/*

 * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.applet;

import java.io.File;

import java.io.FilePermission;

import java.io.IOException;

import java.io.FileDescriptor;

import java.net.URL;

import java.net.URLClassLoader;

import java.net.InetAddress;

import java.net.UnknownHostException;

import java.net.SocketPermission;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.HashSet;

import java.util.StringTokenizer;

import java.security.*;

import java.lang.reflect.*;

import sun.awt.AWTSecurityManager;

import sun.awt.AppContext;

import sun.security.provider.*;

import sun.security.util.SecurityConstants;

/**

 * This class defines an applet security policy

 *

 */

public

class AppletSecurity extends AWTSecurityManager {

    //URLClassLoader.acc

    private static Field facc = null;

    //AccessControlContext.context;

    private static Field fcontext = null;

    static {

        try {

            facc = URLClassLoader.class.getDeclaredField("acc");

            facc.setAccessible(true);

            fcontext = AccessControlContext.class.getDeclaredField("context");

            fcontext.setAccessible(true);

        } catch (NoSuchFieldException e) {

            throw new UnsupportedOperationException(e);

        }

    }

    /**

     * Construct and initialize.

     */

    public AppletSecurity() {

        reset();

    }

    // Cache to store known restricted packages

    private HashSet restrictedPackages = new HashSet();

    /**

     * Reset from Properties

     */

    public void reset()

    {

        // Clear cache

        restrictedPackages.clear();

        AccessController.doPrivileged(new PrivilegedAction() {

            public Object run()

            {

                // Enumerate system properties

                Enumeration e = System.getProperties().propertyNames();

                while (e.hasMoreElements())

                {

                    String name = (String) e.nextElement();

                    if (name != null && name.startsWith("package.restrict.access."))

                    {

                        String value = System.getProperty(name);

                        if (value != null && value.equalsIgnoreCase("true"))

                        {

                            String pkg = name.substring(24);

                            // Cache restricted packages

                            restrictedPackages.add(pkg);

                        }

                    }

                }

                return null;

            }

        });

    }

    /**

     * get the current (first) instance of an AppletClassLoader on the stack.

     */

    private AppletClassLoader currentAppletClassLoader()

    {

        // try currentClassLoader first

        ClassLoader loader = currentClassLoader();

        if ((loader == null) || (loader instanceof AppletClassLoader))

            return (AppletClassLoader)loader;

        // if that fails, get all the classes on the stack and check them.

        Class[] context = getClassContext();

        for (int i = 0; i < context.length; i++) {

            loader = context[i].getClassLoader();

            if (loader instanceof AppletClassLoader)

                return (AppletClassLoader)loader;

        }

        /*

         * fix bug # 6433620 the logic here is : try to find URLClassLoader from

         * class context, check its AccessControlContext to see if

         * AppletClassLoader is in stack when it's created. for this kind of

         * AppletClassLoader.

         */

        for (int i = 0; i < context.length; i++) {

            final ClassLoader currentLoader = context[i].getClassLoader();

            if (currentLoader instanceof URLClassLoader) {

                loader = (ClassLoader) AccessController.doPrivileged(new PrivilegedAction() {

                    public Object run() {

                        AccessControlContext acc = null;

                        ProtectionDomain[] pds = null;

                        try {

                            acc = (AccessControlContext) facc.get(currentLoader);

                            if (acc == null) {

                                return null;

                            }

                            pds = (ProtectionDomain[]) fcontext.get(acc);

                            if (pds == null) {

                                return null;

                            }

                        } catch (Exception e) {

                            throw new UnsupportedOperationException(e);

                        }

                        for (int i=0; i<pds.length; i++) {

                            ClassLoader cl = pds[i].getClassLoader();

                            if (cl instanceof AppletClassLoader) {

                                    return cl;

                            }

                        }

                        return null;

                    }

                });

                if (loader != null) {

                    return (AppletClassLoader) loader;

                }

            }

        }

        // if that fails, try the context class loader

        loader = Thread.currentThread().getContextClassLoader();

        if (loader instanceof AppletClassLoader)

            return (AppletClassLoader)loader;

        // no AppletClassLoaders on the stack

        return (AppletClassLoader)null;

    }

    /**

     * Returns true if this threadgroup is in the applet's own thread

     * group. This will return false if there is no current class

     * loader.

     */

    protected boolean inThreadGroup(ThreadGroup g) {

        if (currentAppletClassLoader() == null)

            return false;

        else

            return getThreadGroup().parentOf(g);

    }

    /**

     * Returns true of the threadgroup of thread is in the applet's

     * own threadgroup.

     */

    protected boolean inThreadGroup(Thread thread) {

        return inThreadGroup(thread.getThreadGroup());

    }

    /**

     * Applets are not allowed to manipulate threads outside

     * applet thread groups. However a terminated thread no longer belongs

     * to any group.

