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<?php |
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namespace SilverStripe\VersionFeed\Filters; |
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use SilverStripe\Core\Config\Config; |
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use SilverStripe\Control\Controller; |
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use SilverStripe\Control\HTTPResponse_Exception; |
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/** |
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* Provides rate limiting of execution of a callback |
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*/ |
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class RateLimitFilter extends ContentFilter { |
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/** |
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* Time duration (in second) to allow for generation of cached results. Requests to |
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* pages that within this time period that do not hit the cache (and would otherwise trigger |
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* a version query) will be presented with a 429 (rate limit) HTTP error |
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* |
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* @config |
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* @var int |
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*/ |
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private static $lock_timeout = 5; |
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/** |
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* Determine if the cache generation should be locked on a per-page basis. If true, concurrent page versions |
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* may be generated without rate interference. |
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* |
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* @config |
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* @var bool |
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*/ |
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private static $lock_bypage = false; |
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/** |
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* Determine if rate limiting should be applied independently to each IP address. This method is not |
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* reliable, as most DDoS attacks use multiple IP addresses. |
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* |
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* @config |
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* @var bool |
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*/ |
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private static $lock_byuserip = false; |
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/** |
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* Time duration (in sections) to deny further search requests after a successful search. |
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* Search requests within this time period while another query is in progress will be |
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* presented with a 429 (rate limit) |
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* |
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* @config |
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* @var int |
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*/ |
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private static $lock_cooldown = 2; |
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/** |
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* Cache key prefix |
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*/ |
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const CACHE_PREFIX = 'RateLimitBegin'; |
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/** |
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* Determines the key to use for saving the current rate |
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* |
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* @param string $itemkey Input key |
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* @return string Result key |
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*/ |
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protected function getCacheKey($itemkey) { |
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$key = self::CACHE_PREFIX; |
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// Add global identifier |
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if($this->config()->get('lock_bypage')) { |
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$key .= '_' . md5($itemkey); |
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} |
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// Add user-specific identifier |
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if($this->config()->get('lock_byuserip') && Controller::has_curr()) { |
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$ip = Controller::curr()->getRequest()->getIP(); |
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$key .= '_' . md5($ip); |
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} |
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return $key; |
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} |
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public function getContent($key, $callback) { |
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// Bypass rate limiting if flushing, or timeout isn't set |
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$timeout = $this->config()->get('lock_timeout'); |
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if(isset($_GET['flush']) || !$timeout) { |
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return parent::getContent($key, $callback); |
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} |
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// Generate result with rate limiting enabled |
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$limitKey = $this->getCacheKey($key); |
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$cache = $this->getCache(); |
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if($lockedUntil = $cache->get($limitKey)) { |
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if(time() < $lockedUntil) { |
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// Politely inform visitor of limit |
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$response = new HTTPResponse_Exception('Too Many Requests.', 429); |
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$response->getResponse()->addHeader('Retry-After', 1 + $lockedUntil - time()); |
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throw $response; |
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} |
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} |
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$lifetime = Config::inst()->get(ContentFilter::class, 'cache_lifetime') ?: null; |
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// Apply rate limit |
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$cache->set($limitKey, time() + $timeout, $lifetime); |
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// Generate results |
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$result = parent::getContent($key, $callback); |
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// Reset rate limit with optional cooldown |
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if($cooldown = $this->config()->get('lock_cooldown')) { |
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// Set cooldown on successful query execution |
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$cache->set($limitKey, time() + $cooldown, $lifetime); |
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} else { |
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// Without cooldown simply disable lock |
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$cache->delete($limitKey); |
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} |
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return $result; |
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} |
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} |
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silverstripe /
silverstripe-versionfeed
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