[1]
if device_id not in devicemap:
logger.debug(
"upload signature: could not find signature for device %s",
device_id,
)
# set device to None so that the failure gets
# marked on all the signatures
device_id = None
raise NotFoundError("Unknown device")
key = devicemap[device_id]
other_devices = [k for k in devicemap.keys() if k != device_id]
if other_devices:
# other devices were signed -- mark those as failures
logger.debug("upload signature: too many devices specified")
failure = _exception_to_failure(NotFoundError("Unknown device"))
failures[target_user] = {
device: failure for device in other_devices
}
if user_signing_key_id in master_key.get("signatures", {}).get(
user_id, {}
):
# we already have the signature, so we can skip it
continue
_check_device_signature(
user_id, user_signing_verify_key, key, master_key
)
signature = key["signatures"][user_id][user_signing_key_id]
signature_list.append(
SignatureListItem(
user_signing_key_id, target_user, device_id, signature
)
)
except SynapseError as e:
failure = _exception_to_failure(e)
if device_id is None:
failures[target_user] = {
device_id: failure for device_id in devicemap.keys()
}
else:
failures.setdefault(target_user, {})[device_id] = failure
return signature_list, failures
async def _get_e2e_cross_signing_verify_key(
self, user_id: str, key_type: str, from_user_id: Optional[str] = None
) -> Tuple[JsonDict, str, VerifyKey]:
"""Fetch locally or remotely query for a cross-signing public key.
First, attempt to fetch the cross-signing public key from storage.
If that fails, query the keys from the homeserver they belong to
and update our local copy.
Args:
user_id: the user whose key should be fetched
key_type: the type of key to fetch
from_user_id: the user that we are fetching the keys for.
This affects what signatures are fetched.
Returns:
The raw key data, the key ID, and the signedjson verify key
Raises:
NotFoundError: if the key is not found
SynapseError: if `user_id` is invalid
"""
user = UserID.from_string(user_id)
key = await self.store.get_e2e_cross_signing_key(
user_id, key_type, from_user_id
)
if key:
# We found a copy of this key in our database. Decode and return it
key_id, verify_key = get_verify_key_from_cross_signing_key(key)
return key, key_id, verify_key
# If we couldn't find the key locally, and we're looking for keys of
# another user then attempt to fetch the missing key from the remote
# user's server.
#
# We may run into this in possible edge cases where a user tries to
# cross-sign a remote user, but does not share any rooms with them yet.
# Thus, we would not have their key list yet. We instead fetch the key,
# store it and notify clients of new, associated device IDs.
if self.is_mine(user) or key_type not in ["master", "self_signing"]:
# Note that master and self_signing keys are the only cross-signing keys we
# can request over federation
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
cross_signing_keys = await self._retrieve_cross_signing_keys_for_remote_user(
user, key_type
)
if cross_signing_keys is None:
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
return cross_signing_keys
async def _retrieve_cross_signing_keys_for_remote_user(
self,
user: UserID,
desired_key_type: str,
) -> Optional[Tuple[Dict[str, Any], str, VerifyKey]]:
"""Queries cross-signing keys for a remote user and saves them to the database
Only the key specified by `key_type` will be returned, while all retrieved keys
will be saved regardless
Args:
user: The user to query remote keys for
desired_key_type: The type of key to receive. One of "master", "self_signing"
Returns:
A tuple of the retrieved key content, the key's ID and the matching VerifyKey.
If the key cannot be retrieved, all values in the tuple will instead be None.
"""
try:
remote_result = await self.federation.query_user_devices(
user.domain, user.to_string()
)
except Exception as e:
logger.warning(
"Unable to query %s for cross-signing keys of user %s: %s %s",
user.domain,
user.to_string(),
type(e),
e,
)
return None
# Process each of the retrieved cross-signing keys
desired_key_data = None
retrieved_device_ids = []
for key_type in ["master", "self_signing"]:
key_content = remote_result.get(key_type + "_key")
if not key_content:
continue
# Ensure these keys belong to the correct user
if "user_id" not in key_content:
logger.warning(
"Invalid %s key retrieved, missing user_id field: %s",
key_type,
key_content,
)
continue
if user.to_string() != key_content["user_id"]:
logger.warning(
"Found %s key of user %s when querying for keys of user %s",
key_type,
key_content["user_id"],
user.to_string(),
)
continue
# Validate the key contents
try:
# verify_key is a VerifyKey from signedjson, which uses
# .version to denote the portion of the key ID after the
# algorithm and colon, which is the device ID
key_id, verify_key = get_verify_key_from_cross_signing_key(key_content)
except ValueError as e:
logger.warning(
"Invalid %s key retrieved: %s - %s %s",
key_type,
key_content,
type(e),
e,
)
continue
# Note down the device ID attached to this key
retrieved_device_ids.append(verify_key.version)
# If this is the desired key type, save it and its ID/VerifyKey
if key_type == desired_key_type:
desired_key_data = key_content, key_id, verify_key
# At the same time, store this key in the db for subsequent queries
await self.store.set_e2e_cross_signing_key(
user.to_string(), key_type, key_content
)
# Notify clients that new devices for this user have been discovered
if retrieved_device_ids:
# XXX is this necessary?
await self.device_handler.notify_device_update(
user.to_string(), retrieved_device_ids
)
return desired_key_data
def _check_cross_signing_key(
key: JsonDict, user_id: str, key_type: str, signing_key: Optional[VerifyKey] = None
) -> None:
"""Check a cross-signing key uploaded by a user. Performs some basic sanity
checking, and ensures that it is signed, if a signature is required.
