使用google 两步验证的一个库

<?
/**
* 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;
}

/**
* 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 = 4, $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 = "PEHMPSDNLXIOG65U";                 // 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);