forked-synapse/synapse/crypto/keyring.py
Richard van der Hoff 895b79ac2e Factor out KeyFetchers from KeyRing
Rather than have three methods which have to have the same interface,
factor out a separate interface which is provided by three implementations.

I find it easier to grok the code this way.
2019-05-23 13:46:47 +01:00

771 lines
28 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2017, 2018 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from collections import namedtuple
from six import raise_from
from six.moves import urllib
from signedjson.key import (
decode_verify_key_bytes,
encode_verify_key_base64,
is_signing_algorithm_supported,
)
from signedjson.sign import (
SignatureVerifyException,
encode_canonical_json,
sign_json,
signature_ids,
verify_signed_json,
)
from unpaddedbase64 import decode_base64
from twisted.internet import defer
from synapse.api.errors import (
Codes,
HttpResponseException,
RequestSendFailed,
SynapseError,
)
from synapse.storage.keys import FetchKeyResult
from synapse.util import logcontext, unwrapFirstError
from synapse.util.logcontext import (
LoggingContext,
PreserveLoggingContext,
preserve_fn,
run_in_background,
)
from synapse.util.metrics import Measure
from synapse.util.retryutils import NotRetryingDestination
logger = logging.getLogger(__name__)
VerifyKeyRequest = namedtuple(
"VerifyRequest", ("server_name", "key_ids", "json_object", "deferred")
)
"""
A request for a verify key to verify a JSON object.
Attributes:
server_name(str): The name of the server to verify against.
key_ids(set(str)): The set of key_ids to that could be used to verify the
JSON object
json_object(dict): The JSON object to verify.
deferred(Deferred[str, str, nacl.signing.VerifyKey]):
A deferred (server_name, key_id, verify_key) tuple that resolves when
a verify key has been fetched. The deferreds' callbacks are run with no
logcontext.
"""
class KeyLookupError(ValueError):
pass
class Keyring(object):
def __init__(self, hs):
self.clock = hs.get_clock()
self._key_fetchers = (
StoreKeyFetcher(hs),
PerspectivesKeyFetcher(hs),
ServerKeyFetcher(hs),
)
# map from server name to Deferred. Has an entry for each server with
# an ongoing key download; the Deferred completes once the download
# completes.
#
# These are regular, logcontext-agnostic Deferreds.
self.key_downloads = {}
def verify_json_for_server(self, server_name, json_object):
return logcontext.make_deferred_yieldable(
self.verify_json_objects_for_server([(server_name, json_object)])[0]
)
def verify_json_objects_for_server(self, server_and_json):
"""Bulk verifies signatures of json objects, bulk fetching keys as
necessary.
Args:
server_and_json (list): List of pairs of (server_name, json_object)
Returns:
List<Deferred>: for each input pair, a deferred indicating success
or failure to verify each json object's signature for the given
server_name. The deferreds run their callbacks in the sentinel
logcontext.
"""
# a list of VerifyKeyRequests
verify_requests = []
handle = preserve_fn(_handle_key_deferred)
def process(server_name, json_object):
"""Process an entry in the request list
Given a (server_name, json_object) pair from the request list,
adds a key request to verify_requests, and returns a deferred which will
complete or fail (in the sentinel context) when verification completes.
"""
key_ids = signature_ids(json_object, server_name)
if not key_ids:
return defer.fail(
SynapseError(
400, "Not signed by %s" % (server_name,), Codes.UNAUTHORIZED
)
)
logger.debug("Verifying for %s with key_ids %s", server_name, key_ids)
# add the key request to the queue, but don't start it off yet.
verify_request = VerifyKeyRequest(
server_name, key_ids, json_object, defer.Deferred()
)
verify_requests.append(verify_request)
# now run _handle_key_deferred, which will wait for the key request
# to complete and then do the verification.
#
# We want _handle_key_request to log to the right context, so we
# wrap it with preserve_fn (aka run_in_background)
return handle(verify_request)
results = [
process(server_name, json_object)
for server_name, json_object in server_and_json
]
if verify_requests:
run_in_background(self._start_key_lookups, verify_requests)
return results
@defer.inlineCallbacks
def _start_key_lookups(self, verify_requests):
"""Sets off the key fetches for each verify request
Once each fetch completes, verify_request.deferred will be resolved.
