anonymousland-synapse/synapse/handlers/e2e_keys.py
Brendan Abolivier 33c39ab93c
Process cross-signing keys when resyncing device lists (#7594)
It looks like `user_device_resync` was ignoring cross-signing keys from the results received from the remote server. This patch fixes this, by processing these keys using the same process `_handle_signing_key_updates` does (and effectively factor that part out of that function).
2020-06-01 17:47:30 +02:00

1313 lines
51 KiB
Python

# -*- coding: utf-8 -*-
# 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 six import iteritems
import attr
from canonicaljson import encode_canonical_json, json
from signedjson.key import 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.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 (
UserID,
get_domain_from_id,
get_verify_key_from_cross_signing_key,
)
from synapse.util import unwrapFirstError
from synapse.util.async_helpers import Linearizer
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.util.retryutils import NotRetryingDestination
logger = logging.getLogger(__name__)
class E2eKeysHandler(object):
def __init__(self, hs):
self.store = hs.get_datastore()
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_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
#
# FIXME: switch to m.signing_key_update when MSC1756 is merged into the spec
federation_registry.register_edu_handler(
"org.matrix.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
)
@trace
@defer.inlineCallbacks
def query_devices(self, query_body, timeout, from_user_id):
""" Handle a device key query from a client
{
"device_keys": {
"<user_id>": ["<device_id>"]
}
}
->
{
"device_keys": {
"<user_id>": {
"<device_id>": {
...
}
}
}
}
Args:
from_user_id (str): the user making the query. This is used when
adding cross-signing signatures to limit what signatures users
can see.
"""
device_keys_query = 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", local_query)
set_tag("remote_key_query", remote_queries)
# First get local devices.
failures = {}
results = {}
if local_query:
local_result = yield self.query_local_devices(local_query)
for user_id, keys in local_result.items():
if user_id in local_query:
results[user_id] = keys
# Now attempt to get any remote devices from our local cache.
remote_queries_not_in_cache = {}
if remote_queries:
query_list = []
for user_id, device_ids in iteritems(remote_queries):
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,
) = yield self.store.get_user_devices_from_cache(query_list)
for user_id, devices in iteritems(remote_results):
user_devices = results.setdefault(user_id, {})
for device_id, device in iteritems(devices):
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
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]
# Get cached cross-signing keys
cross_signing_keys = yield self.get_cross_signing_keys_from_cache(
device_keys_query, from_user_id
)
# Now fetch any devices that we don't have in our cache
@trace
@defer.inlineCallbacks
def do_remote_query(destination):
"""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.
"""
destination_query = remote_queries_not_in_cache[destination]
# 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 = yield 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:
user_devices = yield self.device_handler.device_list_updater.user_device_resync(
user_id
)
else:
user_devices = yield self._user_device_resync_client(
user_id=user_id
)
user_devices = user_devices["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)
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 = yield 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", failure)
yield make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(do_remote_query, destination)
for destination in remote_queries_not_in_cache
],
consumeErrors=True,
).addErrback(unwrapFirstError)
)
ret = {"device_keys": results, "failures": failures}
ret.update(cross_signing_keys)
return ret
@defer.inlineCallbacks
def get_cross_signing_keys_from_cache(self, query, from_user_id):
"""Get cross-signing keys for users from the database
Args:
query (Iterable[string]) 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 (str): the user making the query. This is used when
adding cross-signing signatures to limit what signatures users
can see.
