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
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
|
/*
* Implementation of Password-Based Cryptography as per PKCS#5
* Copyright (C) 2002,2003 Simon Josefsson
* Copyright (C) 2004 Free Software Foundation
*
* cryptsetup related changes
* Copyright (C) 2012-2024 Red Hat, Inc. All rights reserved.
* Copyright (C) 2012-2024 Milan Broz
*
* This file is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This file 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this file; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
#include <errno.h>
#include <alloca.h>
#include "crypto_backend_internal.h"
static int hash_buf(const char *src, size_t src_len,
char *dst, size_t dst_len,
const char *hash_name)
{
struct crypt_hash *hd = NULL;
int r;
if (crypt_hash_init(&hd, hash_name))
return -EINVAL;
r = crypt_hash_write(hd, src, src_len);
if (!r)
r = crypt_hash_final(hd, dst, dst_len);
crypt_hash_destroy(hd);
return r;
}
/*
* 5.2 PBKDF2
*
* PBKDF2 applies a pseudorandom function (see Appendix B.1 for an
* example) to derive keys. The length of the derived key is essentially
* unbounded. (However, the maximum effective search space for the
* derived key may be limited by the structure of the underlying
* pseudorandom function. See Appendix B.1 for further discussion.)
* PBKDF2 is recommended for new applications.
*
* PBKDF2 (P, S, c, dkLen)
*
* Options: PRF underlying pseudorandom function (hLen
* denotes the length in octets of the
* pseudorandom function output)
*
* Input: P password, an octet string (ASCII or UTF-8)
* S salt, an octet string
* c iteration count, a positive integer
* dkLen intended length in octets of the derived
* key, a positive integer, at most
* (2^32 - 1) * hLen
*
* Output: DK derived key, a dkLen-octet string
*/
/*
* if hash_block_size is not zero, the HMAC key is pre-hashed
* inside this function.
* This prevents situation when crypto backend doesn't support
* long HMAC keys or it tries hash long key in every iteration
* (because of crypt_final() cannot do simple key reset.
*/
#define MAX_PRF_BLOCK_LEN 80
int pkcs5_pbkdf2(const char *hash,
const char *P, size_t Plen,
const char *S, size_t Slen,
unsigned int c, unsigned int dkLen,
char *DK, unsigned int hash_block_size)
{
struct crypt_hmac *hmac;
char U[MAX_PRF_BLOCK_LEN];
char T[MAX_PRF_BLOCK_LEN];
char P_hash[MAX_PRF_BLOCK_LEN];
int i, k, rc = -EINVAL;
unsigned int u, hLen, l, r;
size_t tmplen = Slen + 4;
char *tmp;
tmp = alloca(tmplen);
if (tmp == NULL)
return -ENOMEM;
hLen = crypt_hmac_size(hash);
if (hLen == 0 || hLen > MAX_PRF_BLOCK_LEN)
return -EINVAL;
if (c == 0)
return -EINVAL;
if (dkLen == 0)
return -EINVAL;
/*
*
* Steps:
*
* 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long" and
* stop.
*/
if (dkLen > 4294967295U)
return -EINVAL;
/*
* 2. Let l be the number of hLen-octet blocks in the derived key,
* rounding up, and let r be the number of octets in the last
* block:
*
* l = CEIL (dkLen / hLen) ,
* r = dkLen - (l - 1) * hLen .
*
* Here, CEIL (x) is the "ceiling" function, i.e. the smallest
* integer greater than, or equal to, x.
*/
l = dkLen / hLen;
if (dkLen % hLen)
l++;
r = dkLen - (l - 1) * hLen;
/*
* 3. For each block of the derived key apply the function F defined
* below to the password P, the salt S, the iteration count c, and
* the block index to compute the block:
*
* T_1 = F (P, S, c, 1) ,
* T_2 = F (P, S, c, 2) ,
* ...
* T_l = F (P, S, c, l) ,
*
* where the function F is defined as the exclusive-or sum of the
* first c iterates of the underlying pseudorandom function PRF
* applied to the password P and the concatenation of the salt S
* and the block index i:
*
* F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
*
* where
*
* U_1 = PRF (P, S || INT (i)) ,
* U_2 = PRF (P, U_1) ,
* ...
* U_c = PRF (P, U_{c-1}) .
*
* Here, INT (i) is a four-octet encoding of the integer i, most
* significant octet first.
*
* 4. Concatenate the blocks and extract the first dkLen octets to
* produce a derived key DK:
*
* DK = T_1 || T_2 || ... || T_l<0..r-1>
*
* 5. Output the derived key DK.
*
* Note. The construction of the function F follows a "belt-and-
* suspenders" approach. The iterates U_i are computed recursively to
* remove a degree of parallelism from an opponent; they are exclusive-
* ored together to reduce concerns about the recursion degenerating
* into a small set of values.
*
*/
/* If hash_block_size is provided, hash password in advance. */
if (hash_block_size > 0 && Plen > hash_block_size) {
if (hash_buf(P, Plen, P_hash, hLen, hash))
return -EINVAL;
if (crypt_hmac_init(&hmac, hash, P_hash, hLen))
return -EINVAL;
crypt_backend_memzero(P_hash, sizeof(P_hash));
} else {
if (crypt_hmac_init(&hmac, hash, P, Plen))
return -EINVAL;
}
for (i = 1; (unsigned int) i <= l; i++) {
memset(T, 0, hLen);
for (u = 1; u <= c ; u++) {
if (u == 1) {
memcpy(tmp, S, Slen);
tmp[Slen + 0] = (i & 0xff000000) >> 24;
tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
tmp[Slen + 3] = (i & 0x000000ff) >> 0;
if (crypt_hmac_write(hmac, tmp, tmplen))
goto out;
} else {
if (crypt_hmac_write(hmac, U, hLen))
goto out;
}
if (crypt_hmac_final(hmac, U, hLen))
goto out;
for (k = 0; (unsigned int) k < hLen; k++)
T[k] ^= U[k];
}
memcpy(DK + (i - 1) * hLen, T, (unsigned int) i == l ? r : hLen);
}
rc = 0;
out:
crypt_hmac_destroy(hmac);
crypt_backend_memzero(U, sizeof(U));
crypt_backend_memzero(T, sizeof(T));
crypt_backend_memzero(tmp, tmplen);
return rc;
}
|
