RE: Nmap Attack Scripting Language (NASL)

[Brandon Enright <bmenrigh () ucsd edu>]

I'm a fan of TCL/Expect and write a lot of very useful code in it.  I
don't think it is up to the Nmap/NASL job though.  I recently went about
writing a vulnerability checker for the "RealVNC Authentication Bypass"
security hole in Expect and found it's handling of binary data very
primitive.  TCL can't handle/match NULL characters in strings at all.  I
re-wrote it in Perl and handled the NULLs just fine.

The NASL language of choice has to be able to handle arbitrary binary
data including NULLs without any extra work.  It's totally feasible to
need to send binary data and expect binary data back -- TCL/Expect
really breaks down in this area.

The Nmap script framework should (and probably will) have some sort of
send/expect API similar to TCL/Expect.  There may also be a need to do
asynchronous I/O and other non-blocking I/O tasks.  Nmap already has
PCRE and doesn't need the bloat of another RE engine.

I've looked into LUA and have been pleasantly surprised.  It compiles in
5 seconds and is meant to be integrated into another project rather than
be standalone.  It also sounds like LUA threads really well and is
extremely portable.  LUA should be the fastest to implement and cause
the fewest integration headaches.

I like TCL just fine but would rather see LUA or Perl or Ruby over TCL.

Brandon

-- 
Brandon Enright
Network Security Analyst
UCSD ACS/Network Operations
bmenrigh () ucsd edu


On Tue, 2006-05-23 at 11:36 +0530, Arun Vishwanathan wrote:
> Fyodor,
>
> Why can't we use TCL as the scripting language?
>
> I say TCL because of the following reasons
> - TCL is easily extensible by writing custom commands in C and exporting
> them as TCL functions. 
> - TCL provides a very decent syntax and provides all common programming
> constructs in addition to in-built commands for string handling/regex
> etc.  
> - TCL is used by most networking companies and hence would be easy for
> companies to integrate NMAP commands into their existing frameworks thus
> making nmap an integral part of their test infrastructure (like we do at
> Nevis Networks :)). 
> - TCL integrates easily with expect and which can be used to automate
> remote scanning. You could potentially launch nmaps from multiple hosts
> all controlled from a single controller script written using
> send/expect. This may make sense for scanning larger networks where an
> admin can logically divide his network and scan parallely. 
>
> My 2 cents. Hope the above makes sense. 
>
> Regards,
> Arun
>
> -----Original Message-----
> From: nmap-dev-bounces () insecure org
> [mailto:nmap-dev-bounces () insecure org] On Behalf Of Fyodor
> Sent: Tuesday, May 23, 2006 6:50 AM
> To: nmap-dev () insecure org
> Subject: Nmap Attack Scripting Language (NASL)
>
> One of the Google SoC projects that I'm most excited about is adding a
> scripting engine to Nmap.  Don't worry Renaud, we won't really call it
> NASL :).  And this doesn't mean Nmap is becoming a vulnerability
> scanner.  Scripts can be used for all sorts of things.  For example,
> KX's recent suggestion of looking up AS numbers and whois data.  Or
> you could write a custom script to query your own proprietary
> applications on your network.  Or vulnerability detection.  Or maybe
> check for open proxies.  There are tons of options.
>
> So I just wrote up a requirements doc for the project:
>
> http://www.insecure.org/nmap/SoC/Scripting.html
>
> Boy, SoC is a great program but it sure keeps me writing a lot of long
> text files :).  The good news is that the final student selection
> should be announced within the next couple days and then we'll move
> toward writing code.  But doing the initial design properly is
> obviously critical.  So do reply if you have suggestions.
>
> For what it is worth, we're currently looking at LUA as the embedded
> scripting language of choice.  Anyone have experience in this area?
>
> Cheers,
> -F




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