1 /*
   2  * Copyright (c) 1999, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.jndi.ldap;
  27 
  28 import jdk.internal.access.SharedSecrets;
  29 
  30 import java.net.MalformedURLException;
  31 import java.net.URL;
  32 import java.net.URLClassLoader;
  33 import java.security.AccessControlContext;
  34 import java.security.AccessController;
  35 import java.security.PrivilegedAction;
  36 
  37 public final class VersionHelper {
  38 
  39     private static final VersionHelper helper = new VersionHelper();
  40 
  41     /**
  42      * Determines whether classes may be loaded from an arbitrary URL code base.
  43      */
  44     private static final boolean trustURLCodebase;
  45 
  46     static {
  47         // System property to control whether classes may be loaded from an
  48         // arbitrary URL code base
  49         PrivilegedAction<String> act =
  50                 () -> System.getProperty("com.sun.jndi.ldap.object.trustURLCodebase", "false");
  51         String trust = AccessController.doPrivileged(act);
  52         trustURLCodebase = "true".equalsIgnoreCase(trust);
  53     }
  54 
  55     private VersionHelper() { }
  56 
  57     static VersionHelper getVersionHelper() {
  58         return helper;
  59     }
  60 
  61     ClassLoader getURLClassLoader(String[] url) throws MalformedURLException {
  62         ClassLoader parent = getContextClassLoader();
  63         /*
  64          * Classes may only be loaded from an arbitrary URL code base when
  65          * the system property com.sun.jndi.ldap.object.trustURLCodebase
  66          * has been set to "true".
  67          */
  68         if (url != null && trustURLCodebase) {
  69             return URLClassLoader.newInstance(getUrlArray(url), parent);
  70         } else {
  71             return parent;
  72         }
  73     }
  74 
  75     Class<?> loadClass(String className) throws ClassNotFoundException {
  76         return Class.forName(className, true, getContextClassLoader());
  77     }
  78 
  79     Thread createThread(Runnable r) {
  80         AccessControlContext acc = AccessController.getContext();
  81         // 4290486: doPrivileged is needed to create a thread in
  82         // an environment that restricts "modifyThreadGroup".
  83         PrivilegedAction<Thread> act =
  84                 () -> SharedSecrets.getJavaLangAccess().newThreadWithAcc(r, acc);
  85         return AccessController.doPrivileged(act);
  86     }
  87 
  88     private ClassLoader getContextClassLoader() {
  89         PrivilegedAction<ClassLoader> act =
  90                 Thread.currentThread()::getContextClassLoader;
  91         return AccessController.doPrivileged(act);
  92     }
  93 
  94     private static URL[] getUrlArray(String[] url) throws MalformedURLException {
  95         URL[] urlArray = new URL[url.length];
  96         for (int i = 0; i < urlArray.length; i++) {
  97             urlArray[i] = new URL(url[i]);
  98         }
  99         return urlArray;
 100     }
 101 }