#!/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

#######################################
# Configure target system for chroot.
# Globals:
#   ERR_CHRT_MOUNTS
#   TARGET
#   VAR_CHROOT_ACTIVATED
#   VAR_NEED_RUN_IN_TARGET
# Arguments:
#   None
# Returns:
#   ERR_CHRT_MOUNTS
#   0: on success
#######################################
configure_system() {

  ### Notes
  # This file mounts all necessary pseudo filesystems into the target root environment to enable chroot operations.
  # --rbind: recursive binding.
  # --make-rslave: In this case, the mount point is marked as 'slave'.
  # This means changes to the source mount (e.g., /proc) are propagated to the target mount (e.g., "${TARGET}/proc").
  # Conversely, changes to the target mount are not propagated back to the source mount.
  # This mode is necessary to avoid problems with double or erroneous propagation effects in chroot or container environments.
  #
  # Some subdirectories (such as /dev/pts, /dev/shm, /sys/fs/cgroup) are remounted with more restrictive options
  # like 'noexec', 'nosuid', and 'nodev' to enhance security. This ensures they override the inherited bind-mounts and
  # enforce proper runtime behavior in the chroot.

  ### Declare Arrays, HashMaps, and Variables.
  declare -A  HMP_SPECIAL_MOUNTS=(
    ["/dev/pts"]="devpts devpts noexec,nosuid"                           ### Mount 'devpts' (used by pseudo-terminals).
    ["/dev/shm"]="tmpfs tmpfs rw,nosuid,nodev"                           ### Mount 'tmpfs' for '/dev/shm' (shared memory).
    ["/dev/mqueue"]="mqueue mqueue rw,nosuid,nodev,noexec"               ### Mount 'mqueue' for POSIX message queues.
    ["/dev/hugepages"]="hugetlbfs hugetlbfs rw,nosuid,nodev"             ### Mount 'hugetlbfs' (huge pages, may be unused but required on some 'archs').
    ["/sys/fs/cgroup"]="cgroup2 cgroup2 rw,nosuid,nodev,noexec,relatime" ### Mount unified 'cgroup2' hierarchy.
  )

  declare -a  ary_mount=( "/proc" "/sys" "/dev" )
  declare     var_src="" var_dst="" var_path="" var_fs="" var_opts=""

  for var_path in "${ary_mount[@]}" "${!HMP_SPECIAL_MOUNTS[@]}"; do

    mkdir -p "${TARGET}${var_path}"

  done

  for var_src in "${ary_mount[@]}"; do
    var_dst="${TARGET}${var_src}"

    if ! mount --make-rslave --rbind "${var_src}" "${var_dst}"; then

      do_log "emergency" "file_only" "4020() Command: [mount --make-rslave --rbind ${var_src} ${var_dst}] failed."
      return "${ERR_CHRT_MOUNTS}"

    fi

    do_log "info" "file_only" "4020() Command: [mount --make-rslave --rbind ${var_src} ${var_dst}] successful."

  done

  if [[ "${VAR_NEED_RUN_IN_TARGET:-false}" == "true" ]]; then

    mkdir -p "${TARGET}/run"

    if ! mount --make-rslave --rbind /run "${TARGET}/run"; then

      do_log "emergency" "file_only" "4020() Command: [mount --make-rslave --rbind /run ${TARGET}/run] failed."
      return "${ERR_CHRT_MOUNTS}"

    fi

    do_log "info" "file_only" "4020() Command: [mount --make-rslave --rbind /run ${TARGET}/run] successful."

  fi

  for var_path in "${!HMP_SPECIAL_MOUNTS[@]}"; do

    IFS=" " read -r var_fs var_src var_opts <<< "${HMP_SPECIAL_MOUNTS[${var_path}]}"

    if ! mount -t "${var_fs}" "${var_src}" "${TARGET}${var_path}" -o "${var_opts}"; then

      do_log "emergency" "file_only" "4020() Command: [mount -t ${var_fs} ${var_src} ${TARGET}${var_path} -o ${var_opts}] failed."
      return "${ERR_CHRT_MOUNTS}"

    else

      do_log "info" "file_only" "4020() Command: [mount -t ${var_fs} ${var_src} ${TARGET}${var_path} -o ${var_opts}] successful."

    fi

  done

  if ! do_in_target "${TARGET}" mkdir -p /etc/systemd/system/multi-user.target.wants; then

    do_log "emergency" "file_only" "4020() Command: [do_in_target ${TARGET} mkdir -p /etc/systemd/system/multi-user.target.wants] failed."
    return "${ERR_CHRT_MOUNTS}"

  else

    do_log "info" "file_only" "4020() Command: [do_in_target ${TARGET} mkdir -p /etc/systemd/system/multi-user.target.wants] successful."

  fi

  # shellcheck disable=SC2034
  declare -gx VAR_CHROOT_ACTIVATED="system"

  return 0
}
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