Extracting user uploaded archives without exposing to ZipBombs?

Question

My question is simple: how do I make sure (or prevent) a user from uploading an archive that upon extraction fills the entire disc space (a so-called ZipBomb)? I am using PHP.

Answer 1

Before extracting your archive, use the PHP Zip library functions to ensure that, when extracted, the contents fall within a total size limit.

For example:

$zip = zip_open('uploaded.zip');
$file = zip_read($zip);
$totalsize = 0;

while ($file) {
    $totalsize += zip_entry_filesize($file);
    $file = zip_read($zip); // read next file
}

zip_close($zip);

if ($totalsize > SIZE_LIMIT) {
    // not allowed!
}