通过 JSch 进行 SSH 隧道

jsch 上的代理设置允许您连接到远程端正在运行的代理服务器。远程端的 不会被视为代理。您需要做的是建立一个本地端口，转发到要通过隧道传输到的计算机上的 ssh 端口，然后使用 api 建立与此系统的辅助 ssh 连接。SOCKSsshdSOCKS

我以你的例子为例，并稍微重写了它来实现这一点：

import com.jcraft.jsch.*;
import java.io.*;

public class JschExecutor2 {

    public static void main(String[] args){
        JschExecutor2 t=new JschExecutor2();
        try{
            t.go();
        } catch(Exception ex){
            ex.printStackTrace();
        }
    }

    public void go() throws Exception{

        StringBuilder outputBuffer = new StringBuilder();

        String host="firstsystem"; // First level target
        String user="username";
        String password="firstlevelpassword";
        String tunnelRemoteHost="secondlevelhost"; // The host of the second target
        String secondPassword="targetsystempassword";
        int port=22;


        JSch jsch=new JSch();
        Session session=jsch.getSession(user, host, port);
        session.setPassword(password);
        localUserInfo lui=new localUserInfo();
        session.setUserInfo(lui);
        session.setConfig("StrictHostKeyChecking", "no");
        // create port from 2233 on local system to port 22 on tunnelRemoteHost
        session.setPortForwardingL(2233, tunnelRemoteHost, 22);
        session.connect();
        session.openChannel("direct-tcpip");

        // create a session connected to port 2233 on the local host.
        Session secondSession = jsch.getSession(user, "localhost", 2233);
        secondSession.setPassword(secondPassword);
        secondSession.setUserInfo(lui);
        secondSession.setConfig("StrictHostKeyChecking", "no");

        secondSession.connect(); // now we're connected to the secondary system
        Channel channel=secondSession.openChannel("exec");
        ((ChannelExec)channel).setCommand("hostname");

        channel.setInputStream(null);

        InputStream stdout=channel.getInputStream();

        channel.connect();

        while (true) {
            byte[] tmpArray=new byte[1024];
            while(stdout.available() > 0){
                int i=stdout.read(tmpArray, 0, 1024);
                if(i<0)break;
                outputBuffer.append(new String(tmpArray, 0, i));
             }
            if(channel.isClosed()){
                System.out.println("exit-status: "+channel.getExitStatus());
                break;
             }
        }
        stdout.close();

        channel.disconnect();

        secondSession.disconnect();
        session.disconnect();

        System.out.print(outputBuffer.toString());
    }

  class localUserInfo implements UserInfo{
    String passwd;
    public String getPassword(){ return passwd; }
    public boolean promptYesNo(String str){return true;}
    public String getPassphrase(){ return null; }
    public boolean promptPassphrase(String message){return true; }
    public boolean promptPassword(String message){return true;}
    public void showMessage(String message){}
  }

} 

此代码的作用是创建一个本地端口，该端口转发到目标系统上的 ssh 端口，然后通过它进行连接。运行 hostname 命令表明它确实在转发到的系统上运行。

这是经过测试并正常工作的。这类似于安全管道，最适合隧道

        String strSshUser = "ssh_user_name"; // SSH loging username
        String strSshPassword = "abcd1234"; // SSH login password
        String strSshHost = "your.ssh.hostname.com"; // hostname or ip or
                                                        // SSH server
        int nSshPort = 22; // remote SSH host port number
        String strRemoteHost = "your.database.hostname.com"; // hostname or
                                                                // ip of
                                                                // your
                                                                // database
                                                                // server
        int nLocalPort = 3366; // local port number use to bind SSH tunnel
        int nRemotePort = 3306; // remote port number of your database
        String strDbUser = "db_user_name"; // database loging username
        String strDbPassword = "4321dcba"; // database login password

    final JSch jsch = new JSch();
    Session session = jsch.getSession(strSshUser, strSshHost, 22);
    session.setPassword(strSshPassword);

    final Properties config = new Properties();
    config.put("StrictHostKeyChecking", "no");
    session.setConfig(config);

    session.connect();
    session.setPortForwardingL(nLocalPort, strRemoteHost, nRemotePort);