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/*
* TLS Session Key
* (C) 2004-2006,2011,2016 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/tls_session_key.h>
#include <botan/internal/tls_handshake_state.h>
#include <botan/internal/tls_messages.h>
namespace Botan {
namespace TLS {
/**
* Session_Keys Constructor
*/
Session_Keys::Session_Keys(const Handshake_State* state,
const secure_vector<byte>& pre_master_secret,
bool resuming)
{
const size_t cipher_keylen = state->ciphersuite().cipher_keylen();
const size_t mac_keylen = state->ciphersuite().mac_keylen();
const size_t cipher_nonce_bytes = state->ciphersuite().nonce_bytes_from_handshake();
const bool extended_master_secret = state->server_hello()->supports_extended_master_secret();
const size_t prf_gen = 2 * (mac_keylen + cipher_keylen + cipher_nonce_bytes);
const byte MASTER_SECRET_MAGIC[] = {
0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
const byte EXT_MASTER_SECRET_MAGIC[] = {
0x65, 0x78, 0x74, 0x65, 0x6E, 0x64, 0x65, 0x64, 0x20,
0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
const byte KEY_GEN_MAGIC[] = {
0x6B, 0x65, 0x79, 0x20, 0x65, 0x78, 0x70, 0x61, 0x6E, 0x73, 0x69, 0x6F, 0x6E };
std::unique_ptr<KDF> prf(state->protocol_specific_prf());
if(resuming)
{
// This is actually the master secret saved as part of the session
m_master_sec = pre_master_secret;
}
else
{
secure_vector<byte> salt;
if(extended_master_secret)
{
salt += std::make_pair(EXT_MASTER_SECRET_MAGIC, sizeof(EXT_MASTER_SECRET_MAGIC));
salt += state->hash().final(state->version(),
state->ciphersuite().prf_algo());
}
else
{
salt += std::make_pair(MASTER_SECRET_MAGIC, sizeof(MASTER_SECRET_MAGIC));
salt += state->client_hello()->random();
salt += state->server_hello()->random();
}
m_master_sec = prf->derive_key(48, pre_master_secret, salt);
}
secure_vector<byte> salt;
salt += std::make_pair(KEY_GEN_MAGIC, sizeof(KEY_GEN_MAGIC));
salt += state->server_hello()->random();
salt += state->client_hello()->random();
SymmetricKey keyblock = prf->derive_key(prf_gen, m_master_sec, salt);
const byte* key_data = keyblock.begin();
m_c_mac = SymmetricKey(key_data, mac_keylen);
key_data += mac_keylen;
m_s_mac = SymmetricKey(key_data, mac_keylen);
key_data += mac_keylen;
m_c_cipher = SymmetricKey(key_data, cipher_keylen);
key_data += cipher_keylen;
m_s_cipher = SymmetricKey(key_data, cipher_keylen);
key_data += cipher_keylen;
m_c_iv = InitializationVector(key_data, cipher_nonce_bytes);
key_data += cipher_nonce_bytes;
m_s_iv = InitializationVector(key_data, cipher_nonce_bytes);
}
}
}
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