Botan 2.19.2
Crypto and TLS for C&
tls_session_key.cpp
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1/*
2* TLS Session Key
3* (C) 2004-2006,2011,2016,2019 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/tls_messages.h>
11#include <botan/kdf.h>
12
13namespace Botan {
14
15namespace TLS {
16
17/**
18* Session_Keys Constructor
19*/
21 const secure_vector<uint8_t>& pre_master_secret,
22 bool resuming)
23 {
24 const size_t cipher_keylen = state->ciphersuite().cipher_keylen();
25 const size_t mac_keylen = state->ciphersuite().mac_keylen();
26 const size_t cipher_nonce_bytes = state->ciphersuite().nonce_bytes_from_handshake();
27
28 const bool extended_master_secret = state->server_hello()->supports_extended_master_secret();
29
30 const size_t prf_gen = 2 * (mac_keylen + cipher_keylen + cipher_nonce_bytes);
31
32 const uint8_t MASTER_SECRET_MAGIC[] = {
33 0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
34
35 const uint8_t EXT_MASTER_SECRET_MAGIC[] = {
36 0x65, 0x78, 0x74, 0x65, 0x6E, 0x64, 0x65, 0x64, 0x20,
37 0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
38
39 const uint8_t KEY_GEN_MAGIC[] = {
40 0x6B, 0x65, 0x79, 0x20, 0x65, 0x78, 0x70, 0x61, 0x6E, 0x73, 0x69, 0x6F, 0x6E };
41
42 std::unique_ptr<KDF> prf(state->protocol_specific_prf());
43
44 if(resuming)
45 {
46 // This is actually the master secret saved as part of the session
47 m_master_sec = pre_master_secret;
48 }
49 else
50 {
51 std::vector<uint8_t> salt;
52 std::vector<uint8_t> label;
53 if(extended_master_secret)
54 {
55 label.assign(EXT_MASTER_SECRET_MAGIC, EXT_MASTER_SECRET_MAGIC + sizeof(EXT_MASTER_SECRET_MAGIC));
56 salt += state->hash().final(state->version(),
57 state->ciphersuite().prf_algo());
58 }
59 else
60 {
61 label.assign(MASTER_SECRET_MAGIC, MASTER_SECRET_MAGIC + sizeof(MASTER_SECRET_MAGIC));
62 salt += state->client_hello()->random();
63 salt += state->server_hello()->random();
64 }
65
66 m_master_sec = prf->derive_key(48, pre_master_secret, salt, label);
67 }
68
69 std::vector<uint8_t> salt;
70 std::vector<uint8_t> label;
71 label.assign(KEY_GEN_MAGIC, KEY_GEN_MAGIC + sizeof(KEY_GEN_MAGIC));
72 salt += state->server_hello()->random();
73 salt += state->client_hello()->random();
74
75 const secure_vector<uint8_t> prf_output = prf->derive_key(
76 prf_gen,
77 m_master_sec.data(), m_master_sec.size(),
78 salt.data(), salt.size(),
79 label.data(), label.size());
80
81 const uint8_t* key_data = prf_output.data();
82
83 m_c_aead.resize(mac_keylen + cipher_keylen);
84 m_s_aead.resize(mac_keylen + cipher_keylen);
85
86 copy_mem(&m_c_aead[0], key_data, mac_keylen);
87 copy_mem(&m_s_aead[0], key_data + mac_keylen, mac_keylen);
88
89 copy_mem(&m_c_aead[mac_keylen], key_data + 2*mac_keylen, cipher_keylen);
90 copy_mem(&m_s_aead[mac_keylen], key_data + 2*mac_keylen + cipher_keylen, cipher_keylen);
91
92 m_c_nonce.resize(cipher_nonce_bytes);
93 m_s_nonce.resize(cipher_nonce_bytes);
94
95 copy_mem(&m_c_nonce[0], key_data + 2*(mac_keylen + cipher_keylen), cipher_nonce_bytes);
96 copy_mem(&m_s_nonce[0], key_data + 2*(mac_keylen + cipher_keylen) + cipher_nonce_bytes, cipher_nonce_bytes);
97 }
98
99}
100
101}
size_t cipher_keylen() const
size_t nonce_bytes_from_handshake() const
std::string prf_algo() const
secure_vector< uint8_t > final(Protocol_Version version, const std::string &mac_algo) const
void client_hello(Client_Hello *client_hello)
const Ciphersuite & ciphersuite() const
void server_hello(Server_Hello *server_hello)
Protocol_Version version() const
Definition: alg_id.cpp:13
void copy_mem(T *out, const T *in, size_t n)
Definition: mem_ops.h:133
std::vector< T, secure_allocator< T > > secure_vector
Definition: secmem.h:65