File.php

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<?php

namespace Elgg\FileService;

use Elgg\Exceptions\DomainException;
use Elgg\Project\Paths;
use Elgg\Security\Base64Url;

class File {

    const INLINE = 'inline';
    const ATTACHMENT = 'attachment';

    private $file;

    private $expires;

    private $disposition;

    private $use_cookie = true;

    public function setFile(\ElggFile $file) {
        $this->file = $file;
    }

    public function getFile(): ?\ElggFile {
        return $this->file;
    }

    public function setExpires(string $expires = '+2 hours'): void {
        $this->expires = strtotime($expires);
    }

    public function setDisposition(string $disposition = self::ATTACHMENT): void {
        if (!in_array($disposition, [self::ATTACHMENT, self::INLINE])) {
            throw new DomainException("Disposition {$disposition} is not supported in " . __CLASS__);
        }
        
        $this->disposition = $disposition;
    }

    public function bindSession(bool $use_cookie = true): void {
        $this->use_cookie = $use_cookie;
    }

    public function getURL(): ?string {

        if (!$this->file->exists()) {
            elgg_log('Unable to resolve resource URL for a file that does not exist on filestore');
            return null;
        }

        $relative_path = '';
        $root_prefix = Paths::sanitize(_elgg_services()->config->dataroot);
        $path = Paths::sanitize($this->file->getFilenameOnFilestore(), false);
        if (str_starts_with($path, $root_prefix)) {
            $relative_path = substr($path, strlen($root_prefix));
        }

        if (!$relative_path) {
            elgg_log('Unable to resolve relative path of the file on the filestore');
            return null;
        }

        if (preg_match('~[^a-zA-Z0-9_\./ ]~', $relative_path)) {
            // Filenames may contain special characters that result in malformatted URLs
            // and/or HMAC mismatches. We want to avoid that by encoding the path.
            $relative_path = ':' . Base64Url::encode($relative_path);
        }

        $data = [
            'expires' => $this->expires ?? 0,
            'last_updated' => filemtime($this->file->getFilenameOnFilestore()),
            'disposition' => $this->disposition === self::INLINE ? 'i' : 'a',
            'path' => $relative_path,
        ];

        if ($this->use_cookie) {
            $data['cookie'] = _elgg_services()->session->getID();
            if (empty($data['cookie'])) {
                return null;
            }
            
            $data['use_cookie'] = 1;
        } else {
            $data['use_cookie'] = 0;
        }

        ksort($data);
        $mac = _elgg_services()->hmac->getHmac($data)->getToken();

        $url_segments = [
            'serve-file',
            "e{$data['expires']}",
            "l{$data['last_updated']}",
            "d{$data['disposition']}",
            "c{$data['use_cookie']}",
            $mac,
            $relative_path,
        ];

        return elgg_normalize_url(implode('/', $url_segments));
    }
}