There is a POC shell program that uses XML-RPC called Monkey shell
(http://www.securiteam.com/tools/6L00F0KBFE.html). It looks like it
might require a re-code to be fully used as a pen-test tool. But it
something to look at. -
You can try HTTPTunnel as well.
httptunnel creates a bidirectional virtual data connection tunnelled in
HTTP requests. The HTTP requests can be sent via an HTTP proxy if so
desired.
This can be useful for users behind restrictive firewalls. If WWW access
is allowed through a HTTP proxy, it's possible to use httptunnel and,
say, telnet or PPP to connect to a computer outside the firewall.
http://www.nocrew.org/software/httptunnel.html
-Todd
-----Original Message-----
From: Joachim Schipper [mailto:j.schipper@math.uu.nl]
Sent: Sunday, April 17, 2005 10:13 AM
To: pen-test@securityfocus.com
Subject: Re: Netcat through Squid HTTP Proxy
On Fri, Apr 15, 2005 at 10:40:31AM -0400, Rod S wrote:
Hello,
I have a squid proxy server running, caching and filtering
web access.
User workstations on my network are only allowed http
access through
this proxy server. The firewall (Cisco PIX) will not let
them connect
outbound to any ports.
I've done some testing and was successful in running netcat
to connect
to a remote server listening with netcat on port 80 and get
a command
prompt for an internal machine (which is allowed to connect to any
outgoing ports) on that remote server. I'm wondering if
it's possible
for netcat to connect through our proxy server to a remote
machine and
send a cmd.exe shell in the same way? Any tips on
preventing this or
any other information you care to share is appreciated.
Thanks!
Rod
Dear Rod,
if I understand correctly, you can get a shell on a remote
machine and want to allow a remote machine to get a shell on
a local host. This can be achieved quite easily - search for
'reverse shell'. One example which looks nice is rrs (*nix
only) - see freshmeat.net. This one cannot do HTTP proxying,
though, so it should be augmented or wrapped in something that can.
The Hacker's Choice (www.thc.org) has just run an article on
this, including an example in Perl. If you desire something
more Windows-specific, you may want to ask Google, or any
shades-of-grey-hat site you can find. ;-)
However, simply, yes, this is possible. Quite a few of these
kinds of reverse shells rely on HTTP CONNECT, so limiting
that may help - but there are some seriously scary things out
there, including reverse shells that communicate over DNS or
ICMP (pings etc).
A good I(P|D)S may help a little. Locking down the network
further may help. However, it is almost impossible to keep a
smart attacker in - make sure to keep him out.
Joachim
