Re: Using 0days as part of pen-test?

[David Howe <DaveHowe.Pentest () googlemail com>]

ArcSighter Elite wrote:
> Hi list.
> I'm rather new to responsible disclosure, so experts may found silly my
> question, but I've founded pretty interesting, so please keep reading.
>
> A few days ago, I've identified a vulnerability in some closed-source
> vendor's ftp server.
> Then, days later I was requested to do pen-test against a company. While
> I was information gathering, I've managed to identify that third-party
> ftp daemon in one of the company's external hosts.
> I wasn't pretty sure how to proceed in such a situation, but I've fal to
> the temptation and exploited the flaw. That led to a 20-mins entire
> network compromise, and of course proved that the network was vulnerable.
> After doing that, and thinking about what I've done; I wasn't that happy
> about my results.
> First, I got the issue of how to report this vulnerability to the
> company, without breaking the -intermediary- vendor contact and
> agreement; because the vulnerability exists and its exploitable as I've
> proved, but it wasn't general public knowledge the flaw is present.

  Do you have a remedial/workaround you can offer them? If so, all I can
suggest is that you document it purely as "vulnerable to undisclosed
attack <randomly chosen four digit number or embargoed CVE/CERT number>"
and add the workaround; if they query it, just say that you are
contractually obliged to not disclose the vulnerability, pending a
vendor response and patch rollout. It can help if you can imply (without
stating) that you are licensing undisclosed 0days (would that be a
-1day?) and hence that your service offers a "deeper" check than you
could get as a skilled amateur without "contacts" in the field.

> I know I've braked a lot of phases of any pen-test framework, but IMHO a
> blackhat will proceed exactly this way: they'll exploit the network
> through its weakest link, and is my task to protect the company from the
> blackhat, not from pen-testers (at least not the evil ones).

  The real question there though is that, modulo that 0day, could you
have compromised their network? or did you drop everything else and rush
in to expand your bridgehead?

> Secondly, the flaw provided me with enough information that otherwise
> will take me a lot longer to achieve; so I felt the audit process has
> been somehow compromised.

  Well, you should really eliminate any information you could not have
gotten some other way, then do a review of their security on that basis;
Really, the best *anyone* can do in a pentest is "without knowledge of
vulnerabilities not known in the art (undisclosed 0days) this network is
secure" and that is *always* true. For any network, however secure,
there could (and will be) some as yet undocumented vulnerability that
will render it a decorative bandaid not a security solution.

  Your dilemma really is that, on the basis of privileged information
not available to an average attacker, you *can* compromise their
network, and you (as a paid consultant) owe a duty of care to that
customer to block or reduce that exposure as best you can; note that you
can require (of your customer) that certain parts (or all) of the report
be treated under NDA (that is routine anyhow) and usually, you can
phrase the remedial action in a way as to make it hard to
reverse-engineer the original 0day from it (recommending a substitute
free ftp product if that is not a special case platform, even if only as
a temporary solution until the vendor "catches up")