mte/src/crypto.ml

(* TODO key format
   - check what is the exact format in GNUNET
   - endianess issue? *)
module EddsaPublicKey = struct
  (* EdDSA and ECDHE public keys always point on Curve25519
     and represented  using the standard 256 bits Ed25519 compact format,
     converted to Crockford Base32. *)
  open Mirage_crypto_ec.Ed25519

  type t = pub

  let to_octets t = pub_to_octets t
  let of_octets t = pub_of_octets t |> Result.get_ok
  let bin = Bin.map (Bin.bytes 32) of_octets to_octets

  let of_b32 s =
    let open Syntax in
    let* octets = B32.decode s in
    match pub_of_octets octets with
    | Error e -> Fmt.error "%a" Mirage_crypto_ec.pp_error e
    | Ok pub -> Ok pub

  let to_b32 t = B32.encode (to_octets t)
  let jsont = Jsont.of_of_string ~kind:"EddsaPublicKey" of_b32 ~enc:to_b32
end

module EddsaPrivateKey = struct
  (* EdDSA and ECDHE public keys always point on Curve25519
     and represented  using the standard 256 bits Ed25519 compact format,
     converted to Crockford Base32. *)
  open Mirage_crypto_ec.Ed25519

  type t = priv

  let pub_of_priv = pub_of_priv
  let to_octets t = priv_to_octets t
  let of_octets t = priv_of_octets t |> Result.get_ok
  let bin = Bin.map (Bin.bytes 32) of_octets to_octets

  let of_b32 s =
    let open Syntax in
    let* octets = B32.decode s in
    match priv_of_octets octets with
    | Error e -> Fmt.error "%a" Mirage_crypto_ec.pp_error e
    | Ok priv -> Ok priv

  let to_b32 t = B32.encode (to_octets t)
  let jsont = Jsont.of_of_string ~kind:"EddsaPrivateKey" of_b32 ~enc:to_b32
end

module EddsaSignature : sig
  type t

  val sign : key:Mirage_crypto_ec.Ed25519.priv -> string -> t
  val sign_as_string : key:Mirage_crypto_ec.Ed25519.priv -> string -> string
  val of_b32 : string -> (t, string) result
  val to_b32 : t -> string
  val to_octets : t -> string
  val of_octets : string -> t
  val jsont : t Jsont.t
  val bin : t Bin.t
end = struct
  (* TODO key format
     endianess issue? *)
  (* EdDSA signatures are transmitted as 64-bytes base32
     binary-encoded objects with just the R and S values (base32_ binary-only).

     They are signature over a c-struct like `TALER_xxxPS` + with a purpose *)
  type t = string

  let to_octets t = t

  let of_octets v =
    match String.length v = 64 with
    | false ->
        Fmt.failwith "EddsaSignature.of_octets failure: data is not 64 bytes."
    | true -> v

  let bin = Bin.map (Bin.bytes 64) of_octets to_octets

  let sign ~key s =
    (* mirage_crypto: "The result is the concatenation of r and s, as specified in RFC 8032." *)
    Mirage_crypto_ec.Ed25519.sign ~key s

  let sign_as_string ~key s = sign ~key s

  let check_size t =
    match String.length t = 64 with
    | false -> Error "EddsaSignature: invalid string length"
    | true -> Ok ()

  let of_b32 s =
    let open Syntax in
    let* t = B32.decode s in
    let+ () = check_size t in
    t

  let to_b32 = B32.encode
  let jsont = Jsont.of_of_string ~kind:"EddsaSignature" of_b32 ~enc:to_b32
end

module RsaPublicKey = struct
  open Mirage_crypto_pk

  type t = Rsa.pub

  let of_octets = Util.Bin_rsa.pub_of_octets
  let to_octets = Util.Bin_rsa.pub_to_octets

  let of_b32 s =
    let open Syntax in
    let* s = B32.decode s in
    let v = Util.Bin_rsa.pub_of_octets s in
    let+ v = Rsa.pub ~n:v.n ~e:v.e |> unwrap_err_msg in
    v

  let to_b32 t = B32.encode (to_octets t)
  let jsont = Jsont.of_of_string ~kind:"RsaPublicKey" of_b32 ~enc:to_b32
end

module RsaPrivateKey = struct
  open Mirage_crypto_pk.Rsa

  type t = priv

  let pub_of_priv = pub_of_priv
  let of_octets = Util.Bin_rsa.priv_of_octets
  let to_octets = Util.Bin_rsa.priv_to_octets

  let of_b32 s =
    let open Syntax in
    let* s = B32.decode s in
    Ok (of_octets s)

  let to_b32 t = B32.encode (to_octets t)
  let jsont = Jsont.of_of_string ~kind:"RsaPrivateKey" of_b32 ~enc:to_b32
end

module RsaSignature : sig
  type t

  val to_octets : t -> string
  val sign : key:Mirage_crypto_pk.Rsa.priv -> string -> t
  val of_b32 : string -> (t, string) result
  val to_b32 : t -> string
  val jsont : t Jsont.t
end = struct
  type t = string

  let to_octets t = t

  (* TODO rsa sign *)
  let sign ~key s =
    Mirage_crypto_pk.Rsa.decrypt ~crt_hardening:true ~mask:`Yes ~key s

  let of_b32 s = B32.decode s
  let to_b32 t = B32.encode t
  let jsont = Jsont.of_of_string ~kind:"RsaSignature" of_b32 ~enc:to_b32
end