Botan: src/constructs/cryptobox/cryptobox.cpp Source File

Botan 1.10.17

cryptobox.cpp
Go to the documentation of this file.
1 /*
2 * Cryptobox Message Routines
3 * (C) 2009 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7
8 #include <botan/cryptobox.h>
9 #include <botan/filters.h>
10 #include <botan/pipe.h>
11 #include <botan/lookup.h>
12 #include <botan/sha2_64.h>
13 #include <botan/hmac.h>
14 #include <botan/pbkdf2.h>
15 #include <botan/pem.h>
16 #include <botan/get_byte.h>
17 #include <botan/mem_ops.h>
18
19 namespace Botan {
20
21 namespace CryptoBox {
22
23 namespace {
24
25 /*
26 First 24 bits of SHA-256("Botan Cryptobox"), followed by 8 0 bits
27 for later use as flags, etc if needed
28 */
29 const u32bit CRYPTOBOX_VERSION_CODE = 0xEFC22400;
30
31 const size_t VERSION_CODE_LEN = 4;
32 const size_t CIPHER_KEY_LEN = 32;
33 const size_t CIPHER_IV_LEN = 16;
34 const size_t MAC_KEY_LEN = 32;
35 const size_t MAC_OUTPUT_LEN = 20;
36 const size_t PBKDF_SALT_LEN = 10;
37 const size_t PBKDF_ITERATIONS = 8 * 1024;
38
39 const size_t PBKDF_OUTPUT_LEN = CIPHER_KEY_LEN + CIPHER_IV_LEN + MAC_KEY_LEN;
40
41 }
42
43 std::string encrypt(const byte input[], size_t input_len,
44 const std::string& passphrase,
45 RandomNumberGenerator& rng)
46 {
47 SecureVector<byte> pbkdf_salt(PBKDF_SALT_LEN);
48 rng.randomize(&pbkdf_salt[0], pbkdf_salt.size());
49
50 PKCS5_PBKDF2 pbkdf(new HMAC(new SHA_512));
51
52 OctetString master_key = pbkdf.derive_key(
53 PBKDF_OUTPUT_LEN,
54 passphrase,
55 &pbkdf_salt[0],
56 pbkdf_salt.size(),
57 PBKDF_ITERATIONS);
58
59 const byte* mk = master_key.begin();
60
61 SymmetricKey cipher_key(&mk[0], CIPHER_KEY_LEN);
62 SymmetricKey mac_key(&mk[CIPHER_KEY_LEN], MAC_KEY_LEN);
63 InitializationVector iv(&mk[CIPHER_KEY_LEN + MAC_KEY_LEN], CIPHER_IV_LEN);
64
65 Pipe pipe(get_cipher("Serpent/CTR-BE", cipher_key, iv, ENCRYPTION),
66 new Fork(
67 0,
68 new MAC_Filter(new HMAC(new SHA_512),
69 mac_key, MAC_OUTPUT_LEN)));
70
71 pipe.process_msg(input, input_len);
72
73 /*
74 Output format is:
75 version # (4 bytes)
76 salt (10 bytes)
77 mac (20 bytes)
78 ciphertext
79 */
80 const size_t ciphertext_len = pipe.remaining(0);
81
82 SecureVector<byte> out_buf(VERSION_CODE_LEN +
83 PBKDF_SALT_LEN +
84 MAC_OUTPUT_LEN +
85 ciphertext_len);
86
87 for(size_t i = 0; i != VERSION_CODE_LEN; ++i)
88 out_buf[i] = get_byte(i, CRYPTOBOX_VERSION_CODE);
89
90 copy_mem(&out_buf[VERSION_CODE_LEN], &pbkdf_salt[0], PBKDF_SALT_LEN);
91
92 pipe.read(&out_buf[VERSION_CODE_LEN + PBKDF_SALT_LEN], MAC_OUTPUT_LEN, 1);
93 pipe.read(&out_buf[VERSION_CODE_LEN + PBKDF_SALT_LEN + MAC_OUTPUT_LEN],
94 ciphertext_len, 0);
95
96 return PEM_Code::encode(out_buf, "BOTAN CRYPTOBOX MESSAGE");
97 }
98
99 std::string decrypt(const byte input[], size_t input_len,
100 const std::string& passphrase)
101 {
102 DataSource_Memory input_src(input, input_len);
103 SecureVector<byte> ciphertext =
104 PEM_Code::decode_check_label(input_src,
105 "BOTAN CRYPTOBOX MESSAGE");
106
107 if(ciphertext.size() < (VERSION_CODE_LEN + PBKDF_SALT_LEN + MAC_OUTPUT_LEN))
108 throw Decoding_Error("Invalid CryptoBox input");
109
110 for(size_t i = 0; i != VERSION_CODE_LEN; ++i)
111 if(ciphertext[i] != get_byte(i, CRYPTOBOX_VERSION_CODE))
112 throw Decoding_Error("Bad CryptoBox version");
113
114 const byte* pbkdf_salt = &ciphertext[VERSION_CODE_LEN];
115
116 PKCS5_PBKDF2 pbkdf(new HMAC(new SHA_512));
117
118 OctetString master_key = pbkdf.derive_key(
119 PBKDF_OUTPUT_LEN,
120 passphrase,
121 pbkdf_salt,
122 PBKDF_SALT_LEN,
123 PBKDF_ITERATIONS);
