/*

 * 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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.security;

import java.util.HashMap;

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.

 *

 * @author  Li Gong

 * @author  Roland Schemers

 */

public class SecureClassLoader extends ClassLoader {

    /*

     * If initialization succeed this is set to true and security checks will

     * succeed. Otherwise the object is not initialized and the object is

     * useless.

     */

    // HashMap that maps CodeSource to ProtectionDomain

                        new HashMap<CodeSource, ProtectionDomain>(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.

     * <p>

     * @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();

        }

        initialized = true;

    }

    /**

     * 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();

        }

        initialized = true;

    }

    /**

     * 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.

     * <p>

     * If a non-null CodeSource is supplied a ProtectionDomain is

     * constructed and associated with the class being defined.

     * <p>

     * @param      name the expected name of the class, or <code>null</code>

     *                  if not known, using '.' and not '/' as the separator

     *                  and without a trailing ".class" suffix.

     * @param      b    the bytes that make up the class data. The bytes in

     *             positions <code>off</code> through <code>off+len-1</code>

     *             should have the format of a valid class file as defined

     *             by the

     *             <a href="http://java.sun.com/docs/books/vmspec/">Java

     *             Virtual Machine Specification</a>.

     * @param      off  the start offset in <code>b</code> of the class data

     * @param      len  the length of the class data

     * @param      cs   the associated CodeSource, or <code>null</code> if none

     * @return the <code>Class</code> object created from the data,

     *         and optional CodeSource.

     * @exception  ClassFormatError if the data did not contain a valid class

     * @exception  IndexOutOfBoundsException if either <code>off</code> or

     *             <code>len</code> is negative, or if

     *             <code>off+len</code> is greater than <code>b.length</code>.

     *

     * @exception  SecurityException if an attempt is made to add this class

     *             to a package that contains classes that were signed by

     *             a different set of certificates than this class, or if

     *             the class name begins with "java.".

     */

    protected final Class<?> defineClass(String name,

                                         byte[] b, int off, int len,

                                         CodeSource cs)

    {

    }

    /**

     * Converts a {@link java.nio.ByteBuffer <tt>ByteBuffer</tt>}

     * into an instance of class <tt>Class</tt>, with an optional CodeSource.

     * Before the class can be used it must be resolved.

     * <p>

     * If a non-null CodeSource is supplied a ProtectionDomain is

     * constructed and associated with the class being defined.

     * <p>

     * @param      name the expected name of the class, or <code>null</code>

     *                  if not known, using '.' and not '/' as the separator

     *                  and without a trailing ".class" suffix.

     * @param      b    the bytes that make up the class data.  The bytes from positions

     *                  <tt>b.position()</tt> through <tt>b.position() + b.limit() -1</tt>

     *                  should have the format of a valid class file as defined by the

     *                  <a href="http://java.sun.com/docs/books/vmspec/">Java Virtual

     *                  Machine Specification</a>.

     * @param      cs   the associated CodeSource, or <code>null</code> if none

     * @return the <code>Class</code> object created from the data,

     *         and optional CodeSource.

     * @exception  ClassFormatError if the data did not contain a valid class

     * @exception  SecurityException if an attempt is made to add this class

     *             to a package that contains classes that were signed by

     *             a different set of certificates than this class, or if

     *             the class name begins with "java.".

     *

     * @since  1.5

     */

    protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,

                                         CodeSource cs)

    {

    }

    /**

     * Returns the permissions for the given CodeSource object.

     * <p>

     * This method is invoked by the defineClass method which 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)

    {

        check();

        return new Permissions(); // ProtectionDomain defers the binding

    }

    /*

     * Returned cached ProtectionDomain for the specified CodeSource.

     */

    private ProtectionDomain getProtectionDomain(CodeSource cs) {

        if (cs == null)

            return null;

        ProtectionDomain pd = null;

        synchronized (pdcache) {

            pd = pdcache.get(cs);

            if (pd == null) {

                PermissionCollection perms = getPermissions(cs);

                pd = new ProtectionDomain(cs, perms, this, null);

                }

            }

        }

        return pd;

    }

    /*

     * Check to make sure the class loader has been initialized.

     */

    private void check() {

        if (!initialized) {

            throw new SecurityException("ClassLoader object not initialized");

        }

    }

}