Args:
verify_requests (List[VerifyKeyRequest]):
"""
try:
# create a deferred for each server we're going to look up the keys
# for; we'll resolve them once we have completed our lookups.
# These will be passed into wait_for_previous_lookups to block
# any other lookups until we have finished.
# The deferreds are called with no logcontext.
server_to_deferred = {
rq.server_name: defer.Deferred() for rq in verify_requests
}
# We want to wait for any previous lookups to complete before
# proceeding.
yield self.wait_for_previous_lookups(
[rq.server_name for rq in verify_requests], server_to_deferred
)
# Actually start fetching keys.
self._get_server_verify_keys(verify_requests)
# When we've finished fetching all the keys for a given server_name,
# resolve the deferred passed to `wait_for_previous_lookups` so that
# any lookups waiting will proceed.
#
# map from server name to a set of request ids
server_to_request_ids = {}
for verify_request in verify_requests:
server_name = verify_request.server_name
request_id = id(verify_request)
server_to_request_ids.setdefault(server_name, set()).add(request_id)
def remove_deferreds(res, verify_request):
server_name = verify_request.server_name
request_id = id(verify_request)
server_to_request_ids[server_name].discard(request_id)
if not server_to_request_ids[server_name]:
d = server_to_deferred.pop(server_name, None)
if d:
d.callback(None)
return res
for verify_request in verify_requests:
verify_request.deferred.addBoth(remove_deferreds, verify_request)
except Exception:
logger.exception("Error starting key lookups")
@defer.inlineCallbacks
def wait_for_previous_lookups(self, server_names, server_to_deferred):
"""Waits for any previous key lookups for the given servers to finish.
Args:
server_names (list): list of server_names we want to lookup
server_to_deferred (dict): server_name to deferred which gets
resolved once we've finished looking up keys for that server.
The Deferreds should be regular twisted ones which call their
callbacks with no logcontext.
Returns: a Deferred which resolves once all key lookups for the given
servers have completed. Follows the synapse rules of logcontext
preservation.
"""
loop_count = 1
while True:
wait_on = [
(server_name, self.key_downloads[server_name])
for server_name in server_names
if server_name in self.key_downloads
]
if not wait_on:
break
logger.info(
"Waiting for existing lookups for %s to complete [loop %i]",
[w[0] for w in wait_on],
loop_count,
)
with PreserveLoggingContext():
yield defer.DeferredList((w[1] for w in wait_on))
loop_count += 1
ctx = LoggingContext.current_context()
def rm(r, server_name_):
with PreserveLoggingContext(ctx):
logger.debug("Releasing key lookup lock on %s", server_name_)
self.key_downloads.pop(server_name_, None)
return r
for server_name, deferred in server_to_deferred.items():
logger.debug("Got key lookup lock on %s", server_name)
self.key_downloads[server_name] = deferred
deferred.addBoth(rm, server_name)
def _get_server_verify_keys(self, verify_requests):
"""Tries to find at least one key for each verify request
For each verify_request, verify_request.deferred is called back with
params (server_name, key_id, VerifyKey) if a key is found, or errbacked
with a SynapseError if none of the keys are found.
Args:
verify_requests (list[VerifyKeyRequest]): list of verify requests
"""
@defer.inlineCallbacks
def do_iterations():
with Measure(self.clock, "get_server_verify_keys"):
# dict[str, set(str)]: keys to fetch for each server
missing_keys = {}
for verify_request in verify_requests:
missing_keys.setdefault(verify_request.server_name, set()).update(
verify_request.key_ids
)
for f in self._key_fetchers:
results = yield f.get_keys(missing_keys.items())
# We now need to figure out which verify requests we have keys
# for and which we don't
missing_keys = {}
requests_missing_keys = []
for verify_request in verify_requests:
if verify_request.deferred.called:
