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
|
/*
* ChaCha20Poly1305 AEAD
* (C) 2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/mode_utils.h>
#include <botan/chacha20poly1305.h>
namespace Botan {
BOTAN_REGISTER_TRANSFORM_NOARGS(ChaCha20Poly1305_Encryption);
BOTAN_REGISTER_TRANSFORM_NOARGS(ChaCha20Poly1305_Decryption);
ChaCha20Poly1305_Mode::ChaCha20Poly1305_Mode() :
m_chacha(make_stream_cipher("ChaCha")),
m_poly1305(make_message_auth("Poly1305"))
{}
bool ChaCha20Poly1305_Mode::valid_nonce_length(size_t n) const
{
return (n == 8 || n == 12);
}
void ChaCha20Poly1305_Mode::clear()
{
m_chacha->clear();
m_poly1305->clear();
m_ad.clear();
m_ctext_len = 0;
}
void ChaCha20Poly1305_Mode::key_schedule(const byte key[], size_t length)
{
m_chacha->set_key(key, length);
}
void ChaCha20Poly1305_Mode::set_associated_data(const byte ad[], size_t length)
{
if(m_ctext_len)
throw std::runtime_error("Too late to set AD for ChaCha20Poly1305");
m_ad.assign(ad, ad + length);
}
void ChaCha20Poly1305_Mode::update_len(size_t len)
{
byte len8[8] = { 0 };
store_le(static_cast<u64bit>(len), len8);
m_poly1305->update(len8, 8);
}
secure_vector<byte> ChaCha20Poly1305_Mode::start_raw(const byte nonce[], size_t nonce_len)
{
if(!valid_nonce_length(nonce_len))
throw Invalid_IV_Length(name(), nonce_len);
m_ctext_len = 0;
m_nonce_len = nonce_len;
m_chacha->set_iv(nonce, nonce_len);
secure_vector<byte> zeros(64);
m_chacha->encrypt(zeros);
m_poly1305->set_key(&zeros[0], 32);
// Remainder of output is discard
m_poly1305->update(m_ad);
if(cfrg_version())
{
std::vector<byte> padding(16 - m_ad.size() % 16);
m_poly1305->update(padding);
}
else
{
update_len(m_ad.size());
}
return secure_vector<byte>();
}
void ChaCha20Poly1305_Encryption::update(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
byte* buf = &buffer[offset];
m_chacha->cipher1(buf, sz);
m_poly1305->update(buf, sz); // poly1305 of ciphertext
m_ctext_len += sz;
}
void ChaCha20Poly1305_Encryption::finish(secure_vector<byte>& buffer, size_t offset)
{
update(buffer, offset);
if(cfrg_version())
{
std::vector<byte> padding(16 - m_ctext_len % 16);
m_poly1305->update(padding);
update_len(m_ad.size());
}
update_len(m_ctext_len);
const secure_vector<byte> mac = m_poly1305->final();
buffer += std::make_pair(&mac[0], tag_size());
m_ctext_len = 0;
}
void ChaCha20Poly1305_Decryption::update(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
byte* buf = &buffer[offset];
m_poly1305->update(buf, sz); // poly1305 of ciphertext
m_chacha->cipher1(buf, sz);
m_ctext_len += sz;
}
void ChaCha20Poly1305_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
byte* buf = &buffer[offset];
BOTAN_ASSERT(sz >= tag_size(), "Have the tag as part of final input");
const size_t remaining = sz - tag_size();
if(remaining)
{
m_poly1305->update(buf, remaining); // poly1305 of ciphertext
m_chacha->cipher1(buf, remaining);
m_ctext_len += remaining;
}
if(cfrg_version())
{
for(size_t i = 0; i != 16 - m_ctext_len % 16; ++i)
m_poly1305->update(0);
update_len(m_ad.size());
}
update_len(m_ctext_len);
const secure_vector<byte> mac = m_poly1305->final();
const byte* included_tag = &buf[remaining];
m_ctext_len = 0;
if(!same_mem(&mac[0], included_tag, tag_size()))
throw Integrity_Failure("ChaCha20Poly1305 tag check failed");
buffer.resize(offset + remaining);
}
}
|
