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
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
/*
* AFsplitter - Anti forensic information splitter
*
* Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>
* Copyright (C) 2009-2024 Red Hat, Inc. All rights reserved.
*
* AFsplitter diffuses information over a large stripe of data,
* therefore supporting secure data destruction.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "internal.h"
#include "af.h"
static void XORblock(const char *src1, const char *src2, char *dst, size_t n)
{
size_t j;
for (j = 0; j < n; j++)
dst[j] = src1[j] ^ src2[j];
}
static int hash_buf(const char *src, char *dst, uint32_t iv,
size_t len, const char *hash_name)
{
struct crypt_hash *hd = NULL;
char *iv_char = (char *)&iv;
int r;
iv = be32_to_cpu(iv);
if (crypt_hash_init(&hd, hash_name))
return -EINVAL;
if ((r = crypt_hash_write(hd, iv_char, sizeof(uint32_t))))
goto out;
if ((r = crypt_hash_write(hd, src, len)))
goto out;
r = crypt_hash_final(hd, dst, len);
out:
crypt_hash_destroy(hd);
return r;
}
/*
* diffuse: Information spreading over the whole dataset with
* the help of hash function.
*/
static int diffuse(char *src, char *dst, size_t size, const char *hash_name)
{
int r, hash_size = crypt_hash_size(hash_name);
unsigned int digest_size;
unsigned int i, blocks, padding;
if (hash_size <= 0)
return -EINVAL;
digest_size = hash_size;
blocks = size / digest_size;
padding = size % digest_size;
for (i = 0; i < blocks; i++) {
r = hash_buf(src + digest_size * i,
dst + digest_size * i,
i, (size_t)digest_size, hash_name);
if (r < 0)
return r;
}
if (padding) {
r = hash_buf(src + digest_size * i,
dst + digest_size * i,
i, (size_t)padding, hash_name);
if (r < 0)
return r;
}
return 0;
}
/*
* Information splitting. The amount of data is multiplied by
* blocknumbers. The same blocksize and blocknumbers values
* must be supplied to AF_merge to recover information.
*/
int AF_split(struct crypt_device *ctx, const char *src, char *dst,
size_t blocksize, unsigned int blocknumbers, const char *hash)
{
unsigned int i;
char *bufblock;
int r;
bufblock = crypt_safe_alloc(blocksize);
if (!bufblock)
return -ENOMEM;
/* process everything except the last block */
for (i = 0; i < blocknumbers - 1; i++) {
r = crypt_random_get(ctx, dst + blocksize * i, blocksize, CRYPT_RND_NORMAL);
if (r < 0)
goto out;
XORblock(dst + blocksize * i, bufblock, bufblock, blocksize);
r = diffuse(bufblock, bufblock, blocksize, hash);
if (r < 0)
goto out;
}
/* the last block is computed */
XORblock(src, bufblock, dst + blocksize * i, blocksize);
r = 0;
out:
crypt_safe_free(bufblock);
return r;
}
int AF_merge(const char *src, char *dst,
size_t blocksize, unsigned int blocknumbers, const char *hash)
{
unsigned int i;
char *bufblock;
int r;
bufblock = crypt_safe_alloc(blocksize);
if (!bufblock)
return -ENOMEM;
for (i = 0; i < blocknumbers - 1; i++) {
XORblock(src + blocksize * i, bufblock, bufblock, blocksize);
r = diffuse(bufblock, bufblock, blocksize, hash);
if (r < 0)
goto out;
}
XORblock(src + blocksize * i, bufblock, dst, blocksize);
r = 0;
out:
crypt_safe_free(bufblock);
return r;
}
/* Size of final split data including sector alignment */
size_t AF_split_sectors(size_t blocksize, unsigned int blocknumbers)
{
size_t af_size;
/* data material * stripes */
af_size = blocksize * blocknumbers;
/* round up to sector */
af_size = (af_size + (SECTOR_SIZE - 1)) / SECTOR_SIZE;
return af_size;
}
|
