/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

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.
 */
 private final boolean initialized;

 // HashMap that maps CodeSource to ProtectionDomain
 // @GuardedBy("pdcache")
 private final HashMap<CodeSource, ProtectionDomain> pdcache =
 new HashMap<>(11);

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

 static {
 ClassLoader.registerAsParallelCapable();
 }

 /**
 * 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}
 * 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} 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}
 * method to ensure creation of a class loader is allowed.
 *
 * @exception SecurityException if a security manager exists and its
 * {@code checkCreateClassLoader} 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}
 * 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} through {@code off+len-1}
 * should have the format of a valid class file as defined by
 * <cite>The Java&trade; Virtual Machine Specification</cite>.
 * @param off the start offset in {@code b} of the class data
 * @param len the length of the class data
 * @param cs the associated CodeSource, or {@code null} if none
 * @return the {@code Class} 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} or
 * {@code len} is negative, or if
 * {@code off+len} is greater than {@code b.length}.
 *
 * @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)
 {
 return defineClass(name, b, off, len, getProtectionDomain(cs));
 }

 /**
 * Converts a {@link java.nio.ByteBuffer ByteBuffer}
 * into an instance of class {@code 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}
 * 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
 * {@code b.position()} through {@code b.position() + b.limit() -1}
 * should have the format of a valid class file as defined by
 * <cite>The Java&trade; Virtual Machine Specification</cite>.
 * @param cs the associated CodeSource, or {@code null} if none
 * @return the {@code Class} 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)
 {
 return defineClass(name, b, getProtectionDomain(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);
 pdcache.put(cs, pd);
 if (debug != null) {
 debug.println(" getPermissions "+ pd);
 debug.println("");
 }
 }
 }
 return pd;
 }

 /*
 * Check to make sure the class loader has been initialized.
 */
 private void check() {
 if (!initialized) {
 throw new SecurityException("ClassLoader object not initialized");
 }
 }

}