forwardOut() fails with Connection refused error with some remote hosts

[agebrock]

forwardOut() fails with Connection refused error with some remote hosts

[mscdex]

@aberbegall i'd try adding ssh.shell() and then do ssh.forwardOut() inside the shell callback and see if that works.

[aberbegall]

@markelog I get the same issue with the same hosts if I use adit instead of tunnel-ssh.

[aberbegall]

I keep investigating the issue, so far what I found this error in the target host log file

Nov  6 19:09:14 (none) sshd[2680]: error: connect_to 127.0.0.1 port 5900: failed.

so sshd complains that it cannot connect to 5900 port, and I verified that the x11vnc process was not running and therefore the port 5900 was not open. That's ok but:

In the /etc/password I have specified the following for 'myuser'

myuser::503:503:service:/var/home/myuser:/bin/start_x11vnc.sh

For each successful ssh session of 'myuser' the start_x11vnc.sh script should be executed, but it is not executed when doing port forward with this module.

For some reason when I do the same port forward with plink it does work fine, the start_x11vnc.sh gets executed, the port 5900 is listening and the client can connect to it through the tunnel.

My question now, is why it should be different with ssh2? Should I try first to establish a ssh connection and then execute ForwardOut separately, to ensure the user script gets executed just before?

Any help would be very appreciated.

[aberbegall]

Hi @mscdex, perhaps you could help me here, I can also file an issue in the ssh2 if you prefer it.

[mscdex]

I'm afraid there's not much I can do if it's something server-side. Have you tried adding a statement at the top of your script that logs to a file when it's executed? That might help you narrow it down whether the script is not executing at all or just some line in the script is failing.

[aberbegall]

Thanks, that's indeed what I tried in the script start_x11vnc.sh

#! /bin/sh
touch /tmp/executed

but I only get the file created when using plink port forward.
Any ideas other ideas?

[mscdex]

No idea, maybe plink is starting an interactive shell in the background, which might cause the shell in /etc/password to be executed? For ssh in general, you can forward ports separately from interactive sessions, command executions, etc. So tunnel-ssh is probably doing just that, since there is usually no use in spinning up an interactive shell session for port forwarding.

[markelog]

Have you tried to create a tunnel directly with ssh i.e. without using Nodejs at all? Regards, Oleg

…

On 6 Nov 2017, at 19:13, Brian White ***@***.***> wrote: No idea, maybe plink is starting an interactive shell in the background, which might cause the shell in /etc/password to be executed? For ssh in general, you can forward ports separately from interactive sessions, command executions, etc. So tunnel-ssh is probably doing just that, since there is usually no use in spinning up an interactive shell session for port forwarding. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[aberbegall]

@markelog No I've never tried, I only tried with putty and plink windows clients so far

[aberbegall]

Is it possible to force an interactive session with ssh2 before the ForwardOut()?
I have never use the ssh2 module directly.

[aberbegall]

@mscdex @markelog thanks guys for the help, I will try that ssh.shell() and see if I manage to get the script executes and post some feedback here

[aberbegall]

ssh.shell() did the trick 👍 executing the ssh.forwarOut() on its callback function ensures that the script execution is triggered just before.
Thank you again :)

[agebrock]

Glad you found a solution for you problem.

…

On 8 November 2017 at 03:25, Agustin Berbegall ***@***.***> wrote: Closed #60 <#60>. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#60 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAL-p96Ydq3yaPh7CN4YUU4odsq3zfmKks5s0LyigaJpZM4QSYDc> .