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 * Copyright (c) 1997, 2015, 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.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
 * @since 1.2
 */
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
 * @spec JPMS
 */
 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);
 }
 }
}