/*

 * Copyright (c) 1997, 2015, 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

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 */

package java.security;

import java.util.Map;

import java.util.Objects;

import java.util.concurrent.ConcurrentHashMap;

import java.util.function.Function;

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;

    /*

     * Map that maps the CodeSource to a ProtectionDomain. The key is a

     * CodeSourceKey class that uses a String instead of a URL to avoid

     * potential expensive name service lookups. This does mean that URLs that

     * are equivalent after nameservice lookup will be placed in separate

     * ProtectionDomains; however during policy enforcement these URLs will be

     * canonicalized and resolved resulting in a consistent set of granted

     * permissions.

     */

    private final Map<CodeSourceKey, ProtectionDomain> pdcache

            = new ConcurrentHashMap<>(11);

    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.

     *

     * @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;

    }

    /**

     * Creates a new {@code SecureClassLoader} of the specified name and

     * using the specified parent class loader for delegation.

     *

     * @param name class loader name; or {@code null} if not named

     * @param parent the parent class loader

     *

     * @throws IllegalArgumentException if the given name is empty.

     *

     * @throws SecurityException  if a security manager exists and its

     *         {@link SecurityManager#checkCreateClassLoader()} method

     *         doesn't allow creation of a class loader.

     *

     * @since 9

     */

    protected SecureClassLoader(String name, ClassLoader parent) {

        super(name, parent);

        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.

     *

     * @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.

     *

     * @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.

     *

     * @param codesource the codesource.

     *

     * @return the permissions granted to the codesource.

     *

     */

    protected PermissionCollection getPermissions(CodeSource codesource)

    {

        check();

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

    }

    /*

     * holder class for the static field "debug" to delay its initialization

     */

    private static class DebugHolder {

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

    }

    /*

     * Returned cached ProtectionDomain for the specified CodeSource.

     */

    private ProtectionDomain getProtectionDomain(CodeSource cs) {

        if (cs == null) {

            return null;

        }

        // Use a CodeSourceKey object key. It should behave in the

        // same manner as the CodeSource when compared for equality except

        // that no nameservice lookup is done on the hostname (String comparison

        // only), and the fragment is not considered.

        CodeSourceKey key = new CodeSourceKey(cs);

        return pdcache.computeIfAbsent(key, new Function<>() {

            @Override

            public ProtectionDomain apply(CodeSourceKey key /* not used */) {

                PermissionCollection perms

                        = SecureClassLoader.this.getPermissions(cs);

                ProtectionDomain pd = new ProtectionDomain(

                        cs, perms, SecureClassLoader.this, null);

                if (DebugHolder.debug != null) {

                    DebugHolder.debug.println(" getPermissions " + pd);

                    DebugHolder.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");

        }

    }

    private static class CodeSourceKey {

        private final CodeSource cs;

        CodeSourceKey(CodeSource cs) {

            this.cs = cs;

        }

        @Override

        public int hashCode() {

            String locationNoFrag = cs.getLocationNoFragString();

            return locationNoFrag != null ? locationNoFrag.hashCode() : 0;

        }

        @Override

        public boolean equals(Object obj) {

            if (obj == this) {

                return true;

            }

            if (!(obj instanceof CodeSourceKey)) {

                return false;

            }

            CodeSourceKey csk = (CodeSourceKey) obj;

            if (!Objects.equals(cs.getLocationNoFragString(),

                                csk.cs.getLocationNoFragString())) {

                return false;

            }

            return cs.matchCerts(csk.cs, true);

        }

    }

}