infra: Samihost fail2ban watchdog (auto-unban trusted IPs, drift guard, cap at 200)

2026-06-10 11:28:42 -07:00
parent 1d8919532b
commit 0aa7244cf4
1 changed files with 76 additions and 0 deletions
@@ -0,0 +1,76 @@
+#!/bin/bash
+# Samihost fail2ban watchdog — auto-unban whitelisted IPs and keep ignoreip list in sync.
+# Deployed to /usr/local/bin/samihost-fail2ban-watchdog.sh on 194.163.161.162
+# Cron: every 30 min (0,30 * * * *)
+
+set -euo pipefail
+
+JAIL_LOCAL=/etc/fail2ban/jail.local
+BACKUP=/etc/fail2ban/jail.local.watchdog.bak
+EXPECTED_IGNOREIP="127.0.0.1/8 ::1 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 fc00::/7 fe80::/10 100.64.0.0/10 100.121.150.22 100.85.236.10 100.71.97.12 100.81.59.99 100.98.123.59 194.233.88.206 173.212.201.200 194.163.161.162"
+LOG=/var/log/samihost-fail2ban-watchdog.log
+TELEGRAM_LOG=/tmp/fail2ban-watchdog-last-action
+
+ts() { date -u +"%Y-%m-%dT%H:%M:%SZ"; }
+log() { echo "$(ts) $*" | tee -a "$LOG"; }
+
+mkdir -p "$(dirname "$LOG")"
+touch "$LOG"
+
+# --- 1. Verify ignoreip line is intact and matches expected ---
+CURRENT=$(grep '^ignoreip' "$JAIL_LOCAL" | sed 's/^ignoreip[[:space:]]*=[[:space:]]*//' || true)
+EXPECTED_NORMALIZED=$(echo "$EXPECTED_IGNOREIP" | tr ' ' '\n' | sort -u | tr '\n' ' ' | sed 's/ $//')
+CURRENT_NORMALIZED=$(echo "$CURRENT" | tr ' ' '\n' | sort -u | tr '\n' ' ' | sed 's/ $//')
+
+if [ "$CURRENT_NORMALIZED" != "$EXPECTED_NORMALIZED" ]; then
+  log "ALERT: ignoreip line drifted. Restoring."
+  cp "$JAIL_LOCAL" "$BACKUP"
+  sed -i "s|^ignoreip = .*|ignoreip = $EXPECTED_IGNOREIP|" "$JAIL_LOCAL"
+  fail2ban-client reload
+  echo "ignoreip restored at $(ts)" > "$TELEGRAM_LOG"
+  log "ignoreip restored, fail2ban reloaded"
+fi
+
+# --- 2. Unban any currently-banned IPs that match our trusted set ---
+BANNED=$(fail2ban-client status sshd 2>/dev/null | awk -F: '/Banned IP list/{print $2}' | tr ' ' '\n' | grep -v '^$' || true)
+UNBANNED=0
+for ip in $BANNED; do
+  # Match against any trusted network
+  is_trusted=0
+  for net in 127.0.0.0/8 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 100.64.0.0/10 ::1 fc00::/7 fe80::/10 100.121.150.22 100.85.236.10 100.71.97.12 100.81.59.99 100.98.123.59 194.233.88.206 173.212.201.200 194.163.161.162; do
+    if [[ "$net" == *"/"* ]]; then
+      # CIDR match (simple IPv4 only — IPv6 needs python or ipcalc, skip for now)
+      base="${net%/*}"
+      mask="${net#*/}"
+      if [[ "$ip" == "$base"* ]] || python3 -c "import ipaddress,sys; sys.exit(0 if ipaddress.ip_address('$ip') in ipaddress.ip_network('$net', strict=False) else 1)" 2>/dev/null; then
+        is_trusted=1
+        break
+      fi
+    else
+      if [ "$ip" = "$net" ]; then
+        is_trusted=1
+        break
+      fi
+    fi
+  done
+  if [ "$is_trusted" = "1" ]; then
+    if fail2ban-client set sshd unbanip "$ip" >/dev/null 2>&1; then
+      log "auto-unbanned trusted IP: $ip"
+      UNBANNED=$((UNBANNED+1))
+    fi
+  fi
+done
+
+[ "$UNBANNED" -gt 0 ] && echo "auto-unbanned $UNBANNED trusted IPs at $(ts)" > "$TELEGRAM_LOG"
+
+# --- 3. Cap the ban count — if more than 200 are banned, mass-unban stale ones ---
+TOTAL_BANNED=$(fail2ban-client status sshd 2>/dev/null | awk '/Currently banned/{print $NF}' || echo 0)
+if [ "$TOTAL_BANNED" -gt 200 ]; then
+  log "ALERT: $TOTAL_BANNED IPs banned. Mass-unbanning all."
+  for ip in $BANNED; do
+    fail2ban-client set sshd unbanip "$ip" >/dev/null 2>&1 || true
+  done
+  echo "mass-unbanned $TOTAL_BANNED stale bans at $(ts)" > "$TELEGRAM_LOG"
+fi
+
+log "watchdog run complete (unbanned=$UNBANNED, total_banned=$TOTAL_BANNED)"