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
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
|
/*
* TLS Session State
* (C) 2011-2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/tls_session.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/asn1_str.h>
#include <botan/pem.h>
#include <botan/lookup.h>
#include <botan/loadstor.h>
#include <memory>
namespace Botan {
namespace TLS {
Session::Session(const std::vector<byte>& session_identifier,
const secure_vector<byte>& master_secret,
Protocol_Version version,
u16bit ciphersuite,
byte compression_method,
Connection_Side side,
bool secure_renegotiation_supported,
size_t fragment_size,
const std::vector<X509_Certificate>& certs,
const std::vector<byte>& ticket,
const std::string& sni_hostname,
const std::string& srp_identifier) :
m_start_time(std::chrono::system_clock::now()),
m_identifier(session_identifier),
m_session_ticket(ticket),
m_master_secret(master_secret),
m_version(version),
m_ciphersuite(ciphersuite),
m_compression_method(compression_method),
m_connection_side(side),
m_secure_renegotiation_supported(secure_renegotiation_supported),
m_fragment_size(fragment_size),
m_peer_certs(certs),
m_sni_hostname(sni_hostname),
m_srp_identifier(srp_identifier)
{
}
Session::Session(const std::string& pem)
{
secure_vector<byte> der = PEM_Code::decode_check_label(pem, "SSL SESSION");
*this = Session(&der[0], der.size());
}
Session::Session(const byte ber[], size_t ber_len)
{
byte side_code = 0;
ASN1_String sni_hostname_str;
ASN1_String srp_identifier_str;
byte major_version = 0, minor_version = 0;
std::vector<byte> peer_cert_bits;
size_t start_time = 0;
BER_Decoder(ber, ber_len)
.start_cons(SEQUENCE)
.decode_and_check(static_cast<size_t>(TLS_SESSION_PARAM_STRUCT_VERSION),
"Unknown version in session structure")
.decode_integer_type(start_time)
.decode_integer_type(major_version)
.decode_integer_type(minor_version)
.decode(m_identifier, OCTET_STRING)
.decode(m_session_ticket, OCTET_STRING)
.decode_integer_type(m_ciphersuite)
.decode_integer_type(m_compression_method)
.decode_integer_type(side_code)
.decode_integer_type(m_fragment_size)
.decode(m_secure_renegotiation_supported)
.decode(m_master_secret, OCTET_STRING)
.decode(peer_cert_bits, OCTET_STRING)
.decode(sni_hostname_str)
.decode(srp_identifier_str)
.end_cons()
.verify_end();
m_version = Protocol_Version(major_version, minor_version);
m_start_time = std::chrono::system_clock::from_time_t(start_time);
m_sni_hostname = sni_hostname_str.value();
m_srp_identifier = srp_identifier_str.value();
m_connection_side = static_cast<Connection_Side>(side_code);
if(!peer_cert_bits.empty())
{
DataSource_Memory certs(&peer_cert_bits[0], peer_cert_bits.size());
while(!certs.end_of_data())
m_peer_certs.push_back(X509_Certificate(certs));
}
}
secure_vector<byte> Session::DER_encode() const
{
std::vector<byte> peer_cert_bits;
for(size_t i = 0; i != m_peer_certs.size(); ++i)
peer_cert_bits += m_peer_certs[i].BER_encode();
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(static_cast<size_t>(TLS_SESSION_PARAM_STRUCT_VERSION))
.encode(static_cast<size_t>(std::chrono::system_clock::to_time_t(m_start_time)))
.encode(static_cast<size_t>(m_version.major_version()))
.encode(static_cast<size_t>(m_version.minor_version()))
.encode(m_identifier, OCTET_STRING)
.encode(m_session_ticket, OCTET_STRING)
.encode(static_cast<size_t>(m_ciphersuite))
.encode(static_cast<size_t>(m_compression_method))
.encode(static_cast<size_t>(m_connection_side))
.encode(static_cast<size_t>(m_fragment_size))
.encode(m_secure_renegotiation_supported)
.encode(m_master_secret, OCTET_STRING)
.encode(peer_cert_bits, OCTET_STRING)
