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<?php
/**
* Matomo - free/libre analytics platform
*
* @link https://matomo.org
* @license https://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
*/
namespace Piwik\Tracker;
use Piwik\Common;
use Piwik\Date;
use Piwik\Option;
class FingerprintSalt
{
public const OPTION_PREFIX = 'fingerprint_salt_';
public const DELETE_FINGERPRINT_OLDER_THAN_SECONDS = 432000; // 5 days in seconds
public function generateSalt()
{
return Common::getRandomString(32);
}
public function deleteOldSalts()
{
// we want to make sure to delete salts that were created more than three days ago as they are likely not in
// use anymore. We should delete them to ensure the fingerprint is truly random for each day because if we used
// eg the regular salt then it would technically still be possible to try and regenerate the fingerprint based
// on certain information.
// Typically, only the salts for today and yesterday are used. However, if someone was to import historical data
// for the same day and this takes more than five days, then it could technically happen that we delete a
// fingerprint that is still in use now and as such after deletion a few visitors would have a new configId
// within one visit and such a new visit would be created. That should be very much edge case though.
$deleteSaltsCreatedBefore = Date::getNowTimestamp() - self::DELETE_FINGERPRINT_OLDER_THAN_SECONDS;
$options = Option::getLike(self::OPTION_PREFIX . '%');
$deleted = array();
foreach ($options as $name => $value) {
$value = $this->decode($value);
if (empty($value['time']) || $value['time'] < $deleteSaltsCreatedBefore) {
Option::delete($name);
$deleted[] = $name;
}
}
return $deleted;
}
public function getDateString(Date $date, $timezone)
{
$dateString = Date::factory($date->getTimestampUTC(), $timezone)->toString();
return $dateString;
}
private function encode($value)
{
return json_encode($value);
}
private function decode($value)
{
return @json_decode($value, true);
}
public function getSalt($dateString, $idSite)
{
$fingerprintSaltKey = self::OPTION_PREFIX . (int) $idSite . '_' . $dateString;
$salt = Option::get($fingerprintSaltKey);
if (!empty($salt)) {
$salt = $this->decode($salt);
}
if (empty($salt['value'])) {
$salt = array(
'value' => $this->generateSalt(),
'time' => Date::getNowTimestamp(),
);
Option::set($fingerprintSaltKey, $this->encode($salt));
}
return $salt['value'];
}
}
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