MatrixSynapse/synapse/crypto/keyring.py

694 lines
24 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2014-2016 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 synapse.api.errors import SynapseError, Codes
from synapse.util.retryutils import get_retry_limiter
from synapse.util import unwrapFirstError
from synapse.util.async import ObservableDeferred
from synapse.util.logcontext import (
preserve_context_over_deferred, preserve_context_over_fn, PreserveLoggingContext,
preserve_fn
)
from twisted.internet import defer
from signedjson.sign import (
verify_signed_json, signature_ids, sign_json, encode_canonical_json
)
from signedjson.key import (
is_signing_algorithm_supported, decode_verify_key_bytes
)
from unpaddedbase64 import decode_base64, encode_base64
from OpenSSL import crypto
from collections import namedtuple
import urllib
import hashlib
import logging
logger = logging.getLogger(__name__)
KeyGroup = namedtuple("KeyGroup", ("server_name", "group_id", "key_ids"))
class Keyring(object):
def __init__(self, hs):
self.store = hs.get_datastore()
self.clock = hs.get_clock()
self.client = hs.get_http_client()
self.config = hs.get_config()
self.perspective_servers = self.config.perspectives
self.hs = hs
self.key_downloads = {}
def verify_json_for_server(self, server_name, json_object):
return self.verify_json_objects_for_server(
[(server_name, json_object)]
)[0]
def verify_json_objects_for_server(self, server_and_json):
"""Bulk verfies signatures of json objects, bulk fetching keys as
necessary.
Args:
server_and_json (list): List of pairs of (server_name, json_object)
Returns:
list of deferreds indicating success or failure to verify each
json object's signature for the given server_name.
"""
group_id_to_json = {}
group_id_to_group = {}
group_ids = []
next_group_id = 0
deferreds = {}
for server_name, json_object in server_and_json:
logger.debug("Verifying for %s", server_name)
group_id = next_group_id
next_group_id += 1
group_ids.append(group_id)
key_ids = signature_ids(json_object, server_name)
if not key_ids:
deferreds[group_id] = defer.fail(SynapseError(
400,
"Not signed with a supported algorithm",
Codes.UNAUTHORIZED,
))
else:
deferreds[group_id] = defer.Deferred()
group = KeyGroup(server_name, group_id, key_ids)
group_id_to_group[group_id] = group
group_id_to_json[group_id] = json_object
@defer.inlineCallbacks
def handle_key_deferred(group, deferred):
server_name = group.server_name
try:
_, _, key_id, verify_key = yield deferred
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.exception(
"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,
)
json_object = group_id_to_json[group.group_id]
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,
)
server_to_deferred = {
server_name: defer.Deferred()
for server_name, _ in server_and_json
}
with PreserveLoggingContext():
# We want to wait for any previous lookups to complete before
# proceeding.
wait_on_deferred = self.wait_for_previous_lookups(
[server_name for server_name, _ in server_and_json],
server_to_deferred,
)
# Actually start fetching keys.
wait_on_deferred.addBoth(
lambda _: self.get_server_verify_keys(group_id_to_group, deferreds)
)
# 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.
server_to_gids = {}
def remove_deferreds(res, server_name, group_id):
server_to_gids[server_name].discard(group_id)
if not server_to_gids[server_name]:
d = server_to_deferred.pop(server_name, None)
if d:
d.callback(None)
return res
for g_id, deferred in deferreds.items():
server_name = group_id_to_group[g_id].server_name
server_to_gids.setdefault(server_name, set()).add(g_id)
deferred.addBoth(remove_deferreds, server_name, g_id)
# Pass those keys to handle_key_deferred so that the json object
# signatures can be verified
return [
preserve_context_over_fn(
handle_key_deferred,
group_id_to_group[g_id],
deferreds[g_id],
)
for g_id in group_ids
]
@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
"""
while True:
wait_on = [
self.key_downloads[server_name]
for server_name in server_names
if server_name in self.key_downloads
]
if wait_on:
with PreserveLoggingContext():
yield defer.DeferredList(wait_on)
else:
break
for server_name, deferred in server_to_deferred.items():
d = ObservableDeferred(preserve_context_over_deferred(deferred))
self.key_downloads[server_name] = d
def rm(r, server_name):
self.key_downloads.pop(server_name, None)
return r
d.addBoth(rm, server_name)
def get_server_verify_keys(self, group_id_to_group, group_id_to_deferred):
"""Takes a dict of KeyGroups and tries to find at least one key for
each group.
