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
|
/*
* SIV Mode Encryption
* (C) 2013,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/siv.h>
#include <botan/block_cipher.h>
#include <botan/cmac.h>
#include <botan/internal/poly_dbl.h>
#include <botan/ctr.h>
namespace Botan {
SIV_Mode::SIV_Mode(BlockCipher* cipher) :
m_name(cipher->name() + "/SIV"),
m_ctr(new CTR_BE(cipher->clone())),
m_mac(new CMAC(cipher)),
m_bs(cipher->block_size())
{
// Not really true but only 128 bit allowed at the moment
if(m_bs != 16)
throw Invalid_Argument("SIV requires a 128 bit block cipher");
}
SIV_Mode::~SIV_Mode()
{
// for ~unique_ptr
}
void SIV_Mode::clear()
{
m_ctr->clear();
m_mac->clear();
reset();
}
void SIV_Mode::reset()
{
m_nonce.clear();
m_msg_buf.clear();
m_ad_macs.clear();
}
std::string SIV_Mode::name() const
{
return m_name;
}
bool SIV_Mode::valid_nonce_length(size_t) const
{
return true;
}
size_t SIV_Mode::update_granularity() const
{
/*
This value does not particularly matter as regardless SIV_Mode::update
buffers all input, so in theory this could be 1. However as for instance
Transform_Filter creates update_granularity() uint8_t buffers, use a
somewhat large size to avoid bouncing on a tiny buffer.
*/
return 128;
}
Key_Length_Specification SIV_Mode::key_spec() const
{
return m_mac->key_spec().multiple(2);
}
void SIV_Mode::key_schedule(const uint8_t key[], size_t length)
{
const size_t keylen = length / 2;
m_mac->set_key(key, keylen);
m_ctr->set_key(key + keylen, keylen);
m_ad_macs.clear();
}
void SIV_Mode::set_associated_data_n(size_t n, const uint8_t ad[], size_t length)
{
const size_t max_ads = block_size() * 8 - 2;
if(n > max_ads)
throw Invalid_Argument(name() + " allows no more than " + std::to_string(max_ads) + " ADs");
if(n >= m_ad_macs.size())
m_ad_macs.resize(n+1);
m_ad_macs[n] = m_mac->process(ad, length);
}
void SIV_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
{
if(!valid_nonce_length(nonce_len))
throw Invalid_IV_Length(name(), nonce_len);
if(nonce_len)
m_nonce = m_mac->process(nonce, nonce_len);
else
m_nonce.clear();
m_msg_buf.clear();
}
size_t SIV_Mode::process(uint8_t buf[], size_t sz)
{
// all output is saved for processing in finish
m_msg_buf.insert(m_msg_buf.end(), buf, buf + sz);
return 0;
}
secure_vector<uint8_t> SIV_Mode::S2V(const uint8_t* text, size_t text_len)
{
const std::vector<uint8_t> zeros(block_size());
secure_vector<uint8_t> V = m_mac->process(zeros.data(), zeros.size());
for(size_t i = 0; i != m_ad_macs.size(); ++i)
{
poly_double_n(V.data(), V.size());
V ^= m_ad_macs[i];
}
if(m_nonce.size())
{
poly_double_n(V.data(), V.size());
V ^= m_nonce;
}
if(text_len < block_size())
{
poly_double_n(V.data(), V.size());
xor_buf(V.data(), text, text_len);
V[text_len] ^= 0x80;
return m_mac->process(V);
}
m_mac->update(text, text_len - block_size());
xor_buf(V.data(), &text[text_len - block_size()], block_size());
m_mac->update(V);
return m_mac->final();
}
void SIV_Mode::set_ctr_iv(secure_vector<uint8_t> V)
{
V[m_bs-8] &= 0x7F;
V[m_bs-4] &= 0x7F;
ctr().set_iv(V.data(), V.size());
}
void SIV_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
msg_buf().clear();
const secure_vector<uint8_t> V = S2V(buffer.data() + offset, buffer.size() - offset);
buffer.insert(buffer.begin() + offset, V.begin(), V.end());
if(buffer.size() != offset + V.size())
{
set_ctr_iv(V);
ctr().cipher1(&buffer[offset + V.size()], buffer.size() - offset - V.size());
}
}
void SIV_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
msg_buf().clear();
const size_t sz = buffer.size() - offset;
BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
secure_vector<uint8_t> V(buffer.data() + offset,
buffer.data() + offset + block_size());
if(buffer.size() != offset + V.size())
{
set_ctr_iv(V);
ctr().cipher(buffer.data() + offset + V.size(),
buffer.data() + offset,
buffer.size() - offset - V.size());
}
const secure_vector<uint8_t> T = S2V(buffer.data() + offset, buffer.size() - offset - V.size());
if(!constant_time_compare(T.data(), V.data(), T.size()))
throw Integrity_Failure("SIV tag check failed");
buffer.resize(buffer.size() - tag_size());
}
}
|
