> -----Ursprüngliche Nachricht----- > Von: Paul Querna > Gesendet: Montag, 30. März 2009 17:18 > An: [email protected] > Betreff: Re: [PROPOSAL] mod_cloudbeat > > On Mon, Mar 30, 2009 at 5:10 PM, "Plüm, Rüdiger, VF-Group" > <[email protected]> wrote: > >> -----Ursprüngliche Nachricht----- > >> Von: Paul Querna > >> Gesendet: Montag, 30. März 2009 17:04 > >> An: [email protected] > >> Betreff: Re: [PROPOSAL] mod_cloudbeat > >> > >> On Mon, Mar 30, 2009 at 4:45 PM, Jim Jagielski > >> <[email protected]> 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. > > Server A wants to talk to B. > > We include server B's IP in the hash that Server A sends to B. (this > prevents B without knowledge of the secret from doing a replay).
But it doesn't prevent A' that sniffed the traffic from A to B to replay. OTOH why fiddle with this auth stuff anyway. We could make it save by using TLS and client certs. Regards Rüdiger
