php集成动态口令认证

大多数系统目前均使用的静态密码进行身份认证登录，但由于静态密码容易被窃取，其安全性无法满足安全要求。

动态口令采用一次一密、用过密码作废的方式防止了密码被窃取带来的安全问题。
动态口令分为HOTP（基于事件计数的动态口令，RFC4226）、TOTP（基于时间计数的动态口令,RFC6238）、OCRA（挑战应答式动态口令,RFC6287）等方式。

本文介绍了集成TOTP方式的动态口令认证的方案，PHP框架采用Thinkphp3.2.3，动态口令生成器使用的是google authtication。

1、为Thinkphp框架添加oath算法类

oath算法封装类oath.php代码如下：

<?PHP
/**
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * PHP Google two-factor authentication module.
 *
 * See http://www.idontplaydarts.com/2011/07/google-totp-two-factor-authentication-for-php/
 * for more details
 *
 * @author Phil
 **/

class Google2FA {

 const keyRegeneration  = 30; // Interval between key regeneration
 const otpLength  = 6; // Length of the Token generated

 private static $lut = array( // Lookup needed for Base32 encoding
  "A" => 0, "B" => 1,
  "C" => 2, "D" => 3,
  "E" => 4, "F" => 5,
  "G" => 6, "H" => 7,
  "I" => 8, "J" => 9,
  "K" => 10, "L" => 11,
  "M" => 12, "N" => 13,
  "O" => 14, "P" => 15,
  "Q" => 16, "R" => 17,
  "S" => 18, "T" => 19,
  "U" => 20, "V" => 21,
  "W" => 22, "X" => 23,
  "Y" => 24, "Z" => 25,
  "2" => 26, "3" => 27,
  "4" => 28, "5" => 29,
  "6" => 30, "7" => 31
 );

 /**
  * Generates a 16 digit secret key in base32 format
  * @return string
  **/
 public static function generate_secret_key($length = 16) {
  $b32  = "234567QWERTYUIOPASDFGHJKLZXCVBNM";
  $s  = "";

  for ($i = 0; $i < $length; $i++)
   $s .= $b32[rand(0,31)];

  return $s;
 }

 /**
  * Returns the current Unix Timestamp devided by the keyRegeneration
  * period.
  * @return integer
  **/
 public static function get_timestamp() {
  return floor(microtime(true)/self::keyRegeneration);
 }

 /**
  * Decodes a base32 string into a binary string.
  **/
 public static function base32_decode($b32) {

  $b32  = strtoupper($b32);

  if (!preg_match('/^[ABCDEFGHIJKLMNOPQRSTUVWXYZ234567]+$/', $b32, $match))
   throw new Exception('Invalid characters in the base32 string.');

  $l  = strlen($b32);
  $n = 0;
  $j = 0;
  $binary = "";

  for ($i = 0; $i < $l; $i++) {

   $n = $n << 5;     // Move buffer left by 5 to make room
   $n = $n + self::$lut[$b32[$i]];  // Add value into buffer
   $j = $j + 5;    // Keep track of number of bits in buffer

   if ($j >= 8) {
    $j = $j - 8;
    $binary .= chr(($n & (0xFF << $j)) >> $j);
   }
  }

  return $binary;
 }
 /*by tang*/
 public static function base32_encode($data, $length){
  $basestr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
  $count = 0;
  if ($length > 0) {
   $buffer = $data[0];
   $next = 1;
   $bitsLeft = 8;

   while (($bitsLeft > 0 || $next < $length)) {
    if ($bitsLeft < 5) {
    if ($next < $length) {
     $buffer <<= 8;
     $buffer |= $data[$next++] & 0xFF;
     $bitsLeft += 8;
    } else {
     $pad = 5 - $bitsLeft;
     $buffer <<= $pad;
     $bitsLeft += $pad;
    }
    }
    $index = 0x1F & ($buffer >> ($bitsLeft - 5));
    $bitsLeft -= 5;
    $result .= $basestr[$index];
    $count++;
   }
   }
   return $result;
 }
 /**
  * Takes the secret key and the timestamp and returns the one time
  * password.
  *
  * @param binary $key - Secret key in binary form.
  * @param integer $counter - Timestamp as returned by get_timestamp.
  * @return string
  **/
 public static function oath_hotp($key, $counter)
 {
  if (strlen($key) < 8)
  throw new Exception('Secret key is too short. Must be at least 16 base 32 characters');

