initial commit

2025-12-27 19:23:42 +01:00
commit fea1d9fdc0
8 changed files with 328 additions and 0 deletions
--- a/bin/fw-apply
+++ b/bin/fw-apply
@@ -0,0 +1,155 @@
+#!/usr//bin/env bash
+set -euo pipefail
+
+########################
+# Args
+########################
+DO_APPLY=true
+if [[ "${1:-}" == "--check" ]]; then
+  DO_APPLY=false
+elif [[ "${1:-}" != "" ]]; then
+  echo "Usage: $0 [--check]" >&2
+  exit 2
+fi
+
+########################
+# Defaults
+########################
+EXT_IF="eth0"
+PRIV_IF="enp7s0"
+PRIV_NET="172.20.0.0/21"
+
+ALLOW_SSH_PUBLIC_IN=false
+ALLOW_APT_PUBLIC_OUT=false
+
+ALLOW_ICMP4_PUBLIC=true
+ALLOW_ICMP6_PUBLIC=true
+
+########################
+# Optional config file
+########################
+CFG="/etc/default/nft-fw"
+if [[ -r "$CFG" ]]; then
+  # shellcheck disable=SC1090
+  source "$CFG"
+fi
+
+########################
+# Normalize booleans
+########################
+normalize_bool() {
+  # trim whitespace + remove CR (Windows line endings)
+  local v
+  v="$(printf '%s' "${1:-}" | tr -d '\r' | xargs)"
+  case "${v,,}" in
+    true|yes|1) echo true ;;
+    false|no|0|"") echo false ;;
+    *) echo false ;;
+  esac
+}
+
+ALLOW_ICMP4_PUBLIC="$(normalize_bool "${ALLOW_ICMP4_PUBLIC:-true}")"
+ALLOW_ICMP6_PUBLIC="$(normalize_bool "${ALLOW_ICMP6_PUBLIC:-true}")"
+ALLOW_SSH_PUBLIC_IN="$(normalize_bool "${ALLOW_SSH_PUBLIC_IN:-false}")"
+ALLOW_APT_PUBLIC_OUT="$(normalize_bool "${ALLOW_APT_PUBLIC_OUT:-false}")"
+
+
+NEED_EXT=false
+if [[ "$ALLOW_SSH_PUBLIC_IN" == "true" || "$ALLOW_APT_PUBLIC_OUT" == "true" || "$ALLOW_ICMP4_PUBLIC" == "true" || "$ALLOW_ICMP6_PUBLIC" == "true" ]]; then
+  NEED_EXT=true
+fi
+
+EFFECTIVE_ALLOW_ICMP6_PUBLIC="$ALLOW_ICMP6_PUBLIC"
+if [[ "$NEED_EXT" == "true" ]]; then
+  EFFECTIVE_ALLOW_ICMP6_PUBLIC=true
+fi
+
+########################
+# Build optional rule blocks
+########################
+ICMP_PUBLIC_IN_RULES=""
+ICMP_PUBLIC_OUT_RULES=""
+SSH_PUBLIC_IN_RULE=""
+APT_PUBLIC_OUT_RULES=""
+
+
+# ICMPv4 optional
+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 "$EXT_IF" ip protocol icmp accept
+EOF
+)"
+fi
+
+# ICMPv6 optional (oder erzwungen über EFFECTIVE_ALLOW_ICMP6_PUBLIC)
+if [[ "$EFFECTIVE_ALLOW_ICMP6_PUBLIC" == "true" ]]; then
+  # Falls schon was drin ist, füge sauber eine Leerzeile/Zeilenumbruch hinzu
+  [[ -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" ip6 nexthdr icmpv6 accept
+EOF
+)
+  ICMP_PUBLIC_OUT_RULES+=$(cat <<EOF
+    oif "$EXT_IF" ip6 nexthdr icmpv6 accept
+EOF
+)
+fi
+
+
+if [[ "$ALLOW_SSH_PUBLIC_IN" == "true" ]]; then
+  SSH_PUBLIC_IN_RULE="$(cat <<EOF
+    iif "$EXT_IF" tcp dport 22 accept
+EOF
+)"
+fi
+
+if [[ "$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
+
+
+export EXT_IF PRIV_IF PRIV_NET
+export ICMP_PUBLIC_IN_RULES ICMP_PUBLIC_OUT_RULES
+export SSH_PUBLIC_IN_RULE APT_PUBLIC_OUT_RULES
+
+########################
+# Render
+########################
+TMP="$(mktemp -p /run nft-fw.XXXXXX)"
+trap 'rm -f "$TMP"' EXIT
+
+envsubst < /etc/nftables.conf.in > "$TMP"
+
+########################
+# Remove only our table (do NOT touch fail2ban)
+########################
+nft delete table inet fw_static 2>/dev/null || true
+
+########################
+# Validate + apply
+########################
+nft -c -f "$TMP"
+
+if [[ "$DO_APPLY" == "true" ]]; then
+  nft -f "$TMP"
+  install -m 600 "$TMP" /etc/nftables.conf
+else
+  echo ""
+  echo "   fw-apply: check mode"
+  [[ -r "$CFG" ]] && echo "      - config loaded: $CFG" || echo "      - config loaded: defaults only"
+  echo "      - rendered nftables ruleset: OK"
+  echo "      - syntax check (nft -c): OK"
+  echo "      - no changes applied"
+  echo ""
+fi