Apple Developer Connection Student Program/ADC Tools Sampler CD Disk 3 1999.iso/Metrowerks CodeWarrior/Java Support/Java_Source/Java2/src/java/security/SecureClassLoader.java

Java Source | 1999-05-28 | 5.0 KB | 163 lines | [TEXT/CWIE]

/*
 * @(#)SecureClassLoader.java    1.69 98/09/24
 *
 * Copyright 1997, 1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.security;

import java.util.Hashtable;
import java.util.ArrayList;
import java.net.URL;

import sun.security.util.Debug;

/**
 * This class extends ClassLoader with additional support for defining
 * classes with an associated code source and permissions which are
 * retrieved by the system policy by default.
 *
 * @version 1.69, 09/24/98
 * @author  Li Gong
 * @author  Roland Schemers
 */
public class SecureClassLoader extends ClassLoader {
    // Hashtable that maps CodeSource to ProtectionDomain
    private Hashtable pdcache = new Hashtable(11);

    private static final Debug debug = Debug.getInstance("scl");

    /**
     * Creates a new SecureClassLoader using the specified parent
     * class loader for delegation.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code>
     * method  to ensure creation of a class loader is allowed.
     *
     * @param parent the parent ClassLoader
     * @exception  SecurityException  if a security manager exists and its
     *             <code>checkCreateClassLoader</code> method doesn't allow
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    protected SecureClassLoader(ClassLoader parent) {
    super(parent);
    // this is to make the stack depth consistent with 1.1
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
        security.checkCreateClassLoader();
    }
    }

    /**
     * Creates a new SecureClassLoader using the default parent class
     * loader for delegation.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code>
     * method  to ensure creation of a class loader is allowed.
     *
     * @exception  SecurityException  if a security manager exists and its
     *             <code>checkCreateClassLoader</code> method doesn't allow
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    protected SecureClassLoader() {
    super();
    // this is to make the stack depth consistent with 1.1
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
        security.checkCreateClassLoader();
    }
    }

    /**
     * Converts an array of bytes into an instance of class Class,
     * with an optional CodeSource. Before the
     * class can be used it must be resolved.
     * @param name the name of the class
     * @param b the class bytes
     * @param off the start offset of the class bytes
     * @param len the length of the class bytes
     * @param cs the associated CodeSource, or null if none
     * @return the <code>Class</code> object created from the data,
     *         and optional CodeSource.
     */
    protected final Class defineClass(String name, byte[] b, int off, int len,
                      CodeSource cs)
    {
    if (cs == null)
        return defineClass(name, b, off, len);
    else
        return defineClass(name, b, off, len, getProtectionDomain(cs));
    }

    /**
     * Returns the permissions for the given codesource object.
     * The default implementation of this method invokes the
     * java.security.Policy.getPermissions method to get the permissions
     * granted by the policy to the specified codesource.
     * <p>
     * This method is invoked by the defineClass method that takes
     * a CodeSource as an argument when it is constructing the
     * ProtectionDomain for the class being defined.
     * <p>
     * @param codesource the codesource.
     *
     * @return the permissions granted to the codesource.
     *
     */
    protected PermissionCollection getPermissions(CodeSource codesource)
    {
    Policy p = Policy.getPolicyNoCheck();

    PermissionCollection perms;
    if (p == null) {
        return null;
    } else {
        perms = p.getPermissions(codesource);
    }
    return perms;
    }

    /*
     * Returned cached ProtectionDomain for the specified CodeSource.
     */
    private ProtectionDomain getProtectionDomain(CodeSource cs) {
    if (cs == null)
        return null;

    ProtectionDomain pd = (ProtectionDomain)pdcache.get(cs);
    if (pd == null) {
        synchronized (pdcache) {
        pd = (ProtectionDomain)pdcache.get(cs);
        if (pd == null) {

            PermissionCollection perms = getPermissions(cs);
            if (debug != null) {
            debug.println(" getPermissions "+ cs);
            debug.println("  "+perms);
            debug.println("");
            }
            pd = new ProtectionDomain(cs, perms);

            if (pd != null) {
            pdcache.put(cs, pd);
            }
        }
        }
    }
    return pd;
    }

}