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 "common.h"
23 #include "aes_ctr.h"
24 #include "aes.h"
25 #include "random_seed.h"
26 
27 #define AES_BLOCK_SIZE (16)
28 
29 typedef struct AVAESCTR {
30  struct AVAES* aes;
34 } AVAESCTR;
35 
37 {
38  return av_mallocz(sizeof(struct AVAESCTR));
39 }
40 
41 void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
42 {
43  memcpy(a->counter, iv, AES_CTR_IV_SIZE);
44  memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
45  a->block_offset = 0;
46 }
47 
48 void av_aes_ctr_set_full_iv(struct AVAESCTR *a, const uint8_t* iv)
49 {
50  memcpy(a->counter, iv, sizeof(a->counter));
51  a->block_offset = 0;
52 }
53 
55 {
56  return a->counter;
57 }
58 
60 {
61  uint32_t iv[2];
62 
63  iv[0] = av_get_random_seed();
64  iv[1] = av_get_random_seed();
65 
66  av_aes_ctr_set_iv(a, (uint8_t*)iv);
67 }
68 
69 int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
70 {
71  a->aes = av_aes_alloc();
72  if (!a->aes) {
73  return AVERROR(ENOMEM);
74  }
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  if (a) {
87  av_freep(&a->aes);
88  av_free(a);
89  }
90 }
91 
93 {
94  uint8_t* cur_pos;
95 
96  for (cur_pos = counter + 7; cur_pos >= counter; cur_pos--) {
97  (*cur_pos)++;
98  if (*cur_pos != 0) {
99  break;
100  }
101  }
102 }
103 
105 {
107  memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
108  a->block_offset = 0;
109 }
110 
111 void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
112 {
113  const uint8_t* src_end = src + count;
114  const uint8_t* cur_end_pos;
115  uint8_t* encrypted_counter_pos;
116 
117  while (src < src_end) {
118  if (a->block_offset == 0) {
119  av_aes_crypt(a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
120 
122  }
123 
124  encrypted_counter_pos = a->encrypted_counter + a->block_offset;
125  cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
126  cur_end_pos = FFMIN(cur_end_pos, src_end);
127 
128  a->block_offset += cur_end_pos - src;
129  a->block_offset &= (AES_BLOCK_SIZE - 1);
130 
131  while (src < cur_end_pos) {
132  *dst++ = *src++ ^ *encrypted_counter_pos++;
133  }
134  }
135 }
uint8_t counter[AES_BLOCK_SIZE]
Definition: aes_ctr.c:31
#define NULL
Definition: coverity.c:32
int block_offset
Definition: aes_ctr.c:33
static void av_aes_ctr_increment_be64(uint8_t *counter)
Definition: aes_ctr.c:92
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:163
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:104
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:36
const char * key
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:236
#define src
Definition: vp8dsp.c:254
uint8_t encrypted_counter[AES_BLOCK_SIZE]
Definition: aes_ctr.c:32
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:111
uint8_t
void av_aes_ctr_free(struct AVAESCTR *a)
Release an AVAESCTR context.
Definition: aes_ctr.c:84
struct AVAES * av_aes_alloc(void)
Allocate an AVAES context.
Definition: aes.c:31
GLsizei count
Definition: opengl_enc.c:108
struct AVAESCTR * av_aes_ctr_alloc(void)
Allocate an AVAESCTR context.
Definition: aes_ctr.c:36
#define FFMIN(a, b)
Definition: common.h:96
void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
Generate a random iv.
Definition: aes_ctr.c:59
int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
Initialize an AVAES context.
Definition: aes.c:195
#define AES_BLOCK_SIZE
Definition: aes_ctr.c:27
void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t *iv)
Forcefully change the 8-byte iv.
Definition: aes_ctr.c:41
common internal and external API header
#define av_free(p)
int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
Initialize an AVAESCTR context.
Definition: aes_ctr.c:69
#define av_freep(p)
uint32_t av_get_random_seed(void)
Get a seed to use in conjunction with random functions.
Definition: random_seed.c:120
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:48
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
#define AES_CTR_IV_SIZE
Definition: aes_ctr.h:31
const uint8_t * av_aes_ctr_get_iv(struct AVAESCTR *a)
Get the current iv.
Definition: aes_ctr.c:54
struct AVAES * aes
Definition: aes_ctr.c:30