Java字符串不可变如何提高安全性? [英] How does Java strings being immutable increase security?

问题描述

我刚刚了解到 String 是不可变的.当我阅读其背后的原因时，出现了一些原因，例如性能提高，或者由于无法修改其值，因此可以由多个线程共享.这些我确实理解的原因.

I just learned that a String is immutable. When I was reading the reason behind it a few reasons came up, for example performance increases, or since its value cannot be modified it can be shared by multiple threads. These reasons I do understand.

但是我不知道它与安全性之间的关系. String 是不可变的，对Java安全性有何帮助?

But I don't get how it is related to security. How does a String being immutable help in Java security?

推荐答案

编写类库的一种非常普遍的做法是将传递到API的参数存储在构造函数中，例如:

A very common practice in writing class libraries is storing the parameters passed into your API, say, in a constructor, like this:

public class MyApi {
    final String myUrl;
    public MyApi(String urlString) {
        // Verify that urlString points to an approved server
        if (!checkApprovedUrl(urlString)) throw new IllegalArgumentException();
        myUrl = urlString;
    }
}

是 String 可变的，这将导致微妙的利用:攻击者将传递一个好的URL，等待几微秒，然后将URL设置为指向攻击站点.

Were String mutable, this would lead to a subtle exploit: an attacker would pass a good URL, wait for a few microseconds, and then set the URL to point to an attack site.

由于不复制而存储是一种相当普遍的做法，并且由于字符串是最常用的数据类型之一，因此使字符串可变仍然会打开许多​​尚未编写但仍存在严重安全问题的API.使字符串不可变会关闭所有API(包括尚未编写的API)的特定安全漏洞.

Since storing without copying is a reasonably common practice, and because strings are among the most commonly used data types, leaving strings mutable would open up many APIs that are not written yet open to a serious security problem. Making strings immutable closes this particular security hole for all APIs, including the ones that are not written yet.

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