#!/bin/bash
# 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; WEIDNER, Marc S.; <msw@coresecret.dev>
# 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

guard_sourcing || return "${ERR_GUARD_SOURCE}"

#######################################
# Build Ultra Hardened dropbear from sources.
# Globals:
#   TARGET
#   VAR_SETUP_PATH
# Arguments:
#   None
# Returns:
#   0: on success
#   126: on permission, noexec, or interpreter execution failure
#   127: on missing build command
#   ERR_PATH_NOT_VALID: on failure
#######################################
dropbear_build() {
  ### Declare Arrays, HashMaps, and Variables.
  declare     var_dropbear_version="2026.91"
  declare     var_tar="${VAR_SETUP_PATH}/upgrades/dropbear/dropbear-${var_dropbear_version}.tar.bz2"
  declare     var_build_root="/opt/.ciss/build"
  declare     var_build_dir="${var_build_root}/dropbear-${var_dropbear_version}"
  declare -r  var_logfile="/root/.ciss/cdi/log/4310_dropbear_build.log"
  declare -r  var_build_log="${TARGET}${var_logfile}"
  declare -r  var_build_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
  declare     var_command="" var_command_path="" var_configure_interpreter="" var_configure_shebang=""
  declare     var_mount_options="" var_mount_target=""
  declare -a  ary_required_commands=(bash setsid musl-gcc make nproc)

  chroot_logger "${var_build_log}"

  mkdir -p "${var_build_root}"
  chmod 0700 "${var_build_root}"

  if ! PATH="${var_build_path}" command -v findmnt >/dev/null 2>&1; then
    do_log "error" "file_only" "4310() Required Dropbear build command missing from sterile PATH: 'findmnt'."
    return 127
  fi

  case "${var_build_dir}" in
    /opt/.ciss/build/dropbear-*) ;;
    *)
      do_log "error" "file_only" "4310() Refusing to clean unexpected Dropbear build directory: '${var_build_dir}'."
      return "${ERR_PATH_NOT_VALID}"
      ;;
  esac

  rm -rf -- "${var_build_dir}"
  tar xjf "${var_tar}" -C "${var_build_root}" || return "${ERR_PATH_NOT_VALID}"

  if [[ ! -d "${var_build_dir}" ]]; then
    do_log "error" "file_only" "4310() Dropbear build directory missing: '${var_build_dir}'."
    return "${ERR_PATH_NOT_VALID}"
  fi

  cp "${VAR_SETUP_PATH}/upgrades/dropbear/localoptions.h" "${var_build_dir}"

  if ! var_mount_target="$(PATH="${var_build_path}" findmnt -T "${var_build_dir}" -no TARGET)"; then
    do_log "error" "file_only" "4310() Cannot determine mount target for Dropbear build directory: '${var_build_dir}'."
    return "${ERR_PATH_NOT_VALID}"
  fi

  if ! var_mount_options="$(PATH="${var_build_path}" findmnt -T "${var_build_dir}" -no OPTIONS)"; then
    do_log "error" "file_only" "4310() Cannot determine mount options for Dropbear build directory: '${var_build_dir}'."
    return "${ERR_PATH_NOT_VALID}"
  fi

  if [[ ! -f "${var_build_dir}/configure" ]]; then
    do_log "error" "file_only" "4310() Dropbear configure script missing: '${var_build_dir}/configure'."
    return "${ERR_PATH_NOT_VALID}"
  fi

  if ! IFS= read -r var_configure_shebang < "${var_build_dir}/configure"; then
    do_log "error" "file_only" "4310() Cannot read Dropbear configure script: '${var_build_dir}/configure'."
    return "${ERR_PATH_NOT_VALID}"
  fi

  if [[ ! -x "${var_build_dir}/configure" ]]; then
    do_log "warn" "file_only" "4310() Dropbear configure script is not executable; correcting trusted source tree mode."
    chmod u+x "${var_build_dir}/configure" || return 126
  fi

  if [[ ! -x "${var_build_dir}/configure" ]]; then
    do_log "error" "file_only" "4310() Dropbear configure script is not executable: '${var_build_dir}/configure'."
    return 126
  fi

  (
    set -Ceuo pipefail
    PATH="${var_build_path}"
    export PATH
    cd "${var_build_dir}"
    printf '4310 Dropbear build preflight diagnostics\n'
    pwd
    id
    for var_command in bash setsid musl-gcc make nproc; do
      if var_command_path="$(command -v "${var_command}")"; then
        printf 'command -v %s: %s\n' "${var_command}" "${var_command_path}"
      else
        printf 'command -v %s: not found\n' "${var_command}"
      fi
    done
    findmnt -T .
    ls -ld .
    ls -l ./configure
    stat ./configure
    head -n 1 ./configure
  ) >> "${var_build_log}" 2>&1

  if [[ ",${var_mount_options}," == *,noexec,* ]]; then
    do_log "error" "file_only" "4310() Dropbear build directory is on a noexec mount: '${var_mount_target}' options '${var_mount_options}'. Use an exec-capable build directory."
    return 126
  fi

  if [[ "${var_configure_shebang}" != "#!"* ]]; then
    do_log "error" "file_only" "4310() Dropbear configure script has no interpreter line: '${var_build_dir}/configure'."
      return 126
  fi

  read -r var_configure_interpreter _ <<< "${var_configure_shebang#\#!}"
  if [[ "${var_configure_interpreter}" != /* || ! -x "${var_configure_interpreter}" ]]; then
    do_log "error" "file_only" "4310() Dropbear configure interpreter is not executable: '${var_configure_interpreter}'."
       return 126
  fi

  for var_command in "${ary_required_commands[@]}"; do
    if ! PATH="${var_build_path}" command -v "${var_command}" >/dev/null 2>&1; then
      do_log "error" "file_only" "4310() Required Dropbear build command missing from sterile PATH: '${var_command}'."
      return 127
    fi
  done

  ### Flag Purpose:
  #  -fPIE              : Generate position-independent executable code
  #  -pie               : Link the executable as PIE (so that ASLR works)
  #  -static            : Fully statically linked against musl
  #  -s                 : Strip unnecessary symbols directly during linking
  #  -Wl,-z,relro,-z,now: Enables full RELRO (symbol resolution at program startup)

  guard_trace on

  # shellcheck disable=SC2016,SC2312
  PATH="${var_build_path}" setsid bash -c '
    set -Ceuo pipefail
    ### Sterile environment for the build-process.
    export -n SHELLOPTS
    unset PATH_SEPARATOR
    PATH_SEPARATOR=":"
    export PATH_SEPARATOR
    PATH="${1}"
    export PATH
    cd "${2}"

    CC=musl-gcc \
      CFLAGS="-Os -fPIE -Wno-undef -fstack-protector-strong -D_FORTIFY_SOURCE=2" \
      LDFLAGS="-static -pie -s -Wl,-z,relro,-z,now" \
      ./configure \
      --enable-static \
      --enable-openpty \
      --disable-pam \
      --disable-zlib

    # shellcheck disable=2312
    make -j"$(nproc)"
  ' bash "${var_build_path}" "${var_build_dir}" >> "${var_build_log}" 2>&1

  guard_trace off

  guard_dir; return 0
}
### Prevents accidental 'unset -f'.
# shellcheck disable=SC2034
readonly -f dropbear_build
# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh