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/*
* AES-CTR cipher
* Copyright (c) 2015 Eran Kornblau <erankor at gmail dot com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <string.h>
#include "aes_ctr.h"
#include "aes.h"
#include "aes_internal.h"
#include "intreadwrite.h"
#include "macros.h"
#include "mem.h"
#include "random_seed.h"
#define AES_BLOCK_SIZE (16)
typedef struct AVAESCTR {
DECLARE_ALIGNED(8, uint8_t, counter)[AES_BLOCK_SIZE];
DECLARE_ALIGNED(8, uint8_t, encrypted_counter)[AES_BLOCK_SIZE];
AVAES aes;
} AVAESCTR;
struct AVAESCTR *av_aes_ctr_alloc(void)
{
return av_mallocz(sizeof(struct AVAESCTR));
}
void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
{
memcpy(a->counter, iv, AES_CTR_IV_SIZE);
memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
}
void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
{
memcpy(a->counter, iv, sizeof(a->counter));
}
const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
{
return a->counter;
}
void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
{
uint32_t iv[2];
iv[0] = av_get_random_seed();
iv[1] = av_get_random_seed();
av_aes_ctr_set_iv(a, (uint8_t*)iv);
}
int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
{
av_aes_init(&a->aes, key, 128, 0);
memset(a->counter, 0, sizeof(a->counter));
return 0;
}
void av_aes_ctr_free(struct AVAESCTR *a)
{
av_free(a);
}
static inline void av_aes_ctr_increment_be64(uint8_t* counter)
{
uint64_t c = AV_RB64A(counter) + 1;
AV_WB64A(counter, c);
}
void av_aes_ctr_increment_iv(struct AVAESCTR *a)
{
av_aes_ctr_increment_be64(a->counter);
memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
}
void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
{
while (count >= AES_BLOCK_SIZE) {
av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
av_aes_ctr_increment_be64(a->counter + 8);
#if HAVE_FAST_64BIT
for (int len = 0; len < AES_BLOCK_SIZE; len += 8)
AV_WN64(&dst[len], AV_RN64(&src[len]) ^ AV_RN64A(&a->encrypted_counter[len]));
#else
for (int len = 0; len < AES_BLOCK_SIZE; len += 4)
AV_WN32(&dst[len], AV_RN32(&src[len]) ^ AV_RN32A(&a->encrypted_counter[len]));
#endif
dst += AES_BLOCK_SIZE;
src += AES_BLOCK_SIZE;
count -= AES_BLOCK_SIZE;
}
if (count > 0) {
av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
av_aes_ctr_increment_be64(a->counter + 8);
for (int len = 0; len < count; len++)
dst[len] = src[len] ^ a->encrypted_counter[len];
}
}
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