_ Git - BearSSL/blob - src/symcipher/aes_ct64_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_ct64_cbcdec_init(br_aes_ct64_cbcdec_keys *ctx,
  30         const void *key, size_t len)
  31 {
  32         ctx->vtable = &br_aes_ct64_cbcdec_vtable;
  33         ctx->num_rounds = br_aes_ct64_keysched(ctx->skey, key, len);
  34 }
  35
  36 /* see bearssl_block.h */
  37 void
  38 br_aes_ct64_cbcdec_run(const br_aes_ct64_cbcdec_keys *ctx,
  39         void *iv, void *data, size_t len)
  40 {
  41         unsigned char *buf;
  42         uint64_t sk_exp[120];
  43         uint32_t ivw[4];
  44
  45         br_aes_ct64_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);
  46         br_range_dec32le(ivw, 4, iv);
  47         buf = data;
  48         while (len > 0) {
  49                 uint64_t q[8];
  50                 uint32_t w1[16], w2[16];
  51                 int i;
  52
  53                 if (len >= 64) {
  54                         br_range_dec32le(w1, 16, buf);
  55                 } else {
  56                         br_range_dec32le(w1, len >> 2, buf);
  57                 }
  58                 for (i = 0; i < 4; i ++) {
  59                         br_aes_ct64_interleave_in(
  60                                 &q[i], &q[i + 4], w1 + (i << 2));
  61                 }
  62                 br_aes_ct64_ortho(q);
  63                 br_aes_ct64_bitslice_decrypt(ctx->num_rounds, sk_exp, q);
  64                 br_aes_ct64_ortho(q);
  65                 for (i = 0; i < 4; i ++) {
  66                         br_aes_ct64_interleave_out(
  67                                 w2 + (i << 2), q[i], q[i + 4]);
  68                 }
  69                 for (i = 0; i < 4; i ++) {
  70                         w2[i] ^= ivw[i];
  71                 }
  72                 if (len >= 64) {
  73                         for (i = 4; i < 16; i ++) {
  74                                 w2[i] ^= w1[i - 4];
  75                         }
  76                         memcpy(ivw, w1 + 12, sizeof ivw);
  77                         br_range_enc32le(buf, w2, 16);
  78                 } else {
  79                         int j;
  80
  81                         j = (int)(len >> 2);
  82                         for (i = 4; i < j; i ++) {
  83                                 w2[i] ^= w1[i - 4];
  84                         }
  85                         memcpy(ivw, w1 + j - 4, sizeof ivw);
  86                         br_range_enc32le(buf, w2, j);
  87                         break;
  88                 }
  89                 buf += 64;
  90                 len -= 64;
  91         }
  92         br_range_enc32le(iv, ivw, 4);
  93 }
  94
  95 /* see bearssl_block.h */
  96 const br_block_cbcdec_class br_aes_ct64_cbcdec_vtable = {
  97         sizeof(br_aes_ct64_cbcdec_keys),
  98         16,
  99         4,
 100         (void (*)(const br_block_cbcdec_class **, const void *, size_t))
 101                 &br_aes_ct64_cbcdec_init,
 102         (void (*)(const br_block_cbcdec_class *const *, void *, void *, size_t))
 103                 &br_aes_ct64_cbcdec_run
 104 };