add sshd role

roles/sshd/tasks/algorithms.yml

@@ -0,0 +1,33 @@
+---
+# NOTE: order of preference for openssh-server ed25519 -> rsa
+- name: "Algorithms | enable ed25519 authentication algorithm"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^HostKey /etc/ssh/ssh_host_ed25519_key'
+    line: 'HostKey /etc/ssh/ssh_host_ed25519_key'
+    validate: sshd -f %s -t
+
+- name: "Algorithms | enable the RSA authentication algorithm"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^HostKey /etc/ssh/ssh_host_rsa_key'
+    line: 'HostKey /etc/ssh/ssh_host_rsa_key'
+    validate: sshd -f %s -t
+
+- name: "Algorithms | disable the ECDSA algorithm (deemed to be less safe)"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^HostKey /etc/ssh/ssh_host_ecdsa_key'
+    state: absent
+    validate: sshd -f %s -t
+
+- name: "Algorithms | disable the DSA algorithm (considered to be defunct)"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^HostKey /etc/ssh/ssh_host_dsa_key'
+    state: absent
+    validate: sshd -f %s -t

roles/sshd/tasks/authentication.yml

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+---
+- name: "Authentication | Configure SSH authentication settings"
+  notify: Restart sshd
+  loop:
+    - { regexp: '^#?\s*PubkeyAuthentication\s+', line: 'PubkeyAuthentication yes' }
+    - { regexp: '^#?\s*PasswordAuthentication\s+', line: 'PasswordAuthentication {{ password_auth | ternary("yes", "no") }}' }
+    - { regexp: '^#?\s*PermitEmptyPasswords\s+', line: 'PermitEmptyPasswords no' }
+    - { regexp: '^#?\s*ChallengeResponseAuthentication\s+', line: 'ChallengeResponseAuthentication {{ challenge_response_auth | ternary("yes", "no") }}' }
+    - { regexp: '^#?\s*GSSAPIAuthentication\s+', line: 'GSSAPIAuthentication {{ gss_api_auth | ternary("yes", "no") }}' }
+    - {
+      regexp: '^#?\s*AuthenticationMethods\s+',
+      line: "{{ 'AuthenticationMethods publickey password' if password_auth else 'AuthenticationMethods publickey' }}"
+    }
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: "{{ item.regexp }}"
+    line: "{{ item.line }}"
+    validate: /usr/sbin/sshd -t -f %s
+
+- name: "Check if there is an SSH config forced by cloud-init"
+  register: sshd_cloud_init
+  ansible.builtin.stat:
+    path: "/etc/ssh/sshd_config.d/50-cloud-init.conf"
+
+- name: "Authentication | override password authentication by cloud-init to '{{ password_auth | ternary('yes', 'no') }}'"
+  when: sshd_cloud_init.stat.exists
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: "/etc/ssh/sshd_config.d/50-cloud-init.conf"
+    regexp: '^#?PasswordAuthentication'
+    line: 'PasswordAuthentication {{ password_auth | ternary("yes", "no") }}'

roles/sshd/tasks/encryption.yml

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+---
+- name: "Encryption | remove unsafe host keys"
+  loop:
+    - /etc/ssh/ssh_host_ecdsa_key
+    - /etc/ssh/ssh_host_ecdsa_key.pub
+    - /etc/ssh/ssh_host_dsa_key
+    - /etc/ssh/ssh_host_dsa_key.pub
+  notify: Restart sshd
+  ansible.builtin.file:
+    path: "{{ item }}"
+    state: absent

roles/sshd/tasks/install.yml

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+---
+- name: "Install | install OpenSSH (RHEL flavours)"
+  when: ansible_os_family == "RHEL"
+  ansible.builtin.dnf:
+    name: openssh
+    state: installed
+
+- name: "Install | Install OpenSSH (Debian flavours)"
+  when: ansible_os_family == "Debian"
+  ansible.builtin.apt:
+    name: openssh-server
+    state: present

roles/sshd/tasks/main.yml

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+---
+- name: "Install an OpenSSH server"
+  ansible.builtin.include_tasks: "install.yml"
+
+- name: "Configure SSH algorithms"
+  ansible.builtin.include_tasks: "algorithms.yml"
+
+- name: "Configure authentication methods"
+  ansible.builtin.include_tasks: "authentication.yml"
+
+- name: "Configure SSH encryption keys"
+  ansible.builtin.include_tasks: "encryption.yml"
+
+- name: "Configure additional restrictions"
+  ansible.builtin.include_tasks: "restrictions.yml"
+
+- name: "Log at VERBOSE level"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^#?LogLevel'
+    line: 'LogLevel VERBOSE'
+    validate: sshd -f %s -t

roles/sshd/tasks/restrictions.yml

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+---
+- name: "Restrictions | Configure SSH security restrictions"
+  loop:
+    - { regexp: '^#?Protocol\s+', line: 'Protocol 2' }
+    - { regexp: '^PermitRootLogin yes', line: 'PermitRootLogin no' }
+    - { regexp: '^#?X11Forwarding', line: 'X11Forwarding no' }
+    - { regexp: '^#?IgnoreRhosts', line: 'IgnoreRhosts yes' }
+    - { regexp: '^#?DebianBanner\s+', line: 'DebianBanner no' }
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: "{{ item.regexp }}"
+    line: "{{ item.line }}"
+    validate: /usr/sbin/sshd -t -f %s
+
+- name: "Restrictions | toggle PAM"
+  notify: Restart sshd
+  ansible.builtin.lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^#?UsePAM'
+    line: "UsePAM {{ disable_pam | ternary('no', 'yes') }}"
+    validate: sshd -f %s -t
+
+- name: "Restrictions | ensure the SSHD config is restricted to the root user"
+  notify: Restart sshd
+  ansible.builtin.file:
+    path: /etc/ssh/sshd_config
+    owner: root
+    group: root
+    mode: "0600"