Botan  1.11.32
tls_session_key.cpp
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1 /*
2 * TLS Session Key
3 * (C) 2004-2006,2011,2016 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/internal/tls_session_key.h>
9 #include <botan/internal/tls_handshake_state.h>
10 #include <botan/internal/tls_messages.h>
11 
12 namespace Botan {
13 
14 namespace TLS {
15 
16 /**
17 * Session_Keys Constructor
18 */
19 Session_Keys::Session_Keys(const Handshake_State* state,
20  const secure_vector<byte>& pre_master_secret,
21  bool resuming)
22  {
23  const size_t cipher_keylen = state->ciphersuite().cipher_keylen();
24  const size_t mac_keylen = state->ciphersuite().mac_keylen();
25  const size_t cipher_nonce_bytes = state->ciphersuite().nonce_bytes_from_handshake();
26 
27  const bool extended_master_secret = state->server_hello()->supports_extended_master_secret();
28 
29  const size_t prf_gen = 2 * (mac_keylen + cipher_keylen + cipher_nonce_bytes);
30 
31  const byte MASTER_SECRET_MAGIC[] = {
32  0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
33 
34  const byte EXT_MASTER_SECRET_MAGIC[] = {
35  0x65, 0x78, 0x74, 0x65, 0x6E, 0x64, 0x65, 0x64, 0x20,
36  0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
37 
38  const byte KEY_GEN_MAGIC[] = {
39  0x6B, 0x65, 0x79, 0x20, 0x65, 0x78, 0x70, 0x61, 0x6E, 0x73, 0x69, 0x6F, 0x6E };
40 
41  std::unique_ptr<KDF> prf(state->protocol_specific_prf());
42 
43  if(resuming)
44  {
45  // This is actually the master secret saved as part of the session
46  m_master_sec = pre_master_secret;
47  }
48  else
49  {
50  secure_vector<byte> salt;
51  secure_vector<byte> label;
52  if(extended_master_secret)
53  {
54  label += std::make_pair(EXT_MASTER_SECRET_MAGIC, sizeof(EXT_MASTER_SECRET_MAGIC));
55  salt += state->hash().final(state->version(),
56  state->ciphersuite().prf_algo());
57  }
58  else
59  {
60  label += std::make_pair(MASTER_SECRET_MAGIC, sizeof(MASTER_SECRET_MAGIC));
61  salt += state->client_hello()->random();
62  salt += state->server_hello()->random();
63  }
64 
65  m_master_sec = prf->derive_key(48, pre_master_secret, salt, label);
66  }
67 
68  secure_vector<byte> salt;
69  secure_vector<byte> label;
70  label += std::make_pair(KEY_GEN_MAGIC, sizeof(KEY_GEN_MAGIC));
71  salt += state->server_hello()->random();
72  salt += state->client_hello()->random();
73 
74  SymmetricKey keyblock = prf->derive_key(prf_gen, m_master_sec, salt, label);
75 
76  const byte* key_data = keyblock.begin();
77 
78  m_c_mac = SymmetricKey(key_data, mac_keylen);
79  key_data += mac_keylen;
80 
81  m_s_mac = SymmetricKey(key_data, mac_keylen);
82  key_data += mac_keylen;
83 
84  m_c_cipher = SymmetricKey(key_data, cipher_keylen);
85  key_data += cipher_keylen;
86 
87  m_s_cipher = SymmetricKey(key_data, cipher_keylen);
88  key_data += cipher_keylen;
89 
90  m_c_iv = InitializationVector(key_data, cipher_nonce_bytes);
91  key_data += cipher_nonce_bytes;
92 
93  m_s_iv = InitializationVector(key_data, cipher_nonce_bytes);
94  }
95 
96 }
97 
98 }
OctetString InitializationVector
Definition: symkey.h:141
Definition: alg_id.cpp:13
OctetString SymmetricKey
Definition: symkey.h:136
std::uint8_t byte
Definition: types.h:31