how to create a custom two factor auth plugin for wordpress

1. Set up the Plugin Structure:
- Create a new directory for your plugin within the `wp-content/plugins/` directory.
- Inside the directory, create the main plugin file (e.g., `my-custom-2fa.php`) and add the plugin header information.

2. Implement the 2FA Functionality:
- Create a new class to handle the 2FA logic, e.g., `MyCustom2FAPlugin`.
- In the class, add methods to:
- Enqueue the necessary scripts and styles for the 2FA interface.
- Add the 2FA settings page to the WordPress admin menu.
- Handle the 2FA authentication process, including:
- Generating and storing the 2FA secret key for each user.
- Verifying the 2FA code entered by the user during login.
- Providing backup codes for users to use if they lose their 2FA device.

3. Customize the 2FA Interface:
- Create custom templates or use WordPress' built-in template functions to design the 2FA interface.
- You can use WordPress' settings API to create custom settings pages and options.
- Leverage WordPress' hooks and filters to integrate the 2FA functionality seamlessly into the login process.

4. Support Multiple 2FA Methods:
- Implement support for different 2FA methods, such as:
- Time-based One-Time Password (TOTP) using apps like Google Authenticator.
- SMS-based one-time codes.
- Email-based one-time codes.
- FIDO U2F security keys.

5. Provide User Management:
- Allow users to manage their 2FA settings, such as:
- Enabling/disabling 2FA.
- Configuring their preferred 2FA method.
- Generating and managing backup codes.

6. Enforce 2FA Policies:
- Implement the ability to enforce 2FA for specific user roles or the entire site.
- Provide options to set grace periods for users to set up 2FA.

7. Integrate with Other Plugins:
- Ensure your custom 2FA plugin works seamlessly with other popular WordPress plugins, such as WooCommerce, BuddyPress, or custom login pages.

8. Test and Optimize:
- Thoroughly test your custom 2FA plugin to ensure it works as expected and provides a smooth user experience.
- Optimize the plugin's performance and security to ensure it meets the WordPress standards.

9. Distribute and Maintain the Plugin:
- Package your plugin for distribution on the WordPress.org plugin repository or your own website.
- Provide documentation, support, and regular updates to maintain the plugin's functionality and security.

Creating a custom 2FA plugin for WordPress requires a good understanding of WordPress development, security best practices, and user experience design. It's a complex task, but following these steps should give you a solid foundation to build your own custom 2FA solution for your WordPress site.

Citations:
[1] https://www.wpbeginner.com/plugins/how-to-add-two-factor-authentication-for-wordpress/
[2] https://wordpress.org/plugins/two-factor-authentication/
[3] https://melapress.com/wordpress-2fa/
[4] https://wordpress.org/plugins/two-factor/
[5] https://www.wpzoom.com/blog/wordpress-two-factor-authentication/

Sample code for the plugin

Here is a sample code for a custom two-factor authentication (2FA) plugin for WordPress:

php
<?php
/*
Plugin Name: Custom 2FA Plugin
Description: A custom 2FA plugin for WordPress
*/

// Define the plugin constants
define('CUSTOM_2FA_PLUGIN_DIR', plugin_dir_path(__FILE__));
define('CUSTOM_2FA_PLUGIN_URL', plugin_dir_url(__FILE__));

// Define the 2FA methods
define('CUSTOM_2FA_METHODS', array(
    'google_authenticator',
    'sms',
    'email',
));

// Define the 2FA settings
function custom_2fa_settings() {
    // Add the 2FA settings page
    add_menu_page(
        'Custom 2FA Settings',
        'Custom 2FA',
        'manage_options',
        'custom-2fa-settings',
        'custom_2fa_settings_page'
    );
}

// Define the 2FA settings page
function custom_2fa_settings_page() {
    // Output the settings page
    ?>
    <div class="wrap">
        <h1>Custom 2FA Settings</h1>
        <form method="post" action="options.php">
            <?php settings_fields('custom_2fa_settings'); ?>
            <?php do_settings_sections('custom_2fa_settings'); ?>
            <table class="form-table">
                <tr>
                    <th><label for="custom_2fa_method">2FA Method:</label></th>
                    <td>
                        <select id="custom_2fa_method" name="custom_2fa_method">
                            <?php foreach (CUSTOM_2FA_METHODS as $method) { ?>
                                <option value="<?php echo $method; ?>"><?php echo $method; ?></option>
                            <?php } ?>
                        </select>
                    </td>
                </tr>
                <tr>
                    <th><label for="custom_2fa_secret_key">Secret Key:</label></th>
                    <td>
                        <input type="text" id="custom_2fa_secret_key" name="custom_2fa_secret_key" value="<?php echo get_option('custom_2fa_secret_key'); ?>">
                    </td>
                </tr>
            </table>
            <p class="submit">
                <input type="submit" class="button button-primary" value="Save Changes">
            </p>
        </form>
    </div>
    <?php
}

