Google TOTP Two-factor Authentication for PHP

google2fa.php

<?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;
	}

	/**
	* 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);
	}



}
/**
 * for qr code:   otpauth://totp/screenconnect?secret=PEHMPSDNLXIOG65U
 * for scan qr code in mobile use FreeOTP or Google Authenticator
 * vhdm.ir
 */
$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<br>");
echo("Timestamp: $TimeStamp<br>");
echo("One time password: $otp<br>");

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

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

var_dump($result);
?>

Ok thats good!  Thank you very very much!!! Sent from Yahoo Mail for iPhone On Monday, February 15, 2021, 8:06 AM, Vahid <notifications@github.com> wrote: @vhdm commented on this gist. Hi, congratulations for this great work, I want to know if this code can be used by another developer? hi, you're welcome, yes of course — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or unsubscribe.