SFTP Set Allowed SSH Algorithms

See more SFTP Examples

Demonstrates the Chilkat SFtp.SetAllowedAlgorithms method, which configures the exact set of SSH algorithms permitted for the connection. A JsonObject supplies comma-separated allow-lists for the kex, hostKey, cipher, and mac categories. It must be called before Connect.

Important: You typically should not set allowed algorithms explicitly. By default Chilkat orders algorithms according to best practices and accounts for known vulnerabilities.

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.SFtp;

public class ChilkatExample {

    public static void main(String[] args) {
        // Demonstrates the SFtp.SetAllowedAlgorithms method, which configures the exact set of SSH
        // algorithms permitted for the connection.  The only argument is a JsonObject.  It must be
        // called before Connect.
        //
        // -------------------------------------------------------------------------------------------
        // Note: You typically should NOT explicitly set allowed algorithms.
        // By default, Chilkat orders algorithms according to best practices and accounts for known
        // vulnerabilities such as the "Terrapin Attack".  Hard-coding algorithms can make an
        // application brittle over time: if a server later changes its allowed algorithms, or if you
        // connect to a different server, the client and server may fail to agree on a mutually
        // supported set.
        // -------------------------------------------------------------------------------------------

        SFtp sftp = new SFtp();

        JsonObject json = new JsonObject();

        // The algorithms supported by Chilkat, by category:
        //
        // Key-exchange:
        //   curve25519-sha256
        //   curve25519-sha256@libssh.org
        //   ecdh-sha2-nistp256
        //   ecdh-sha2-nistp384
        //   ecdh-sha2-nistp521
        //   diffie-hellman-group14-sha256
        //   diffie-hellman-group16-sha512
        //   diffie-hellman-group18-sha512
        //   diffie-hellman-group-exchange-sha256
        //   diffie-hellman-group1-sha1
        //   diffie-hellman-group14-sha1
        //   diffie-hellman-group-exchange-sha1
        //
        // Host key:
        //   ssh-ed25519
        //   ecdsa-sha2-nistp256
        //   ecdsa-sha2-nistp384
        //   ecdsa-sha2-nistp521
        //   rsa-sha2-256
        //   rsa-sha2-512
        //   ssh-rsa
        //   ssh-dss
        //
        // Cipher (encryption):
        //   chacha20-poly1305@openssh.com
        //   aes128-ctr
        //   aes256-ctr
        //   aes192-ctr
        //   aes128-cbc
        //   aes256-cbc
        //   aes192-cbc
        //   aes128-gcm@openssh.com
        //   aes256-gcm@openssh.com
        //   twofish256-cbc
        //   twofish128-cbc
        //   blowfish-cbc
        //
        // MAC (hash):
        //   hmac-sha2-256
        //   hmac-sha2-512
        //   hmac-sha2-256-etm@openssh.com
        //   hmac-sha2-512-etm@openssh.com
        //   hmac-sha1-etm@openssh.com
        //   hmac-sha1
        //   hmac-ripemd160
        //   hmac-sha1-96
        //   hmac-md5

        // List the allowed key-exchange, host-key, cipher (encryption), and mac (hash) algorithms, in
        // order of preference.
        String allowed_kex = "curve25519-sha256@libssh.org,ecdh-sha2-nistp256";
        String allowed_hostKey = "ssh-ed25519,ecdsa-sha2-nistp256";
        String allowed_cipher = "chacha20-poly1305@openssh.com,aes256-ctr";
        String allowed_mac = "hmac-sha2-256,hmac-sha2-512";

        json.updateString("kex", allowed_kex);
        json.updateString("hostKey", allowed_hostKey);
        json.updateString("cipher", allowed_cipher);
        json.updateString("mac", allowed_mac);

        // Apply the allow-list before connecting.
        try {
            sftp.setAllowedAlgorithms(json);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        int port = 22;
        try {
            sftp.connect("sftp.example.com", port);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Connected.");

        sftp.disconnect();
    }
}