<?php

namespace {
    /**
     * PHP Class for handling Google Authenticator 2-factor authentication
     *
     * @author Michael Kliewe
     * @copyright 2012 Michael Kliewe
     * @license http://www.opensource.org/licenses/bsd-license.php BSD License
     * @link http://www.phpgangsta.de/
     *
     * small adjustments by matomo.org
     * - renamed class
     * - removed method getQRCodeGoogleUrl
     * - use better random secret generator
     * - apply proper type hints
     */
    class TwoFactorAuthenticator
    {
        protected $_codeLength = 6;
        /**
         * Create new secret.
         * 16 characters, randomly chosen from the allowed base32 characters.
         *
         * @param int $secretLength
         * @return string
         */
        public function createSecret(int $secretLength = 16) : string
        {
            $validChars = $this->_getBase32LookupTable();
            unset($validChars[32]);
            // modified by matomo.org
            return \Piwik\Common::getRandomString($secretLength, \implode('', $validChars));
        }
        /**
         * Calculate the code, with given secret and point in time
         *
         * @param string $secret
         * @param int|null $timeSlice
         * @return string
         */
        public function getCode(string $secret, ?int $timeSlice = null)
        {
            if ($timeSlice === null) {
                $timeSlice = \floor(\time() / 30);
            }
            $secretkey = $this->_base32Decode($secret);
            // Pack time into binary string
            $time = \chr(0) . \chr(0) . \chr(0) . \chr(0) . \pack('N*', $timeSlice);
            // Hash it with users secret key
            $hm = \hash_hmac('SHA1', $time, $secretkey, \true);
            // Use last nipple of result as index/offset
            $offset = \ord(\substr($hm, -1)) & 0xf;
            // grab 4 bytes of the result
            $hashpart = \substr($hm, $offset, 4);
            // Unpak binary value
            $value = \unpack('N', $hashpart);
            $value = $value[1];
            // Only 32 bits
            $value = $value & 0x7fffffff;
            $modulo = \pow(10, $this->_codeLength);
            return \str_pad($value % $modulo, $this->_codeLength, '0', \STR_PAD_LEFT);
        }
        /**
         * Check if the code is correct. This will accept codes starting from $discrepancy*30sec ago to $discrepancy*30sec from now
         *
         * @param string $secret
         * @param string $code
         * @param int $discrepancy This is the allowed time drift in 30 second units (8 means 4 minutes before or after)
         * @param int|null $currentTimeSlice time slice if we want use other that time()
         * @return bool
         */
        public function verifyCode(string $secret, string $code, int $discrepancy = 1, ?int $currentTimeSlice = null) : bool
        {
            if ($currentTimeSlice === null) {
                $currentTimeSlice = \floor(\time() / 30);
            }
            for ($i = -$discrepancy; $i <= $discrepancy; $i++) {
                $calculatedCode = $this->getCode($secret, $currentTimeSlice + $i);
                if ($this->timingSafeEquals($calculatedCode, $code)) {
                    return \true;
                }
            }
            return \false;
        }
        /**
         * Set the code length, should be >=6
         *
         * @param int $length
         * @return self
         */
        public function setCodeLength(int $length)
        {
            $this->_codeLength = $length;
            return $this;
        }
        /**
         * Helper class to decode base32
         *
         * @param string $secret
         * @return string
         */
        protected function _base32Decode(string $secret) : string
        {
            if (empty($secret)) {
                return '';
            }
            $base32chars = $this->_getBase32LookupTable();
            $base32charsFlipped = \array_flip($base32chars);
            $paddingCharCount = \substr_count($secret, $base32chars[32]);
            $allowedValues = array(6, 4, 3, 1, 0);
            if (!\in_array($paddingCharCount, $allowedValues)) {
                return \false;
            }
            for ($i = 0; $i < 4; $i++) {
                if ($paddingCharCount == $allowedValues[$i] && \substr($secret, -$allowedValues[$i]) != \str_repeat($base32chars[32], $allowedValues[$i])) {
                    return \false;
