UserAuth.php

<?php

namespace Drupal\user;

use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\Core\Password\PasswordInterface;

/**
 * Validates user authentication credentials.
 */
class UserAuth implements UserAuthInterface {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The password hashing service.
     *
     * @var \Drupal\Core\Password\PasswordInterface
     */
    protected $passwordChecker;
    
    /**
     * Constructs a UserAuth object.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Password\PasswordInterface $password_checker
     *   The password service.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager, PasswordInterface $password_checker) {
        $this->entityTypeManager = $entity_type_manager;
        $this->passwordChecker = $password_checker;
    }
    
    /**
     * {@inheritdoc}
     */
    public function authenticate($username, $password) {
        $uid = FALSE;
        if (!empty($username) && strlen($password) > 0) {
            $account_search = $this->entityTypeManager
                ->getStorage('user')
                ->loadByProperties([
                'name' => $username,
            ]);
            if ($account = reset($account_search)) {
                if ($this->passwordChecker
                    ->check($password, $account->getPassword())) {
                    // Successful authentication.
                    $uid = $account->id();
                    // Update user to new password scheme if needed.
                    if ($this->passwordChecker
                        ->needsRehash($account->getPassword())) {
                        $account->setPassword($password);
                        $account->save();
                    }
                }
            }
        }
        return $uid;
    }

}