Search code examples
macosubuntuunixsshportforwarding

Remote port forwarded SSH considered as an invalid user accessing from 127.0.0.1

I am trying to connect to a server which already established a remote ssh connection to my client by running the following on server:

ssh -R :8080:localhost:22 -p 22 clientUser@clientIP

when I try to connect to the server by running the following on the client side:

ssh -p 8080 localhost

I am getting asked for a password as:

clientUser@localhost's password:

both connections should be able to establish via public key (the remote port forwarding ssh already can do this with no problem.)

furthermore in /var/log/auth.log on server shows:

Invalid user clientUser from 127.0.0.1 port 39768

which suggests that the server sees this as kind of a loopback connection?

the client OS is MacOSX Mojave and the server side is Ubuntu 18.04 LTS.

If I try to remote forward the connection from the client to any port other than 22 on the server I am getting

ssh_exchange_identification: Connection closed by remote host

I appreciate your kind help!

Solution

  • thanks to Chris in comments.

    the problem was I had to 

    ssh -p 8080 serverUser@localhost

    by default 

    ssh -p 8080 localhost

    is the same as 

    ssh -p 8080 ${USER}@localhost

    and uses the current user from the environment. This will results in an invalid user message by the server.