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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 =
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