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
|
/*
* PSSR
* (C) 1999-2007,2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/pssr.h>
#include <botan/mgf1.h>
#include <botan/internal/bit_ops.h>
namespace Botan {
namespace {
/*
* PSSR Encode Operation
*/
secure_vector<uint8_t> pss_encode(HashFunction& hash,
const secure_vector<uint8_t>& msg,
const secure_vector<uint8_t>& salt,
size_t output_bits)
{
const size_t HASH_SIZE = hash.output_length();
const size_t SALT_SIZE = salt.size();
if(msg.size() != HASH_SIZE)
throw Encoding_Error("Cannot encode PSS string, input length invalid for hash");
if(output_bits < 8*HASH_SIZE + 8*SALT_SIZE + 9)
throw Encoding_Error("Cannot encode PSS string, output length too small");
const size_t output_length = (output_bits + 7) / 8;
for(size_t i = 0; i != 8; ++i)
hash.update(0);
hash.update(msg);
hash.update(salt);
secure_vector<uint8_t> H = hash.final();
secure_vector<uint8_t> EM(output_length);
EM[output_length - HASH_SIZE - SALT_SIZE - 2] = 0x01;
buffer_insert(EM, output_length - 1 - HASH_SIZE - SALT_SIZE, salt);
mgf1_mask(hash, H.data(), HASH_SIZE, EM.data(), output_length - HASH_SIZE - 1);
EM[0] &= 0xFF >> (8 * ((output_bits + 7) / 8) - output_bits);
buffer_insert(EM, output_length - 1 - HASH_SIZE, H);
EM[output_length-1] = 0xBC;
return EM;
}
bool pss_verify(HashFunction& hash,
const secure_vector<uint8_t>& const_coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
const size_t HASH_SIZE = hash.output_length();
const size_t KEY_BYTES = (key_bits + 7) / 8;
if(key_bits < 8*HASH_SIZE + 9)
return false;
if(raw.size() != HASH_SIZE)
return false;
if(const_coded.size() > KEY_BYTES || const_coded.size() <= 1)
return false;
if(const_coded[const_coded.size()-1] != 0xBC)
return false;
secure_vector<uint8_t> coded = const_coded;
if(coded.size() < KEY_BYTES)
{
secure_vector<uint8_t> temp(KEY_BYTES);
buffer_insert(temp, KEY_BYTES - coded.size(), coded);
coded = temp;
}
const size_t TOP_BITS = 8 * ((key_bits + 7) / 8) - key_bits;
if(TOP_BITS > 8 - high_bit(coded[0]))
return false;
uint8_t* DB = coded.data();
const size_t DB_size = coded.size() - HASH_SIZE - 1;
const uint8_t* H = &coded[DB_size];
const size_t H_size = HASH_SIZE;
mgf1_mask(hash, H, H_size, DB, DB_size);
DB[0] &= 0xFF >> TOP_BITS;
size_t salt_offset = 0;
for(size_t j = 0; j != DB_size; ++j)
{
if(DB[j] == 0x01)
{ salt_offset = j + 1; break; }
if(DB[j])
return false;
}
if(salt_offset == 0)
return false;
const size_t salt_size = DB_size - salt_offset;
for(size_t j = 0; j != 8; ++j)
hash.update(0);
hash.update(raw);
hash.update(&DB[salt_offset], salt_size);
secure_vector<uint8_t> H2 = hash.final();
return constant_time_compare(H, H2.data(), HASH_SIZE);
}
}
PSSR::PSSR(HashFunction* h) :
m_hash(h), m_SALT_SIZE(m_hash->output_length())
{
}
PSSR::PSSR(HashFunction* h, size_t salt_size) :
m_hash(h), m_SALT_SIZE(salt_size)
{
}
/*
* PSSR Update Operation
*/
void PSSR::update(const uint8_t input[], size_t length)
{
m_hash->update(input, length);
}
/*
* Return the raw (unencoded) data
*/
secure_vector<uint8_t> PSSR::raw_data()
{
return m_hash->final();
}
secure_vector<uint8_t> PSSR::encoding_of(const secure_vector<uint8_t>& msg,
size_t output_bits,
RandomNumberGenerator& rng)
{
secure_vector<uint8_t> salt = rng.random_vec(m_SALT_SIZE);
return pss_encode(*m_hash, msg, salt, output_bits);
}
/*
* PSSR Decode/Verify Operation
*/
bool PSSR::verify(const secure_vector<uint8_t>& coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
return pss_verify(*m_hash, coded, raw, key_bits);
}
PSSR_Raw::PSSR_Raw(HashFunction* h) :
m_hash(h), m_SALT_SIZE(m_hash->output_length())
{
}
PSSR_Raw::PSSR_Raw(HashFunction* h, size_t salt_size) :
m_hash(h), m_SALT_SIZE(salt_size)
{
}
/*
* PSSR_Raw Update Operation
*/
void PSSR_Raw::update(const uint8_t input[], size_t length)
{
m_msg.insert(m_msg.end(), input, input + length);
}
/*
* Return the raw (unencoded) data
*/
secure_vector<uint8_t> PSSR_Raw::raw_data()
{
secure_vector<uint8_t> ret;
std::swap(ret, m_msg);
if(ret.size() != m_hash->output_length())
throw Encoding_Error("PSSR_Raw Bad input length, did not match hash");
return ret;
}
secure_vector<uint8_t> PSSR_Raw::encoding_of(const secure_vector<uint8_t>& msg,
size_t output_bits,
RandomNumberGenerator& rng)
{
secure_vector<uint8_t> salt = rng.random_vec(m_SALT_SIZE);
return pss_encode(*m_hash, msg, salt, output_bits);
}
/*
* PSSR_Raw Decode/Verify Operation
*/
bool PSSR_Raw::verify(const secure_vector<uint8_t>& coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
return pss_verify(*m_hash, coded, raw, key_bits);
}
}
|
