1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
|
#include <stdint.h>
#include <stdlib.h>
#include "crypto_aes.h"
#include "insecure_memzero.h"
#include "sysendian.h"
#include "crypto_aesctr.h"
struct crypto_aesctr {
const struct crypto_aes_key * key;
uint64_t nonce;
uint64_t bytectr;
uint8_t buf[16];
};
/**
* crypto_aesctr_init(key, nonce):
* Prepare to encrypt/decrypt data with AES in CTR mode, using the provided
* expanded key and nonce. The key provided must remain valid for the
* lifetime of the stream.
*/
struct crypto_aesctr *
crypto_aesctr_init(const struct crypto_aes_key * key, uint64_t nonce)
{
struct crypto_aesctr * stream;
/* Allocate memory. */
if ((stream = malloc(sizeof(struct crypto_aesctr))) == NULL)
goto err0;
/* Initialize values. */
stream->key = key;
stream->nonce = nonce;
stream->bytectr = 0;
/* Success! */
return (stream);
err0:
/* Failure! */
return (NULL);
}
/**
* crypto_aesctr_stream(stream, inbuf, outbuf, buflen):
* Generate the next ${buflen} bytes of the AES-CTR stream and xor them with
* bytes from ${inbuf}, writing the result into ${outbuf}. If the buffers
* ${inbuf} and ${outbuf} overlap, they must be identical.
*/
void
crypto_aesctr_stream(struct crypto_aesctr * stream, const uint8_t * inbuf,
uint8_t * outbuf, size_t buflen)
{
uint8_t pblk[16];
size_t pos;
int bytemod;
for (pos = 0; pos < buflen; pos++) {
/* How far through the buffer are we? */
bytemod = stream->bytectr % 16;
/* Generate a block of cipherstream if needed. */
if (bytemod == 0) {
be64enc(pblk, stream->nonce);
be64enc(pblk + 8, stream->bytectr / 16);
crypto_aes_encrypt_block(pblk, stream->buf,
stream->key);
}
/* Encrypt a byte. */
outbuf[pos] = inbuf[pos] ^ stream->buf[bytemod];
/* Move to the next byte of cipherstream. */
stream->bytectr += 1;
}
}
/**
* crypto_aesctr_free(stream):
* Free the provided stream object.
*/
void
crypto_aesctr_free(struct crypto_aesctr * stream)
{
/* Behave consistently with free(NULL). */
if (stream == NULL)
return;
/* Zero potentially sensitive information. */
insecure_memzero(stream, sizeof(struct crypto_aesctr));
/* Free the stream. */
free(stream);
}
/**
* crypto_aesctr_buf(key, nonce, inbuf, outbuf, buflen):
* Equivalent to init(key, nonce); stream(inbuf, outbuf, buflen); free.
*/
void
crypto_aesctr_buf(const struct crypto_aes_key * key, uint64_t nonce,
const uint8_t * inbuf, uint8_t * outbuf, size_t buflen)
{
struct crypto_aesctr stream_rec;
struct crypto_aesctr * stream = &stream_rec;
/* Initialize values. */
stream->key = key;
stream->nonce = nonce;
stream->bytectr = 0;
/* Perform the encryption. */
crypto_aesctr_stream(stream, inbuf, outbuf, buflen);
/* Zero potentially sensitive information. */
insecure_memzero(stream, sizeof(struct crypto_aesctr));
}
|
