Merge remote-tracking branch 'upstream/master'

1 files changed, 845 insertions, 0 deletions

diff --git a/library/openid/provider/provider.php b/library/openid/provider/provider.php
new file mode 100644
index 000000000..03fbe1c81
--- /dev/null
+++ b/library/openid/provider/provider.php
@@ -0,0 +1,845 @@
+<?php
+/**
+ * Using this class, you can easily set up an OpenID Provider.
+ * It's independent of LightOpenID class.
+ * It requires either GMP or BCMath for session encryption, 
+ * but will work without them (although either via SSL, or in stateless mode only).
+ * Also, it requires PHP >= 5.1.2
+ * 
+ * This is an alpha version, using it in production code is not recommended,
+ * until you are *sure* that it works and is secure.
+ *
+ * Please send me messages about your testing results 
+ * (even if successful, so I know that it has been tested).
+ * Also, if you think there's a way to make it easier to use, tell me -- it's an alpha for a reason.
+ * Same thing applies to bugs in code, suggestions, 
+ * and everything else you'd like to say about the library.
+ *
+ * There's no usage documentation here, see the examples.
+ *
+ * @author Mewp
+ * @copyright Copyright (c) 2010, Mewp
+ * @license http://www.opensource.org/licenses/mit-license.php MIT
+ */
+ini_set('error_log','log');
+abstract class LightOpenIDProvider
+{
+    # URL-s to XRDS and server location.
+    public $xrdsLocation, $serverLocation;
+    
+    # Should we operate in server, or signon mode?
+    public $select_id = false;
+    
+    # Lifetime of an association.
+    protected $assoc_lifetime = 600;
+    
+    # Variables below are either set automatically, or are constant.
+    # -----
+    # Can we support DH?
+    protected $dh = true;
+    protected $ns = 'http://specs.openid.net/auth/2.0';
+    protected $data, $assoc;
+    
+    # Default DH parameters as defined in the specification.
+    protected $default_modulus;
+    protected $default_gen = 'Ag==';
+    
+    # AX <-> SREG transform
+    protected $ax_to_sreg = array(
+        'namePerson/friendly'     => 'nickname',
+        'contact/email'           => 'email',
+        'namePerson'              => 'fullname',
+        'birthDate'               => 'dob',
+        'person/gender'           => 'gender',
+        'contact/postalCode/home' => 'postcode',
+        'contact/country/home'    => 'country',
+        'pref/language'           => 'language',
+        'pref/timezone'           => 'timezone',
+        );
+    
+    # Math
+    private $add, $mul, $pow, $mod, $div, $powmod;
+    # -----
+    
+    # ------------------------------------------------------------------------ #
+    #  Functions you probably want to implement when extending the class.
+    
+    /**
+     * Checks whether an user is authenticated.
+     * The function should determine what fields it wants to send to the RP, 
+     * and put them in the $attributes array.
+     * @param Array $attributes
+     * @param String $realm Realm used for authentication.
+     * @return String OP-local identifier of an authenticated user, or an empty value.
+     */
+    abstract function checkid($realm, &$attributes);
+    
+    /**
+     * Displays an user interface for inputting user's login and password.
+     * Attributes are always AX field namespaces, with stripped host part.
+     * For example, the $attributes array may be:
+     * array( 'required' => array('namePerson/friendly', 'contact/email'),
+     *        'optional' => array('pref/timezone', 'pref/language')
+     * @param String $identity Discovered identity string. May be used to extract login, unless using $this->select_id
+     * @param String $realm Realm used for authentication.
+     * @param String Association handle. must be sent as openid.assoc_handle in $_GET or $_POST in subsequent requests.
+     * @param Array User attributes requested by the RP.
+     */
+    abstract function setup($identity, $realm, $assoc_handle, $attributes);
+    
+    /**
+     * Stores an association.
+     * If you want to use php sessions in your provider code, you have to replace it.
+     * @param String $handle Association handle -- should be used as a key.
+     * @param Array $assoc Association data.
