接入google-authenticator opt（one time password一次性密码）

参考资源：

https://github.com/ruansheng/technology-study/blob/master/other/otp.md

百度百科：

一次性密码（One Time Password，简称OTP），又称“一次性口令”，是指只能使用一次的密码。一次性密码是根据专门算法、每隔30或60秒生成一个不可预测的随机数字组合。

实现原理：

动态密码是基于时间、口令密钥按照特定的算法所生成的随机数字组合。

现在我们讲一下应用比较广泛的动态密码生成器google-authenticator。

authenticator给我们提供了接入协议，格式如下：

格式：otpauth://totp/52min.net?secret=IH2AGN774DGNNA2N&period=30&digits=8&issuer=Alias

    52min.net ：密码来源，用于描述密码。

    secret ：口令种子密钥，每个用户拥有唯一的secret。用户的唯一表示为secret的生成参数。

    period ：【可选参数】密码的有效时间，默认30S

    Digits ：【可选参数】密码的长度，默认6字符

    issuer ：【可选参数】密码别名，用于描述密码。

用户可以根据otpauth://totp/52min.net?secret=IH2AGN774DGNNA2N&period=30&digits=8&issuer=Alias

生成二维码，用于密码生成器扫码获取当前密码。

验证原理：

通过用户输入的标识信息（比如：手机号）生成16位secret。

使用secret通过与密码生成器相同的加密算法，生成password1。

比较用户输入的password 是否与password1相同，如果相同密码有效，反之无效。

代码实现：

<?php

/**
 * Class PHPGangsta_GoogleAuthenticator
 */
class PHPGangsta_GoogleAuthenticator
{
    protected $_codeLength = 6;

    /**
     * Create new secret.
     * 16 characters, randomly chosen from the allowed base32 characters.
     *
     * @param int $secretLength
     *
     * @return string
     */
    public function createSecret($secretLength = 16)
    {
        $validChars = $this->_getBase32LookupTable();

        // Valid secret lengths are 80 to 640 bits
        if ($secretLength < 16 || $secretLength > 128) {
            throw new Exception('Bad secret length');
        }
        $secret = '';
        $rnd = false;
        if (function_exists('random_bytes')) {
            $rnd = random_bytes($secretLength);
        } elseif (function_exists('mcrypt_create_iv')) {
            $rnd = mcrypt_create_iv($secretLength, MCRYPT_DEV_URANDOM);
        } elseif (function_exists('openssl_random_pseudo_bytes')) {
            $rnd = openssl_random_pseudo_bytes($secretLength, $cryptoStrong);
            if (!$cryptoStrong) {
                $rnd = false;
            }
        }
        if ($rnd !== false) {
            for ($i = 0; $i < $secretLength; ++$i) {
                $secret .= $validChars[ord($rnd[$i]) & 31];
            }
        } else {
            throw new Exception('No source of secure random');
        }

        return $secret;
    }

    /**
     * Calculate the code, with given secret and point in time.
     *
     * @param string   $secret
     * @param int|null $timeSlice
     *
     * @return string
     */
    public function getCode($secret, $timeSlice = null)
    {
        if ($timeSlice === null) {
            $timeSlice = floor(time() / 30);
        }

        $secretkey = $this->_base32Decode($secret);

        // Pack time into binary string
        $time = chr(0).chr(0).chr(0).chr(0).pack('N*', $timeSlice);
        // Hash it with users secret key
        $hm = hash_hmac('SHA1', $time, $secretkey, true);
        // Use last nipple of result as index/offset
        $offset = ord(substr($hm, -1)) & 0x0F;
        // grab 4 bytes of the result
        $hashpart = substr($hm, $offset, 4);

        // Unpak binary value
        $value = unpack('N', $hashpart);
        $value = $value[1];
        // Only 32 bits
        $value = $value & 0x7FFFFFFF;

        $modulo = pow(10, $this->_codeLength);

        return str_pad($value % $modulo, $this->_codeLength, '0', STR_PAD_LEFT);
    }

    /**
     * Get QR-Code URL for image, from google charts.
     *
     * @param string $name
     * @param string $secret
     * @param string $title
     * @param array  $params
     *
     * @return string
     */
    public function getQRCodeGoogleUrl($name, $secret, $title = null, $params = array())
    {
        $width = !empty($params['width']) && (int) $params['width'] > 0 ? (int) $params['width'] : 200;
        $height = !empty($params['height']) && (int) $params['height'] > 0 ? (int) $params['height'] : 200;
        $level = !empty($params['level']) && array_search($params['level'], array('L', 'M', 'Q', 'H')) !== false ? $params['level'] : 'M';

        $urlencoded = ('otpauth://totp/'.$name.'?secret='.$secret.'');
//        if (isset($title)) {
//            $urlencoded .= urlencode('&issuer='.urlencode($title));
//        }

        //return 'https://chart.googleapis.com/chart?chs='.$width.'x'.$height.'&chld='.$level.'|0&cht=qr&chl='.$urlencoded.'';
        return $urlencoded.'';
    }

