/*!
 * hmac.c - hmac for C89
 * Copyright (c) 2018-2019, Christopher Jeffrey (MIT License).
 * https://github.com/handshake-org/goosig
 */

#include <stdlib.h>
#include <string.h>
#include "hmac.h"
#include "util.h"

void
goo_hmac_init(goo_hmac_t *hmac, const unsigned char *key, size_t len) {
  unsigned char pad[GOO_SHA256_BLOCK_SIZE];
  size_t i;

  ASSERT(len <= GOO_SHA256_BLOCK_SIZE);

  for (i = 0; i < len; i++)
    pad[i] = key[i] ^ 0x36;

  for (i = len; i < GOO_SHA256_BLOCK_SIZE; i++)
    pad[i] = 0x36;

  goo_sha256_init(&hmac->inner);
  goo_sha256_update(&hmac->inner, pad, GOO_SHA256_BLOCK_SIZE);

  for (i = 0; i < len; i++)
    pad[i] = key[i] ^ 0x5c;

  for (i = len; i < GOO_SHA256_BLOCK_SIZE; i++)
    pad[i] = 0x5c;

  goo_sha256_init(&hmac->outer);
  goo_sha256_update(&hmac->outer, pad, GOO_SHA256_BLOCK_SIZE);

  memset(pad, 0x00, GOO_SHA256_BLOCK_SIZE);
}

void
goo_hmac_update(goo_hmac_t *hmac, const void *data, size_t len) {
  goo_sha256_update(&hmac->inner, data, len);
}

void
goo_hmac_final(goo_hmac_t *hmac, unsigned char *out) {
  goo_sha256_final(&hmac->inner, out);
  goo_sha256_update(&hmac->outer, out, GOO_SHA256_HASH_SIZE);
  goo_sha256_final(&hmac->outer, out);
}

void
goo_hmac(unsigned char *out,
         const void *data,
         size_t len,
         const unsigned char *key,
         size_t klen) {
  goo_hmac_t hmac;
  goo_hmac_init(&hmac, key, klen);
  goo_hmac_update(&hmac, data, len);
  goo_hmac_final(&hmac, out);
}