Source for java.security.SecureClassLoader

   1: /* SecureClassLoader.java --- A Secure Class Loader
   2:    Copyright (C) 1999, 2004, 2006  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: import java.util.WeakHashMap;
  41: 
  42: import java.nio.ByteBuffer;
  43: import java.util.HashMap;
  44: 
  45: /**
  46:  * A Secure Class Loader for loading classes with additional 
  47:  * support for specifying code source and permissions when
  48:  * they are retrieved by the system policy handler.
  49:  *
  50:  * @since 1.2
  51:  *
  52:  * @author Mark Benvenuto
  53:  */
  54: public class SecureClassLoader extends ClassLoader
  55: {
  56:   private final HashMap<CodeSource,ProtectionDomain> protectionDomainCache
  57:     = new HashMap<CodeSource, ProtectionDomain>();
  58: 
  59:   protected SecureClassLoader(ClassLoader parent)
  60:   {
  61:     super(parent);
  62:   }
  63: 
  64:   protected SecureClassLoader()
  65:   {
  66:   }
  67: 
  68:   /** 
  69:    * Creates a class using an array of bytes and a 
  70:    * CodeSource.
  71:    *
  72:    * @param name the name to give the class.  null if unknown.
  73:    * @param b the data representing the classfile, in classfile format.
  74:    * @param off the offset into the data where the classfile starts.
  75:    * @param len the length of the classfile data in the array.
  76:    * @param cs the CodeSource for the class or null when unknown.
  77:    *
  78:    * @return the class that was defined and optional CodeSource.
  79:    *
  80:    * @exception ClassFormatError if the byte array is not in proper classfile format.
  81:    */
  82:   protected final Class<?> defineClass(String name, byte[] b, int off, int len,
  83:                     CodeSource cs)
  84:   {
  85:     return super.defineClass(name, b, off, len, getProtectionDomain(cs));
  86:   }
  87: 
  88:   /** 
  89:    * Creates a class using an ByteBuffer and a 
  90:    * CodeSource.
  91:    *
  92:    * @param name the name to give the class.  null if unknown.
  93:    * @param b the data representing the classfile, in classfile format.
  94:    * @param cs the CodeSource for the class or null when unknown.
  95:    *
  96:    * @return the class that was defined and optional CodeSource.
  97:    *
  98:    * @exception ClassFormatError if the byte array is not in proper classfile format.
  99:    *
 100:    * @since 1.5
 101:    */
 102:   protected final Class<?> defineClass(String name, ByteBuffer b, CodeSource cs)
 103:   {
 104:     return super.defineClass(name, b, getProtectionDomain(cs));
 105:   }
 106: 
 107:   /* Lookup or create a protection domain for the CodeSource,
 108:    * if CodeSource is null it will return null. */
 109:   private ProtectionDomain getProtectionDomain(CodeSource cs)
 110:   {
 111:     ProtectionDomain protectionDomain = null;
 112:     if (cs != null)
 113:       {
 114:     synchronized (protectionDomainCache)
 115:       {
 116:         protectionDomain = (ProtectionDomain)protectionDomainCache.get(cs);
 117:       }
 118: 
 119:     if (protectionDomain == null)
 120:       {
 121:         protectionDomain 
 122:           = new ProtectionDomain(cs, getPermissions(cs), this, null);
 123:         synchronized (protectionDomainCache)
 124:           {
 125:         ProtectionDomain domain 
 126:           = (ProtectionDomain)protectionDomainCache.get(cs);
 127:         if (domain == null)
 128:           protectionDomainCache.put(cs, protectionDomain);
 129:         else
 130:           protectionDomain = domain;
 131:           }
 132:       }
 133:       }
 134:     return protectionDomain;
 135:   }
 136: 
 137:   /**
 138:    * Returns a PermissionCollection for the specified CodeSource.
 139:    * The default implementation invokes 
 140:    * java.security.Policy.getPermissions.
 141:    *
 142:    * This method is called by defineClass that takes a CodeSource
 143:    * argument to build a proper ProtectionDomain for the class
 144:    * being defined.
 145:    */
 146:   protected PermissionCollection getPermissions(CodeSource cs)
 147:   {
 148:     Policy policy = Policy.getCurrentPolicy();
 149:     return policy.getPermissions(cs);
 150:   }
 151: }