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Added safe mime sniffing to prevent serving HTML
(Amoung other content types) For #3027
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Original file line number | Diff line number | Diff line change |
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<?php | ||
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namespace BookStack\Util; | ||
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use finfo; | ||
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/** | ||
* 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 | ||
{ | ||
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/** | ||
* @var string[] | ||
*/ | ||
protected $safeMimes = [ | ||
'application/json', | ||
'application/octet-stream', | ||
'application/pdf', | ||
'image/bmp', | ||
'image/jpeg', | ||
'image/png', | ||
'image/gif', | ||
'image/webp', | ||
'image/avif', | ||
'image/heic', | ||
'text/css', | ||
'text/csv', | ||
'text/javascript', | ||
'text/json', | ||
'text/plain', | ||
'video/x-msvideo', | ||
'video/mp4', | ||
'video/mpeg', | ||
'video/ogg', | ||
'video/webm', | ||
'video/vp9', | ||
'video/h264', | ||
'video/av1', | ||
]; | ||
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/** | ||
* Sniff the mime-type from the given file content while running the result | ||
* through an allow-list to ensure a web-safe result. | ||
* Takes the content as a reference since the value may be quite large. | ||
*/ | ||
public function sniff(string &$content): string | ||
{ | ||
$fInfo = new finfo(FILEINFO_MIME_TYPE); | ||
$mime = $fInfo->buffer($content) ?: 'application/octet-stream'; | ||
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if (in_array($mime, $this->safeMimes)) { | ||
return $mime; | ||
} | ||
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[$category] = explode('/', $mime, 2); | ||
if ($category === 'text') { | ||
return 'text/plain'; | ||
} | ||
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return 'application/octet-stream'; | ||
} | ||
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} |
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