How can i use jwto?

Learning
1

Hi. I am really OCaml beginner and i try to use Jwto.
Jwto(https://github.com/sporto/jwto)

I read README.md and try it.
But it does not work…
I want to simply encode and decode.

(* Encode *)
utop # let payload=[("user","koji")];;
val payload : (string * string) list = [("user", "koji")]  

utop # let encoded = Jwto.encode Jwto.HS256 "secret" payload;;
val encoded : (string, string) result =
  Ok
   "eyJhbGciOiJIUzI1NiJ9.eyJ1c2VyIjoia29qaSJ9.iTB59lHphOi66_84L_oinHlUm95nwOJ-NJuth8MBE3c"

(* Decode *)
utop # let decoded = Jwto.decode "eyJhbGciOiJIUzI1NiJ9.eyJ1c2VyIjoia29qaSJ9.iTB59lHphOi66_84L_oinHlUm95nwOJ-NJuth8MBE3c";;
val decoded : (Jwto.t, string) result = Ok <abstr>

utop # let Ok decoded = Jwto.decode "eyJhbGciOiJIUzI1NiJ9.eyJ1c2VyIjoia29qaSJ9.iTB59lHphOi66_84L_oinHlUm95nwOJ-NJuth8MBE3c";;
val decoded : Jwto.t = <abstr>

Above codes seems to work correctly.
And “decoded”'s type is “Jwto.t”.

this is declaration of “Jwto.t” from jwto.ml

type t =
  {
    header: header; 
    payload: payload; 
    signature: string;
  } [@@deriving show, eq]

From the my current understanding of Ocaml, i think this is a “record”.
Therefore i try to access to “signature” attribute.
But somehow this “decoded” variable does’nt seem to have the attribute…

utop # decoded.signature;;
Line 1, characters 8-17:
Error: Unbound record field signature

Why “decode” has not the attribute?
I still can’t tell if this is a Jwto problem or an OCaml problem.
OCaml version is 4.09.0, utop is 2.4.3.

2

It looks like the type Jwto.t is abstract in the signature, so you cannot access the record fields: rather than looking at the ml file, you should look at the mli file.

1 Like
3

I made this lib because I couldn’t find a decent JWT lib when experimenting with oCaml and as learning exercise. I’m not surprised if this is a problem with the lib. PRs are very welcome. Thanks

1 Like
4

I did not right understand OCaml specification…(abstract, mli etc)
But! I know now what i have to learn into!
And i was complicating this problem.
This is JWT. so i can split the JWT token with “.” and can decode each splited tokens with “Base64.decode”.
Your answer was really helpful.
Thank you!

5

Your Jwto library is really great!
And this is good a material to learn the OCaml code for me. :slight_smile:
Thank you for your effort!

By the way, maybe i found a problem by “is_valid” function.
I try to solve this and create PR.
But my OCaml skill is not yet so goold…
I am going to write about that on Issue by Github for now.