Java

SSH Tunnel Through an Outbound SOCKS Proxy

Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword properties.

Background: This is the reverse direction from dynamic forwarding: here a SOCKS proxy is used to reach the SSH server, for networks where outbound connections must pass through one. SocksVersion is the switch — 0 means no SOCKS, while 4 or 5 selects the protocol. SOCKS5 supports username/password authentication and remote DNS; SOCKS4 supports only a username.

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Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SshTunnel
    //  properties SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword.

    CkSshTunnel tunnel = new CkSshTunnel();

    //  Set SocksVersion to 4 or 5 to route the outbound connection to the SSH server through a SOCKS
    //  proxy.  A value of 0 (the default) means no SOCKS proxy.
    tunnel.put_SocksVersion(5);
    tunnel.put_SocksHostname("socks.example.com");
    tunnel.put_SocksPort(1080);

    //  SOCKS4 supports only a username; SOCKS5 supports username and password.
    tunnel.put_SocksUsername("myProxyLogin");
    tunnel.put_SocksPassword("myProxyPassword");

    tunnel.put_DestHostname("db.internal.example.com");
    tunnel.put_DestPort(5432);

    //  Connect to the SSH server through the SOCKS proxy configured above.
    int sshPort = 22;
    success = tunnel.Connect("ssh.example.com",sshPort);
    if (success == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    String password = "mySshPassword";

    success = tunnel.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    int listenPort = 1080;
    success = tunnel.BeginAccepting(listenPort);
    if (success == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    System.out.println("Tunnel established through the SOCKS proxy.");

    boolean waitForThreadExit = true;
    success = tunnel.CloseTunnel(waitForThreadExit);
    if (success == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }
  }
}