Re: [EXTERNAL] WAF Metrics

[Don Ankney via Dailydave <dailydave () lists aitelfoundation org>]

So far, this conversation focuses on how effectively WAFs block malicious HTTP requests. I'd argue that this is both a 
red herring and an abuse of WAF technology.  A WAF only protects the enterprise when it blocks a request that would 
trigger an actual bug. If there's no bug present, all that's really happening is that likely malicious requests are 
being logged at a much higher costs than if it were simply allowed to sit in the web logs. Being attacked constantly is 
a side-effect of being on the Internet. You should expect to be constantly scanned and probed. Ideally, action should 
only be necessary if an attack is actually practical, otherwise you're simply reacting to the background chatter of the 
Internet.

If there is a bug present and the WAF blocks the attempt, then it is a legitimate protective action has occurred. The 
WAF is simply a stopgap, however. If the bug is present, then the WAF will eventually be evaded allowing an attack to 
succeed. As a result, I'd argue that success metrics for a WAF are effectively twofold:

1) How clearly does it signal that there's an actual bug in the software behind it?
2) How much time can it provide for a fix to that software?

The problems you are protecting against aren't in the WAF or it's tuning -- it's in the underlying software. A WAF is 
simply a stopgap that buys time while code is corrected or vendors ship a patch. Relying on a WAF as anything more than 
a defense-in-depth mechanism is a losing proposition over time. Metrics need to reflect that.
________________________________
From: Chuck McAuley via Dailydave <dailydave () lists aitelfoundation org>
Sent: Tuesday, July 14, 2020 7:14 AM
To: John Lampe <jlampe () tenable com>; Rafal Los <Rafal () ishackingyou com>
Cc: dailydave () lists aitelfoundation org <dailydave () lists aitelfoundation org>
Subject: [Dailydave] Re: [EXTERNAL] WAF Metrics


This isn’t directly related to John’s observation below, but it got me motivated to further clarify some of the 
challenges involved in testing WAFs.



I’ve seen many implementations over the years that try to determine the decision making process of an IPS, WAF, or 
similar device by simply interrogating it from the client side only. The realities of test of measurement is that it 
requires the user to implement both a client and server side process of whatever it is you are testing to validate that 
not only was malicious content allowed or blocked, but that IF it was allowed, it was allowed through without a 
modification that would impact the intent of the vulnerability.



That’s a mouthful of a sentence. Let me make it briefer:

You can’t tell if the bad stuff got through unless you are wrapped around the bad stuff blocking thing.



This gets even harder when you are testing WAF’s. They very often interrupt the connection, marshal the request, then 
issue a new HTTP request to the server. This means that while your malicious  request might have altered headers, or 
Content-Transfer-Encoding changes the actual little nugget of maliciousness is left alone.



“Fine”, you say, “I’ll just examine the URL request, because I’m only interested in testing items that are impacted 
there.” And then CVE-2017-5638 comes along and you need to accommodate for deserialization vulnerabilities in other 
headers. The WAF catches it. But your current test implementation can’t.



And that’s an easy example.



You can have a chain like this:

Client POST multipart http2 -> proxy -> TLS 1_1 -> Internet -> IPS Performing TLS inspection -> Different handshake TLS 
1_0 -> WAF/LB -> http1.1 cleartext/chunked -> server.



I just came up with that off the top of my head, so please don’t challenge me on the technical limitations of said 
example :).



The point is that testing in isolation is very different from testing a deployed system under test and for each new 
technology deployed, the number of permutations increases dramatically. This list has discussed many times the merits 
and problems with “defense in depth” strategies, so I won’t belabor that point. Only to say “it’s hard to get an 
accurate read on if you are secure or not.” Lunchtime doubly so.



-chuck



From: John Lampe via Dailydave <dailydave () lists aitelfoundation org>
Reply-To: John Lampe <jlampe () tenable com>
Date: Monday, July 13, 2020 at 8:07 PM
To: Rafal Los <Rafal () ishackingyou com>
Cc: "dailydave () lists aitelfoundation org" <dailydave () lists aitelfoundation org>
Subject: [Dailydave] Re: [EXTERNAL] WAF Metrics



[EXTERNAL]

Yeah, I guess the way I would envision it going would be:



1) web app scanner sees XSS vuln on /path/to/foo.php

2) my integration ties that web app scan into a format to pass to WAF

3) WAF sets up anti-xss rules on /path/to/foo.php (we had to actually create a static mapping for this step)

4) measure how many hits the waf blocks to that endpoint for the XSS



John











On Mon, Jul 13, 2020 at 10:46 AM Rafal Los <Rafal () ishackingyou com<mailto:Rafal () ishackingyou com>> wrote:

*** CAUTION: This email was sent from an EXTERNAL source. Think before clicking links or opening attachments. ***



________________________________

John,

Can you expand on #2? How do you measure the number of attacks stifled?



_--
Rafal
_Mobile: (404) 606-6056
_Email: Rafal.Los@Seventy7.Consulting<mailto:Rafal.Los@Seventy7.Consulting>





From: John Lampe via Dailydave <dailydave () lists aitelfoundation org<mailto:dailydave () lists aitelfoundation org>>
Reply-To: John Lampe <jlampe () tenable com<mailto:jlampe () tenable com>>
Date: Saturday, July 11, 2020 at 9:52 PM
To: Dave Aitel <dave.aitel () gmail com<mailto:dave.aitel () gmail com>>
Cc: "dailydave () lists aitelfoundation org<mailto:dailydave () lists aitelfoundation org>" <dailydave () lists 
aitelfoundation org<mailto:dailydave () lists aitelfoundation org>>
Subject: [Dailydave] Re: [EXTERNAL] WAF Metrics



So, I recently did an integration for a company that took their web app scanner results and mapped those to existing 
WAF rules. I can think of 2 metrics based off that



1) How many real-world vulns have a corresponding check in the WAF? and

2) Once the WAF rules have been put in place to protect actually-vulnerable endpoints, how many attacks were actually 
stifled?



John





On Sat, Jul 11, 2020 at 12:51 PM Dave Aitel via Dailydave <dailydave () lists aitelfoundation org<mailto:dailydave () 
lists aitelfoundation org>> wrote:

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________________________________

So I'm making a video on metrics, of all things, and I wanted to post both this question 
<https://urldefense.com/v3/__https:/twitter.com/daveaitel/status/1281629327776522242?s=20__;!!I5pVk4LIGAfnvw!1DZZL1viGJTRH-H2akN1jntqUUjdEe6Oa7-HctTc9IePgQzC3DN13JryFgb8Id0i$>
 and the best answer so far to the list to see if anyone had any other ideas or followups.



-dave





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