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From "Plüm, Rüdiger, VF-Group" <ruediger.pl...@vodafone.com>
Subject Re: [PROPOSAL] mod_cloudbeat
Date Mon, 30 Mar 2009 15:10:53 GMT
 

> -----Ursprüngliche Nachricht-----
> Von: Paul Querna 
> Gesendet: Montag, 30. März 2009 17:04
> An: dev@httpd.apache.org
> Betreff: Re: [PROPOSAL] mod_cloudbeat
> 
> On Mon, Mar 30, 2009 at 4:45 PM, Jim Jagielski 
> <jim@jagunet.com> wrote:
> >
> > On Mar 29, 2009, at 11:43 AM, Paul Querna wrote:
> >>
> >> URL Authentication is done by computing an randomly seeded 
> md5 signature
> >> of:
> >>    seed + "$"+ MD5(seed + shared_secret + uri)
> >> This is base64 encoded, and placed in a 'X-Cloudbeat-Auth' header.
> >>
> >
> > Thinking outloud here... The idea I think is to ensure that
> > the X-Cloudbeat-Auth defines an authenticated server, using
> > the fact that it knows the shared secret. But how does the
> > above do that? Say for example that A and B known to each
> > other and B is sending X-Cloudbeat-Auth. This is easy to
> > find out, of course. So I setup B' to send the exact same
> > header and apply a DoS to B causing it to drop/hang/whatever.
> > Won't A just see B' as B, maybe thinking that it had a
> > momentary glitch and came back? It seems to me that we need
> > some sort of IP:port knowledge in there as well.
> 
> In my mind, URL includes the IP/port, so you shouldn't be able to DoS
> it this way.  I guess I should of been clearer by what I meant with
> URL.
> 
> I was thinking about this more, and we should also change the hash to
> sha1, considering it only takes a few days to find md5 collisions if
> you have enough playstation 3s:
>     seed + "$"+ sha1(seed + shared_secret + ip ":"+ port + URI)

Which IP do you use here? The one from the client that sends the request?
Furthermore we should include a timestamp as we are very vulnerable against
replay attacks otherwise.

Regards

Rüdiger


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