Also Part of: Hardening Linux Servers

1. Make Public / Private Key Pair
2. Add Public Key to Server
3. Verify Passwordless Login Works
4. Disable Password Login on Server

ssh-keygen -t rsa

Go to .ssh under your home directory

cd ~/.ssh

Info: In case you don't have a “.ssh” directory, create it and set the permissions to 700

mkdir .ssh && sudo chmod 700 .ssh

Inside you should have a file called “authorized_keys”. If you do not, make it and set the permissions to 600

touch authorized_keys && sudo chmod 600 authorized_keys

Copy your public key from *.pub to authorized_keys. It should look something like this:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQDVtv5prVJ[.....]

ssh-copy-id user@remote-host

Important! Be 110% sure the passwordless login works, else you will lock yourself out.

Edit the file “sshd_config”

nano /etc/ssh/sshd_config

Update / Confirm the following 3 values:

PasswordAuthentication no
ChallengeResponseAuthentication no
UsePAM no

Restart the service with:

sudo systemctl restart sshd

sudo nano ~/.ssh/config

~/.ssh/config eg:

Host opportunity
    HostName 10.20.30.40
    User remoteUser
    IdentityFile ~/.ssh/privateKey

Connect with:

ssh opportunity