file.php

<?php
 
namespace Bitrix\Bizproc\Controller;
 
use Bitrix\Main;
use Bitrix\Main\Engine\Response\BFile;
use Bitrix\Main\Error;
 
class File extends Base
{
    private const TOKEN_SALT = 'bizproc.file.show';
 
    public function configureActions(): array
    {
        $configureActions = parent::configureActions();
        $configureActions['show'] = [
            '-prefilters' => [
                Main\Engine\ActionFilter\Csrf::class,
                Main\Engine\ActionFilter\Authentication::class,
            ],
            '+prefilters' => [
                new Main\Engine\ActionFilter\CloseSession(),
            ]
        ];
 
        return $configureActions;
    }
 
    public function showAction($token)
    {
        [$fileId] = self::extractToken($token);
        $file = null;
 
        if ($fileId)
        {
            $file = \CFile::getFileArray($fileId);
        }
 
        if (!$file)
        {
            $this->addError(new Error('No file'));
            return null;
        }
 
        return BFile::createByFileData($file);
    }
 
    public static function getPublicLink(int $fileId): string
    {
        return Main\Engine\UrlManager::getInstance()->create(
            'bizproc.file.show',
            [
                'token' => static::generateToken($fileId),
            ],
            true
        )->getUri();
    }
 
    private static function generateToken(int $fileId)
    {
        $signer = new Main\Security\Sign\Signer;
        return $signer->sign((string) $fileId, self::TOKEN_SALT);
    }
 
    private static function extractToken(string $token): array
    {
        $signer = new Main\Security\Sign\Signer;
 
        try
        {
            $unsigned = $signer->unsign($token, self::TOKEN_SALT);
            $result = [$unsigned];
        }
        catch (\Exception $e)
        {
            $result = [null];
        }
 
        return $result;
    }
}