aead-common.c
2.34 KB
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
/*
* Copyright (C) 2020 Southern Storm Software, Pty Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "aead-common.h"
int aead_check_tag
(unsigned char *plaintext, unsigned long long plaintext_len,
const unsigned char *tag1, const unsigned char *tag2,
unsigned size)
{
/* Set "accum" to -1 if the tags match, or 0 if they don't match */
int accum = 0;
while (size > 0) {
accum |= (*tag1++ ^ *tag2++);
--size;
}
accum = (accum - 1) >> 8;
/* Destroy the plaintext if the tag match failed */
while (plaintext_len > 0) {
*plaintext++ &= accum;
--plaintext_len;
}
/* If "accum" is 0, return -1, otherwise return 0 */
return ~accum;
}
int aead_check_tag_precheck
(unsigned char *plaintext, unsigned long long plaintext_len,
const unsigned char *tag1, const unsigned char *tag2,
unsigned size, int precheck)
{
/* Set "accum" to -1 if the tags match, or 0 if they don't match */
int accum = 0;
while (size > 0) {
accum |= (*tag1++ ^ *tag2++);
--size;
}
accum = ((accum - 1) >> 8) & precheck;
/* Destroy the plaintext if the tag match failed */
while (plaintext_len > 0) {
*plaintext++ &= accum;
--plaintext_len;
}
/* If "accum" is 0, return -1, otherwise return 0 */
return ~accum;
}