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diff --git a/content/blog/2023-10-15-alpine-ssh-hardening.org b/content/blog/2023-10-15-alpine-ssh-hardening.org deleted file mode 100644 index 4e7fcc5..0000000 --- a/content/blog/2023-10-15-alpine-ssh-hardening.org +++ /dev/null @@ -1,71 +0,0 @@ -#+title: SSH Hardening for Alpine Linux -#+date: 2023-10-15 -#+description: A quick guide to harden SSH configuration on Alpine. -#+filetags: :linux: - -* Overview -This guide follows the standard -[[https://www.ssh-audit.com/hardening_guides.html][ssh-audit]] hardening -guide, tweaked for Alpine Linux. - -* Hardening Guide -These steps must be performed as root. You can try to use =doas= or -=sudo=, but there may be issues. - -1. Re-generate the RSA and ED25519 keys - -#+begin_src sh -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 "" -#+end_src - -2. [@2] Remove small Diffie-Hellman moduli - -#+begin_src sh -awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe -mv /etc/ssh/moduli.safe /etc/ssh/moduli -#+end_src - -3. [@3] Enable the RSA and ED25519 HostKey directives in the - /etc/ssh/sshd_{config} file - -#+begin_src sh -sed -i 's/^\#HostKey \/etc\/ssh\/ssh_host_\(rsa\|ed25519\)_key$/HostKey \/etc\/ssh\/ssh_host_\1_key/g' /etc/ssh/sshd_config -#+end_src - -4. [@4] Restrict supported key exchange, cipher, and MAC algorithms - -#+begin_src sh -echo -e "\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" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf -#+end_src - -5. [@5] Include the /etc/ssh/sshd_{config}.d directory - -#+begin_src sh -echo -e "Include /etc/ssh/sshd_config.d/*.conf" > /etc/ssh/sshd_config -#+end_src - -6. [@6] Restart OpenSSH server - -#+begin_src sh -rc-service sshd restart -#+end_src - -* Testing SSH -You can test the results with the =ssh-audit= python script. - -#+begin_src sh -pip3 install ssh-audit -ssh-audit localhost -#+end_src - -If everything succeeded, the results will show as all green. If anything -is yellow, orange, or red, you may need to tweak additional settings. - -#+begin_src txt -,#+caption: ssh audit -#+end_src - -#+caption: ssh-audit -[[https://img.cleberg.net/blog/20231015-ssh-hardening/ssh-audit.png]] |