# We've already called this deferred, which probably
# means that we've already found a key for it.
continue
server_name = verify_request.server_name
# see if any of the keys we got this time are sufficient to
# complete this VerifyKeyRequest.
result_keys = results.get(server_name, {})
for key_id in verify_request.key_ids:
fetch_key_result = result_keys.get(key_id)
if fetch_key_result:
with PreserveLoggingContext():
verify_request.deferred.callback(
(
server_name,
key_id,
fetch_key_result.verify_key,
)
)
break
else:
# The else block is only reached if the loop above
# doesn't break.
missing_keys.setdefault(server_name, set()).update(
verify_request.key_ids
)
requests_missing_keys.append(verify_request)
if not missing_keys:
break
with PreserveLoggingContext():
for verify_request in requests_missing_keys:
verify_request.deferred.errback(
SynapseError(
401,
"No key for %s with id %s"
% (verify_request.server_name, verify_request.key_ids),
Codes.UNAUTHORIZED,
)
)
def on_err(err):
with PreserveLoggingContext():
for verify_request in verify_requests:
if not verify_request.deferred.called:
verify_request.deferred.errback(err)
run_in_background(do_iterations).addErrback(on_err)
class KeyFetcher(object):
def get_keys(self, server_name_and_key_ids):
"""
Args:
server_name_and_key_ids (iterable[Tuple[str, iterable[str]]]):
list of (server_name, iterable[key_id]) tuples to fetch keys for
Returns:
Deferred[dict[str, dict[str, synapse.storage.keys.FetchKeyResult|None]]]:
map from server_name -> key_id -> FetchKeyResult
"""
raise NotImplementedError
class StoreKeyFetcher(KeyFetcher):
"""KeyFetcher impl which fetches keys from our data store"""
def __init__(self, hs):
self.store = hs.get_datastore()
@defer.inlineCallbacks
def get_keys(self, server_name_and_key_ids):
"""see KeyFetcher.get_keys"""
keys_to_fetch = (
(server_name, key_id)
for server_name, key_ids in server_name_and_key_ids
for key_id in key_ids
)
res = yield self.store.get_server_verify_keys(keys_to_fetch)
keys = {}
for (server_name, key_id), key in res.items():
keys.setdefault(server_name, {})[key_id] = key
defer.returnValue(keys)
class BaseV2KeyFetcher(object):
def __init__(self, hs):
self.store = hs.get_datastore()
self.config = hs.get_config()
@defer.inlineCallbacks
def process_v2_response(
self, from_server, response_json, time_added_ms, requested_ids=[]
):
"""Parse a 'Server Keys' structure from the result of a /key request
This is used to parse either the entirety of the response from
GET /_matrix/key/v2/server, or a single entry from the list returned by
POST /_matrix/key/v2/query.
Checks that each signature in the response that claims to come from the origin
server is valid. (Does not check that there actually is such a signature, for
some reason.)
Stores the json in server_keys_json so that it can be used for future responses
to /_matrix/key/v2/query.
Args:
from_server (str): the name of the server producing this result: either
the origin server for a /_matrix/key/v2/server request, or the notary
for a /_matrix/key/v2/query.
response_json (dict): the json-decoded Server Keys response object
time_added_ms (int): the timestamp to record in server_keys_json
requested_ids (iterable[str]): a list of the key IDs that were requested.
We will store the json for these key ids as well as any that are
actually in the response
Returns:
Deferred[dict[str, FetchKeyResult]]: map from key_id to result object
"""
ts_valid_until_ms = response_json[u"valid_until_ts"]
# start by extracting the keys from the response, since they may be required
# to validate the signature on the response.
verify_keys = {}
for key_id, key_data in response_json["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_base64 = key_data["key"]
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_keys[key_id] = FetchKeyResult(
verify_key=verify_key, valid_until_ts=ts_valid_until_ms
)
# TODO: improve this signature checking
server_name = response_json["server_name"]
for key_id in response_json["signatures"].get(server_name, {}):
if key_id not in verify_keys:
raise KeyLookupError(
"Key response must include verification keys for all signatures"
)
verify_signed_json(
response_json, server_name, verify_keys[key_id].verify_key
)
for key_id, key_data in response_json["old_verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_base64 = key_data["key"]
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_keys[key_id] = FetchKeyResult(
verify_key=verify_key, valid_until_ts=key_data["expired_ts"]
)
# re-sign the json with our own key, so that it is ready if we are asked to
# give it out as a notary server
signed_key_json = sign_json(
response_json, self.config.server_name, self.config.signing_key[0]
)
signed_key_json_bytes = encode_canonical_json(signed_key_json)
