Accept the TOTP token before and after the current

tildes/tests/test_user.py

 # Copyright (c) 2018 Tildes contributors <code@tildes.net>
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
+from datetime import datetime
+
+from dateutil import tz
+from freezegun import freeze_time
 from marshmallow.exceptions import ValidationError
 from pyramid.security import principals_allowed_by_permission
 from pytest import raises
@@ -160,3 +164,21 @@ def test_ban_permission_manually_granted():
 
     principals = principals_allowed_by_permission(user, "ban")
     assert principals == {"*:user.ban"}
+
+
+def test_totp_token_window():
+    """Ensure the TOTP token accepts the one directly before and after the current."""
+    user = User("Test_User", "password")
+    user.two_factor_enabled = True
+    user.two_factor_secret = "USKIRUUOFM54XGSXELCOM6K7KODOB2EC"
+
+    invalid_tokens = ["896500", "075549"]
+    valid_tokens = ["293601", "733932", "295043"]
+
+    target_time = datetime(2023, 6, 16, 23, 55, tzinfo=tz.UTC)
+    with freeze_time(target_time):
+        for token in valid_tokens:
+            assert user.is_correct_two_factor_code(token)
+
+        for token in invalid_tokens:
+            assert not user.is_correct_two_factor_code(token)

tildes/tildes/models/user/user.py

@@ -279,7 +279,7 @@ class User(DatabaseModel):
         # some possible user input (such as unicode) can cause an error in the totp
         # library, catch that and treat it the same as an invalid code
         try:
-            is_valid_code = totp.verify(code)
+            is_valid_code = totp.verify(code, valid_window=1)
         except TypeError:
             is_valid_code = False