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/*
* TLS Session Key
* (C) 2004-2006,2011,2016,2019 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/tls_messages.h>
#include <botan/kdf.h>
namespace Botan::TLS {
/**
* Session_Keys Constructor
*/
Session_Keys::Session_Keys(const Handshake_State* state,
const secure_vector<uint8_t>& 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 uint8_t MASTER_SECRET_MAGIC[] = {
0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
const uint8_t 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 uint8_t KEY_GEN_MAGIC[] = {
0x6B, 0x65, 0x79, 0x20, 0x65, 0x78, 0x70, 0x61, 0x6E, 0x73, 0x69, 0x6F, 0x6E };
auto 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
{
std::vector<uint8_t> salt;
std::vector<uint8_t> label;
if(extended_master_secret)
{
label.assign(EXT_MASTER_SECRET_MAGIC, EXT_MASTER_SECRET_MAGIC + sizeof(EXT_MASTER_SECRET_MAGIC));
salt += state->hash().final(state->ciphersuite().prf_algo());
}
else
{
label.assign(MASTER_SECRET_MAGIC, 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, label);
}
std::vector<uint8_t> salt;
std::vector<uint8_t> label;
label.assign(KEY_GEN_MAGIC, KEY_GEN_MAGIC + sizeof(KEY_GEN_MAGIC));
salt += state->server_hello()->random();
salt += state->client_hello()->random();
const secure_vector<uint8_t> prf_output = prf->derive_key(
prf_gen,
m_master_sec.data(), m_master_sec.size(),
salt.data(), salt.size(),
label.data(), label.size());
const uint8_t* key_data = prf_output.data();
m_c_aead.resize(mac_keylen + cipher_keylen);
m_s_aead.resize(mac_keylen + cipher_keylen);
copy_mem(&m_c_aead[0], key_data, mac_keylen);
copy_mem(&m_s_aead[0], key_data + mac_keylen, mac_keylen);
copy_mem(&m_c_aead[mac_keylen], key_data + 2*mac_keylen, cipher_keylen);
copy_mem(&m_s_aead[mac_keylen], key_data + 2*mac_keylen + cipher_keylen, cipher_keylen);
m_c_nonce.resize(cipher_nonce_bytes);
m_s_nonce.resize(cipher_nonce_bytes);
copy_mem(&m_c_nonce[0], key_data + 2*(mac_keylen + cipher_keylen), cipher_nonce_bytes);
copy_mem(&m_s_nonce[0], key_data + 2*(mac_keylen + cipher_keylen) + cipher_nonce_bytes, cipher_nonce_bytes);
}
}
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