_ Git - BearSSL/blob - src/symcipher/aes_big_cbcdec.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_cbcdec_init(br_aes_big_cbcdec_keys *ctx,
  30         const void *key, size_t len)
  31 {
  32         ctx->vtable = &br_aes_big_cbcdec_vtable;
  33         ctx->num_rounds = br_aes_big_keysched_inv(ctx->skey, key, len);
  34 }
  35
  36 /* see bearssl_block.h */
  37 void
  38 br_aes_big_cbcdec_run(const br_aes_big_cbcdec_keys *ctx,
  39         void *iv, void *data, size_t len)
  40 {
  41         unsigned char *buf, *ivbuf;
  42
  43         ivbuf = iv;
  44         buf = data;
  45         while (len > 0) {
  46                 unsigned char tmp[16];
  47                 int i;
  48
  49                 memcpy(tmp, buf, 16);
  50                 br_aes_big_decrypt(ctx->num_rounds, ctx->skey, buf);
  51                 for (i = 0; i < 16; i ++) {
  52                         buf[i] ^= ivbuf[i];
  53                 }
  54                 memcpy(ivbuf, tmp, 16);
  55                 buf += 16;
  56                 len -= 16;
  57         }
  58 }
  59
  60 /* see bearssl_block.h */
  61 const br_block_cbcdec_class br_aes_big_cbcdec_vtable = {
  62         sizeof(br_aes_big_cbcdec_keys),
  63         16,
  64         4,
  65         (void (*)(const br_block_cbcdec_class **, const void *, size_t))
  66                 &br_aes_big_cbcdec_init,
  67         (void (*)(const br_block_cbcdec_class *const *, void *, void *, size_t))
  68                 &br_aes_big_cbcdec_run
  69 };