/*
 * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The OpenAirInterface Software Alliance licenses this file to You under 
 * the Apache License, Version 2.0  (the "License"); you may not use this file
 * except in compliance with the License.  
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *-------------------------------------------------------------------------------
 * For more information about the OpenAirInterface (OAI) Software Alliance:
 *      contact@openairinterface.org
 */

#include <stdlib.h>
#include <stdint.h>
#include <string.h>

#include <nettle/hmac.h>

#include "security_types.h"
#include "secu_defs.h"
#include "dynamic_memory_check.h"

void
kdf (
  const uint8_t * key,
  const unsigned key_len,
  uint8_t * s,
  const unsigned s_len,
  uint8_t * out,
  const unsigned out_len)
{
  struct hmac_sha256_ctx                  *ctx = calloc(1, sizeof(struct hmac_sha256_ctx));

  //memset (&ctx, 0, sizeof (ctx));
  hmac_sha256_set_key (ctx, key_len, key);
  hmac_sha256_update (ctx, s_len, s);
  hmac_sha256_digest (ctx, out_len, out);
  free_wrapper((void**) &ctx);
}

int
derive_keNB (
  const uint8_t *kasme_32,
  const uint32_t nas_count,
  uint8_t * keNB)
{
  uint8_t                                 s[7] = {0};

  // FC
  s[0] = FC_KENB;
  // P0 = Uplink NAS count
  s[1] = (nas_count & 0xff000000) >> 24;
  s[2] = (nas_count & 0x00ff0000) >> 16;
  s[3] = (nas_count & 0x0000ff00) >> 8;
  s[4] = (nas_count & 0x000000ff);
  // Length of NAS count
  s[5] = 0x00;
  s[6] = 0x04;
  kdf (kasme_32, 32, s, 7, keNB, 32);
  return 0;
}