Returns:
defer.Deferred[dict[str, dict[str, dict]]]: 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 = yield 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"]
if (
from_user_id in keys
and keys[from_user_id] is not None
and "user_signing" in keys[from_user_id]
):
# users can see other users' master and self-signing keys, but can
# only see their own user-signing keys
user_signing_keys[from_user_id] = keys[from_user_id]["user_signing"]
return {
"master_keys": master_keys,
"self_signing_keys": self_signing_keys,
"user_signing_keys": user_signing_keys,
}
@trace
@defer.inlineCallbacks
def query_local_devices(self, query):
"""Get E2E device keys for local users
Args:
query (dict[string, list[string]|None): map from user_id to a list
of devices to query (None for all devices)
Returns:
defer.Deferred: (resolves to dict[string, dict[string, dict]]):
map from user_id -> device_id -> device details
"""
set_tag("local_query", query)
local_query = []
result_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 = yield self.store.get_e2e_device_keys(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
@defer.inlineCallbacks
def on_federation_query_client_keys(self, query_body):
""" Handle a device key query from a federated server
"""
device_keys_query = query_body.get("device_keys", {})
res = yield self.query_local_devices(device_keys_query)
ret = {"device_keys": res}
# add in the cross-signing keys
cross_signing_keys = yield self.get_cross_signing_keys_from_cache(
device_keys_query, None
)
ret.update(cross_signing_keys)
return ret
@trace
@defer.inlineCallbacks
def claim_one_time_keys(self, query, timeout):
local_query = []
remote_queries = {}
for user_id, device_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 device_keys.items():
local_query.append((user_id, device_id, algorithm))
else:
domain = get_domain_from_id(user_id)
remote_queries.setdefault(domain, {})[user_id] = device_keys
set_tag("local_key_query", local_query)
set_tag("remote_key_query", remote_queries)
results = yield self.store.claim_e2e_one_time_keys(local_query)
json_result = {}
failures = {}
for user_id, device_keys in results.items():
for device_id, keys in device_keys.items():
for key_id, json_bytes in keys.items():
json_result.setdefault(user_id, {})[device_id] = {
key_id: json.loads(json_bytes)
}
@trace
@defer.inlineCallbacks
def claim_client_keys(destination):
set_tag("destination", destination)
device_keys = remote_queries[destination]
try:
remote_result = yield 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", failure)
yield 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 iteritems(json_result)
for device_id, device_keys in iteritems(user_keys)
for key_id, _ in iteritems(device_keys)
)
),
)
log_kv({"one_time_keys": json_result, "failures": failures})
return {"one_time_keys": json_result, "failures": failures}
@defer.inlineCallbacks
@tag_args
def upload_keys_for_user(self, user_id, device_id, keys):
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 = yield 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
yield 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,
}
)
yield 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"}
)
# 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.
yield self.device_handler.check_device_registered(user_id, device_id)
result = yield self.store.count_e2e_one_time_keys(user_id, device_id)
set_tag("one_time_key_counts", result)
return {"one_time_key_counts": result}
@defer.inlineCallbacks
def _upload_one_time_keys_for_user(
self, user_id, device_id, time_now, one_time_keys
):
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 = yield 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})
yield self.store.add_e2e_one_time_keys(user_id, device_id, time_now, new_keys)
@defer.inlineCallbacks
def upload_signing_keys_for_user(self, user_id, keys):
"""Upload signing keys for cross-signing
Args:
user_id (string): the user uploading the keys
keys (dict[string, dict]): 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 = yield 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:
yield self.store.set_e2e_cross_signing_key(user_id, "master", master_key)
deviceids.append(master_verify_key.version)
if "self_signing_key" in keys:
yield 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:
yield 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
yield 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):
yield self.device_handler.notify_device_update(user_id, deviceids)
return {}
@defer.inlineCallbacks
def upload_signatures_for_device_keys(self, user_id, signatures):
"""Upload device signatures for cross-signing
Args:
user_id (string): the user uploading the signatures
signatures (dict[string, dict[string, dict]]): 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:
dict: 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 = yield self._process_self_signatures(
user_id, self_signatures
)
signature_list.extend(self_signature_list)
failures.update(self_failures)
other_signature_list, other_failures = yield 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)
yield 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:
yield 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:
yield self.device_handler.notify_user_signature_update(
user_id, signed_users
)
return {"failures": failures}
@defer.inlineCallbacks
def _process_self_signatures(self, user_id, signatures):
"""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:
(list[SignatureListItem], dict[string, dict[string, dict]]):
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 = []
failures = {}
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,
) = yield 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,
) = yield 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 = yield self.store.get_e2e_device_keys([(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, master_key_id, signed_master_key, stored_master_key, devices
):
"""Check signatures of a user's master key made by their devices.
