AppImage type detection wrong

[probonopd]

As per the AppImageSpec, currently there are only two image formats: Types 1 and 2.

• Type 1 can be identified by checking for the magic hex 0x414901 at offset 8.
• Type 2 can be identified by checking for the magic hex 0x414902 at offset 8.

So why is this talking about a type 3 then? And why is it grepping for the string AppImages require FUSE to run? You should read the AppImageSpec more, instead of just making assumptions that may or may not happen to be true sometimes.

https://github.com/ivan-hc/AM/blob/6f29f8ee059a55eaa66544f928d0817205ec4e0e/modules/files.am#L68-L82

To get the image type, you might use something like this (untested):

#!/bin/sh

get_appimage_type() {
  local file_path=$1
  local content_type=$(file --mime-type -b "$file_path")

  # Check the magic bytes to determine the AppImage type
  if [ -f "$file_path" ]; then
    magic=$(dd bs=1 skip=8 count=4 if="$file_path" 2>/dev/null)
    case $magic in
      $'\x41\x49\x01') echo 1; return;;
      $'\x41\x49\x02') echo 2; return;;
    esac
  fi

  # If we couldn't determine the type, return 0 as default
  echo 0
}

Related:

• https://github.com/mijorus/gearlever/issues/132

[ivan-hc]

@probonopd I want to update you about the status of "AM" right now:

• with release 7.5 we have separated "AppImages" from "other portable apps" in lists and queries https://github.com/ivan-hc/AM/releases/tag/7.5
• with release 7.6 we have improved lists with more info about each app https://github.com/ivan-hc/AM/releases/tag/7.6 and also added categories for our catalog (and maybe future "AM" GUI frontend) https://portable-linux-apps.github.io/apps including a page that lists only AppImages https://portable-linux-apps.github.io/appimages
• release 7.6.1 has nothing that can be related directly to this issue https://github.com/ivan-hc/AM/releases/tag/7.6.1
• with release 7.6.2 we removed the the appimage2 and appimage3 names and just named them "appimage", and added an asterisk in case the listed AppImage still require libfuse2 https://github.com/ivan-hc/AM/releases/tag/7.6.2 we have not applied the function you suggested at start because Type1 and Type2 AppImages are both depending on libfuse2, so for our workflows, they are equal. All our interest is for future releases, the Type0 you said here https://github.com/ivan-hc/AM/pull/843 and the focus of "AM" in the options that do this kind of distinction are focused on get rid of libfuse2, may the AppImage using a development build model or not. About the way we will detect if they are old AppImage models or not, its something we will determine in future releases, by following future improvements in your tools. We focus our work on that
• finally, release 7.7 will check the installation scripts we have, to determine if an AppImage, or any kind of program, is "trustable", all depend on how much the build process is transparent https://github.com/ivan-hc/AM/releases/tag/7.7 and this should answer your request at https://github.com/ivan-hc/AM/issues/818#issuecomment-2274918524, thank you for pointing us on this issue. Now it's just a matter of marking the scripts of those apps that have a "dubious" and "non-transparent" construction. Our users will mark these scripts, verifying whether the apps are reliable or not. As maintainers of this package manager, we can only rely on the feedback of our users, to be able to improve.

I hope that the work done in the last week, mostly based on your doubts about our project, is sufficiently exhaustive.

If you have other requests to make or other suggestions, you are welcome.

[probonopd]

Thank you very much, appreciate it @ivan-hc.