I am working with a client with some strict security measures. After undergoing security review, we were notified that the user name stored in the logged in cookie, e.g.
wordpress_logged_in[username]|[hash]
is something that has to be removed. Since this is an integral part of the login system, I’m not sure how to remove it and still maintain the session.
1
Short introduction
After quick look inside WP source code, I think I’ve found solution…
WordPress uses two functions to set and parse auth cookies:
wp_generate_auth_cookie
wp_parse_auth_cookie
There is a filter in wp_generate_auth_cookie
called auth_cookie
which you probably could use to change the contents of cookie, but there is no filter inside wp_parse_auth_cookie
, but…
Both of these functions are defined in pluggable.php, which means, that you can write your own implementations for them and overwrite default ones.
Solution
- Write your own plugin (let’s call it Better Auth Cookie)
- Implement your own
wp_generate_auth_cookie
andwp_parse_auth_cookie
functions inside this plugin. - Activate your plugin.
You can find my sample implementation (based strongly on original versions) of these functions below:
if ( !function_exists('wp_generate_auth_cookie') ) :
/**
* Generate authentication cookie contents.
*
* @since 2.5.0
*
* @param int $user_id User ID
* @param int $expiration Cookie expiration in seconds
* @param string $scheme Optional. The cookie scheme to use: auth, secure_auth, or logged_in
* @param string $token User's session token to use for this cookie
* @return string Authentication cookie contents. Empty string if user does not exist.
*/
function wp_generate_auth_cookie( $user_id, $expiration, $scheme="auth", $token = '' ) {
$user = get_userdata($user_id);
if ( ! $user ) {
return '';
}
if ( ! $token ) {
$manager = WP_Session_Tokens::get_instance( $user_id );
$token = $manager->create( $expiration );
}
$pass_frag = substr($user->user_pass, 8, 4);
$key = wp_hash( $user->user_login . '|' . $pass_frag . '|' . $expiration . '|' . $token, $scheme );
// If ext/hash is not present, compat.php's hash_hmac() does not support sha256.
$algo = function_exists( 'hash' ) ? 'sha256' : 'sha1';
$hash = hash_hmac( $algo, $user->user_login . '|' . $expiration . '|' . $token, $key );
$cookie = $user_id . '|' . $expiration . '|' . $token . '|' . $hash;
/**
* Filter the authentication cookie.
*
* @since 2.5.0
*
* @param string $cookie Authentication cookie.
* @param int $user_id User ID.
* @param int $expiration Authentication cookie expiration in seconds.
* @param string $scheme Cookie scheme used. Accepts 'auth', 'secure_auth', or 'logged_in'.
* @param string $token User's session token used.
*/
return apply_filters( 'auth_cookie', $cookie, $user_id, $expiration, $scheme, $token );
}
endif;
if ( !function_exists('wp_parse_auth_cookie') ) :
/**
* Parse a cookie into its components
*
* @since 2.7.0
*
* @param string $cookie
* @param string $scheme Optional. The cookie scheme to use: auth, secure_auth, or logged_in
* @return array Authentication cookie components
*/
function wp_parse_auth_cookie($cookie="", $scheme="") {
if ( empty($cookie) ) {
switch ($scheme){
case 'auth':
$cookie_name = AUTH_COOKIE;
break;
case 'secure_auth':
$cookie_name = SECURE_AUTH_COOKIE;
break;
case "logged_in":
$cookie_name = LOGGED_IN_COOKIE;
break;
default:
if ( is_ssl() ) {
$cookie_name = SECURE_AUTH_COOKIE;
$scheme="secure_auth";
} else {
$cookie_name = AUTH_COOKIE;
$scheme="auth";
}
}
if ( empty($_COOKIE[$cookie_name]) )
return false;
$cookie = $_COOKIE[$cookie_name];
}
$cookie_elements = explode('|', $cookie);
if ( count( $cookie_elements ) !== 4 ) {
return false;
}
list( $user_id, $expiration, $token, $hmac ) = $cookie_elements;
$user = get_userdata($user_id);
$username = ( ! $user ) ? '' : $user->user_login;
return compact( 'username', 'expiration', 'token', 'hmac', 'scheme' );
}
endif;
My version of these functions replaces user_login
with user_id
. But it should be a good start for changing it to something even more complex (i.e. user specific hash, or something like this).