Set config item (csrf) doesnt work in Codeigniter

Question

I want to turn ON csrf protection only in a few of my controllers, so I have

function __construct() {

    parent::__construct();
    $this->load->library('form_validation');        
    $this->load->library('tank_auth');
    $this->load->helper(array('form', 'url'));
    $this->load->model('user_model', '', true);

    $this->config->set_item('csrf_protection', TRUE);

}

But it doesn't seem to work, although when I do var_dump($this->config) on a page it shows that csrf_protection is TRUE, but the cookies are not set and the form has a hidden field without value

<input type="hidden" name="ci_csrf_token" value="" />

Csrf token name and cookie name are all set, the forms are called with form_open().

Any help would be much appreciated.

Update: So this is not possible from version 2.1.1 because of the line in security class construct if (config_item('csrf_protection') === TRUE) {

Security class is initialized before the controller, so its natural that the config item change in the controller will not affect it.

Answer 1

I have a solution for you. Create a custom application/core/MY_Security.php and put this in it:

<?php if ( !defined( 'BASEPATH' ) ) exit( 'No direct script access allowed' );

class MY_Security extends CI_Security
{
    public function csrf_verify( )
    {
        foreach ( config_item('csrf_excludes') as $exclude )
        {
            $uri = load_class('URI', 'core');
            if ( preg_match( $exclude, $uri->uri_string() ) > 0 )
            {
                // still do input filtering to prevent parameter piggybacking in the form
                if (isset($_COOKIE[$this->_csrf_cookie_name]) && preg_match( '#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name] ) == 0)
                {
                    unset( $_COOKIE[$this->_csrf_cookie_name] );
                }
                return;
            }
        }
        parent::csrf_verify( );
    }
}

This will check the following excludes which you need to put in your application/config.php in the CSRF section:

$config['csrf_excludes'] = array
    ( '@^/?excluded_url_1/?@i'
    , '@^/?excluded_url_2/?@i' );

Every matching URL pattern will be excluded from CSRF checks. You can build regex here at http://rubular.com

cheers