Re: How To Limit FIle Uploader Against Hijackers?

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On Sat, May 30, 2009 at 7:02 PM, Ashley Sheridan
<ash@xxxxxxxxxxxxxxxxxxxx>wrote:

> On Sat, 2009-05-30 at 17:54 +0200, Nitsan Bin-Nun wrote:
> > That's the verification that my layer does. I'm not sure whether that's
> > enough or not.
> >
> > On Sat, May 30, 2009 at 4:43 PM, Michael A. Peters <mpeters@xxxxxxx>
> wrote:
> >
> > > Nitsan Bin-Nun wrote:
> > >
> > >  On Sat, May 30, 2009 at 3:26 PM, Michael A. Peters <mpeters@xxxxxxx
> <mailto:
> > >> mpeters@xxxxxxx>> wrote:
> > >>
> > >>    Nitsan Bin-Nun wrote:
> > >>
> > >>        Hi
> > >>
> > >>        I have wrote a file uploader in PHP, and I don't want people to
> > >>        hijack it
> > >>        (get direct links, download whenever they want, etc).
> > >>
> > >>        Currently I have placed the uploaded files one directory up
> from
> > >>        the www
> > >>        root, and I'm hosting the files mime type in order to serve
> them
> > >>        on the fly.
> > >>
> > >>        I'm trying to think how should I secure this website, I don't
> > >>        want people to
> > >>        get direct links,etc.
> > >>
> > >>        Currently the links are being check with the $_SERVER['refer']
> > >>        variables and
> > >>        it being compared to the one in my config file.
> > >>
> > >>        Any ideas will be very appreciated! Thanks!
> > >>
> > >>
> > >>        By the way, does this file serving feature takes a lot of load
> > >>        from the
> > >>        server? if so then what are the other options? can I serve
> these
> > >>        files w/o
> > >>        PHP involved? lets say only by some sort of apache module or
> > >>        anything like
> > >>        that?
> > >>
> > >>
> > >>    What I do -
> > >>
> > >>    Files for restricted access are outside the web root.
> > >>    php wrapper script verifies the credentials of user to download the
> > >>    file (IE via a post token, session ID, etc.) and if allowed, it
> then
> > >>    sends the real file.
> > >>
> > >>    I use mod_rewrite (apache) to send requests for the real file to
> the
> > >>    php wrapper script so that the linked file has the same name as the
> > >>    real file (lets me use the same wrapper for lots of different
> files).
> > >>
> > >>    As far as load on the server, no - I don't think it costs a lot as
> > >>    far as system resources.
> > >>
> > >>
> > >>
> > >> Thank you for the fast answer.
> > >>
> > >> I'm doing the same regarding the php wrapper layer, but the thing is
> that
> > >> I just don't know what verification exams should I do in the php
> wrapping
> > >> layer.
> > >> I'm not sure what is the way that it should be done.
> > >>
> > >
> > > I check the referrer, assuming no other credential is required, if it
> is
> > > from an approved site or not sent (some people disable sending the
> > > http_referrer in their browser), I allow it. Otherwise I don't.
> > >
> That should be fine for downloading files. There will be an issue if
> they are media files and you want to play them from a browser plugin, as
> no plugin I've ever seen actually passes the referrer header.
>
>
> Ash
> www.ashleysheridan.co.uk
>
>

I'm sending downloading headers, there will be no options of playing it from
the browser's plugin.
Thank you both for your comments. I have decided that referrer check is
enough for now :)

Nitsan

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