Get and Inspect the FTPS Server Certificate Before Login

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Demonstrates the Chilkat Ftp2.GetServerCert method, which loads the leaf certificate presented on the connected FTPS control channel into a Cert object. The only argument is the Cert; an active TLS control connection is required. This example uses ConnectOnly followed by LoginAfterConnectOnly so the certificate can be inspected before any credentials are sent.

// 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.GetServerCert method, which loads the leaf certificate presented on the
    //  connected FTPS control channel into a Cert object.  The only argument is the Cert.  It requires
    //  an active TLS control connection.
    //  
    //  This example uses ConnectOnly + LoginAfterConnectOnly so the server certificate can be
    //  inspected and validated BEFORE any credentials are sent.

    CkFtp2 ftp = new CkFtp2();

    ftp.put_Hostname("ftp.example.com");

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

    //  Establish the connection and TLS layer and receive the greeting, but do NOT send USER/PASS.
    success = ftp.ConnectOnly();
    if (success == false) {
        Log.i(TAG, ftp.lastErrorText());
        return;
        }

    //  The TLS control channel is now up.  Retrieve the server's certificate for inspection.
    CkCert cert = new CkCert();
    success = ftp.GetServerCert(cert);
    if (success == false) {
        Log.i(TAG, ftp.lastErrorText());
        return;
        }

    Log.i(TAG, "Server certificate subject: " + cert.subjectCN());
    Log.i(TAG, "Issued by: " + cert.issuerCN());

    //  Perform any application-specific validation of the server certificate here -- for example,
    //  compare the fingerprint or subject against an expected value.  Only proceed to authenticate if
    //  the certificate is acceptable.  Because no credentials have been sent yet, an untrusted server
    //  never sees the username or password.
    //  
    //    if (certificate is not acceptable) { return; }

    //  The certificate passed inspection, so now provide credentials and authenticate.
    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");

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

    Log.i(TAG, "Authenticated after verifying the server certificate.");

    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."
  }
}