_ Git - BearSSL/blob - src/ssl/prf.c

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #include "inner.h"
  26
  27 /* see inner.h */
  28 void
  29 br_tls_phash(void *dst, size_t len,
  30         const br_hash_class *dig,
  31         const void *secret, size_t secret_len, const char *label,
  32         size_t seed_num, const br_tls_prf_seed_chunk *seed)
  33 {
  34         unsigned char *buf;
  35         unsigned char tmp[64], a[64];
  36         br_hmac_key_context kc;
  37         br_hmac_context hc;
  38         size_t label_len, hlen, u;
  39
  40         if (len == 0) {
  41                 return;
  42         }
  43         buf = dst;
  44         for (label_len = 0; label[label_len]; label_len ++);
  45         hlen = br_digest_size(dig);
  46         br_hmac_key_init(&kc, dig, secret, secret_len);
  47         br_hmac_init(&hc, &kc, 0);
  48         br_hmac_update(&hc, label, label_len);
  49         for (u = 0; u < seed_num; u ++) {
  50                 br_hmac_update(&hc, seed[u].data, seed[u].len);
  51         }
  52         br_hmac_out(&hc, a);
  53         for (;;) {
  54                 br_hmac_init(&hc, &kc, 0);
  55                 br_hmac_update(&hc, a, hlen);
  56                 br_hmac_update(&hc, label, label_len);
  57                 for (u = 0; u < seed_num; u ++) {
  58                         br_hmac_update(&hc, seed[u].data, seed[u].len);
  59                 }
  60                 br_hmac_out(&hc, tmp);
  61                 for (u = 0; u < hlen && u < len; u ++) {
  62                         buf[u] ^= tmp[u];
  63                 }
  64                 buf += u;
  65                 len -= u;
  66                 if (len == 0) {
  67                         return;
  68                 }
  69                 br_hmac_init(&hc, &kc, 0);
  70                 br_hmac_update(&hc, a, hlen);
  71                 br_hmac_out(&hc, a);
  72         }
  73 }