Java

Get SSH Server Authentication Methods

Demonstrates getting the authentication methods advertised by an SSH server. Connect first but do not authenticate, then call GetAuthMethods, which returns a lowercase, comma-separated list such as publickey,password,keyboard-interactive.

Important: Querying the authentication methods intentionally disconnects from the server, so reconnect before authenticating.

Background: Knowing what a server accepts lets a client choose the right authentication path rather than guessing — for example, falling back to keyboard-interactive when password authentication is not offered, or failing fast with a clear message when only public-key is allowed. It is also useful diagnostically when authentication fails for reasons that are not obvious from the error text.

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

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // Demonstrates getting the authentication methods advertised by an SSH server.

        Ssh ssh = new Ssh();

        int port = 22;

        // The server must be connected, but not yet authenticated.
        String authMethods;
        try {
            ssh.connect("ssh.example.com", port);

            // Returns a lowercase, comma-separated list, such as:
            //     publickey,password,keyboard-interactive
            authMethods = ssh.getAuthMethods();
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Authentication methods supported by this server: " + authMethods);

        // IMPORTANT: Querying the authentication methods intentionally disconnects from the server.
        // Reconnect before authenticating.
        try {
            ssh.connect("ssh.example.com", port);
        } 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 {
            ssh.authenticatePw("mySshLogin", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("SSH authentication successful.");

        ssh.disconnect();
    }
}