  $bin_counter = pack('N*', 0) . pack('N*', $counter);  // Counter must be 64-bit int
  $hash  = hash_hmac ('sha1', $bin_counter, $key, true);

  return str_pad(self::oath_truncate($hash), self::otpLength, '0', STR_PAD_LEFT);
 }

 /**
  * Verifys a user inputted key against the current timestamp. Checks $window
  * keys either side of the timestamp.
  *
  * @param string $b32seed
  * @param string $key - User specified key
  * @param integer $window
  * @param boolean $useTimeStamp
  * @return boolean
  **/
 public static function verify_key($b32seed, $key, $window = 5, $useTimeStamp = true) {

  $timeStamp = self::get_timestamp();

  if ($useTimeStamp !== true) $timeStamp = (int)$useTimeStamp;

  $binarySeed = self::base32_decode($b32seed);

  for ($ts = $timeStamp - $window; $ts <= $timeStamp + $window; $ts++)
   if (self::oath_hotp($binarySeed, $ts) == $key)
    return true;

  return false;

 }

 /**
  * Extracts the OTP from the SHA1 hash.
  * @param binary $hash
  * @return integer
  **/
 public static function oath_truncate($hash)
 {
  $offset = ord($hash[19]) & 0xf;

  return (
   ((ord($hash[$offset+0]) & 0x7f) << 24 ) |
   ((ord($hash[$offset+1]) & 0xff) << 16 ) |
   ((ord($hash[$offset+2]) & 0xff) << 8 ) |
   (ord($hash[$offset+3]) & 0xff)
  ) % pow(10, self::otpLength);
 }

}
/*
$InitalizationKey = "LFLFMU2SGVCUIUCZKBMEKRKLIQ";     // Set the inital key

$TimeStamp  = Google2FA::get_timestamp();
$secretkey  = Google2FA::base32_decode($InitalizationKey); // Decode it into binary
$otp    = Google2FA::oath_hotp($secretkey, $TimeStamp); // Get current token

echo("Init key: $InitalizationKey\n");
echo("Timestamp: $TimeStamp\n");
echo("One time password: $otp\n");

// Use this to verify a key as it allows for some time drift.

$result = Google2FA::verify_key($InitalizationKey, "123456");

var_dump($result);
*/
?>

由于google的动态口令算法中种子密钥使用了base32编码，因此需要base32算法，base32.php内容如下：

<?php
//namespace Base32;
/**
 * Base32 encoder and decoder
 *
 * Last update: 2012-06-20
 *
 * RFC 4648 compliant
 * @link http://www.ietf.org/rfc/rfc4648.txt
 *
 * Some groundwork based on this class
 * https://github.com/NTICompass/PHP-Base32
 *
 * @author Christian Riesen <chris.riesen@gmail.com>
 * @link http://christianriesen.com
 * @license MIT License see LICENSE file
 */
class Base32
{
 /**
  * Alphabet for encoding and decoding base32
  *
  * @var array
  */
 private static $alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=';
 /**
  * Creates an array from a binary string into a given chunk size
  *
  * @param string $binaryString String to chunk
  * @param integer $bits Number of bits per chunk
  * @return array
  */
 private static function chunk($binaryString, $bits)
 {
  $binaryString = chunk_split($binaryString, $bits, ' ');
  if (substr($binaryString, (strlen($binaryString)) - 1) == ' ') {
   $binaryString = substr($binaryString, 0, strlen($binaryString)-1);
  }
  return explode(' ', $binaryString);
 }
 /**
  * Encodes into base32
  *
  * @param string $string Clear text string
  * @return string Base32 encoded string
  */
 public static function encode($string)
 {
  if (strlen($string) == 0) {
   // Gives an empty string
   return '';
  }
  // Convert string to binary
  $binaryString = '';
  foreach (str_split($string) as $s) {
   // Return each character as an 8-bit binary string
   $binaryString .= sprintf('%08b', ord($s));
  }
  // Break into 5-bit chunks, then break that into an array
  $binaryArray = self::chunk($binaryString, 5);
  // Pad array to be divisible by 8
  while (count($binaryArray) % 8 !== 0) {
   $binaryArray[] = null;
  }
  $base32String = '';
  // Encode in base32
  foreach ($binaryArray as $bin) {
   $char = 32;
   if (!is_null($bin)) {
    // Pad the binary strings
    $bin = str_pad($bin, 5, 0, STR_PAD_RIGHT);
    $char = bindec($bin);
   }
   // Base32 character
   $base32String .= self::$alphabet[$char];
  }
  return $base32String;
 }
 /**
  * Decodes base32
  *
  * @param string $base32String Base32 encoded string
  * @return string Clear text string
  */
 public static function decode($base32String)
 {
  // Only work in upper cases
  $base32String = strtoupper($base32String);
  // Remove anything that is not base32 alphabet
  $pattern = '/[^A-Z2-7]/';
  $base32String = preg_replace($pattern, '', $base32String);
  if (strlen($base32String) == 0) {
   // Gives an empty string
   return '';
  }
  $base32Array = str_split($base32String);
  $string = '';
  foreach ($base32Array as $str) {
   $char = strpos(self::$alphabet, $str);
   // Ignore the padding character
   if ($char !== 32) {
    $string .= sprintf('%05b', $char);
   }
  }
  while (strlen($string) %8 !== 0) {
   $string = substr($string, 0, strlen($string)-1);
  }
  $binaryArray = self::chunk($string, 8);
  $realString = '';
  foreach ($binaryArray as $bin) {
   // Pad each value to 8 bits
   $bin = str_pad($bin, 8, 0, STR_PAD_RIGHT);
   // Convert binary strings to ASCII
   $realString .= chr(bindec($bin));
  }
  return $realString;
 }
}

