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<?php
// Thrown when internal error occurs
class JasigException extends Exception {}
// Thrown when CAS server return authentication error
class JasigAuthException extends JasigException {}
 
class JasigUser {
    public $user;
    public $attributes = array();
}
 
class uphpCAS {
    const VERSION = '1.0';
    protected $serverUrl = '';
    protected $serviceUrl;
    
    function __construct($serverUrl = NULL, $serviceUrl = NULL) {
        if($serverUrl != NULL) {
            $this->serverUrl = rtrim($serverUrl, '/');
        }
        
        if($serviceUrl != NULL) {
            $this->serviceUrl = $serviceUrl;
        } else {
            $url = 'http://';
            $port = 0;
            if(isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') {
                $url = 'https://';
                if(isset($_SERVER['SERVER_PORT']) && $_SERVER['SERVER_PORT'] != '443') {
                    $port = $_SERVER['SERVER_PORT'];
                }
            } elseif(isset($_SERVER['SERVER_PORT']) && $_SERVER['SERVER_PORT'] != '80') {
                $port = $_SERVER['SERVER_PORT'];
            }
            
            $url .= $_SERVER['SERVER_NAME'];
            
            if($port != 0) {
                $url .= ':'.$port;
            }
            $url .= $_SERVER['REQUEST_URI'];
            
            $this->serviceUrl = $url;
        }
    }
    
    public function setServerUrl($serverUrl) {
        $this->serverUrl = $serverUrl;
    }
    
    public function setServiceUrl($serviceUrl) {
        $this->serviceUrl = $serviceUrl;
    }
    
    public function loginUrl() {
        return $this->serverUrl.'/login?service='.urlencode($this->serviceUrl);
    }
    
    public function logoutUrl() {
        return $this->serverUrl.'/logout';
    }
    
    public function logout() {
        session_start();
        if(isset($_SESSION['uphpCAS-user'])) {
            unset($_SESSION['uphpCAS-user']);
        }
        header('Location: '.$this->logoutUrl());
        die();
    }
    
    public function authenticate() {
        session_start();
        if(isset($_SESSION['uphpCAS-user'])) {
            return $_SESSION['uphpCAS-user'];
        } elseif(isset($_GET['ticket'])) {
            $user = $this->verifyTicket($_GET['ticket']);
            $_SESSION['uphpCAS-user'] = $user;
            return $user;
        } else {
            header('Location: '.$this->loginUrl());
            die();
        }
    }
    
    public function verifyTicket($ticket) {
        $context = array(
            'http' => array(
                'method' => 'GET',
                'user_agent' => 'uphpCAS/'.self::VERSION,
                'max_redirects' => 3,
            ),
            'ssl' => array(
                'verify_peer' => TRUE,
                'allow_self_signed' => FALSE,
                'verify_depth' => 5,
                'ciphers' => 'HIGH:-MD5:-aNULL:-DES',
            ),
        );
        
        $data = file_get_contents($this->serverUrl.'/serviceValidate?service='.urlencode($this->serviceUrl).'&ticket='.urlencode($ticket),
                FALSE, stream_context_create($context));
        if($data === FALSE) {
            throw new JasigException('Authentication error: CAS server is unavailable');
        }
        
        $xmlEntityLoader = libxml_disable_entity_loader(TRUE);
        $xmlInternalErrors = libxml_use_internal_errors(TRUE);
        try {
            $xml = new DOMDocument();
            $xml->loadXML($data);
            
            foreach(libxml_get_errors() as $error) {
                $e = new ErrorException($error->message, $error->code, 1, $error->file, $error->line);
                switch ($error->level) {
                    case LIBXML_ERR_ERROR:
                        throw new Exception('Fatal error during XML parsing', 0, $e);
                        break;
                    case LIBXML_ERR_FATAL:
                        throw new Exception('Fatal error during XML parsing', 0, $e);
                        break;
                }
            }
        }
        catch(Exception $e) {
            throw new JasigException('Authentication error: CAS server response invalid - parse error', 0, $e);
        } finally {
            libxml_clear_errors();
            libxml_disable_entity_loader($xmlEntityLoader);
            libxml_use_internal_errors($xmlInternalErrors);
        }
        
        $failure = $xml->getElementsByTagName('authenticationFailure');
        $success = $xml->getElementsByTagName('authenticationSuccess');
        
        if($failure->length > 0) {
            $failure = $failure->item(0);
            if(!($failure instanceof DOMElement)) {
                throw new JasigException('Authentication error: CAS server response invalid - authenticationFailure');
            }
            throw new JasigAuthException('Authentication error: '.$failure->textContent);
        } elseif($success->length > 0) {
            $success = $success->item(0);
            if(!($success instanceof DOMElement)) {
                throw new JasigException('Authentication error: CAS server response invalid - authenticationSuccess');
            }
            
            $user = $success->getElementsByTagName('user');
            if($user->length == 0) {
                throw new JasigException('Authentication error: CAS server response invalid - user');
            }
            
            $user = trim($user->item(0)->textContent);
            if(strlen($user)<1) {
                throw new JasigException('Authentication error: CAS server response invalid - user value');
            }
            
            $jusr = new JasigUser();
            $jusr->user = $user;
            
            $attrs = $success->getElementsByTagName('attributes');
            if($attrs->length > 0) {
                $attrs = $attrs->item(0);
                foreach($attrs->childNodes as $node) {
                    $jusr->attributes[$node->localName] = $node->textContent;
                }
            }
            
            return $jusr;
        }
        else
        {
            throw new JasigException('Authentication error: CAS server response invalid - required tag not found');
        }
    }
}