Android™

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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// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    //  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.

    CkFtp2 ftp = new CkFtp2();

    ftp.put_Hostname("ftp.example.com");
    ftp.put_Username("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.put_Password("myPassword");

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

    success = ftp.Connect();
    if (success == false) {
        Log.i(TAG, ftp.lastErrorText());
        return;
        }

    Log.i(TAG, "Connected; server certificate met the requirement.");

    success = ftp.Disconnect();
    if (success == false) {
        Log.i(TAG, ftp.lastErrorText());
        return;
        }


  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}