ServeFileHandler.php

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<?php

namespace Elgg\Application;

use DateTime;
use Elgg\Config;
use Elgg\Filesystem\MimeTypeService;
use Elgg\Http\Request;
use Symfony\Component\HttpFoundation\BinaryFileResponse;
use Symfony\Component\HttpFoundation\Response;
use Elgg\Security\Base64Url;
use Elgg\Security\HmacFactory;

class ServeFileHandler {

    private $hmac;

    private $config;
    
    protected $mimetype;

    public function __construct(HmacFactory $hmac, Config $config, MimeTypeService $mimetype) {
        $this->hmac = $hmac;
        $this->config = $config;
        $this->mimetype = $mimetype;
    }

    public function getResponse(Request $request) {

        $response = new Response();
        $response->prepare($request);

        $path = implode('/', $request->getUrlSegments(true));
        if (!preg_match('~serve-file/e(\d+)/l(\d+)/d([ia])/c([01])/([a-zA-Z0-9\-_]+)/(.*)$~', $path, $m)) {
            return $response->setStatusCode(400)->setContent('Malformatted request URL');
        }

        list(, $expires, $last_updated, $disposition, $use_cookie, $mac, $path_from_dataroot) = $m;

        if ($expires && $expires < time()) {
            return $response->setStatusCode(403)->setContent('URL has expired');
        }
        
        // revert spaces from elgg_normalize_url()
        // not using urldecode because it could replace to much
        $path_from_dataroot = str_replace('%20', ' ', $path_from_dataroot);

        $hmac_data = [
            'expires' => (int) $expires,
            'last_updated' => (int) $last_updated,
            'disposition' => $disposition,
            'path' => $path_from_dataroot,
            'use_cookie' => (int) $use_cookie,
        ];
        if ((bool) $use_cookie) {
            $hmac_data['cookie'] = $this->getCookieValue($request);
        }
        
        ksort($hmac_data);

        $hmac = $this->hmac->getHmac($hmac_data);
        if (!$hmac->matchesToken($mac)) {
            return $response->setStatusCode(403)->setContent('HMAC mismatch');
        }

        // Path may have been encoded to avoid problems with special chars in URLs
        if (str_starts_with($path_from_dataroot, ':')) {
            $path_from_dataroot = Base64Url::decode(substr($path_from_dataroot, 1));
        }

        $filenameonfilestore = "{$this->config->dataroot}{$path_from_dataroot}";

        if (!is_readable($filenameonfilestore)) {
            return $response->setStatusCode(404)->setContent('File not found');
        }

        $actual_last_updated = filemtime($filenameonfilestore);
        if ($actual_last_updated != $last_updated) {
            return $response->setStatusCode(403)->setContent('URL has expired');
        }

        $if_none_match = $request->headers->get('if_none_match');
        if (!empty($if_none_match)) {
            // strip mod_deflate suffixes
            $request->headers->set('if_none_match', str_replace('-gzip', '', $if_none_match));
        }

        $etag = '"' . $actual_last_updated . '"';
        $response->setPublic()->setEtag($etag);
        if ($response->isNotModified($request)) {
            return $response;
        }

        $public = !(bool) $use_cookie;
        $content_disposition = $disposition == 'i' ? 'inline' : 'attachment';

        $headers = [
            'Content-Type' => $this->mimetype->getMimeType($filenameonfilestore),
            'X-Content-Type-Options' => 'nosniff',
        ];
        $response = new BinaryFileResponse($filenameonfilestore, 200, $headers, $public, $content_disposition);
        
        $sendfile_type = $this->config->x_sendfile_type;
        if ($sendfile_type) {
            $request->headers->set('X-Sendfile-Type', $sendfile_type);

            $mapping = (string) $this->config->x_accel_mapping;
            $request->headers->set('X-Accel-Mapping', $mapping);

            $response->trustXSendfileTypeHeader();
        }
        
        $response->prepare($request);

        if (empty($expires)) {
            $expires = strtotime('+1 year');
        }
        
        $expires_dt = (new DateTime())->setTimestamp($expires);
        $response->setExpires($expires_dt);

        $response->setEtag($etag);
        return $response;
    }

    private function getCookieValue(Request $request) {
        $config = $this->config->getCookieConfig();
        $session_name = $config['session']['name'];
        return $request->cookies->get($session_name, '');
    }
}