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
|
/*
* Copyright (C) 2014-2016 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 "xof_bitspender.h"
#include "mgf1.h"
typedef struct private_xof_bitspender_t private_xof_bitspender_t;
/**
* Private data structure for xof_bitspender_t object
*/
struct private_xof_bitspender_t {
/**
* Public interface.
*/
xof_bitspender_t public;
/**
* Extended Output Function (XOF)
*/
xof_t *xof;
/**
* Length of the returned hash value in octets
*/
int hash_len;
/**
* 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;
/**
* Number of octets spent
*/
int octet_count;
};
static bool get_next_block(private_xof_bitspender_t *this, uint8_t *buffer)
{
if (!this->xof->get_bytes(this->xof, 4, buffer))
{
/* no block available */
return FALSE;
}
this->octet_count += 4;
return TRUE;
}
METHOD(xof_bitspender_t, get_bits, bool,
private_xof_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)
{
uint8_t buf[4];
if (!get_next_block(this, buf))
{
return FALSE;
}
this->bits = untoh32(buf);
this->bits_left = 32;
}
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(xof_bitspender_t, get_byte, bool,
private_xof_bitspender_t *this, uint8_t *byte)
{
if (this->bytes_left == 0)
{
if (!get_next_block(this, this->bytes))
{
return FALSE;
}
this->bytes_left = 4;
}
*byte = this->bytes[4 - this->bytes_left--];
return TRUE;
}
METHOD(xof_bitspender_t, destroy, void,
private_xof_bitspender_t *this)
{
DBG2(DBG_LIB, "%N generated %u octets", ext_out_function_names,
this->xof->get_type(this->xof), this->octet_count);
memwipe(this->bytes, 4);
this->xof->destroy(this->xof);
free(this);
}
/**
* See header.
*/
xof_bitspender_t *xof_bitspender_create(ext_out_function_t alg, chunk_t seed,
bool hash_seed)
{
private_xof_bitspender_t *this;
xof_t *xof;
xof = lib->crypto->create_xof(lib->crypto, alg);
if (!xof)
{
return NULL;
}
switch (alg)
{
case XOF_MGF1_SHA1:
case XOF_MGF1_SHA256:
case XOF_MGF1_SHA512:
{
mgf1_t *mgf1 = (mgf1_t*)xof;
mgf1->set_hash_seed(mgf1, hash_seed);
break;
}
default:
break;
}
if (!xof->set_seed(xof, seed))
{
xof->destroy(xof);
return NULL;
}
DBG2(DBG_LIB, "%N is seeded with %u octets", ext_out_function_names,
alg, seed.len);
INIT(this,
.public = {
.get_bits = _get_bits,
.get_byte = _get_byte,
.destroy = _destroy,
},
.xof = xof,
);
return &this->public;
}
|
