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/*
* 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;
HMAC_Init_ex(&c, kdf_K1->data, kdf_K1->length, md, NULL);
_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;
}
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