wordpress get posts random from specific categories

Need some help. I have code in functions.php. when going to myweb.com/random=1 it goes to random post but I want it picks random only from chosen categories. I tried that but it still picks it from all categories.

add_action('init','random_add_rewrite');
function random_add_rewrite() {
    global $wp;
    $wp->add_query_var('random');
    add_rewrite_rule('random/?$', 'index.php?random=1', 'top');
}

add_action('template_redirect','random_template');
function random_template() {
    if (get_query_var('random') == 1) {
        $posts = get_posts('category=14,17,23,28,32&orderby=rand&numberposts=1');
        foreach($posts as $post) {
            $link = get_permalink($post);
        }
        wp_redirect($link,307);
        exit;
    }
}