在 Java 中更改系统属性 - 安全策略文件 [英] Changing System Property in Java - Security Policy file

问题描述

我对 Java 安全模型的理解有些混乱.在我的 ${JDK_HOME}/jre/lib/security/java.policy 文件中，我可以看到以下条目:

I have some confusion in understanding Java Security model. In my ${JDK_HOME}/jre/lib/security/java.policy file, I could see below entries:

grant { 
    // Allows any thread to stop itself using the java.lang.Thread.stop()
    // method that takes no argument.
    // Note that this permission is granted by default only to remain
    // backwards compatible.
    // It is strongly recommended that you either remove this permission
    // from this policy file or further restrict it to code sources
    // that you specify, because Thread.stop() is potentially unsafe.
    // See "http://java.sun.com/notes" for more information.
    permission java.lang.RuntimePermission "stopThread";

    // allows anyone to listen on un-privileged ports
    permission java.net.SocketPermission "localhost:1024-", "listen";

    // "standard" properies that can be read by anyone


    permission java.util.PropertyPermission "java.vm.version", "read";
..... .....

最后一行:permission java.util.PropertyPermission "java.vm.version", "read";

我将其解释为:在VM中运行的Java程序有权读取属性'java.vm.version'

I interpret it as: The Java Program that runs in the VM has permission to read the property 'java.vm.version'

根据这种理解，我编写了一个示例程序来检查是否出现任何运行时错误 如果我更改此属性:

Following this understanding I wrote a sample program just to check, If I get any run time error If I alter this property:

    System.setProperty("java.vm.version", "my.jvm.version.2345");
    System.out.println(System.getProperty("java.vm.version"));

没有错误；而是 System.out.println 显示我修改后的值，即 my.jvm.version.2345

There was no error; instead the System.out.println display my modified value i.e. my.jvm.version.2345

这是否意味着 java.policy 中设置的策略不起作用，我在这里遗漏了什么?

Does that mean policies set in java.policy is not working, what am i missing here?

推荐答案

java.policy 文件不用于普通的 java 进程.您必须首先配置 java 进程以使用 SecurityManager(例如，将-Djava.security.manager"添加到命令行).更多详细信息此处.

the java.policy file is not used in a normal java process. you must first configure the java process to use a SecurityManager (.e.g add "-Djava.security.manager" to the command line). More details here.

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