问题描述
我们都知道，即使您隐藏了危险的函数，因为您可以使用Python的自省功能深入挖掘并重新提取它们。例如，即使删除 __ builtins __ ，也可以使用
We all know that eval is dangerous, even if you hide dangerous functions, because you can use Python's introspection features to dig down into things and re-extract them. For example, even if you delete __builtins__, you can retrieve them with
[c for c in ().__class__.__base__.__subclasses__()
if c.__name__ == 'catch_warnings'][0]()._module.__builtins__
但是，我所看到的每个示例都使用属性访问。如果我禁用所有内置函数，和禁用属性访问（通过使用Python标记器标记输入并在具有属性访问标记的情况下拒绝输入，该怎么办）？
However, every example I've seen of this uses attribute access. What if I disable all builtins, and disable attribute access (by tokenizing the input with a Python tokenizer and rejecting it if it has an attribute access token)?
在您问不，在我的用例中，我不需要这两个，所以它不会太残废。
And before you ask, no, for my use-case, I do not need either of these, so it isn't too crippling.
我要做的是使SymPy的功能更安全。当前，它对输入进行标记化，对其进行一些转换，然后在名称空间中进行评估。但这是不安全的，因为它允许属性访问（即使确实不需要）。
What I'm trying to do is make SymPy's sympify function more safe. Currently it tokenizes the input, does some transformations on it, and evals it in a namespace. But it's unsafe because it allows attribute access (even though it really doesn't need it).
推荐答案
我要提及Python 3.6的新功能之一-。
I'm going to mention one of the new features of Python 3.6 - f-strings.
他们可以计算表达式，
>>> eval('f"{().__class__.__base__}"', {'__builtins__': None}, {})
"<class 'object'>"
，但是Python的标记器不会检测到属性访问：
but the attribute access won't be detected by Python's tokenizer:
0,0-0,0: ENCODING 'utf-8'
1,0-1,1: ERRORTOKEN "'"
1,1-1,27: STRING 'f"{().__class__.__base__}"'
2,0-2,0: ENDMARKER ''
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