Hashcash.php

<?php
/*
    MIT License

    Copyright (C) 2014 Christian Mayer <https://fox21.at>

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all
    copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
    SOFTWARE.
 */
class Hashcash {

    const DATE_FORMATYMD = 'ymd';
    const DATE_FORMAT10 = 'ymdHi';
    const DATE_FORMAT12 = 'ymdHis';
    const MINT_EXPIRATION = '604800';
    const MINT_ATTEMPTS_MAX = '10';

    private $version = 1;
    private $bits;
    private $date;
    private $resource;
    private $extension = '';
    private $salt = '';
    private $suffix = '';
    private $expiration = 0;
    private $attempts = 0;
    private $hash = '';
    private $mintAttemptsMax;
    private $stamp = '';

    /**
     * Creating a new instance of Hashcash class.
     * @param type $bits
     * @param type $resource
     */
    public function __construct($bits = 20, $resource = '') {
        $this->setBits($bits);
        $this->setDate(date(self::DATE_FORMATYMD));
        $this->setResource($resource);
        $this->setExpiration(self::MINT_EXPIRATION);
        $this->setMintAttemptsMax(self::MINT_ATTEMPTS_MAX);
    }

    public function setVersion($version) {
        if ($version <= 0) {
            throw new RuntimeException('Version 0 not implemented yet.', 1);
        } elseif ($version > 1) {
            throw new RuntimeException(
                'Version ' . $version . ' not implemented yet.', 2);
        }

        $this->version = (int)$version;
    }

    public function getVersion(){
        return (int)$this->version;
    }

    public function setBits($bits){
        $this->bits = (int)$bits;
    }

    public function getBits(){
        return (int)$this->bits;
    }

    public function setDate($date){
        $dateLen = strlen($date);
        if($dateLen != 6 && $dateLen != 10 && $dateLen != 12){
            throw new InvalidArgumentException(
                'Date "' . $date . '" is not valid.', 1);
        }

        $this->date = $date;
    }

    public function getDate(){
        return $this->date;
    }

    public function setResource($resource){
        $this->resource = $resource;
    }

    public function getResource(){
        return $this->resource;
    }

    public function setExtension($extension){
        $this->extension = $extension;
    }

    public function getExtension(){
        return $this->extension;
    }

    public function setSalt($salt){
        $this->salt = $salt;
    }

    public function getSalt(){
        return $this->salt;
    }

    public function setSuffix($suffix){
        $this->suffix = $suffix;
    }

    public function getSuffix(){
        return $this->suffix;
    }

    public function setExpiration($expiration){
        $this->expiration = $expiration;
    }

    public function getExpiration(){
        return $this->expiration;
    }

    public function setAttempts($attempts){
        $this->attempts = $attempts;
    }

    public function getAttempts(){
        return $this->attempts;
    }

    public function setHash($hash){
        $this->hash = $hash;
    }

    public function getHash(){
        return $this->hash;
    }

    public function setMintAttemptsMax($mintAttemptsMax){
        $this->mintAttemptsMax = (int)$mintAttemptsMax;
    }

    public function getMintAttemptsMax(){
        return (int)$this->mintAttemptsMax;
    }

    public function setStamp($stamp){
        $this->stamp = $stamp;
    }

    public function getStamp(){
        if(!$this->stamp) {
            $stamp = $this->getVersion() . ':'.$this->getBits();
            $stamp .= ':' . $this->getDate();
            $stamp .= ':' . $this->getResource().':' . $this->getExtension();
            $stamp .= ':' . $this->getSalt() . ':' . $this->getSuffix();
            $this->stamp = $stamp;
        }

        return $this->stamp;
    }

    public function mint() {
        $stamp = '';
        $rounds = pow(2, $this->getBits());
        $bytes = $this->getBits() / 8 + (8 - ($this->getBits() % 8)) / 8;
        $salt = $this->getSalt();
        if (!$salt) {
            $salt = Application::SecureRandomString(24, 'base64');
        }

        $baseStamp = $this->getVersion().':'.$this->getBits();
        $baseStamp .= ':'.$this->getDate();
        $baseStamp .= ':' . $this->getResource() . ':' . $this->getExtension() . ':';
        $found = FALSE;
        $round = 0;
        $testStamp = '';
        $bits = 0;
        $attemptSalts = array();
        for ($attempt = 0; ($attempt < $this->getMintAttemptsMax() || !$this->getMintAttemptsMax()) && !$found; ++$attempt) {
            $attemptSalts[] = $salt;
            $attemptStamp = $baseStamp . $salt . ':';
            for ($round = 0; $round < $rounds; ++$round) {
                $testStamp = $attemptStamp . $round;
                $found = $this->checkBitsFast(substr(hash('sha1', $testStamp, TRUE), 0, $bytes), $bytes, $this->getBits());
                if ($found) {
                    break;
                }
            }

