implement hash

TODO good handling of 0-terminated C-string

src/binary_formats.ml

@@ -26,6 +26,15 @@
      - outdated doc(?)
    - some missing struct documentation *)
 
+(* TODO hash and C(ancer)-terminated strings
+
+   - "A JSON object is canonicalized by converting it to an ASCII byte array
+      with the algorithm specified in RFC 8785. The resulting bytes are
+      terminated with a single 0-byte and then hashed with SHA512."
+   - from the code it looks like its the same for all stringy-strings
+     !! that are not raw bytes data
+ *)
+
 module UTIL = struct
   let int32_size = 4
   let int64_size = 8
@@ -71,9 +80,21 @@ module UTIL = struct
       record (fun v -> { v }) |+ field (bytes 64) (fun t -> t.v) |> sealr
   end
 
-  module MK_HASH_32 () = struct
+  module MK_HASH_32 () : sig
+    type t = private { hash: string }
+
+    val of_string : string -> t
+    val bin : t Bin.t
+  end = struct
     type t = { hash: string }
 
+    let of_string s =
+      match String.length s = 32 with
+      | false -> Fmt.failwith "SHA256 failure: data is not 32 bytes"
+      | true ->
+          let hash = Digestif.SHA256.(to_raw_string (digest_string s)) in
+          { hash }
+
     let bin =
       let open Bin in
       record (fun hash -> { hash })
@@ -81,9 +102,21 @@ module UTIL = struct
       |> sealr
   end
 
-  module MK_HASH_64 () = struct
+  module MK_HASH_64 () : sig
+    type t = private { hash: string }
+
+    val f : string -> t
+    val bin : t Bin.t
+  end = struct
     type t = { hash: string }
 
+    let f s =
+      match String.length s = 64 with
+      | false -> Fmt.failwith "SHA512 failure: data is not 64bytes"
+      | true ->
+          let hash = Digestif.SHA512.(to_raw_string (digest_string s)) in
+          { hash }
+
     let bin =
       let open Bin in
       record (fun hash -> { hash })
@@ -183,7 +216,7 @@ module EncryptedLinkSecretP = MK_64 ()
 module DenominationBlindingKeyP = MK_32 ()
 
 (* GNUNET_CRYPTO format *)
-module RsaPublicKey = struct
+module GNUNET_RsaPublicKey = struct
   (* libgnuutil format:
      https://docs.gnunet.org/doxygen/d9/dbe/structGNUNET__CRYPTO__RsaPublicKeyHeaderP.html
      https://docs.gnunet.org/doxygen/d6/d70/group__libgnunetutil.html#ga9c99a81e8cd649c1c925d23211a0738f