/**

 * @file hmac_sha1.c  Implements HMAC-SHA1 as of RFC 2202

 *

 * Copyright (C) 2010 Creytiv.com

 */

#include <string.h>

#include <re_types.h>

#ifdef USE_OPENSSL

#include <openssl/sha.h>

#include <openssl/hmac.h>

#include <openssl/err.h>

#else

#include <re_sha.h>

#endif

#include <re_hmac.h>

/** SHA-1 Block size */

#ifndef SHA_BLOCKSIZE

#define SHA_BLOCKSIZE   64

#endif

/**

 * Function to compute the digest

 *

 * @param k   Secret key

 * @param lk  Length of the key in bytes

 * @param d   Data

 * @param ld  Length of data in bytes

 * @param out Digest output

 * @param t   Size of digest output

 */

void hmac_sha1(const uint8_t *k,  /* secret key */

         size_t   lk,       /* length of the key in bytes */

         const uint8_t *d,  /* data */

         size_t   ld,       /* length of data in bytes */

         uint8_t *out,      /* output buffer, at least "t" bytes */

         size_t   t)

{

#ifdef USE_OPENSSL

  (void)t;

  if (!HMAC(EVP_sha1(), k, (int)lk, d, ld, out, NULL))

    ERR_clear_error();

#else

  SHA_CTX ictx, octx;

  uint8_t isha[SHA_DIGEST_LENGTH], osha[SHA_DIGEST_LENGTH];

  uint8_t key[SHA_DIGEST_LENGTH];

  uint8_t buf[SHA_BLOCKSIZE];

  size_t  i;

  if (lk > SHA_BLOCKSIZE) {

    SHA_CTX tctx;

    SHA1_Init(&tctx);

    SHA1_Update(&tctx, k, lk);

    SHA1_Final(key, &tctx);

    k = key;

    lk = SHA_DIGEST_LENGTH;

  }

  /**** Inner Digest ****/

  SHA1_Init(&ictx);

  /* Pad the key for inner digest */

  for (i = 0 ; i < lk ; ++i)

    buf[i] = k[i] ^ 0x36;

  for (i = lk ; i < SHA_BLOCKSIZE ; ++i)

    buf[i] = 0x36;

  SHA1_Update(&ictx, buf, SHA_BLOCKSIZE);

  SHA1_Update(&ictx, d, ld);

  SHA1_Final(isha, &ictx);

  /**** Outer Digest ****/

  SHA1_Init(&octx);

  /* Pad the key for outter digest */

  for (i = 0 ; i < lk ; ++i)

    buf[i] = k[i] ^ 0x5c;

  for (i = lk ; i < SHA_BLOCKSIZE ; ++i)

    buf[i] = 0x5c;

  SHA1_Update(&octx, buf, SHA_BLOCKSIZE);

  SHA1_Update(&octx, isha, SHA_DIGEST_LENGTH);

  SHA1_Final(osha, &octx);

  /* truncate and print the results */

  t = t > SHA_DIGEST_LENGTH ? SHA_DIGEST_LENGTH : t;

  memcpy(out, osha, t);

#endif

}