<?php
// Based on / inspired by: https://github.com/PHPGangsta/GoogleAuthenticator
// Algorithms, digits, period etc. explained: https://code.google.com/p/google-authenticator/wiki/KeyUriFormat
class TwoFactorAuth 
{
    private $algorithm;
    private $period;
    private $digits;
    private $issuer;
    private $qrcodeprovider;
    private static $_base32;
    private static $_base32lookup = array();
    private static $_supportedalgos = array('sha1', 'sha256', 'sha512', 'md5');
    
    function __construct($issuer = null, $digits = 6, $period = 30, $algorithm = 'sha1', $qrcodeprovider = null) 
    {
        $this->issuer = $issuer;

        if (!is_int($digits) || $digits <= 0)
            throw new Exception('Digits must be int > 0');
        $this->digits = $digits;
        
        if (!is_int($period) || $period <= 0)
            throw new Exception('Period must be int > 0');
        $this->period = $period;
        
        $algorithm = strtolower(trim($algorithm));
        if (!in_array($algorithm, self::$_supportedalgos))
            throw new Exception('Unsupported algorithm: ' . $algorithm);
        $this->algorithm = $algorithm;
        
        if ($qrcodeprovider==null)
            $qrcodeprovider = new GoogleQRCodeProvider();
        
        if (!($qrcodeprovider instanceof IQRCodeProvider))
            throw new Exception('QRCodeProvider must implement IQRCodeProvider');
        
        $this->qrcodeprovider = $qrcodeprovider;
        
        self::$_base32 = str_split('ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=');
        self::$_base32lookup = array_flip(self::$_base32);
    }
    
    /**
     * Create a new secret
     */
    public function createSecret($bits = 80) 
    {
        $secret = '';
        $bytes = ceil($bits / 5);   //We use 5 bits of each byte
        $rnd = openssl_random_pseudo_bytes($bytes);
        for ($i = 0; $i < $bytes; $i++)
            $secret .= self::$_base32[ord($rnd[$i]) & 31];  //Mask out left 3 bits for 0-31 values
        return $secret;
    }
    
    /**
     * Calculate the code with given secret and point in time
     */
    public function getCode($secret, $time = null)
    {
        $secretkey = $this->base32Decode($secret);
        
        $ts = "\0\0\0\0" . pack('N*', $this->getTimeSlice($this->getTime($time)));  // Pack time into binary string
        $hm = hash_hmac($this->algorithm, $ts, $secretkey, true);                   // Hash it with users secret key
        $hashpart = substr($hm, ord(substr($hm, -1)) & 0x0F, 4);                    // Use last nibble of result as index/offset and grab 4 bytes of the result
        $value = unpack('N', $hashpart);                                            // Unpack binary value
        $value = $value[1] & 0x7FFFFFFF;                                            // Drop MSB, keep only 31 bits
        
        return str_pad($value % pow(10, $this->digits), $this->digits, '0', STR_PAD_LEFT);
    }
    
    /**
     * Check if the code is correct. This will accept codes starting from ($discrepancy * $period) sec ago to ($discrepancy * period) sec from now
     */
    public function verifyCode($secret, $code, $discrepancy = 1, $time = null)
    {
        $t = $this->getTime($time);
        for ($i = -$discrepancy; $i <= $discrepancy; $i++) 
        {
            if (strcmp($this->getCode($secret, $t + ($i * $this->period)), $code) === 0)
                return true;
        }
        
        return false;
    }
    
    /**
     * Get data-uri of QRCode
     */
    public function getQRCodeImageAsDataUri($label, $secret, $size = 200) 
    {
        if (!is_int($size) || $size < 0)
            throw new  Exception('Size must be int > 0');
        
        return 'data:'
            . $this->qrcodeprovider->getMimeType()
            . ';base64,'
            . base64_encode($this->qrcodeprovider->getQRCodeImage($this->getQRText($label, $secret), $size));
    }
    
    private function getTime($time) 
    {
        return ($time === null) ? time() : $time;
    }
    
    private function getTimeSlice($time = null, $offset = 0) 
    {
        return (int)floor($time / $this->period) + ($offset * $this->period);
    }
    
    /**
     * Builds a string to be encoded in a QR code
     */
    private function getQRText($label, $secret) 
    {
        return 'otpauth://totp/' . rawurlencode($label)
            . '?secret=' . rawurlencode($secret)
            . '&issuer=' . rawurlencode($this->issuer)
            . '&period=' . intval($this->period)
            . '&algorithm=' . rawurlencode(strtoupper($this->algorithm))
            . '&digits=' . intval($this->digits);
    }
    
    private function base32Decode($value)
    {
        if (strlen($value)==0) return '';
        
        $s = '';
        foreach (str_split($value) as $c) 
        {
            if ($c !== '=')
                $s .= str_pad(decbin(self::$_base32lookup[$c]), 5, 0, STR_PAD_LEFT);
        }
        $l = strlen($s);
        $r = trim(chunk_split(substr($s, 0, $l - ($l % 8)), 8, ' '));
        
