fix(installer-factory): Use the given path of the base ISO

The path was resolved against /output via basename, so a base ISO
anywhere else failed with "Installer ISO not found". tool.sh now mounts
it read-only at a path of its own.

Also refuse a base ISO that resolves to the output file: xorriso would
read and write one file, which is reachable because the output name is
derived from the configuration.

Signed-off-by: Simon Walz <contact@simonwalz.de>

Author: simonwalz

installer-factory/patch_iso.sh

@@ -20,16 +20,31 @@ if [[ ! -d "${OUTPUT_DIR}" ]]; then
   exit 1
 fi
 
-BASE_INSTALLER="${OUTPUT_DIR}/$(basename "$1")"
-if [[ -z "${BASE_INSTALLER}" || ! -f "${BASE_INSTALLER}" ]]; then
-  echo "Error: Installer ISO not found." >&2
+# The base ISO is mounted into the container at a path of its own - tool.sh
+# mounts it read-only at /base.iso - so the given path is used as-is.
+BASE_INSTALLER="$1"
+if [[ -z "${BASE_INSTALLER}" ]]; then
+  echo "Error: No base installer ISO given." >&2
+  exit 1
+fi
+if [[ ! -f "${BASE_INSTALLER}" ]]; then
+  echo "Error: Installer ISO not found: ${BASE_INSTALLER}" >&2
   exit 1
 fi
 
 IMAGE_NAME="${IMAGE_NAME:-"installer"}"
 INSTALLER="${OUTPUT_DIR}/${IMAGE_NAME}.iso"
 CONFIG_PATH="${OUTPUT_DIR}/${IMAGE_NAME}.json"
 
+# xorriso reads -indev and writes -outdev. If they resolve to the same file the
+# result is undefined. The output name is derived from the configuration, so
+# deriving from an ISO built with that same configuration lands on its own path.
+if [[ "$(realpath "${BASE_INSTALLER}")" == "$(realpath -m "${INSTALLER}")" ]]; then
+  echo "Error: base installer and output are the same file: ${INSTALLER}" >&2
+  echo "       This writes a new ISO; it does not modify the base one." >&2
+  exit 1
+fi
+
 #xorriso -indev /output/CuOS-IaC-cuos-test.iso -ls /
 
 xorriso \