     */

    public void checkAccess(Thread t) {

        /* When multiple applets is reloaded simultaneously, there will be

         * multiple invocations to this method from plugin's SecurityManager.

         * This method should not be synchronized to avoid deadlock when

         * a page with multiple applets is reloaded

         */

        if ((t.getState() != Thread.State.TERMINATED) && !inThreadGroup(t)) {

            checkPermission(SecurityConstants.MODIFY_THREAD_PERMISSION);

        }

    }

    private boolean inThreadGroupCheck = false;

    /**

     * Applets are not allowed to manipulate thread groups outside

     * applet thread groups.

     */

    public synchronized void checkAccess(ThreadGroup g) {

        if (inThreadGroupCheck) {

            // if we are in a recursive check, it is because

            // inThreadGroup is calling appletLoader.getThreadGroup

            // in that case, only do the super check, as appletLoader

            // has a begin/endPrivileged

            checkPermission(SecurityConstants.MODIFY_THREADGROUP_PERMISSION);

        } else {

            try {

                inThreadGroupCheck = true;

                if (!inThreadGroup(g)) {

                    checkPermission(SecurityConstants.MODIFY_THREADGROUP_PERMISSION);

                }

            } finally {

                inThreadGroupCheck = false;

            }

        }

    }

    /**

     * Throws a <code>SecurityException</code> if the

     * calling thread is not allowed to access the package specified by

     * the argument.

     * <p>

     * This method is used by the <code>loadClass</code> method of class

     * loaders.

     * <p>

     * The <code>checkPackageAccess</code> method for class

     * <code>SecurityManager</code>  calls

     * <code>checkPermission</code> with the

     * <code>RuntimePermission("accessClassInPackage."+pkg)</code>

     * permission.

     *

     * @param      pkg   the package name.

     * @exception  SecurityException  if the caller does not have

     *             permission to access the specified package.

     * @see        java.lang.ClassLoader#loadClass(java.lang.String, boolean)

     */

    public void checkPackageAccess(final String pkgname) {

        // first see if the VM-wide policy allows access to this package

        super.checkPackageAccess(pkgname);

        // now check the list of restricted packages

        for (Iterator iter = restrictedPackages.iterator(); iter.hasNext();)

        {

            String pkg = (String) iter.next();

            // Prevent matching "sun" and "sunir" even if they

            // starts with similar beginning characters

            //

            if (pkgname.equals(pkg) || pkgname.startsWith(pkg + "."))

            {

                checkPermission(new java.lang.RuntimePermission

                            ("accessClassInPackage." + pkgname));

            }

        }

    }

    /**

     * Tests if a client can get access to the AWT event queue.

     * <p>

     * This method calls <code>checkPermission</code> with the

     * <code>AWTPermission("accessEventQueue")</code> permission.

     *

     * @since   JDK1.1

     * @exception  SecurityException  if the caller does not have

     */

    public void checkAwtEventQueueAccess() {

        AppContext appContext = AppContext.getAppContext();

        AppletClassLoader appletClassLoader = currentAppletClassLoader();

        if (AppContext.isMainContext(appContext) && (appletClassLoader != null)) {

            // If we're about to allow access to the main EventQueue,

            // and anything untrusted is on the class context stack,

            // disallow access.

            super.checkPermission(SecurityConstants.AWT.CHECK_AWT_EVENTQUEUE_PERMISSION);

        }

    } // checkAwtEventQueueAccess()

    /**

     * Returns the thread group of the applet. We consult the classloader

     * if there is one.

     */

    public ThreadGroup getThreadGroup() {

        /* If any applet code is on the execution stack, we return

           that applet's ThreadGroup.  Otherwise, we use the default

           behavior. */

        AppletClassLoader appletLoader = currentAppletClassLoader();

        ThreadGroup loaderGroup = (appletLoader == null) ? null

                                          : appletLoader.getThreadGroup();

        if (loaderGroup != null) {

            return loaderGroup;

        } else {

            return super.getThreadGroup();

        }

    } // getThreadGroup()

    /**

      * Get the AppContext corresponding to the current context.

      * The default implementation returns null, but this method

      * may be overridden by various SecurityManagers

      * (e.g. AppletSecurity) to index AppContext objects by the

      * calling context.

      *

      * @return  the AppContext corresponding to the current context.

      * @see     sun.awt.AppContext

      * @see     java.lang.SecurityManager

      * @since   JDK1.2.1

      */

    public AppContext getAppContext() {

        AppletClassLoader appletLoader = currentAppletClassLoader();

        if (appletLoader == null) {

            return null;

        } else {

            AppContext context =  appletLoader.getAppContext();

            // context == null when some thread in applet thread group

            // has not been destroyed in AppContext.dispose()

            if (context == null) {

                throw new SecurityException("Applet classloader has invalid AppContext");

            }

            return context;

        }

    }

} // class AppletSecurity