[8326] in bugtraq
Re: Firewall-1 Security Advisory
daemon@ATHENA.MIT.EDU (Larry Pingree)
Wed Oct 28 14:47:30 1998
Date: Tue, 27 Oct 1998 15:13:29 -0800
Reply-To: Larry Pingree <larryp@secure-it.net>
From: Larry Pingree <larryp@SECURE-IT.NET>
X-To: Paul Sears <Paul_Sears@NACM.COM>
To: BUGTRAQ@NETSPACE.ORG
This is a multi-part message in MIME format.
------=_NextPart_000_0058_01BE01BC.5AF15F40
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Once you place the
Source "Any" Dest "Firewall" and service "Any" Action "Drop" rule into
place, ping should no longer work even if the "Accept ICMP" is checked under
the Policy Property settings, what this leads me to believe is that not all
ICMP is allowed by the default rule, which leads me to the
question.......What is the definition of "ICMP" in that default setting?
-----Original Message-----
From: Paul Sears <Paul_Sears@NACM.COM>
To: BUGTRAQ@NETSPACE.ORG <BUGTRAQ@NETSPACE.ORG>
Date: Monday, October 26, 1998 1:59 PM
Subject: Re: Firewall-1 Security Advisory
>Diligence Risks wrote:
>
>> Diligence Security Advisory
>>
>> Issue: Checkpoint's Firewall-1 has a "feature" that can allow an external
>> intruder to pass through the firewall and attack machines, unihibited, on
>> the protected side.
>>
>> Details: When Firewall-1 is installed there is an implicit rule: ANY
>> (Source), ANY (Destination), ANY (Service) and ACTION (drop). This means,
in
>> theory, that all IP based packets, whether incoming or outgoing should be
>> dropped. However, Firewall-1, out of the box, allows certain "core"
network
>> protocols through - these being RIP (UDP port 520), DNS (UDP and TCP port
>> 53) and all ICMP except Redirects. These are allowed through, from ANY
>> (source) to ANY (Destination), without being logged, before the rule base
is
>> referenced.
>>
>
>These are because the Firewall Properties are set to allow this protocols
>through. These settings are what as known as the Firewall-1 "Implicit
Rules".
>These properties have four settings, unchecked, which means disabled;
checked,
>and "First" which means the this is handled before it hits the ruleset;
checked
>and "Before Last" which means that this property is passed through the
ruleset
>but accepted just before the last rule, which is usually any-any-any-drop;
and
>checked and "Last" which means that this rule is automatically the last
rule in
>your ruleset. This is documented in the administration guide and CCSE
training
>classes also cover these.
>
>In FW-1 version 4.0 you can toggle the display of these implicit rules,
which
>makes them much easier to identify and understand how they affect your
>ruleset.. In previous versions, you had to keep track of them manually,
and
>they were much easier to forget about.
>
>The problem is not how these properties are controlled, IMHO, but instead
that
>they default to enabled and "First". In my opinion, it should follow the
>standard Checkpoint mantra of "Which is not explicitly allowed is denied."
They
>violate their own standards there. Still, this is documented, though you
have
>to wade through the manuals.
>
>Just a point, however, is that setting up firewall is not a trivial thing
and
>every FW-1 admin that I have dealt with is familiar with how these
properties
>work, if you are not familiar with the product, inside and out, how can you
be
>sure you are properly implementing the product when it has such a critical
role?
>
>>
>> Consequently, DNS cache poisoning aside, if an attacker has managed to
place
>> a trojan or another "backdoor" on a host on the protected side, through
>> whatever method, and set it listening on TCP or UDP port 53, they will be
>> able to access this host transparently, through the firewall. No logging
>> will take place. The firewall host itself is reachable by this method,
even
>> if a 'stealth' rule has been placed in the rule-base to protect it.
>>
>> During our lab tests we set an NT Server listening on TCP port 53 using
>> netcat and on connection spawned a command prompt (cmd.exe). On
telnetting
>> to this server, through the firewall, we were able to attack all other
>> machines on the "protected" side. We also installed the cDc's Back
Orifice
>> on a Windows 95 client listening on UDP port 53 and could access this
>> machine through the firewall. When listening on UDP 520 (RIP) the we
could
>> not access the 95 client, indicating that firewall-1 checks the validity
of
>> traffic sent over the RIP port.
>>
>> Versions tested: Firewall-1 v3.0b on NT server 4.0 with Service Pack 3
>>
>> Fix: From the Firewall-1 Security Policy Window choose Properties from
the
>> Policy Menu. Uncheck the "Accept Domain Name Queries (UDP)" and "Accept
>> Domain Name Download (TCP)". This will disable DNS which, of course, will
>> cause problems. In order to avoid this you will need to create a specific
>> rule in the rule base to allow these core protocols to function. The
exact
>> nature of this rule will vary depending on the configuration of DNS
within
>> your own network and the above steps should only be taken after
consulting
>> with in-house DNS administrators. Diligence accepts no responsibility for
>> any problems caused by the disabling of these default settings.
>>
>
>Instead of completely disabling these rules, I recommend the "enabled" but
>process it "Last" and have appropriate rules to authorize and log these
>services...
>
>>
>> For further information see: http://www.diligence.co.uk
>
>--
>Paul Sears
>Senior UNIX Systems Admin
>Nicholas | Applegate
>600 West Broadway, 33rd Floor
>San Diego, CA 92101
>(619) 652-5493 voice
>(619) 687-8136 fax
------=_NextPart_000_0058_01BE01BC.5AF15F40
Content-Type: application/x-pkcs7-signature;
name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="smime.p7s"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=
------=_NextPart_000_0058_01BE01BC.5AF15F40--
