JSON数据 - 解析或'评估' [英] JSON Data - Parsed Or 'Eval'ed

问题描述

从安全角度来看，我可以看到对传入的JSON数据执行'eval'是一个严重的错误。如果你得到如下数据，你会遇到一些问题。

From a security perspective, I can see simply doing an 'eval' on incoming JSON data as a critical mistake. If you got data like below you'd have some problems.

{ someData:((function() { 
    alert("i'm in ur code hackin' ur page"); 
})()) }

我想知道最流行的Javascript库做了什么？是手动解析还是仅仅是评估？

I wondered what do most popular Javascript libraries do? Is it a manual parse or simply an eval?

我不是问我是否应该eval / parse - 我问的是一些流行的Javascript库使用了什么方法（jQuery，Prototype等等）

I'm not asking if I should eval/parse - I was asking what methods some of the popular Javascript libraries used (jQuery, Prototype, etc...)

推荐答案

以下是官方JavaScript解析器：

// In the second stage, we run the text against regular expressions that look
// for non-JSON patterns. We are especially concerned with '()' and 'new'
// because they can cause invocation, and '=' because it can cause mutation.
// But just to be safe, we want to reject all unexpected forms.

// We split the second stage into 4 regexp operations in order to work around
// crippling inefficiencies in IE's and Safari's regexp engines. First we
// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
// replace all simple value tokens with ']' characters. Third, we delete all
// open brackets that follow a colon or comma or that begin the text. Finally,
// we look to see that the remaining characters are only whitespace or ']' or
// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.

if (/^[\],:{}\s]*$/.
    test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').
    replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
    replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {

// In the third stage we use the eval function to compile the text into a
// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
// in JavaScript: it can begin a block or an object literal. We wrap the text
// in parens to eliminate the ambiguity.

    j = eval('(' + text + ')');

    ...

除了内置的 JSON解析支持，这是所有（基于库的）安全JSON解析器所做的事情（即， eval 之前的正则表达式测试。

With the exception of the built-in JSON parsing support that is in modern browsers, this is what all (library-based) secure JSON parsers do (ie, a regex test before eval).

安全库（除官方json2之外）实施）

Secure libraries (in addition to the official json2 implementation)

Prototype的 isJSON 功能。

Prototype's isJSON function.

Mootools' JSON.decode 功能（再次通过 eval ）。

Mootools' JSON.decode function (again, via a regex test before eval).

不安全库：

道场的 fromJson 不提供安全 eval ing。 这是他们的整个实施（减去评论）：

dojo's fromJson does not provide secure evaling. Here is their entire implementation (minus comments):

dojo.fromJson = function(json) {
    return eval("(" + json + ")");
}

jQuery不提供安全的JSON eval 'ing，但请参阅官方插件 secureEvalJSON 功能（第143行）。

jQuery does not provide secure JSON eval'ing, but see the official plugin's secureEvalJSON function (line 143).

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