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       1                 :            : /* ctr_mode.c - TinyCrypt CTR mode implementation */
       2                 :            : 
       3                 :            : /*
       4                 :            :  *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
       5                 :            :  *
       6                 :            :  *  Redistribution and use in source and binary forms, with or without
       7                 :            :  *  modification, are permitted provided that the following conditions are met:
       8                 :            :  *
       9                 :            :  *    - Redistributions of source code must retain the above copyright notice,
      10                 :            :  *     this list of conditions and the following disclaimer.
      11                 :            :  *
      12                 :            :  *    - Redistributions in binary form must reproduce the above copyright
      13                 :            :  *    notice, this list of conditions and the following disclaimer in the
      14                 :            :  *    documentation and/or other materials provided with the distribution.
      15                 :            :  *
      16                 :            :  *    - Neither the name of Intel Corporation nor the names of its contributors
      17                 :            :  *    may be used to endorse or promote products derived from this software
      18                 :            :  *    without specific prior written permission.
      19                 :            :  *
      20                 :            :  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
      21                 :            :  *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      22                 :            :  *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      23                 :            :  *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
      24                 :            :  *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
      25                 :            :  *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
      26                 :            :  *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
      27                 :            :  *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
      28                 :            :  *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
      29                 :            :  *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      30                 :            :  *  POSSIBILITY OF SUCH DAMAGE.
      31                 :            :  */
      32                 :            : 
      33                 :            : #include <tinycrypt/constants.h>
      34                 :            : #include <tinycrypt/ctr_mode.h>
      35                 :            : #include <tinycrypt/utils.h>
      36                 :            : 
      37                 :          0 : int tc_ctr_mode(uint8_t *out, unsigned int outlen, const uint8_t *in,
      38                 :            :                 unsigned int inlen, uint8_t *ctr, const TCAesKeySched_t sched)
      39                 :            : {
      40                 :            : 
      41                 :          0 :         uint8_t buffer[TC_AES_BLOCK_SIZE];
      42                 :          0 :         uint8_t nonce[TC_AES_BLOCK_SIZE];
      43                 :          0 :         unsigned int block_num;
      44                 :          0 :         unsigned int i;
      45                 :            : 
      46                 :            :         /* input sanity check: */
      47                 :          0 :         if (out == (uint8_t *) 0 ||
      48         [ #  # ]:          0 :             in == (uint8_t *) 0 ||
      49                 :          0 :             ctr == (uint8_t *) 0 ||
      50         [ #  # ]:          0 :             sched == (TCAesKeySched_t) 0 ||
      51                 :          0 :             inlen == 0 ||
      52   [ #  #  #  # ]:          0 :             outlen == 0 ||
      53                 :            :             outlen != inlen) {
      54                 :            :                 return TC_CRYPTO_FAIL;
      55                 :            :         }
      56                 :            : 
      57                 :            :         /* copy the ctr to the nonce */
      58                 :          0 :         (void)_copy(nonce, sizeof(nonce), ctr, sizeof(nonce));
      59                 :            : 
      60                 :            :         /* select the last 4 bytes of the nonce to be incremented */
      61                 :          0 :         block_num = (nonce[12] << 24) | (nonce[13] << 16) |
      62                 :          0 :                     (nonce[14] << 8) | (nonce[15]);
      63         [ #  # ]:          0 :         for (i = 0; i < inlen; ++i) {
      64         [ #  # ]:          0 :                 if ((i % (TC_AES_BLOCK_SIZE)) == 0) {
      65                 :            :                         /* encrypt data using the current nonce */
      66         [ #  # ]:          0 :                         if (tc_aes_encrypt(buffer, nonce, sched)) {
      67                 :          0 :                                 block_num++;
      68                 :          0 :                                 nonce[12] = (uint8_t)(block_num >> 24);
      69                 :          0 :                                 nonce[13] = (uint8_t)(block_num >> 16);
      70                 :          0 :                                 nonce[14] = (uint8_t)(block_num >> 8);
      71                 :          0 :                                 nonce[15] = (uint8_t)(block_num);
      72                 :            :                         } else {
      73                 :            :                                 return TC_CRYPTO_FAIL;
      74                 :            :                         }
      75                 :            :                 }
      76                 :            :                 /* update the output */
      77                 :          0 :                 *out++ = buffer[i%(TC_AES_BLOCK_SIZE)] ^ *in++;
      78                 :            :         }
      79                 :            : 
      80                 :            :         /* update the counter */
      81                 :          0 :         ctr[12] = nonce[12]; ctr[13] = nonce[13];
      82                 :          0 :         ctr[14] = nonce[14]; ctr[15] = nonce[15];
      83                 :            : 
      84                 :          0 :         return TC_CRYPTO_SUCCESS;
      85                 :            : }