mkarchiso: Add buildmode to export netboot artifacts

archiso/mkarchiso:
Implement a buildmode to export artifacts required for netboot with IPXE.
When providing the buildmode 'netboot' via profiledef.sh or the `-m` option, all targets necessary to create an ISO
medium are built, but the components required for netboot are exported to the output dir.
Optionally, it is possible to provide a set of certificates for codsigning using the `-c` option, where the first file
is considered as the signer certificate and the second as the key.

Add `_export_netboot_artifacts()` to copy build artifacts to the output directory.
Add `_sign_netboot_artifacts()` to codesign the netboot artifacts in the work directory.
Add `_validate_requirements_buildmode_netboot()` to check for openssl.
Add `_build_iso_base()` to implement common function calls between the 'iso' and the 'netboot' buildmodes.
Add `_build_buildmode_netboot()` to make use of `_build_iso_base()`, (optionally) `_sign_netboot_artifacts()` and
`_export_netboot_artifacts()`.
Change `_build_buildmode_iso()` to make use of `_build_iso_base()`.
Add `-c` as an option to mkarchiso to read in a list of file names.
Unify the output of `_usage()` by using the same definition style for lists of strings provided to options that accept
them (e.g. `-c`, `-m`, `-p`).

Closes #128

archiso/mkarchiso

@@ -34,6 +34,8 @@ buildmodes=()
 bootmodes=()
 airootfs_image_type=""
 airootfs_image_tool_options=()
+cert_list=()
+sign_netboot_artifacts=""
 declare -A file_permissions=()
 
 
@@ -96,13 +98,17 @@ usage: ${app_name} [options] <profile_dir>
                       Default: '${iso_label}'
      -P <publisher>   Set the ISO publisher
                       Default: '${iso_publisher}'
+     -c [cert ..]     Provide certificates for codesigning of netboot artifacts
+                      Multiple files are provided as quoted, space delimited list.
+                      The first file is considered as the signing certificate,
+                      the second as the key.
      -g <gpg_key>     Set the PGP key ID to be used for signing the rootfs image
      -h               This message
-     -m [build modes] Build modes to use (valid modes are: 'bootstrap' and 'iso').
+     -m [mode ..]     Build mode(s) to use (valid modes are: 'bootstrap', 'iso' and 'netboot').
                       Multiple build modes are provided as quoted, space delimited list.
      -o <out_dir>     Set the output directory
                       Default: '${out_dir}'
-     -p PACKAGE(S)    Package(s) to install.
+     -p [package ..]  Package(s) to install.
                       Multiple packages are provided as quoted, space delimited list.
      -v               Enable verbose output
      -w <work_dir>    Set the working directory
@@ -127,6 +133,7 @@ _show_config() {
     _msg_info "       Current build mode:   ${buildmode}"
     _msg_info "              Build modes:   ${buildmodes[*]}"
     _msg_info "                  GPG key:   ${gpg_key:-None}"
+    _msg_info "Code signing certificates:   ${cert_list[*]}"
     _msg_info "                  Profile:   ${profile}"
     _msg_info "Pacman configuration file:   ${pacman_conf}"
     _msg_info "          Image file name:   ${image_name:-None}"
@@ -650,6 +657,34 @@ _prepare_airootfs_image() {
     fi
 }
 
