MatrixSynapse/synapse/handlers/e2e_keys.py

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# Copyright 2016 OpenMarket Ltd
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# Copyright 2018-2019 New Vector Ltd
# Copyright 2019 The Matrix.org Foundation C.I.C.
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#
# 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
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import attr
from canonicaljson import encode_canonical_json
from signedjson.key import VerifyKey, decode_verify_key_bytes
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from signedjson.sign import SignatureVerifyException, verify_signed_json
from unpaddedbase64 import decode_base64
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from twisted.internet import defer
from synapse.api.constants import EduTypes
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from synapse.api.errors import CodeMessageException, Codes, NotFoundError, SynapseError
from synapse.handlers.device import DeviceHandler
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.logging.opentracing import log_kv, set_tag, tag_args, trace
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from synapse.types import (
JsonDict,
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UserID,
get_domain_from_id,
get_verify_key_from_cross_signing_key,
)
from synapse.util import json_decoder
from synapse.util.async_helpers import Linearizer, concurrently_execute
from synapse.util.cancellation import cancellable
from synapse.util.retryutils import NotRetryingDestination
if TYPE_CHECKING:
from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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class E2eKeysHandler:
def __init__(self, hs: "HomeServer"):
self.config = hs.config
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()
federation_registry = hs.get_federation_registry()
is_master = hs.config.worker.worker_app is None
if is_master:
edu_updater = SigningKeyEduUpdater(hs)
# 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,
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,
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
)
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# 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>": {
...
}
}
}
}
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Args:
from_user_id: the user making the query. This is used when
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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, it means there was either a bug in
# device list tracking, or we hit the race mentioned above.
# TODO: In practice, this path is hit fairly often in existing
# deployments when clients query the keys of departed remote
# users. A background update to mark the appropriate device
# lists as unsubscribed is needed.
# https://github.com/matrix-org/synapse/issues/13651
# Note that this currently introduces a failure mode when clients
# are trying to decrypt old messages from a remote user whose
# homeserver is no longer available. We may want to consider falling
# back to the cached data when we fail to retrieve a device list
# over federation for such remote users.
user_ids_not_in_cache.update(invalid_cached_users)
for invalid_user_id in invalid_cached_users:
remote_results.pop(invalid_user_id)
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.
logger.debug(
"%d destinations to query devices for", len(remote_queries_not_in_cache)
)
async def _query(
destination_queries: Tuple[str, Dict[str, Iterable[str]]]
) -> None:
destination, queries = destination_queries
return await self._query_devices_for_destination(
results,
cross_signing_keys,
failures,
destination,
queries,
timeout,
)
await concurrently_execute(
_query,
remote_queries_not_in_cache.items(),
10,
delay_cancellation=True,
)
ret = {"device_keys": results, "failures": failures}
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ret.update(cross_signing_keys)
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return ret
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@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 = []
# Perform a user device resync for each user only once and only as long as:
# - they have an empty device_list
# - they are in some rooms that this server can see
users_to_resync_devices = {
user_id
for (user_id, device_list) in destination_query.items()
if (not device_list) and (await self.store.get_rooms_for_user(user_id))
}
logger.debug(
"%d users to resync devices for from destination %s",
len(users_to_resync_devices),
destination,
)
try:
user_resync_results = (
await self.device_handler.device_list_updater.multi_user_device_resync(
list(users_to_resync_devices)
)
)
for user_id in users_to_resync_devices:
resync_results = user_resync_results[user_id]
if resync_results is None:
# TODO: It's weird that we'll store a failure against a
# destination, yet continue processing users from that
# destination.
# We might want to consider changing this, but for now
# I'm leaving it as I found it.
failures[destination] = _exception_to_failure(
ValueError(f"Device resync failed for {user_id!r}")
)
continue
# 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]]:
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"""Get cross-signing keys for users from the database
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Args:
query: an iterable of user IDs. A dict whose keys
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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
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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
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"""
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]]],
include_displaynames: bool = True,
) -> 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)
include_displaynames: Whether to include device displaynames in the returned
device details.
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)):
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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, include_displaynames
)
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# Build the result structure
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for user_id, device_keys in results.items():
for device_id, device_info in device_keys.items():
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result_dict[user_id][device_id] = device_info
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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:
Handles the path: GET /_matrix/federation/v1/users/keys/query
Args:
query_body: The body of the query request. Should contain a key
"device_keys" that map to a dictionary of user ID's -> list of
device IDs. If the list of device IDs is empty, all devices of
that user will be queried.
Returns:
A json dictionary containing the following:
- device_keys: A dictionary containing the requested device information.
- master_keys: An optional dictionary of user ID -> master cross-signing
key info.
- self_signing_key: An optional dictionary of user ID -> self-signing
key info.
