Java

SSH Through a SOCKS Proxy

Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy. Set the SOCKS properties before calling Connect, and set SocksVersion to match the proxy server.

Background: SOCKS is a general-purpose TCP relay, so unlike an HTTP proxy it is designed from the start to carry arbitrary protocols — usually the smoother option for SSH. The version matters: SOCKS4 supports only a username with no password, while SOCKS5 supports full login/password authentication as well as IPv6 and remote DNS resolution. Note this is the inverse of dynamic port forwarding: here a SOCKS proxy is used to reach the SSH server, rather than SSH providing a SOCKS proxy.

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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;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy.

    CkSsh ssh = new CkSsh();

    //  Set the SOCKS proxy properties before connecting.  The hostname may be a domain name or an
    //  IP address.
    ssh.put_SocksHostname("socks.example.com");
    ssh.put_SocksPort(1080);
    ssh.put_SocksUsername("mySocksLogin");
    ssh.put_SocksPassword("mySocksPassword");

    //  Set the version to match the proxy server: 4 or 5.
    //  Note: SOCKS4 supports only a username, with no password.  SOCKS5 supports full
    //  login/password authentication.
    ssh.put_SocksVersion(5);

    String hostname = "ssh.example.com";
    int port = 22;
    success = ssh.Connect(hostname,port);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    System.out.println("Connected to the SSH server through the SOCKS proxy.");

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

    //  ... use the SSH connection normally ...

    ssh.Disconnect();
  }
}