1 /*
   2  * Copyright (c) 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 java.security.AccessController;
  29 import java.security.PrivilegedAction;
  30 import java.util.*;
  31 import javax.naming.NamingException;
  32 import javax.naming.ldap.spi.LdapDnsProvider;
  33 import javax.naming.ldap.spi.LdapDnsProviderResult;
  34 import sun.security.util.SecurityConstants;
  35 
  36 /**
  37  * The {@code LdapDnsProviderService} is responsible for creating and providing
  38  * access to the registered {@code LdapDnsProvider}s. The {@link ServiceLoader}
  39  * is used to find and register any implementations of {@link LdapDnsProvider}.
  40  */
  41 final class LdapDnsProviderService {
  42 
  43     private static volatile LdapDnsProviderService service;
  44     private static final Object LOCK = new int[0];
  45     private final ServiceLoader<LdapDnsProvider> providers;
  46 
  47     /**
  48      * Creates a new instance of LdapDnsProviderService
  49      */
  50     private LdapDnsProviderService() {
  51         SecurityManager sm = System.getSecurityManager();
  52         if (sm == null) {
  53             providers = ServiceLoader.load(
  54                     LdapDnsProvider.class,
  55                     ClassLoader.getSystemClassLoader());
  56         } else {
  57             final PrivilegedAction<ServiceLoader<LdapDnsProvider>> pa =
  58                     () -> ServiceLoader.load(
  59                             LdapDnsProvider.class,
  60                             ClassLoader.getSystemClassLoader());
  61 
  62             providers = AccessController.doPrivileged(
  63                 pa,
  64                 null,
  65                 new RuntimePermission("ldapDnsProvider"),
  66                 SecurityConstants.GET_CLASSLOADER_PERMISSION);
  67         }
  68     }
  69 
  70     /**
  71      * Retrieve the singleton static instance of LdapDnsProviderService.
  72      */
  73     static LdapDnsProviderService getInstance() {
  74         if (service != null) return service;
  75         synchronized(LOCK) {
  76             if (service != null) return service;
  77             service = new LdapDnsProviderService();
  78         }
  79         return service;
  80     }
  81 
  82     /**
  83      * Retrieve result from the first provider that successfully resolves
  84      * the endpoints. If no results are found when calling installed
  85      * subclasses of {@code LdapDnsProvider} then this method will fall back
  86      * to the {@code DefaultLdapDnsProvider}.
  87      *
  88      * @throws NamingException if the {@code url} in not valid or an error
  89      *                         occurred while performing the lookup.
  90      */
  91     LdapDnsProviderResult lookupEndpoints(String url, Hashtable<?,?> env)
  92         throws NamingException
  93     {
  94         Iterator<LdapDnsProvider> iterator = providers.iterator();
  95         Hashtable<?, ?> envCopy = new Hashtable<>(env);
  96         LdapDnsProviderResult result = null;
  97 
  98         while (result == null && iterator.hasNext()) {
  99             result = iterator.next().lookupEndpoints(url, envCopy)
 100                     .filter(r -> r.getEndpoints().size() > 0)
 101                     .orElse(null);
 102         }
 103 
 104         if (result == null) {
 105             return new DefaultLdapDnsProvider().lookupEndpoints(url, env)
 106                 .orElse(new LdapDnsProviderResult("", List.of()));
 107         }
 108         return result;
 109     }
 110 
 111 }