Args:
key: the key data to verify
user_id: the user whose key is being checked
key_type: the type of key that the key should be
signing_key: the signing key that the key should be signed with. If
omitted, signatures will not be checked.
"""
if (
key.get("user_id") != user_id
or key_type not in key.get("usage", [])
or len(key.get("keys", {})) != 1
):
raise SynapseError(400, ("Invalid %s key" % (key_type,)), Codes.INVALID_PARAM)
if signing_key:
try:
verify_signed_json(key, user_id, signing_key)
except SignatureVerifyException:
raise SynapseError(
400, ("Invalid signature on %s key" % key_type), Codes.INVALID_SIGNATURE
)
def _check_device_signature(
user_id: str,
verify_key: VerifyKey,
signed_device: JsonDict,
stored_device: JsonDict,
) -> None:
"""Check that a signature on a device or cross-signing key is correct and
matches the copy of the device/key that we have stored. Throws an
exception if an error is detected.
Args:
user_id: the user ID whose signature is being checked
verify_key: the key to verify the device with
signed_device: the uploaded signed device data
stored_device: our previously stored copy of the device
Raises:
SynapseError: if the signature was invalid or the sent device is not the
same as the stored device
"""
# make sure that the device submitted matches what we have stored
stripped_signed_device = {
k: v for k, v in signed_device.items() if k not in ["signatures", "unsigned"]
}
stripped_stored_device = {
k: v for k, v in stored_device.items() if k not in ["signatures", "unsigned"]
}
if stripped_signed_device != stripped_stored_device:
logger.debug(
"upload signatures: key does not match %s vs %s",
signed_device,
stored_device,
)
raise SynapseError(400, "Key does not match")
try:
verify_signed_json(signed_device, user_id, verify_key)
except SignatureVerifyException:
logger.debug("invalid signature on key")
raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE)
def _exception_to_failure(e: Exception) -> JsonDict:
if isinstance(e, SynapseError):
return {"status": e.code, "errcode": e.errcode, "message": str(e)}
if isinstance(e, CodeMessageException):
return {"status": e.code, "message": str(e)}
if isinstance(e, NotRetryingDestination):
return {"status": 503, "message": "Not ready for retry"}
# include ConnectionRefused and other errors
#
# Note that some Exceptions (notably twisted's ResponseFailed etc) don't
# give a string for e.message, which json then fails to serialize.
return {"status": 503, "message": str(e)}
def _one_time_keys_match(old_key_json: str, new_key: JsonDict) -> bool:
old_key = json_decoder.decode(old_key_json)
# if either is a string rather than an object, they must match exactly
if not isinstance(old_key, dict) or not isinstance(new_key, dict):
return old_key == new_key
# otherwise, we strip off the 'signatures' if any, because it's legitimate
# for different upload attempts to have different signatures.
old_key.pop("signatures", None)
new_key_copy = dict(new_key)
new_key_copy.pop("signatures", None)
return old_key == new_key_copy
@attr.s(slots=True, auto_attribs=True)
class SignatureListItem:
"""An item in the signature list as used by upload_signatures_for_device_keys."""
signing_key_id: str
target_user_id: str
target_device_id: str
signature: JsonDict
class SigningKeyEduUpdater:
"""Handles incoming signing key updates from federation and updates the DB"""
def __init__(self, hs: "HomeServer", e2e_keys_handler: E2eKeysHandler):
self.store = hs.get_datastores().main
self.federation = hs.get_federation_client()
self.clock = hs.get_clock()
self.e2e_keys_handler = e2e_keys_handler
self._remote_edu_linearizer = Linearizer(name="remote_signing_key")
# user_id -> list of updates waiting to be handled.
self._pending_updates: Dict[str, List[Tuple[JsonDict, JsonDict]]] = {}
async def incoming_signing_key_update(
self, origin: str, edu_content: JsonDict
) -> None:
"""Called on incoming signing key update from federation. Responsible for
parsing the EDU and adding to pending updates list.
Args:
origin: the server that sent the EDU
edu_content: the contents of the EDU
"""
user_id = edu_content.pop("user_id")
master_key = edu_content.pop("master_key", None)
self_signing_key = edu_content.pop("self_signing_key", None)
if get_domain_from_id(user_id) != origin:
logger.warning("Got signing key update edu for %r from %r", user_id, origin)
return
room_ids = await self.store.get_rooms_for_user(user_id)
if not room_ids:
# We don't share any rooms with this user. Ignore update, as we
# probably won't get any further updates.
return
self._pending_updates.setdefault(user_id, []).append(
(master_key, self_signing_key)
)
await self._handle_signing_key_updates(user_id)
async def _handle_signing_key_updates(self, user_id: str) -> None:
"""Actually handle pending updates.
Args:
user_id: the user whose updates we are processing
"""
device_handler = self.e2e_keys_handler.device_handler
device_list_updater = device_handler.device_list_updater
async with self._remote_edu_linearizer.queue(user_id):
pending_updates = self._pending_updates.pop(user_id, [])
if not pending_updates:
# This can happen since we batch updates
return
device_ids: List[str] = []
logger.info("pending updates: %r", pending_updates)
for master_key, self_signing_key in pending_updates:
new_device_ids = (
await device_list_updater.process_cross_signing_key_update(
user_id,
master_key,
self_signing_key,
)
)
device_ids = device_ids + new_device_ids
await device_handler.notify_device_update(user_id, device_ids)