<?php
   private function _prepareDigestAuth()
    {
    	$digest = NULL;
    	$nonce = uniqid();

        // We need to test which server authentication variable to use
	    if(isset($_SERVER['PHP_AUTH_DIGEST']))
	    {
	        $digest = $_SERVER['PHP_AUTH_DIGEST'];
	    }

	    elseif(isset($_SERVER['HTTP_AUTHORIZATION']))
	    {
	        $digest = $_SERVER['HTTP_AUTHORIZATION'];
	    }

	    else
	    {
	    	$digest = "";
	    }

		// If there was no digest, show login
		if (empty($digest))
		{
			$this->_forceLogin($nonce);
		}

	    preg_match_all('@(username|nonce|uri|nc|cnonce|qop|response)'.
                    '=[\'"]?([^\'",]+)@', $digest, $t);
    	$digest_parts = array_combine($t[1], $t[2]);

		if ( !$this->_checkLogin($digest_parts['username']) )
		{
		    $this->_forceLogin($nonce);
		}

		$valid_logins =& $this->config->item('rest_valid_logins');
		$valid_pass = $valid_logins[$digest_parts['username']];

		// Based on all the info we gathered we can figure out what the response should be
        $A1 = md5($digest['username'] . ':' . $this->config->item('rest_realm') . ':' . $valid_pass);
        $A2 = md5($_SERVER['REQUEST_METHOD'].':'.$digest['uri']);

        $valid_response = md5($A1.':'.$digest['nonce'].':'.$digest['nc'].':'.$digest['cnonce'].':'.$digest['qop'].':'.$A2);

        if ($digest['response'] != $valid_response)
		{
			$this->_forceLogin($nonce);
		}

    }


    private function _forceLogin($nonce = '')
    {
	    header('HTTP/1.0 401 Unauthorized');

    	if($this->config->item('rest_auth') == 'basic')
        {
        	header('WWW-Authenticate: Basic realm="'.$this->config->item('rest_realm').'"');
        }

        elseif($this->config->item('rest_auth') == 'digest')
        {
        	header('WWW-Authenticate: Digest realm="'.$this->config->item('rest_realm'). '" qop="auth" nonce="'.$nonce.'" opaque="'.md5($this->config->item('rest_realm')).'"');
        }

	    echo 'Text to send if user hits Cancel button';
	    die();
    }
/php?>