Date: Tue, 23 May 2006 11:52:42 +0530
From: "Niranjan S Patil" <niranjan.patil@...il.com>
To: sanjaynaik@...e.org
Cc: cbrenton@...isbrenton.org, bugtraq@...urityfocus.com
Subject: Re: Checkpoint SYN DoS Vulnerability


Hi Sanjay,

I agree with others when they pointed out the cause as the smart
defense feature. In Checkpoint, the most of smart protection features
still continue to run until you disable the entire feature in the main
page of SmartDefense in the Dashboard config window.

These features override the rules and its their idea of obfuscating
the scan results.

I dont think its a problem with Nokia platform, you would get same
result with secureplatform or windows or linux.

You may call it a feature or a bug, but I guess checkpoint has over
loaded their product with these features on.

Regards,
Niranjan

On 17/05/06, sanjay naik <sanjaynaik@...mail.com> wrote:
> Hi Chris,
>
> I have tested this with a complete TCPdump on the checkpoint side and
> Tethereal on the scanner side. The scan used is NMAP TCP Connect scan, which
> actually does the full 3-way handshake. So, according to your response, the
> scan should have always succeeded.
> The scan does succeed sometimes and at other times we get bogus information
> from the firewall. If this was a feature, it should have consistently
> provided bogus information.
>
> SYNDefender is disabled on the firewalls. Also, the firewall performance
> starts degrading as we start getting these bogus results. The State Table
> definely gets affected due to this scan which is really a valid permitted
> scan with proper rules in place for the scanner. I have seen issues with ACK
> scans and invalid SYN scans, but this is a valid TCP connect scan that we
> are trying.
>
> Nokia's response is that even if SYNDefender is disabld, it still works in
> the background! Authorized Scanning is not allowed by Checkpoint firewall as
> that is a product limitation.
>
> Regards,
> Sanjay Naik
>
>
> ----Original Message Follows----
> From: Chris Brenton <cbrenton@...isbrenton.org>
> Reply-To: cbrenton@...isbrenton.org
> To: sanjaynaik@...e.org
> CC: bugtraq@...urityfocus.com
> Subject: Re: Checkpoint SYN DoS Vulnerability
> Date: Tue, 16 May 2006 16:14:09 -0400
>
> On Tue, 2006-05-16 at 11:09 -0400, sanjay naik wrote:
>  >
>  > When a scan is intiated from the Inside interface of Checkpoint firewall,
>  > the firewall responds with bogus information intermittently.
>
> Sounds like you are triggering the SYN flood protection. Typically the
> firewall will respond with a SYN/ACK to ensure the source is not just
> generating a SYN flood. If you close the handshake, the connection is
> passed through to the target host if it is permitted in the rules. If
> not, the connection is simply deleted from the state table and ignored.
>
> Not sure why you are calling this a DoS as it does not sound like
> regular connectivity is being effected. The exception would be if you
> generated enough bogus SYN packets to fill up the state table so legit
> connections could not get through. I seem to remember Lance posting info
> about that to this list 4-5 years ago.
>
>  > In both cases, the scans results were inconsistent. Both SYN and ACK
>  > scans had similar issues.
>
> IMHO this is a feature. I would certainly rather see a port scanner
> receiving bogus results rather than accurate info that would assist in a
> compromise. Make them work a bit harder and earn it. ;-)
>
> HTH,
> Chris
>
> _________________________________________________________________
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>


-- 
Regards,
Niranjan S Patil

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