"""
# These are functions that produce keys given a list of key ids
key_fetch_fns = (
self.get_keys_from_store, # First try the local store
self.get_keys_from_perspectives, # Then try via perspectives
self.get_keys_from_server, # Then try directly
)
@defer.inlineCallbacks
def do_iterations():
merged_results = {}
missing_keys = {}
for group in group_id_to_group.values():
missing_keys.setdefault(group.server_name, set()).update(
group.key_ids
)
for fn in key_fetch_fns:
results = yield fn(missing_keys.items())
merged_results.update(results)
# We now need to figure out which groups we have keys for
# and which we don't
missing_groups = {}
for group in group_id_to_group.values():
for key_id in group.key_ids:
if key_id in merged_results[group.server_name]:
with PreserveLoggingContext():
group_id_to_deferred[group.group_id].callback((
group.group_id,
group.server_name,
key_id,
merged_results[group.server_name][key_id],
))
break
else:
missing_groups.setdefault(
group.server_name, []
).append(group)
if not missing_groups:
break
missing_keys = {
server_name: set(
key_id for group in groups for key_id in group.key_ids
)
for server_name, groups in missing_groups.items()
}
for group in missing_groups.values():
group_id_to_deferred[group.group_id].errback(SynapseError(
401,
"No key for %s with id %s" % (
group.server_name, group.key_ids,
),
Codes.UNAUTHORIZED,
))
def on_err(err):
for deferred in group_id_to_deferred.values():
if not deferred.called:
deferred.errback(err)
do_iterations().addErrback(on_err)
return group_id_to_deferred
@defer.inlineCallbacks
def get_keys_from_store(self, server_name_and_key_ids):
res = yield defer.gatherResults(
[
self.store.get_server_verify_keys(
server_name, key_ids
).addCallback(lambda ks, server: (server, ks), server_name)
for server_name, key_ids in server_name_and_key_ids
],
consumeErrors=True,
).addErrback(unwrapFirstError)
defer.returnValue(dict(res))
@defer.inlineCallbacks
def get_keys_from_perspectives(self, server_name_and_key_ids):
@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 Exception as e:
logger.exception(
"Unable to get key from %r: %s %s",
perspective_name,
type(e).__name__, str(e.message),
)
defer.returnValue({})
results = yield defer.gatherResults(
[
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_keys_from_server(self, server_name_and_key_ids):
@defer.inlineCallbacks
def get_key(server_name, key_ids):
limiter = yield get_retry_limiter(
server_name,
self.clock,
self.store,
)
with limiter:
keys = None
try:
keys = yield self.get_server_verify_key_v2_direct(
server_name, key_ids
)
except Exception as e:
logger.info(
"Unable to getting key %r for %r directly: %s %s",
key_ids, server_name,
type(e).__name__, str(e.message),
)
if not keys:
keys = yield self.get_server_verify_key_v1_direct(
server_name, key_ids
)
keys = {server_name: keys}
defer.returnValue(keys)
results = yield defer.gatherResults(
[
get_key(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_indirect(self, server_names_and_key_ids,
perspective_name,
perspective_keys):
# 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.
query_response = 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
}
for server_name, key_ids in server_names_and_key_ids
}
},
long_retries=True,
)
keys = {}
responses = query_response["server_keys"]
for response in responses:
if (u"signatures" not in response
or perspective_name not in response[u"signatures"]):
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,)
)
processed_response = yield self.process_v2_response(
perspective_name, response
)
for server_name, response_keys in processed_response.items():
keys.setdefault(server_name, {}).update(response_keys)
yield defer.gatherResults(
[
self.store_keys(
server_name=server_name,
from_server=perspective_name,
verify_keys=response_keys,
)
for server_name, response_keys in keys.items()
],
consumeErrors=True
).addErrback(unwrapFirstError)
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
(response, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_server_context_factory,
path=(b"/_matrix/key/v2/server/%s" % (
urllib.quote(requested_key_id),
)).encode("ascii"),
)
if (u"signatures" not in response
or server_name not in response[u"signatures"]):
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()
for fingerprint in response[u"tls_fingerprints"]:
if u"sha256" in fingerprint:
response_sha256_fingerprints.add(fingerprint[u"sha256"])
if sha256_fingerprint_b64 not in response_sha256_fingerprints:
raise ValueError("TLS certificate not allowed by fingerprints")
response_keys = yield self.process_v2_response(
from_server=server_name,
requested_ids=[requested_key_id],
response_json=response,
)
keys.update(response_keys)
yield defer.gatherResults(
[
preserve_fn(self.store_keys)(
server_name=key_server_name,
from_server=server_name,
verify_keys=verify_keys,
)
for key_server_name, verify_keys in keys.items()
],
consumeErrors=True
).addErrback(unwrapFirstError)
defer.returnValue(keys)
@defer.inlineCallbacks
def process_v2_response(self, from_server, response_json,
requested_ids=[]):
time_now_ms = self.clock.time_msec()
response_keys = {}
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_key.time_added = time_now_ms
verify_keys[key_id] = verify_key
old_verify_keys = {}
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_key.expired = key_data["expired_ts"]
verify_key.time_added = time_now_ms
old_verify_keys[key_id] = verify_key
results = {}
server_name = response_json["server_name"]
for key_id in response_json["signatures"].get(server_name, {}):
if key_id not in response_json["verify_keys"]:
raise ValueError(
"Key response must include verification keys for all"
" signatures"
)
if key_id in verify_keys:
verify_signed_json(
response_json,
server_name,
verify_keys[key_id]
)
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)
ts_valid_until_ms = signed_key_json[u"valid_until_ts"]
updated_key_ids = set(requested_ids)
updated_key_ids.update(verify_keys)
updated_key_ids.update(old_verify_keys)
response_keys.update(verify_keys)
response_keys.update(old_verify_keys)
yield defer.gatherResults(
[
preserve_fn(self.store.store_server_keys_json)(
server_name=server_name,
key_id=key_id,
from_server=server_name,
ts_now_ms=time_now_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)
results[server_name] = response_keys
defer.returnValue(results)
@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_server_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")
# 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)
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,
)
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.
"""
# TODO(markjh): Store whether the keys have expired.
yield defer.gatherResults(
[
preserve_fn(self.store.store_server_verify_key)(
server_name, server_name, key.time_added, key
)
for key_id, key in verify_keys.items()
],
consumeErrors=True,
).addErrback(unwrapFirstError)