libjava/java/security/SecureClassLoader.java

   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., 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  * 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 }