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sp800-108-kdf.c revision 1.2 
      1 /*	$NetBSD: sp800-108-kdf.c,v 1.2 2017/01/28 21:31:49 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2015, Secure Endpoints Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  *
     11  * - Redistributions of source code must retain the above copyright
     12  *   notice, this list of conditions and the following disclaimer.
     13  *
     14  * - Redistributions in binary form must reproduce the above copyright
     15  *   notice, this list of conditions and the following disclaimer in
     16  *   the documentation and/or other materials provided with the
     17  *   distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     22  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     23  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
     24  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     25  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     26  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     28  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
     30  * OF THE POSSIBILITY OF SUCH DAMAGE.
     31  *
     32  */
     33 
     34 #include "krb5_locl.h"
     35 
     36 /*
     37  * SP800-108 KDF
     38  */
     39 
     40 /**
     41  * As described in SP800-108 5.1 (for HMAC)
     42  *
     43  * @param context	Kerberos 5 context
     44  * @param kdf_K1	Base key material.
     45  * @param kdf_label	A string that identifies the purpose for the derived key.
     46  * @param kdf_context   A binary string containing parties, nonce, etc.
     47  * @param md		Message digest function to use for PRF.
     48  * @param kdf_K0	Derived key data.
     49  *
     50  * @return Return an error code for an failure or 0 on success.
     51  * @ingroup krb5_crypto
     52  */
     53 krb5_error_code
     54 _krb5_SP800_108_HMAC_KDF(krb5_context context,
     55 			 const krb5_data *kdf_K1,
     56 			 const krb5_data *kdf_label,
     57 			 const krb5_data *kdf_context,
     58 			 const EVP_MD *md,
     59 			 krb5_data *kdf_K0)
     60 {
     61     HMAC_CTX c;
     62     unsigned char *p = kdf_K0->data;
     63     size_t i, n, left = kdf_K0->length;
     64     unsigned char hmac[EVP_MAX_MD_SIZE];
     65     unsigned int h = EVP_MD_size(md);
     66     const size_t L = kdf_K0->length;
     67 
     68     heim_assert(md != NULL, "SP800-108 KDF internal error");
     69 
     70     HMAC_CTX_init(&c);
     71 
     72     n = L / h;
     73 
     74     for (i = 0; i <= n; i++) {
     75 	unsigned char tmp[4];
     76 	size_t len;
     77 
     78 	HMAC_Init_ex(&c, kdf_K1->data, kdf_K1->length, md, NULL);
     79 
     80 	_krb5_put_int(tmp, i + 1, 4);
     81 	HMAC_Update(&c, tmp, 4);
     82 	HMAC_Update(&c, kdf_label->data, kdf_label->length);
     83 	HMAC_Update(&c, (unsigned char *)"", 1);
     84 	if (kdf_context)
     85 	    HMAC_Update(&c, kdf_context->data, kdf_context->length);
     86 	_krb5_put_int(tmp, L * 8, 4);
     87 	HMAC_Update(&c, tmp, 4);
     88 
     89 	HMAC_Final(&c, hmac, &h);
     90 	len = h > left ? left : h;
     91 	memcpy(p, hmac, len);
     92 	p += len;
     93 	left -= len;
     94     }
     95 
     96     HMAC_CTX_cleanup(&c);
     97 
     98     return 0;
     99 }
    100