            if (!$found) {
                $saltBase64Padded = base64_encode(openssl_random_pseudo_bytes(24, true));
                $salt =  substr($saltBase64Padded, 0, strpos($saltBase64Padded, '='));
            }
        }

        if ($found) {
            $stamp = $testStamp;
            $this->setSuffix($round);
            $this->setSalt($salt);
            $this->setAttempts($attempt);
            $this->setHash(hash('sha1', $stamp));
        } else{
            $msg = 'Could not generate stamp after '.$attempt.' attempts, ';
            $msg .= 'each with ' . $rounds . ' rounds. ';
            $msg .= 'bits=' . $this->getBits() . ', ';
            $msg .= 'date=' . $this->getDate() . ', ';
            $msg .= 'resource='.$this->getResource().', ';
            $msg .= 'salts='.join(',', $attemptSalts);
            throw new RuntimeException($msg);
        }

        $this->setStamp($stamp);
        return $stamp;
    }

    public function mintAll(){
        $stamps = array();
        $rounds = pow(2, $this->getBits());
        $bytes = $this->getBits() / 8 + (8 - ($this->getBits() % 8)) / 8;
        $salt = $this->getSalt();
        $baseStamp = $this->getVersion().':'.$this->getBits();
        $baseStamp .= ':'.$this->getDate();
        $baseStamp .= ':'.$this->getResource().':'.$this->getExtension().':'.$salt.':';
        if (!$salt) {
            $salt = Application::SecureRandomString(24, 'base64');
        }

        for($round = 0; $round < $rounds; ++$round){
            $testStamp = $baseStamp.$round;
            $found = $this->checkBitsFast(substr(hash('sha1', $testStamp, TRUE), 0, $bytes), $bytes, $this->getBits());
            if ($found){
                $stamps[] = $testStamp;
            }
        }

        return $stamps;
    }

    public function parseStamp($stamp) {
        if (!$stamp) {
            throw new InvalidArgumentException('Stamp "'.$stamp.'" is not valid.', 1);
        }

        $items = preg_split('/:/', $stamp);
        if (count($items) < 7) {
            throw new InvalidArgumentException('Stamp "'.$stamp.'" is not valid.', 2);
        }

        $this->setVersion($items[0]);
        $this->setBits($items[1]);
        $this->setDate($items[2]);
        $this->setResource($items[3]);
        $this->setExtension($items[4]);
        $this->setSalt($items[5]);
        $this->setSuffix($items[6]);
    }

    public function verify($stamp = null) {
        if($stamp === null){
            $stamp = $this->getStamp();
        } else {
            $this->parseStamp($stamp);
        }

        $verified = false;
        $bytes = $this->getBits() / 8 + (8 - ($this->getBits() % 8)) / 8;
        $verified = $this->checkBitsFast(substr(hash('sha1', $stamp, true), 0, $bytes), $bytes, $this->getBits());
        if ($verified && $this->getExpiration()) {
            $dateLen = strlen($this->getDate());
            $year = '';
            $month = '';
            $day = '';
            $hour = '00';
            $minute = '00';
            $second = '00';
            switch ($dateLen) {
                case 12:
                    $second = substr($this->getDate(), 10, 2);
                    break;
                case 10:
                    $hour = substr($this->getDate(), 6, 2);
                    $minute = substr($this->getDate(), 8, 2);
                    break;
                case 6:
                    $year = substr($this->getDate(), 0, 2);
                    $month = substr($this->getDate(), 2, 2);
                    $day = substr($this->getDate(), 4, 2);
                    break;
            }

            $date = new DateTime($year.'-'.$month.'-'.$day.' '.$hour.':'.$minute.':'.$second);
            $now = new DateTime('now');
            if ($date->getTimestamp() < $now->getTimestamp() - $this->getExpiration()) {
                $verified = false;
            }
        }

        return $verified;
    }

    /**
     * @codeCoverageIgnore
     */
    private function checkBitsSlow($data) {
        $bits = 0;
        $dataLen = strlen($data);
        for ($charn = 0; $charn < $dataLen; $charn++) {
            $char = ord($data[$charn]);
            if ($char) {
                for($bit = 7; $bit >= 0; $bit--) {
                    if ($char & (1 << $bit)) {
                        break;
                    }

                    $bits++;
                }

                break;
            } else{
                $bits += 8;
            }
        }

        return $bits;
    }

    private function checkBitsFast($data, $bytes, $bits) {
        $last = $bytes - 1;
        if (substr($data, 0, $last) == str_repeat("\x00", $last) && ord(substr($data, -1)) >> ($bytes * 8 - $bits) == 0) {
            return TRUE;
        }

        return FALSE;
    }
}