_ Git - BearSSL/blob - src/hash/mgf1.c

   1 /*
   2  * Copyright (c) 2018 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_mgf1_xor(void *data, size_t len,
  30         const br_hash_class *dig, const void *seed, size_t seed_len)
  31 {
  32         unsigned char *buf;
  33         size_t u, hlen;
  34         uint32_t c;
  35
  36         buf = data;
  37         hlen = br_digest_size(dig);
  38         for (u = 0, c = 0; u < len; u += hlen, c ++) {
  39                 br_hash_compat_context hc;
  40                 unsigned char tmp[64];
  41                 size_t v;
  42
  43                 hc.vtable = dig;
  44                 dig->init(&hc.vtable);
  45                 dig->update(&hc.vtable, seed, seed_len);
  46                 br_enc32be(tmp, c);
  47                 dig->update(&hc.vtable, tmp, 4);
  48                 dig->out(&hc.vtable, tmp);
  49                 for (v = 0; v < hlen; v ++) {
  50                         if ((u + v) >= len) {
  51                                 break;
  52                         }
  53                         buf[u + v] ^= tmp[v];
  54                 }
  55         }
  56 }