Re: public secret and public radius server. Is it secure?

[sophana <sophana@zizi.ath.cx>]

Alan DeKok wrote:

My problem is that there can be hotspots on dynamic ip addresses.
The solution I found actually is to have an unique secret shared with 
all hotspots.
So the secret is known by everybody.
    

  Or, make the hotspots NOT have dynamic IP's.  There's no reason why
they should have dynamic IP's.

  

In my project, I don't own the hotspots, and don't know about the hotspots ISPs.
The hotspots communicate to the radius server though the internet.

- What can a malicious user can do with the secret? Can it alter 
accounting and other things? (chillispot uses chap auth-type)
    

  If someone knows the secret, he can do *anything* to the packets
without the RADIUS server being able to tell.
  

Ok. I don't know much about the radius protocol details, maybe you could help me understanding how secure would be a solution where the secret is know by everybody.
Chillispot uses CHAP authentication with a different secret per hotspot.
I consider is part as secure.
Now, once a user is authenticated, how does the nas send accounting info?
Does it have to authenticate again, or is its ip address (and its (public known)secret) sufficient to authenticate?
Do you need at least a session id?

Imagine that the malicious use cannot listen to the radius communications. What can it do without authentication?

I need security, because I will use accounting info to perform facturation...

Thanks for your great help.

- Is there a way of maintaining a per hotspot secret with dynamic ip 
addresses?
    

  Not really, no.
  

this means I must use a vpn client to connect to the radius server?
I would have liked a simple chillispot installation...

Regards
Sophana KOK