class BasicAuth

class BasicAuth implements AuthenticationProviderInterface, AuthenticationProviderChallengeInterface {
    
    /**
     * The config factory.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * The user auth service.
     *
     * @var \Drupal\user\UserAuthInterface
     */
    protected $userAuth;
    
    /**
     * The flood service.
     *
     * @var \Drupal\Core\Flood\FloodInterface
     */
    protected $flood;
    
    /**
     * The entity type manager service.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Constructs a HTTP basic authentication provider object.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The config factory.
     * @param \Drupal\user\UserAuthInterface $user_auth
     *   The user authentication service.
     * @param \Drupal\Core\Flood\FloodInterface $flood
     *   The flood service.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager service.
     */
    public function __construct(ConfigFactoryInterface $config_factory, UserAuthInterface $user_auth, FloodInterface $flood, EntityTypeManagerInterface $entity_type_manager) {
        $this->configFactory = $config_factory;
        $this->userAuth = $user_auth;
        $this->flood = $flood;
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public function applies(Request $request) {
        $username = $request->headers
            ->get('PHP_AUTH_USER');
        $password = $request->headers
            ->get('PHP_AUTH_PW');
        return isset($username) && isset($password);
    }
    
    /**
     * {@inheritdoc}
     */
    public function authenticate(Request $request) {
        $flood_config = $this->configFactory
            ->get('user.flood');
        $username = $request->headers
            ->get('PHP_AUTH_USER');
        $password = $request->headers
            ->get('PHP_AUTH_PW');
        // Flood protection: this is very similar to the user login form code.
        // @see \Drupal\user\Form\UserLoginForm::validateAuthentication()
        // Do not allow any login from the current user's IP if the limit has been
        // reached. Default is 50 failed attempts allowed in one hour. This is
        // independent of the per-user limit to catch attempts from one IP to log
        // in to many different user accounts.  We have a reasonably high limit
        // since there may be only one apparent IP for all users at an institution.
        if ($this->flood
            ->isAllowed('basic_auth.failed_login_ip', $flood_config->get('ip_limit'), $flood_config->get('ip_window'))) {
            $accounts = $this->entityTypeManager
                ->getStorage('user')
                ->loadByProperties([
                'name' => $username,
                'status' => 1,
            ]);
            $account = reset($accounts);
            if ($account) {
                if ($flood_config->get('uid_only')) {
                    // Register flood events based on the uid only, so they apply for any
                    // IP address. This is the most secure option.
                    $identifier = $account->id();
                }
                else {
                    // The default identifier is a combination of uid and IP address. This
                    // is less secure but more resistant to denial-of-service attacks that
                    // could lock out all users with public user names.
                    $identifier = $account->id() . '-' . $request->getClientIP();
                }
                // Don't allow login if the limit for this user has been reached.
                // Default is to allow 5 failed attempts every 6 hours.
                if ($this->flood
                    ->isAllowed('basic_auth.failed_login_user', $flood_config->get('user_limit'), $flood_config->get('user_window'), $identifier)) {
                    $uid = $this->userAuth
                        ->authenticate($username, $password);
                    if ($uid) {
                        $this->flood
                            ->clear('basic_auth.failed_login_user', $identifier);
                        return $this->entityTypeManager
                            ->getStorage('user')
                            ->load($uid);
                    }
                    else {
                        // Register a per-user failed login event.
                        $this->flood
                            ->register('basic_auth.failed_login_user', $flood_config->get('user_window'), $identifier);
                    }
                }
            }
        }
        // Always register an IP-based failed login event.
        $this->flood
            ->register('basic_auth.failed_login_ip', $flood_config->get('ip_window'));
        return NULL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function challengeException(Request $request, \Exception $previous) {
        $site_config = $this->configFactory
            ->get('system.site');
        $site_name = $site_config->get('name');
        $challenge = new FormattableMarkup('Basic realm="@realm"', [
            '@realm' => !empty($site_name) ? $site_name : 'Access restricted',
        ]);
        // A 403 is converted to a 401 here, but it doesn't matter what the
        // cacheability was of the 403 exception: what matters here is that
        // authentication credentials are missing, i.e. this request was made
        // as an anonymous user.
        // Therefore, the following actions will be taken:
        // 1. Verify whether the current user has the 'anonymous' role or not. This
        //    works fine because:
        //    - Thanks to \Drupal\basic_auth\PageCache\DisallowBasicAuthRequests,
        //      Page Cache never caches a response whose request has Basic Auth
        //      credentials.
        //    - Dynamic Page Cache will cache a different result for when the
        //      request is unauthenticated (this 401) versus authenticated (some
        //      other response)
        // 2. Have the 'config:user.role.anonymous' cache tag, because the only
        //    reason this 401 would no longer be a 401 is if permissions for the
        //    'anonymous' role change, causing the cache tag to be invalidated.
        // @see \Drupal\Core\EventSubscriber\AuthenticationSubscriber::onExceptionSendChallenge()
        // @see \Drupal\Core\EventSubscriber\ClientErrorResponseSubscriber()
        // @see \Drupal\Core\EventSubscriber\FinishResponseSubscriber::onAllResponds()
        $cacheability = CacheableMetadata::createFromObject($site_config)->addCacheTags([
            'config:user.role.anonymous',
        ])
            ->addCacheContexts([
            'user.roles:anonymous',
        ]);
        return $request->isMethodCacheable() ? new CacheableUnauthorizedHttpException($cacheability, (string) $challenge, 'No authentication credentials provided.', $previous) : new UnauthorizedHttpException((string) $challenge, 'No authentication credentials provided.', $previous);
    }

}