php - Cancel an HTTP POST request server side

Question

I am trying to write a script for uploading large files (>500MB). I would like to do some authentication before the upload is processed, eg:

$id = $_GET['key'];
$size = $_GET['size'];
$time = $_GET['time'];
$signature = $_GET['signature'];

$secret = 'asdfgh123456';

if(sha1($id.$size.$time.$secret) != $signature){
echo 'invalid signature';
exit;
}
process upload...

unfortunately php only runs this code after the file has been uploaded to a temp directory, taking up valuable server resources. Is there a way to do this before the upload happens? I have tried similar things with perl/cgi but the same thing happens.

Answer 1

Wow, already 5 answers telling how it can't be done. mod_perl to the rescue, here you can reject a request before the whole request body is uploaded.