NginxでGETパラメーターを使ってbasic認証の条件分岐

  location ~* /wp-login\.php|/wp-admin/.*\.php$ {
    set $auth_basic "INPUT ID & PASSWORD";
    if ($arg_action = 'postpass') {
      set $auth_basic off;
    }
    auth_basic $auth_basic;
    auth_basic_user_file /etc/nginx/conf.d/htpasswd;

    fastcgi_pass   unix:/run/php/php7.4-fpm.sock;
    fastcgi_index  index.php;
    fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
    include        fastcgi_params;
  }