Mega Code Archive
Lock request from going up in the classloader hierarchy
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/**
* 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 java.security.SecureClassLoader;
/**
* The FireWallClassLoader is a classloader that can block request from going up
* in the classloader hierarchy.
* <P>
* Normally, when a classloader receives a request for a resource, it will
* consult its parent class loader first for that resource. The parent class
* loader is typically the System ClassLoader. If the parent class loader cannot
* provide the requested resource, the child class loader will be consulted for
* the request. <I>Note: the parent class loader must not be confused by the
* superclass of a certain class loader (e.g. SecureClassLoader). The parent
* classloader is identified at constuction time and passed in as an constructor
* argument.</I>
* <P>
* Consulting the parent classloader first can be inconvenient for certain
* applications that want guarantees about which classloader is used to load a
* certain class. This could be because you want to be certain about where the
* resource came from, or you want to protect yourself against (other versions)
* of the same class that could be served by the System ClassLoader (e.g.
* because someone put them on the classpath or in the extensions directory).
* <P>
* For these cases, the FireWallClassLoader can be used.
*
* <PRE>
*
* System ClassLoader | FireWallClassLoader | User's ClassLoader
*
* </PRE>
*
* The FireWallClassLoader is placed between the user's class loader and the
* parent class loader. It has a set of filters that define what classes are
* allowed to go through. These filters describe (a groups of) packages, or a
* specific classes or resources that are allowed through to the parent
* classloader. Take as example this filter set:
*
* <pre>
* ["com.iona.", "javax.servlet.jsp."]
* </pre>
*
* This will allow requests to any class/resource staring with com.iona. or
* javax.servlet.jsp. through to the parent classloader and block all other
* requests.
* <P>
* A very common set of filters would be a set that allows nothing through
* except the classes used by the JDK. The {@link JDKFireWallClassLoaderFactory}
* factory class can create such FireWallClassLoader.
* <P>
* The FireWallClassLoader does not load any classes.
*/
public class FireWallClassLoader extends SecureClassLoader {
private final String[] filters;
private final String[] fnFilters;
private final String[] negativeFilters;
private final String[] negativeFNFilters;
/**
* Constructor.
*
* @param parent The Parent ClassLoader to use.
* @param fs A set of filters to let through. The filters and be either in
* package form (<CODE>org.omg.</CODE> or <CODE>org.omg.*</CODE>)
* or specify a single class (<CODE>junit.framework.TestCase</CODE>).
* <P>
* When the package form is used, all classed in all subpackages
* of this package are let trough the firewall. When the class
* form is used, the filter only lets that single class through.
* Note that when that class depends on another class, this class
* does not need to be mentioned as a filter, because if the
* originating class is loaded by the parent classloader, the
* FireWallClassLoader will not receive requests for the
* dependant class.
*/
public FireWallClassLoader(ClassLoader parent, String[] fs) {
this(parent, fs, new String[0]);
}
/**
* Constructor.
*
* @param parent The Parent ClassLoader to use.
* @param fs A set of filters to let through. The filters and be either in
* package form (<CODE>org.omg.</CODE> or <CODE>org.omg.*</CODE>)
* or specify a single class (<CODE>junit.framework.TestCase</CODE>).
* <P>
* When the package form is used, all classed in all subpackages
* of this package are let trough the firewall. When the class
* form is used, the filter only lets that single class through.
* Note that when that class depends on another class, this class
* does not need to be mentioned as a filter, because if the
* originating class is loaded by the parent classloader, the
* FireWallClassLoader will not receive requests for the
* dependant class.
* @param negativeFs List of negative filters to use. Negative filters take
* precedence over positive filters. When a class or resource is
* requested that matches a negative filter it is not let through
* the firewall even if an allowing filter would exist in the
* positive filter list.
*/
public FireWallClassLoader(ClassLoader parent, String[] fs, String[] negativeFs) {
super(parent);
this.filters = processFilters(fs);
this.negativeFilters = processFilters(negativeFs);
this.fnFilters = filters2FNFilters(this.filters);
this.negativeFNFilters = filters2FNFilters(this.negativeFilters);
boolean javaCovered = false;
if (this.filters == null) {
javaCovered = true;
} else {
for (int i = 0; i < this.filters.length; i++) {
if (this.filters[i].equals("java.")) {
javaCovered = true;
}
}
}
if (this.negativeFilters != null) {
String java = "java.";
// try all that would match java: j, ja, jav, java and java.
for (int i = java.length(); i >= 0; i--) {
for (int j = 0; j < this.negativeFilters.length; j++) {
if (negativeFilters[j].equals(java.substring(0, i))) {
javaCovered = false;
}
}
}
}
if (!javaCovered) {
throw new SecurityException("It's unsafe to construct a "
+ "FireWallClassLoader that does not let the java. "
+ "package through.");
}
}
private static String[] processFilters(String[] fs) {
if (fs == null || fs.length == 0) {
return null;
}
String[] f = new String[fs.length];
for (int i = 0; i < fs.length; i++) {
String filter = fs[i];
if (filter.endsWith("*")) {
filter = filter.substring(0, filter.length() - 1);
}
f[i] = filter;
}
return f;
}
private static String[] filters2FNFilters(String[] fs) {
if (fs == null || fs.length == 0) {
return null;
}
String[] f = new String[fs.length];
for (int i = 0; i < fs.length; i++) {
f[i] = fs[i].replace('.', '/');
}
return f;
}
protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
if (negativeFilters != null) {
for (int i = 0; i < negativeFilters.length; i++) {
if (name.startsWith(negativeFilters[i])) {
throw new ClassNotFoundException(name);
}
}
}
if (filters != null) {
for (int i = 0; i < filters.length; i++) {
if (name.startsWith(filters[i])) {
return super.loadClass(name, resolve);
}
}
} else {
return super.loadClass(name, resolve);
}
throw new ClassNotFoundException(name);
}
/*protected Class<?> findClass(String name) throws ClassNotFoundException {
if (negativeFilters != null) {
for (int i = 0; i < negativeFilters.length; i++) {
if (name.startsWith(negativeFilters[i])) {
throw new ClassNotFoundException(name);
}
}
}
if (filters != null) {
for (int i = 0; i < filters.length; i++) {
if (name.startsWith(filters[i])) {
return super.findClass(name);
}
}
} else {
return super.loadClass(name);
}
throw new ClassNotFoundException(name);
}*/
public java.net.URL getResource(String name) {
if (negativeFNFilters != null) {
for (int i = 0; i < negativeFNFilters.length; i++) {
if (name.startsWith(negativeFNFilters[i])) {
return null;
}
}
}
if (fnFilters != null) {
for (int i = 0; i < fnFilters.length; i++) {
if (name.startsWith(fnFilters[i])) {
return super.getResource(name);
}
}
} else {
return super.getResource(name);
}
return null;
}
/**
* Returns the list of filters used by this FireWallClassLoader. The list is
* a copy of the array internally used.
*
* @return The filters used.
*/
public String[] getFilters() {
if (filters == null) {
return null;
}
return (String[])filters.clone();
}
/**
* Returns the list of negative filters used by this FireWallClassLoader.
* The list is a copy of the array internally used.
*
* @return The filters used.
*/
public String[] getNegativeFilters() {
if (negativeFilters == null) {
return null;
}
return (String[])negativeFilters.clone();
}
}
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