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
|
/*
* Counter mode
* (C) 1999-2011,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ctr.h>
#include <botan/loadstor.h>
namespace Botan {
CTR_BE::CTR_BE(BlockCipher* ciph) :
m_cipher(ciph),
m_block_size(m_cipher->block_size()),
m_ctr_size(m_block_size),
m_ctr_blocks(m_cipher->parallel_bytes() / m_block_size),
m_counter(m_cipher->parallel_bytes()),
m_pad(m_counter.size()),
m_pad_pos(0)
{
}
CTR_BE::CTR_BE(BlockCipher* cipher, size_t ctr_size) :
m_cipher(cipher),
m_block_size(m_cipher->block_size()),
m_ctr_size(ctr_size),
m_ctr_blocks(m_cipher->parallel_bytes() / m_block_size),
m_counter(m_cipher->parallel_bytes()),
m_pad(m_counter.size()),
m_pad_pos(0)
{
if(m_ctr_size < 4 || m_ctr_size > m_block_size)
throw Invalid_Argument("Invalid CTR-BE counter size");
}
void CTR_BE::clear()
{
m_cipher->clear();
zeroise(m_pad);
zeroise(m_counter);
zap(m_iv);
m_pad_pos = 0;
}
void CTR_BE::key_schedule(const uint8_t key[], size_t key_len)
{
m_cipher->set_key(key, key_len);
// Set a default all-zeros IV
set_iv(nullptr, 0);
}
std::string CTR_BE::name() const
{
if(m_ctr_size == m_block_size)
return ("CTR-BE(" + m_cipher->name() + ")");
else
return ("CTR-BE(" + m_cipher->name() + "," + std::to_string(m_ctr_size) + ")");
}
void CTR_BE::cipher(const uint8_t in[], uint8_t out[], size_t length)
{
verify_key_set(m_iv.empty() == false);
const uint8_t* pad_bits = &m_pad[0];
const size_t pad_size = m_pad.size();
if(m_pad_pos > 0)
{
const size_t avail = pad_size - m_pad_pos;
const size_t take = std::min(length, avail);
xor_buf(out, in, pad_bits + m_pad_pos, take);
length -= take;
in += take;
out += take;
m_pad_pos += take;
if(take == avail)
{
add_counter(m_ctr_blocks);
m_cipher->encrypt_n(m_counter.data(), m_pad.data(), m_ctr_blocks);
m_pad_pos = 0;
}
}
while(length >= pad_size)
{
xor_buf(out, in, pad_bits, pad_size);
length -= pad_size;
in += pad_size;
out += pad_size;
add_counter(m_ctr_blocks);
m_cipher->encrypt_n(m_counter.data(), m_pad.data(), m_ctr_blocks);
}
xor_buf(out, in, pad_bits, length);
m_pad_pos += length;
}
void CTR_BE::set_iv(const uint8_t iv[], size_t iv_len)
{
if(!valid_iv_length(iv_len))
throw Invalid_IV_Length(name(), iv_len);
m_iv.resize(m_cipher->block_size());
zeroise(m_iv);
buffer_insert(m_iv, 0, iv, iv_len);
seek(0);
}
void CTR_BE::add_counter(const uint64_t counter)
{
const size_t ctr_size = m_ctr_size;
const size_t ctr_blocks = m_ctr_blocks;
const size_t BS = m_block_size;
if(ctr_size == 4)
{
size_t off = (BS - 4);
for(size_t i = 0; i != ctr_blocks; ++i)
{
uint32_t low32 = load_be<uint32_t>(&m_counter[off], 0);
low32 += counter;
store_be(low32, &m_counter[off]);
off += BS;
}
}
else if(ctr_size == 8)
{
size_t off = (BS - 8);
for(size_t i = 0; i != ctr_blocks; ++i)
{
uint64_t low64 = load_be<uint64_t>(&m_counter[off], 0);
low64 += counter;
store_be(low64, &m_counter[off]);
off += BS;
}
}
else if(ctr_size == 16)
{
size_t off = (BS - 16);
for(size_t i = 0; i != ctr_blocks; ++i)
{
uint64_t b0 = load_be<uint64_t>(&m_counter[off], 0);
uint64_t b1 = load_be<uint64_t>(&m_counter[off], 1);
b1 += counter;
b0 += (b1 < counter) ? 1 : 0; // carry
store_be(b0, &m_counter[off]);
store_be(b1, &m_counter[off+8]);
off += BS;
}
}
else
{
for(size_t i = 0; i != ctr_blocks; ++i)
{
uint64_t local_counter = counter;
uint16_t carry = static_cast<uint8_t>(local_counter);
for(size_t j = 0; (carry || local_counter) && j != ctr_size; ++j)
{
const size_t off = i*BS + (BS-1-j);
const uint16_t cnt = static_cast<uint16_t>(m_counter[off]) + carry;
m_counter[off] = static_cast<uint8_t>(cnt);
local_counter = (local_counter >> 8);
carry = (cnt >> 8) + static_cast<uint8_t>(local_counter);
}
}
}
}
void CTR_BE::seek(uint64_t offset)
{
verify_key_set(m_iv.empty() == false);
const uint64_t base_counter = m_ctr_blocks * (offset / m_counter.size());
zeroise(m_counter);
buffer_insert(m_counter, 0, m_iv);
const size_t BS = m_block_size;
// Set m_counter blocks to IV, IV + 1, ... IV + n
for(size_t i = 1; i != m_ctr_blocks; ++i)
{
buffer_insert(m_counter, i*BS, &m_counter[(i-1)*BS], BS);
for(size_t j = 0; j != m_ctr_size; ++j)
if(++m_counter[i*BS + (BS - 1 - j)])
break;
}
if(base_counter > 0)
add_counter(base_counter);
m_cipher->encrypt_n(m_counter.data(), m_pad.data(), m_ctr_blocks);
m_pad_pos = offset % m_counter.size();
}
}
|