Args:
user_id (string): the user whose master key is being checked
master_key_id (string): the ID of the user's master key
signed_master_key (dict): the user's signed master key that was uploaded
stored_master_key (dict): our previously-stored copy of the user's master key
devices (iterable(dict)): the user's devices
Returns:
list[SignatureListItem]: 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
@defer.inlineCallbacks
def _process_other_signatures(self, user_id, signatures):
"""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 (string): the user uploading the keys
signatures (dict[string, dict]): map of users to devices to signed keys
Returns:
(list[SignatureListItem], dict[string, dict[string, dict]]):
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 = []
failures = {}
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,
) = yield 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,
_,
) = yield 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
@defer.inlineCallbacks
def _get_e2e_cross_signing_verify_key(
self, user_id: str, key_type: str, from_user_id: str = None
):
"""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:
dict, str, VerifyKey: 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 = yield 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))
(
key,
key_id,
verify_key,
) = yield self._retrieve_cross_signing_keys_for_remote_user(user, key_type)
if key is None:
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
return key, key_id, verify_key
@defer.inlineCallbacks
def _retrieve_cross_signing_keys_for_remote_user(
self, user: UserID, desired_key_type: str,
):
"""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:
Deferred[Tuple[Optional[Dict], Optional[str], Optional[VerifyKey]]]: 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 = yield 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, None, None
# Process each of the retrieved cross-signing keys
desired_key = None
desired_key_id = None
desired_verify_key = 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 = key_content
desired_verify_key = verify_key
desired_key_id = key_id
# At the same time, store this key in the db for subsequent queries
yield 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?
yield self.device_handler.notify_device_update(
user.to_string(), retrieved_device_ids
)
return desired_key, desired_key_id, desired_verify_key
def _check_cross_signing_key(key, user_id, key_type, signing_key=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 (dict): the key data to verify
user_id (str): the user whose key is being checked
key_type (str): the type of key that the key should be
signing_key (VerifyKey): (optional) 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, verify_key, signed_device, stored_device):
"""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 (str): the user ID whose signature is being checked
verify_key (VerifyKey): the key to verify the device with
signed_device (dict): the uploaded signed device data
stored_device (dict): 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):
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, new_key):
old_key = json.loads(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
class SignatureListItem:
"""An item in the signature list as used by upload_signatures_for_device_keys.
"""
signing_key_id = attr.ib()
target_user_id = attr.ib()
target_device_id = attr.ib()
signature = attr.ib()
class SigningKeyEduUpdater(object):
"""Handles incoming signing key updates from federation and updates the DB"""
def __init__(self, hs, e2e_keys_handler):
self.store = hs.get_datastore()
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 = {}
# Recently seen stream ids. We don't bother keeping these in the DB,
# but they're useful to have them about to reduce the number of spurious
# resyncs.
self._seen_updates = ExpiringCache(
cache_name="signing_key_update_edu",
clock=self.clock,
max_len=10000,
expiry_ms=30 * 60 * 1000,
iterable=True,
)
@defer.inlineCallbacks
def incoming_signing_key_update(self, origin, edu_content):
"""Called on incoming signing key update from federation. Responsible for
parsing the EDU and adding to pending updates list.
Args:
origin (string): the server that sent the EDU
edu_content (dict): 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 = yield 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)
)
yield self._handle_signing_key_updates(user_id)
@defer.inlineCallbacks
def _handle_signing_key_updates(self, user_id):
"""Actually handle pending updates.
Args:
user_id (string): the user whose updates we are processing
"""
device_handler = self.e2e_keys_handler.device_handler
device_list_updater = device_handler.device_list_updater
with (yield 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 = []
logger.info("pending updates: %r", pending_updates)
for master_key, self_signing_key in pending_updates:
new_device_ids = yield device_list_updater.process_cross_signing_key_update(
user_id, master_key, self_signing_key,
)
device_ids = device_ids + new_device_ids
yield device_handler.notify_device_update(user_id, device_ids)