RE: How secure is software X?
David,
One thing you have to keep in mind is that a lot of things are incredibly
variable when dealing with this subject. For instance, suppose you want to
ensure that the URI in a web server is not overflowable. So you test with
something like
GET /[AAAAAAAAA x 4096] HTTP/1.1
Host: foobar.com
Connection: close
This is all fine and well, unless at 8192 is where the overflow takes place,
or if I can stick as many characters as I want in, so long as I am using
HTTP 1.1 and not HTTP 0.9, or if I am using HTTP/1.1 and Host doesn't
contain a 36 backslashes, et cetera.
This is generally why fuzzing is mostly inconclusive because it often misses
a lot of conditions and you have essentially assured nothing. Without
in-depth analysis of each software package you are basically pushing snake
oil. There are just far too many variables to really standardize such a
thing.
Best Regards,
Justin Ferguson
Reverse Engineer
NNSA IARC
702.942.2539
"It is a capital mistake to theorize before one has data. Insensibly one
begins to twist facts to suit theories, instead of theories to suit facts."
-- Sir Arthur Conan Doyle
> -----Original Message-----
> From: Adam Shostack [mailto:adam@xxxxxxxxxxxx]
> Sent: Friday, May 12, 2006 11:35 AM
> To: David Litchfield
> Cc: bugtraq@xxxxxxxxxxxxxxxxx;
> full-disclosure@xxxxxxxxxxxxxxxxx;
> ntbugtraq@xxxxxxxxxxxxxxxxxxxxxx; dbsec@xxxxxxxxxxxxx
> Subject: Re: How secure is software X?
>
>
> Hi David,
>
> Very briefly because I'm swamped today: Please consider
> bringing some of this to Metricon
> (https://securitymetrics.org/content/Wiki.jsp?page=Welcome)
>
> Also there's a project of US DHS/NIST and probably others
> called SAMATE Software Assurance Metrics and Tool Evaluation
> http://samate.nist.gov/index.php/Main_Page
>
> which might be of interest.
>
> Adam
>
> On Fri, May 12, 2006 at 02:59:17AM +0100, David Litchfield wrote:
> | How secure is software X?
> |
> | At least as secure as Vulnerability Assessment Assurance
> Level P; or Q
> | or
> | R. Well, that's what I think we should be able to say. What
> we need is an
> | open standard, that has been agreed upon by recognized
> experts, against
> | which the absence of software security vulnerability can be
> measured -
> | something which improves upon the failings of the Common
> Criteria. Let's
> | choose web server software as an example. When looking for
> flaws in a new
> | piece of web server software there are a bunch of well
> known checks that
> | one would throw at it first. Try directory traversal
> attacks and the
> | several variations. Try overflowing the request method, the
> URI, the query
> | string, the host header field and so on. Try cross site
> scripting attacks
> | in server error pages and file not found messages. As I
> said, there's a
> | bunch of checks and I've mentioned but a few. If these were
> all written
> | down and labelled with as a "standard" then one could say
> that web server
> | software X is at least as secure as the standard -
> providing of course the
> | server stands up.
> |
> | For products that are based upon RFCs it would be trivial
> to write a
> | simple
> | criteria that tests every aspect of the software as per the
> RFCs. This
> | would be called Vulnerability Assessment Assurance Level:
> Protocol. If a
> | bit of software was accredited at VAAL:Protocol then it
> would given a
> | level of assurance that it at least stood up to those attacks.
> |
> | Not all products are RFC compliant however. Sticking with
> web servers,
> | one
> | bit of software might have a bespoke request method of
> "FOOBAR". This opens
> | up a whole new attack surface that's not covered by the
> VAAL:Protocol
> | standard. There are two aspects to this. Anyone with a
> firewall capable of
> | blocking non-RFC compliant requests could configure it to
> do so - thus
> | closing off the attack surface - from the outside at least.
> As far as the
> | standards go however - you'd have to introduce criteria to
> cover that
> | specific functionality. And what about different
> application environments
> | running on top of the web server? And what about more
> complex products such
> | as database servers? I suppose at a minimum for DB software
> you could at
> | least have a standard that simply checks if the server
> falls to a long
> | username or password buffer overflow attempt and then fuzz
> SQL-92 language
> | elements. It certainly makes standardization much more
> difficult but I
> | think by no means impossible.
> |
> | Clearly, what is _easy_ is writing and agreeing upon a VAAL:Protocol
> | standard for many different types of servers. You could
> then be assured
> | that any server that passes is at least as secure as
> VAAL:Protocol and for
> | those looking for more "comfort" then they can at least
> block non-RFC
> | compliant traffic.
> |
> | Having had a chat with Steve Christey about this earlier
> today I know
> | there
> | are other people thinking along the same lines and I bet
> there are more
> | projects out there being worked on that are attempting to
> achieve the same
> | thing. If anyone is currently working on this stuff or
> would like to get
> | involved in thrashing out some ideas then please mail me -
> I'd love to hear
> | from you.
> |
> | Cheers,
> | David Litchfield
> | http://www.databasesecurity.com/
> | http://www.ngssoftware.com/
>