Source for java.security.SecureClassLoader

   1: /* SecureClassLoader.java --- A Secure Class Loader
   2:    Copyright (C) 1999, 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:  * A Secure Class Loader for loading classes with additional 
  42:  * support for specifying code source and permissions when
  43:  * they are retrieved by the system policy handler.
  44:  *
  45:  * @since 1.2
  46:  *
  47:  * @author Mark Benvenuto
  48:  */
  49: public class SecureClassLoader extends ClassLoader
  50: {
  51:   java.util.WeakHashMap protectionDomainCache = new java.util.WeakHashMap();
  52: 
  53:   protected SecureClassLoader(ClassLoader parent)
  54:   {
  55:     super(parent);
  56:     SecurityManager sm = System.getSecurityManager();
  57:     if(sm != null)
  58:       sm.checkCreateClassLoader();
  59:   }
  60: 
  61:   protected SecureClassLoader()
  62:   {
  63:     SecurityManager sm = System.getSecurityManager();
  64:     if(sm != null)
  65:       sm.checkCreateClassLoader();
  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:     if (cs != null)
  86:       {
  87:     ProtectionDomain protectionDomain;
  88:       
  89:     synchronized (protectionDomainCache)
  90:       {
  91:         protectionDomain = (ProtectionDomain)protectionDomainCache.get(cs);
  92:       }
  93: 
  94:     if (protectionDomain == null)
  95:       {
  96:         protectionDomain 
  97:           = new ProtectionDomain(cs, getPermissions(cs), this, null);
  98:         synchronized (protectionDomainCache)
  99:           {
 100:         ProtectionDomain domain 
 101:           = (ProtectionDomain)protectionDomainCache.get(cs);
 102:         if (domain == null)
 103:           protectionDomainCache.put(cs, protectionDomain);
 104:         else
 105:           protectionDomain = domain;
 106:           }
 107:       }
 108:     return super.defineClass(name, b, off, len, protectionDomain);
 109:       } 
 110:     else
 111:       return super.defineClass(name, b, off, len);
 112:   }
 113: 
 114:   /**
 115:    * Returns a PermissionCollection for the specified CodeSource.
 116:    * The default implementation invokes 
 117:    * java.security.Policy.getPermissions.
 118:    *
 119:    * This method is called by defineClass that takes a CodeSource
 120:    * arguement to build a proper ProtectionDomain for the class
 121:    * being defined.
 122:    */
 123:   protected PermissionCollection getPermissions(CodeSource cs)
 124:   {
 125:     Policy policy = Policy.getCurrentPolicy();
 126:     return policy.getPermissions(cs);
 127:   }
 128: }