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 <>. * * PHP Google two-factor authentication module. * * See * 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：