<?php
// configure error reporting
error_reporting(E_ALL | E_STRICT);

// set include paths for zend framework
set_include_path(PATH_SEPARATOR . get_include_path()
	. PATH_SEPARATOR . './library/');

// load loader and set autoload function
require_once 'Zend/Loader.php';
spl_autoload_register(array('Zend_Loader', 'autoload'));
	
/*-----------------------------------------------------------*/

$client = new Zend_Http_Client('http://services.msn.com/svcs/hotmail/httpmail.asp', array(
	'useragent' => 'Outlook-Express/6.0',
	'maxredirects' => 0));
$client->setMethod('PROPFIND');

$digest = new Digest($client, 'PROPFIND', 'zftest@hotmail.co.uk', 'password123');
$digest->request();

/*-----------------------------------------------------------*/

class Digest
{
	private $client;
	private $method; // we shouldnt have to specify this, it should be possible to get it from the client
	private $username;
	private $password;
	
	private $nonce;
	private $nc = 1;
	private $a1;
	
	public function __construct(Zend_Http_Client $client, $method, $username, $password)
	{
		$this->client = $client;
		$this->method = $method;
		$this->username = $username;
		$this->password = $password;
	}
	
	public function request()
	{
		// make initial request		
		$response = $this->client->request();		
		Zend_Debug::dump($response->getHeaders(), 'Initial Request Response');
		
		// check the status
		if ($response->getStatus() != 401) {
			return $response;
		}
		
		// get the authenticate header (we might also want to try for proxy-authenticate)
		$resHeader = $response->getHeader('www-authenticate');
		
		// check that authentication digest has been requested
		if (!preg_match('/^Digest/i', $resHeader)) {
			throw new Zend_Exception('server does not require digest authentication');
		}
		
		// take the response header params and create a request header
		$resParams = $this->splitHeader($resHeader);
		$reqParams = $this->calculateParams($resParams, $response);
		$reqHeader = $this->joinHeader($reqParams);
		
		Zend_Debug::dump($reqHeader, 'Authorization Request Header');
		
		// set header and re-request
		$this->client->setHeaders('Authorization', $reqHeader);
		$response = $this->client->request();		
		Zend_Debug::dump($response->getHeaders(), 'Authorization Request Response');
			
		return $response;
	}
	
	private function calculateParams($params, $response)
	{	
		// generate a random client nonce value
		$cnonce = md5(microtime(true));
		
		// check we have the minumum requirements
		if (!isset($params['realm'])) {
			throw new Zend_Exception('authentication realm parameter missing');
		}
		if (!isset($params['nonce'])) {
			throw new Zend_Exception('authentication nonce parameter missing');
		}
		
		// check if we are retrying the nonce value
		if (isset($this->nonce)) {
			if ($this->nonce == $params['nonce']) {
				$this->nc++;
			} else {
				$this->nonce = $params['nonce'];
				$this->nc = 1;
			}
		} else {
			$this->nonce = $params['nonce'];
		}

		// convert decimal nc to hex
		$nc = dechex($this->nc);
		
		// set required values
		$result = array(
			'username'	=> '"' . $this->username . '"',
			'realm'		=> '"' . $params['realm'] . '"',
			'nonce'		=> '"' . $params['nonce'] . '"',
			'uri'		=> '"' . $this->client->getUri()->getPath() . '"',
		);
	
		// check for a qop value
		if (isset($params['qop'])) {
			$qops = preg_split('/;\s+/', $params['qop']);
			if (in_array('auth', $qops)) {
				$qop = 'auth';
			} 
			/* // todo
			elseif (in_array('auth-int', $qops)) {
				$qop = 'auth-int';
			}
			*/
		}
		
		// check for an algorithm value
		if (isset($params['algorithm'])) {
			if ($params['algorithm'] == 'MD5' || $params['algorithm'] == 'MD5-sess') {
				$algorithm = $params['algorithm'];
			}
		}
		
		// if qop is specified add parameters to result
		if(isset($qop)) {
			$result['qop']	  = $qop;
			$result['nc']	  = $nc;
			$result['cnonce'] = '"' . $cnonce . '"';
		}
		
		// if an algorithm is specified add parameter to result
		if(isset($algorithm)) {
			$result['algorithm'] = $algorithm;
		}
		
		// generate the A1 string based on the algorithm value
		if (!isset($algorithm) || $algorithm == 'MD5') {
			$a1 = $this->username . ':' . $params['realm'] . ':' . $this->password;
			$this->a1 = null;
		} elseif ($algorithm == 'MD5-sess') {
			if (isset($this->a1)) {
				$a1 = $this->a1;
			} else {
				$a1 = $this->h($this->username . ':' . $params['realm'] . ':' . $this->password) . ':' . $params['nonce'] . ':' . $cnonce;
				$this->a1 = $a1;
			}
		}
		
		// generate secret value
		$secret = $this->h($a1);
		
		// generate the A2 string based on the qop value
		if (!isset($qop) || $qop == 'auth') {
			$a2 = $this->method . ':' . $this->client->getUri()->getPath();
		} 
		/* //todo
		elseif($qop == 'auth-int') { 
			$a2 = $this->method . ':' . $uri . ':' . *entity-body*;
		}
		*/
		
		// generate the response hash based on the qop value
		if(!isset($qop)) {
			$response = $this->kd($secret, $params['nonce'] . ':' . $a2);
		} elseif($qop == 'auth' || $qop == 'auth-int') {
			$response = $this->kd($secret, $params['nonce'] . ':' . $nc . ':' . $cnonce . ':' . $qop . ':' . $a2);
		}
		
		// add response value to result
		$result['response'] = '"' . $response . '"';
			
		// check if an opaque value was sent
		if (isset($params['opaque'])) {
			$result['opaque'] = '"' . $params['opaque'] . '"';
		}
		
		return $result;
	}
	
	private function h($data)
	{
		return md5($data);
	}
	
	private function kd($secret, $data)
	{
		return $this->h($secret . ':' . $data);
	}
	
	private function splitHeader($header)
	{	
		$params = array();
	
		// remove the leading Digest string
		$header = preg_replace('/^Digest\s+(.*)$/i', '$1', $header);
		
		// match all individual parts of the header
		preg_match_all('/([^=]+)=("[^"]+"|[^,]+)(?:,\s*|$)/', $header, $matches);
		
		// loop through matches remove quotes and add to array
		foreach ($matches[1] as $key => $name) {
			$params[$name] = trim($matches[2][$key], '"');
		}
		
		return $params;
	}
	
	private function joinHeader($params)
	{	
		$header  = 'Digest ';
		
		// loop through params and add to header
		foreach ($params as $name => $value) {
			$header .= $name . '=' . $value . ', ';
		}
		
		// trim trailing comma-space
		$header = rtrim($header, ', ');
		
		return $header;	
	}

}