fix: harden twenty four game submissions

backend/contest/game_services.py

@@ -1,5 +1,6 @@
 import ast
 import secrets
+import unicodedata
 from collections import Counter
 from fractions import Fraction
 
@@ -36,6 +37,18 @@ TWENTY_FOUR_PUZZLES = {
     MathGameAttempt.Difficulty.HARD: [(1, 5, 5, 5), (3, 3, 7, 7), (5, 5, 7, 11)],
 }
 
+TWENTY_FOUR_SYMBOLS = str.maketrans(
+    {
+        "×": "*",
+        "·": "*",
+        "∙": "*",
+        "÷": "/",
+        "−": "-",
+        "–": "-",
+        "—": "-",
+    }
+)
+
 
 def _grid_from_text(value):
     return [[int(value[row * 9 + column]) for column in range(9)] for row in range(9)]
@@ -80,7 +93,10 @@ def start_game(user, kind, difficulty):
 
 
 def _validate_twenty_four_expression(source, numbers):
-    source = str(source or "").strip()
+    source = unicodedata.normalize("NFKC", str(source or "")).translate(
+        TWENTY_FOUR_SYMBOLS
+    )
+    source = source.strip()
     if not source or len(source) > 120:
         raise ValidationError({"expression": "请输入不超过 120 个字符的表达式"})
     try:
@@ -90,7 +106,11 @@ def _validate_twenty_four_expression(source, numbers):
     used = []
 
     def evaluate(node):
-        if isinstance(node, ast.Constant) and isinstance(node.value, int):
+        if (
+            isinstance(node, ast.Constant)
+            and isinstance(node.value, int)
+            and not isinstance(node.value, bool)
+        ):
             used.append(node.value)
             return Fraction(node.value)
         if isinstance(node, ast.BinOp) and isinstance(