+     */
+    protected function setAssoc($handle, $assoc)
+    {
+        $oldSession = session_id();
+        session_commit();
+        session_id($assoc['handle']);
+        session_start();
+        $_SESSION['assoc'] = $assoc;
+        session_commit();
+        if($oldSession) {
+            session_id($oldSession);
+            session_start();
+        }
+    }
+    
+    /**
+     * Retreives association data.
+     * If you want to use php sessions in your provider code, you have to replace it.
+     * @param String $handle Association handle.
+     * @return Array Association data.
+     */
+    protected function getAssoc($handle)
+    {
+        $oldSession = session_id();
+        session_commit();
+        session_id($handle);
+        session_start();
+        if(empty($_SESSION['assoc'])) {
+            return null;
+        }
+        return $_SESSION['assoc'];
+        session_commit();
+        if($oldSession) {
+            session_id($oldSession);
+            session_start();
+        }
+    }
+    
+    /**
+     * Deletes an association.
+     * If you want to use php sessions in your provider code, you have to replace it.
+     * @param String $handle Association handle.
+     */
+    protected function delAssoc($handle)
+    {
+        $oldSession = session_id();
+        session_commit();
+        session_id($handle);
+        session_start();
+        session_destroy();
+        if($oldSession) {
+            session_id($oldSession);
+            session_start();
+        }
+    }
+    
+    # ------------------------------------------------------------------------ #
+    # Functions that you might want to implement.
+    
+    /**
+     * Redirects the user to an url.
+     * @param String $location The url that the user will be redirected to.
+     */
+    protected function redirect($location)
+    {
+        header('Location: ' . $location);
+        die();
+    }
+    
+    /**
+     * Generates a new association handle.
+     * @return string
+     */
+    protected function assoc_handle()
+    {
+        return sha1(microtime());
+    }
+    
+    /**
+     * Generates a random shared secret.
+     * @return string
+     */
+    protected function shared_secret($hash)
+    {
+        $length = 20;
+        if($hash == 'sha256') {
+            $length = 256;
+        }
+        
+        $secret = '';
+        for($i = 0; $i < $length; $i++) {
+            $secret .= mt_rand(0,255);
+        }
+        
+        return $secret;
+    }
+    
+    /**
+     * Generates a private key.
+     * @param int $length Length of the key.
+     */
+    protected function keygen($length)
+    {
+        $key = '';
+        for($i = 1; $i < $length; $i++) {
+            $key .= mt_rand(0,9);
+        }
+        $key .= mt_rand(1,9);
+        
+        return $key;
+    }
+    
+    # ------------------------------------------------------------------------ #
+    # Functions that you probably shouldn't touch.
+    
+    function __construct()
+    {
+        $this->default_modulus = 
+            'ANz5OguIOXLsDhmYmsWizjEOHTdxfo2Vcbt2I3MYZuYe91ouJ4mLBX+YkcLiemOcPy'
+          . 'm2CBRYHNOyyjmG0mg3BVd9RcLn5S3IHHoXGHblzqdLFEi/368Ygo79JRnxTkXjgmY0'
+          . 'rxlJ5bU1zIKaSDuKdiI+XUkKJX8Fvf8W8vsixYOr';
+
+        $location = (!empty($_SERVER['HTTPS']) ? 'https' : 'http') . '://'
+                  . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
+        $location = preg_replace('/\?.*/','',$location);
+        $this->serverLocation = $location;
+        $location .= (strpos($location, '?') ? '&' : '?') . 'xrds';
+        $this->xrdsLocation = $location;
+        
+        $this->data = $_GET + $_POST;
+        
+        # We choose GMP if avaiable, and bcmath otherwise
+        if(function_exists('gmp_add')) {
+            $this->add = 'gmp_add';
+            $this->mul = 'gmp_mul';
+            $this->pow = 'gmp_pow';
+            $this->mod = 'gmp_mod';
+            $this->div = 'gmp_div';
+            $this->powmod = 'gmp_powm';
+        } elseif(function_exists('bcadd')) {
+            $this->add = 'bcadd';
+            $this->mul = 'bcmul';
+            $this->pow = 'bcpow';
+            $this->mod = 'bcmod';
+            $this->div = 'bcdiv';
+            $this->powmod = 'bcpowmod';
+        } else {
+            # If neither are avaiable, we can't use DH
+            $this->dh = false;
+        }
+        
+        # However, we do require the hash functions.
