15 Jul
2020
15 Jul
'20
11:09 a.m.
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(a)lists.aitelfoundation.org>
Sent: Tuesday, July 14, 2020 7:14 AM
To: John Lampe <jlampe(a)tenable.com>om>; Rafal Los <Rafal(a)ishackingyou.com>
Cc: dailydave(a)lists.aitelfoundation.org <dailydave(a)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(a)lists.aitelfoundation.org>
Reply-To: John Lampe <jlampe(a)tenable.com>
Date: Monday, July 13, 2020 at 8:07 PM
To: Rafal Los <Rafal(a)ishackingyou.com>
Cc: "dailydave(a)lists.aitelfoundation.org"
<dailydave(a)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:
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________________________________
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
[cid:image001.png@01D659C7.81D98AD0]
[cid:image002.png@01D659C7.81D98AD0]
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