?>

将这两个文件放到Thinkphp框架的ThinkPHP\Library\Vendor\oath目录下，oath目录是自己创建的。

2、添加数据库字段

用户表添加如下字段:
auth_type（0-静态密码，1-动态口令）
seed（种子密钥）
temp_seed（临时种子密钥）
last_logintime（上次登录成功时间）
last_otp（上次使用密码）
其中auth_type是为了标明用户使用的哪种认证方式，seed为用户的种子密钥，temp_seed为用户未开通前临时保存的一个种子密钥，如果用户开通动态口令认证成功，该字段内容会填到seed字段。last_logintime和last_otp为上次认证成功的时间和动态口令，用于避免用户同一个口令重复使用。

3、代码集成

1）、开通动态口令

在原有系统的修改密码页面，加上认证方式的选择，例如：

如果用户选择动态口令方式，则会生成一张二维码显示在页面，用于用户开通动态口令。为了兼容google authtication，其二维码格式与谷歌一样。生成二维码的方法见我的另一篇《Thinkphp3.2.3整合phpqrcode生成带logo的二维码》 。
生成密钥二维码代码如下：

public function qrcode()
 {
  Vendor('oath.base32');
  $base32 = new \Base32();
  $rand = random(16);//生成随机种子
  $rand = $base32->encode($rand);
  $rand=str_replace('=','',$rand);//去除填充的‘='

  $errorCorrectionLevel =intval(3) ;//容错级别
  $matrixPointSize = intval(8);//生成图片大小

  //生成二维码图片
  Vendor('phpqrcode.phpqrcode');
  $object = new \QRcode();
  $text = sprintf("otpauth://totp/%s?secret=%s", $user, $rand);
  $object->png($text, false, $errorCorrectionLevel, $matrixPointSize, 2);

  生成的种子$rand保存到数据库的temp_seed字段
 }

random是生成随机字符串函数。$rand=str_replace('=','',$rand)这句代码是因为谷歌手机令牌中base32解码算法并没有填充的‘='号。

验证用户动态口令的代码如下：

从数据库读取temp_seed
Vendor('oath.oath');
$object = new \Google2FA();
if($object->verify_key($temp_seed, $otp)){
 验证成功，将数据库更新seed为temp_seed，auth_type为1，last_otp为otp
}

2）、动态口令登录

用户动态口令登录验证的代码：

从数据库读取auth_type,seed,last_otp字段。

if($auth_type==1){//动态口令
 //防止重复认证
 if($lat_otp == $otp) {
  动态口令重复使用返回
 }
 Vendor('oath.oath');
 $object = new \Google2FA();
 if(!$object->verify_key($seed, $otp))
 {
  动态口令不正确
 }
 else
 {
  登录成功，将数据库更新last_otp为$otp,last_logintime为time()
 }
}

4、测试验证

下载google authtication，使用静态密码登录系统，进入修改密码页面。
打开google authtication，扫描二维码，会显示动态口令。

保存内容，开通动态口令成功！
然后你就可以用高大上的动态口令登录系统了!

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