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

From: "Gerald G. Young" <g.young@xxxxxxxx>
To: <isapros@xxxxxxxxxxxxx>
Date: Fri, 12 Jan 2007 09:27:25 -0500
If it’s participating in the domain, add the subnet to AD, especially if you 
have more than one AD site (I consider this a best practice).  A lot of funny 
things can occur with Active Directory aware applications when they can’t 
tell which site they belong to.  Exchange (2003), for instance, won’t start 
an information store.

 

Cordially yours,

Jerry G. Young II

Product Engineer - Senior

Platform Engineering, Enterprise Hosting

NTT America, an NTT Communications Company

 

22451 Shaw Rd.

Sterling, VA 20166

 

Office: 571-434-1319

Fax: 703-333-6749

Email: g.young@xxxxxxxx

 

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On 
Behalf Of Jason Jones
Sent: Friday, January 12, 2007 6:53 AM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

 

Either way, I think the idea of an intranet CAS and extranet CAS is probably a 
good approach - the extranet CAS one would assume could then go into the auth 
access perimeter network whilst the intranet one could stay on the LAN. In this 
model, each CAS has a different security risk and hence could be put into 
different security zones. 

 

Would it be such a bad thing to add the perimeter subnet to the AD site? It 
will have domain members in it after all...

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> 

 

 

________________________________

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On 
Behalf Of Greg Mulholland
Sent: 12 January 2007 05:35
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

doing a little bit more reading the only thing i can think might be the reason 
is that apparently each mailbox server needs to have a CAS server in its AD 
site. Therefore they recommend you keep the cas box on the same lan. Also in 
multi domain environments this would add more design considerations. Also in 
larger environments you might need 2 CAS boxes, one for internal users and one 
for external users, for the sake of keeping outbound lan access out of the dmz 
or better design.

 

but im not sure about the whole idea of the "swiss cheese" argument. seems a 
bit like flogging a dead horse to me..i dont see how or why it wouldn't work in 
the dmz environment. 

 

greg

 

 

        ----- Original Message ----- 

        From: Thomas W Shinder <mailto:tshinder@xxxxxxxxxxx>  

        To: isapros@xxxxxxxxxxxxx 

        Sent: Friday, January 12, 2007 3:22 PM

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

         

        WORD!

         

        I’ll gladly joining you in that public nut-kicking when the time 
comes. What I want to understand first is what are the protocol requirements 
for the CAS to the back-end components, and what their rationale is for making 
the statements that have been reported so far. They might have a good point, 
and if they have it, I want to hear it. But if the point is ‘it’s too 
hard” or “I don’t understand network security, I just say what my boss 
tells me to say” or “I’m on the take with Syphco” then those aren’t 
valid and body parts will deserve some shaking up in the public square. The 
least they can do is state “we don’t have the time or inclination to show 
you have to provide the highest level of network security, but it is possible 
to do it right, we’re just not going to show you how to do it” as a 
disclaimer. With that, we can then go ahead and help those who want to be 
helped J

         

        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Thor (Hammer of God)
        Sent: Thursday, January 11, 2007 6:40 PM
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

         

        It may be just this type of “beating it to death” that is required 
to get the Exchange group’s attention.  I don’t really care if they don’t 
support “perimeter network” deployments as long as ISA is an exception.  I 
have every intention to ensure that an ISA authenticated perimeter network DMZ 
segment “in front” of the CAS server is fully supported if the proper 
protocols are allowed.  I will make sure to press them into officially stating 
why it is not supported.  Even so, if they try that, I will publicly kick them 
in the nuts. 
        
        t
        
        
        On 1/11/07 4:15 PM, "Jason Jones" <Jason.Jones@xxxxxxxxxxxxxxxxx> 
spoketh to all:

        Hi Amy,
        
        I am not really sure for their reasoning, but think it is based around 
the "Swiss cheese", don't pass intradomain traffic across a normal firewall 
argument.
        
        Sorry, my bad for using the term DMZ, the exact phrase used by Scholl 
is "It's true. The Client Access Server (CAS), which among other things 
includes the OWA feature, is not supported in a perimeter network (aka a DMZ).  
Instead you'll deploy one or more CASs inside your organization and put a 
robust firewall such as ISA 2006 in front of it." I am guessing from experience 
of other Exchange team recommendations that when they say perimeter network 
they really mean a traditional DMZ which is created using traditional packet 
filter firewalls. The recommended deployment is to put the CAS on the internal 
network e.g. on the same network as the Exchange back-end servers. Once the CAS 
is on the internal network, it should then be published to the Internet using 
ISA.
        
        This design if fine if you want a simple open network where all servers 
exist in the same security zone and hence all trust each other, but many people 
are now trying to better this design by placing different types of servers into 
different security zones based upon their risk level and internet presence - 
say hello to the ISA auth access perimeter network! ;-) 
        
        Basically I think it all harks back to the "don't put domain members in 
a DMZ" mantra which is a pretty fair statement when using PF firewalls like 
PIX, but things have moved on as least privilege authenticated access perimeter 
networks with ISA are now getting advanced enough to challenge this argument. 
Maybe the difference between a PIX firewall and ISA firewall is just too subtle 
for some people???
        
