ansible_role_proxmox_provision/tasks/fail2ban.yml

---
# -------------------------------------------------
# Deploy Fail2Ban integrated with Proxmox Firewall
# -------------------------------------------------

#################################################
# Detect cluster
#################################################

- name: fail2ban | Detect Proxmox cluster
  ansible.builtin.stat:
    path: /etc/pve/corosync.conf
  register: cluster_status

- name: fail2ban | Set cluster fact
  ansible.builtin.set_fact:
    pve_clustered: "{{ cluster_status.stat.exists }}"

#################################################
# Determine Correct Firewall File
#################################################

- name: fail2ban | Get Proxmox node name
  ansible.builtin.command: hostname
  register: pve_node
  changed_when: false

- name: fail2ban | Set firewall config path
  ansible.builtin.set_fact:
    pve_firewall_config: >-
      {{
        '/etc/pve/firewall/cluster.fw'
        if pve_clustered
        else '/etc/pve/firewall/' + pve_node.stdout + '.fw'
      }}

#################################################
# Detect firewall configuration
#################################################

- name: fail2ban | Check firewall config exists
  ansible.builtin.stat:
    path: "{{ pve_firewall_config }}"
  register: fw_stat

- name: fail2ban | Read firewall config
  ansible.builtin.slurp:
    src: "{{ pve_firewall_config }}"
  register: fw_content
  when: fw_stat.stat.exists

- name: fail2ban | Determine if firewall enabled
  ansible.builtin.set_fact:
    pve_firewall_enabled: >-
      {{
        fw_stat.stat.exists and
        (fw_content.content | b64decode) is search('enable:\s*1')
      }}

- name: fail2ban | Warn if firewall not enabled
  ansible.builtin.debug:
    msg: >
      WARNING: Proxmox firewall is disabled in configuration.
      Fail2Ban will not actively block traffic.
  when: not pve_firewall_enabled

#################################################
# Validate firewall runtime state
#################################################

- name: fail2ban | Check firewall runtime status
  ansible.builtin.command: pve-firewall status
  register: pve_fw_status
  changed_when: false
  failed_when: false

- name: fail2ban | Abort if firewall daemon not running
  ansible.builtin.fail:
    msg: >
      Proxmox firewall service is not running.
      Run: systemctl enable --now pve-firewall
  when: pve_fw_status.rc != 0

#################################################
# Corosync safety validation
#################################################

- name: fail2ban | Validate corosync firewall rules
  ansible.builtin.command: pve-firewall compile
  register: compiled_fw
  changed_when: false
  failed_when: false
  when: cluster_status.stat.exists

- name: fail2ban | Fail if corosync ports are being dropped
  ansible.builtin.fail:
    msg: >
      Firewall configuration appears to affect Corosync ports (5404/5405).
      Refusing to continue to prevent cluster outage.
  when:
    - cluster_status.stat.exists
    - compiled_fw.stdout is search('5404.*DROP|5405.*DROP')

#################################################
# Install Fail2Ban
#################################################

- name: fail2ban | Install fail2ban
  ansible.builtin.apt:
    name: fail2ban
    state: present
    update_cache: true

#################################################
# Create Proxmox firewall IPSet
#################################################

- name: fail2ban | Add Fail2Ban IPSet to firewall
  ansible.builtin.blockinfile:
    path: "{{ pve_firewall_config }}"
    marker: "# {mark} ANSIBLE FAIL2BAN IPSET"
    insertbefore: BOF
    block: |
      [IPSET {{ f2b_ipset_name }}]
      comment: Fail2Ban dynamic blacklist
    create: false
  notify: Reload pve firewall
  # noqa risky-file-permissions

- name: fail2ban | Add drop rule for Fail2Ban IPSet
  ansible.builtin.blockinfile:
    path: "{{ pve_firewall_config }}"
    marker: "# {mark} ANSIBLE FAIL2BAN RULE"
    insertafter: '^\[RULES\]'
    block: |
      IN DROP -source +{{ f2b_ipset_name }}
    create: false
  notify: Reload pve firewall
  # noqa risky-file-permissions

- name: fail2ban | Extract corosync ring0 address
  ansible.builtin.shell: |
    set -o pipefail
    grep ring0_addr /etc/pve/corosync.conf | awk '{print $2}'
  args:
    executable: /bin/bash
  register: corosync_ip
  changed_when: false
  when: cluster_status.stat.exists

