Source for java.security.AccessControlContext

 1:  /* AccessControlContext.java --- Access Control Context Class
 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:  import java.util.HashSet;
 41: 
 42:  /**
 43:  * AccessControlContext makes system resource access decsion 
 44:  * based on permission rights. 
 45:  *
 46:  * It is used for a specific context and has only one method
 47:  * checkPermission. It is similar to AccessController except
 48:  * that it makes decsions based on the current context instead
 49:  * of the the current thread.
 50:  *
 51:  * It is created by call AccessController.getContext method.
 52:  *
 53:  * @author Mark Benvenuto
 54:  * @since 1.2
 55:  */
 56:  public final class AccessControlContext
 57: {
 58:  private final ProtectionDomain[] protectionDomains;
 59:  private final DomainCombiner combiner;
 60: 
 61:  /**
 62:  * Construct a new AccessControlContext with the specified
 63:  * ProtectionDomains. <code>context</code> must not be 
 64:  * null and duplicates will be removed.
 65:  *
 66:  * @param context The ProtectionDomains to use
 67:  */
 68:  public AccessControlContext(ProtectionDomain[] context)
 69:  {
 70:  HashSet domains = new HashSet (context.length);
 71:  for (int i = 0; i < context.length; i++)
 72:  domains.add (context[i]);
 73:  protectionDomains = (ProtectionDomain[])
 74:  domains.toArray (new ProtectionDomain[domains.size()]);
 75:  combiner = null;
 76:  }
 77: 
 78:  /**
 79:  * Construct a new AccessControlContext with the specified
 80:  * {@link ProtectionDomain}s and {@link DomainCombiner}.
 81:  *
 82:  * <p>Code calling this constructor must have a {@link
 83:  * SecurityPermission} of <i>createAccessControlContext</i>.</p>
 84:  *
 85:  * @throws SecurityException If the caller does not have permission
 86:  * to create an access control context.
 87:  * @since 1.3
 88:  */
 89:  public AccessControlContext(AccessControlContext acc,
 90:  DomainCombiner combiner)
 91:  {
 92:  AccessControlContext acc2 = null;
 93:  SecurityManager sm = System.getSecurityManager ();
 94:  if (sm != null)
 95:  {
 96:  Permission perm =
 97:  new SecurityPermission ("createAccessControlContext");
 98: 
 99:  // The default SecurityManager.checkPermission(perm) just calls 
 100:  // AccessController.checkPermission(perm) which in turn just
 101:  // calls AccessController.getContext().checkPermission(perm).
 102:  // This means AccessController.getContext() is called twice,
 103:  // once for the security check and once by us. It's a very
 104:  // expensive call (on gcj at least) so if we're using the
 105:  // default security manager we avoid this duplication.
 106:  if (sm.getClass() == SecurityManager.class)
 107:  {
 108:  acc2 = AccessController.getContext ();
 109:  acc2.checkPermission (perm);
 110:  }
 111:  else
 112:  sm.checkPermission (perm);
 113:  }
 114:  if (acc2 == null)
 115:  acc2 = AccessController.getContext ();
 116:  protectionDomains = combiner.combine (acc2.protectionDomains,
 117:  acc.protectionDomains);
 118:  this.combiner = combiner;
 119:  }
 120: 
 121:  AccessControlContext (ProtectionDomain[] domains, AccessControlContext acc,
 122:  DomainCombiner combiner)
 123:  {
 124:  protectionDomains = combiner.combine (domains, acc.protectionDomains);
 125:  this.combiner = combiner;
 126:  }
 127: 
 128:  /**
 129:  * Returns the Domain Combiner associated with the AccessControlContext
 130:  *
 131:  * @return the DomainCombiner
 132:  */
 133:  public DomainCombiner getDomainCombiner()
 134:  {
 135:  return combiner;
 136:  }
 137: 
 138:  /**
 139:  * Determines whether or not the specific permission is granted
 140:  * depending on the context it is within. 
 141:  *
 142:  * @param perm a permission to check
 143:  *
 144:  * @throws AccessControlException if the permssion is not permitted
 145:  */
 146:  public void checkPermission(Permission perm) throws AccessControlException
 147:  {
 148:  if (protectionDomains.length == 0)
 149:  throw new AccessControlException ("permission " 
 150:  + perm 
 151:  + " not granted: no protection domains");
 152: 
 153:  for (int i = 0; i < protectionDomains.length; i++)
 154:  {
 155:  final ProtectionDomain domain = protectionDomains[i];
 156:  if (!domain.implies(perm))
 157:  throw new AccessControlException ("permission " 
 158:  + perm 
 159:  + " not granted: " 
 160:  + domain 
 161:  + " does not imply it.");
 162:  }
 163:  }
 164: 
 165:  /**
 166:  * Checks if two AccessControlContexts are equal.
 167:  *
 168:  * It first checks if obj is an AccessControlContext class, and
 169:  * then checks if each ProtectionDomain matches.
 170:  *
 171:  * @param obj The object to compare this class to
 172:  *
 173:  * @return true if equal, false otherwise
 174:  */
 175:  public boolean equals(Object obj)
 176:  {
 177:  if (obj instanceof AccessControlContext)
 178:  {
 179:  AccessControlContext acc = (AccessControlContext) obj;
 180: 
 181:  if (acc.protectionDomains.length != protectionDomains.length)
 182:  return false;
 183: 
 184:  int i, j;
 185:  for (i = 0; i < protectionDomains.length; i++)
 186:  {
 187:  for (j = 0; j < acc.protectionDomains.length; j++)
 188:  {
 189:  if (acc.protectionDomains[j].equals (protectionDomains[i]))
 190:  break;
 191:  }
 192:  if (j == acc.protectionDomains.length)
 193:  return false;
 194:  }
 195:  return true;
 196:  }
 197:  return false;
 198:  }
 199: 
 200:  /**
 201:  * Computes a hash code of this class
 202:  *
 203:  * @return a hash code representing this class
 204:  */
 205:  public int hashCode()
 206:  {
 207:  int h = 0;
 208:  for (int i = 0; i < protectionDomains.length; i++)
 209:  h ^= protectionDomains[i].hashCode();
 210: 
 211:  return h;
 212:  }
 213: 
 214:  ProtectionDomain[] getProtectionDomains ()
 215:  {
 216:  return protectionDomains;
 217:  }
 218: }