Authenticate by WordPress

readme.md

The Goal

Get WordPress user identity without need to include huge and unclear WP files.
Assumed that you place scripts somewhere near by WP, so you can access config, database and cookie.

Prerequisites

• PHP 5.4+
• Installed WP. I made it for WP 4.1 but I hope it is valid for earlier versions too.
• Some DataBase Access Level library. I use my own DBAL you can obvoiusly replace it to your own.

usage.php

<?php
//
// Get your own constants from actual wp-config.php
//
$site_url       = 'http://example.com';
$LOGGED_IN_KEY  = 'D^3*f,[}VS,$@j>{kl*uMNK-,)zor9ZJCg2X)=(Xv GD!Gy:>3@dpZi8F(J~ZGnz';
$LOGGED_IN_SALT = ',;r|2xEgGm/`F(nf^B+sn64kw[iF!]Qfq?;gYL~(v$ziQG:A {7aL{)c:gqxM>?s';
$salt           = $LOGGED_IN_KEY.$LOGGED_IN_SALT;
$cookie_name    = 'wordpress_logged_in_'.md5($site_url);
$db_params      = [
    'username'  => 'wp',
    'password'  => 'wpPassz3',
    'dbname'    => 'wp',
    'prefix'    => 'wp1_'
];
$db = new \R2\DBAL\PDOMySQL($db_params);

$auth = new WPAuth(compact('cookie_name', 'salt', 'db'));
var_export($auth->authByCookie()); // false or array with user data

WPAuth.php

<?php

class WPAuth
{
    private $config;

    public function __construct(array $config)
    {
        $this->config = array_replace(
            [
                'cookie_name'   => 'wordpress',
                'salt'          => '',
                'db'            => null,
            ],
            $config
        );
    }

    public function authByCookie()
    {
        if (!isset($_COOKIE[$this->config['cookie_name']])
         || count($tmp = explode('|', $_COOKIE[$this->config['cookie_name']])) !== 4
         || $tmp[1] < time()) {
            return false;
        }
        list($username, $expiration, $token, $hmac) = $tmp;

        $db = $this->config['db'];
        $user = $db
            ->query(
                "SELECT * ".
                "FROM `:p_users` ".
                "WHERE `user_login` = :username",
                compact('username')
            )
            ->fetchAssoc();
        if (!$user) {
            return false;
        }

        $pass_frag = substr($user['user_pass'], 8, 4);
        $key = hash_hmac('md5', $username.'|'.$pass_frag.'|'.$expiration.'|'.$token, $this->config['salt']);
        $hash = hash_hmac('sha256', $username.'|'.$expiration.'|'.$token, $key);
        if ($hash !== $hmac) {
            return false;
        }

        $meta = $db
            ->query(
                "SELECT `meta_value` ".
                "FROM `:p_usermeta` ".
                "WHERE `user_id` = :ID AND `meta_key` = 'session_tokens'",
                $user
            )
            ->result();
        if (empty($meta)) {
            return false;
        }
        $sessions = unserialize($meta);
        $hash_token = hash('sha256', $token);
        if (!isset($sessions[$hash_token]) || $sessions[$hash_token]['expiration'] < time()) {
            return false;
        }

        return $user;
    }
}