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
|
/*
* Copyright (C) 2014 Andreas Steffen
* HSR Hochschule fuer Technik Rapperswil
*
* 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. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* 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 General Public License
* for more details.
*/
#include "mgf1_bitspender.h"
#include <crypto/mgf1/mgf1.h>
typedef struct private_mgf1_bitspender_t private_mgf1_bitspender_t;
/**
* Private data structure for mgf1_bitspender_t object
*/
struct private_mgf1_bitspender_t {
/**
* Public interface.
*/
mgf1_bitspender_t public;
/**
* MGF1 bit mask generator
*/
mgf1_t *mgf1;
/**
* Octet storage (accommodates up to 64 octets)
*/
uint8_t octets[HASH_SIZE_SHA512];
/**
* Length of the returned hash value in octets
*/
int hash_len;
/**
* Number of generated octets
*/
int octets_count;
/**
* Number of available octets
*/
int octets_left;
/**
* Bit storage (accommodates up to 32 bits)
*/
uint32_t bits;
/**
* Number of available bits
*/
int bits_left;
/**
* Byte storage (accommodates up to 4 bytes)
*/
uint8_t bytes[4];
/**
* Number of available bytes
*/
int bytes_left;
};
METHOD(mgf1_bitspender_t, get_bits, bool,
private_mgf1_bitspender_t *this, int bits_needed, uint32_t *bits)
{
int bits_now;
*bits = 0x00000000;
if (bits_needed == 0)
{
/* trivial */
return TRUE;
}
if (bits_needed > 32)
{
/* too many bits requested */
return FALSE;
}
while (bits_needed)
{
if (this->bits_left == 0)
{
if (this->octets_left == 0)
{
/* get another block from MGF1 */
if (!this->mgf1->get_mask(this->mgf1, this->hash_len,
this->octets))
{
/* no block available */
return FALSE;
}
this->octets_left = this->hash_len;
this->octets_count += this->hash_len;
}
this->bits = untoh32(this->octets + this->hash_len -
this->octets_left);
this->bits_left = 32;
this->octets_left -= 4;
}
if (bits_needed > this->bits_left)
{
bits_now = this->bits_left;
this->bits_left = 0;
bits_needed -= bits_now;
}
else
{
bits_now = bits_needed;
this->bits_left -= bits_needed;
bits_needed = 0;
}
if (bits_now == 32)
{
*bits = this->bits;
}
else
{
*bits <<= bits_now;
*bits |= this->bits >> this->bits_left;
if (this->bits_left)
{
this->bits &= 0xffffffff >> (32 - this->bits_left);
}
}
}
return TRUE;
}
METHOD(mgf1_bitspender_t, get_byte, bool,
private_mgf1_bitspender_t *this, uint8_t *byte)
{
if (this->bytes_left == 0)
{
if (this->octets_left == 0)
{
/* get another block from MGF1 */
if (!this->mgf1->get_mask(this->mgf1, this->hash_len, this->octets))
{
/* no block available */
return FALSE;
}
this->octets_left = this->hash_len;
this->octets_count += this->hash_len;
}
memcpy(this->bytes, this->octets + this->hash_len - this->octets_left, 4);
this->bytes_left = 4;
this->octets_left -= 4;
}
*byte = this->bytes[4 - this->bytes_left--];
return TRUE;
}
METHOD(mgf1_bitspender_t, destroy, void,
private_mgf1_bitspender_t *this)
{
DBG2(DBG_LIB, "mgf1 generated %u octets", this->octets_count);
memwipe(this->octets, sizeof(this->octets));
this->mgf1->destroy(this->mgf1);
free(this);
}
/**
* See header.
*/
mgf1_bitspender_t *mgf1_bitspender_create(hash_algorithm_t alg, chunk_t seed,
bool hash_seed)
{
private_mgf1_bitspender_t *this;
mgf1_t *mgf1;
mgf1 = mgf1_create(alg, seed, hash_seed);
if (!mgf1)
{
return NULL;
}
DBG2(DBG_LIB, "mgf1 based on %N is seeded with %u octets",
hash_algorithm_short_names, alg, seed.len);
INIT(this,
.public = {
.get_bits = _get_bits,
.get_byte = _get_byte,
.destroy = _destroy,
},
.mgf1 = mgf1,
.hash_len = mgf1->get_hash_size(mgf1),
);
return &this->public;
}
|
