Installing the SSH Audit tool:

sudo snap install ssh-audit


pip3 install ssh-audit


docker pull positronsecurity/ssh-audit

Auditing SSH hosts:

ssh-audit -T servers.txt

List and run an audit against a host:

ssh-audit -L
ssh-audit -P 'Hardened Ubuntu Server 20.04 LTS (version 1)'

Hardening Ubuntu 20.04 SSH:

rm /etc/ssh/ssh_host_*
ssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N ""
ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N
awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/
mv /etc/ssh/ /etc/ssh/moduli
sed -i 's/^\#HostKey \/etc\/ssh\/ssh_host_\(rsa\|ed25519\)_key$/HostKey \/etc\/ssh\/ssh_host_\1_key/g' /etc/ssh/sshd_config
echo -e "\n# Restrict key exchange, cipher, and MAC algorithms, as per\n# hardening guide.\nKexAlgorithms curve25519-sha256,[email protected],diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\nCiphers [email protected],[email protected],[email protected],aes256-ctr,aes192-ctr,aes128-ctr\nMACs [email protected],[email protected],[email protected]\nHostKeyAlgorithms ssh-ed25519,[email protected],[email protected],[email protected],rsa-sha2-256,rsa-sha2-512,[email protected],[email protected]" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf
systemctl restart ssh

Check the result of the hardened host running another audit against it.