1 files changed, 13 insertions, 3 deletions
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index b3f76428b6..a13f11f8d8 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -25,8 +25,18 @@ from synapse.logging import context
 
 logger = logging.getLogger(__name__)
 
-# Create a custom encoder to reduce the whitespace produced by JSON encoding.
-json_encoder = json.JSONEncoder(separators=(",", ":"))
+
+def _reject_invalid_json(val):
+    """Do not allow Infinity, -Infinity, or NaN values in JSON."""
+    raise ValueError("Invalid JSON value: '%s'" % val)
+
+
+# Create a custom encoder to reduce the whitespace produced by JSON encoding and
+# ensure that valid JSON is produced.
+json_encoder = json.JSONEncoder(allow_nan=False, separators=(",", ":"))
+
+# Create a custom decoder to reject Python extensions to JSON.
+json_decoder = json.JSONDecoder(parse_constant=_reject_invalid_json)
 
 
 def unwrapFirstError(failure):
@@ -36,7 +46,7 @@ def unwrapFirstError(failure):
 
 
 @attr.s
-class Clock(object):
+class Clock:
     """
     A Clock wraps a Twisted reactor and provides utilities on top of it.