"""
device_keys_query: Dict[str, Optional[List[str]]] = query_body.get(
"device_keys", {}
)
res = await self.query_local_devices(
device_keys_query,
include_displaynames=(
self.config.federation.allow_device_name_lookup_over_federation
),
)
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(
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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(
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defer.gatherResults(
[
run_in_background(claim_client_keys, destination)
for destination in remote_queries
],
consumeErrors=True,
)
)
logger.info(
"Claimed one-time-keys: %s",
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",".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()
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)
),
)
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:
# This can only be called from the main process.
assert isinstance(self.device_handler, DeviceHandler)
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",
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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(
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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(
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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",
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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(":")
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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,
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(
"One time key %s:%s already exists. "
"Old key: %s; new key: %r"
)
% (algorithm, key_id, ex_json, key),
)
else:
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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:
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"""Upload signing keys for cross-signing
Args:
user_id: the user uploading the keys
keys: the signing keys
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"""
# This can only be called from the main process.
assert isinstance(self.device_handler, DeviceHandler)
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# 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")
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# 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)
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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")
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# 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)
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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
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)
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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)
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if "user_signing_key" in keys:
await self.store.set_e2e_cross_signing_key(
user_id, "user_signing", user_signing_key
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)
# 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])
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# 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)
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return {}
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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.
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Returns:
The response to be sent back to the client. The response will have
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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.
"""
# This can only be called from the main process.
assert isinstance(self.device_handler, DeviceHandler)
failures = {}
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# 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
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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)
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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)
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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]]]:
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"""Process uploaded signatures of the user's own keys.
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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.
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Args:
user_id: the user uploading the keys
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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
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Raises:
SynapseError: if the input is malformed
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"""
signature_list: List["SignatureListItem"] = []
failures: Dict[str, Dict[str, JsonDict]] = {}
if not signatures:
return signature_list, failures
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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")
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# 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
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# 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:
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raise NotFoundError("No device keys found")
devices = devices[user_id]
except SynapseError as e:
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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():
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# make sure submitted data is in the right form
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if not isinstance(device, dict):
raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM)
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try:
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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:
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# The signature is of the master key. This needs to be
# handled differently from signatures of normal devices.
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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:
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raise NotFoundError("Unknown device")
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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(
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SignatureListItem(
self_signing_key_id, user_id, device_id, signature
)
)
except SynapseError as e:
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failures.setdefault(user_id, {})[device_id] = _exception_to_failure(e)
return signature_list, failures
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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"]:
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"""Check signatures of a user's master key made by their devices.
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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
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Returns:
A list of signatures to store
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Raises:
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SynapseError: if a signature is invalid
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"""
# 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"]
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):
# 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]
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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]]]:
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"""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.
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Args:
user_id: the user uploading the keys
signatures: map of users to devices to signed keys
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Returns:
A list of signatures to store, and a map of users to devices to failure
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reasons
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Raises:
SynapseError: if the input is malformed
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"""
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():
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failures[user] = {device_id: failure for device_id in devicemap.keys()}
return signature_list, failures
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for target_user, devicemap in signatures.items():
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# make sure submitted data is in the right form
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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)
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device_id = None
try:
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# 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(
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target_user, "master", user_id
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)
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# make sure that the target user's master key is the one that
# was signed (and no others)
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device_id = master_key_id.split(":", 1)[1]
if device_id not in devicemap:
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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
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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
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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
}
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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(
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user_id, user_signing_verify_key, key, master_key
)
signature = key["signatures"][user_id][user_signing_key_id]
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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:
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failures[target_user] = {
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device_id: failure for device_id in devicemap.keys()
}
else:
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failures.setdefault(target_user, {})[device_id] = failure
return signature_list, failures
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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.
2019-09-24 20:12:20 +02:00
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.
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This affects what signatures are fetched.
Returns:
The raw key data, the key ID, and the signedjson verify key
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Raises:
NotFoundError: if the key is not found
SynapseError: if `user_id` is invalid
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"""
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:
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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.
"""
# This can only be called from the main process.
assert isinstance(self.device_handler, DeviceHandler)
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:
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"""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.
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"""
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:
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"""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
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Raises:
SynapseError: if the signature was invalid or the sent device is not the
same as the stored device
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"""
# make sure that the device submitted matches what we have stored
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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:
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logger.debug(
"upload signatures: key does not match %s vs %s",
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signed_device,
stored_device,
)
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raise SynapseError(400, "Key does not match")
try:
verify_signed_json(signed_device, user_id, verify_key)
except SignatureVerifyException:
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logger.debug("invalid signature on key")
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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):
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return {"status": e.code, "message": str(e)}
if isinstance(e, NotRetryingDestination):
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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.
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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
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@attr.s(slots=True, auto_attribs=True)
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class SignatureListItem:
"""An item in the signature list as used by upload_signatures_for_device_keys."""
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signing_key_id: str
target_user_id: str
target_device_id: str
signature: JsonDict
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class SigningKeyEduUpdater:
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"""Handles incoming signing key updates from federation and updates the DB"""
def __init__(self, hs: "HomeServer"):
self.store = hs.get_datastores().main
self.federation = hs.get_federation_client()
self.clock = hs.get_clock()
device_handler = hs.get_device_handler()
assert isinstance(device_handler, DeviceHandler)
self._device_handler = device_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(
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(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
"""
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)
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for master_key, self_signing_key in pending_updates:
new_device_ids = await self._device_handler.device_list_updater.process_cross_signing_key_update(
user_id,
master_key,
self_signing_key,
)
device_ids = device_ids + new_device_ids
await self._device_handler.notify_device_update(user_id, device_ids)