Passwordless login via the GUI and ssh defaults

I use cloud services at CSC  (e.g. pouta.csc.fi), and they do not allow SSH login with a traditional username/password combo. When I want to make a bookmark in my file manager (Nemo oder Nautilus/Files), pointing to this location. I need to specify an RSA key file that is used for the login. On the command line, it looks as follows:

ssh -i ~/.ssh/encypted_rsa_key.pem cloud-user@pouta.csc.fi

Then the shell asks for the password to decrypt the encoded RSA key, which is stored in the encrypted_rsa_key.pem file. Bypassing the requirement to decode the password (and giving up some security), one can decrypt the RSA password ahead of time:

openssl rsa -in encrypted_rsa_key.pem -out decrypted_rsa.key

But in order to use the file manger (Nemo or Nautilus/Files) to mount pouta.csc.fi, you need to tell it that you do want to use a passwordless login, and the Nemo “Connect to server” dialog does not offer this possibility. Hence, you need to modify the SSH configuration. In order to do this, you create a file ~/.ssh/config with the following content:

Host pouta
IdentityFile ~/.ssh/decrypted_rsa.key

This tells SSH that you want to use the specified identity file, but ONLY for the host pouta.csc.fi. After that, you can fill out the Nemo “Connect to server” dialog (no need to fill in the password) and connect to pouta via the GUI. A similar situation arises when you use Cubbli for your work at the University of Helsinki. Cubbli is the Helsinki University-modified/managed version of Ubuntu. If you are at home and want to connect directly to your work computer from the Ubuntu file manager, you also need to modify the /home/user/.ssh/config file:

Host workpc_cubbli
HostName dx2-000-26112.pc.helsinki.fi
User your_UH_username
ProxyJump your_UH_username@markka.it.helsinki.fi

After that, you can mount your work computer’s user directory into your local filesystem:

ssh://workpc_cubbli

You should make your life easier by using ssh keys instead of typing in your password:

ssh-copy-id your_UH_username@markka.it.helsinki.fi

And similarly from markka.it.helsinki.fi to your work computer:

ssh-copy-id your_UH_username@dx2-000-26112.pc.helsinki.fi

The ssh-copy-id does not get rid of the necessity to type in your password for good. Every now and then, you need to type in your password again, because markka just turns around and asks somewhere else whether you are allowed to login. And then markka gets a “ticket” that is valid for a certain time, after which you need again to authenticate with your password.