# Then automatically whitelist it in Fail2Ban:
# ignoreip = 127.0.0.1/8 {{ corosync_ip.stdout }}

#################################################
# Create Fail2Ban Proxmox action
#################################################

- name: fail2ban | Create Proxmox firewall action
  ansible.builtin.copy:
    dest: /etc/fail2ban/action.d/proxmox-fw.conf
    mode: '0644'
    content: |
      [Definition]
      actionstart =
      actionstop =
      actioncheck =
      actionban = /usr/sbin/pve-firewall ipset add {{ f2b_ipset_name }} <ip>
      actionunban = /usr/sbin/pve-firewall ipset del {{ f2b_ipset_name }} <ip>

#################################################
# Configure AD-aware jail
#################################################

- name: fail2ban | Ensure jail.d exists
  ansible.builtin.file:
    path: /etc/fail2ban/jail.d
    state: directory
    mode: '0755'

- name: fail2ban | Configure Fail2Ban jails
  ansible.builtin.copy:
    dest: /etc/fail2ban/jail.d/proxmox.conf
    mode: '0644'
    content: |
      [DEFAULT]
      bantime  = {{ f2b_bantime }}
      findtime = {{ f2b_findtime }}
      maxretry = {{ f2b_maxretry }}
      bantime.increment = {{ f2b_bantime_increment }}
      bantime.factor = {{ f2b_bantime_factor }}
      bantime.max = {{ f2b_bantime_max }}
      backend  = systemd
      banaction = proxmox-fw
      ignoreip = 127.0.0.1/8{% if pve_clustered %} {{ corosync_ip.stdout }}{% endif %} 192.168.2.0/24

      #################################################
      # SSH
      #################################################
      [sshd]
      enabled = true
      journalmatch = _SYSTEMD_UNIT=sshd.service

      #################################################
      # Proxmox GUI + AD authentication
      #################################################
      [proxmox-auth]
      enabled  = true
      port     = https,8006
      filter   = proxmox-auth
      logpath  = /var/log/pveproxy/access.log

      #################################################
      # Progressive escalation (recidive)
      #################################################
      [recidive]
      enabled  = true
      filter   = recidive
      logpath  = /var/log/fail2ban.log
      bantime  = {{ f2b_recidive_bantime }}
      findtime = {{ f2b_recidive_findtime }}
      maxretry = {{ f2b_recidive_maxretry }}
      banaction = proxmox-fw
  notify:
    - Restart fail2ban

#################################################
# AD / Winbind filter
#################################################

- name: fail2ban | Create AD-aware filter
  ansible.builtin.copy:
    dest: /etc/fail2ban/filter.d/proxmox-auth.conf
    mode: '0644'
    content: |
      [Definition]
      failregex = authentication failure; rhost=<HOST>
                  pam_unix\(sshd:auth\): authentication failure;.*rhost=<HOST>
                  winbind.*authentication for user.*from <HOST> failed
      ignoreregex =
  notify:
    - Restart fail2ban

#################################################
# Enable services
#################################################

- name: fail2ban | Enable fail2ban
  ansible.builtin.systemd:
    name: fail2ban
    enabled: true
    state: started

#################################################
# List banned IPs cluster-wide
#################################################

- name: fail2ban | Get banned IPs from Proxmox IPSet
  ansible.builtin.command: pve-firewall ipset list {{ f2b_ipset_name }}
  register: banned_ips
  changed_when: false
  failed_when: false

- name: fail2ban | Show banned IPs
  ansible.builtin.debug:
    msg: >
      Current banned IPs (cluster-wide):
      {{ banned_ips.stdout_lines | default([]) }}

#################################################
# Manual unban
#################################################

- name: fail2ban | Unban specific IP
  ansible.builtin.command: >
    pve-firewall ipset del {{ f2b_ipset_name }} {{ f2b_unban_ip }}
  when: f2b_unban_ip | length > 0
  register: unban_result
  changed_when: "'removed' in unban_result.stdout or unban_result.rc == 0"
  failed_when: false

- name: fail2ban | Report unban result
  ansible.builtin.debug:
    msg: "Unbanned IP {{ f2b_unban_ip }}"
  when: f2b_unban_ip | length > 0