<?php

// Do not allow the file to be called directly.
if (!defined('ABSPATH')) {
	exit;
}

require_once(dirname(__FILE__) . '/base32.php');

class TokenAuth6238
{
	/**
	 * Verify the code & token.
	 * 
	 * @param string $secretkey Secret clue (base 32).
	 * @return bool True if success, false if failure
	 */	
	public static function verify($secretkey, $code, $rangein30s = 3)
	{
		$key = base32static::decode($secretkey);
		$unixtimestamp = time() / 30;
		
		for ($i = -($rangein30s); $i <= $rangein30s; $i++) {
			$checktime = (int)($unixtimestamp + $i);
			$thiskey = self::oath_hotp($key, $checktime);
			
			if ((int) $code == self::oath_truncate($thiskey, 6)) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Generate the random clue/key.
	 * 
	 * @param integer $length
	 * @return string
	 */
	public static function generateRandomClue($length = 16)
	{
		$b32 = '234567QWERTYUIOPASDFGHJKLZXCVBNM';
		$s = '';
		for ($i = 0; $i < $length; $i++) {
			$s .= $b32[rand(0,31)];
		}
		
		return $s;
	}

	/**
	 * 
	 * @param string $key
	 * @param integer $counter
	 * @return string
	 */
	private static function oath_hotp($key, $counter)
	{
		$result = '';  
		$orgcounter = $counter;         
		$cur_counter = array(0,0,0,0,0,0,0,0);
					
		for ($i = 7; $i >= 0; $i--) { // C for unsigned char, * for  repeating to the end of the input data 
			$cur_counter[$i] = pack('C*', $counter);    
			$counter = $counter >> 8;
		}

		$binary = implode($cur_counter);

		// Pad to 8 characters
		str_pad($binary, 8, chr(0), STR_PAD_LEFT);
		return hash_hmac('sha1', $binary, $key);
	}

	/**
	 * Truncate
	 * 
	 * @param string $hash
	 * @param integer $length
	 * @return boolean
	 */
	private static function oath_truncate($hash, $length = 6)
	{
		$result = ''; 
		$hashcharacters = str_split($hash, 2);

		for ($j = 0; $j < count($hashcharacters); $j++) {
			$hmac_result[] = hexdec($hashcharacters[$j]);
		}

		$offset = $hmac_result[19] & 0xf;     
		return (
				(($hmac_result[$offset + 0] & 0x7f) << 24) |
				(($hmac_result[$offset + 1] & 0xff) << 16) |
				(($hmac_result[$offset + 2] & 0xff) << 8) |
				($hmac_result[$offset + 3] & 0xff)
		) % pow(10, $length);
	}
	
}