#!/bin/bash
# SPDX-Version: 3.0
# SPDX-CreationInfo: 2025-10-11; WEIDNER, Marc S.; <msw@coresecret.dev>
# SPDX-ExternalRef: GIT https://git.coresecret.dev/msw/CISS.debian.live.builder.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: LicenseRef-CNCL-1.1 OR LicenseRef-CCLA-1.1
# SPDX-LicenseComment: This file is part of the CISS.debian.installer.secure framework.
# SPDX-PackageName: CISS.debian.live.builder
# SPDX-Security-Contact: security@coresecret.eu
set -Ceuo pipefail

printf "\e[95m🧪 '%s' starting ... \e[0m\n" "${0}"

[[ -r /root/ciss_xdg_tmp.sh ]] && . /root/ciss_xdg_tmp.sh
export DEBIAN_FRONTEND="noninteractive"
export INITRD="No"

declare SOPS_COSIGN_CERTIFICATE_IDENTITY_REGEXP="https://github.com/getsops"
declare SOPS_COSIGN_CERTIFICATE_OIDC_ISSUER="https://token.actions.githubusercontent.com"

#######################################
# Print a fatal error and abort the hook.
# Globals:
#   None
# Arguments:
#   1: Message string
# Returns:
#   None
#######################################
die() {
  declare message="$1"
  printf "\e[91m❌ ERROR: %s \e[0m\n" "${message}" >&2
  exit 43
}

#######################################
# Require an executable tool.
# Globals:
#   None
# Arguments:
#   1: Tool name
# Returns:
#   0: on success
#######################################
require_tool() {
  declare tool_name="$1"

  command -v "${tool_name}" >/dev/null 2>&1 || die "Required tool not found: ${tool_name}"

  return 0
}

#######################################
# Validate and normalize a SOPS semantic version.
# Globals:
#   None
# Arguments:
#   1: SOPS version string
# Outputs:
#   Normalized bare semantic version
# Returns:
#   0: on success
#######################################
normalize_sops_version() {
  declare sops_version="${1#v}"

  [[ "${sops_version}" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]] || \
    die "Invalid SOPS version '${1}'. Expected '<MAJOR>.<MINOR>.<PATCH>' without prerelease metadata."

  printf '%s' "${sops_version}"

  return 0
}

#######################################
# Download a mandatory release asset.
# Globals:
#   None
# Arguments:
#   1: Asset URL
#   2: Target filename
# Returns:
#   0: on success
#######################################
download_required_asset() {
  declare asset_url="$1"
  declare target_file="$2"

  if ! curl -fsSLo "${target_file}" "${asset_url}"; then
    die "Failed to download required SOPS asset '${target_file}' from '${asset_url}'."
  fi

  [[ -s "${target_file}" ]] || die "Downloaded SOPS asset is empty: ${target_file}"

  return 0
}

#######################################
# Download an optional release asset and distinguish absence from download errors.
# Globals:
#   None
# Arguments:
#   1: Asset URL
#   2: Target filename
# Returns:
#   0: asset was downloaded
#   1: asset is absent upstream
#######################################
download_optional_asset() {
  declare asset_url="$1"
  declare target_file="$2"
  declare http_code=""

  if ! http_code=$(curl -sSLo "${target_file}" -w '%{http_code}' "${asset_url}"); then
    rm -f -- "${target_file}"
    die "Failed to query optional SOPS asset '${target_file}' from '${asset_url}'."
  fi

  case "${http_code}" in
    200)
      [[ -s "${target_file}" ]] || die "Optional SOPS asset is empty after HTTP 200: ${target_file}"
      return 0
      ;;
    404)
      rm -f -- "${target_file}"
      return 1
      ;;
    *)
      rm -f -- "${target_file}"
      die "Unexpected HTTP status ${http_code} for optional SOPS asset '${target_file}' from '${asset_url}'."
      ;;
  esac
}

#######################################
# Verify the SOPS checksums file with Cosign.
# Globals:
#   SOPS_COSIGN_CERTIFICATE_IDENTITY_REGEXP
#   SOPS_COSIGN_CERTIFICATE_OIDC_ISSUER
# Arguments:
#   1: Checksums filename
#   2: Bundle filename
#   3: Certificate filename
#   4: Signature filename
# Returns:
#   0: on success
#######################################
verify_sops_checksums_signature() {
  declare checksums_file="$1"
  declare bundle_file="$2"
  declare certificate_file="$3"
  declare signature_file="$4"

  if [[ -f "${bundle_file}" ]]; then
    printf "\e[95m[INFO] Verifying SOPS checksums with Cosign bundle: %s \e[0m\n" "${bundle_file}"
    cosign verify-blob "${checksums_file}" \
      --bundle "${bundle_file}" \
      --certificate-identity-regexp="${SOPS_COSIGN_CERTIFICATE_IDENTITY_REGEXP}" \
      --certificate-oidc-issuer="${SOPS_COSIGN_CERTIFICATE_OIDC_ISSUER}" || \
      die "SOPS checksum signature verification failed in bundle mode for '${checksums_file}' using '${bundle_file}'."
    return 0
  fi

  if [[ -f "${certificate_file}" && -f "${signature_file}" ]]; then
    printf "\e[95m[INFO] Verifying SOPS checksums with Cosign split certificate/signature: %s %s \e[0m\n" "${certificate_file}" "${signature_file}"
    cosign verify-blob "${checksums_file}" \
      --certificate "${certificate_file}" \
      --signature "${signature_file}" \
      --certificate-identity-regexp="${SOPS_COSIGN_CERTIFICATE_IDENTITY_REGEXP}" \
      --certificate-oidc-issuer="${SOPS_COSIGN_CERTIFICATE_OIDC_ISSUER}" || \
      die "SOPS checksum signature verification failed in legacy split mode for '${checksums_file}' using '${certificate_file}' and '${signature_file}'."
    return 0
  fi

  if [[ -f "${certificate_file}" || -f "${signature_file}" ]]; then
    die "Incomplete legacy SOPS signature layout for '${checksums_file}'. Expected both '${certificate_file}' and '${signature_file}'."
  fi

  die "No supported SOPS checksum signature layout found for '${checksums_file}'. Expected bundle or split certificate/signature assets."
}

