_ Git - BearSSL/blob - src/symcipher/des_ct_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_des_ct_cbcdec_init(br_des_ct_cbcdec_keys *ctx,
  30         const void *key, size_t len)
  31 {
  32         ctx->vtable = &br_des_ct_cbcdec_vtable;
  33         ctx->num_rounds = br_des_ct_keysched(ctx->skey, key, len);
  34         if (len == 8) {
  35                 br_des_rev_skey(ctx->skey);
  36         } else {
  37                 int i;
  38
  39                 for (i = 0; i < 48; i += 2) {
  40                         uint32_t t;
  41
  42                         t = ctx->skey[i];
  43                         ctx->skey[i] = ctx->skey[94 - i];
  44                         ctx->skey[94 - i] = t;
  45                         t = ctx->skey[i + 1];
  46                         ctx->skey[i + 1] = ctx->skey[95 - i];
  47                         ctx->skey[95 - i] = t;
  48                 }
  49         }
  50 }
  51
  52 /* see bearssl_block.h */
  53 void
  54 br_des_ct_cbcdec_run(const br_des_ct_cbcdec_keys *ctx,
  55         void *iv, void *data, size_t len)
  56 {
  57         unsigned char *buf, *ivbuf;
  58         uint32_t sk_exp[288];
  59
  60         br_des_ct_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);
  61         ivbuf = iv;
  62         buf = data;
  63         while (len > 0) {
  64                 unsigned char tmp[8];
  65                 int i;
  66
  67                 memcpy(tmp, buf, 8);
  68                 br_des_ct_process_block(ctx->num_rounds, sk_exp, buf);
  69                 for (i = 0; i < 8; i ++) {
  70                         buf[i] ^= ivbuf[i];
  71                 }
  72                 memcpy(ivbuf, tmp, 8);
  73                 buf += 8;
  74                 len -= 8;
  75         }
  76 }
  77
  78 /* see bearssl_block.h */
  79 const br_block_cbcdec_class br_des_ct_cbcdec_vtable = {
  80         sizeof(br_des_ct_cbcdec_keys),
  81         8,
  82         3,
  83         (void (*)(const br_block_cbcdec_class **, const void *, size_t))
  84                 &br_des_ct_cbcdec_init,
  85         (void (*)(const br_block_cbcdec_class *const *, void *, void *, size_t))
  86                 &br_des_ct_cbcdec_run
  87 };