Re: [NSE] Check for CVE-2011-1720 - Postfix SMTP Cyrus SASL memory corruption

[Djalal Harouni <tixxdz () opendz org>]

On 2011-05-16 19:17:41 -0700, Fyodor wrote:
> On Thu, May 12, 2011 at 06:33:50PM +0100, Djalal Harouni wrote:
> > Attached is just another clean version,
>
> Thanks Djalal.  This is a nice script for an important vulnerability!
> Regarding this line:
>
> > categories = {"dos", "exploit", "intrusive", "vuln"}
>
> The "intrusive" and "vuln" categories seem right on, but should this
> script be in "dos" and "exploit"?  The question is whether the script
> itself can be used to perform a DoS (intentionally or not) and whether
> the script itself can be used to exploit the bug.  I don't think we
> should use these categories if the reasoning is just that the
> underlying vulnerability could be used to perform a DoS or exploit.
> If the script can be used to perform a DoS or exploit, it should
> probably be documented in the description.  Maybe these are just there
> because you used smb-check-vulns as a template?  That one actually
> does DoS services (if you use the right option) and does include an
> exploit feature.
Right, I'll remove these two categories, since the script will just
segfault the Postfix smtpd child and not the master.

> Also, I have mixed feelings about making this a smtp-check-vulns
> script rather than being specific to the vulnerability it detects).
> Do you already have other bugs you plan to add to this script?  Do
> they benefit from being combined within this script rather than
> separate?  I suppose you could probably reuse some of the code, but
> that could be done by sharing an smtp library as well.
We should definitively write an smtp library, but currently it's not our
priority (perhaps when we have another smtp script).

> Admittedly your script follows the pattern of the well-loved
> smb-check-vulns script.  But that one does at least check for multiple
> vulnerabilities.  And, frankly, it might make more sense for that one
> to be split up too.  It is a strange mix of checking for several
> vulnerabilities, checking for the Conficker malware, exploiting a DoS
> bug, and exploiting an SMBv2 vulnerability.
Yes I used the smb-check-vulns as a template, but now with your
arguments and after a discussion with Henri this morning, spliting the
code that can fit in different NSE script categories seems more logical.

This way we take advantage of the boolean operator.
e.g: --script="smb* and intrusive and not dos" or something similar.

> If you don't have more vulns in mind for this script, maybe it would
> be best to name it after the Postfix Cyrus SASL vulnerability it
> detects.  Then if we find a later SMTP vulnerability and we believe it
> makes sense to combine detection into one script, we could do so then?
> Or if we decide they would be best structured as different scripts
> (from a user interface perspective), we could move the shared code to
> a library.
There are the exim vulnerabilities (one of them is too old).

If we decide to change the name, what do you think about:
smtp-cve-2011-1720.nse
smtp-postfix-cve-2011-1720.nse


> Or maybe some folks think having a single vuln check script per
> protocol might be a better model?
>
> I do think that if we were doing local patch checks, it would probably
> make more sense to have just one script for each platform which checks
> if all the patches are installed than to do the Nessus/OpenVAS model
> of one-script-per-issued-patch.
Yes, one script can do this (use the package manager or search for
patterns ...)

-- 
tixxdz
http://opendz.org
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