Java

Require Specific FTPS Server Certificate Fields

Demonstrates the Chilkat Ftp2.SetSslCertRequirement method, which adds a required match against the FTP server certificate. The first argument selects the certificate field (such as SubjectCN or IssuerCN) and the second is the required value. It is a void method; a non-matching certificate causes the connection to fail.

Background: Standard TLS validation confirms a certificate is trusted and valid for the hostname, but it does not guarantee you reached the specific server you expect — a form of pinning closes that gap. Requiring a certificate field to match a known value rejects any certificate that does not, defending against a mis-issued or substituted certificate even if it would otherwise pass validation. Multiple requirements can be added, and all must be satisfied.

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import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ftp2;

public class ChilkatExample {

    public static void main(String[] args) {
        // Demonstrates the Ftp2.SetSslCertRequirement method, which adds a required match against the FTP
        // server certificate.  The 1st argument selects the certificate field and the 2nd is the required
        // value.  It is a void method.

        Ftp2 ftp = new Ftp2();

        ftp.setHostname("ftp.example.com");
        ftp.setUsername("myFtpLogin");

        // 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.
        ftp.setPassword("myPassword");

        // Use explicit FTPS (AUTH TLS) on the standard FTP port.
        ftp.setAuthTls(true);

        // Require that the server certificate's subject common name matches an expected value.  If the
        // presented certificate does not match, the TLS connection fails.  Supported fields include
        // SubjectDN, SubjectCN, IssuerDN, IssuerCN, and others.
        ftp.setSslCertRequirement("SubjectCN", "ftp.example.com");

        try {
            ftp.connect();
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Connected; server certificate met the requirement.");

        try {
            ftp.disconnect();
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }
    }
}