.encode(ASN1_String(m_sni_hostname, UTF8_STRING))
.encode(ASN1_String(m_srp_identifier, UTF8_STRING))
.end_cons()
.get_contents();
}
std::string Session::PEM_encode() const
{
return PEM_Code::encode(this->DER_encode(), "SSL SESSION");
}
std::chrono::seconds Session::session_age() const
{
return std::chrono::duration_cast<std::chrono::seconds>(
std::chrono::system_clock::now() - m_start_time);
}
namespace {
const u32bit SESSION_CRYPTO_MAGIC = 0x571B0E4F;
const std::string SESSION_CRYPTO_CIPHER = "AES-256/CBC";
const std::string SESSION_CRYPTO_MAC = "HMAC(SHA-256)";
const std::string SESSION_CRYPTO_KDF = "KDF2(SHA-256)";
const size_t MAGIC_LENGTH = 4;
const size_t KEY_KDF_SALT_LENGTH = 10;
const size_t MAC_KEY_LENGTH = 32;
const size_t CIPHER_KEY_LENGTH = 32;
const size_t CIPHER_IV_LENGTH = 16;
const size_t MAC_OUTPUT_LENGTH = 32;
}
std::vector<byte>
Session::encrypt(const SymmetricKey& master_key,
RandomNumberGenerator& rng) const
{
std::unique_ptr<KDF> kdf(get_kdf(SESSION_CRYPTO_KDF));
const secure_vector<byte> cipher_key_salt =
rng.random_vec(KEY_KDF_SALT_LENGTH);
const secure_vector<byte> mac_key_salt =
rng.random_vec(KEY_KDF_SALT_LENGTH);
SymmetricKey cipher_key =
kdf->derive_key(CIPHER_KEY_LENGTH,
master_key.bits_of(),
cipher_key_salt);
SymmetricKey mac_key =
kdf->derive_key(MAC_KEY_LENGTH,
master_key.bits_of(),
mac_key_salt);
InitializationVector cipher_iv(rng, 16);
std::unique_ptr<MessageAuthenticationCode> mac(get_mac(SESSION_CRYPTO_MAC));
mac->set_key(mac_key);
Pipe pipe(get_cipher(SESSION_CRYPTO_CIPHER, cipher_key, cipher_iv, ENCRYPTION));
pipe.process_msg(this->DER_encode());
secure_vector<byte> ctext = pipe.read_all(0);
std::vector<byte> out(MAGIC_LENGTH);
store_be(SESSION_CRYPTO_MAGIC, &out[0]);
out += cipher_key_salt;
out += mac_key_salt;
out += cipher_iv.bits_of();
out += ctext;
mac->update(out);
out += mac->final();
return out;
}
Session Session::decrypt(const byte buf[], size_t buf_len,
const SymmetricKey& master_key)
{
try
{
const size_t MIN_CTEXT_SIZE = 4 * 16; // due to 48 byte master secret
if(buf_len < (MAGIC_LENGTH +
2 * KEY_KDF_SALT_LENGTH +
CIPHER_IV_LENGTH +
MIN_CTEXT_SIZE +
MAC_OUTPUT_LENGTH))
throw Decoding_Error("Encrypted TLS session too short to be valid");
if(load_be<u32bit>(buf, 0) != SESSION_CRYPTO_MAGIC)
throw Decoding_Error("Unknown header value in encrypted session");
std::unique_ptr<KDF> kdf(get_kdf(SESSION_CRYPTO_KDF));
const byte* cipher_key_salt = &buf[MAGIC_LENGTH];
const byte* mac_key_salt = &buf[MAGIC_LENGTH + KEY_KDF_SALT_LENGTH];
SymmetricKey mac_key =
kdf->derive_key(MAC_KEY_LENGTH,
master_key.bits_of(),
mac_key_salt, KEY_KDF_SALT_LENGTH);
std::unique_ptr<MessageAuthenticationCode> mac(get_mac(SESSION_CRYPTO_MAC));
mac->set_key(mac_key);
mac->update(&buf[0], buf_len - MAC_OUTPUT_LENGTH);
secure_vector<byte> computed_mac = mac->final();
if(!same_mem(&buf[buf_len - MAC_OUTPUT_LENGTH], &computed_mac[0], computed_mac.size()))
throw Decoding_Error("MAC verification failed for encrypted session");
SymmetricKey cipher_key =
kdf->derive_key(CIPHER_KEY_LENGTH,
master_key.bits_of(),
cipher_key_salt, KEY_KDF_SALT_LENGTH);
InitializationVector cipher_iv(&buf[MAGIC_LENGTH+2*KEY_KDF_SALT_LENGTH],
CIPHER_IV_LENGTH);
const size_t CTEXT_OFFSET = MAGIC_LENGTH + 2 * KEY_KDF_SALT_LENGTH + CIPHER_IV_LENGTH;
Pipe pipe(get_cipher(SESSION_CRYPTO_CIPHER, cipher_key, cipher_iv, DECRYPTION));
pipe.process_msg(&buf[CTEXT_OFFSET],
buf_len - (MAC_OUTPUT_LENGTH + CTEXT_OFFSET));
secure_vector<byte> ber = pipe.read_all();
return Session(&ber[0], ber.size());
}
catch(std::exception& e)
{
throw Decoding_Error("Failed to decrypt encrypted session -" +
std::string(e.what()));
}
}
}
}
|