+        # They should be built-in anyway.
+        if(!function_exists('hash_algos')) {
+            $this->dh = false;
+        }
+    }
+    
+    /**
+     * Displays an XRDS document, or redirects to it.
+     * By default, it detects whether it should display or redirect automatically.
+     * @param bool|null $force When true, always display the document, when false always redirect.
+     */
+    function xrds($force=null)
+    {
+        if($force) {
+            echo $this->xrdsContent();
+            die();
+        } elseif($force === false) {
+            header('X-XRDS-Location: '. $this->xrdsLocation);
+            return;
+        }
+        
+        if (isset($_GET['xrds'])
+            || (isset($_SERVER['HTTP_ACCEPT']) &&  strpos($_SERVER['HTTP_ACCEPT'], 'application/xrds+xml') !== false)
+        ) {
+            header('Content-Type: application/xrds+xml');
+            echo $this->xrdsContent();
+            die();
+        }
+        
+        header('X-XRDS-Location: ' . $this->xrdsLocation);
+    }
+    
+    /**
+     * Returns the content of the XRDS document
+     * @return String The XRDS document.
+     */
+    protected function xrdsContent()
+    {
+        $lines = array(
+            '<?xml version="1.0" encoding="UTF-8"?>',
+            '<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">',
+            '<XRD>',
+            '    <Service>',
+            '        <Type>' . $this->ns . '/' . ($this->select_id ? 'server' : 'signon') .'</Type>',
+            '        <URI>' . $this->serverLocation . '</URI>',
+            '    </Service>',
+            '</XRD>',
+            '</xrds:XRDS>'
+            );
+        return implode("\n", $lines);
+    }
+    
+    /**
+     * Does everything that a provider has to -- in one function.
+     */
+    function server()
+    {
+        if(isset($this->data['openid_assoc_handle'])) {
+            $this->assoc = $this->getAssoc($this->data['openid_assoc_handle']);
+            if(isset($this->assoc['data'])) {
+                # We have additional data stored for setup.
+                $this->data += $this->assoc['data'];
+                unset($this->assoc['data']);
+            }
+        }
+            
+        if (isset($this->data['openid_ns'])
+            && $this->data['openid_ns'] == $this->ns
+        ) {
+            if(!isset($this->data['openid_mode'])) $this->errorResponse();
+            
+            switch($this->data['openid_mode'])
+            { 
+            case 'checkid_immediate':
+            case 'checkid_setup':
+                $this->checkRealm();
+                # We support AX xor SREG.
+                $attributes = $this->ax();
+                if(!$attributes) {
+                    $attributes = $this->sreg();
+                }
+                
+                # Even if some user is authenticated, we need to know if it's
+                # the same one that want's to authenticate.
+                # Of course, if we use select_id, we accept any user.
