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/* cbc_mode.c - TinyCrypt implementation of CBC mode encryption & decryption */
/*
* Copyright (C) 2015 by Intel Corporation, All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <cbc_mode.h>
#include <utils.h>
int32_t tc_cbc_mode_encrypt(uint8_t *out, uint32_t outlen, const uint8_t *in,
uint32_t inlen, const uint8_t *iv, const TCAesKeySched_t sched)
{
uint8_t buffer[TC_AES_BLOCK_SIZE];
uint32_t n, m;
/* input sanity check: */
if (out == (uint8_t *) 0 ||
in == (const uint8_t *) 0 ||
sched == (TCAesKeySched_t) 0 ||
inlen == 0 ||
outlen == 0 ||
(inlen % TC_AES_BLOCK_SIZE) != 0 ||
(outlen % TC_AES_BLOCK_SIZE) != 0 ||
outlen != inlen + TC_AES_BLOCK_SIZE) {
return TC_FAIL;
}
/* copy iv to the buffer */
(void)_copy(buffer, TC_AES_BLOCK_SIZE, iv, TC_AES_BLOCK_SIZE);
/* copy iv to the output buffer */
(void)_copy(out, TC_AES_BLOCK_SIZE, iv, TC_AES_BLOCK_SIZE);
out += TC_AES_BLOCK_SIZE;
for (n = m = 0; n < inlen; ++n) {
buffer[m++] ^= *in++;
if (m == TC_AES_BLOCK_SIZE) {
(void)tc_aes_encrypt(buffer, buffer, sched);
(void)_copy(out, TC_AES_BLOCK_SIZE, buffer, TC_AES_BLOCK_SIZE);
out += TC_AES_BLOCK_SIZE;
m = 0;
}
}
return TC_SUCCESS;
}
int32_t tc_cbc_mode_decrypt(uint8_t *out, uint32_t outlen, const uint8_t *in,
uint32_t inlen, const uint8_t *iv, const TCAesKeySched_t sched)
{
uint8_t buffer[TC_AES_BLOCK_SIZE];
const uint8_t *p;
uint32_t n, m;
/* sanity check the inputs */
if (out == (uint8_t *) 0 ||
in == (const uint8_t *) 0 ||
sched == (TCAesKeySched_t) 0 ||
inlen == 0 ||
outlen == 0 ||
(inlen % TC_AES_BLOCK_SIZE) != 0 ||
(outlen % TC_AES_BLOCK_SIZE) != 0 ||
outlen != inlen - TC_AES_BLOCK_SIZE) {
return TC_FAIL;
}
/* Note that in == iv + ciphertext, i.e. the iv and the ciphertext are
* contiguous. This allows for a very efficient decryption algorithm that
* would not otherwise be possible. */
p = iv;
for (n = m = 0; n < inlen; ++n) {
if ((n % TC_AES_BLOCK_SIZE) == 0) {
(void)tc_aes_decrypt(buffer, in, sched);
in += TC_AES_BLOCK_SIZE;
m = 0;
}
*out++ = buffer[m++] ^ *p++;
}
return TC_SUCCESS;
}
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