                }
            }
            $secret = \str_replace('=', '', $secret);
            $secret = \str_split($secret);
            $binaryString = "";
            for ($i = 0; $i < \count($secret); $i = $i + 8) {
                $x = "";
                if (!\in_array($secret[$i], $base32chars)) {
                    return \false;
                }
                for ($j = 0; $j < 8; $j++) {
                    $x .= \str_pad(\base_convert($base32charsFlipped[@$secret[$i + $j]] ?? '', 10, 2), 5, '0', \STR_PAD_LEFT);
                }
                $eightBits = \str_split($x, 8);
                for ($z = 0; $z < \count($eightBits); $z++) {
                    $binaryString .= ($y = \chr(\base_convert($eightBits[$z], 2, 10))) || \ord($y) == 48 ? $y : "";
                }
            }
            return $binaryString;
        }
        /**
         * Helper class to encode base32
         *
         * @param string $secret
         * @param bool $padding
         * @return string
         */
        protected function _base32Encode(string $secret, bool $padding = \true) : string
        {
            if (empty($secret)) {
                return '';
            }
            $base32chars = $this->_getBase32LookupTable();
            $secret = \str_split($secret);
            $binaryString = "";
            for ($i = 0; $i < \count($secret); $i++) {
                $binaryString .= \str_pad(\base_convert(\ord($secret[$i]), 10, 2), 8, '0', \STR_PAD_LEFT);
            }
            $fiveBitBinaryArray = \str_split($binaryString, 5);
            $base32 = "";
            $i = 0;
            while ($i < \count($fiveBitBinaryArray)) {
                $base32 .= $base32chars[\base_convert(\str_pad($fiveBitBinaryArray[$i], 5, '0'), 2, 10)];
                $i++;
            }
            if ($padding && ($x = \strlen($binaryString) % 40) != 0) {
                if ($x == 8) {
                    $base32 .= \str_repeat($base32chars[32], 6);
                } elseif ($x == 16) {
                    $base32 .= \str_repeat($base32chars[32], 4);
                } elseif ($x == 24) {
                    $base32 .= \str_repeat($base32chars[32], 3);
                } elseif ($x == 32) {
                    $base32 .= $base32chars[32];
                }
            }
            return $base32;
        }
        /**
         * Get array with all 32 characters for decoding from/encoding to base32
         *
         * @return array<string>
         */
        protected function _getBase32LookupTable() : array
        {
            return array(
                'A',
                'B',
                'C',
                'D',
                'E',
                'F',
                'G',
                'H',
                //  7
                'I',
                'J',
                'K',
                'L',
                'M',
                'N',
                'O',
                'P',
                // 15
                'Q',
                'R',
                'S',
                'T',
                'U',
                'V',
                'W',
                'X',
                // 23
                'Y',
                'Z',
                '2',
                '3',
                '4',
                '5',
                '6',
                '7',
                // 31
                '=',
            );
        }
        /**
         * A timing safe equals comparison
         * more info here: https://blog.ircmaxell.com/2014/11/its-all-about-time.html.
         *
         * @param string $safeString The internal (safe) value to be checked
         * @param string $userString The user submitted (unsafe) value
         *
         * @return bool True if the two strings are identical
         */
        private function timingSafeEquals(string $safeString, string $userString) : bool
        {
            if (\function_exists('hash_equals')) {
                return \hash_equals($safeString, $userString);
            }
            $safeLen = \strlen($safeString);
            $userLen = \strlen($userString);
            if ($userLen != $safeLen) {
                return \false;
            }
            $result = 0;
            for ($i = 0; $i < $userLen; ++$i) {
                $result |= \ord($safeString[$i]) ^ \ord($userString[$i]);
            }
            // They are only identical strings if $result is exactly 0...
            return $result === 0;
        }
    }
}