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135 lines
3.4 KiB
C
135 lines
3.4 KiB
C
/*
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* AES-CTR cipher
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* Copyright (c) 2015 Eran Kornblau <erankor at gmail dot com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "common.h"
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#include "aes_ctr.h"
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#include "aes.h"
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#include "random_seed.h"
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#define AES_BLOCK_SIZE (16)
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typedef struct AVAESCTR {
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struct AVAES* aes;
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uint8_t counter[AES_BLOCK_SIZE];
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uint8_t encrypted_counter[AES_BLOCK_SIZE];
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int block_offset;
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} AVAESCTR;
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struct AVAESCTR *av_aes_ctr_alloc(void)
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{
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return av_mallocz(sizeof(struct AVAESCTR));
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}
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void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
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{
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memcpy(a->counter, iv, AES_CTR_IV_SIZE);
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memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
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a->block_offset = 0;
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}
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void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
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{
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memcpy(a->counter, iv, sizeof(a->counter));
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a->block_offset = 0;
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}
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const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
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{
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return a->counter;
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}
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void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
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{
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uint32_t iv[2];
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iv[0] = av_get_random_seed();
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iv[1] = av_get_random_seed();
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av_aes_ctr_set_iv(a, (uint8_t*)iv);
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}
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int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
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{
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a->aes = av_aes_alloc();
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if (!a->aes) {
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return AVERROR(ENOMEM);
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}
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av_aes_init(a->aes, key, 128, 0);
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memset(a->counter, 0, sizeof(a->counter));
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a->block_offset = 0;
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return 0;
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}
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void av_aes_ctr_free(struct AVAESCTR *a)
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{
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if (a) {
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av_freep(&a->aes);
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av_free(a);
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}
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}
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static void av_aes_ctr_increment_be64(uint8_t* counter)
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{
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uint8_t* cur_pos;
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for (cur_pos = counter + 7; cur_pos >= counter; cur_pos--) {
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(*cur_pos)++;
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if (*cur_pos != 0) {
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break;
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}
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}
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}
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void av_aes_ctr_increment_iv(struct AVAESCTR *a)
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{
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av_aes_ctr_increment_be64(a->counter);
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memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
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a->block_offset = 0;
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}
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void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
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{
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const uint8_t* src_end = src + count;
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const uint8_t* cur_end_pos;
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uint8_t* encrypted_counter_pos;
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while (src < src_end) {
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if (a->block_offset == 0) {
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av_aes_crypt(a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
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av_aes_ctr_increment_be64(a->counter + 8);
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}
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encrypted_counter_pos = a->encrypted_counter + a->block_offset;
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cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
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cur_end_pos = FFMIN(cur_end_pos, src_end);
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a->block_offset += cur_end_pos - src;
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a->block_offset &= (AES_BLOCK_SIZE - 1);
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while (src < cur_end_pos) {
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*dst++ = *src++ ^ *encrypted_counter_pos++;
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}
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}
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}
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