Re: Microsoft IPSec via group policy

[Herb Martin <HerbM () LearnQuick Com>]

Jesse Rink wrote:
> Perhaps I need to re-think this a bit.
>
> My original intention for enabling IPsec was the prevent users from sniffing
> Kerberos hashes.  I was under the assumption based on the communication I
> had with several security "experts" from a couple consulting companies that
> IPsec could accomplish this.
>
> What I'm here from Rodrigo and Scott, is that IPsec cannot encrypt the
> packets containing Kerberos hashes that are sent over the network between
> the XP client and domain controller.  Is this correct?

No it's not correct EXACTLY but it would be difficult to get it to do
that (not impossible.)

IPSec requires one of three authentication methods, i.e., Kerberos,
Certificates, or Pre-Shared Secret (think common password) before
IPSec (encryption) is begun.

Kerberos is the default (for Microsoft IPSec) and is thus exempted
from the default policies to avoid a cart before the horse issue
(you can't do IPSec without Kerberos but the IPsec won't work until
the Kerberos authenticates).

Since in a domain environment most people use the Default IPSec
policies (the ones already present in the GPOs) this would mean
"no Kerberos encryption" by IPSec.

However you could (at least in theory) build a CUSTOM Policy (without
to much trouble really so that caveat of "in theory" is much scarier
than it probably deserves) which use Certificates to authenticate for
the purpose of encrypting Kerberos too.

The main issue here would be the distribution of IPSec Certificates and
perhaps the Trust Certificates securely (if you don't trust what you
already have to be secure.)

Kerberos is already largely secure so this is likely not much point
here, e.g,   No passwords are exchanged during a password authentication 
and the "tickets" have limited lifetime (during which they can 
theoretically be decrypted and played back.)


> I am not so concerned with encrypting traffic between the clients and
> members servers or emails servers as I am with encrypting traffic that
> contains the Kerberos hashes which users can sniff and then hack offline.

There are much easier attacks -- like finding Passwords being sent 
through that email by naive users.

--
Herb

> Comments welcome. .. Paul?  Rodrigo?  Scott?
>
> Thanks.
> J
>
>
> -----Original Message-----
> From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On
> Behalf Of Ramsdell, Scott
> Sent: Thursday, February 07, 2008 8:36 AM
> To: Jesse Rink; Paul J. Brickett
> Cc: security-basics () securityfocus com;
> security-basics-return-47647 () securityfocus com
> Subject: RE: Microsoft IPSec via group policy
>
> JR,
>
> Requiring ipsec between a client and a DC via GPO is problematic.
>
> You'll have much more success allowing the initial auth to the domain
> via Kerberos, then using ipsec to secure communication from the client
> machine to the file/email servers.
>
> From Microsoft: Currently, we do not support the use of IPSec to encrypt
> network traffic from a domain client or member server to a domain
> controller when you apply the IPSec policies by using Group Policy or
> when you use the Kerberos version 5 protocol authentication method.
>
> http://support.microsoft.com/kb/q254949/ 
>
> You're putting the cart before the horse, so to speak, by requiring
> ipsec communication before your client machines can auth and read the
> GPO that requires the ipsec.
>
>
> Kind Regards,
>
> Scott Ramsdell
> CISSP CCNA MSCE
>
>
> -----Original Message-----
> From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
> On Behalf Of Jesse Rink
> Sent: Wednesday, February 06, 2008 8:04 AM
> To: 'Paul J. Brickett'
> Cc: security-basics () securityfocus com;
> security-basics-return-47647 () securityfocus com
> Subject: RE: Microsoft IPSec via group policy
>
> Hello.
> Sorry for the delayed response.  For some reason when I post on this
> list,
> my posts sometimes don't' show up for 16-30 hours.  Not quite sure why.
>
> What I'm attempting is to encrypt network traffic between my clients and
> my
> domain controllers and clients and my member servers.
>
> I have tried setting IPSec up in group policy however I'm running into
> some
> strange issues.  What I've done to set this up for testing is this...
>
> 1. In the Domain Controllers OU and GPO, I set the IP Sec policy for
> Server
> (request security) - Assigned.
>
> 2. In the test PC OU and GPO, I set the IP Sec policy for Client
> (respond
> only) - Assigned.
>
> At this time, I think I should be good to go.  I go to the XP client and
> do
> a gpupdate /force and reboot the computer.  Now, here's what's odd.
> According to documentation I've read, I should be able to tell the IP
> Sec
> policy applied to the client in the following ways:
>
> 1. I should be able to do an RSOP.msc from Start|Run on the XP client
> and
> see the IP Sec policy.  I try that, but nothing shows up.
>
> 2. I should be able to look at the Local Security Policy on the XP
> client
> and it should show that IP Sec policy has been applied from a GPO.  I
> try
> that, but nothing shows up.
>
> I am starting to wonder if the documentation I've read is WRONG about
> these
> things.  I have noticed this... If I look on the XP Client's registry,
> under
> HKLM\SOFTWARE\Policies\Microsoft\Windows\IPsec\GPTIPSECPolicy and under
> HKLM\SOFTWARE\Policies\Microsoft\Windows\IPsec\Policy\Cache, I "DO" find
> that these keys are created/updated after doing the gpupdate /force and
> rebooting, so it SEEMS like IPSec is getting applied?   But again,
> RSOP.msc
> and the Local Security Policy show NOTHING.  Why is this?
>
> Also, I am testing what happens if the IPSec policy on the client is
> unapplied.  This is very strange as well.  If after having applied the
> IP
> Sec policy via GPO to the XP Client, I remove it a short time later by
> going
> into the GPO for the PC OU, and changing Client (respond only) to
> Unassign,
> when I then go to the XP client and do a gpupdate /force and then
> reboot,
> the XP client can no longer contact the domain controller.  I can't even
> ping it, nor can the domain controller ping the client.   This doesn't
> make
> sense.  I am removing the IP Sec policy from the client "by the book" as
> far
> as I can tell by unassigning it first, and then making sure the new GPO
> is
> applied to the PC.  Any idea on this particular issue?
>
> I'm about ready to open up a case with Microsoft to figure this stuff
> out.
> Thanks for any help.
>
> JR
>
>
>  
> -----Original Message-----
> From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
> On
> Behalf Of Paul J. Brickett
> Sent: Tuesday, February 05, 2008 11:02 AM
> To: jesse-rink () wi rr com
> Cc: security-basics () securityfocus com;
> security-basics-return-47647 () securityfocus com
> Subject: Re: Microsoft IPSec via group policy
>
> What exactly are you trying to do? Providing detail to the group may 
> elicit more responses.
>
> I've deployed several IPSec GPOs- I generally have used IPSec GPOs to
> more 
> granularly block/allow access to specific ports/protocols. I find that 
> it's a more precise tool then Windows Firewall. I often find myself 
> comparing it to IPTables.
>
> -PJB
>
> On Mon, 4 Feb 2008, jesse-rink () wi rr com wrote:
>
> > Just curious if anyone on the list has implemented IPsec for Windows
> > 2003/XP via Group Policy?  I am testing this out and finding some
> strange
> > results that I'd like to bounce off someone who's done this before.
> > Anyone?
> >
> > JR
> >
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