libjava/java/security/AccessController.java

   1 /* AccessController.java --- Access control context and permission checker
   2    Copyright (C) 2001 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.security;
  39
  40 /**
  41  * Access control context and permission checker.
  42  * Can check permissions in the access control context of the current thread
  43  * through the <code>checkPermission()</code> method.
  44  * Manipulates the access control context for code that needs to be executed
  45  * the protection domain of the calling class (by explicitly ignoring the
  46  * context of the calling code) in the <code>doPrivileged()</code> methods.
  47  * And provides a <code>getContext()</code> method which gives the access
  48  * control context of the current thread that can be used for checking
  49  * permissions at a later time and/or in another thread.
  50  * <p>
  51  * XXX - Mostly a stub implementation at the moment. Needs native support
  52  * from the VM to function correctly. XXX - Do not forget to think about
  53  * how to handle <code>java.lang.reflect.Method.invoke()</code> on the
  54  * <code>doPrivileged()</code> methods.
  55  *
  56  * @author Mark Wielaard (mark@klomp.org)
  57  * @since 1.2
  58  */
  59 public final class AccessController
  60 {
  61   /**
  62    * This class only has static methods so there is no public contructor.
  63    */
  64   private AccessController()
  65   {
  66   }
  67
  68   /**
  69    * Checks wether the access control context of the current thread allows
  70    * the given Permission. Throws an <code>AccessControlException</code>
  71    * when the permission is not allowed in the current context. Otherwise
  72    * returns silently without throwing an exception.
  73    *
  74    * @param perm the permission to be checked.
  75    * @exception AccessControlException thrown if the current context does not
  76    * allow the given permission.
  77    */
  78   public static void checkPermission(Permission perm)
  79     throws AccessControlException
  80   {
  81     getContext().checkPermission(perm);
  82   }
  83
  84   /**
  85    * Calls the <code>run()</code> method of the given action with as
  86    * (initial) access control context only the protection domain of the
  87    * calling class. Calls to <code>checkPermission()</code> in the
  88    * <code>run()</code> method ignore all earlier protection domains of
  89    * classes in the call chain. Note that the protection domains of classes
  90    * called by the code in the <code>run()</code> method are not ignored.
  91    *
  92    * @param action the <code>PrivilegedAction</code> whose <code>run()</code>
  93    * should be be called.
  94    * @returns the result of the <code>action.run()</code> method.
  95    */
  96   public static Object doPrivileged(PrivilegedAction action)
  97   {
  98     return action.run();
  99   }
 100
 101   /**
 102    * Calls the <code>run()</code> method of the given action with as
 103    * (initial) access control context the given context combined with the
 104    * protection domain of the calling class. Calls to
 105    * <code>checkPermission()</code> in the <code>run()</code> method ignore
 106    * all earlier protection domains of classes in the call chain, but add
 107    * checks for the protection domains given in the supplied context.
 108    *
 109    * @param action the <code>PrivilegedAction</code> whose <code>run()</code>
 110    * should be be called.
 111    * @param context the <code>AccessControlContext</code> whose protection
 112    * domains should be added to the protection domain of the calling class.
 113    * @returns the result of the <code>action.run()</code> method.
 114    */
 115   public static Object doPrivileged(PrivilegedAction action,
 116                                     AccessControlContext context)
 117   {
 118     return action.run();
 119   }
 120
 121   /**
 122    * Calls the <code>run()</code> method of the given action with as
 123    * (initial) access control context only the protection domain of the
 124    * calling class. Calls to <code>checkPermission()</code> in the
 125    * <code>run()</code> method ignore all earlier protection domains of
 126    * classes in the call chain. Note that the protection domains of classes
 127    * called by the code in the <code>run()</code> method are not ignored.
 128    * If the <code>run()</code> method throws an exception then this method
 129    * will wrap that exception in an <code>PrivilegedActionException</code>.
 130    *
 131    * @param action the <code>PrivilegedExceptionAction</code> whose
 132    * <code>run()</code> should be be called.
 133    * @returns the result of the <code>action.run()</code> method.
 134    * @exception PrivilegedActionException wrapped around any exception that
 135    * is thrown in the <code>run()</code> method.
 136    */
 137   public static Object doPrivileged(PrivilegedExceptionAction action)
 138     throws PrivilegedActionException
 139   {
 140
 141     try
 142       {
 143         return action.run();
 144       }
 145     catch (Exception e)
 146       {
 147         throw new PrivilegedActionException(e);
 148       }
 149   }
 150
 151   /**
 152    * Calls the <code>run()</code> method of the given action with as
 153    * (initial) access control context the given context combined with the
 154    * protection domain of the calling class. Calls to
 155    * <code>checkPermission()</code> in the <code>run()</code> method ignore
 156    * all earlier protection domains of classes in the call chain, but add
 157    * checks for the protection domains given in the supplied context.
 158    * If the <code>run()</code> method throws an exception then this method
 159    * will wrap that exception in an <code>PrivilegedActionException</code>.
 160    *
 161    * @param action the <code>PrivilegedExceptionAction</code> whose
 162    * <code>run()</code> should be be called.
 163    * @param context the <code>AccessControlContext</code> whose protection
 164    * domains should be added to the protection domain of the calling class.
 165    * @returns the result of the <code>action.run()</code> method.
 166    * @exception PrivilegedActionException wrapped around any exception that
 167    * is thrown in the <code>run()</code> method.
 168    */
 169   public static Object doPrivileged(PrivilegedExceptionAction action,
 170                                     AccessControlContext context)
 171     throws PrivilegedActionException
 172   {
 173
 174     try
 175       {
 176         return action.run();
 177       }
 178     catch (Exception e)
 179       {
 180         throw new PrivilegedActionException(e);
 181       }
 182   }
 183
 184   /**
 185    * Returns the complete access control context of the current thread.
 186    * <p>
 187    * XXX - Should this include all the protection domains in the call chain
 188    * or only the domains till the last <code>doPrivileged()</code> call?
 189    * <p>
 190    * XXX - needs native support. Currently returns an empty context.
 191    */
 192   public static AccessControlContext getContext()
 193   {
 194     // For now just return an new empty context
 195     return new AccessControlContext(new ProtectionDomain[0]);
 196   }
 197 }