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<?php

/**

 * The OpenID library's Diffie-Hellman implementation.

 *

 * PHP versions 4 and 5

 *

 * LICENSE: See the COPYING file included in this distribution.

 *

 * @access private

 * @package OpenID

 * @author JanRain, Inc. <openid@janrain.com>

 * @copyright 2005 Janrain, Inc.

 * @license http://www.gnu.org/copyleft/lesser.html LGPL

 */

require_once 'Auth/OpenID/BigMath.php';

require_once 'Auth/OpenID/HMACSHA1.php';

function Auth_OpenID_getDefaultMod()

{

    return '155172898181473697471232257763715539915724801'.

        '966915404479707795314057629378541917580651227423'.

        '698188993727816152646631438561595825688188889951'.

        '272158842675419950341258706556549803580104870537'.

        '681476726513255747040765857479291291572334510643'.

        '245094715007229621094194349783925984760375594985'.

        '848253359305585439638443';

}

function Auth_OpenID_getDefaultGen()

{

    return '2';

}

/**

 * The Diffie-Hellman key exchange class.  This class relies on

 * {@link Auth_OpenID_MathLibrary} to perform large number operations.

 *

 * @access private

 * @package OpenID

 */

class Auth_OpenID_DiffieHellman {

    var $mod;

    var $gen;

    var $private;

    var $lib = null;

    function Auth_OpenID_DiffieHellman($mod = null, $gen = null,

                                       $private = null, $lib = null)

    {

        if ($lib === null) {

            $this->lib =& Auth_OpenID_getMathLib();

        } else {

            $this->lib =& $lib;

        }

        if ($mod === null) {

            $this->mod = $this->lib->init(Auth_OpenID_getDefaultMod());

        } else {

            $this->mod = $mod;

        }

        if ($gen === null) {

            $this->gen = $this->lib->init(Auth_OpenID_getDefaultGen());

        } else {

            $this->gen = $gen;

        }

        if ($private === null) {

            $r = $this->lib->rand($this->mod);

            $this->private = $this->lib->add($r, 1);

        } else {

            $this->private = $private;

        }

        $this->public = $this->lib->powmod($this->gen, $this->private,

                                           $this->mod);

    }

    function getSharedSecret($composite)

    {

        return $this->lib->powmod($composite, $this->private, $this->mod);

    }

    function getPublicKey()

    {

        return $this->public;

    }

    /**

     * Generate the arguments for an OpenID Diffie-Hellman association

     * request

     */

    function getAssocArgs()

    {

        $cpub = $this->lib->longToBase64($this->getPublicKey());

        $args = array(

                      'openid.dh_consumer_public' => $cpub,

                      'openid.session_type' => 'DH-SHA1'

                      );

        if ($this->lib->cmp($this->mod, Auth_OpenID_getDefaultMod()) ||

            $this->lib->cmp($this->gen, Auth_OpenID_getDefaultGen())) {

            $args['openid.dh_modulus'] = $this->lib->longToBase64($this->mod);

            $args['openid.dh_gen'] = $this->lib->longToBase64($this->gen);

        }

        return $args;

    }

    function usingDefaultValues()

    {

        return ($this->mod == Auth_OpenID_getDefaultMod() &&

                $this->gen == Auth_OpenID_getDefaultGen());

    }

    /**

     * Perform the server side of the OpenID Diffie-Hellman association

     */

    function serverAssociate($consumer_args, $assoc_secret)

    {

        $lib =& Auth_OpenID_getMathLib();

        if (isset($consumer_args['openid.dh_modulus'])) {

            $mod = $lib->base64ToLong($consumer_args['openid.dh_modulus']);

        } else {

            $mod = null;

        }

        if (isset($consumer_args['openid.dh_gen'])) {

            $gen = $lib->base64ToLong($consumer_args['openid.dh_gen']);

        } else {

            $gen = null;

        }

        $cpub64 = @$consumer_args['openid.dh_consumer_public'];

        if (!isset($cpub64)) {

            return false;

        }

        $dh = new Auth_OpenID_DiffieHellman($mod, $gen);

        $cpub = $lib->base64ToLong($cpub64);

        $mac_key = $dh->xorSecret($cpub, $assoc_secret);

        $enc_mac_key = base64_encode($mac_key);

        $spub64 = $lib->longToBase64($dh->getPublicKey());

        $server_args = array(

                             'session_type' => 'DH-SHA1',

                             'dh_server_public' => $spub64,

                             'enc_mac_key' => $enc_mac_key

                             );

        return $server_args;

    }

    function consumerFinish($reply)

    {

        $spub = $this->lib->base64ToLong($reply['dh_server_public']);

        if ($this->lib->cmp($spub, 0) <= 0) {

            return false;

        }

        $enc_mac_key = base64_decode($reply['enc_mac_key']);

        return $this->xorSecret($spub, $enc_mac_key);

    }

    function xorSecret($composite, $secret)

    {

        $dh_shared = $this->getSharedSecret($composite);

        $dh_shared_str = $this->lib->longToBinary($dh_shared);

        $sha1_dh_shared = Auth_OpenID_SHA1($dh_shared_str);

        $xsecret = "";

        for ($i = 0; $i < strlen($secret); $i++) {

            $xsecret .= chr(ord($secret[$i]) ^ ord($sha1_dh_shared[$i]));

        }

        return $xsecret;

    }

}