Dart

Use a TLS Client Certificate

Demonstrates the Chilkat MailMan.SetSslClientCert method, which sets the client-side certificate to use for SSL/TLS connections. This is typically not required — most SSL/TLS connections authenticate the server only. This example loads a client certificate from a PFX and uses it when connecting.

Background: In an ordinary TLS handshake only the server presents a certificate, and the client proves who it is later with a password. Mutual TLS adds a second leg: the client also presents a certificate, so it is authenticated cryptographically at the transport layer. Some corporate or high-security mail servers require this. Because the client must prove possession of the key, the certificate needs its private key — hence loading from a PFX.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  var success = false;

  // Demonstrates the MailMan.SetSslClientCert method, which sets the client-side certificate
  // to use for SSL/TLS connections.  This is typically not required -- most SSL/TLS
  // connections authenticate the server only.

  final mailman = CkMailMan();

  // Configure the SMTP server connection.
  mailman.smtpHost = 'smtp.example.com';
  mailman.smtpPort = 465;
  mailman.smtpSsl = true;
  mailman.smtpUsername = 'user@example.com';
  mailman.smtpPassword = 'myPassword';

  // Load the client certificate (with its private key) from a PFX file.
  final cert = CkCert();
  try {
    cert.loadPfxFile('qa_data/certs/client.pfx', 'pfx_password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Use this certificate to identify the client during the TLS handshake.
  try {
    mailman.setSslClientCert(cert);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  success = mailman.verifySmtpLogin();
  if (!success) {
    print(mailman.lastErrorText);
    return;
  }

  print('Connected using a TLS client certificate.');

  // Note: The path "qa_data/certs/client.pfx" is a relative local filesystem path,
  // relative to the current working directory of the running application.
}