1 /*
   2  * Copyright (c) 1999, 2014, 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 java.net.MalformedURLException;
  29 import java.net.URL;
  30 import sun.misc.SharedSecrets;
  31 import java.net.URLClassLoader;
  32 import java.security.AccessControlContext;
  33 import java.security.AccessController;
  34 import java.security.PrivilegedAction;
  35 
  36 public class VersionHelper {
  37 
  38     private static final VersionHelper helper = new VersionHelper();
  39 
  40     VersionHelper() {} // Disallow anyone from creating one of these.
  41 
  42     static VersionHelper getVersionHelper() {
  43         return helper;
  44     }
  45 
  46     ClassLoader getURLClassLoader(String[] url)
  47         throws MalformedURLException {
  48         ClassLoader parent = getContextClassLoader();
  49         /*
  50          * Classes may only be loaded from an arbitrary URL code base when
  51          * the system property com.sun.jndi.ldap.object.trustURLCodebase
  52          * has been set to "true".
  53          */
  54         if (url != null && trustURLCodebase) {
  55             return URLClassLoader.newInstance(getUrlArray(url), parent);
  56         } else {
  57             return parent;
  58         }
  59     }
  60 
  61 
  62     static protected URL[] getUrlArray(String[] url) throws MalformedURLException {
  63         URL[] urlArray = new URL[url.length];
  64         for (int i = 0; i < urlArray.length; i++) {
  65             urlArray[i] = new URL(url[i]);
  66         }
  67         return urlArray;
  68     }
  69 
  70     Class<?> loadClass(String className) throws ClassNotFoundException {
  71         return Class.forName(className, true, getContextClassLoader());
  72     }
  73 
  74     Thread createThread(Runnable r) {
  75         AccessControlContext acc = AccessController.getContext();
  76         // 4290486: doPrivileged is needed to create a thread in
  77         // an environment that restricts "modifyThreadGroup".
  78         PrivilegedAction<Thread> act =
  79                 () -> SharedSecrets.getJavaLangAccess().newThreadWithAcc(r, acc);
  80         return AccessController.doPrivileged(act);
  81     }
  82 
  83     private ClassLoader getContextClassLoader() {
  84         PrivilegedAction<ClassLoader> act =
  85                 Thread.currentThread()::getContextClassLoader;
  86         return AccessController.doPrivileged(act);
  87     }
  88 
  89     /**
  90      * Determines whether classes may be loaded from an arbitrary URL code base.
  91      */
  92     private static final boolean trustURLCodebase;
  93 
  94     static {
  95         // System property to control whether classes may be loaded from an
  96         // arbitrary URL code base
  97         PrivilegedAction<String> act =
  98                 () -> System.getProperty("com.sun.jndi.ldap.object.trustURLCodebase", "false");
  99         String trust = AccessController.doPrivileged(act);
 100         trustURLCodebase = "true".equalsIgnoreCase(trust);
 101     }
 102 }