libavutil/aes_ctr.c

   1 /*
   2  * AES-CTR cipher
   3  * Copyright (c) 2015 Eran Kornblau <erankor at gmail dot com>
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <string.h>
  23
  24 #include "aes_ctr.h"
  25 #include "aes.h"
  26 #include "aes_internal.h"
  27 #include "intreadwrite.h"
  28 #include "macros.h"
  29 #include "mem.h"
  30 #include "random_seed.h"
  31
  32 #define AES_BLOCK_SIZE (16)
  33
  34 typedef struct AVAESCTR {
  35     DECLARE_ALIGNED(8, uint8_t, counter)[AES_BLOCK_SIZE];
  36     DECLARE_ALIGNED(8, uint8_t, encrypted_counter)[AES_BLOCK_SIZE];
  37     int block_offset;
  38     AVAES aes;
  39 } AVAESCTR;
  40
  41 struct AVAESCTR *av_aes_ctr_alloc(void)
  42 {
  43     return av_mallocz(sizeof(struct AVAESCTR));
  44 }
  45
  46 void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
  47 {
  48     memcpy(a->counter, iv, AES_CTR_IV_SIZE);
  49     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
  50     a->block_offset = 0;
  51 }
  52
  53 void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
  54 {
  55     memcpy(a->counter, iv, sizeof(a->counter));
  56     a->block_offset = 0;
  57 }
  58
  59 const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
  60 {
  61     return a->counter;
  62 }
  63
  64 void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
  65 {
  66     uint32_t iv[2];
  67
  68     iv[0] = av_get_random_seed();
  69     iv[1] = av_get_random_seed();
  70
  71     av_aes_ctr_set_iv(a, (uint8_t*)iv);
  72 }
  73
  74 int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
  75 {
  76     av_aes_init(&a->aes, key, 128, 0);
  77
  78     memset(a->counter, 0, sizeof(a->counter));
  79     a->block_offset = 0;
  80
  81     return 0;
  82 }
  83
  84 void av_aes_ctr_free(struct AVAESCTR *a)
  85 {
  86     av_free(a);
  87 }
  88
  89 static inline void av_aes_ctr_increment_be64(uint8_t* counter)
  90 {
  91     uint64_t c = AV_RB64A(counter) + 1;
  92     AV_WB64A(counter, c);
  93 }
  94
  95 void av_aes_ctr_increment_iv(struct AVAESCTR *a)
  96 {
  97     av_aes_ctr_increment_be64(a->counter);
  98     memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
  99     a->block_offset = 0;
 100 }
 101
 102 void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
 103 {
 104     if (a->block_offset && count > 0) {
 105         int left = FFMIN(count, AES_BLOCK_SIZE - a->block_offset);
 106         for (int len = 0; len < left; len++)
 107             dst[len] = src[len] ^ a->encrypted_counter[a->block_offset++];
 108         a->block_offset &= AES_BLOCK_SIZE - 1;
 109         dst += left;
 110         src += left;
 111         count -= left;
 112     }
 113
 114     while (count >= AES_BLOCK_SIZE) {
 115         av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
 116         av_aes_ctr_increment_be64(a->counter + 8);
 117 #if HAVE_FAST_64BIT
 118         for (int len = 0; len < AES_BLOCK_SIZE; len += 8)
 119             AV_WN64(&dst[len], AV_RN64(&src[len]) ^ AV_RN64A(&a->encrypted_counter[len]));
 120 #else
 121         for (int len = 0; len < AES_BLOCK_SIZE; len += 4)
 122             AV_WN32(&dst[len], AV_RN32(&src[len]) ^ AV_RN32A(&a->encrypted_counter[len]));
 123 #endif
 124         dst += AES_BLOCK_SIZE;
 125         src += AES_BLOCK_SIZE;
 126         count -= AES_BLOCK_SIZE;
 127     }
 128
 129     if (count > 0) {
 130         av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
 131         av_aes_ctr_increment_be64(a->counter + 8);
 132         for (int len = 0; len < count; len++)
 133             dst[len] = src[len] ^ a->encrypted_counter[a->block_offset++];
 134     }
 135 }