通過 JSch 的 SSH 隧道

Question

我的目標是連接到防火牆后面的服務器（主機）。 我可以通過連接到網絡中的另一台服務器（隧道）然后通過 SSH 連接到該服務器來訪問該服務器。 但是我無法通過 JSch 實現相同的場景。

我無法使用我為此目的編寫的以下代碼。 如果我在這里做任何愚蠢的事情，請告訴我。

public class JschExecutor {

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

        StringBuilder outputBuffer = new StringBuilder();

        String host="xxx.xxx.xxx.xxx"; // The host to be connected finally
        String user="user";
        String password="passwrd";
        int port=22;

        String tunnelRemoteHost="xx.xx.xx.xx"; // The host from where the tunnel is created

        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");

        ProxySOCKS5 proxyTunnel = new ProxySOCKS5(tunnelRemoteHost, 22);
        proxyTunnel.setUserPasswd(user, password);
        session.setProxy(proxyTunnel);

        session.connect(30000);

        Channel channel=session.openChannel("exec");
        ((ChannelExec)channel).setCommand("hostname");

        channel.setInputStream(null);
        ((ChannelExec)channel).setErrStream(System.err);

        InputStream in=channel.getInputStream();
        BufferedReader ebr = new BufferedReader(new InputStreamReader(in));

        channel.connect();

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

        channel.disconnect();

        session.disconnect();

        System.out.println(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){}
  }     

} 

上面的代碼在session.connect(30000);上給出了以下異常session.connect(30000); 線。

com.jcraft.jsch.JSchException: ProxySOCKS5: com.jcraft.jsch.JSchException: fail in SOCKS5 proxy
    at com.jcraft.jsch.ProxySOCKS5.connect(ProxySOCKS5.java:317)
    at com.jcraft.jsch.Session.connect(Session.java:231)
    at com.ukris.main.JschExecutor.go(JschExecutor.java:50)
    at com.ukris.main.JschExecutor.main(JschExecutor.java:19)
Caused by: com.jcraft.jsch.JSchException: fail in SOCKS5 proxy
    at com.jcraft.jsch.ProxySOCKS5.connect(ProxySOCKS5.java:200)
    ... 3 more

Answer 1

jsch 上的SOCKS代理設置允許您連接到遠程端正在運行的代理服務器。 遠程端的sshd不會被視為SOCKS代理。 您需要做的是建立一個本地端口轉發到您要通過隧道連接的機器上的 ssh 端口，然后使用 api 建立到該系統的輔助 ssh 連接。

我已經拿了你的例子並稍微重寫了它來完成這個：

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){}
  }

} 

這段代碼的作用是創建一個本地端口轉發到目標系統上的 ssh 端口，然后通過它進行連接。 hostname 命令的運行說明它確實在轉發到的系統上運行。

Answer 2

這已經過測試並且工作正常。 這就像安全管道一樣，最適合隧道

        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);