fix: Derive NT5 boot load size from extracted image (#1991)

src/image.sh

@@ -1044,43 +1044,53 @@ EOC
 getBootLoadSize() {
 
   local iso="$1"
-  local desc="$2"
-  local boot_info value
+  local dir="$2"
+  local desc="$3"
+  local boot_info size value
 
-  if ! boot_info=$(isoinfo -d -i "$iso"); then
+  case "${DETECTED,,}" in
+    "win2k"* | "winxp"* | "win2003"* )
 
-    case "${DETECTED,,}" in
-      "win2k"* | "winxp"* | "win2003"* )
-        BOOT_LOAD_SIZE=4
-        return 0
-        ;;
-    esac
+      if [ ! -s "$dir/$ETFS" ]; then
+        error "Failed to locate file \"$ETFS\" in $desc ISO image!"
+        return 1
+      fi
 
-    error "Failed to read boot image information from $desc ISO!"
-    return 1
-  fi
+      if ! size=$(stat -c%s "$dir/$ETFS"); then
+        error "Failed to determine boot image size from $desc ISO!"
+        return 1
+      fi
 
-  value=$(awk '/Nsect / { print $NF; exit }' <<< "$boot_info")
+      if (( size < 512 || size % 512 != 0 )); then
+        error "Invalid boot image size found in $desc ISO!"
+        return 1
+      fi
 
-  if [ -z "$value" ]; then
+      BOOT_LOAD_SIZE=$((size / 512))
+      ;;
 
-    case "${DETECTED,,}" in
-      "win2k"* | "winxp"* | "win2003"* )
-        BOOT_LOAD_SIZE=4
-        return 0
-        ;;
-    esac
+    * )
 
-    error "Failed to determine boot image load size from $desc ISO!"
-    return 1
-  fi
+      if ! boot_info=$(isoinfo -d -i "$iso"); then
+        error "Failed to read boot image information from $desc ISO!"
+        return 1
+      fi
 
-  if [[ ! "$value" =~ ^[0-9]+$ ]] || [ "${#value}" -gt 5 ]; then
-    error "Invalid boot image load size found in $desc ISO!"
-    return 1
-  fi
+      value=$(awk '/Nsect / { print $NF; exit }' <<< "$boot_info")
 
-  BOOT_LOAD_SIZE=$((10#$value))
+      if [ -z "$value" ]; then
+        error "Failed to determine boot image load size from $desc ISO!"
+        return 1
+      fi
+
+      if [[ ! "$value" =~ ^[0-9]+$ ]] || [ "${#value}" -gt 5 ]; then
+        error "Invalid boot image load size found in $desc ISO!"
+        return 1
+      fi
+
+      BOOT_LOAD_SIZE=$((10#$value))
+      ;;
+  esac
 
   if (( BOOT_LOAD_SIZE < 1 || BOOT_LOAD_SIZE > 65535 )); then
     error "Invalid boot image load size found in $desc ISO!"
@@ -1097,9 +1107,9 @@ extractBootImage() {
   local desc="$3"
 
   local tmp="$TMP/boot-images"
-  local max_size=$((32 * 1024 * 1024))
   local rc size offset image=""
   local msg="using legacy extraction..."
+  local expected_size=$((BOOT_LOAD_SIZE * 512))
   local boot_info
   local -a images=()
 
@@ -1130,8 +1140,8 @@ extractBootImage() {
         warn "The extracted BIOS boot image is empty, $msg"
       elif ! size=$(stat -c%s "$image"); then
         warn "Failed to determine the BIOS boot image size, $msg"
-      elif (( size > max_size )); then
-        warn "The extracted BIOS boot image exceeds 32 MB, $msg"
+      elif (( size != expected_size )); then
+        enabled "$DEBUG" && warn "The extracted BIOS boot image has an unexpected size, $msg"
       else
         if ! mv -f "$image" "$dir/$ETFS"; then
           rm -rf "$tmp" || true
@@ -1162,8 +1172,6 @@ extractBootImage() {
 
   rm -rf "$tmp" || true
 
-  local boot_info
-
   if ! boot_info=$(isoinfo -d -i "$iso"); then
     error "Failed to read boot image information from $desc ISO!"
     return 1
@@ -1184,9 +1192,9 @@ extractBootImage() {
   if ! dd \
       "if=$iso" \
       "of=$dir/$ETFS" \
-      bs=2048 \
+      bs=512 \
       "count=$BOOT_LOAD_SIZE" \
-      "skip=$offset" \
+      "skip=$((offset * 4))" \
       status=none; then
     rm -f "$dir/$ETFS" || true
     error "Failed to extract boot image from $desc ISO!"

src/install.sh

@@ -784,7 +784,7 @@ prepareImage() {
 
   if [[ "${BOOT_MODE,,}" == "windows_legacy" &&
     "${DETECTED,,}" != "win9"* ]]; then
-    getBootLoadSize "$iso" "$desc" || return 1
+    getBootLoadSize "$iso" "$dir" "$desc" || return 1
   fi
 
   skipVersion "$DETECTED" && return 0