1 files changed, 33 insertions, 15 deletions
diff --git a/synapse/crypto/event_signing.py b/synapse/crypto/event_signing.py
index e65bd61d97..5f733c1cf5 100644
--- a/synapse/crypto/event_signing.py
+++ b/synapse/crypto/event_signing.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
-
+#
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2020 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.
@@ -17,13 +18,17 @@
 import collections.abc
 import hashlib
 import logging
+from typing import Dict
 
 from canonicaljson import encode_canonical_json
 from signedjson.sign import sign_json
+from signedjson.types import SigningKey
 from unpaddedbase64 import decode_base64, encode_base64
 
 from synapse.api.errors import Codes, SynapseError
+from synapse.api.room_versions import RoomVersion
 from synapse.events.utils import prune_event, prune_event_dict
+from synapse.types import JsonDict
 
 logger = logging.getLogger(__name__)
 
@@ -112,18 +117,28 @@ def compute_event_reference_hash(event, hash_algorithm=hashlib.sha256):
     return hashed.name, hashed.digest()
 
 
-def compute_event_signature(event_dict, signature_name, signing_key):
+def compute_event_signature(
+    room_version: RoomVersion,
+    event_dict: JsonDict,
+    signature_name: str,
+    signing_key: SigningKey,
+) -> Dict[str, Dict[str, str]]:
     """Compute the signature of the event for the given name and key.
 
     Args:
-        event_dict (dict): The event as a dict
-        signature_name (str): The name of the entity signing the event
+        room_version: the version of the room that this event is in.
+            (the room version determines the redaction algorithm and hence the
+            json to be signed)
+
+        event_dict: The event as a dict
+
+        signature_name: The name of the entity signing the event
             (typically the server's hostname).
-        signing_key (syutil.crypto.SigningKey): The key to sign with
+
+        signing_key: The key to sign with
 
     Returns:
-        dict[str, dict[str, str]]: Returns a dictionary in the same format of
-        an event's signatures field.
+        a dictionary in the same format of an event's signatures field.
     """
     redact_json = prune_event_dict(event_dict)
     redact_json.pop("age_ts", None)
@@ -137,23 +152,26 @@ def compute_event_signature(event_dict, signature_name, signing_key):
 
 
 def add_hashes_and_signatures(
-    event_dict, signature_name, signing_key, hash_algorithm=hashlib.sha256
+    room_version: RoomVersion,
+    event_dict: JsonDict,
+    signature_name: str,
+    signing_key: SigningKey,
 ):
     """Add content hash and sign the event
 
     Args:
-        event_dict (dict): The event to add hashes to and sign
-        signature_name (str): The name of the entity signing the event
+        room_version: the version of the room this event is in
+
+        event_dict: The event to add hashes to and sign
+        signature_name: The name of the entity signing the event
             (typically the server's hostname).
-        signing_key (syutil.crypto.SigningKey): The key to sign with
-        hash_algorithm: A hasher from `hashlib`, e.g. hashlib.sha256, to use
-            to hash the event
+        signing_key: The key to sign with
     """
 
-    name, digest = compute_content_hash(event_dict, hash_algorithm=hash_algorithm)
+    name, digest = compute_content_hash(event_dict, hash_algorithm=hashlib.sha256)
 
     event_dict.setdefault("hashes", {})[name] = encode_base64(digest)
 
     event_dict["signatures"] = compute_event_signature(
-        event_dict, signature_name=signature_name, signing_key=signing_key
+        room_version, event_dict, signature_name=signature_name, signing_key=signing_key
     )