Re: Contributing to Nmap development

[David Fifield <david () bamsoftware com>]

On Sun, Sep 20, 2009 at 05:17:28PM +0600, Ravipriya Thushara wrote:
> Thanks lot for all for helping me. I'll give main priority in my project to
>  o [NSE] Add DNS based service discovery script.
>
> After that script is done I'll try to work on Zenmap development and
> some other Lua scripts with the time I have. even after my project,
> I'll contribute to Nmap development.
>
> Tomorrow I'll write the project proposal and I'll send a copy to here also.
> Then I have to begin coding. Still I'm trying to learn whats happening in
> Nmap and learn its basics in it's code and scripting.
>
> I'll be glad if you can send me some more details on
> o [NSE] Add DNS based service discovery script. and some places to
> read and learn about it. Also I like to know some more ideas on scripting.

First see my original sketch of an idea at
http://seclists.org/nmap-dev/2009/q3/0786.html. Then read the DNS-SD
spec at http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt,
especially section 9 that covers the "_service._dns-sd._udp.local"
probe.

For building and decoding the DNS packets you will use the dns module:
http://nmap.org/nsedoc/lib/dns.html.

This is how I picture the output of a first version of this script:

# nmap -F -sU --script=dns-sd 192.168.0.190

Starting Nmap 5.05BETA1 ( http://nmap.org ) at 2009-09-21 11:26 MDT
Interesting ports on 192.168.0.190:
Not shown: 98 open|filtered ports
PORT     STATE SERVICE
123/udp  open  ntp
5353/udp open  zeroconf
| dns-sd: _ssh._tcp.local _sftp-ssh._tcp.local
MAC Address: 00:16:CB:AE:D4:AC (Apple Computer)

Nmap done: 1 IP address (1 host up) scanned in 3.26 seconds

Producing this output should only take one probe and a few reads. When
the script can do this we can commit it and add additional functionality
such as follow-up probes to find out port numbers.

David Fifield

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