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package org.apache.velocity.util.introspection;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import org.slf4j.Logger;
import java.lang.reflect.Method;
/**
* <p>Prevent "dangerous" classloader/reflection related calls. Use this
* introspector for situations in which template writers are numerous
* or untrusted. Specifically, this introspector prevents creation of
* arbitrary objects and prevents reflection on objects.
*
* <p>See documentation of checkObjectExecutePermission() for
* more information on specific classes and methods blocked.
*
* @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a>
* @version $Id$
* @since 1.5
*/
public class SecureIntrospectorImpl extends Introspector implements SecureIntrospectorControl
{
private String[] badClasses;
private String[] badPackages;
public SecureIntrospectorImpl(String[] badClasses, String[] badPackages, Logger log)
{
super(log);
this.badClasses = badClasses;
this.badPackages = badPackages;
}
/**
* Get the Method object corresponding to the given class, name and parameters.
* Will check for appropriate execute permissions and return null if the method
* is not allowed to be executed.
*
* @param clazz Class on which method will be called
* @param methodName Name of method to be called
* @param params array of parameters to method
* @return Method object retrieved by Introspector
* @throws IllegalArgumentException The parameter passed in were incorrect.
*/
public Method getMethod(Class clazz, String methodName, Object[] params)
throws IllegalArgumentException
{
if (!checkObjectExecutePermission(clazz, methodName))
{
log.warn("Cannot retrieve method {} from object of class {} due to security restrictions."
, methodName, clazz.getName());
return null;
}
else
{
return super.getMethod(clazz, methodName, params);
}
}
/**
* Determine which methods and classes to prevent from executing. Always blocks
* methods wait() and notify(). Always allows methods on Number, Boolean, and String.
* Prohibits method calls on classes related to reflection and system operations.
* For the complete list, see the properties <code>introspector.restrict.classes</code>
* and <code>introspector.restrict.packages</code>.
*
* @param clazz Class on which method will be called
* @param methodName Name of method to be called
* @see org.apache.velocity.util.introspection.SecureIntrospectorControl#checkObjectExecutePermission(java.lang.Class, java.lang.String)
*/
public boolean checkObjectExecutePermission(Class clazz, String methodName)
{
/**
* check for wait and notify
*/
if (methodName != null &&
(methodName.equals("wait") || methodName.equals("notify")) )
{
return false;
}
/**
* Always allow the most common classes - Number, Boolean and String
*/
else if (Number.class.isAssignableFrom(clazz))
{
return true;
}
else if (Boolean.class.isAssignableFrom(clazz))
{
return true;
}
else if (String.class.isAssignableFrom(clazz))
{
return true;
}
/**
* Always allow Class.getName()
*/
else if (Class.class.isAssignableFrom(clazz) &&
(methodName != null) && methodName.equals("getName"))
{
return true;
}
/**
* check the classname (minus any array info)
* whether it matches disallowed classes or packages
*/
String className = clazz.getName();
if (className.startsWith("[L") && className.endsWith(";"))
{
className = className.substring(2, className.length() - 1);
}
int dotPos = className.lastIndexOf('.');
String packageName = (dotPos == -1) ? "" : className.substring(0, dotPos);
for (String badPackage : badPackages)
{
if (packageName.equals(badPackage))
{
return false;
}
}
for (String badClass : badClasses)
{
if (className.equals(badClass))
{
return false;
}
}
return true;
}
}
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