        Think we have now done this to death now!! - be very surprised if the 
Exchange team go back on these type of statements though. I remember Tom 
banging his head against a brick wall with Henrik based upon one of his 
MSExchange.org articles which said "not in the DMZ" type statements.
        
        JJ

        
________________________________


        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Amy Babinchak
        Sent: 11 January 2007 23:15
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        
        Jason,
         
        What’s the reasoning behind CAS not in the DMZ? Where to they want 
it? Handing nude off the router? Behind a firewall?
         
        If the later, then just drop the out dated DMZ language. Most firewall 
admins think that DMZ means nude off the other port on my nat box. Your least 
priv design puts CAS safely behind a firewall.
         
        
        Amy Babinchak
        Harbor Computer Services

________________________________

        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Jason Jones
        Sent: Thursday, January 11, 2007 5:58 PM
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        
        Thanks Amy - maybe I am being a little oversensitive, just didn't 
expect some of the initial responses.
        
        I tend to avoid most of the main mailing lists, probably for similar 
reasons as others, and I tend to hang out at isaserver.org 95% of the time. 
Hence maybe why only Tom (and Stefan) tend to see my input and views on stuff.
        
        Tom invited me to this list as he felt it would be a good place for me 
to pose all the questions that he can't answer or go unreplied on isaserver.org
        
        I really do value the combined "ISA brain power" here, but just think 
it could be a little more forgiving and friendly at times...having said that I 
have found answers here that I just couldn't get elsewhere, so don't 
misunderstand me as ungrateful.
        
        Anyhow back to the "core issue", from what I hearing from Exchange MVP 
contacts, MS are playing the "CAS in a DMZ is totally unsupported" tune very 
strongly. This is a real shame as it looks like I will never be able to deploy 
the existing least privilege design with Exchange 2007 without fear of 
customers coming back to us after trying to log PSS calls or getting other 
non-ISA firewall guys in who slate the design...oh well, at least ISA will 
still involved to some degree, just not as cool as it could be...
        
        JJ  
        
        
          

________________________________

        
        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Amy Babinchak
        Sent: 11 January 2007 15:09
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        Jason don’t get discouraged. The changes in Exchange are monumental 
so there are bound to be disagreements and changes of opinion on how to best 
secure it. The concept of an authenticated access DMZ in a separate security 
zone allowing only a very minimal set of protocols is a completely foreign 
concept to 99% of firewall admins out there. That fact you are even thinking 
about this stuff put you in an elite class. The rest are still poking holes and 
setting up VLANs. 
         
        Tom, Thor and Jim can be a bit clubby and a little overly poky to new 
comers. It’s a twitch they developed after participating on the ISA server 
mailing list. It got worse when they decided to join a general purpose SBS 
list. I’m not sure that they’ll ever completely recover.  
         
        
        Amy 
         
        
         
         

________________________________

        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Jason Jones
        Sent: Thursday, January 11, 2007 5:47 AM
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        
        Wish I had never asked now...sometimes, some of you guys really don't 
make it easy for new people to try express their views and pose questions for 
comment without being slapped down. One minute I am being labelled as an 
"idiot" for my comments/views, the next minute someone else who says the same 
thing as me is now right and not challenged. What gives?  
        
        I know many of you guys don't know me from Adam, but kinda unfair to 
just assume I know jack about ISA and secure network design just because I'm 
not "part of the club".
        
        
        Anyhow, thanks to Tim and Tom for seeming to share my disappointment 
with the decision made by the Exchange 2007 team...I think I need to try and 
find out how "official" their lack of support with 2k7 is going to be before I 
can continue recommending the least privilege model I have been using for 
Exchange 2003.

________________________________

        
        From: isapros-bounce@xxxxxxxxxxxxx 
[mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Jim Harrison
        Sent: 11 January 2007 04:30
        To: isapros@xxxxxxxxxxxxx
        Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
        ..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] <mailto:isapros-bounce@xxxxxxxxxxxxx%5d> 
<mailto:isapros-bounce@xxxxxxxxxxxxx%5d>   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] <mailto:isapros-bounce@xxxxxxxxxxxxx%5d> 
<mailto:isapros-bounce@xxxxxxxxxxxxx%5d>   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&rnum=2&hl=en#4db165c21599cf9b
 
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+isa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>
 
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&rnum=2&hl=en#4db165c21599cf9b>
   
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+isa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>
 
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&rnum=2&hl=en#4db165c21599cf9b>
  
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+isa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>
 
<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&rnum=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. 

        
        
         
        
          

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

         

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References:
- [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
  - From: Jason Jones
[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

Other related posts:
