The problem:
Various classes, such as Calendar, need to load Locale information from ResourceBundles. The ResourceBundle.getBundle() calls are frequent enough, eg every time a Calendar instance is created, and sometimes every time certain calls are made, that the calling-classloader check performed by getBundle can be a significant performance issue. To avoid this check, we use the 3-argument form of getBundle(), which includes an explicit ClassLoader argument.
However, getting the classloader argument for getBundle() can be a problem. Currently we use the system classloader as returned by getSystemClassLoader() (using something like Calendar.class.getClassLoader() unfortunately doesn't work because that may return "null" for the system classloader, and null is not a valid argument for getBundle() ). But, getSystemClassLoader is a privileged call and requires an AccessController.doPrivileged() to call safely in a secure environment.
Rather than having to add an AccessController.doPrivilaged() to every getBundle() call in every class that uses Locale data, I wondered if we can use a "LocaleHelper" class to cache the system classloader and simplify locale bundle lookups from the classes that need access to them.
My question is - could the LocaleHelper class be a security problem? As far as I can tell it isn't - the worst that can happen is that untrusted code could load a ResourceBundle using the system classloader, but since getBundle() itself is not a privileged call, and getBundle() is not called with elevated privileges anyway, I don't see any problems there. The code could do the same thing by calling getBundle() directly. Have I missed anything?
Bryce
/* LocaleHelper.java Copyright (C) 2004 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.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
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
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modules, and to copy and distribute the resulting executable under
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independent module, the terms and conditions of the license of that
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package gnu.java.locale;
import java.security.AccessController;
import java.security.PrivilegedAction;
import gnu.java.security.action.GetSystemClassLoaderAction;
/**
* This class provides a convienient interface to access Locale information.
*/
public class LocaleHelper
{
/** The system classloader is used to load Locale resource bundles. Passing
* this to ResourceBundle.getBundle() explicitly avoids a potentially
* expensive calling-classloader check. */
private static ClassLoader systemClassLoader;
static
{
PrivilegedAction action = new GetSystemClassLoaderAction();
systemClassLoader = (ClassLoader) AccessController.doPrivileged(action);
}
/** Retrieve LocaleInformation ResourceBundle for the given locale. */
public static ResourceBundle getLocaleInformation(Locale locale)
{
return ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
locale, systemClassLoader);
}
/** Retrieve Calendar ResourceBundle for the given locale. */
public static ResourceBundle getCalendar(Locale locale)
{
return ResourceBundle.getBundle("gnu.java.locale.Calendar",
locale, systemClassLoader);
}
}
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