# for reasons I don't quite understand, we store this json for the key ids we
# requested, as well as those we got.
updated_key_ids = set(requested_ids)
updated_key_ids.update(verify_keys)
yield logcontext.make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(
self.store.store_server_keys_json,
server_name=server_name,
key_id=key_id,
from_server=from_server,
ts_now_ms=time_added_ms,
ts_expires_ms=ts_valid_until_ms,
key_json_bytes=signed_key_json_bytes,
)
for key_id in updated_key_ids
],
consumeErrors=True,
).addErrback(unwrapFirstError)
)
defer.returnValue(verify_keys)
class PerspectivesKeyFetcher(BaseV2KeyFetcher):
"""KeyFetcher impl which fetches keys from the "perspectives" servers"""
def __init__(self, hs):
super(PerspectivesKeyFetcher, self).__init__(hs)
self.clock = hs.get_clock()
self.client = hs.get_http_client()
self.perspective_servers = self.config.perspectives
@defer.inlineCallbacks
def get_keys(self, server_name_and_key_ids):
"""see KeyFetcher.get_keys"""
@defer.inlineCallbacks
def get_key(perspective_name, perspective_keys):
try:
result = yield self.get_server_verify_key_v2_indirect(
server_name_and_key_ids, perspective_name, perspective_keys
)
defer.returnValue(result)
except KeyLookupError as e:
logger.warning("Key lookup failed from %r: %s", perspective_name, e)
except Exception as e:
logger.exception(
"Unable to get key from %r: %s %s",
perspective_name,
type(e).__name__,
str(e),
)
defer.returnValue({})
results = yield logcontext.make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(get_key, p_name, p_keys)
for p_name, p_keys in self.perspective_servers.items()
],
consumeErrors=True,
).addErrback(unwrapFirstError)
)
union_of_keys = {}
for result in results:
for server_name, keys in result.items():
union_of_keys.setdefault(server_name, {}).update(keys)
defer.returnValue(union_of_keys)
@defer.inlineCallbacks
def get_server_verify_key_v2_indirect(
self, server_names_and_key_ids, perspective_name, perspective_keys
):
"""
Args:
server_names_and_key_ids (iterable[Tuple[str, iterable[str]]]):
list of (server_name, iterable[key_id]) tuples to fetch keys for
perspective_name (str): name of the notary server to query for the keys
perspective_keys (dict[str, VerifyKey]): map of key_id->key for the
notary server
Returns:
Deferred[dict[str, dict[str, synapse.storage.keys.FetchKeyResult]]]: map
from server_name -> key_id -> FetchKeyResult
"""
# TODO(mark): Set the minimum_valid_until_ts to that needed by
# the events being validated or the current time if validating
# an incoming request.
try:
query_response = yield self.client.post_json(
destination=perspective_name,
path="/_matrix/key/v2/query",
data={
u"server_keys": {
server_name: {
key_id: {u"minimum_valid_until_ts": 0} for key_id in key_ids
}
for server_name, key_ids in server_names_and_key_ids
}
},
long_retries=True,
)
except (NotRetryingDestination, RequestSendFailed) as e:
raise_from(KeyLookupError("Failed to connect to remote server"), e)
except HttpResponseException as e:
raise_from(KeyLookupError("Remote server returned an error"), e)
keys = {}
added_keys = []
time_now_ms = self.clock.time_msec()
for response in query_response["server_keys"]:
if (
u"signatures" not in response
or perspective_name not in response[u"signatures"]
):
raise KeyLookupError(
"Key response not signed by perspective server"
" %r" % (perspective_name,)
)
verified = False
for key_id in response[u"signatures"][perspective_name]:
if key_id in perspective_keys:
verify_signed_json(
response, perspective_name, perspective_keys[key_id]
)
verified = True
if not verified:
logging.info(
"Response from perspective server %r not signed with a"
" known key, signed with: %r, known keys: %r",
perspective_name,
list(response[u"signatures"][perspective_name]),
list(perspective_keys),
)
raise KeyLookupError(
"Response not signed with a known key for perspective"
" server %r" % (perspective_name,)
)
