AssociatedThread.java

/*
** Module   : AssociatedThread.java
** Abstract : a new thread which inherits the security context of the creating thread
**
** Copyright (c) 2011-2023, Golden Code Development Corporation.
**
** -#- -I- --Date-- -----------------------Description------------------------
** 001 GES 20111109 First version.
** 002 GES 20200204 Refactored some logic into a base class.
** 003 GBB 20230825 SecurityManager context methods calls updated.
*/

/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
** 
** Additional terms under GNU Affero GPL version 3 section 7:
** 
**   Under Section 7 of the GNU Affero GPL version 3, the following additional
**   terms apply to the works covered under the License.  These additional terms
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**   Affero GPL version 3 and may not be removed by you.
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*/

package com.goldencode.p2j.security;

/**
 * Provides a thread which automatically inherits the security context of the thread that
 * instantiates it.  This means that the SAME context is used on both the instantiating thread
 * and the new thread.  All context-local data is accessible to both threads.  When the thread
 * exits, it will automatically cleanup the context (decrementing the reference counts and so
 * forth). This makes it easy to implement additional threads which all share the same
 * context, which means they have the same rights and have the same context-local data.
 * <p>
 * <b>WARNING:</b> Be very careful using this mechanism.  Much (if not all of) the context-local
 * data may not be thread-safe.  Any data sharing between threads sharing a context must be made
 * safe by the caller. 
 */
public class AssociatedThread
extends ContextAwareThread
{
   /** Any pending security context switch or {@code null}. */
   private SecurityContext context = null;
   
   /**
    * Constructor which allows the core logic to be specified.
    *
    * @param    core
    *           The logic to execute when the thread is started.  Must not be {@code null}.
    *
    * @throws   NullPointerException
    *           If the instantiating thread has no security context or if {@code core} is
    *           {@code null}.
    */
   public AssociatedThread(Runnable core)
   throws NullPointerException
   {
      // duplicate the current context stack (which has both the initial and optionally an
      // effective context assigned)
      super(core, sm.isServer() ? SecurityContextStack.getContext().duplicate() : null);
   }
   
   /**
    * Save the given context as a pending context switch which will be
    * processed later by the key reading thread.
    *
    * @param    context
    *           The security context to switch to (if non-null).
    */
   public synchronized void setPendingContextSwitch(Object context)
   {
      if (context != null && context instanceof SecurityContext)
      {
         this.context = (SecurityContext) context;
      }
   }
   
   /**
    * Switch security contexts on the current thread if a switch is pending.
    */
   public synchronized void morphContextIfNeeded()
   {
      if (context != null)
      {
         if (sm.isServer())
         {
            try
            {
               sm.contextSm.pushContextWorker(context);
            }
            
            catch (RestrictedUseException rue)
            {
               // should not happen
            }
         }
         
         context = null;
      }
   }
}