/**
* Renders the captcha image
*
* @return string empty string (the image is sent here)
*/
public function render()
{
// Avoid Brute Force Attacks:
if (!$this->word->getAttempts()) {
$this->word->setAttempts(1);
} else {
$this->word->setAttempts($this->word->getAttempts() + 1);
// if more than ($this->settings['maxAttempts']) refreshes, block further refreshes
// can be negated by connecting with new session id
// could get round this by storing num attempts in database against IP
// could get round that by connecting with different IP (eg, using proxy servers)
// in short, there's little point trying to avoid brute forcing
// the best way to protect against BF attacks is to ensure the dictionary is not
// accessible via the web or use random string option
if ($this->word->getAttempts() > $this->settings['maxAttempts']) {
$this->word->setWordHash('');
$this->word->setWordCypher(array());
$this->word->setHashFunction('');
// Get an instance of the word repository
$objectManager = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\\CMS\\Extbase\\Object\\ObjectManager');
$wordRepository = $objectManager->get('SJBR\\SrFreecap\\Domain\\Repository\\WordRepository');
// Reset the word
$wordRepository->setWord($this->word);
$string = \TYPO3\CMS\Extbase\Utility\LocalizationUtility::translate('max_attempts', $this->extensionName);
$font = 5;
$width = imagefontwidth($font) * strlen($string);
$height = imagefontheight($font);
$image = ImageCreate($width + 2, $height + 20);
$background = ImageColorAllocate($image, 255, 255, 255);
ImageColorTransparent($image, $background);
$red = ImageColorAllocate($image, 255, 0, 0);
ImageString($image, $font, 1, 10, $string, $red);
\SJBR\SrFreecap\Utility\ImageContentUtility::sendImage($image, $this->settings['imageFormat']);
ImageDestroy($image);
// Return an empty string
return '';
}
}
// Get random word
$word = \SJBR\SrFreecap\Utility\RandomContentUtility::getRandomWord($this->settings['useWordsList'], $this->settings['wordsListLocation'], $this->settings['generateNumbers'], $this->settings['maxWordLength']);
// Save hash of word for comparison
// using hash so that if there's an insecurity elsewhere (eg on the form processor),
// an attacker could only get the hash
// also, shared servers usually give all users access to the session files
// echo `ls /tmp`; and echo `more /tmp/someone_elses_session_file`; usually work
// so even if your site is 100% secure, someone else's site on your server might not be
// hence, even if attackers can read the session file, they can't get the freeCap word
// (though most hashes are easy to brute force for simple strings)
$this->word->setWordHash(md5($word));
// We use a simple encrypt to prevent the session from being exposed
if ($this->settings['accessibleOutput']) {
$this->word->setWordCypher(\SJBR\SrFreecap\Utility\EncryptionUtility::encrypt($word));
}
// Build the image
$image = $this->buildImage($word, $this->settings['imageWidth'], $this->settings['imageHeight'], $this->settings['backgroundType']);
// Send the image
\SJBR\SrFreecap\Utility\ImageContentUtility::sendImage($image, $this->settings['imageFormat']);
// Cleanup
ImageDestroy($image);
// Return an empty string
return '';
}
/**
* Gets the word that was stored in session data
* @return string the retrieved and decoded word
*/
protected function getWord()
{
// Get cypher from session data
$cypher = $this->word->getWordCypher();
// Decrypt the word
$decryptedString = EncryptionUtility::decrypt($cypher);
return implode('-', preg_split('//', $decryptedString, -1, PREG_SPLIT_NO_EMPTY));
}
