List ports forwarded by myself from ssh?

Question

If I connect to a server like so:

JP_PORT=$(shuf -i 8895-9100 -n 1)
TB_PORT=$(shuf -i 6010-6200 -n 1)
ssh -Y -L ${JP_PORT}:127.0.0.1:${JP_PORT} -L ${TB_PORT}:127.0.0.1:${TB_PORT} <host>

Once connection is established, is there any terminal command that will return the list of ports I forwarded?

Solution 1

You can list via lsof

sudo lsof -i -n 

You may use grep to filter results

sudo lsof -i -n  | grep ssh

Solution 2

If it is enough to list only the forwarded connections that are actually used, and if your session is interactive (like in your case), you can use the ~# escape within the ssh session. Just type enter~#.

$ ssh -L1234:localhost:22 localhost
seb@localhost's password: 
Welcome to Ubuntu 18.04 LTS (GNU/Linux 4.15.0-23-generic x86_64)
$ ~#
The following connections are open:
  #2 client-session (t4 r0 i0/0 o0/0 fd 7/8 cc -1)
  #3 direct-tcpip: listening port 1234 for localhost port 22, connect from 127.0.0.1 port 37238 to 127.0.0.1 port 1234 (t4 r1 i0/0 o0/0 fd 10/10 cc -1)

This will also list forwardings that were added later within the session using escape commands, and thus are not appearing on the command line.

Try ~? for other useful commands inside the ssh session. See also the section on ESCAPE CHARACTERS in the ssh manual page.

Solution 3

There's a couple more ways to list ssh's connections/tunnels. Firstly one can use netstat (p show process name (sudo needed), ip - show IP connections):

sudo netstat -ap --ip | grep ssh

Secondly one can also use the socket stats command ss (p - show process name (sudo needed), e - extended socket info for userid, t - TCP connections):

sudo ss -pet | grep ssh

Note: Local (-L) ssh tunnels are not created on the server until the something on the client side has initiated a connection to the local port - only then will the tunnel be set up on the server side and be visible by these methods or any of the other answers.

Comments

[Austin]

Any way to list the ssh ports I forwarded without having sudo on the remote server?

[Panther]

You can try without sudo. You can try ps aux | grep ssh

[Sebastian Stark]

A few more charcaters, but no grep needed: lsof -a -c '/^ssh$/' -i -sTCP:LISTEN,ESTABLISHED

[muru]

Heads up: using fragment IDs with the Ubuntu manpages site is useless, since the IDs are generated using JS after the page loads.

[Sebastian Stark]

@muru and I was wondering what I'm doing wrong... Thanks for letting me know.

[Austin]

Thanks this is interesting to know about. Unfortunately for me it only lists #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cc -1) without any port information.

[Sebastian Stark]

@Austin as I wrote, it will only list the forwarding if it is in use. You can test it with telnet localhost port.

[Austin]

Telnet appears to not be installed on my server and I don't have sudo :/ ah well.

[Oleg Bolden]

Forwardings that were added later within the session using escape commands won't appear in the output of ~#. I've tested this for OpenSSH_6.

[Sebastian Stark]

@OlegBolden just tested this on 18.04: If I add a forwarding later and use it, it will be listed.