PropertyPermission.java   [plain text]

/* java.util.PropertyPermission
   Copyright (C) 1999, 2000 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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package java.util;
import java.security.Permission;
import java.security.BasicPermission;
import java.security.PermissionCollection;
import java.io.ObjectStreamField;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;

/**
 * This class represents the permission to access and modify a property.<br>
 *
 * The name is the name of the property, e.g. xxx.  You can also
 * use an asterisk "*" as described in BasicPermission <br>
 *
 * The action string is a comma-separated list if keywords.  There are
 * two possible actions:
 * <dl>
 * <dt>read</dt> 
 * <dd>Allows to read the property via <code>System.getProperty</code>.</dd>
 * <dt>write</dt> 
 * <dd>Allows to write the property via <code>System.setProperty</code>.</dd>
 * </dl>
 * 
 * The action string is case insensitive (it is converted to lower case).
 *
 * @see Permission
 * @see BasicPermission
 * @author Jochen Hoenicke 
 */
public final class PropertyPermission extends BasicPermission
{
  /**
   * @serialField action String
   *   The action string.
   */
  private static final ObjectStreamField[] serialPersistentFields =
  {
    new ObjectStreamField("action", String.class)
  };

  private static final long serialVersionUID = 885438825399942851L;

  private static final int READ = 1;
  private static final int WRITE = 2;
  private transient int actions;

  private static final String actionStrings[] =
  {
    "", "read", "write", "read,write"
  };

  /**
   * Constructs a PropertyPermission witha he specified property.  Possible
   * actions are read and write.
   * @param name the name of the property.
   * @param actions the action string.
   * @exception IllegalArgumentException if name string contains an
   * illegal wildcard or actions string contains an illegal action
   */
  public PropertyPermission(String name, String actions)
  {
    super(name);
    setActions(actions.toLowerCase());
  }

  /**
   * Parse the action string and convert actions from external to internal
   * form.  This will set the internal actions field.
   * @param actions the action string.
   * @exception IllegalArgumentException if actions string contains an
   * illegal action */
  private void setActions(String actions)
  {
    this.actions = 0;
    StringTokenizer actionTokenizer = new StringTokenizer(actions, ",");
    while (actionTokenizer.hasMoreElements())
      {
	String anAction = actionTokenizer.nextToken();
	if ("read".equals(anAction))
	  this.actions |= READ;
	else if ("write".equals(anAction))
	  this.actions |= WRITE;
	else
	  throw new IllegalArgumentException("illegal action " + anAction);
      }
  }

  /**
   * Check if this permission implies p.  This returns true iff all of
   * the following conditions are true:
   * <ul>
   * <li> p is a PropertyPermission </li>
   * <li> this.getName() implies p.getName(),  
   *  e.g. <code>java.*</code> implies <code>java.home</code> </li>
   * <li> this.getActions is a subset of p.getActions </li>
   * </ul>
   */
  public boolean implies(Permission p)
  {
    if (!(p instanceof PropertyPermission))
      return false;

    // We have to check the actions.
    PropertyPermission pp = (PropertyPermission) p;
    if ((pp.actions & ~actions) != 0)
      return false;

    // BasicPermission checks for name.
    if (!super.implies(p))
      return false;

    return true;
  }

  /**
   * Returns the action string.  Note that this may differ from the string
   * given at the constructor:  The actions are converted to lowercase and
   * may be reordered.
   */
  public String getActions()
  {
    return actionStrings[actions];
  }

  /**
   * Check to see whether this object is the same as another
   * PropertyPermission object.
   *
   * @param obj The other object
   */
  public boolean equals (Object obj)
  {
    if (! (obj instanceof PropertyPermission))
      return false;
    PropertyPermission p = (PropertyPermission) obj;
    return actions == p.actions && super.equals (p);
  }

  /**
   * Reads an object from the stream. This converts the external to the
   * internal representation.
   */
  private void readObject(ObjectInputStream s)
    throws IOException, ClassNotFoundException
  {
    ObjectInputStream.GetField fields = s.readFields();
    setActions((String) fields.get("actions", null));
  }

  /**
   * Writes an object to the stream. This converts the internal to the
   * external representation.
   */
  private void writeObject(ObjectOutputStream s) throws IOException
  {
    ObjectOutputStream.PutField fields = s.putFields();
    fields.put("actions", getActions());
    s.writeFields();
  }

  /**
   * Returns a permission collection suitable to take
   * PropertyPermission objects.
   * @return a new empty PermissionCollection.  
   */
  public PermissionCollection newPermissionCollection()
  {
    return new PermissionCollection()
    {
      Hashtable permissions = new Hashtable();
      int allActions = 0;

      public void add(Permission permission)
      {
	if (isReadOnly())
	  throw new IllegalStateException("readonly");

	// also check that permission is of correct type.
	PropertyPermission pp = (PropertyPermission) permission;
	String name = pp.getName();
	if (name.equals("*"))
	  allActions |= pp.actions;
	permissions.put(name, pp);
      }

      public boolean implies(Permission permission)
      {
	if (!(permission instanceof PropertyPermission))
	  return false;

	PropertyPermission toImply = (PropertyPermission) permission;
	if ((toImply.actions & ~allActions) == 0)
	  return true;

	String name = toImply.getName();
	if (name.equals("*"))
	  return false;

	int prefixLength = name.length();
	if (name.endsWith("*"))
	  prefixLength -= 2;

	while (true)
	  {
	    PropertyPermission forName =
	      (PropertyPermission) permissions.get(name);
	    if (forName != null && (toImply.actions & ~forName.actions) == 0)
	      return true;

	    prefixLength = name.lastIndexOf('.', prefixLength);
	    if (prefixLength < 0)
	      return false;
	    name = name.substring(0, prefixLength + 1) + '*';
	  }
      }

      public Enumeration elements()
      {
	return permissions.elements();
      }
    };
  }
}