BookStack/app/Util/WebSafeMimeSniffer.php
Dan Brown ae155d6745
Added safe mime sniffing to prevent serving HTML
(Amoung other content types)
For #3027
2021-10-31 17:58:56 +00:00

65 lines
1.5 KiB
PHP

<?php
namespace BookStack\Util;
use finfo;
/**
* Helper class to sniff out the mime-type of content resulting in
* a mime-type that's relatively safe to serve to a browser.
*/
class WebSafeMimeSniffer
{
/**
* @var string[]
*/
protected $safeMimes = [
'application/json',
'application/octet-stream',
'application/pdf',
'image/bmp',
'image/jpeg',
'image/png',
'image/gif',
'image/webp',
'image/avif',
'image/heic',
'text/css',
'text/csv',
'text/javascript',
'text/json',
'text/plain',
'video/x-msvideo',
'video/mp4',
'video/mpeg',
'video/ogg',
'video/webm',
'video/vp9',
'video/h264',
'video/av1',
];
/**
* Sniff the mime-type from the given file content while running the result
* through an allow-list to ensure a web-safe result.
* Takes the content as a reference since the value may be quite large.
*/
public function sniff(string &$content): string
{
$fInfo = new finfo(FILEINFO_MIME_TYPE);
$mime = $fInfo->buffer($content) ?: 'application/octet-stream';
if (in_array($mime, $this->safeMimes)) {
return $mime;
}
[$category] = explode('/', $mime, 2);
if ($category === 'text') {
return 'text/plain';
}
return 'application/octet-stream';
}
}