124
125 const byte* mk = master_key.begin();
126
127 SymmetricKey cipher_key(&mk[0], CIPHER_KEY_LEN);
128 SymmetricKey mac_key(&mk[CIPHER_KEY_LEN], MAC_KEY_LEN);
129 InitializationVector iv(&mk[CIPHER_KEY_LEN + MAC_KEY_LEN], CIPHER_IV_LEN);
130
131 Pipe pipe(new Fork(
132 get_cipher("Serpent/CTR-BE", cipher_key, iv, DECRYPTION),
133 new MAC_Filter(new HMAC(new SHA_512),
134 mac_key, MAC_OUTPUT_LEN)));
135
136 const size_t ciphertext_offset =
137 VERSION_CODE_LEN + PBKDF_SALT_LEN + MAC_OUTPUT_LEN;
138
139 pipe.process_msg(&ciphertext[ciphertext_offset],
140 ciphertext.size() - ciphertext_offset);
141
142 byte computed_mac[MAC_OUTPUT_LEN];
143 pipe.read(computed_mac, MAC_OUTPUT_LEN, 1);
144
145 if(!same_mem(computed_mac,
146 &ciphertext[VERSION_CODE_LEN + PBKDF_SALT_LEN],
147 MAC_OUTPUT_LEN))
148 throw Decoding_Error("CryptoBox integrity failure");
149
150 return pipe.read_all_as_string(0);
151 }
152
153 std::string decrypt(const std::string& input,
154 const std::string& passphrase)
155 {
156 return decrypt(reinterpret_cast<const byte*>(&input[0]),
157 input.size(),
158 passphrase);
159 }
160
161 }
162
163 }
Botan::Pipe::remaining
size_t remaining(message_id msg=DEFAULT_MESSAGE) const
Definition: pipe_rw.cpp:138
Botan::OctetString
Definition: symkey.h:19
Botan::same_mem
bool same_mem(const T *p1, const T *p2, size_t n)
Definition: mem_ops.h:57
Botan::Pipe::read
size_t read(byte output[], size_t length)
Definition: pipe_rw.cpp:89
Botan::PKCS5_PBKDF2
Definition: pbkdf2.h:19
Botan::RandomNumberGenerator
Definition: rng.h:20
Botan::Pipe::read_all_as_string
std::string read_all_as_string(message_id=DEFAULT_MESSAGE)
Definition: pipe_rw.cpp:117
Botan::ENCRYPTION
Definition: sym_algo.h:87
Botan::get_byte
byte get_byte(size_t byte_num, T input)
Definition: get_byte.h:21
Botan::CryptoBox::decrypt
std::string decrypt(const byte input[], size_t input_len, const std::string &passphrase)
Definition: cryptobox.cpp:99
Botan::DECRYPTION
Definition: sym_algo.h:87
Botan::OctetString::begin
const byte * begin() const
Definition: symkey.h:35
Botan::byte
unsigned char byte
Definition: types.h:22
Botan::Decoding_Error
Definition: exceptn.h:138
Botan::copy_mem
void copy_mem(T *out, const T *in, size_t n)
Definition: mem_ops.h:22
Botan
Definition: algo_base.h:14
Botan::MAC_Filter
Definition: filters.h:142
Botan::CryptoBox::encrypt
std::string encrypt(const byte input[], size_t input_len, const std::string &passphrase, RandomNumberGenerator &rng)
Definition: cryptobox.cpp:43
Botan::MemoryRegion::size
size_t size() const
Definition: secmem.h:29
Botan::PEM_Code::encode
std::string encode(const byte der[], size_t length, const std::string &label, size_t width)
Definition: pem.cpp:19
Botan::DataSource_Memory
Definition: data_src.h:94
Botan::Fork
Definition: basefilt.h:57
Botan::SecureVector< byte >
Botan::HMAC
Definition: hmac.h:19
Botan::Pipe
Definition: pipe.h:25
Botan::PKCS5_PBKDF2::derive_key
OctetString derive_key(size_t output_len, const std::string &passphrase, const byte salt[], size_t salt_len, size_t iterations) const
Definition: pbkdf2.cpp:17
Botan::get_cipher
Keyed_Filter * get_cipher(const std::string &algo_spec, Cipher_Dir direction)
Definition: lookup.cpp:124
Botan::PEM_Code::decode_check_label
SecureVector< byte > decode_check_label(DataSource &source, const std::string &label_want)
Definition: pem.cpp:42
Botan::Pipe::process_msg
void process_msg(const byte in[], size_t length)
Definition: pipe.cpp:116
Botan::SHA_512
Definition: sha2_64.h:39
Botan::u32bit
unsigned int u32bit
Definition: types.h:32