Digest HTTP Authentication class for core

DigestAuth.php

<?php
/**
 * Digest HTTP Authentication class
 *
 * PHP version 5.5
 *
 * @author Gabriele Diener <gabriele.diener@caffeina.com>
 */

class DigestAuth {

	protected static 	$realm 			= "Restricted area",
						$data			= false,
						$needed_parts 	= [
							'nonce' 	=> true,
							'nc' 		=> true,
							'cnonce' 	=> true,
							'qop' 		=> true,
							'username' 	=> true,
							'uri' 		=> true,
							'response' 	=> true
						];

	public static function authenticate( $callback = false ) {
		/**
		 * analyze the PHP_AUTH_DIGEST variable
		 */
		if (
			Request::server( 'PHP_AUTH_DIGEST', false ) ||
			!( static::$data = static::parse( Request::server( 'PHP_AUTH_DIGEST', false ) ) ) ||
			!Options::get( "auth.clients." . static::$data['username'], false ) ||
			static::$data['response'] !== static::validResponse()
		) {
			return is_callable($callback) ? call_user_func($callback) : false;
		}

		return true;
	}

	public static function failHeader() {
		return [ "WWW-Authenticate", 'Digest realm="' . static::$realm . '",qop="auth",nonce="' . uniqid() . '",opaque="' . Hash::make(static::$realm) . '"' ];
	}

	protected static function parse($txt) {
		$needed = static::$needed_parts;
		preg_match_all( '@(' . implode( '|', array_keys($needed) ) . ')=(?:([\'"])([^\2]+?)\2|([^\s,]+))@', $txt, $matches, PREG_SET_ORDER );

		foreach ( $matches as $m ) {
			$data[$m[1]] = $m[3] ? $m[3] : $m[4];
			unset($needed[$m[1]]);
		}

		return $needed ? false : $data;
	}

	/**
	 * generate the valid response
	 */
	protected static function validResponse() {
		if (!static::$data) return false;
		$hash = [
			Hash::make( static::$data['username'] . ":{$realm}:" . Options::get( "auth.clients." . static::$data['username'], false ) ),
			Hash::make( Request::server('REQUEST_METHOD') . ":" . static::$data['uri'] )
		];
		return Hash::make("{$hash[0]}:" . static::$data['nonce'] . ":" . static::$data['nc'] . 	":" . static::$data['cnonce'] . ":" . static::$data['qop'] . ":{$hash[2]}");
	}
}