    /**
     * Check if the code is correct. This will accept codes starting from $discrepancy*30sec ago to $discrepancy*30sec from now.
     *
     * @param string   $secret
     * @param string   $code
     * @param int      $discrepancy      This is the allowed time drift in 30 second units (8 means 4 minutes before or after)
     * @param int|null $currentTimeSlice time slice if we want use other that time()
     *
     * @return bool
     */
    public function verifyCode($secret, $code, $discrepancy = 1, $currentTimeSlice = null)
    {
        if ($currentTimeSlice === null) {
            $currentTimeSlice = floor(time() / 30);
        }

        if (strlen($code) != 6) {
            return false;
        }

        for ($i = -$discrepancy; $i <= $discrepancy; ++$i) {
            $calculatedCode = $this->getCode($secret, $currentTimeSlice + $i);
            if ($this->timingSafeEquals($calculatedCode, $code)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Set the code length, should be >=6.
     *
     * @param int $length
     *
     * @return PHPGangsta_GoogleAuthenticator
     */
    public function setCodeLength($length)
    {
        $this->_codeLength = $length;

        return $this;
    }

    /**
     * Helper class to decode base32.
     *
     * @param $secret
     *
     * @return bool|string
     */
    protected function _base32Decode($secret)
    {
        if (empty($secret)) {
            return '';
        }

        $base32chars = $this->_getBase32LookupTable();
        $base32charsFlipped = array_flip($base32chars);

        $paddingCharCount = substr_count($secret, $base32chars[32]);
        $allowedValues = array(6, 4, 3, 1, 0);
        if (!in_array($paddingCharCount, $allowedValues)) {
            return false;
        }
        for ($i = 0; $i < 4; ++$i) {
            if ($paddingCharCount == $allowedValues[$i] &&
                substr($secret, -($allowedValues[$i])) != str_repeat($base32chars[32], $allowedValues[$i])) {
                return false;
            }
        }
        $secret = str_replace('=', '', $secret);
        $secret = str_split($secret);
        $binaryString = '';
        for ($i = 0; $i < count($secret); $i = $i + 8) {
            $x = '';
            if (!in_array($secret[$i], $base32chars)) {
                return false;
            }
            for ($j = 0; $j < 8; ++$j) {
                $x .= str_pad(base_convert(@$base32charsFlipped[@$secret[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
            }
            $eightBits = str_split($x, 8);
            for ($z = 0; $z < count($eightBits); ++$z) {
                $binaryString .= (($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48) ? $y : '';
            }
        }

        return $binaryString;
    }

    /**
     * Get array with all 32 characters for decoding from/encoding to base32.
     *
     * @return array
     */
    protected function _getBase32LookupTable()
    {
        return array(
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', //  7
            'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
            'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
            '=',  // padding char
        );
    }

    /**
     * A timing safe equals comparison
     * more info here: http://blog.ircmaxell.com/2014/11/its-all-about-time.html.
     *
     * @param string $safeString The internal (safe) value to be checked
     * @param string $userString The user submitted (unsafe) value
     *
     * @return bool True if the two strings are identical
     */
    private function timingSafeEquals($safeString, $userString)
    {
        if (function_exists('hash_equals')) {
            return hash_equals($safeString, $userString);
        }
        $safeLen = strlen($safeString);
        $userLen = strlen($userString);

        if ($userLen != $safeLen) {
            return false;
        }

        $result = 0;

        for ($i = 0; $i < $userLen; ++$i) {
            $result |= (ord($safeString[$i]) ^ ord($userString[$i]));
        }

        // They are only identical strings if $result is exactly 0...
        return $result === 0;
    }
}

//程序调用部分
$ga = new PHPGangsta_GoogleAuthenticator();

//创建一个新的"安全密匙SecretKey"
//把本次的"安全密匙SecretKey" 入库,和账户关系绑定,客户端也是绑定这同一个"安全密匙SecretKey"
//$secret = $ga->createSecret();
$secret = 'IH2AGN774DGNNA2N';
echo "安全密匙SecretKey: ".$secret."\n\n";

$qrCodeUrl = $ga->getQRCodeGoogleUrl('52min.net', $secret); //第一个参数是"标识",第二个参数为"安全密匙SecretKey" 生成二维码信息
echo "Google Charts URL for the QR-Code: ".$qrCodeUrl."\n\n"; //Google Charts接口 生成的二维码图片,方便手机端扫描绑定安全密匙SecretKey

$oneCode = $ga->getCode($secret); //服务端计算"一次性验证码"
echo "服务端计算的验证码是:".$oneCode."\n\n";

//把提交的验证码和服务端上生成的验证码做对比
// $secret 服务端的 "安全密匙SecretKey"
// $oneCode 手机上看到的 "一次性验证码"
// 最后一个参数 为容差时间,这里是2 那么就是 2* 30 sec 一分钟.
// 这里改成自己的业务逻辑

$checkResult = $ga->verifyCode($secret, $code, 1);
if ($checkResult) {
    echo '匹配! OK';
} else {
    echo '不匹配! FAILED';
}