+                if (($identity = $this->checkid($this->data['openid_realm'], $attrValues))
+                    && ($this->select_id || $identity == $this->data['openid_identity'])
+                ) {
+                    $this->positiveResponse($identity, $attrValues);
+                } elseif($this->data['openid_mode'] == 'checkid_immediate') {
+                    $this->redirect($this->response(array('openid.mode' => 'setup_needed')));
+                } else {
+                    if(!$this->assoc) {
+                        $this->generateAssociation();
+                        $this->assoc['private'] = true;
+                    }
+                    $this->assoc['data'] = $this->data;
+                    $this->setAssoc($this->assoc['handle'], $this->assoc);
+                    $this->setup($this->data['openid_identity'],
+                                 $this->data['openid_realm'],
+                                 $this->assoc['handle'],
+                                 $attributes);
+                }
+                break;
+            case 'associate':
+                $this->associate();
+                break;
+            case 'check_authentication':
+                $this->checkRealm();
+                if($this->verify()) {
+                    echo "ns:$this->ns\nis_valid:true";
+                    if(strpos($this->data['openid_signed'],'invalidate_handle') !== false) {
+                        echo "\ninvalidate_handle:" . $this->data['openid_invalidate_handle'];
+                    }
+                } else {
+                    echo "ns:$this->ns\nis_valid:false";
+                }
+                die();
+                break;
+            default:
+                $this->errorResponse();
+            }
+        } else {
+            $this->xrds();
+        }
+    }
+    
+    protected function checkRealm()
+    {
+        if (!isset($this->data['openid_return_to'], $this->data['openid_realm'])) {
+            $this->errorResponse();
+        }
+        
+        $realm = str_replace('\*', '[^/]', preg_quote($this->data['openid_realm']));
+        if(!preg_match("#^$realm#", $this->data['openid_return_to'])) {
+            $this->errorResponse();
+        }
+    }
+    
+    protected function ax()
+    {
+        # Namespace prefix that the fields must have.
+        $ns = 'http://axschema.org/';
+        
+        # First, we must find out what alias is used for AX.
+        # Let's check the most likely one
+        $alias = null;
+        if (isset($this->data['openid_ns_ax'])
+            && $this->data['openid_ns_ax'] == 'http://openid.net/srv/ax/1.0'
+        ) {
+            $alias = 'ax';
+        } else {
+            foreach($this->data as $name => $value) {
+                if ($value == 'http://openid.net/srv/ax/1.0'
+                    && preg_match('/openid_ns_(.+)/', $name, $m)
+                ) {
+                    $alias = $m[1];
+                    break;
+                }
+            }
+        }
+        
+        if(!$alias) {
+            return null;
+        }
+        
+        $fields = array();
+        # Now, we must search again, this time for field aliases
+        foreach($this->data as $name => $value) {
+            if (strpos($name, 'openid_' . $alias . '_type') === false
+                || strpos($value, $ns) === false) {
+                continue;
+            }
+            
+            $name = substr($name, strlen('openid_' . $alias . '_type_'));
+            $value = substr($value, strlen($ns));
+            
+            $fields[$name] = $value;
+        }
+        
+        # Then, we find out what fields are required and optional
+        $required = array();
+        $if_available = array();
+        foreach(array('required','if_available') as $type) {
+            if(empty($this->data["openid_{$alias}_{$type}"])) {
+                continue;
+            }
+            $attributes = explode(',', $this->data["openid_{$alias}_{$type}"]);
+            foreach($attributes as $attr) {
+                if(empty($fields[$attr])) {
+                    # There is an undefined field here, so we ignore it.
+                    continue;
+                }
+                
+                ${$type}[] = $fields[$attr];
+            }
+        }
+        
+        $this->data['ax'] = true;
+        return array('required' => $required, 'optional' => $if_available);
+    }
+    
+    protected function sreg()
+    {
+        $sreg_to_ax = array_flip($this->ax_to_sreg);
+        
+        $attributes = array('required' => array(), 'optional' => array());
+        
+        if (empty($this->data['openid_sreg_required'])
+            && empty($this->data['openid_sreg_optional'])
+        ) {
+            return $attributes;
+        }
+        
+        foreach(array('required', 'optional') as $type) {
+            foreach(explode(',',$this->data['openid_sreg_' . $type]) as $attr) {
+                if(empty($sreg_to_ax[$attr])) {
+                    # Undefined attribute in SREG request.
+                    # Shouldn't happen, but we check anyway.
+                    continue;
+                }
+                
+                $attributes[$type][] = $sreg_to_ax[$attr];
+            }
+        }
+        
+        return $attributes;
+    }
+    
+    /**
+     * Aids an RP in assertion verification.
