meetletacbfree/classes/local/content.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Meeting content download helpers (Adobe Connect proxy).
 *
 * @package    mod_meetletacbfree
 * @copyright  2026 MeetLet <info@meetlet.net>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace mod_meetletacbfree\local;

use mod_meetletacbfree\api\service;
use stdClass;

defined('MOODLE_INTERNAL') || die();

/**
 * Authenticated Moodle proxy for uploaded meeting content files.
 */
class content {
    /**
     * Opaque, HMAC-signed, current-user download URL.
     */
    public static function download_url(int $userid, int $cmid, int $scoid): \moodle_url {
        return new \moodle_url('/mod/meetletacbfree/download_content.php', [
            'k' => self::make_download_token($userid, $cmid, $scoid),
        ]);
    }

    /**
     * Unpack and verify a content download token.
     *
     * @return array{userid:int,cmid:int,cid:int}
     */
    public static function unpack_download_token(string $token): array {
        $token = trim($token);
        if (!preg_match('/^[A-Za-z0-9_-]+$/', $token)) {
            throw new \moodle_exception('errorbadcontenttoken', 'meetletacbfree');
        }
        $b64 = strtr($token, '-_', '+/');
        $pad = strlen($b64) % 4;
        if ($pad) {
            $b64 .= str_repeat('=', 4 - $pad);
        }
        $raw = base64_decode($b64, true);
        if ($raw === false || strlen($raw) < 44) {
            throw new \moodle_exception('errorbadcontenttoken', 'meetletacbfree');
        }
        $mac = substr($raw, 0, 32);
        $payload = substr($raw, 32);
        if (strlen($payload) < 32) {
            throw new \moodle_exception('errorbadcontenttoken', 'meetletacbfree');
        }

        $ids = unpack('Nuid/Ncmid/Ncid/Nexp', substr($payload, 0, 16));
        $nonce = substr($payload, 16, 16);
        $userid = (int)$ids['uid'];
        $cmid = (int)$ids['cmid'];
        $cid = (int)$ids['cid'];
        $expires = (int)$ids['exp'];
        $expected = hash_hmac(
            'sha256',
            'meetletacbfree-content-v1|' . $userid . ':' . $cmid . ':' . $cid . ':' . $expires . '|' . $nonce,
            self::download_secret(),
            true
        );
        if (!hash_equals($expected, $mac)) {
            throw new \moodle_exception('errorbadcontenttoken', 'meetletacbfree');
        }
        if ($expires < time() || $userid <= 0 || $cmid <= 0 || $cid <= 0) {
            throw new \moodle_exception('errorbadcontenttoken', 'meetletacbfree');
        }
        return ['userid' => $userid, 'cmid' => $cmid, 'cid' => $cid];
    }

    /**
     * Find a content item listed under a meeting folder.
     */
    public static function find_in_meeting(service $service, int $meetingscoid, int $scoid): ?stdClass {
        foreach ($service->list_meeting_content($meetingscoid) as $item) {
            if ((int)($item->scoid ?? 0) === $scoid) {
                return $item;
            }
        }
        return null;
    }

    /**
     * Adobe stores uploaded binaries under {url-path}/output/{filename}.
     */
    public static function output_file_url(string $urlpath, string $filename): string {
        $filename = basename(str_replace('\\', '/', $filename));
        if ($filename === '' || strpos($filename, '/') !== false) {
            throw new \moodle_exception('filenotfound', 'error');
        }
        $base = '/' . trim($urlpath, '/');
        if ($base === '/') {
            throw new \moodle_exception('filenotfound', 'error');
        }
        return config::public_url($base . '/output/' . rawurlencode($filename));
    }

    /**
     * Stream a meeting content file to the browser via user SSO.
     */
    public static function serve_download(instance $inst, int $scoid): void {
        global $USER;

        $service = new service();
        $service->login_admin();
        $item = self::find_in_meeting($service, $inst->require_meeting(), $scoid);
        $service->logout();

        if (!$item || empty($item->name) || empty($item->urlpath)) {
            throw new \moodle_exception('filenotfound', 'error');
        }

        $adoberole = roles::resolve_adobe_role($inst->record, $inst->context, (int)$USER->id);
        $permission = $adoberole ?: service::ROLE_PARTICIPANT;
        $auth = sso::provision_and_login($USER, $scoid, $permission);

        $fileurl = self::output_file_url((string)$item->urlpath, (string)$item->name);
        $filename = clean_filename((string)$item->name);
        if ($filename === '') {
            $filename = 'content_' . $scoid;
        }

        $tmpdir = make_request_directory();
        $tmp = $tmpdir . '/content_' . $scoid . '_' . $filename;
        self::fetch_to_path($fileurl, $auth['cookie'], $tmp);

        \core\session\manager::write_close();
        send_temp_file($tmp, $filename);
    }

    /**
     * Download remote content bytes using a BREEZESESSION cookie.
     */
    protected static function fetch_to_path(string $url, string $session, string $dest): void {
        $ch = curl_init($url);
        $fp = fopen($dest, 'wb');
        if ($fp === false) {
            curl_close($ch);
            throw new \moodle_exception('filenotfound', 'error');
        }
        curl_setopt_array($ch, [
            CURLOPT_FILE => $fp,
            CURLOPT_FOLLOWLOCATION => true,
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_TIMEOUT => 300,
            CURLOPT_COOKIE => $session !== '' ? ('BREEZESESSION=' . $session) : '',
        ]);
        $ok = curl_exec($ch);
        $code = (int)curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $size = (int)curl_getinfo($ch, CURLINFO_SIZE_DOWNLOAD);
        curl_close($ch);
        fclose($fp);

        if (!$ok || $code < 200 || $code >= 400 || $size <= 0 || !is_file($dest) || filesize($dest) <= 0) {
            @unlink($dest);
            throw new \moodle_exception('filenotfound', 'error');
        }
    }

    protected static function make_download_token(int $userid, int $cmid, int $scoid): string {
        $expires = time() + DAYSECS * 7;
        $nonce = random_bytes(16);
        $payload = pack('N4', $userid, $cmid, $scoid, $expires) . $nonce;
        $mac = hash_hmac(
            'sha256',
            'meetletacbfree-content-v1|' . $userid . ':' . $cmid . ':' . $scoid . ':' . $expires . '|' . $nonce,
            self::download_secret(),
            true
        );
        return rtrim(strtr(base64_encode($mac . $payload), '+/', '-_'), '=');
    }

    protected static function download_secret(): string {
        return 'mod_meetletacbfree/content/' . get_site_identifier();
    }
}