unikernel/duniverse/kdf/pbkdf/pbkdf.ml

@@ -0,0 +1,63 @@
+module type S = sig
+  val pbkdf1 : password:string -> salt:string -> count:int -> dk_len:int -> string
+  val pbkdf2 : password:string -> salt:string -> count:int -> dk_len:int32 -> string
+end
+
+let cdiv x y =
+  (* This is lifted from Nocrypto.Uncommon.(//)
+     (formerly known as [cdiv]). It is part of the documented, publically
+     exposed _internal_ utility library not for public consumption, hence
+     the API break that prompted this copy-pasted function. *)
+  if y < 1 then raise Division_by_zero else
+    if x > 0 then 1 + ((x - 1) / y) else 0 [@@inline]
+
+module Make (H: Digestif.S) : S = struct
+  let pbkdf1 ~password ~salt ~count ~dk_len =
+    if String.length salt <> 8 then invalid_arg "salt should be 8 bytes"
+    else if count <= 0 then invalid_arg "count must be a positive integer"
+    else if dk_len <= 0 then invalid_arg "derived key length must be a positive integer"
+    else if dk_len > H.digest_size then invalid_arg "derived key too long"
+    else
+      let rec loop t = function
+          0 -> t
+        | i -> loop H.(to_raw_string (digest_string t)) (i - 1)
+      in
+      String.sub (loop (password ^ salt) count) 0 dk_len
+
+  let pbkdf2 ~password ~salt ~count ~dk_len =
+    if count <= 0 then invalid_arg "count must be a positive integer"
+    else if dk_len <= 0l then invalid_arg "derived key length must be a positive integer"
+    else
+      let h_len = H.digest_size
+      and dk_len = Int32.to_int dk_len in
+      let l = cdiv dk_len h_len in
+      let r = dk_len - (l - 1) * h_len in
+      let block i =
+        let rec f u xor = function
+          | 0 -> xor
+          | j ->
+            let u = H.(to_raw_string (hmac_string ~key:password u)) in
+            f u (Mirage_crypto.Uncommon.xor xor u) (j - 1)
+        in
+        let int_i = Bytes.create 4 in
+        Bytes.set_int32_be int_i 0 (Int32.of_int i);
+        let u_1 = H.hmac_string ~key:password (salt ^ Bytes.unsafe_to_string int_i) in
+        let u_1 = H.to_raw_string u_1 in
+        f u_1 u_1 (count - 1)
+      in
+      let rec loop blocks = function
+        | 0 -> blocks
+        | i -> loop (block i :: blocks) (i - 1)
+      in
+      String.concat "" (loop [String.sub (block l) 0 r] (l - 1))
+end
+
+let pbkdf1 ~hash ~password ~salt ~count ~dk_len =
+  let module H = (val (Digestif.module_of_hash' hash)) in
+  let module PBKDF = Make (H) in
+  PBKDF.pbkdf1 ~password ~salt ~count ~dk_len
+
+let pbkdf2 ~prf ~password ~salt ~count ~dk_len =
+  let module H = (val (Digestif.module_of_hash' prf)) in
+  let module PBKDF = Make (H) in
+  PBKDF.pbkdf2 ~password ~salt ~count ~dk_len