[stunnel-users] stunnel used as jump host for SFTP

Schultz, Cecilia Schultz_Cecilia at rsccd.edu
Wed Jun 20 17:01:25 CEST 2018

Thank you very much for the suggestion Jose.

From: Josealf.rm <josealf at rocketmail.com>
Sent: Tuesday, June 19, 2018 5:22 PM
To: Schultz, Cecilia <Schultz_Cecilia at rsccd.edu>
Cc: stunnel-users at stunnel.org
Subject: Re: [stunnel-users] stunnel used as jump host for SFTP

Hi Cecilia,

I don’t Think stunnel is the right tool for This job. If your target server R is outside your local net and has a limit on the IPs that can connect to it, you can configure your firewall to do NAT ( network address translation ). You just need to use the same outgoing public IP used by S for your other clients C1, C2, C3 when they connect to R. You can do NAT just for outgoing connections to R on port 22.
Jose Alfredo Diaz

On Jun 19, 2018, at 1:12 PM, Schultz, Cecilia <Schultz_Cecilia at rsccd.edu<mailto:Schultz_Cecilia at rsccd.edu>> wrote:

I am trying to test stunnel to see if it can provide the functionality we need. We are a Windows shop.
What we need is for multiple client machines (I call these C1, C2, C3) to connect to our server (S).
Server S will connect to a remote SFTP server (port 22). I call the remote SFTP server “R”.
C1, C2, C3 and S are all inside our firewall.
Currently S can connect and send files to R using SFTP (port 22).
The problem is that R does not accept a range of IP addresses, and has a limit on the number of IP addresses they can accept.

So, what I need is for C1, C2, C3 to be able to connect to server R using S as a jump host.
From R’s perspective, it should be like the connection is coming from S.

Question 1: can stunnel be used to accomplish this?

Question 2: I have installed stunnel in a test server (“stunnel –install” actually from the bin folder), and configured the conf like this:


I tried to use Winscp SFTP client to test a connection, but it times out.
I then checked S, and I don’t see anything listening on port 22. I did “netstat –a” and I don’t see anything listening on port 22.

Was something wrong in the “stunnel –install” command? Shouldn’t it be listening on port 22?
Also, I uncommented the entry for log, but I don’t see any log file in the stunnel folder/subfolders

; Debugging stuff (may be useful for troubleshooting)
debug = info
output = stunnel.log

Thanks for your help,

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