Redesign of the nft firewall based on an existing Ansible playbook for the same purpose.

2025-12-29 17:49:12 +01:00
parent 13893f6cd9
commit f03b0c7ab3
10 changed files with 247 additions and 189 deletions
--- a/sbin/fw-apply
+++ b/sbin/fw-apply
@@ -0,0 +1,193 @@
+#!/bin/bash
+# *** [ Ansible managed file: DO NOT EDIT DIRECTLY ] ***
+
+#
+# fw-apply
+#
+# Generic firewall loader (Ansible-independent):
+# - Reads config from /etc/nftables.conf.d/nft-fw.conf (optional)
+# - Renders /etc/nftables.conf.in using envsubst
+# - Validates with: nft -c -f <rendered>
+# - Applies by deleting ONLY table inet fw_static and loading the new definition
+#   (keeps fail2ban tables intact)
+#
+# Usage:
+#   fw-apply         -> validate + apply
+#   fw-apply --check -> validate only (no changes)
+#
+
+set -euo pipefail
+
+############################
+# Argument handling
+############################
+DO_APPLY=true
+if [[ "${1:-}" == "--check" ]]; then
+  DO_APPLY=false
+elif [[ "${1:-}" != "" ]]; then
+  echo "Usage: $0 [--check]" >&2
+  exit 2
+fi
+
+############################
+# Config location
+############################
+CFG_DIR="/etc/nftables.conf.d"
+CFG_FILE="$CFG_DIR/nft-fw.conf"
+
+############################
+# Defaults (used if config missing/partial)
+############################
+EXT_IF="eth0"
+PRIV_IF="enp7s0"
+PRIV_NET="172.20.0.0/21"
+
+ALLOW_SSH_PUBLIC_IN="true"
+ALLOW_APT_PUBLIC_OUT="true"
+
+ALLOW_ICMP4_PUBLIC="true"
+ALLOW_ICMP6_PUBLIC="true"
+FORCE_ICMP6_ESSENTIAL="true"
+
+############################
+# Load config if present
+############################
+if [[ -r "$CFG_FILE" ]]; then
+  # shellcheck disable=SC1090
+  source "$CFG_FILE"
+fi
+
+############################
+# Helpers
+############################
+normalize_bool() {
+  # Robust against CRLF and leading/trailing whitespace.
+  local v
+  v="$(printf '%s' "${1:-}" | tr -d '\r' | xargs)"
+  case "${v,,}" in
+    true|yes|1) echo true ;;
+    false|no|0|"") echo false ;;
+    *) echo false ;;
+  esac
+}
+
+ALLOW_SSH_PUBLIC_IN="$(normalize_bool "$ALLOW_SSH_PUBLIC_IN")"
+ALLOW_APT_PUBLIC_OUT="$(normalize_bool "$ALLOW_APT_PUBLIC_OUT")"
+ALLOW_ICMP4_PUBLIC="$(normalize_bool "$ALLOW_ICMP4_PUBLIC")"
+ALLOW_ICMP6_PUBLIC="$(normalize_bool "$ALLOW_ICMP6_PUBLIC")"
+FORCE_ICMP6_ESSENTIAL="$(normalize_bool "$FORCE_ICMP6_ESSENTIAL")"
+
+############################
+# Determine external usage
+############################
+# EXT_IF is considered "in use" if any externally-relevant feature is enabled.
