MatrixSynapse/synapse/crypto/keyring.py

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# -*- coding: utf-8 -*-
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# Copyright 2014, 2015 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from synapse.crypto.keyclient import fetch_server_key
from twisted.internet import defer
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from syutil.crypto.jsonsign import (
verify_signed_json, signature_ids, sign_json, encode_canonical_json
)
from syutil.crypto.signing_key import (
is_signing_algorithm_supported, decode_verify_key_bytes
)
from syutil.base64util import decode_base64, encode_base64
from synapse.api.errors import SynapseError, Codes
from synapse.util.retryutils import get_retry_limiter
from synapse.util.async import ObservableDeferred
from OpenSSL import crypto
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import urllib
import hashlib
import logging
logger = logging.getLogger(__name__)
class Keyring(object):
def __init__(self, hs):
self.store = hs.get_datastore()
self.clock = hs.get_clock()
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self.client = hs.get_http_client()
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self.config = hs.get_config()
self.perspective_servers = self.config.perspectives
self.hs = hs
self.key_downloads = {}
@defer.inlineCallbacks
def verify_json_for_server(self, server_name, json_object):
logger.debug("Verifying for %s", server_name)
key_ids = signature_ids(json_object, server_name)
if not key_ids:
raise SynapseError(
400,
"Not signed with a supported algorithm",
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Codes.UNAUTHORIZED,
)
try:
verify_key = yield self.get_server_verify_key(server_name, key_ids)
except IOError as e:
logger.warn(
"Got IOError when downloading keys for %s: %s %s",
server_name, type(e).__name__, str(e.message),
)
raise SynapseError(
502,
"Error downloading keys for %s" % (server_name,),
Codes.UNAUTHORIZED,
)
except Exception as e:
logger.warn(
"Got Exception when downloading keys for %s: %s %s",
server_name, type(e).__name__, str(e.message),
)
raise SynapseError(
401,
"No key for %s with id %s" % (server_name, key_ids),
Codes.UNAUTHORIZED,
)
try:
verify_signed_json(json_object, server_name, verify_key)
except:
raise SynapseError(
401,
"Invalid signature for server %s with key %s:%s" % (
server_name, verify_key.alg, verify_key.version
),
Codes.UNAUTHORIZED,
)
@defer.inlineCallbacks
def get_server_verify_key(self, server_name, key_ids):
"""Finds a verification key for the server with one of the key ids.
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Trys to fetch the key from a trusted perspective server first.
Args:
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server_name(str): The name of the server to fetch a key for.
keys_ids (list of str): The key_ids to check for.
"""
cached = yield self.store.get_server_verify_keys(server_name, key_ids)
if cached:
defer.returnValue(cached[0])
return
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download = self.key_downloads.get(server_name)
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if download is None:
download = self._get_server_verify_key_impl(server_name, key_ids)
download = ObservableDeferred(
download,
consumeErrors=True
)
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self.key_downloads[server_name] = download
@download.addBoth
def callback(ret):
del self.key_downloads[server_name]
return ret
r = yield download.observe()
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defer.returnValue(r)
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@defer.inlineCallbacks
def _get_server_verify_key_impl(self, server_name, key_ids):
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keys = None
perspective_results = []
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for perspective_name, perspective_keys in self.perspective_servers.items():
@defer.inlineCallbacks
def get_key():
try:
result = yield self.get_server_verify_key_v2_indirect(
server_name, key_ids, perspective_name, perspective_keys
)
defer.returnValue(result)
except:
logging.info(
"Unable to getting key %r for %r from %r",
key_ids, server_name, perspective_name,
)
perspective_results.append(get_key())
perspective_results = yield defer.gatherResults(perspective_results)
for results in perspective_results:
if results is not None:
keys = results
limiter = yield get_retry_limiter(
server_name,
self.clock,
self.store,
)
with limiter:
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if keys is None:
try:
keys = yield self.get_server_verify_key_v2_direct(
server_name, key_ids
)
except:
pass
keys = yield self.get_server_verify_key_v1_direct(
server_name, key_ids
)
for key_id in key_ids:
if key_id in keys:
defer.returnValue(keys[key_id])
return
raise ValueError("No verification key found for given key ids")
@defer.inlineCallbacks
def get_server_verify_key_v2_indirect(self, server_name, key_ids,
perspective_name,
perspective_keys):
limiter = yield get_retry_limiter(
perspective_name, self.clock, self.store
)
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with limiter:
