123 lines
3.1 KiB
PHP
123 lines
3.1 KiB
PHP
<?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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$key = self::CACHE_PREFIX;
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// Add global identifier
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if(Config::inst()->get(get_class(), 'lock_bypage')) {
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$key .= '_' . md5($itemkey);
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}
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// Add user-specific identifier
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if(Config::inst()->get(get_class(), 'lock_byuserip') && Controller::has_curr()) {
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$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 = Config::inst()->get(get_class(), '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 = $cache->load($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 $response;
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}
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}
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// Apply rate limit
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$cache->save(time() + $timeout, $limitKey);
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// Generate results
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$result = parent::getContent($key, $callback);
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// Reset rate limit with optional cooldown
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if($cooldown = Config::inst()->get(get_class(), 'lock_cooldown')) {
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// Set cooldown on successful query execution
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$cache->save(time() + $cooldown, $limitKey);
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} else {
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// Without cooldown simply disable lock
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$cache->remove($limitKey);
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}
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return $result;
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}
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}
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