// Define the 2FA authentication function
function custom_2fa_authenticate($username, $password) {
    // Check if the user has 2FA enabled
    $user = get_user_by('login', $username);
    if (!get_option('custom_2fa_enabled')) {
        return wp_authenticate($username, $password);
    }

    // Get the 2FA method and secret key
    $method = get_option('custom_2fa_method');
    $secret_key = get_option('custom_2fa_secret_key');

    // Generate the 2FA code
    $code = custom_2fa_generate_code($method, $secret_key);

    // Check if the user entered the correct 2FA code
    if (!isset($_POST['custom_2fa_code']) || $_POST['custom_2fa_code'] !== $code) {
        return new WP_Error('invalid_2fa_code', 'Invalid 2FA code');
    }

    // Authenticate the user
    return wp_authenticate($username, $password);
}

// Define the 2FA code generation function
function custom_2fa_generate_code($method, $secret_key) {
    // Generate the code based on the 2FA method
    switch ($method) {
        case 'google_authenticator':
            // Use the Google Authenticator library to generate the code
            require_once CUSTOM_2FA_PLUGIN_DIR . 'google-authenticator.php';
            $ga = new GoogleAuthenticator();
            return $ga->getCode($secret_key);
        case 'sms':
            // Use the Twilio library to generate the code
            require_once CUSTOM_2FA_PLUGIN_DIR . 'twilio.php';
            $twilio = new Twilio();
            return $twilio->generateCode($secret_key);
        case 'email':
            // Use the PHPMailer library to generate the code
            require_once CUSTOM_2FA_PLUGIN_DIR . 'phpmailer.php';
            $phpmailer = new PHPMailer();
            return $phpmailer->generateCode($secret_key);
        default:
            return '';
    }
}

// Define the 2FA settings API
function custom_2fa_settings_api($settings) {
    // Add the 2FA settings to the API
    $settings->add_section('custom_2fa_settings', array(
        'title' => 'Custom 2FA Settings',
        'callback' => 'custom_2fa_settings_page',
    ));

    // Add the 2FA method field
    $settings->add_field(array(
        'type' => 'select',
        'label' => '2FA Method:',
        'name' => 'custom_2fa_method',
        'options' => array(
            'google_authenticator' => 'Google Authenticator',
            'sms' => 'SMS',
            'email' => 'Email',
        ),
    ));

    // Add the 2FA secret key field
    $settings->add_field(array(
        'type' => 'text',
        'label' => 'Secret Key:',
        'name' => 'custom_2fa_secret_key',
    ));

    // Add the 2FA enabled field
    $settings->add_field(array(
        'type' => 'checkbox',
        'label' => 'Enable 2FA:',
        'name' => 'custom_2fa_enabled',
    ));
}

// Register the plugin
function custom_2fa_plugin_register() {
    // Register the plugin settings API
    add_action('admin_init', 'custom_2fa_settings_api');

    // Register the plugin authentication function
    add_filter('authenticate', 'custom_2fa_authenticate');

    // Register the plugin code generation function
    add_filter('custom_2fa_code', 'custom_2fa_generate_code');
}

// Initialize the plugin
custom_2fa_plugin_register();

This code defines a custom 2FA plugin for WordPress that includes the following features:

1. Settings Page: A settings page is added to the WordPress admin dashboard where users can configure their 2FA settings.
2. 2FA Methods: The plugin supports three 2FA methods: Google Authenticator, SMS, and Email.
3. Code Generation: The plugin generates the 2FA code based on the selected method and secret key.
4. Authentication: The plugin authenticates the user by checking if they entered the correct 2FA code.
5. API Integration: The plugin integrates with the WordPress settings API to store and retrieve the 2FA settings.

This code is a basic example and may need to be modified to fit your specific requirements.