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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import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ssh;

public class ChilkatExample {

    public static void main(String[] args) {
        // 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.

        Ssh sshJump = new Ssh();

        // Connect and authenticate to the first SSH server (the jump host).
        int sshPort = 22;
        try {
            sshJump.connect("jump.example.com", sshPort);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            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";

        try {
            sshJump.authenticatePw("jumpUser", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Connect to the target SSH server through the jump host.
        Ssh sshTarget = new Ssh();
        try {
            sshTarget.connectThroughSsh(sshJump, "target.example.com", sshPort);

            // Authenticate to the target server (separate credentials).
            sshTarget.authenticatePw("targetUser", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

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

        sshTarget.disconnect();
        sshJump.disconnect();
    }
}