Coverage Report

Created: 2021-02-21 07:20

/src/botan/src/lib/tls/tls_session_key.cpp
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/*
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* TLS Session Key
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* (C) 2004-2006,2011,2016,2019 Jack Lloyd
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/internal/tls_session_key.h>
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#include <botan/internal/tls_handshake_state.h>
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#include <botan/tls_messages.h>
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#include <botan/kdf.h>
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namespace Botan {
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namespace TLS {
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/**
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* Session_Keys Constructor
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*/
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Session_Keys::Session_Keys(const Handshake_State* state,
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                           const secure_vector<uint8_t>& pre_master_secret,
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                           bool resuming)
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   {
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   const size_t cipher_keylen = state->ciphersuite().cipher_keylen();
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   const size_t mac_keylen = state->ciphersuite().mac_keylen();
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   const size_t cipher_nonce_bytes = state->ciphersuite().nonce_bytes_from_handshake();
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   const bool extended_master_secret = state->server_hello()->supports_extended_master_secret();
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   const size_t prf_gen = 2 * (mac_keylen + cipher_keylen + cipher_nonce_bytes);
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   const uint8_t MASTER_SECRET_MAGIC[] = {
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      0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
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   const uint8_t EXT_MASTER_SECRET_MAGIC[] = {
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      0x65, 0x78, 0x74, 0x65, 0x6E, 0x64, 0x65, 0x64, 0x20,
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      0x6D, 0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x73, 0x65, 0x63, 0x72, 0x65, 0x74 };
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   const uint8_t KEY_GEN_MAGIC[] = {
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      0x6B, 0x65, 0x79, 0x20, 0x65, 0x78, 0x70, 0x61, 0x6E, 0x73, 0x69, 0x6F, 0x6E };
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   std::unique_ptr<KDF> prf(state->protocol_specific_prf());
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   if(resuming)
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      {
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      // This is actually the master secret saved as part of the session
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      m_master_sec = pre_master_secret;
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      }
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   else
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      {
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      std::vector<uint8_t> salt;
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      std::vector<uint8_t> label;
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      if(extended_master_secret)
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         {
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         label.assign(EXT_MASTER_SECRET_MAGIC, EXT_MASTER_SECRET_MAGIC + sizeof(EXT_MASTER_SECRET_MAGIC));
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         salt += state->hash().final(state->version(),
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                                     state->ciphersuite().prf_algo());
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         }
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      else
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         {
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         label.assign(MASTER_SECRET_MAGIC, MASTER_SECRET_MAGIC + sizeof(MASTER_SECRET_MAGIC));
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         salt += state->client_hello()->random();
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         salt += state->server_hello()->random();
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         }
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      m_master_sec = prf->derive_key(48, pre_master_secret, salt, label);
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      }
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   std::vector<uint8_t> salt;
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   std::vector<uint8_t> label;
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   label.assign(KEY_GEN_MAGIC, KEY_GEN_MAGIC + sizeof(KEY_GEN_MAGIC));
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   salt += state->server_hello()->random();
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   salt += state->client_hello()->random();
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   const secure_vector<uint8_t> prf_output = prf->derive_key(
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      prf_gen,
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      m_master_sec.data(), m_master_sec.size(),
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      salt.data(), salt.size(),
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      label.data(), label.size());
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   const uint8_t* key_data = prf_output.data();
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   m_c_aead.resize(mac_keylen + cipher_keylen);
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   m_s_aead.resize(mac_keylen + cipher_keylen);
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   copy_mem(&m_c_aead[0], key_data, mac_keylen);
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   copy_mem(&m_s_aead[0], key_data + mac_keylen, mac_keylen);
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   copy_mem(&m_c_aead[mac_keylen], key_data + 2*mac_keylen, cipher_keylen);
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   copy_mem(&m_s_aead[mac_keylen], key_data + 2*mac_keylen + cipher_keylen, cipher_keylen);
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   m_c_nonce.resize(cipher_nonce_bytes);
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   m_s_nonce.resize(cipher_nonce_bytes);
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   copy_mem(&m_c_nonce[0], key_data + 2*(mac_keylen + cipher_keylen), cipher_nonce_bytes);
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   copy_mem(&m_s_nonce[0], key_data + 2*(mac_keylen + cipher_keylen) + cipher_nonce_bytes, cipher_nonce_bytes);
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   }
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}
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}