~ Bin_rsa

src/crypto.ml

@@ -1,3 +1,100 @@
+open Syntax
+
+module Binary_format_rsa = struct
+  (* TODO tests:
+         - need to strip leading zeros?
+         - endianess ok? *)
+  (* RSA public key binary format
+       https://www.gnupg.org/documentation/manuals/gcrypt/MPI-formats.html
+       := { uint16_be: n size; uint16_be: e size; n; e}
+
+       integer in big-endian format (MSB first)
+       leading zeroes are stripped unless they are required to keep a value positive
+       no 0-termination *)
+
+  let rev_string len s = String.init len (fun i -> s.[len - 1 - i])
+
+  (* we reverse bytes because Z.of_bits reads bytes in little endian *)
+  let z_of_bits_be src pos len =
+    String.sub src pos len |> rev_string len |> Z.of_bits
+
+  let z_to_bits_be z =
+    let bits = Z.to_bits z in
+    rev_string (String.length bits) bits
+
+  let z_array_to_octets (arr : Z.t array) =
+    let nb = Array.length arr in
+    let bits_arr = Array.map z_to_bits_be arr in
+    let len_arr = Array.map String.length bits_arr in
+    let len = (2 * nb) + Array.fold_left ( + ) 0 len_arr in
+    let b = Bytes.make len '\x00' in
+    let pos = ref 0 in
+    Array.iter
+      (fun len ->
+        Bytes.set_uint16_be b !pos len;
+        pos := !pos + 2)
+      len_arr;
+    Array.iteri
+      (fun i bits ->
+        let len = len_arr.(i) in
+        Bytes.blit_string bits 0 b !pos len;
+        pos := !pos + len)
+      bits_arr;
+    Bytes.unsafe_to_string b
+
+  let check = function
+    | false -> Error "rsa of_octets error, invalid data"
+    | true -> Ok ()
+
+  let z_array_of_octets ~nb s =
+    let s_len = String.length s in
+    let* () = check (s_len > 2 * nb) in
+    let pos = ref 0 in
+    let len_arr =
+      Array.init nb (fun _i ->
+          let len = String.get_uint16_be s !pos in
+          pos := !pos + 2;
+          len)
+    in
+    let* () =
+      let len = (2 * nb) + Array.fold_left ( + ) 0 len_arr in
+      check (s_len = len)
+    in
+    let z_arr =
+      Array.init nb (fun i ->
+          let len = len_arr.(i) in
+          let z = z_of_bits_be s !pos len in
+          pos := !pos + len;
+          z)
+    in
+    Ok z_arr
+
+  let pub_to_octets ({ n; e } : Mirage_crypto_pk.Rsa.pub) =
+    z_array_to_octets [| n; e |]
+
+  let pub_of_octets s =
+    let* arr = z_array_of_octets ~nb:2 s in
+    match arr with
+    | [| n; e |] ->
+        let+ pub = Mirage_crypto_pk.Rsa.pub ~n ~e |> unwrap_err_msg in
+        pub
+    | _ -> assert false
+
+  let priv_to_octets ({ e; d; n; p; q; dp; dq; q' } : Mirage_crypto_pk.Rsa.priv)
+      =
+    z_array_to_octets [| e; d; n; p; q; dp; dq; q' |]
+
+  let priv_of_octets s =
+    let* arr = z_array_of_octets ~nb:8 s in
+    match arr with
+    | [| e; d; n; p; q; dp; dq; q' |] ->
+        let+ priv =
+          Mirage_crypto_pk.Rsa.priv ~e ~d ~n ~p ~q ~dp ~dq ~q' |> unwrap_err_msg
+        in
+        priv
+    | _ -> assert false
+end
+
 (* TODO key format
    - check what is the exact format in GNUNET
    - endianess issue? *)
@@ -17,13 +114,10 @@ module EddsaPublicKey = struct
     | Ok v -> Ok v
 
   let bin =
-    let of_octets o =
-      match of_octets o with Error e -> raise (Util.Bin_error e) | Ok v -> v
-    in
-    Bin.map (Bin.bytes 32) of_octets to_octets
+    let of_octets_exn t = of_octets t |> Result.get_ok in
+    Bin.map (Bin.bytes 32) of_octets_exn to_octets
 
   let of_b32 s =
-    let open Syntax in
     let* octets = B32.decode s in
     let* pub = of_octets octets in
     Ok pub
@@ -62,7 +156,6 @@ module EddsaPrivateKey = struct
 
   let jsont =
     let of_b32 s =
-      let open Syntax in
       let* octets = B32.decode s in
       of_octets octets
     in
@@ -117,7 +210,6 @@ end = struct
 
   let jsont =
     let of_b32 s =
-      let open Syntax in
       let* t = B32.decode s in
       let+ () = check_size t in
       t
@@ -137,12 +229,11 @@ module RsaPublicKey = struct
 
   type t = Rsa.pub
 
-  let to_octets = Util.Bin_rsa.pub_to_octets
-  let of_octets = Util.Bin_rsa.pub_of_octets
+  let to_octets = Binary_format_rsa.pub_to_octets
+  let of_octets = Binary_format_rsa.pub_of_octets
 
   let jsont =
     let of_b32 s =
-      let open Syntax in
       let* s = B32.decode s in
       let+ v = of_octets s in
       v
@@ -168,12 +259,11 @@ module RsaPrivateKey = struct
     (priv, pub)
 
   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_octets = Binary_format_rsa.priv_of_octets
+  let to_octets = Binary_format_rsa.priv_to_octets
 
   let jsont =
     let of_b32 s =
-      let open Syntax in
       let* s = B32.decode s in
       let+ v = of_octets s in
       v