/*

 * Copyright (c) 2015, Secure Endpoints Inc.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 *

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in

 *   the documentation and/or other materials provided with the

 *   distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 */

#include "krb5_locl.h"

/*

 * SP800-108 KDF

 */

/**

 * As described in SP800-108 5.1 (for HMAC)

 *

 * @param context Kerberos 5 context

 * @param kdf_K1  Base key material.

 * @param kdf_label A string that identifies the purpose for the derived key.

 * @param kdf_context   A binary string containing parties, nonce, etc.

 * @param md    Message digest function to use for PRF.

 * @param kdf_K0  Derived key data.

 *

 * @return Return an error code for an failure or 0 on success.

 * @ingroup krb5_crypto

 */

krb5_error_code

_krb5_SP800_108_HMAC_KDF(krb5_context context,

       const krb5_data *kdf_K1,

       const krb5_data *kdf_label,

       const krb5_data *kdf_context,

       const EVP_MD *md,

       krb5_data *kdf_K0)

{

    HMAC_CTX c;

    unsigned char *p = kdf_K0->data;

    size_t i, n, left = kdf_K0->length;

    unsigned char hmac[EVP_MAX_MD_SIZE];

    unsigned int h = EVP_MD_size(md);

    const size_t L = kdf_K0->length;

    heim_assert(md != NULL, "SP800-108 KDF internal error");

    HMAC_CTX_init(&c);

    n = L / h;

    for (i = 0; i <= n; i++) {

  unsigned char tmp[4];

  size_t len;

        if (HMAC_Init_ex(&c, kdf_K1->data, kdf_K1->length, md, NULL) == 0) {

            HMAC_CTX_cleanup(&c);

            return krb5_enomem(context);

        }

  _krb5_put_int(tmp, i + 1, 4);

  HMAC_Update(&c, tmp, 4);

  HMAC_Update(&c, kdf_label->data, kdf_label->length);

  HMAC_Update(&c, (unsigned char *)"", 1);

  if (kdf_context)

      HMAC_Update(&c, kdf_context->data, kdf_context->length);

  _krb5_put_int(tmp, L * 8, 4);

  HMAC_Update(&c, tmp, 4);

  HMAC_Final(&c, hmac, &h);

  len = h > left ? left : h;

  memcpy(p, hmac, len);

  p += len;

  left -= len;

    }

    HMAC_CTX_cleanup(&c);

    return 0;

}