+# export build artifacts for netboot
+_export_netboot_artifacts() {
+    _msg_info "Exporting netboot artifacts..."
+    install -d -m 0755 "${out_dir}"
+    cp -a -- "${isofs_dir}/${install_dir}/" "${out_dir}/"
+    _msg_info "Done!"
+    du -h -- "${out_dir}/${install_dir}"
+}
+
+# sign build artifacts for netboot
+_sign_netboot_artifacts() {
+    local _file _dir
+    _msg_info "Signing netboot artifacts..."
+    _dir="${isofs_dir}/${install_dir}/"
+    for _file in "${_dir}/boot/"*ucode.img "${_dir}/boot/${arch}/vmlinuz-"* "${_dir}/boot/${arch}/initramfs-"*.img; do
+        openssl cms \
+            -sign \
+            -binary \
+            -noattr \
+            -in "${_file}" \
+            -signer "${cert_list[0]}" \
+            -inkey "${cert_list[1]}" \
+            -outform DER \
+            -out "${_file}".ipxe.sig
+    done
+    _msg_info "Done!"
+}
+
 _validate_requirements_airootfs_image_type_squashfs() {
     if ! command -v mksquashfs &> /dev/null; then
         (( validation_error=validation_error+1 ))
@@ -703,6 +738,14 @@ _validate_requirements_buildmode_iso() {
     fi
 }
 
+_validate_requirements_buildmode_netboot() {
+    _validate_requirements_buildmode_all
+    if ! command -v openssl &> /dev/null; then
+        (( validation_error=validation_error+1 ))
+        _msg_error "Validating build mode '${_buildmode}': openssl is not available on this host. Install 'openssl'!" 0
+    fi
+}
+
 # SYSLINUX El Torito
 _add_xorrisofs_options_bios.syslinux.eltorito() {
     xorrisofs_options+=(
@@ -884,9 +927,10 @@ _read_profile() {
 
 # Validate set options
 _validate_options() {
-    local validation_error=0 bootmode _buildmode
+    local validation_error=0 bootmode _cert _buildmode
     local pkg_list_from_file=()
     local bootstrap_pkg_list_from_file=()
+    local _override_cert_list=()
 
     _msg_info "Validating options..."
     # Check if the package list file exists and read packages from it
@@ -917,7 +961,23 @@ _validate_options() {
             _msg_error "Bootstrap packages file '${bootstrap_packages}' does not exist." 0
         fi
     fi
-
+    if [[ "${sign_netboot_artifacts}" == "y" ]]; then
+        # Check if the certificate files exist
+        for _cert in "${cert_list[@]}"; do
+            if [[ -e "${_cert}" ]]; then
+                _override_cert_list+=("$(realpath -- "${_cert}")")
+            else
+                (( validation_error=validation_error+1 ))
+                _msg_error "File '${_cert}' does not exist." 0
+            fi
+        done
+        cert_list=("${_override_cert_list[@]}")
+        # Check if there are at least two certificate files
+        if (( "${#cert_list[@]}" < 2 )); then
+            (( validation_error=validation_error+1 ))
+            _msg_error "Two certificates are required for codesigning, but '${cert_list[*]}' is provided." 0
+        fi
+    fi
     # Check if pacman configuration file exists
     if [[ ! -e "${pacman_conf}" ]]; then
         (( validation_error=validation_error+1 ))
@@ -1017,6 +1077,10 @@ _set_overrides() {
         install_dir="${app_name}"
     fi
     [[ ! -v override_gpg_key ]] || gpg_key="$override_gpg_key"
+    if [[ -v override_cert_list ]]; then
+        sign_netboot_artifacts="y"
+    fi
+    [[ ! -v override_cert_list ]] || cert_list+=("${override_cert_list[@]}")
     if [[ -v override_quiet ]]; then
         quiet="$override_quiet"
     elif [[ -z "$quiet" ]]; then
@@ -1079,38 +1143,15 @@ _make_pkglist() {
     _msg_info "Done!"
 }
 