+     * @return bool Information whether the verification suceeded.
+     */
+    protected function verify()
+    {
+        # Firstly, we need to make sure that there's an association.
+        # Otherwise the verification will fail, 
+        # because we've signed assoc_handle in the assertion
+        if(empty($this->assoc)) {
+            return false;
+        }
+        
+        # Next, we check that it's a private association, 
+        # i.e. one made without RP input.
+        # Otherwise, the RP shouldn't ask us to verify.
+        if(empty($this->assoc['private'])) {
+            return false;
+        }
+        
+        # Now we have to check if the nonce is correct, to prevent replay attacks.
+        if($this->data['openid_response_nonce'] != $this->assoc['nonce']) {
+            return false;
+        }
+        
+        # Getting the signed fields for signature.
+        $sig = array();
+        $signed = explode(',', $this->data['openid_signed']);
+        foreach($signed as $field) {
+            $name = strtr($field, '.', '_');
+            if(!isset($this->data['openid_' . $name])) {
+                return false;
+            }
+            
+            $sig[$field] = $this->data['openid_' . $name];
+        }
+        
+        # Computing the signature and checking if it matches.
+        $sig = $this->keyValueForm($sig);
+        if ($this->data['openid_sig'] != 
+            base64_encode(hash_hmac($this->assoc['hash'], $sig, $this->assoc['mac'], true))
+        ) {
+            return false;
+        }
+        
+        # Clearing the nonce, so that it won't be used again.
+        $this->assoc['nonce'] = null;
+        
+        if(empty($this->assoc['private'])) {
+            # Commiting changes to the association.
+            $this->setAssoc($this->assoc['handle'], $this->assoc);
+        } else {
+            # Private associations shouldn't be used again, se we can as well delete them.
+            $this->delAssoc($this->assoc['handle']);
+        }
+        
+        # Nothing has failed, so the verification was a success.
+        return true;
+    }
+    
+    /**
+     * Performs association with an RP.
+     */
+    protected function associate()
+    {
+        # Rejecting no-encryption without TLS.
+        if(empty($_SERVER['HTTPS']) && $this->data['openid_session_type'] == 'no-encryption') {
+            $this->directErrorResponse();
+        }
+        
+        # Checking whether we support DH at all.
+        if (!$this->dh && substr($this->data['openid_session_type'], 0, 2) == 'DH') {
+            $this->redirect($this->response(array(
+                'openid.error' => 'DH not supported',
+                'openid.error_code' => 'unsupported-type',
+                'openid.session_type' => 'no-encryption'
+                )));
+        }
+        
+        # Creating the association
+        $this->assoc = array();
+        $this->assoc['hash'] = $this->data['openid_assoc_type'] == 'HMAC-SHA256' ? 'sha256' : 'sha1';
+        $this->assoc['handle'] = $this->assoc_handle();
+        
+        # Getting the shared secret
+        if($this->data['openid_session_type'] == 'no-encryption') {
+            $this->assoc['mac'] = base64_encode($this->shared_secret($this->assoc['hash']));
+        } else {
+            $this->dh();
+        }
+        
+        # Preparing the direct response...
+        $response = array(
+            'ns'           => $this->ns,
+            'assoc_handle' => $this->assoc['handle'],
+            'assoc_type'   => $this->data['openid_assoc_type'],
+            'session_type' => $this->data['openid_session_type'],
+            'expires_in'   => $this->assoc_lifetime
+            );
+        
+        if(isset($this->assoc['dh_server_public'])) {
+            $response['dh_server_public'] = $this->assoc['dh_server_public'];
+            $response['enc_mac_key'] = $this->assoc['mac'];
+        } else {
+            $response['mac_key'] = $this->assoc['mac'];
+        }
+        
+        # ...and sending it.
+        echo $this->keyValueForm($response);
+        die();
+    }
+    
+    /**
+     * Creates a private association.
+     */
+    protected function generateAssociation()
+    {
+        $this->assoc = array();
+        # We use sha1 by default.