processed_response = yield self.process_v2_response(
perspective_name, response, time_added_ms=time_now_ms
)
server_name = response["server_name"]
added_keys.extend(
(server_name, key_id, key) for key_id, key in processed_response.items()
)
keys.setdefault(server_name, {}).update(processed_response)
yield self.store.store_server_verify_keys(
perspective_name, time_now_ms, added_keys
)
defer.returnValue(keys)
class ServerKeyFetcher(BaseV2KeyFetcher):
"""KeyFetcher impl which fetches keys from the origin servers"""
def __init__(self, hs):
super(ServerKeyFetcher, self).__init__(hs)
self.clock = hs.get_clock()
self.client = hs.get_http_client()
@defer.inlineCallbacks
def get_keys(self, server_name_and_key_ids):
"""see KeyFetcher.get_keys"""
results = yield logcontext.make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(
self.get_server_verify_key_v2_direct, server_name, key_ids
)
for server_name, key_ids in server_name_and_key_ids
],
consumeErrors=True,
).addErrback(unwrapFirstError)
)
merged = {}
for result in results:
merged.update(result)
defer.returnValue(
{server_name: keys for server_name, keys in merged.items() if keys}
)
@defer.inlineCallbacks
def get_server_verify_key_v2_direct(self, server_name, key_ids):
keys = {} # type: dict[str, FetchKeyResult]
for requested_key_id in key_ids:
if requested_key_id in keys:
continue
time_now_ms = self.clock.time_msec()
try:
response = yield self.client.get_json(
destination=server_name,
path="/_matrix/key/v2/server/"
+ urllib.parse.quote(requested_key_id),
ignore_backoff=True,
)
except (NotRetryingDestination, RequestSendFailed) as e:
raise_from(KeyLookupError("Failed to connect to remote server"), e)
except HttpResponseException as e:
raise_from(KeyLookupError("Remote server returned an error"), e)
if (
u"signatures" not in response
or server_name not in response[u"signatures"]
):
raise KeyLookupError("Key response not signed by remote server")
if response["server_name"] != server_name:
raise KeyLookupError(
"Expected a response for server %r not %r"
% (server_name, response["server_name"])
)
response_keys = yield self.process_v2_response(
from_server=server_name,
requested_ids=[requested_key_id],
response_json=response,
time_added_ms=time_now_ms,
)
yield self.store.store_server_verify_keys(
server_name,
time_now_ms,
((server_name, key_id, key) for key_id, key in response_keys.items()),
)
keys.update(response_keys)
defer.returnValue({server_name: keys})
@defer.inlineCallbacks
def _handle_key_deferred(verify_request):
"""Waits for the key to become available, and then performs a verification
Args:
verify_request (VerifyKeyRequest):
Returns:
Deferred[None]
Raises:
SynapseError if there was a problem performing the verification
"""
server_name = verify_request.server_name
try:
with PreserveLoggingContext():
_, key_id, verify_key = yield verify_request.deferred
except KeyLookupError as e:
logger.warn(
"Failed to download keys for %s: %s %s",
server_name,
type(e).__name__,
str(e),
)
raise SynapseError(
502, "Error downloading keys for %s" % (server_name,), Codes.UNAUTHORIZED
)
except Exception as e:
logger.exception(
"Got Exception when downloading keys for %s: %s %s",
server_name,
type(e).__name__,
str(e),
)
raise SynapseError(
401,
"No key for %s with id %s" % (server_name, verify_request.key_ids),
Codes.UNAUTHORIZED,
)
json_object = verify_request.json_object
logger.debug(
"Got key %s %s:%s for server %s, verifying"
% (key_id, verify_key.alg, verify_key.version, server_name)
)
try:
verify_signed_json(json_object, server_name, verify_key)
except SignatureVerifyException as e:
logger.debug(
"Error verifying signature for %s:%s:%s with key %s: %s",
server_name,
verify_key.alg,
verify_key.version,
encode_verify_key_base64(verify_key),
str(e),
)
raise SynapseError(
401,
"Invalid signature for server %s with key %s:%s: %s"
% (server_name, verify_key.alg, verify_key.version, str(e)),
Codes.UNAUTHORIZED,
)