nim-libp2p/libp2p/crypto/hkdf.nim

# Nim-LibP2P
# Copyright (c) 2023 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
# at your option.
# This file may not be copied, modified, or distributed except according to
# those terms.

# https://tools.ietf.org/html/rfc5869

{.push raises: [].}

import nimcrypto
import bearssl/[kdf, hash]

type HkdfResult*[len: static int] = array[len, byte]

proc hkdf*[T: sha256, len: static int](
    _: type[T],
    salt, ikm, info: openArray[byte],
    outputs: var openArray[HkdfResult[len]],
) =
  var ctx: HkdfContext
  hkdfInit(
    ctx,
    addr sha256Vtable,
    if salt.len > 0:
      unsafeAddr salt[0]
    else:
      nil
    ,
    csize_t(salt.len),
  )
  hkdfInject(
    ctx,
    if ikm.len > 0:
      unsafeAddr ikm[0]
    else:
      nil
    ,
    csize_t(ikm.len),
  )
  hkdfFlip(ctx)
  for i in 0 .. outputs.high:
    discard hkdfProduce(
      ctx,
      if info.len > 0:
        unsafeAddr info[0]
      else:
        nil
      ,
      csize_t(info.len),
      addr outputs[i][0],
      csize_t(outputs[i].len),
    )