Remote Desktop and reverse PuTTY tunnels.

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Hello all.

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

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???


Re: Remote Desktop and reverse PuTTY tunnels.

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Do you have any access to a Windows debugger?  If you could attach a
debugger to the hanging PuTTY process and send us the call stack, we
might be able to work out precisely where it has hung.
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PuTTY should never hang or crash, so if it does that's a bug that we
need to fix.


Re: Remote Desktop and reverse PuTTY tunnels. - rdchat.txt (0/1)

Can you suggest a light debugger,  I cannot install Visual Studio.

Also attached is a tcp dump of the traffic after mapping back a port
R3399 -> L3389 still with the no login, and hang like affect.

I am assuming in the trace, that 4454 is the originating connection as
all the traffic goes to port 22 on (B). ther is no mention of port
3389 tho.


On 01 Mar 2004 11:55:03 +0000, Owen Dunn

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Re: Remote Desktop and reverse PuTTY tunnels. - rdchat.txt (0/1)

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I'm not sure about `light', but Microsoft's WinDbg appears to be
freely downloadable from:

I don't have easy access to Windows at the moment, so I can't tell you
if this does what's needed.


Re: Remote Desktop and reverse PuTTY tunnels. - rdchat.txt (0/1)

I hope I did it right, When connecting to the mstsc.exe when it locks,
its in ntdll, whne I connecto to the PuTTY session that locked, its in
the same place....

(a44.fa8): Break instruction exception - code 80000003 (first chance)
eax=7ffdf000 ebx=00000001 ecx=00000002 edx=00000003 esi=00000004
eip=77f75a58 esp=010bffcc ebp=010bfff4 iopl=0         nv up ei pl zr
na po nc
cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000
77f75a58 cc               int     3

Don't think its a PuTTY problem at this end as the connection hangs
whether I use it or not.

I'll attempt to run it on the PC thats service the connection, but the
only way in is RD at the moment :)


On 02 Mar 2004 10:16:02 +0000, Owen Dunn

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Re: Remote Desktop and reverse PuTTY tunnels. - rdchat.txt (0/1)

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Is that all it gave you?  I would expect to see rather more of the
stack than that.


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