feat ✨: Add Fail2ban integration with Proxmox Firewall

This commit adds Fail2ban settings to `defaults/main.yml`, a new task to restart the fail2ban service, and a task file for deploying Fail2Ban integrated with Proxmox Firewall. The new tasks include checks, validations, and configuration to enhance security by blocking malicious IP addresses.

defaults/main.yml

@@ -47,3 +47,15 @@ journald_runtime_max_use: "100M"
 vm_dirty_ratio: 15
 vm_dirty_background_ratio: 5
 vm_swappiness: "{{ proxmox_swapiness }}"
+
+# Fail2ban settings
+f2b_bantime: 1800             # 30 minutes
+f2b_findtime: 600
+f2b_maxretry: 5
+f2b_recidive_bantime: 86400    # 24 hours
+f2b_recidive_findtime: 86400   # 24 hours
+f2b_recidive_maxretry: 3
+f2b_ipset_name: f2b-blacklist
+f2b_bantime_increment: true
+f2b_bantime_factor: 2
+f2b_bantime_max: 86400

handlers/main.yml

@@ -31,3 +31,8 @@
 - name: Reload systemd
   ansible.builtin.systemd:
     daemon_reload: true
+
+- name: Restart fail2ban
+  ansible.builtin.systemd:
+    name: fail2ban
+    state: restarted

tasks/fail2ban.yml

@@ -0,0 +1,236 @@
+---
+# -------------------------------------------------
+# Deploy Fail2Ban integrated with Proxmox Firewall
+# -------------------------------------------------
+
+#################################################
+# Detect firewall configuration
+#################################################
+
+- name: fail2ban | Check if cluster firewall config exists
+  ansible.builtin.stat:
+    path: /etc/pve/firewall/cluster.fw
+  register: cluster_fw
+
+- name: fail2ban | Read cluster firewall config
+  slurp:
+    src: /etc/pve/firewall/cluster.fw
+  register: cluster_fw_content
+  when: cluster_fw.stat.exists
+
+- name: fail2ban | Determine if firewall enabled
+  ansible.builtin.set_fact:
+    pve_firewall_enabled: >-
+      {{
+        cluster_fw.stat.exists and
+        (cluster_fw_content.content | b64decode)
+        is search('enable:\s*1')
+      }}
+
+- name: fail2ban | Abort if firewall not enabled
+  ansible.builtin.fail:
+    msg: >
+      Proxmox firewall is not enabled at Datacenter level.
+      Enable it before deploying Fail2Ban integration.
+  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: "'Status: enabled' not in pve_fw_status.stdout"
+
+#################################################
+# 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 }}"
+
+#################################################
+# 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')
+    - compiled_fw.stdout is search('DROP')
+
+#################################################
+# Install Fail2Ban
+#################################################
+
+- name: fail2ban | Install fail2ban
+  ansible.builtin.apt:
+    name: fail2ban
+    state: present
+    update_cache: true
+
+#################################################
+# Create Proxmox firewall IPSet (cluster-wide)
+#################################################
+
+- name: fail2ban | Ensure firewall cluster config exists
+  ansible.builtin.file:
+    path: /etc/pve/firewall
+    state: directory
+  when: pve_clustered
+
+- name: fail2ban | Add Fail2Ban IPSet to cluster firewall
+  ansible.builtin.blockinfile:
+    path: /etc/pve/firewall/cluster.fw
+    marker: "# {mark} ANSIBLE FAIL2BAN IPSET"
+    block: |
+      [IPSET {{ f2b_ipset_name }}]
+    create: true
+  when: pve_clustered
+
+- name: fail2ban | Add drop rule for Fail2Ban IPSet
+  ansible.builtin.blockinfile:
+    path: /etc/pve/firewall/cluster.fw
+    marker: "# {mark} ANSIBLE FAIL2BAN RULE"
+    block: |
+      [RULES]
+      IN DROP -source +{{ f2b_ipset_name }}
+  when: pve_clustered
+
+- name: fail2ban | Extract corosync ring0 address
+  ansible.builtin.shell: grep ring0_addr /etc/pve/corosync.conf | awk '{print $2}'
+  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 {{ corosync_ip.stdout | default('') }} 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
+
+- name: fail2ban | Reload Proxmox firewall
+  ansible.builtin.command: pve-firewall reload
+  changed_when: false