[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

From: "Jim Harrison" <Jim@xxxxxxxxxxxx>
To: <isapros@xxxxxxxxxxxxx>
Date: Wed, 10 Jan 2007 20:30:17 -0800
..maybe I'm just tired...

I spent two hours trying to get home tonight and I'm clearly not in my
mind (right or otherwise).

Forget I wrote and we'll start over tomorrow...

 

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
On Behalf Of Thor (Hammer of God)
Sent: Wednesday, January 10, 2007 8:18 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

 

That's exactly what I'm talking about.  And precisely the configuration
I deploy:

My FE is in the authenticated segment of the DMZ - and a member of my
internal domain; however, the "recommended protocols" the Exchange group
recommends are not necessary- and thus, Steve's contention that "CIFS
and all that other stuff... Might as well just be internal" I reject.  I
only allow Kerberos-Sec, LDAP, LDAP GC, Ping and DNS only from my FE to
the internal DC's.  And only HTTP to the BE's.  

Even if the other prots WERE required, it would still be far smarter to
deploy the FE in the authenticated DMZ with limited access than to just
give full stack access to the ENTIRE internal network.   This is a
deployment of a services made available (initially) to a global,
anonymous, untrusted network. 

Maybe I'm not properly articulating my point, but I have to say I'm
really surprised that we are having this conversation...

t


On 1/10/07 7:10 PM, "Jim Harrison" <Jim@xxxxxxxxxxxx> spoketh to all:

C'mon, Tim; I know what your deployment recommendations are; this isn't
it.
He wants to extend his domain via "remote membership"; not create a
separate domain.
 

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
On Behalf Of Thor (Hammer of God)
Sent: Wednesday, January 10, 2007 4:26 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
 
Because it's safer that way, that's why... That's what an authenticated
access DMZ perimeter is for- with a CAS server that presents logon
services to any Internet user, I would (and, in fact, require) that the
server be in a least-privileged authenticated access perimeter network
that limits that servers communications to the minimum required for
required functionality - and only to the hosts it needs to talk to.

Let's say there is a front-end implementation issue or coding
vulnerability: the CAS on the internal network would allow unfettered,
full-stack access to the internal network.  A CAS in a perimeter DMZ
would mitigate potential exposure in the event of a 0day or
configuration issue. 

"Safer on the internal network" is a complete misnomer when it comes to
servers presenting services to an untrusted network. 

t


On 1/10/07 3:04 PM, "Jim Harrison" <Jim@xxxxxxxxxxxx> spoketh to all:
Why would you want to place a member of your internal domain in your
DMZ, fer chrissakes?!?
Hosting any domain member in the DMZ is a difficult proposition;
especially where NAT is the order of the day.
You can either use a network shotgun at your firewall or attempt to use
your facvorite VPN tunnel across the firewall to the domain.

Jim 

________________________________


From: isapros-bounce@xxxxxxxxxxxxx on behalf of Jason Jones
Sent: Wed 1/10/2007 2:35 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

From what I can gather, the new CAS role now uses RPC to communicate
with the back-end (not sure of new name!) servers so I am guessing that
this is an "RPC isn't safe across firewalls" type stance. Which I guess
for a PIX, is a pretty true statement.

Just think how much safer the world will be when firewalls can
understand dynamic protocols like RPC...maybe one day firewalls will
even be able to understand and filter based upon RPC interface...maybe
one day... :-D ;-)

Shame the Exchange team can't see how much ISA changes the traditional
approach to DMZ thinking...kinda makes you think that both teams work
for a different company :-(
Jason Jones | Silversands Limited | Desk: +44 (0)1202 360489 | Mobile:
+44 (0)7971 500312 | Fax: +44 (0)1202 360900 | Email:
jason.jones@xxxxxxxxxxxxxxxxx <mailto:jason.jones@xxxxxxxxxxxxxxxxx>
<mailto:jason.jones@xxxxxxxxxxxxxxxxx>  

  

________________________________


From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
On Behalf Of Greg Mulholland
Sent: 10 January 2007 22:07
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

I seriously hope that they have take different paths and these are not
limitations on the software or it is going to mean a nice little
redesign and break from custom..

Greg
----- Original Message ----- 
From: Jason Jones <mailto:Jason.Jones@xxxxxxxxxxxxxxxxx>
<mailto:Jason.Jones@xxxxxxxxxxxxxxxxx>   
To: isapros@xxxxxxxxxxxxx 
Sent: Thursday, January 11, 2007 8:25 AM
Subject: [isapros] ISA, Exchange 2007 and Perimeter Networks


Hi All, 

I heard today from an Exchange MVP colleague that members of the
Exchange team (Scott Schnoll) are saying that they (Microsoft) do not
support placing the new Exchange 2007 Client Access Server (like the old
Exch2k3 FE role) role into a perimeter network. Has anyone else heard
the same? This sounds very similar to Exchange admins of old when they
didn't really understand modern application firewalls like ISA could do
- RPC filter anyone???
http://groups.google.co.uk/group/microsoft.public.exchange.design/browse
_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&rn
um=2&hl=en#4db165c21599cf9b
<http://groups.google.co.uk/group/microsoft.public.exchange.design/brows
e_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+i
sa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>
<http://groups.google.co.uk/group/microsoft.public.exchange.design/brows
e_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&r
num=2&hl=en#4db165c21599cf9b>
<http://groups.google.co.uk/group/microsoft.public.exchange.design/brows
e_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+i
sa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>
<http://groups.google.co.uk/group/microsoft.public.exchange.design/brows
e_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&r
num=2&hl=en#4db165c21599cf9b>  

I have just about managed to convince Exchange colleagues (and
customers) of the value of placing Exchange FE servers in a separate
security zone from BE servers, DC's etc and now I here this...

Are the Exchange team confusing the old traditional DMZ's with what ISA
can achieve with perimeter networks? 

From what I believe, it is good perimeter security practice to place
servers which are Internet accessible into different security zones than
servers that are purely internal. Therefore, the idea of placing
Exchange 2003 FE servers in an ISA auth access perimeter network with
Exchange 2003 BE servers on the internal network has always seemed like
a good approach. It also follows a good least privilege model. 

Is this another example of the Exchange and ISA teams following
different paths???? 

Please tell me that I am wrong and that I am not going to have to start
putting all Exchange roles, irrespective of security risk, on the same
network again!!!!

Comments? 

Cheers 

JJ 

All mail to and from this domain is GFI-scanned. 


 

  

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References:
- [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
  - From: Thor (Hammer of God)
[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

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