[启用Java安全管理器后，获取系统属性“ os.arch”时权限被拒绝期望

Question

我有一个简单的Java应用程序ClientApp，它启用了Java安全管理器。该应用程序正在尝试调用获取“ os.arch”系统属性的Test jar方法。由于这很耗时，因此我们正在使用Completable任务来调用新线程。

此为例外

java.util.concurrent.ExecutionException: java.security.AccessControlException: access denied ("java.util.PropertyPermission" "os.arch" "read")
    at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
    at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1895)
    at SecurityApplication.ClientApp.main(ClientApp.java:23)
Caused by: java.security.AccessControlException: access denied ("java.util.PropertyPermission" "os.arch" "read")
    at java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
    at java.security.AccessController.checkPermission(AccessController.java:884)
    at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
    at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1294)
    at java.lang.System.getProperty(System.java:717)
    at com.ravindra.CustomSupplier.get(CustomSupplier.java:10)
    at com.ravindra.CustomSupplier.get(CustomSupplier.java:5)
    at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590)
    at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1582)
    at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
    at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
    at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
    at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

ClientApp：

import com.test.App;

public class ClientApp
{
    public static void main(String[] args)
    {
        //Enable security 
        SecurityManager securityManager = new SecurityManager();
        System.setSecurityManager(securityManager);

        TestApp app = new TestApp();

        Future<String> future = app.getOsArchitecture();

        try
        {
            // blocking Aysnc get Future call for result
            System.out.println(future.get());
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

Test.jar具有以下2个类文件

Test.java

final public class TestApp
{
    public Future<String> getOsArchitecture()
    {
        CompletableFuture<String> completableFuture
                = CompletableFuture.supplyAsync(new CustomSupplier());

        return completableFuture;
    }
}

CustomSupplier.java

public class CustomSupplier implements Supplier<String> {
    public CustomSupplier() {
    }

    public String get() {
        //Time consuming complex Task and finally return "os.arch"
        //...
        //...
        //...
        return System.getProperty("os.arch");
    }
}

但是，当我们禁用Java Security Manager时，程序可以正常运行。

非常感谢您的帮助。

Answer 1

默认ForkJoinPool使用配置为没有特权的线程。

一种解决方案是使用自定义线程工厂或使用普通线程的任何其他ForkJoinPool实现来创建新的Executor实例。不足之处在于，创建自己的线程池需要安全管理器授予相关权限。

另一种选择是将查询作为特权操作执行，而忽略调用线程的限制：

public class CustomSupplier implements Supplier<String> {
    public CustomSupplier() {
    }

    public String get() {
        //Time consuming complex Task and finally return "os.arch"
        //...
        //...
        //...
        return AccessController.doPrivileged(
            (PrivilegedAction<String>)() -> System.getProperty("os.arch"));
    }
}

这将忽略调用方的特权，并在调用doPrivileged的代码（即您的CustomSupplier）的许可下执行查询。默认情况下，授予应用程序代码读取"os.arch"系统属性的权限。

但是由于预计该系统属性在应用程序的生存期内不会更改，并且查询它不是一项昂贵的操作，因此无需在后台执行查询。

public class CustomSupplier implements Supplier<String> {
    public CustomSupplier() {
    }

    public String get() {
        //Time consuming complex Task and finally return "os.arch"
        //...
        //...
        //...
        return ARCH;
    }
    static final String ARCH = System.getProperty("os.arch");
}