Be stricter about JSON that is accepted by Synapse (#8106)

3 files changed, 14 insertions, 10 deletions

diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 2ab30ce897..f216382636 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -21,8 +21,6 @@ import re
 from typing import List, Optional
 from urllib import parse as urlparse
 
-from canonicaljson import json
-
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import (
     AuthError,
@@ -46,6 +44,7 @@ from synapse.rest.client.v2_alpha._base import client_patterns
 from synapse.storage.state import StateFilter
 from synapse.streams.config import PaginationConfig
 from synapse.types import RoomAlias, RoomID, StreamToken, ThirdPartyInstanceID, UserID
+from synapse.util import json_decoder
 
 MYPY = False
 if MYPY:
@@ -519,7 +518,9 @@ class RoomMessageListRestServlet(RestServlet):
         filter_str = parse_string(request, b"filter", encoding="utf-8")
         if filter_str:
             filter_json = urlparse.unquote(filter_str)
-            event_filter = Filter(json.loads(filter_json))  # type: Optional[Filter]
+            event_filter = Filter(
+                json_decoder.decode(filter_json)
+            )  # type: Optional[Filter]
             if (
                 event_filter
                 and event_filter.filter_json.get("event_format", "client")
@@ -631,7 +632,9 @@ class RoomEventContextServlet(RestServlet):
         filter_str = parse_string(request, b"filter", encoding="utf-8")
         if filter_str:
             filter_json = urlparse.unquote(filter_str)
-            event_filter = Filter(json.loads(filter_json))  # type: Optional[Filter]
+            event_filter = Filter(
+                json_decoder.decode(filter_json)
+            )  # type: Optional[Filter]
         else:
             event_filter = None
 
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index a5c24fbd63..96488b131a 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -16,8 +16,6 @@
 import itertools
 import logging
 
-from canonicaljson import json
-
 from synapse.api.constants import PresenceState
 from synapse.api.errors import Codes, StoreError, SynapseError
 from synapse.api.filtering import DEFAULT_FILTER_COLLECTION, FilterCollection
@@ -29,6 +27,7 @@ from synapse.handlers.presence import format_user_presence_state
 from synapse.handlers.sync import SyncConfig
 from synapse.http.servlet import RestServlet, parse_boolean, parse_integer, parse_string
 from synapse.types import StreamToken
+from synapse.util import json_decoder
 
 from ._base import client_patterns, set_timeline_upper_limit
 
@@ -125,7 +124,7 @@ class SyncRestServlet(RestServlet):
             filter_collection = DEFAULT_FILTER_COLLECTION
         elif filter_id.startswith("{"):
             try:
-                filter_object = json.loads(filter_id)
+                filter_object = json_decoder.decode(filter_id)
                 set_timeline_upper_limit(
                     filter_object, self.hs.config.filter_timeline_limit
                 )
diff --git a/synapse/rest/key/v2/remote_key_resource.py b/synapse/rest/key/v2/remote_key_resource.py
index e266204f95..5db7f81c2d 100644
--- a/synapse/rest/key/v2/remote_key_resource.py
+++ b/synapse/rest/key/v2/remote_key_resource.py
@@ -15,19 +15,19 @@
 import logging
 from typing import Dict, Set
 
-from canonicaljson import json
 from signedjson.sign import sign_json
 
 from synapse.api.errors import Codes, SynapseError
 from synapse.crypto.keyring import ServerKeyFetcher
 from synapse.http.server import DirectServeJsonResource, respond_with_json
 from synapse.http.servlet import parse_integer, parse_json_object_from_request
+from synapse.util import json_decoder
 
 logger = logging.getLogger(__name__)
 
 
 class RemoteKey(DirectServeJsonResource):
-    """HTTP resource for retreiving the TLS certificate and NACL signature
+    """HTTP resource for retrieving the TLS certificate and NACL signature
     verification keys for a collection of servers. Checks that the reported
     X.509 TLS certificate matches the one used in the HTTPS connection. Checks
     that the NACL signature for the remote server is valid. Returns a dict of
@@ -209,13 +209,15 @@ class RemoteKey(DirectServeJsonResource):
                     # Cast to bytes since postgresql returns a memoryview.
                     json_results.add(bytes(result["key_json"]))
 
+        # If there is a cache miss, request the missing keys, then recurse (and
+        # ensure the result is sent).
         if cache_misses and query_remote_on_cache_miss:
             await self.fetcher.get_keys(cache_misses)
             await self.query_keys(request, query, query_remote_on_cache_miss=False)
         else:
             signed_keys = []
             for key_json in json_results:
-                key_json = json.loads(key_json.decode("utf-8"))
+                key_json = json_decoder.decode(key_json.decode("utf-8"))
                 for signing_key in self.config.key_server_signing_keys:
                     key_json = sign_json(key_json, self.config.server_name, signing_key)