ansible_role_proxmox_provision/tasks/fail2ban.yml

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

#################################################
# Detect Proxmox
#################################################

- name: fail2ban | Detect Proxmox
  ansible.builtin.stat:
    path: /usr/bin/pveversion
  register: pve_installed

#################################################
# Ensure pmxcfs is mounted (cluster filesystem)
#################################################

- name: fail2ban | Check pmxcfs cluster filesystem
  ansible.builtin.stat:
    path: /etc/pve/.members
  register: pmxcfs_running
  when: pve_installed.stat.exists | default(false)

- name: fail2ban | Warn if pmxcfs not mounted (no quorum)
  ansible.builtin.debug:
    msg: >
      /etc/pve is not mounted or node has no quorum.
      Refusing to modify cluster firewall.
  when:
    - pve_installed.stat.exists | default(false)
    - not pmxcfs_running.stat.exists

#################################################
# Detect cluster membership
#################################################

- name: fail2ban | Detect Proxmox cluster membership
  ansible.builtin.stat:
    path: /etc/pve/corosync.conf
  register: clustered
  when: pmxcfs_running.stat.exists | default(false)

- name: fail2ban | Warn if corosync.conf is missing
  ansible.builtin.debug:
    msg: >
      node has no quorum.
      Refusing to modify cluster firewall.
  when:
    - pve_installed.stat.exists | default(false)
    - pmxcfs_running.stat.exists | default(false)
    - not clustered.stat.exists

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

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

#################################################
# Ensure jail.local exists (do NOT copy jail.conf)
#################################################

- name: fail2ban | Ensure jail.local exists
  ansible.builtin.file:
    path: /etc/fail2ban/jail.local
    state: touch
    owner: root
    group: root
    mode: '0644'

#################################################
# Configure Fail2Ban jails
#################################################

- name: fail2ban | Configure Fail2Ban jails
  ansible.builtin.blockinfile:
    dest: /etc/fail2ban/jail.local
    marker: "# {mark} ANSIBLE MANAGED BLOCK - PROXMOX"
    block: |
      # jail.conf (default)
      # jail.local (override defaults)
      [DEFAULT]
      bantime  = {{ f2b_bantime }}
      findtime = {{ f2b_findtime }}
      maxretry = {{ f2b_maxretry }}
      bantime.increment = {{ f2b_bantime_increment }}
      bantime.factor = {{ f2b_bantime_factor }}
      bantime.maxtime = {{ f2b_bantime_max }}
      backend  = systemd
      banaction = {% if (clustered.stat.exists | default(false)) %} proxmox-fw{% else %} iptables-multiport{% endif %}
      ignoreip = 127.0.0.1/8 192.168.2.0/24

      #################################################
      # SSH
      #################################################
      [sshd]
      enabled = true

      #################################################
      # Proxmox GUI + AD authentication
      #################################################
      [proxmox]
      enabled  = true
      port = https,http,8006
      filter   = proxmox

      #################################################
      # 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 = {% if (clustered.stat.exists | default(false)) %} proxmox-fw{% else %} iptables-multiport{% endif %}
  notify:
    - Reload fail2ban

- name: fail2ban | Place Proxmox filter definition
  ansible.builtin.copy:
    dest: /etc/fail2ban/filter.d/proxmox.conf
    content: |
      [Definition]
      failregex = pvedaemon\[.*authentication failure; rhost=<HOST> user=.* msg=.*
      ignoreregex =
      journalmatch = _SYSTEMD_UNIT=pvedaemon.service
    owner: root
    group: root
    mode: '0644'
  notify:
    - Reload fail2ban

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

- name: fail2ban | Get Proxmox node name
  ansible.builtin.set_fact:
    pve_node: "{{ ansible_hostname }}"
  when: not clustered.stat.exists

- name: fail2ban | Set firewall config path
  ansible.builtin.set_fact:
    pve_firewall_config: >-
      {{
        '/etc/pve/firewall/cluster.fw'
        if clustered.stat.exists
        else '/etc/pve/nodes/' + pve_node + '.fw'
      }}
  when: pve_installed.stat.exists | default(false)

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

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

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

- name: fail2ban | Determine if firewall enabled
  ansible.builtin.set_fact:
    pve_firewall_enabled: >-
      {{
        (fw_stat.stat.exists | default(false)) and
        (
          (fw_content.content | default('') | 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
  when: pmxcfs_running.stat.exists | default(false)

- name: fail2ban | Abort if firewall daemon not running
  ansible.builtin.debug:
    msg: >
      Proxmox firewall service is not running.
      You can run: systemctl enable --now pve-firewall
  when:
    - pve_fw_status is defined
    - pve_fw_status.rc != 0
    - fw_stat.stat.exists | default(false)
    - pmxcfs_running.stat.exists | default(false)

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

- name: fail2ban | Validate corosync firewall rules
  ansible.builtin.command: pve-firewall compile
  register: compiled_fw
  changed_when: false
  failed_when: compiled_fw.rc != 0
  when: clustered.stat.exists | default(false)

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

#################################################
# Deploy cluster-aware Fail2Ban action
#################################################

- name: fail2ban | Deploy proxmox-fw action
  ansible.builtin.copy:
    dest: /etc/fail2ban/action.d/proxmox-fw.conf
    owner: root
    group: root
    mode: '0644'
    content: |
      [Definition]

      fwfile = {{ pve_firewall_config }}

      rule = DROP    -source <ip> -log nolog

      actionban = \
          if [ -f <fwfile> ]; then \
              grep -qF "<rule>" <fwfile> || echo "<rule>" >> <fwfile>; \
              pve-firewall compile >/dev/null 2>&1 || true; \
          fi

      actionunban = \
          if [ -f <fwfile> ]; then \
              sed -i "\|<rule>|d" <fwfile>; \
              pve-firewall compile >/dev/null 2>&1 || true; \
          fi

      actionstart =
      actionstop =
  when:
    - clustered.stat.exists | default(false)
  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 is defined and 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