如何创建 Java 沙箱？

Question

我想让我的应用程序运行其他人的代码，也就是插件。但是，我必须采取哪些措施来确保其安全，以免他们编写恶意代码。我如何控制他们能做什么或不能做什么？

我偶然发现 JVM 具有“内置沙盒”功能 - 它是什么，这是唯一的方法吗？是否有用于制作沙盒的第三方 Java 库？

我有什么选择？感谢您提供指南和示例的链接！

Answer 1

您正在寻找security manager。您可以通过指定policy 来限制应用程序的权限。

Answer 2

• 定义和注册您自己的安全管理器将允许您限制代码的作用 - 请参阅 SecurityManager 的 oracle 文档。

• 另外，考虑创建一个单独的机制来加载代码 - 即您可以编写或实例化另一个 Classloader 以从特殊位置加载代码。您可能有加载代码的约定 - 例如从特殊目录或特殊格式的 zip 文件（如 WAR 文件和 JAR 文件）。如果你正在编写一个类加载器，它会让你不得不做一些工作来加载代码。这意味着如果您看到想要拒绝的某些内容（或某些依赖项），您可能无法加载代码。 http://java.sun.com/javase/6/docs/api/java/lang/ClassLoader.html

Answer 3

对于 AWT/Swing 应用程序，您需要使用非标准的 AppContext 类，该类可能随时更改。因此，为了有效，您需要启动另一个进程来运行插件代码，并处理两者之间的通信（有点像 Chrome）。插件进程将需要一个SecurityManager 集和一个ClassLoader 来隔离插件代码并将适当的ProtectionDomain 应用于插件类。

Answer 4

看看the java-sandbox project，它可以轻松创建非常灵活的沙箱来运行不受信任的代码。

Answer 5

以下是使用 SecurityManager 解决问题的方法：

https://svn.code.sf.net/p/loggifier/code/trunk/de.unkrig.commons.lang/src/de/unkrig/commons/lang/security/Sandbox.java

package de.unkrig.commons.lang.security;

import java.security.AccessControlContext;
import java.security.Permission;
import java.security.Permissions;
import java.security.ProtectionDomain;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;

import de.unkrig.commons.nullanalysis.Nullable;

/**
 * This class establishes a security manager that confines the permissions for code executed through specific classes,
 * which may be specified by class, class name and/or class loader.
 * <p>
 * To 'execute through a class' means that the execution stack includes the class. E.g., if a method of class {@code A}
 * invokes a method of class {@code B}, which then invokes a method of class {@code C}, and all three classes were
 * previously {@link #confine(Class, Permissions) confined}, then for all actions that are executed by class {@code C}
 * the <i>intersection</i> of the three {@link Permissions} apply.
 * <p>
 * Once the permissions for a class, class name or class loader are confined, they cannot be changed; this prevents any
 * attempts (e.g. of the confined class itself) to release the confinement.
 * <p>
 * Code example:
 * <pre>
 *  Runnable unprivileged = new Runnable() {
 *      public void run() {
 *          System.getProperty("user.dir");
 *      }
 *  };
 *
 *  // Run without confinement.
 *  unprivileged.run(); // Works fine.
 *
 *  // Set the most strict permissions.
 *  Sandbox.confine(unprivileged.getClass(), new Permissions());
 *  unprivileged.run(); // Throws a SecurityException.
 *
 *  // Attempt to change the permissions.
 *  {
 *      Permissions permissions = new Permissions();
 *      permissions.add(new AllPermission());
 *      Sandbox.confine(unprivileged.getClass(), permissions); // Throws a SecurityException.
 *  }
 *  unprivileged.run();
 * </pre>
 */
public final
class Sandbox {

    private Sandbox() {}

    private static final Map<Class<?>, AccessControlContext>
    CHECKED_CLASSES = Collections.synchronizedMap(new WeakHashMap<Class<?>, AccessControlContext>());

    private static final Map<String, AccessControlContext>
    CHECKED_CLASS_NAMES = Collections.synchronizedMap(new HashMap<String, AccessControlContext>());

    private static final Map<ClassLoader, AccessControlContext>
    CHECKED_CLASS_LOADERS = Collections.synchronizedMap(new WeakHashMap<ClassLoader, AccessControlContext>());

    static {

        // Install our custom security manager.
        if (System.getSecurityManager() != null) {
            throw new ExceptionInInitializerError("There's already a security manager set");
        }
        System.setSecurityManager(new SecurityManager() {

