Firewall Wizards: Re: Radius access from provider to internal MS ISA Server

[Paul Robertson <proberts () patriot net>]

On Thu, 4 Jul 2002, Christoph Steigmeier wrote:

> Hello
>
> Our network-engineers are planing a vpn. The access should be done through
> a selected local internet provider. The authentication for the
> ppp-connection to the provider should be authenticated using the chap
> protocol which is then forwarded from the isp's dialin to our radius
> server in our corporate network to validate uid/pw. After this the
> vpn-connection can be initialized through our vpn-gateways.
>
> My question: I am not sure if it is good to allow the providers
> radius-proxys to access our radiusservers (MS ISA) in our internal net
> without an additional radiusproxy in our dmz. Our engineers argument, that
> these will be expensive and pointless, because only the ip from the
> providers radius would be granted, and that dos- and spoofing protection
> on the firewalls is enough, and that an additional radiusproxy will not
> prohibit unauthorized use of the connection. I am also not so sure if it
> is a good thing to administrate both rights in one directory eg.
I prefer to keep internal and external authentication realms different, so 
that compromise of the credentials is limited in scope (your ISP will be 
able to sniff the CHAP authentication.)  If you're using one-time tokens, 
that's not a big deal, if you've got administrative users coming in with 
passwords, then it may be.  I'd vote for seperate authentication servers in 
the DMZ with just the ISP's servers able to access them, but it probably 
requires an additional set of credentials for users (I'm not sure that's 
bad, lots of people tend to disagree.)

Given the price of PCs, cost shouldn't be much of an issue.

Paul
-----------------------------------------------------------------------------
Paul D. Robertson      "My statements in this message are personal opinions
proberts () patriot net      which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assesment, TruSecure Corporation

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