diff --git a/FreeBSD-OpenSSH-Hardening-Guides.md b/FreeBSD-OpenSSH-Hardening-Guides.md index 832e68a..facb00b 100644 --- a/FreeBSD-OpenSSH-Hardening-Guides.md +++ b/FreeBSD-OpenSSH-Hardening-Guides.md @@ -6,43 +6,44 @@ 1. Remove existing key-pairs, disable DSA & ECDSA -```sh -rm -f /etc/ssh/ssh_host_* -sysrc sshd_dsa_enable="no" -sysrc sshd_ecdsa_enable="no" -sysrc sshd_ed25519_enable="yes" -sysrc sshd_rsa_enable="yes" -``` + ```sh + rm -f /etc/ssh/ssh_host_* + sysrc sshd_dsa_enable="no" + sysrc sshd_ecdsa_enable="no" + sysrc sshd_ed25519_enable="yes" + sysrc sshd_rsa_enable="yes" + ``` 2. Regenerate RSA and Ed25519 keys -```sh -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 "" -``` + ```sh + 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 "" + ``` 3. Remove Diffie-Hellman moduli smaller than 3071 -```sh -awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe -mv /etc/ssh/moduli.safe /etc/ssh/moduli -``` + ```sh + awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe + mv /etc/ssh/moduli.safe /etc/ssh/moduli + ``` 4. Restrict supported key exchange, cipher, and MAC algorithms -```sh -printf "\n# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\n# hardening guide.\nKexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\nHostKeyAlgorithms ssh-ed25519,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com\n" >> /etc/ssh/sshd_config -``` + ```sh + printf "\n# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\n# hardening guide.\nKexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\nHostKeyAlgorithms ssh-ed25519,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com\n" >> /etc/ssh/sshd_config + ``` 5. Restart sshd -```sh -service sshd restart -``` + ```sh + service sshd restart + ``` + # Client 1. Run the following in a terminal to harden the OpenSSH client for the local user -```sh -mkdir -p -m 0700 ~/.ssh; printf "\nHost *\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr\n KexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\n HostKeyAlgorithms ssh-ed25519,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com\n" >> ~/.ssh/config -``` \ No newline at end of file + ```sh + mkdir -p -m 0700 ~/.ssh; printf "\nHost *\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr\n KexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\n HostKeyAlgorithms ssh-ed25519,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com\n" >> ~/.ssh/config + ``` \ No newline at end of file