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<?php |
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declare(strict_types=1); |
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namespace DanBettles\Defence\Filter; |
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use DanBettles\Defence\Envelope; |
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use InvalidArgumentException; |
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use function is_array; |
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use function is_string; |
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use function preg_match; |
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use const false; |
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use const null; |
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use const true; |
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/** |
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* Rejects requests containing the specified user-agent string(s). |
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* |
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* Apparently, some malicious users don't know/think to change the user-agent string in their scripts, so this filter |
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* can be used to quickly reject probing/harmful requests--requests sent via unusual user agents. Commercial |
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* screen-scraping apps identify themselves, and experienced programmers know to use a sensible user-agent string when |
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* working with tools like cURL. |
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* |
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* @phpstan-import-type IncomingFilterOptions from \DanBettles\Defence\Filter\AbstractFilter |
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* |
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* @phpstan-type Selector string|string[] |
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*/ |
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class BannedUserAgentHeaderFilter extends AbstractFilter |
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{ |
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/** |
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* @phpstan-var Selector |
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*/ |
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private $selector; |
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/** |
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* @phpstan-param Selector $selector One/more regular expressions. |
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* @phpstan-param IncomingFilterOptions $options |
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*/ |
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public function __construct($selector, array $options = []) |
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{ |
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parent::__construct($options); |
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$this->setSelector($selector); |
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} |
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public function __invoke(Envelope $envelope): bool |
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{ |
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$request = $envelope->getRequest(); |
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/** @var string|null Contrary to what Scrutinizer thinks */ |
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$uaString = /** @scrutinizer ignore-type */ $request->headers->get('User-Agent'); |
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if (null === $uaString) { |
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// Since there's no user-agent header, we have nothing to check against our blacklist. *In this context*, |
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// then, we have to treat the request as not suspicious -- even though it *is* suspicious that there's no |
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// user-agent header. |
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return false; |
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} |
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foreach ((array) $this->getSelector() as $selector) { |
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if (preg_match($selector, $uaString)) { |
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$this->envelopeAddLogEntry($envelope, 'The request was made via a banned user agent.'); |
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return true; |
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} |
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} |
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return false; |
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} |
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/** |
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* @phpstan-param Selector $selector One/more regular expressions. |
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* @throws InvalidArgumentException If the selector is invalid |
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*/ |
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private function setSelector($selector): self |
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{ |
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if ( |
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empty($selector) |
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/** @phpstan-ignore-next-line */ |
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|| (!is_array($selector) && !is_string($selector)) |
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) { |
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throw new InvalidArgumentException('The selector is invalid'); |
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} |
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$this->selector = $selector; |
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return $this; |
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} |
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/** |
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* @phpstan-return Selector |
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*/ |
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public function getSelector() |
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{ |
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return $this->selector; |
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} |
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} |
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danbettles /
defence
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