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From "Thomas Lindgren" <thomas.lindg...@diino.net>
Subject How to reject requests before request body is sent?
Date Mon, 24 Nov 2008 16:18:58 GMT
Hi all,

I'm using mod_perl2. I'd like to reject user requests, e.g., very large
PUTs, after examining headers and authorizing the user, but before the
request body is read. Quota checking could be an example of where this is
useful.

However, at this time, even if I return an error in the handler, it
(surprisingly) seems as if the request body still is uploaded. What to do?

Here is a boiled-down config, which just returns an error code after reading
the header. In the real code, I also examine the headers a bit before
deciding, but here I'm just interested in the case when the request is
rejected. The example below uses the HeaderParser hook, but the same things
seems to happen with a Fixup handler.

...
<Location /test>
   PerlHeaderParserHandler Test::Reject
</Location>

The handler itself just returns an error code:

...
sub handler {
  my  $r = shift;
  return Apache2::Const::HTTP_INSUFFICIENT_STORAGE;
}

Running a big PUT to $SERVER with curl transfers the body anyway (but then
returns the error):

# curl -o put.txt --basic --user a:b -T example.vmdk 'http://
$SERVER/test/foo.vmdk'
  % Total    % Received % Xferd  Average Speed   Time    Time     Time
Current
                                 Dload  Upload   Total   Spent    Left
Speed
  4 2743M    0     0    4  123M      0  9185k  0:05:05  0:00:13  0:04:52
10.4M^C

The only way to trigger an early close so far has been to die in the
handler, which confuses clients and so on.

The server could as a worst case alternative actually close the socket, but
that feels inelegant and hackish. So, my question to the esteemed list, how
should this sort of thing best be done? Have I forgotten something basic?
Should I return something else? Is there a more appropriate phase to do
this? Should I do it another way entirely?

Best,
Thomas

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