            @Override public void
            checkPermission(@Nullable Permission perm) {
                assert perm != null;

                for (Class<?> clasS : this.getClassContext()) {

                    // Check if an ACC was set for the class.
                    {
                        AccessControlContext acc = Sandbox.CHECKED_CLASSES.get(clasS);
                        if (acc != null) acc.checkPermission(perm);
                    }

                    // Check if an ACC was set for the class name.
                    {
                        AccessControlContext acc = Sandbox.CHECKED_CLASS_NAMES.get(clasS.getName());
                        if (acc != null) acc.checkPermission(perm);
                    }

                    // Check if an ACC was set for the class loader.
                    {
                        AccessControlContext acc = Sandbox.CHECKED_CLASS_LOADERS.get(clasS.getClassLoader());
                        if (acc != null) acc.checkPermission(perm);
                    }
                }
            }
        });
    }

    // --------------------------

    /**
     * All future actions that are executed through the given {@code clasS} will be checked against the given {@code
     * accessControlContext}.
     *
     * @throws SecurityException Permissions are already confined for the {@code clasS}
     */
    public static void
    confine(Class<?> clasS, AccessControlContext accessControlContext) {

        if (Sandbox.CHECKED_CLASSES.containsKey(clasS)) {
            throw new SecurityException("Attempt to change the access control context for '" + clasS + "'");
        }

        Sandbox.CHECKED_CLASSES.put(clasS, accessControlContext);
    }

    /**
     * All future actions that are executed through the given {@code clasS} will be checked against the given {@code
     * protectionDomain}.
     *
     * @throws SecurityException Permissions are already confined for the {@code clasS}
     */
    public static void
    confine(Class<?> clasS, ProtectionDomain protectionDomain) {
        Sandbox.confine(
            clasS,
            new AccessControlContext(new ProtectionDomain[] { protectionDomain })
        );
    }

    /**
     * All future actions that are executed through the given {@code clasS} will be checked against the given {@code
     * permissions}.
     *
     * @throws SecurityException Permissions are already confined for the {@code clasS}
     */
    public static void
    confine(Class<?> clasS, Permissions permissions) {
        Sandbox.confine(clasS, new ProtectionDomain(null, permissions));
    }

    // Code for 'CHECKED_CLASS_NAMES' and 'CHECKED_CLASS_LOADERS' omitted here.

}

Answer 6

关于这个问题的讨论启发了我开始我自己的沙盒项目。

https://github.com/Black-Mantha/sandbox

在其中我遇到了一个重要的安全问题：“如何让沙箱外的代码绕过SecurityManager？”

我将沙盒代码放在它自己的 ThreadGroup 中，并且总是在该组之外授予权限。如果您无论如何都需要在该组中运行特权代码（例如在回调中），则可以使用 ThreadLocal 仅为该线程设置标志。类加载器将阻止沙箱访问 ThreadLocal。此外，如果您这样做，您需要禁止使用终结器，因为它们在 ThreadGroup 之外的专用线程中运行。

Answer 7

在深入研究 Java 安全 API 一天后，我发现了一个非常简单的解决方案，可以在受权限限制的沙箱中执行不受信任的代码：

https://github.com/janino-compiler/janino/blob/master/commons-compiler/src/main/java/org/codehaus/commons/compiler/Sandbox.java

这是（简化的）源代码：

package org.codehaus.commons.compiler;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Policy;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.security.ProtectionDomain;

public final
class Sandbox {

    static {

        if (System.getSecurityManager() == null) {

            // Before installing the security manager, configure a decent ("positive") policy.
           Policy.setPolicy(new Policy() {

                @Override public boolean
                implies(ProtectionDomain domain, Permission permission) { return true; }
            });

            System.setSecurityManager(new SecurityManager());
        }
    }

    private final AccessControlContext accessControlContext;

    /**
     * @param permissions Will be applied on later calls to {@link #confine(PrivilegedAction)} and {@link
     *                    #confine(PrivilegedExceptionAction)}
     */
    public
    Sandbox(PermissionCollection permissions) {
        this.accessControlContext = new AccessControlContext(new ProtectionDomain[] {
            new ProtectionDomain(null, permissions)
        });
    }

    /**
     * Runs the given <var>action</var>, confined by the permissions configured through the {@link
     * #Sandbox(PermissionCollection) constructor}.
     *
     * @return The value returned by the <var>action</var>
     */
    public <R> R
    confine(PrivilegedAction<R> action) {
        return AccessController.doPrivileged(action, this.accessControlContext);
    }

    public <R> R
    confine(PrivilegedExceptionAction<R> action) throws Exception {
        try {
            return AccessController.doPrivileged(action, this.accessControlContext);
        } catch (PrivilegedActionException pae) {
            throw pae.getException();
        }
    }
}