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
|
/*
* Cryptobox Message Routines
* (C) 2009 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/cryptobox.h>
#include <botan/cipher_mode.h>
#include <botan/mac.h>
#include <botan/pbkdf.h>
#include <botan/data_src.h>
#include <botan/pem.h>
#include <botan/loadstor.h>
#include <botan/mem_ops.h>
namespace Botan {
namespace CryptoBox {
namespace {
/*
First 24 bits of SHA-256("Botan Cryptobox"), followed by 8 0 bits
for later use as flags, etc if needed
*/
const uint32_t CRYPTOBOX_VERSION_CODE = 0xEFC22400;
const size_t VERSION_CODE_LEN = 4;
const size_t CIPHER_KEY_LEN = 32;
const size_t CIPHER_IV_LEN = 16;
const size_t MAC_KEY_LEN = 32;
const size_t MAC_OUTPUT_LEN = 20;
const size_t PBKDF_SALT_LEN = 10;
const size_t PBKDF_ITERATIONS = 8 * 1024;
const size_t PBKDF_OUTPUT_LEN = CIPHER_KEY_LEN + MAC_KEY_LEN + CIPHER_IV_LEN;
const size_t CRYPTOBOX_HEADER_LEN = VERSION_CODE_LEN + PBKDF_SALT_LEN + MAC_OUTPUT_LEN;
}
std::string encrypt(const uint8_t input[], size_t input_len,
const std::string& passphrase,
RandomNumberGenerator& rng)
{
/*
Output format is:
version # (4 bytes)
salt (10 bytes)
mac (20 bytes)
ciphertext
*/
secure_vector<uint8_t> out_buf(CRYPTOBOX_HEADER_LEN + input_len);
for(size_t i = 0; i != VERSION_CODE_LEN; ++i)
out_buf[i] = get_byte(i, CRYPTOBOX_VERSION_CODE);
rng.randomize(&out_buf[VERSION_CODE_LEN], PBKDF_SALT_LEN);
// space left for MAC here
if(input_len > 0)
copy_mem(&out_buf[CRYPTOBOX_HEADER_LEN], input, input_len);
// Generate the keys and IV
std::unique_ptr<PBKDF> pbkdf(PBKDF::create_or_throw("PBKDF2(HMAC(SHA-512))"));
OctetString master_key = pbkdf->derive_key(
CIPHER_KEY_LEN + MAC_KEY_LEN + CIPHER_IV_LEN,
passphrase,
&out_buf[VERSION_CODE_LEN],
PBKDF_SALT_LEN,
PBKDF_ITERATIONS);
const uint8_t* mk = master_key.begin();
const uint8_t* cipher_key = mk;
const uint8_t* mac_key = mk + CIPHER_KEY_LEN;
const uint8_t* iv = mk + CIPHER_KEY_LEN + MAC_KEY_LEN;
// Now encrypt and authenticate
std::unique_ptr<Cipher_Mode> ctr(get_cipher_mode("Serpent/CTR-BE", ENCRYPTION));
ctr->set_key(cipher_key, CIPHER_KEY_LEN);
ctr->start(iv, CIPHER_IV_LEN);
ctr->finish(out_buf, CRYPTOBOX_HEADER_LEN);
std::unique_ptr<MessageAuthenticationCode> hmac =
MessageAuthenticationCode::create_or_throw("HMAC(SHA-512)");
hmac->set_key(mac_key, MAC_KEY_LEN);
if(input_len > 0)
hmac->update(&out_buf[CRYPTOBOX_HEADER_LEN], input_len);
// Can't write directly because of MAC truncation
secure_vector<uint8_t> mac = hmac->final();
copy_mem(&out_buf[VERSION_CODE_LEN + PBKDF_SALT_LEN], mac.data(), MAC_OUTPUT_LEN);
return PEM_Code::encode(out_buf, "BOTAN CRYPTOBOX MESSAGE");
}
secure_vector<uint8_t>
decrypt_bin(const uint8_t input[], size_t input_len,
const std::string& passphrase)
{
DataSource_Memory input_src(input, input_len);
secure_vector<uint8_t> ciphertext =
PEM_Code::decode_check_label(input_src,
"BOTAN CRYPTOBOX MESSAGE");
if(ciphertext.size() < CRYPTOBOX_HEADER_LEN)
throw Decoding_Error("Invalid CryptoBox input");
for(size_t i = 0; i != VERSION_CODE_LEN; ++i)
if(ciphertext[i] != get_byte(i, CRYPTOBOX_VERSION_CODE))
throw Decoding_Error("Bad CryptoBox version");
const uint8_t* pbkdf_salt = &ciphertext[VERSION_CODE_LEN];
const uint8_t* box_mac = &ciphertext[VERSION_CODE_LEN + PBKDF_SALT_LEN];
std::unique_ptr<PBKDF> pbkdf(PBKDF::create_or_throw("PBKDF2(HMAC(SHA-512))"));
OctetString master_key = pbkdf->derive_key(
PBKDF_OUTPUT_LEN,
passphrase,
pbkdf_salt,
PBKDF_SALT_LEN,
PBKDF_ITERATIONS);
const uint8_t* mk = master_key.begin();
const uint8_t* cipher_key = mk;
const uint8_t* mac_key = mk + CIPHER_KEY_LEN;
const uint8_t* iv = mk + CIPHER_KEY_LEN + MAC_KEY_LEN;
// Now authenticate and decrypt
std::unique_ptr<MessageAuthenticationCode> hmac =
MessageAuthenticationCode::create_or_throw("HMAC(SHA-512)");
hmac->set_key(mac_key, MAC_KEY_LEN);
if(ciphertext.size() > CRYPTOBOX_HEADER_LEN)
{
hmac->update(&ciphertext[CRYPTOBOX_HEADER_LEN],
ciphertext.size() - CRYPTOBOX_HEADER_LEN);
}
secure_vector<uint8_t> computed_mac = hmac->final();
if(!constant_time_compare(computed_mac.data(), box_mac, MAC_OUTPUT_LEN))
throw Decoding_Error("CryptoBox integrity failure");
std::unique_ptr<Cipher_Mode> ctr(get_cipher_mode("Serpent/CTR-BE", DECRYPTION));
ctr->set_key(cipher_key, CIPHER_KEY_LEN);
ctr->start(iv, CIPHER_IV_LEN);
ctr->finish(ciphertext, CRYPTOBOX_HEADER_LEN);
ciphertext.erase(ciphertext.begin(), ciphertext.begin() + CRYPTOBOX_HEADER_LEN);
return ciphertext;
}
secure_vector<uint8_t> decrypt_bin(const std::string& input,
const std::string& passphrase)
{
return decrypt_bin(reinterpret_cast<const uint8_t*>(input.data()),
input.size(),
passphrase);
}
std::string decrypt(const uint8_t input[], size_t input_len,
const std::string& passphrase)
{
const secure_vector<uint8_t> bin = decrypt_bin(input, input_len, passphrase);
return std::string(reinterpret_cast<const char*>(&bin[0]),
bin.size());
}
std::string decrypt(const std::string& input,
const std::string& passphrase)
{
return decrypt(reinterpret_cast<const uint8_t*>(input.data()),
input.size(), passphrase);
}
}
}
|
