_ Git - BearSSL/blob - src/symcipher/aes_ct_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_ct_ctr_init(br_aes_ct_ctr_keys *ctx,
  30         const void *key, size_t len)
  31 {
  32         ctx->vtable = &br_aes_ct_ctr_vtable;
  33         ctx->num_rounds = br_aes_ct_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_ct_ctr_run(const br_aes_ct_ctr_keys *ctx,
  52         const void *iv, uint32_t cc, void *data, size_t len)
  53 {
  54         unsigned char *buf;
  55         const unsigned char *ivbuf;
  56         uint32_t iv0, iv1, iv2;
  57         uint32_t sk_exp[120];
  58
  59         br_aes_ct_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);
  60         ivbuf = iv;
  61         iv0 = br_dec32le(ivbuf);
  62         iv1 = br_dec32le(ivbuf + 4);
  63         iv2 = br_dec32le(ivbuf + 8);
  64         buf = data;
  65         while (len > 0) {
  66                 uint32_t q[8];
  67                 unsigned char tmp[32];
  68
  69                 /*
  70                  * TODO: see if we can save on the first br_aes_ct_ortho()
  71                  * call, since iv0/iv1/iv2 are constant for the whole run.
  72                  */
  73                 q[0] = q[1] = iv0;
  74                 q[2] = q[3] = iv1;
  75                 q[4] = q[5] = iv2;
  76                 q[6] = br_swap32(cc);
  77                 q[7] = br_swap32(cc + 1);
  78                 br_aes_ct_ortho(q);
  79                 br_aes_ct_bitslice_encrypt(ctx->num_rounds, sk_exp, q);
  80                 br_aes_ct_ortho(q);
  81                 br_enc32le(tmp, q[0]);
  82                 br_enc32le(tmp + 4, q[2]);
  83                 br_enc32le(tmp + 8, q[4]);
  84                 br_enc32le(tmp + 12, q[6]);
  85                 br_enc32le(tmp + 16, q[1]);
  86                 br_enc32le(tmp + 20, q[3]);
  87                 br_enc32le(tmp + 24, q[5]);
  88                 br_enc32le(tmp + 28, q[7]);
  89
  90                 if (len <= 32) {
  91                         xorbuf(buf, tmp, len);
  92                         cc ++;
  93                         if (len > 16) {
  94                                 cc ++;
  95                         }
  96                         break;
  97                 }
  98                 xorbuf(buf, tmp, 32);
  99                 buf += 32;
 100                 len -= 32;
 101                 cc += 2;
 102         }
 103         return cc;
 104 }
 105
 106 /* see bearssl_block.h */
 107 const br_block_ctr_class br_aes_ct_ctr_vtable = {
 108         sizeof(br_aes_ct_ctr_keys),
 109         16,
 110         4,
 111         (void (*)(const br_block_ctr_class **, const void *, size_t))
 112                 &br_aes_ct_ctr_init,
 113         (uint32_t (*)(const br_block_ctr_class *const *,
 114                 const void *, uint32_t, void *, size_t))
 115                 &br_aes_ct_ctr_run
 116 };