FFmpeg
aes_ctr.c
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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 "macros.h"
28 #include "mem.h"
29 #include "random_seed.h"
30 
31 #define AES_BLOCK_SIZE (16)
32 
33 typedef struct AVAESCTR {
38 } AVAESCTR;
39 
41 {
42  return av_mallocz(sizeof(struct AVAESCTR));
43 }
44 
45 void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
46 {
47  memcpy(a->counter, iv, AES_CTR_IV_SIZE);
48  memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
49  a->block_offset = 0;
50 }
51 
52 void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
53 {
54  memcpy(a->counter, iv, sizeof(a->counter));
55  a->block_offset = 0;
56 }
57 
58 const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
59 {
60  return a->counter;
61 }
62 
64 {
65  uint32_t iv[2];
66 
67  iv[0] = av_get_random_seed();
68  iv[1] = av_get_random_seed();
69 
70  av_aes_ctr_set_iv(a, (uint8_t*)iv);
71 }
72 
73 int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
74 {
75  av_aes_init(&a->aes, key, 128, 0);
76 
77  memset(a->counter, 0, sizeof(a->counter));
78  a->block_offset = 0;
79 
80  return 0;
81 }
82 
83 void av_aes_ctr_free(struct AVAESCTR *a)
84 {
85  av_free(a);
86 }
87 
88 static void av_aes_ctr_increment_be64(uint8_t* counter)
89 {
90  uint8_t* cur_pos;
91 
92  for (cur_pos = counter + 7; cur_pos >= counter; cur_pos--) {
93  (*cur_pos)++;
94  if (*cur_pos != 0) {
95  break;
96  }
97  }
98 }
99 
101 {
102  av_aes_ctr_increment_be64(a->counter);
103  memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
104  a->block_offset = 0;
105 }
106 
107 void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
108 {
109  const uint8_t* src_end = src + count;
110  const uint8_t* cur_end_pos;
111  uint8_t* encrypted_counter_pos;
112 
113  while (src < src_end) {
114  if (a->block_offset == 0) {
115  av_aes_crypt(&a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
116 
117  av_aes_ctr_increment_be64(a->counter + 8);
118  }
119 
120  encrypted_counter_pos = a->encrypted_counter + a->block_offset;
121  cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
122  cur_end_pos = FFMIN(cur_end_pos, src_end);
123 
124  a->block_offset += cur_end_pos - src;
125  a->block_offset &= (AES_BLOCK_SIZE - 1);
126 
127  while (src < cur_end_pos) {
128  *dst++ = *src++ ^ *encrypted_counter_pos++;
129  }
130  }
131 }
av_aes_init
int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
Initialize an AVAES context.
Definition: aes.c:201
AVAESCTR::block_offset
int block_offset
Definition: aes_ctr.c:36
av_aes_ctr_set_random_iv
void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
Generate a random iv.
Definition: aes_ctr.c:63
av_get_random_seed
uint32_t av_get_random_seed(void)
Get a seed to use in conjunction with random functions.
Definition: random_seed.c:121
macros.h
av_aes_ctr_get_iv
const uint8_t * av_aes_ctr_get_iv(struct AVAESCTR *a)
Get the current iv.
Definition: aes_ctr.c:58
AES_BLOCK_SIZE
#define AES_BLOCK_SIZE
Definition: aes_ctr.c:31
key
const char * key
Definition: hwcontext_opencl.c:174
AVAESCTR::aes
AVAES aes
Definition: aes_ctr.c:37
aes.h
NULL
#define NULL
Definition: coverity.c:32
av_aes_ctr_alloc
struct AVAESCTR * av_aes_ctr_alloc(void)
Allocate an AVAESCTR context.
Definition: aes_ctr.c:40
av_aes_crypt
void av_aes_crypt(AVAES *a, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt)
Encrypt or decrypt a buffer using a previously initialized context.
Definition: aes.c:169
av_aes_ctr_init
int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
Initialize an AVAESCTR context.
Definition: aes_ctr.c:73
av_aes_ctr_set_iv
void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t *iv)
Forcefully change the 8-byte iv.
Definition: aes_ctr.c:45
av_aes_ctr_set_full_iv
void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t *iv)
Forcefully change the "full" 16-byte iv, including the counter.
Definition: aes_ctr.c:52
aes_ctr.h
AVAESCTR::encrypted_counter
uint8_t encrypted_counter[AES_BLOCK_SIZE]
Definition: aes_ctr.c:35
a
The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a
Definition: undefined.txt:41
aes_internal.h
av_aes_ctr_free
void av_aes_ctr_free(struct AVAESCTR *a)
Release an AVAESCTR context.
Definition: aes_ctr.c:83
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
av_mallocz
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:264
AVAES
Definition: aes_internal.h:34
random_seed.h
AVAESCTR::counter
uint8_t counter[AES_BLOCK_SIZE]
Definition: aes_ctr.c:34
av_aes_ctr_increment_iv
void av_aes_ctr_increment_iv(struct AVAESCTR *a)
Increment the top 64 bit of the iv (performed after each frame)
Definition: aes_ctr.c:100
av_aes_ctr_crypt
void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
Process a buffer using a previously initialized context.
Definition: aes_ctr.c:107
mem.h
av_free
#define av_free(p)
Definition: tableprint_vlc.h:33
src
INIT_CLIP pixel * src
Definition: h264pred_template.c:418
AES_CTR_IV_SIZE
#define AES_CTR_IV_SIZE
Definition: aes_ctr.h:36
av_aes_ctr_increment_be64
static void av_aes_ctr_increment_be64(uint8_t *counter)
Definition: aes_ctr.c:88
AVAESCTR
Definition: aes_ctr.c:33