#######################################
# Verify the SOPS artifact checksum and ensure the expected artifact was covered.
# Globals:
#   None
# Arguments:
#   1: Checksums filename
#   2: Artifact filename
# Returns:
#   0: on success
#######################################
verify_sops_artifact_checksum() {
  declare checksums_file="$1"
  declare artifact_file="$2"
  declare checksum_output=""

  if ! checksum_output=$(sha256sum -c "${checksums_file}" --ignore-missing 2>&1); then
    printf '%s\n' "${checksum_output}" >&2
    die "SOPS artifact checksum verification failed for '${artifact_file}' using '${checksums_file}'."
  fi

  printf '%s\n' "${checksum_output}"

  if ! grep -Fxq "${artifact_file}: OK" <<< "${checksum_output}" && \
     ! grep -Fxq "./${artifact_file}: OK" <<< "${checksum_output}"; then
    die "SOPS checksum verification did not cover expected artifact '${artifact_file}' from '${checksums_file}'."
  fi

  return 0
}

#######################################
# Install SOPS from an upstream GitHub release after signature and checksum verification.
# Globals:
#   CISS_SOPS_VERSION
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
main() {
  require_tool curl
  require_tool cosign
  require_tool sha256sum

  declare sops_env="/root/sops.env"
  [[ -r "${sops_env}" ]] || die "Missing SOPS environment file: ${sops_env}"

  # shellcheck disable=SC1090
  . "${sops_env}"

  declare ciss_sops_version
  ciss_sops_version=$(normalize_sops_version "${CISS_SOPS_VERSION:?CISS_SOPS_VERSION is not set}")

  declare architecture
  architecture="$(dpkg --print-architecture)"

  declare sops_tag="v${ciss_sops_version}"
  declare sops_file=""
  case "${architecture}" in
    amd64)
      sops_file="sops-${sops_tag}.linux.amd64"
      ;;
    arm64)
      sops_file="sops-${sops_tag}.linux.arm64"
      ;;
    *)
      die "Unsupported architecture '${architecture}' for SOPS version '${ciss_sops_version}'. Expected amd64 or arm64."
      ;;
  esac

  declare release_base_url="https://github.com/getsops/sops/releases/download/${sops_tag}"
  declare checksums_file="sops-${sops_tag}.checksums.txt"
  declare bundle_file="sops-${sops_tag}.checksums.sigstore.json"
  declare certificate_file="sops-${sops_tag}.checksums.pem"
  declare signature_file="sops-${sops_tag}.checksums.sig"
  declare bundle_available="false"
  declare certificate_available="false"
  declare signature_available="false"

  cd /tmp

  printf "\e[95m[INFO] Downloading SOPS %s asset: %s \e[0m\n" "${ciss_sops_version}" "${sops_file}"
  download_required_asset "${release_base_url}/${sops_file}" "${sops_file}"
  download_required_asset "${release_base_url}/${checksums_file}" "${checksums_file}"

  # shellcheck disable=SC2310
  if download_optional_asset "${release_base_url}/${bundle_file}" "${bundle_file}"; then
    bundle_available="true"
  fi

  if [[ "${bundle_available}" == "false" ]]; then
    # shellcheck disable=SC2310
    if download_optional_asset "${release_base_url}/${certificate_file}" "${certificate_file}"; then
      certificate_available="true"
    fi

    # shellcheck disable=SC2310
    if download_optional_asset "${release_base_url}/${signature_file}" "${signature_file}"; then
      signature_available="true"
    fi

    if [[ "${certificate_available}" != "${signature_available}" ]]; then
      die "Incomplete legacy SOPS signature assets for version '${ciss_sops_version}'. Expected both '${certificate_file}' and '${signature_file}'."
    fi
  fi

  verify_sops_checksums_signature "${checksums_file}" "${bundle_file}" "${certificate_file}" "${signature_file}"
  verify_sops_artifact_checksum "${checksums_file}" "${sops_file}"

  install -m 0755 "${sops_file}" /usr/local/bin/sops
  sops --version >| /root/.ciss/cdlb/log/sops.log
  age --version  >| /root/.ciss/cdlb/log/age.log

  rm -f -- "/tmp/${sops_file}"
  rm -f -- "/tmp/${checksums_file}"
  rm -f -- "/tmp/${bundle_file}"
  rm -f -- "/tmp/${certificate_file}"
  rm -f -- "/tmp/${signature_file}"

  if [[ -f /root/.config/sops/age/keys.txt ]]; then
    chmod 0400 /root/.config/sops/age/keys.txt
  fi

  printf "\e[92m✅ '%s' applied successfully. \e[0m\n" "${0}"

  return 0
}

if [[ "${CISS_SOPS_TEST_MODE:-false}" != "true" ]]; then
  main "$@"
  exit 0
fi

# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh