/*

 * 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];

    int block_offset;

    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);

    a->block_offset = 0;

}

void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)

{

    memcpy(a->counter, iv, sizeof(a->counter));

    a->block_offset = 0;

}

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));

    a->block_offset = 0;

    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);

    a->block_offset = 0;

}

void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)

{

    if (a->block_offset && count > 0) {

        int left = FFMIN(count, AES_BLOCK_SIZE - a->block_offset);

        for (int len = 0; len < left; len++)

            dst[len] = src[len] ^ a->encrypted_counter[a->block_offset++];

        a->block_offset &= AES_BLOCK_SIZE - 1;

        dst += left;

        src += left;

        count -= left;

    }

    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[a->block_offset++];

    }

}