I’m attempting to integrate some AD stuff with my app, but I’m stuck on how to use the GUID that is returned with Ecto. From exldap, I get this back: 'objectGUID' => [ [219, 12, 193, 79, 151, 81, 153, 75, 128, 88, 23, 96, 59, 10, 33, 175] ] which is fine, except if I try and load it with Ecto…

This was a cool little problem! First step, find the “correct” format of the expected UUID “4FC10CDB-5197-4B99-8058-17603B0A21AF” iex(50)> Ecto.UUID.dump("4FC10CDB-5197-4B99-8058-17603B0A21AF") {:ok, <<79, 193, 12, 219, 81, 151, 75, 153, 128, 88, 23, 96, 59, 10, 33, 175>>} Hmmm, some of those num…

Thank you!! I spent so long looking at it, I couldn’t see that the first 3 parts were reversed! :blush: Which with some googling leads to: Variant bits aside, the two variants are the same except that when reduced to a binary form for storage or transmission, variant 1 UUIDs use “network” (big-e…

So that has now lead me to this: (Thanks to this post on mixed endian binaries - Pete Corey - Building Mixed Endian Binaries with Elixir ) iex(65)> << a::32, b::16, c::16, d::16, e::48 >> = [219, 12, 193, 79, 151, 81, 153, 75, 128, 88, 23, 96, 59, 10, 33, 175] |> :binary.list_to_bin <<219, 12, 193, …

And all this means that somewhere, they’re getting converted to/from integers by code which is not aware of the different byte-ordering between variants. My guess is Ecto, might be worth a bug report…

Yea, I was wondering if it was Exldap (which calls out to eldap) as that is where the list came from, or if it is Ecto as it is not making sure that the endians are correct. I’ll have a play in a bit with some other UUID libs and see if I can come up with where the issue is Edit: Thinking about i…

[image] benperiton: so yea would seem more likely that Ecto is not checking endiness. ‘How’ would it check that?

I would hope there would be bits specifying the variant at a fixed location, octet-wise, and they would include that. But of course this is MS we’re talking about, so who knows. (A few minutes with google produced a lot of discussions but no real answer.)

So for completeness, this is the issue I raised: Endiness check for UUIDs · Issue #2660 · elixir-ecto/ecto · GitHub Basic gist is that there is a difference between a UUID and a GUID (I always assumed they were the same) - that difference being the endiness, so it’s not really down to Ecto. I’m ju…

FYI, it’s not at all clear from what I’ve read that GUID’s are always little-endian–it may depend on the source.

Elixir Programming Language Forum

Using Active Directory GUID with Ecto UUID field

Questions & Help Questions

axelson August 17, 2018, 9:40pm 4

Awesome, I’m glad it’s helpful!