owncloud/core

<?php
/**
 * @author Georg Ehrke <georg@owncloud.com>
 * @author Joas Schilling <coding@schilljs.com>
 * @author Olivier Paroz <github@oparoz.com>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 *
 * @copyright Copyright (c) 2018, ownCloud GmbH
 * @license AGPL-3.0
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License, version 3,
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */
namespace OC\Preview;

use OCP\Files\File;
use OCP\Files\FileInfo;
use OCP\Preview\IProvider2;
use Rhukster\DomSanitizer\DOMSanitizer;

class SVG implements IProvider2 {
    /**
     * {@inheritDoc}
     */
    public function getMimeType() {
        return '/image\/svg\+xml/';
    }

    /**
     * {@inheritDoc}
     */
    public function getThumbnail(File $file, $maxX, $maxY, $scalingUp) {
        try {
            $svg = new \Imagick();
            $svg->setBackgroundColor(new \ImagickPixel('transparent'));

            $stream = $file->fopen('r');
            $content = \stream_get_contents($stream);
            if (\strpos($content, '<?xml') !== 0) {
                $content = '<?xml version="1.0" encoding="UTF-8" standalone="no"?>' . $content;
            }
            \fclose($stream);

            # sanitize SVG content
            $output = self::sanitizeSVGContent($content);

            $svg->readImageBlob($output);
            $svg->setImageFormat('png32');
        } catch (\Exception $e) {
            \OCP\Util::writeLog('core', $e->getmessage(), \OCP\Util::ERROR);
            return false;
        }

        //new image object
        $image = new \OC_Image();
        $image->loadFromData($svg);
        //check if image object is valid
        if ($image->valid()) {
            $image->scaleDownToFit($maxX, $maxY);

            return $image;
        }
        return false;
    }

    /**
     * @inheritdoc
     */
    public function isAvailable(FileInfo $file) {
        return true;
    }

    public static function sanitizeSVGContent(string $content): string {
        $sanitizer = new DOMSanitizer(DOMSanitizer::SVG);
        $sanitizer->addDisallowedTags(['image']);
        $sanitizer->addDisallowedAttributes(['xlink:href']);
        return $sanitizer->sanitize($content);
    }
}