Source for java.security.AccessController

   1: /* AccessController.java --- Access control context and permission checker
   2:    Copyright (C) 2001, 2004  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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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:    * @return 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:    * @return 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:    * @return 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:     try
 141:       {
 142:         return action.run();
 143:       }
 144:     catch (Exception e)
 145:       {
 146:         throw new PrivilegedActionException(e);
 147:       }
 148:   }
 149: 
 150:   /**
 151:    * Calls the <code>run()</code> method of the given action with as
 152:    * (initial) access control context the given context combined with the
 153:    * protection domain of the calling class. Calls to
 154:    * <code>checkPermission()</code> in the <code>run()</code> method ignore
 155:    * all earlier protection domains of classes in the call chain, but add
 156:    * checks for the protection domains given in the supplied context.
 157:    * If the <code>run()</code> method throws an exception then this method
 158:    * will wrap that exception in an <code>PrivilegedActionException</code>.
 159:    *
 160:    * @param action the <code>PrivilegedExceptionAction</code> whose
 161:    * <code>run()</code> should be be called.
 162:    * @param context the <code>AccessControlContext</code> whose protection
 163:    * domains should be added to the protection domain of the calling class.
 164:    * @return the result of the <code>action.run()</code> method.
 165:    * @exception PrivilegedActionException wrapped around any exception that
 166:    * is thrown in the <code>run()</code> method.
 167:    */
 168:   public static Object doPrivileged(PrivilegedExceptionAction action,
 169:                                     AccessControlContext context)
 170:     throws PrivilegedActionException
 171:   {
 172:     try
 173:       {
 174:         return action.run();
 175:       }
 176:     catch (Exception e)
 177:       {
 178:         throw new PrivilegedActionException(e);
 179:       }
 180:   }
 181: 
 182:   /**
 183:    * Returns the complete access control context of the current thread.
 184:    * <p>
 185:    * XXX - Should this include all the protection domains in the call chain
 186:    * or only the domains till the last <code>doPrivileged()</code> call?
 187:    * <p>
 188:    * XXX - needs native support. Currently returns an empty context.
 189:    */
 190:   public static AccessControlContext getContext()
 191:   {
 192:     // For now just return an new empty context
 193:     return new AccessControlContext(new ProtectionDomain[0]);
 194:   }
 195: }