# 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.
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responses = yield self.client.post_json(
destination=perspective_name,
path=b"/_matrix/key/v2/query",
data={
u"server_keys": {
server_name: {
key_id: {
u"minimum_valid_until_ts": 0
} for key_id in key_ids
}
}
},
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)
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keys = {}
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for response in responses:
if (u"signatures" not in response
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or perspective_name not in response[u"signatures"]):
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raise ValueError(
"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 ValueError(
"Response not signed with a known key for perspective"
" server %r" % (perspective_name,)
)
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response_keys = yield self.process_v2_response(
server_name, perspective_name, response
)
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keys.update(response_keys)
yield self.store_keys(
server_name=server_name,
from_server=perspective_name,
verify_keys=keys,
)
defer.returnValue(keys)
@defer.inlineCallbacks
def get_server_verify_key_v2_direct(self, server_name, key_ids):
keys = {}
for requested_key_id in key_ids:
if requested_key_id in keys:
continue
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(response, tls_certificate) = yield fetch_server_key(
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server_name, self.hs.tls_context_factory,
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path=(b"/_matrix/key/v2/server/%s" % (
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urllib.quote(requested_key_id),
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)).encode("ascii"),
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)
if (u"signatures" not in response
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or server_name not in response[u"signatures"]):
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raise ValueError("Key response not signed by remote server")
if "tls_fingerprints" not in response:
raise ValueError("Key response missing TLS fingerprints")
certificate_bytes = crypto.dump_certificate(
crypto.FILETYPE_ASN1, tls_certificate
)
sha256_fingerprint = hashlib.sha256(certificate_bytes).digest()
sha256_fingerprint_b64 = encode_base64(sha256_fingerprint)
response_sha256_fingerprints = set()
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for fingerprint in response[u"tls_fingerprints"]:
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if u"sha256" in fingerprint:
response_sha256_fingerprints.add(fingerprint[u"sha256"])
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if sha256_fingerprint_b64 not in response_sha256_fingerprints:
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raise ValueError("TLS certificate not allowed by fingerprints")
response_keys = yield self.process_v2_response(
server_name=server_name,
from_server=server_name,
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requested_id=requested_key_id,
response_json=response,
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)
keys.update(response_keys)
yield self.store_keys(
server_name=server_name,
from_server=server_name,
verify_keys=keys,
)
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defer.returnValue(keys)
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@defer.inlineCallbacks
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def process_v2_response(self, server_name, from_server, response_json,
requested_id=None):
time_now_ms = self.clock.time_msec()
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response_keys = {}
verify_keys = {}
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for key_id, key_data in response_json["verify_keys"].items():
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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_key.time_added = time_now_ms
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verify_keys[key_id] = verify_key
old_verify_keys = {}
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for key_id, key_data in response_json["old_verify_keys"].items():
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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_key.expired = key_data["expired_ts"]
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verify_key.time_added = time_now_ms
old_verify_keys[key_id] = verify_key
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for key_id in response_json["signatures"][server_name]:
if key_id not in response_json["verify_keys"]:
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raise ValueError(
"Key response must include verification keys for all"
" signatures"
)
if key_id in verify_keys:
verify_signed_json(
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response_json,
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server_name,
verify_keys[key_id]
)
signed_key_json = sign_json(
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response_json,
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self.config.server_name,
self.config.signing_key[0],
)
signed_key_json_bytes = encode_canonical_json(signed_key_json)
ts_valid_until_ms = signed_key_json[u"valid_until_ts"]
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updated_key_ids = set()
if requested_id is not None:
updated_key_ids.add(requested_id)
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updated_key_ids.update(verify_keys)
updated_key_ids.update(old_verify_keys)
response_keys.update(verify_keys)
response_keys.update(old_verify_keys)
for key_id in updated_key_ids:
yield self.store.store_server_keys_json(
server_name=server_name,
key_id=key_id,
from_server=server_name,
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ts_now_ms=time_now_ms,
ts_expires_ms=ts_valid_until_ms,
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key_json_bytes=signed_key_json_bytes,
)
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defer.returnValue(response_keys)
raise ValueError("No verification key found for given key ids")
@defer.inlineCallbacks
def get_server_verify_key_v1_direct(self, server_name, key_ids):
"""Finds a verification key for the server with one of the key ids.
Args:
server_name (str): The name of the server to fetch a key for.
keys_ids (list of str): The key_ids to check for.
"""
# Try to fetch the key from the remote server.
(response, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_context_factory
)
# Check the response.
x509_certificate_bytes = crypto.dump_certificate(
crypto.FILETYPE_ASN1, tls_certificate
)
if ("signatures" not in response
or server_name not in response["signatures"]):
raise ValueError("Key response not signed by remote server")
if "tls_certificate" not in response:
raise ValueError("Key response missing TLS certificate")
tls_certificate_b64 = response["tls_certificate"]
if encode_base64(x509_certificate_bytes) != tls_certificate_b64:
raise ValueError("TLS certificate doesn't match")
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# Cache the result in the datastore.
time_now_ms = self.clock.time_msec()
verify_keys = {}
for key_id, key_base64 in response["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
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verify_key.time_added = time_now_ms
verify_keys[key_id] = verify_key
for key_id in response["signatures"][server_name]:
if key_id not in response["verify_keys"]:
raise ValueError(
"Key response must include verification keys for all"
" signatures"
)
if key_id in verify_keys:
verify_signed_json(
response,
server_name,
verify_keys[key_id]
)
yield self.store.store_server_certificate(
server_name,
server_name,
time_now_ms,
tls_certificate,
)
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yield self.store_keys(
server_name=server_name,
from_server=server_name,
verify_keys=verify_keys,
)
defer.returnValue(verify_keys)
@defer.inlineCallbacks
def store_keys(self, server_name, from_server, verify_keys):
"""Store a collection of verify keys for a given server
Args:
server_name(str): The name of the server the keys are for.
from_server(str): The server the keys were downloaded from.
verify_keys(dict): A mapping of key_id to VerifyKey.
Returns:
A deferred that completes when the keys are stored.
"""
for key_id, key in verify_keys.items():
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# TODO(markjh): Store whether the keys have expired.
yield self.store.store_server_verify_key(
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server_name, server_name, key.time_added, key
)