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jlechner |
/* AccessController.java --- Access control context and permission checker
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Copyright (C) 2001, 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.security;
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/**
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* Access control context and permission checker.
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* Can check permissions in the access control context of the current thread
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* through the <code>checkPermission()</code> method.
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* Manipulates the access control context for code that needs to be executed
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* the protection domain of the calling class (by explicitly ignoring the
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* context of the calling code) in the <code>doPrivileged()</code> methods.
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* And provides a <code>getContext()</code> method which gives the access
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* control context of the current thread that can be used for checking
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* permissions at a later time and/or in another thread.
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* <p>
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* XXX - Mostly a stub implementation at the moment. Needs native support
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* from the VM to function correctly. XXX - Do not forget to think about
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* how to handle <code>java.lang.reflect.Method.invoke()</code> on the
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* <code>doPrivileged()</code> methods.
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*
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* @author Mark Wielaard (mark@klomp.org)
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* @since 1.2
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*/
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public final class AccessController
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{
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/**
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* This class only has static methods so there is no public contructor.
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*/
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private AccessController()
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{
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}
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/**
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* Checks wether the access control context of the current thread allows
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* the given Permission. Throws an <code>AccessControlException</code>
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* when the permission is not allowed in the current context. Otherwise
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* returns silently without throwing an exception.
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*
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* @param perm the permission to be checked.
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* @exception AccessControlException thrown if the current context does not
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* allow the given permission.
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*/
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public static void checkPermission(Permission perm)
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throws AccessControlException
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{
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getContext().checkPermission(perm);
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}
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/**
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* Calls the <code>run()</code> method of the given action with as
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* (initial) access control context only the protection domain of the
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* calling class. Calls to <code>checkPermission()</code> in the
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* <code>run()</code> method ignore all earlier protection domains of
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* classes in the call chain. Note that the protection domains of classes
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* called by the code in the <code>run()</code> method are not ignored.
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*
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* @param action the <code>PrivilegedAction</code> whose <code>run()</code>
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* should be be called.
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* @return the result of the <code>action.run()</code> method.
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*/
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public static Object doPrivileged(PrivilegedAction action)
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{
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return action.run();
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}
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/**
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* Calls the <code>run()</code> method of the given action with as
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* (initial) access control context the given context combined with the
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* protection domain of the calling class. Calls to
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* <code>checkPermission()</code> in the <code>run()</code> method ignore
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* all earlier protection domains of classes in the call chain, but add
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* checks for the protection domains given in the supplied context.
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*
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* @param action the <code>PrivilegedAction</code> whose <code>run()</code>
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* should be be called.
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* @param context the <code>AccessControlContext</code> whose protection
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* domains should be added to the protection domain of the calling class.
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* @return the result of the <code>action.run()</code> method.
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*/
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public static Object doPrivileged(PrivilegedAction action,
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AccessControlContext context)
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{
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return action.run();
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}
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/**
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* Calls the <code>run()</code> method of the given action with as
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* (initial) access control context only the protection domain of the
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* calling class. Calls to <code>checkPermission()</code> in the
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* <code>run()</code> method ignore all earlier protection domains of
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* classes in the call chain. Note that the protection domains of classes
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* called by the code in the <code>run()</code> method are not ignored.
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* If the <code>run()</code> method throws an exception then this method
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* will wrap that exception in an <code>PrivilegedActionException</code>.
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*
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* @param action the <code>PrivilegedExceptionAction</code> whose
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* <code>run()</code> should be be called.
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* @return the result of the <code>action.run()</code> method.
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* @exception PrivilegedActionException wrapped around any exception that
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* is thrown in the <code>run()</code> method.
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*/
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public static Object doPrivileged(PrivilegedExceptionAction action)
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throws PrivilegedActionException
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{
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try
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{
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return action.run();
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}
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catch (Exception e)
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{
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throw new PrivilegedActionException(e);
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}
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}
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/**
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* Calls the <code>run()</code> method of the given action with as
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* (initial) access control context the given context combined with the
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* protection domain of the calling class. Calls to
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* <code>checkPermission()</code> in the <code>run()</code> method ignore
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* all earlier protection domains of classes in the call chain, but add
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* checks for the protection domains given in the supplied context.
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* If the <code>run()</code> method throws an exception then this method
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* will wrap that exception in an <code>PrivilegedActionException</code>.
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*
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* @param action the <code>PrivilegedExceptionAction</code> whose
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* <code>run()</code> should be be called.
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* @param context the <code>AccessControlContext</code> whose protection
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* domains should be added to the protection domain of the calling class.
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* @return the result of the <code>action.run()</code> method.
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* @exception PrivilegedActionException wrapped around any exception that
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* is thrown in the <code>run()</code> method.
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*/
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public static Object doPrivileged(PrivilegedExceptionAction action,
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AccessControlContext context)
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throws PrivilegedActionException
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{
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try
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{
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return action.run();
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}
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catch (Exception e)
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{
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throw new PrivilegedActionException(e);
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}
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}
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/**
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* Returns the complete access control context of the current thread.
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* <p>
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* XXX - Should this include all the protection domains in the call chain
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* or only the domains till the last <code>doPrivileged()</code> call?
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* <p>
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* XXX - needs native support. Currently returns an empty context.
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*/
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public static AccessControlContext getContext()
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{
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// For now just return an new empty context
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return new AccessControlContext(new ProtectionDomain[0]);
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}
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}
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