From: "Coaxial Karma" <c_karma@hotmail.com>
To: news@technotronic.com
Subject: IP tunnelling through SSL proxy
Date: Thu, 23 Dec 1999 10:34:02 PST
Mime-Version: 1.0

             -[ Tunnelling through an SSL Proxy ]-

-[ Introduction ]-

I know this may be known stuff, but since I haven't seen a lot of
released  tools to implement this concept (through an SSL Proxy),
I've decided to write something about it.

Here is what you'll need in order to create your tunnel:

1) Two linux boxes with root privileges - one on each side of the firewall

2) pppd-2.2 or greater - already installed on both linux boxes
   (it is recommended to use the same version on both linux boxes)

3) ipfwadm-2.3.0 or greater - already installed on both linux boxes

4) ppptcp-ssl.tar.gz (207.236.226.123/ppptcp-ssl.tar.gz)

Futhermore, you must have the following options turned ON in your
kernel:
	- Network firewalls
	- Forwarding/gatewaying
	- IP: Firewalling
	- Masquerading

And make sure IP forwarding is turned ON (not only in your kernel!)

The following has been tested with:
	- linux kernel 2.0.29/2.0.35/2.0.37
	- pppd 2.2.0/2.3.7
	- ipfwadm 2.3.0

-[ Installation ]-

On both linux boxes, do the following:

1) cd /usr/local/src; tar zxvf ppptcp-ssl.tar.gz
2) cd ppptcp-0.6; make

-[ Configuring the tunnel ]-

Let's assume the following configuration:

Linux #1 IP:		10.8.20.50 (inside the corporate network)
Linux #2 IP:		154.5.21.77 (outside the corporate network)
Proxy IP:		10.8.18.254 (port 8080)
Your default route:	10.8.20.1

1) Start a ppptcp server on Linux #2 listening on port 443:
	ppptcp 443 -- silent 192.168.1.1:192.168.1.2 proxyarp &

2) Configure ipfwadm on Linux #2 to masquerade for Linux #1:
	ipfwadm -F -a accept -S 192.168.1.2/32 -m

3) Delete default route on Linux #1:
	route del default

4) Add a route to your proxy on Linux #1:
	route add -host 10.8.18.254 gw 10.8.20.1

5) Start a ppptcp client on Linux #1 (also support authentication):
	ppptcp 154.5.21.77 443 10.8.18.254 8080 &

6) Add a default route on Linux #1:
	route add default gw 192.168.1.1

7) You're set!

Once the tunnel is established, you could also use Linux #1 as a
router for friends in your corporate network.  They could then access
the Internet without any restrictions.  In order to do so, you need
to:

1) Add a masquerading rule to Linux #1 for your friends:
	ipfwadm -F -a accept -S 10.8.20.0/24 -m

2) Delete default route on machines that want to bypass firewall:
	route delete 0.0.0.0 (on Win95/98/NT)
	route del default (on UNIX)

3) Add a default route on machines that want to bypass firewall:
	route add 0.0.0.0 MASK 0.0.0.0 10.8.20.50 (on Win95/98/NT)
	route add default gw 10.8.20.50 (on UNIX)

-[ Conclusion ]-

By default, ppptcp doesn't encrypt the traffic.  If you want it to
encrypt the traffic, read the INSTALL file provided with ppptcp ;-)

It may also be interesting to note that making internal machines
reachable to Linux #2 is also trivial once the tunnel has been
established.  Therefore, this makes for an interesting backdoor
to internal network.

have phun!

ck

-[ Credits ]-

1) encode_base64() function has been excerpt from httptunnel 2.11
   from Lars Brinkhoff.

2) ppptcp-0.6 from Sam Lantinga has been slightly modified to
   support SSL proxy and proxy authentication.

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com