Home page logo
/

nmap-dev logo Nmap Development mailing list archives

Re: ncat usage
From: Dave Henderson <dhenderson () digital-pipe com>
Date: Fri, 11 May 2012 08:28:56 -0400

Good morning James. I agree that the browser opens up a new connection to transmit all the "embedded" document requests (e.g. css and graphics files), however, I disagree with your second paragraph below. As I described in my prior reply, after the first connection is established by the browser for the HTML, that connection never closes, so when the follow-up connection is made by the browser to obtain the graphic file, it sends it over the same two named pipes that are still attached to the original connection for the HTML because it was never disconnected. The problem lies in ncat not disconnecting each connection as I can clearly see this by ncat'ing the ncat web server - it just sits there with the connection open after all the data has been sent. Do you have any thoughts on how to close the connection by ncat after it has completed?

Also this project isn't dealing with multiple connections, so I'm not really worried about serving 2, 5, 100, or 1,000,000 users simultaneously. :)

Thanks,
Dave


On 05/11/2012 07:03 AM, James Rogers wrote:
OK, you can only use ncat to serve a single page at a time to one web
browser, using ncat on the command line like you are. Which means you
cannot embed any images from that same server in the page you are
serving.  Because every image is a separate connection.

The reason for this is that every connection in to ncat would need
it's own separate handles for each send and receive, but you just have
two handles, so everything you send goes into the stream for the first
client that connects and nothing is ever sent to the second
simultaneous connection.

This is why the image shows up in the middle of your first web page as
text.  If 5 clients connected simultaneously the first connection
would get 5 pages randomly mixed together.

There might be a way using nse scripting to make ncat work like a full
featured web server, but at that point I would recommend just using a
small web server like boa or lighthttp.

Thanks,
James

On Thu, May 10, 2012 at 7:53 PM, Dave Henderson
<dhenderson () digital-pipe com>  wrote:
Ok, I adjusted the script to output the verbatim information you've listed
below using the same graphic file (also provided below).  Afterwards, I
tried again in the browser, but it still just shows the raw contents of the
graphic file as part of the HTML.  As a result, I tried an ncat on the ncat
web server to see it's output, and as expected, I got the identical output
below.  What I did notice, and later verified as an issue with all requests,
is that the connection never closes.  As such, I think the original
connection to the web server transmitting the HTML never closes so any
output produced afterwards gets added right behind it as part of it (the
graphics file request).  This would also explain why the status bar never
shows a disconnect from the web server.  So... I changed the script once
again to put ncat inside the infinite 'while' loop (and remove the -k
parameter) so that it should basically serve the file and then stop running
- only this didn't correct the problem!  The connection still stays open
when I ncat, the ncat web server!  I've even tried doing an "echo -e '\x04'"
(EOT/EOF) after the HTML is transmitted to the server, but it doesn't cause
a disconnect either.  Thoughts?

Thanks,
Dave



On 05/10/2012 04:15 PM, James Rogers wrote:
I got it to work on my localhost.   Evidently you have to give a HOST
tag or something similar for some sort of virtual hosting on many
servers.

ncat -C localhost 80
GET /icons/folder.gif HTTP/1.0

HTTP/1.1 200 OK
Date: Thu, 10 May 2012 20:12:32 GMT
Server: Apache/2.2.17 (Ubuntu)
Last-Modified: Sat, 20 Nov 2004 20:16:24 GMT
ETag: "c6c1d-e1-3e9564c23b600"
Accept-Ranges: bytes
Content-Length: 225
Connection: close
Content-Type: image/gif

GIF89a  �����̙����f3333!�NThis art is in the public domain. Kevin
Hughes, kevinh () IE�qg<��N"4�IRaV�V���x��l<&����z�#,L��; ;

On Thu, May 10, 2012 at 3:44 PM, Dave Henderson
<dhenderson () digital-pipe com>    wrote:
I tried your suggestion below, but constantly get a 404 error when trying
to
get a graphic from a remote host even though I know the path and filename
are correct.  Any other thoughts?

Thanks,
Dave
_______________________________________________
Sent through the nmap-dev mailing list
http://cgi.insecure.org/mailman/listinfo/nmap-dev
Archived at http://seclists.org/nmap-dev/

  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]
AlienVault