lib/krb5/sp800-108-kdf.c

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