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

From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
To: <isapros@xxxxxxxxxxxxx>
Date: Wed, 10 Jan 2007 22:55:10 -0600
I know what you're saying. Been fighting the CES crowd here in Vegas all
week and feel like it's close to Texas Chain Saw Massacre time.
 
Thomas W Shinder, M.D.
Site: www.isaserver.org <http://www.isaserver.org/> 
Blog: http://blogs.isaserver.org/shinder
Book: http://tinyurl.com/3xqb7 <http://tinyurl.com/3xqb7> 
MVP -- ISA Firewalls

 


________________________________

        From: isapros-bounce@xxxxxxxxxxxxx
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Thor (Hammer of God)
        Sent: Wednesday, January 10, 2007 8:43 PM
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        
        
        Crap.  I totally forgot about your issues up there today.  I'm
sorry I was such a prick.  Didn't mean to be - hard day myself.  We'll
pick it up in the morning.
        t
        
        
        On 1/10/07 8:30 PM, "Jim Harrison" <Jim@xxxxxxxxxxxx> spoketh to
all:
        
        

                ..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>
<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 
                

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Follow-Ups:
- [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
  - From: Greg Mulholland
[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

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