+        $this->assoc['hash']   = 'sha1';
+        $this->assoc['mac']    = $this->shared_secret('sha1');
+        $this->assoc['handle'] = $this->assoc_handle();
+    }
+    
+    /**
+     * Encrypts the MAC key using DH key exchange.
+     */
+    protected function dh()
+    {
+        if(empty($this->data['openid_dh_modulus'])) {
+            $this->data['openid_dh_modulus'] = $this->default_modulus;
+        }
+        
+        if(empty($this->data['openid_dh_gen'])) {
+            $this->data['openid_dh_gen'] = $this->default_gen;
+        }
+        
+        if(empty($this->data['openid_dh_consumer_public'])) {
+            $this->directErrorResponse();
+        }
+        
+        $modulus = $this->b64dec($this->data['openid_dh_modulus']);
+        $gen = $this->b64dec($this->data['openid_dh_gen']);
+        $consumerKey = $this->b64dec($this->data['openid_dh_consumer_public']);
+        
+        $privateKey = $this->keygen(strlen($modulus));
+        $publicKey = $this->powmod($gen, $privateKey, $modulus);
+        $ss = $this->powmod($consumerKey, $privateKey, $modulus);
+        
+        $mac = $this->x_or(hash($this->assoc['hash'], $ss, true), $this->shared_secret($this->assoc['hash']));
+        $this->assoc['dh_server_public'] = $this->decb64($publicKey);
+        $this->assoc['mac'] = base64_encode($mac);
+    }
+    
+    /**
+     * XORs two strings.
+     * @param String $a
+     * @param String $b
+     * @return String $a ^ $b
+     */
+    protected function x_or($a, $b)
+    {
+        $length = strlen($a);
+        for($i = 0; $i < $length; $i++) {
+            $a[$i] = $a[$i] ^ $b[$i];
+        }
+        
+        return $a;
+    }
+    
+    /**
+     * Prepares an indirect response url.
+     * @param array $params Parameters to be sent.
+     */
+    protected function response($params)
+    {
+        $params += array('openid.ns' => $this->ns);
+        return $this->data['openid_return_to']
+             . (strpos($this->data['openid_return_to'],'?') ? '&' : '?')
+             . http_build_query($params, '', '&');
+    }
+    
+    /**
+     * Outputs a direct error.
+     */
+    protected function errorResponse()
+    {
+        if(!empty($this->data['openid_return_to'])) {
+            $response = array(
+            'openid.mode'  => 'error',
+            'openid.error' => 'Invalid request'
+            );
+            $this->redirect($this->response($response));
+        } else {
+            header('HTTP/1.1 400 Bad Request');
+            $response = array(
+                'ns' => $this->ns,
+                'error' => 'Invalid request'
+                );
+            echo $this->keyValueForm($response);
+        }
+        die();
+    }
+    
+    /**
+     * Sends an positive assertion.
+     * @param String $identity the OP-Local Identifier that is being authenticated.
+     * @param Array $attributes User attributes to be sent.
+     */
+    protected function positiveResponse($identity, $attributes)
+    {
+        # We generate a private association if there is none established.
+        if(!$this->assoc) {
+            $this->generateAssociation();
+            $this->assoc['private'] = true;
+        }
+        
+        # We set openid.identity (and openid.claimed_id if necessary) to our $identity
+        if($this->data['openid_identity'] == $this->data['openid_claimed_id'] || $this->select_id) {
+            $this->data['openid_claimed_id'] = $identity;
+        }
+        $this->data['openid_identity'] = $identity;
+        
+        # Preparing fields to be signed
+        $params = array(
+            'op_endpoint'    => $this->serverLocation,
+            'claimed_id'     => $this->data['openid_claimed_id'],
+            'identity'       => $this->data['openid_identity'],
+            'return_to'      => $this->data['openid_return_to'],
+            'realm'          => $this->data['openid_realm'],
+            'response_nonce' => gmdate("Y-m-d\TH:i:s\Z"),
+            'assoc_handle'   => $this->assoc['handle'],
+            );
+        
+        $params += $this->responseAttributes($attributes);
+        
+        # Has the RP used an invalid association handle?