		$o = '';
		foreach (explode(' ', $r) as $b)
            $o .= chr(bindec(str_pad($b, 8, 0, STR_PAD_RIGHT)));

		return $o;
    }
}

interface IQRCodeProvider
{
	public function getQRCodeImage($qrtext, $size);
    public function getMimeType();
}

abstract class BaseHTTPQRCodeProvider implements IQRCodeProvider
{
    protected $verifyssl;

	protected function getContent($url)
    {
        $ch = curl_init();
        
        curl_setopt_array($ch, array(
			CURLOPT_URL => $url,
			CURLOPT_FOLLOWLOCATION => true,
			CURLOPT_MAXREDIRS => 3,
			CURLOPT_RETURNTRANSFER => true,
			CURLOPT_CONNECTTIMEOUT => 10,
			CURLOPT_DNS_CACHE_TIMEOUT => 10,
			CURLOPT_TIMEOUT => 10,
            CURLOPT_SSL_VERIFYPEER => $this->verifyssl,
			CURLOPT_USERAGENT => 'TwoFactorAuth'
        ));
        $data = curl_exec($ch);
        
        curl_close($ch);
        return $data;
    }
}

// https://developers.google.com/chart/infographics/docs/qr_codes
class GoogleQRCodeProvider extends BaseHTTPQRCodeProvider 
{
    public $errorcorrectionlevel;
    public $margin;

    function __construct($verifyssl = false, $errorcorrectionlevel = 'L', $margin = 1) 
    {
        if (!is_bool($verifyssl))
            throw new Exception('VerifySSL must be bool');

        $this->verifyssl = $verifyssl;
        
        $this->errorcorrectionlevel = $errorcorrectionlevel;
        $this->margin = $margin;
    }
    
    public function getMimeType() 
    {
        return 'image/png';
    }
    
    public function getQRCodeImage($qrtext, $size) 
    {
        return $this->getContent($this->getUrl($qrtext, $size));
    }
    
    public function getUrl($qrtext, $size) 
    {
        return 'https://chart.googleapis.com/chart?cht=qr'
            . '&chs=' . $size . 'x' . $size
            . '&chld=' . $this->errorcorrectionlevel . '|' . $this->margin
            . '&chl=' . rawurlencode($qrtext);
    }
}

// http://goqr.me/api/doc/create-qr-code/
class QRServerProvider extends BaseHTTPQRCodeProvider 
{
    public $errorcorrectionlevel;
    public $margin;
    public $qzone;
    public $bgcolor;
    public $color;
    public $format;

    function __construct($verifyssl = false, $errorcorrectionlevel = 'L', $margin = 4, $qzone = 1, $bgcolor = 'ffffff', $color = '000000', $format = 'png') 
    {
        if (!is_bool($verifyssl))
            throw new Exception('VerifySSL must be bool');

        $this->verifyssl = $verifyssl;
        
        $this->errorcorrectionlevel = $errorcorrectionlevel;
        $this->margin = $margin;
        $this->qzone = $qzone;
        $this->bgcolor = $bgcolor;
        $this->color = $color;
        $this->format = $format;
    }
    
    public function getMimeType() 
    {
        switch (strtolower($this->format))
        {
        	case 'png':
                return 'image/png';
        	case 'gif':
                return 'image/gif';
        	case 'jpg':
        	case 'jpeg':
                return 'image/jpeg';
        	case 'svg':
                return 'image/svg+xml';
        	case 'eps':
                return 'application/postscript';
        }
    }
    
    public function getQRCodeImage($qrtext, $size) 
    {
        return $this->getContent($this->getUrl($qrtext, $size));
    }
    
    private function decodeColor($value) 
    {
        return vsprintf('%d-%d-%d', sscanf($value, "%02x%02x%02x"));
    }
    
    public function getUrl($qrtext, $size) 
    {
        return 'https://api.qrserver.com/v1/create-qr-code/'
            . '?size=' . $size . 'x' . $size
            . '&ecc=' . strtoupper($this->errorcorrectionlevel)
            . '&margin=' . $this->margin
            . '&qzone=' . $this->qzone
            . '&bgcolor=' . $this->decodeColor($this->bgcolor)
            . '&color=' . $this->decodeColor($this->color)
            . '&format=' . strtolower($this->format)
            . '&data=' . rawurlencode($qrtext);
    }
}

// http://qrickit.com/qrickit_apps/qrickit_api.php
class QRicketProvider extends BaseHTTPQRCodeProvider 
{
    public $errorcorrectionlevel;
    public $margin;
    public $qzone;
    public $bgcolor;
    public $color;
    public $format;

    function __construct($errorcorrectionlevel = 'L', $bgcolor = 'ffffff', $color = '000000', $format = 'p') 
    {
        $this->verifyssl = false;
        
        $this->errorcorrectionlevel = $errorcorrectionlevel;
        $this->bgcolor = $bgcolor;
        $this->color = $color;
        $this->format = $format;
    }
    
    public function getMimeType() 
    {
        switch (strtolower($this->format))
        {
        	case 'p':
                return 'image/png';
        	case 'g':
                return 'image/gif';
        	case 'j':
                return 'image/jpeg';
        }
    }
    
    public function getQRCodeImage($qrtext, $size) 
    {
        return $this->getContent($this->getUrl($qrtext, $size));
    }
    
    public function getUrl($qrtext, $size) 
    {
        return 'http://qrickit.com/api/qr'
            . '?qrsize=' . $size
            . '&e=' . strtolower($this->errorcorrectionlevel)
            . '&bgdcolor=' . $this->bgcolor
            . '&fgdcolor=' . $this->color
            . '&t=' . strtolower($this->format)
            . '&d=' . rawurlencode($qrtext);
    }
}