-_build_buildmode_bootstrap() {
+# build the base for an ISO and/or a netboot target
-    local image_name="${iso_name}-bootstrap-${iso_version}-${arch}.tar.gz"
+_build_iso_base() {
-    local run_once_mode="${buildmode}"
+    local run_once_mode="base"
-    local buildmode_packages="${bootstrap_packages}"
-    local buildmode_pkg_list=()
-
-    # Set the package list to use
-    buildmode_pkg_list=("${bootstrap_pkg_list[@]}")
-    # Set up essential directory paths
-    pacstrap_dir="${work_dir}/${arch}/bootstrap/root.${arch}"
-    [[ -d "${work_dir}" ]] || install -d -- "${work_dir}"
-    install -d -m 0755 -o 0 -g 0 -- "${pacstrap_dir}"
-
-    [[ "${quiet}" == "y" ]] || _show_config
-    _run_once _make_pacman_conf
-    _run_once _make_packages
-    _run_once _make_version
-    _run_once _make_pkglist
-    _run_once _cleanup_pacstrap_dir
-    _run_once _build_bootstrap_image
-}
-
-_build_buildmode_iso() {
-    local image_name="${iso_name}-${iso_version}-${arch}.iso"
-    local run_once_mode="${buildmode}"
     local buildmode_packages="${packages}"
-    local buildmode_pkg_list=()
+    # Set the package list to use
+    local buildmode_pkg_list=("${pkg_list[@]}")
     # Set up essential directory paths
     pacstrap_dir="${work_dir}/${arch}/airootfs"
     isofs_dir="${work_dir}/iso"
-    # Set the package list to use
-    buildmode_pkg_list=("${pkg_list[@]}")
 
     # Create working directory
     [[ -d "${work_dir}" ]] || install -d -- "${work_dir}"
@@ -1132,6 +1173,46 @@ _build_buildmode_iso() {
     _make_bootmodes
     _run_once _cleanup_pacstrap_dir
     _run_once _prepare_airootfs_image
+}
+
+# Build the bootstrap buildmode
+_build_buildmode_bootstrap() {
+    local image_name="${iso_name}-bootstrap-${iso_version}-${arch}.tar.gz"
+    local run_once_mode="${buildmode}"
+    local buildmode_packages="${bootstrap_packages}"
+    # Set the package list to use
+    local buildmode_pkg_list=("${bootstrap_pkg_list[@]}")
+
+    # Set up essential directory paths
+    pacstrap_dir="${work_dir}/${arch}/bootstrap/root.${arch}"
+    [[ -d "${work_dir}" ]] || install -d -- "${work_dir}"
+    install -d -m 0755 -o 0 -g 0 -- "${pacstrap_dir}"
+
+    [[ "${quiet}" == "y" ]] || _show_config
+    _run_once _make_pacman_conf
+    _run_once _make_packages
+    _run_once _make_version
+    _run_once _make_pkglist
+    _run_once _cleanup_pacstrap_dir
+    _run_once _build_bootstrap_image
+}
+
+# Build the netboot buildmode
+_build_buildmode_netboot() {
+    local run_once_mode="${buildmode}"
+
+    _run_once _build_iso_base
+    if [[ -v cert_list ]]; then
+        _run_once _sign_netboot_artifacts
+    fi
+    _run_once _export_netboot_artifacts
+}
+
+# Build the ISO buildmode
+_build_buildmode_iso() {
+    local image_name="${iso_name}-${iso_version}-${arch}.iso"
+    local run_once_mode="${buildmode}"
+    _run_once _build_iso_base
     _run_once _build_iso_image
 }
 
@@ -1145,7 +1226,7 @@ _build() {
     done
 }
 
-while getopts 'p:C:L:P:A:D:w:m:o:g:vh?' arg; do
+while getopts 'c:p:C:L:P:A:D:w:m:o:g:vh?' arg; do
     case "${arg}" in
         p) read -r -a override_pkg_list <<< "${OPTARG}" ;;
         C) override_pacman_conf="${OPTARG}" ;;
@@ -1153,6 +1234,7 @@ while getopts 'p:C:L:P:A:D:w:m:o:g:vh?' arg; do
         P) override_iso_publisher="${OPTARG}" ;;
         A) override_iso_application="${OPTARG}" ;;
         D) override_install_dir="${OPTARG}" ;;
+        c) read -r -a override_cert_list <<< "${OPTARG}" ;;
         w) override_work_dir="${OPTARG}" ;;
         m) read -r -a override_buildmodes <<< "${OPTARG}" ;;
         o) override_out_dir="${OPTARG}" ;;