_ Git - BearSSL/blob - src/symcipher/aes_big_ctr.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 bearssl_block.h */
  28 void
  29 br_aes_big_ctr_init(br_aes_big_ctr_keys *ctx,
  30         const void *key, size_t len)
  31 {
  32         ctx->vtable = &br_aes_big_ctr_vtable;
  33         ctx->num_rounds = br_aes_keysched(ctx->skey, key, len);
  34 }
  35
  36 static void
  37 xorbuf(void *dst, const void *src, size_t len)
  38 {
  39         unsigned char *d;
  40         const unsigned char *s;
  41
  42         d = dst;
  43         s = src;
  44         while (len -- > 0) {
  45                 *d ++ ^= *s ++;
  46         }
  47 }
  48
  49 /* see bearssl_block.h */
  50 uint32_t
  51 br_aes_big_ctr_run(const br_aes_big_ctr_keys *ctx,
  52         const void *iv, uint32_t cc, void *data, size_t len)
  53 {
  54         unsigned char *buf;
  55
  56         buf = data;
  57         while (len > 0) {
  58                 unsigned char tmp[16];
  59
  60                 memcpy(tmp, iv, 12);
  61                 br_enc32be(tmp + 12, cc ++);
  62                 br_aes_big_encrypt(ctx->num_rounds, ctx->skey, tmp);
  63                 if (len <= 16) {
  64                         xorbuf(buf, tmp, len);
  65                         break;
  66                 }
  67                 xorbuf(buf, tmp, 16);
  68                 buf += 16;
  69                 len -= 16;
  70         }
  71         return cc;
  72 }
  73
  74 /* see bearssl_block.h */
  75 const br_block_ctr_class br_aes_big_ctr_vtable = {
  76         sizeof(br_aes_big_ctr_keys),
  77         16,
  78         4,
  79         (void (*)(const br_block_ctr_class **, const void *, size_t))
  80                 &br_aes_big_ctr_init,
  81         (uint32_t (*)(const br_block_ctr_class *const *,
  82                 const void *, uint32_t, void *, size_t))
  83                 &br_aes_big_ctr_run
  84 };