V8.00.000.2025.06.17

Signed-off-by: Marc S. Weidner <msw@coresecret.dev>

includes/target/etc/initramfs-tools/files/dropbear_fw.sh

@@ -0,0 +1,66 @@
+#!/bin/sh
+# SPDX-Version: 3.0
+# SPDX-CreationInfo: 2025-06-17; WEIDNER, Marc S.; <msw@coresecret.dev>
+# SPDX-ExternalRef: GIT https://git.coresecret.dev/msw/CISS.debian.installer.git
+# SPDX-FileContributor: WEIDNER, Marc S.; Centurion Intelligence Consulting Agency
+# SPDX-FileCopyrightText: 2024-2025; ZIMNOL, Andre H.; <git.cs@physnet.eu>
+# SPDX-FileType: SOURCE
+# SPDX-License-Identifier: EUPL-1.2 OR LicenseRef-CCLA-1.0
+# SPDX-LicenseComment: This file is part of the CISS.debian.installer.secure framework.
+# SPDX-PackageName: CISS.debian.installer
+# SPDX-Security-Contact: security@coresecret.eu
+
+# shellcheck shell=sh
+
+# Firewall script for Dropbear SSH inside initramfs.
+# This script runs at the "init-bottom" stage of the early boot process.
+#
+# It configures basic iptables rules to restrict SSH access to Dropbear
+# while the system is in the pre-boot phase (before root is decrypted).
+#
+# IPv6 is not supported in initramfs at this stage due to complexity.
+# Only trusted IPv4 addresses are allowed.
+
+PREREQ="dropbear"
+
+prereqs() { echo "${PREREQ}"; }
+
+case "$1" in
+  prereqs) prereqs; exit 0 ;;
+esac
+
+### Check if the firewall is enabled via the config file.
+DROPBEAR_FW_CONF="/etc/initramfs-tools/conf.d/dropbear_fw.cnf"
+if [ -f "${DROPBEAR_FW_CONF}" ]; then
+  # shellcheck disable=SC1090
+  . "${DROPBEAR_FW_CONF}"
+else
+  DROPBEAR_FIREWALL_ENABLED=0
+fi
+
+### Abort if the firewall flag is not set or disabled.
+if [ "${DROPBEAR_FIREWALL_ENABLED}" != "1" ]; then
+  echo "Dropbear firewall disabled by 'dropbear_fw.cnf'."
+  exit 0
+fi
+
+### Ensure iptables is available.
+if command -v iptables >/dev/null 2>&1; then
+
+  ### Reset any existing rules.
+  iptables -F
+  iptables -X
+
+  ### Default policy: block everything unless explicitly allowed.
+  iptables -P INPUT DROP
+  iptables -P FORWARD DROP
+  iptables -P OUTPUT ACCEPT
+
+  ### Allow local loopback.
+  iptables -A INPUT -i lo -j ACCEPT
+
+  ### Infrastructure host / Jump-Server / VPN-Exit-Node: only allow SSH from the specified IPv4.
+  iptables -A INPUT -p tcp --dport "${DROPBEAR_PORT}" -s "${DROPBEAR_JUMP_SERVER_IP}" -j ACCEPT
+
+fi
+# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh