Re: [isapros] Re: ISA, Exchange 2007 and Perimeter Networkswhats gets me is that there is "stuff all" documentation i have been able to find on CAS scenario's from the exchange team. other than "oh please put it in the lan, not supported in the dmz". Time to clear some stuff up i think. ----- Original Message ----- From: Thomas W Shinder To: isapros@xxxxxxxxxxxxx Sent: Saturday, January 13, 2007 4:10 AM Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks Jason, Excellent idea. Makes sense to put the Internet facing CAS in a separate zone from the non-Internet facing CAS. I don't see any problems putting the auth-access DMZ addresses in the site, and they probably already are :) Thomas W Shinder, M.D. Site: www.isaserver.org Blog: http://blogs.isaserver.org/shinder/ Book: http://tinyurl.com/3xqb7 MVP -- Microsoft Firewalls (ISA) ---------------------------------------------------------------------------- From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Jason Jones Sent: Friday, January 12, 2007 5:53 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 ---------------------------------------------------------------------------- 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 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> 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> -------------------------------------------------------------------------- From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] <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> 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&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&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&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. All mail to and from this domain is GFI-scanned.