mailhandler.module

<?php
/**
 * @file
 * Hook implementations for Mailhandler module.
 */

use Drupal\Core\Entity\EntityInterface;

/**
 * Implements hook_ENTITY_TYPE_presave().
 */
function mailhandler_user_presave(EntityInterface $entity) {
  /** @var \Drupal\user\UserInterface $entity */
  if ($entity->hasField('mailhandler_gpg_key') && extension_loaded('gnupg')) {
    /** @var \Drupal\user\UserInterface|null $original */
    $original = $entity->original;
    $gpg_key_field = $entity->get('mailhandler_gpg_key');

    // Update the GPG keyring in case a new user has been created
    // or the GPG key has been changed.
    if (!$original || !$gpg_key_field->equals($original->get('mailhandler_gpg_key'))) {
      // Initialize GnuPG resource.
      $gpg = gnupg_init();

      if ($original) {
        // Delete the old key from GPG keyring.
        gnupg_deletekey($gpg, $original->get('mailhandler_gpg_key')->fingerprint);
      }

      // Import the GPG public key.
      $key_info = gnupg_import($gpg, $gpg_key_field->public_key);

      // Update the fingerprint property.
      $gpg_key_field->fingerprint = $key_info['fingerprint'];
    }
  }
}