Fix unsafe getattr() in DSL evaluator (Issue #15)

dsl_runtime/lang/expression.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import ast
+from collections.abc import Mapping
 import operator
 import time
 from typing import Any, Dict
@@ -28,6 +29,29 @@
     ast.UAdd: operator.pos,
 }
 
+_BLOCKED_ATTRS = frozenset(
+    {
+        "__class__",
+        "__dict__",
+        "__globals__",
+        "__mro__",
+        "__subclasses__",
+        "__bases__",
+        "__base__",
+        "__code__",
+        "__closure__",
+        "__func__",
+        "__self__",
+        "__module__",
+    }
+)
+
+
+def _validate_attr_name(attr: str) -> None:
+    """Reject private/dunder attributes and non-identifier attribute names."""
+    if not attr.isidentifier() or attr.startswith("_") or attr in _BLOCKED_ATTRS:
+        raise ValueError(f"不允许访问属性: {attr}")
+
 
 class SafeEvaluator(ast.NodeVisitor):
     """安全表达式求值器，支持算术/比较/逻辑/变量。"""
@@ -86,8 +110,21 @@ def visit_IfExp(self, node: ast.IfExp) -> Any:  # type: ignore[override]
         return self.visit(node.body) if self.visit(node.test) else self.visit(node.orelse)
 
     def visit_Attribute(self, node: ast.Attribute) -> Any:  # type: ignore[override]
+        attr = node.attr
+        _validate_attr_name(attr)
         value = self.visit(node.value)
-        return getattr(value, node.attr)
+
+        if isinstance(value, Mapping):
+            if attr in value:
+                return value[attr]
+            raise KeyError(attr)
+
+        # Only expose data attributes that are explicitly present on an instance.
+        # This avoids reaching descriptors/classes such as __class__, mro, or methods.
+        instance_attrs = getattr(value, "__dict__", {})
+        if isinstance(instance_attrs, dict) and attr in instance_attrs:
+            return instance_attrs[attr]
+        raise ValueError(f"不允许访问属性: {attr}")
 
     def visit_Subscript(self, node: ast.Subscript) -> Any:  # type: ignore[override]
         value = self.visit(node.value)