Java

Connect to an SSH Server Through Another (Jump Host)

Demonstrates the Chilkat Ssh.ConnectThroughSsh method, which connects to a second SSH server through an already connected and authenticated Ssh object. The first argument is the first (jump-host) Ssh object, and the second and third are the destination hostname and port.

Background: This is SSH chaining through a "jump host" (bastion): the application connects to a reachable gateway, then tunnels onward to a target that is only accessible from inside the network. Each hop is authenticated separately with its own credentials. The result is a normal Ssh object for the target that happens to be routed through the first connection.

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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 the Ssh.ConnectThroughSsh method, which connects to a second SSH server through
    //  an already connected and authenticated Ssh object (a jump host).  The 1st argument is the
    //  first Ssh object, and the 2nd and 3rd are the destination hostname and port.

    CkSsh sshJump = new CkSsh();

    //  Connect and authenticate to the first SSH server (the jump host).
    int sshPort = 22;
    success = sshJump.Connect("jump.example.com",sshPort);
    if (success == false) {
        System.out.println(sshJump.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 = sshJump.AuthenticatePw("jumpUser",password);
    if (success == false) {
        System.out.println(sshJump.lastErrorText());
        return;
        }

    //  Connect to the target SSH server through the jump host.
    CkSsh sshTarget = new CkSsh();
    success = sshTarget.ConnectThroughSsh(sshJump,"target.example.com",sshPort);
    if (success == false) {
        System.out.println(sshTarget.lastErrorText());
        return;
        }

    //  Authenticate to the target server (separate credentials).
    success = sshTarget.AuthenticatePw("targetUser",password);
    if (success == false) {
        System.out.println(sshTarget.lastErrorText());
        return;
        }

    System.out.println("Connected to the target through the jump host.");

    sshTarget.Disconnect();
    sshJump.Disconnect();
  }
}