+NEED_EXT=false
+if [[ "$ALLOW_SSH_PUBLIC_IN" == "true" || "$ALLOW_APT_PUBLIC_OUT" == "true" ]]; then
+  NEED_EXT=true
+fi
+
+############################
+# Build envsubst blocks (must contain REAL newlines)
+############################
+SSH_PUBLIC_IN_RULE=""
+APT_PUBLIC_OUT_RULES=""
+ICMP_PUBLIC_IN_RULES=""
+ICMP_PUBLIC_OUT_RULES=""
+
+# SSH IN (public)
+if [[ "$ALLOW_SSH_PUBLIC_IN" == "true" ]]; then
+  SSH_PUBLIC_IN_RULE="$(cat <<EOF
+    iif "$EXT_IF" tcp dport 22 accept
+EOF
+)"
+fi
+
+# APT OUT (public) - DNS + HTTP/HTTPS
+if [[ "$ALLOW_APT_PUBLIC_OUT" == "true" ]]; then
+  APT_PUBLIC_OUT_RULES="$(cat <<EOF
+    oif "$EXT_IF" udp dport 53 accept
+    oif "$EXT_IF" tcp dport 53 accept
+    oif "$EXT_IF" tcp dport { 80, 443 } accept
+EOF
+)"
+fi
+
+# ICMPv4 echo
+if [[ "$ALLOW_ICMP4_PUBLIC" == "true" ]]; then
+  ICMP_PUBLIC_IN_RULES="$(cat <<EOF
+    iif "$EXT_IF" ip protocol icmp accept
+EOF
+)"
+  ICMP_PUBLIC_OUT_RULES="$(cat <<EOF
+    oif "$EXT_IF" ip protocol icmp accept
+EOF
+)"
+fi
+
+# ICMPv6 essential (no echo) if EXT used and forcing enabled
+ALLOW_ICMP6_ESSENTIAL=false
+if [[ "$FORCE_ICMP6_ESSENTIAL" == "true" && "$NEED_EXT" == "true" ]]; then
+  ALLOW_ICMP6_ESSENTIAL=true
+fi
+
+if [[ "$ALLOW_ICMP6_ESSENTIAL" == "true" ]]; then
+  [[ -n "$ICMP_PUBLIC_IN_RULES" ]] && ICMP_PUBLIC_IN_RULES+=$'\n'
+  [[ -n "$ICMP_PUBLIC_OUT_RULES" ]] && ICMP_PUBLIC_OUT_RULES+=$'\n'
+
+  ICMP_PUBLIC_IN_RULES+=$(cat <<EOF
+    iif "$EXT_IF" icmpv6 type { nd-router-solicit, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, nd-redirect, packet-too-big, time-exceeded, parameter-problem, destination-unreachable } accept
+EOF
+)
+  ICMP_PUBLIC_OUT_RULES+=$(cat <<EOF
+    oif "$EXT_IF" icmpv6 type { nd-router-solicit, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, nd-redirect, packet-too-big, time-exceeded, parameter-problem, destination-unreachable } accept
+EOF
+)
+fi
+
+# ICMPv6 echo (ping6)
+if [[ "$ALLOW_ICMP6_PUBLIC" == "true" ]]; then
+  [[ -n "$ICMP_PUBLIC_IN_RULES" ]] && ICMP_PUBLIC_IN_RULES+=$'\n'
+  [[ -n "$ICMP_PUBLIC_OUT_RULES" ]] && ICMP_PUBLIC_OUT_RULES+=$'\n'
+
+  ICMP_PUBLIC_IN_RULES+=$(cat <<EOF
+    iif "$EXT_IF" icmpv6 type { echo-request, echo-reply } accept
+EOF
+)
+  ICMP_PUBLIC_OUT_RULES+=$(cat <<EOF
+    oif "$EXT_IF" icmpv6 type { echo-request, echo-reply } accept
+EOF
+)
+fi
+
+############################
+# Export for envsubst
+############################
+export EXT_IF PRIV_IF PRIV_NET
+export SSH_PUBLIC_IN_RULE APT_PUBLIC_OUT_RULES
+export ICMP_PUBLIC_IN_RULES ICMP_PUBLIC_OUT_RULES
+
+############################
+# Render + validate + apply
+############################
+TMP="$(mktemp -p /run nft-fw.XXXXXX)"
+trap 'rm -f "$TMP"' EXIT
+
+envsubst < /etc/nftables.conf.in > "$TMP"
+
+# Replace only our table (keep fail2ban intact)
+nft delete table inet fw_static 2>/dev/null || true
+
+# Validate syntax
+nft -c -f "$TMP"
+
+if [[ "$DO_APPLY" == "true" ]]; then
+  nft -f "$TMP"
+  install -m 600 "$TMP" /etc/nftables.conf
+else
+  echo "fw-apply: check mode"
+  [[ -r "$CFG_FILE" ]] && echo "- config loaded: $CFG_FILE" || echo "- config loaded: defaults only"
+  echo "- rendered nftables ruleset: OK"
+  echo "- syntax check (nft -c): OK"
+  echo "- no changes applied"
+fi
+