+        if (isset($this->data['openid_assoc_handle'])
+            && $this->data['openid_assoc_handle'] != $this->assoc['handle']
+        ) {
+            $params['invalidate_handle'] = $this->data['openid_assoc_handle'];
+        }
+        
+        # Signing the $params
+        $sig = hash_hmac($this->assoc['hash'], $this->keyValueForm($params), $this->assoc['mac'], true);
+        $req = array(
+            'openid.mode'   => 'id_res',
+            'openid.signed' => implode(',', array_keys($params)),
+            'openid.sig'    => base64_encode($sig),
+            );
+        
+        # Saving the nonce and commiting the association.
+        $this->assoc['nonce'] = $params['response_nonce'];
+        $this->setAssoc($this->assoc['handle'], $this->assoc);
+        
+        # Preparing and sending the response itself
+        foreach($params as $name => $value) {
+            $req['openid.' . $name] = $value;
+        }
+        
+        $this->redirect($this->response($req));
+    }
+    
+    /**
+     * Prepares an array of attributes to send
+     */
+    protected function responseAttributes($attributes)
+    {
+        if(!$attributes) return array();
+        
+        $ns = 'http://axschema.org/';
+
+        $response = array();
+        if(isset($this->data['ax'])) {
+            $response['ns.ax'] = 'http://openid.net/srv/ax/1.0';
+            foreach($attributes as $name => $value) {
+                $alias = strtr($name, '/', '_');
+                $response['ax.type.' . $alias] = $ns . $name;
+                $response['ax.value.' . $alias] = $value;
+            }
+            return $response;
+        }
+        
+        foreach($attributes as $name => $value) {
+            if(!isset($this->ax_to_sreg[$name])) {
+                continue;
+            }
+            
+            $response['sreg.' . $this->ax_to_sreg[$name]] = $value;
+        }
+        return $response;
+    }
+    
+    /**
+     * Encodes fields in key-value form.
+     * @param Array $params Fields to be encoded.
+     * @return String $params in key-value form.
+     */
+    protected function keyValueForm($params)
+    {
+        $str = '';
+        foreach($params as $name => $value) {
+            $str .= "$name:$value\n";
+        }
+        
+        return $str;
+    }
+    
+    /**
+     * Responds with an information that the user has canceled authentication.
+     */
+    protected function cancel()
+    {
+        $this->redirect($this->response(array('openid.mode' => 'cancel')));
+    }
+    
+    /**
+     * Converts base64 encoded number to it's decimal representation.
+     * @param String $str base64 encoded number.
+     * @return String Decimal representation of that number.
+     */
+    protected function b64dec($str)
+    {
+        $bytes = unpack('C*', base64_decode($str));
+        $n = 0;
+        foreach($bytes as $byte) {
+            $n = $this->add($this->mul($n, 256), $byte);
+        }
+        
+        return $n;
+    }
+    
+    /**
+     * Complements b64dec.
+     */
+    protected function decb64($num)
+    {
+        $bytes = array();
+        while($num) {
+            array_unshift($bytes, $this->mod($num, 256));
+            $num = $this->div($num, 256);
+        }
+        
+        if($bytes && $bytes[0] > 127) {
+            array_unshift($bytes,0);
+        }
+        
+        array_unshift($bytes, 'C*');
+        
+        return base64_encode(call_user_func_array('pack', $bytes));
+    }
+    
+    function __call($name, $args)
+    {
+        switch($name) {
+        case 'add':
+        case 'mul':
+        case 'pow':
+        case 'mod':
+        case 'div':
+        case 'powmod':
+            if(function_exists('gmp_strval')) {
+                return gmp_strval(call_user_func_array($this->$name, $args));
+            }
+            return call_user_func_array($this->$name, $args);
+        default:
+            throw new BadMethodCallException();
+        }
+    }
+}