How to validate files uploaded by user effectively?

How is it not wanting to work yet? What error did you get?

Hey I am getting this for this file upload:

%Plug.Upload{
  content_type: "application/pdf",
  filename: "random-grid.pdf",
  path: "/tmp/plug-1569/multipart-1569287514-743406783659766-2"
}

and I am trying to do this:

FileInfo.get_info(attachment.filename) 

I also tried to append the filename at the end of the path given here but I am getting the same result

error:

** (MimetypeParser.Exception) illegal characters "`"
        (mimetype_parser) lib/mimetype_parser.ex:14: MimetypeParser.parse!/2
        (file_info) lib/file_info/mime.ex:25: FileInfo.Mime.parse!/1
        (file_info) lib/file_info.ex:39: FileInfo.to_tuple/1
        (elixir) lib/stream.ex:565: anonymous fn/4 in Stream.map/2
        (elixir) lib/enum.ex:3317: Enumerable.List.reduce/3
        (elixir) lib/stream.ex:1568: Enumerable.Stream.do_each/4
        (elixir) lib/enum.ex:3015: Enum.reverse/1
        (elixir) lib/enum.ex:2647: Enum.to_list/1
        (elixir) lib/map.ex:181: Map.new_from_enum/1

I am getting hte same result for every single file.
The setup is the following, I am using ubuntu, and the project is running in a docker container if I run the file command inside the container it works.
If i run the project in iex mode and try to call

FileInfo.get_info/1

if I call it with files inside that very folder that i am in it works, I can get results like

%{"mix.lock" => %FileInfo.Mime{arguments: %{}, subtype: "plain", type: "text"}}

but with other files, outside this folder I can only get that same error from earlier

This for sure will not work… How do You append the file and path?

FileInfo.get_info("#{attachment.path}#{attachment.filename}")

You miss a slash in between, as I thought… the path is not valid without.

still doesnt want to work:

%Plug.Upload{
  content_type: "application/pdf",
  filename: "random-grid.pdf",
  path: "/tmp/plug-1569/multipart-1569289758-138513881763554-3"
}

FileInfo.get_info("#{attachment.path}/#{attachment.filename}")

getting the same error, but it did miss the slash so thank you for that

If i do just the underlying command:

System.cmd("file", ["--mime-type" | ["#{attachment.path}/#{attachment.filename}"]])

then the result is this:

{“/tmp/plug-1569/multipart-1569290249-648297072043659-1/random-grid.pdf: cannot open `/tmp/plug-1569/multipart-1569290249-648297072043659-1/random-grid.pdf’ (Not a directory)\n”,
0}

It is working fine on my pc with a pdf file…

iex> FileInfo.get_info "/Users/koko/downloads/MarcAurelePensees.pdf"
%{
  "/Users/koko/downloads/MarcAurelePensees.pdf" => %FileInfo.Mime{
    arguments: %{},
    subtype: "pdf",
    type: "application"
  }
}

But your error seems to be a non existant file… You should check first if the file exists.

File.exists? ...

ok, that says it doesn’t exist, but then how can plug and arc give a path to it and upload it?

From docs…

Note: This file is temporary, and Plug will remove it from the directory as the request completes. If we need to do anything with this file, we need to do it before then.