Remote Desktop and reverse PuTTY tunnels.

From: Nigel Johnson (nigel5_at_dr-deviant.net)
Date: 02/28/04 

Date: Sat, 28 Feb 2004 13:35:23 -0000

Hello all.

I am haveing a PuTTY realted issue, that I was hoping someone could help
with.

A quick diagram...

       |
Corp | Internet Home
+---+ | +---+ +---+
| A +--+--+ B | | C |
+---+ | +---+ +---+
       |
+---+ |
| D | |
+---+ |

(A) - my desktop at work, behind a firewall I have no control over and that
does not allow SSH traffic IN, also sits behind an NAT providing switch.
(B) - My webserver that I have control over (running Linux)
(C) - My Home PC that I want to work at.
(D) - A.N.Other PC at work.

All the windows based PC's (A, C, and D) all run the exact same version of
XP fully service packed, and up to date microsoft wise.

I am connecting PuTTY from (A) to (B).
This connection sets up a reverse tunnel (B):2222 -> localhost:22
I can PuTTY from (C) -> (B):2222 and I get the expected Cygwin login on (A)
This connection maps (C):3399 -> localhost:3389 meaning RD on (A)
When I connect from C to localhost:3399, I get the remote password prompt...
I type in the correct username and password, it starts thinking about it,
but then it hangs and does not recover... the underlying PuTTY command
prompt also hangs.
I can connect (D) -> (A) and run the exact same port mapping (D):3399 ->
localhost:3389 and the connection works.
If I just change the IP address in this connection, and the port to
(B):2222, I get the same as if I were at home.. the hang.

The only difference is the reverse tunnel.

There are no traffic related issues with (A) -> (B) as I have had a tunnel
running for a couple months.

The fact I get a command prompt on (A) when connecting to (B) would indicate
I have correctly configured the RD tunnel... and the fact that it works
direct (D) -> (A) would confirm this.

Anyone know of any setting I might need to set on my initial Putty config?
or is there any traffic that comes back off (A) that I need to have access
to? Like FTP does... that doesn't work over PuTTY because you connect on
port 21, and the server allocates you a random port for the TX of data.

This solution will be put on a production server as an alternative to the
correct solution of opening up the SSH port on our server :) This does mean
that VNC cannot be used.

Any ideas???

Thanks
Nigel.

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