From 029b7ad7b94d167b19d63a5dc777a806b0e073f3 Mon Sep 17 00:00:00 2001
From: Patrick Cloke <clokep@users.noreply.github.com>
Date: Fri, 27 Aug 2021 07:08:02 -0400
Subject: [PATCH] Remove unused `compare_digest` function. (#10706)

---
 changelog.d/10706.misc          |  1 +
 synapse/rest/client/register.py | 13 -------------
 2 files changed, 1 insertion(+), 13 deletions(-)
 create mode 100644 changelog.d/10706.misc

diff --git a/changelog.d/10706.misc b/changelog.d/10706.misc
new file mode 100644
index 0000000000..eed4aa58d6
--- /dev/null
+++ b/changelog.d/10706.misc
@@ -0,0 +1 @@
+Remove unused `compare_digest` function.
diff --git a/synapse/rest/client/register.py b/synapse/rest/client/register.py
index 2781a0ea96..7b5f49d635 100644
--- a/synapse/rest/client/register.py
+++ b/synapse/rest/client/register.py
@@ -12,7 +12,6 @@
 # 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 hmac
 import logging
 import random
 from typing import List, Union
@@ -60,18 +59,6 @@ from synapse.util.threepids import (
 
 from ._base import client_patterns, interactive_auth_handler
 
-# We ought to be using hmac.compare_digest() but on older pythons it doesn't
-# exist. It's a _really minor_ security flaw to use plain string comparison
-# because the timing attack is so obscured by all the other code here it's
-# unlikely to make much difference
-if hasattr(hmac, "compare_digest"):
-    compare_digest = hmac.compare_digest
-else:
-
-    def compare_digest(a, b):
-        return a == b
-
-
 logger = logging.getLogger(__name__)
 
 
-- 
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