/*

* Client Key Exchange Message

* (C) 2004-2010,2016 Jack Lloyd

*     2017 Harry Reimann, Rohde & Schwarz Cybersecurity

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/tls_messages.h>

#include <botan/tls_extensions.h>

#include <botan/rng.h>

#include <botan/internal/tls_reader.h>

#include <botan/internal/tls_handshake_io.h>

#include <botan/internal/tls_handshake_state.h>

#include <botan/internal/tls_handshake_hash.h>

#include <botan/credentials_manager.h>

#include <botan/internal/ct_utils.h>

#include <botan/rsa.h>

#if defined(BOTAN_HAS_CECPQ1)

  #include <botan/cecpq1.h>

#endif

#if defined(BOTAN_HAS_SRP6)

  #include <botan/srp6.h>

#endif

namespace Botan {

namespace TLS {

/*

* Create a new Client Key Exchange message

*/

Client_Key_Exchange::Client_Key_Exchange(Handshake_IO& io,

                                         Handshake_State& state,

                                         const Policy& policy,

                                         Credentials_Manager& creds,

                                         const Public_Key* server_public_key,

                                         const std::string& hostname,

                                         RandomNumberGenerator& rng)

   {

   const Kex_Algo kex_algo = state.ciphersuite().kex_method();

   if(kex_algo == Kex_Algo::PSK)

      {

      std::string identity_hint = "";

      if(state.server_kex())

         {

         TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());

         identity_hint = reader.get_string(2, 0, 65535);

         }

      const std::string psk_identity =

         creds.psk_identity("tls-client", hostname, identity_hint);

      append_tls_length_value(m_key_material, psk_identity, 2);

      SymmetricKey psk = creds.psk("tls-client", hostname, psk_identity);

      std::vector<uint8_t> zeros(psk.length());

      append_tls_length_value(m_pre_master, zeros, 2);

      append_tls_length_value(m_pre_master, psk.bits_of(), 2);

      }

   else if(state.server_kex())

      {

      TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());

      SymmetricKey psk;

      if(kex_algo == Kex_Algo::DHE_PSK ||

         kex_algo == Kex_Algo::ECDHE_PSK)

         {

         std::string identity_hint = reader.get_string(2, 0, 65535);

         const std::string psk_identity =

            creds.psk_identity("tls-client", hostname, identity_hint);

         append_tls_length_value(m_key_material, psk_identity, 2);

         psk = creds.psk("tls-client", hostname, psk_identity);

         }

      if(kex_algo == Kex_Algo::DH ||

         kex_algo == Kex_Algo::DHE_PSK)

         {

         const std::vector<uint8_t> modulus = reader.get_range<uint8_t>(2, 1, 65535);

         const std::vector<uint8_t> generator = reader.get_range<uint8_t>(2, 1, 65535);

         const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(2, 1, 65535);

         if(reader.remaining_bytes())

            throw Decoding_Error("Bad params size for DH key exchange");

         const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> dh_result =

            state.callbacks().tls_dh_agree(modulus, generator, peer_public_value, policy, rng);

         if(kex_algo == Kex_Algo::DH)

            m_pre_master = dh_result.first;

         else

            {

            append_tls_length_value(m_pre_master, dh_result.first, 2);

            append_tls_length_value(m_pre_master, psk.bits_of(), 2);

            }

         append_tls_length_value(m_key_material, dh_result.second, 2);

         }

      else if(kex_algo == Kex_Algo::ECDH ||

              kex_algo == Kex_Algo::ECDHE_PSK)

         {

         const uint8_t curve_type = reader.get_byte();

         if(curve_type != 3)

            throw Decoding_Error("Server sent non-named ECC curve");

         const Group_Params curve_id = static_cast<Group_Params>(reader.get_uint16_t());

         const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(1, 1, 255);

         if(policy.choose_key_exchange_group({curve_id}) != curve_id)

            {

            throw TLS_Exception(Alert::HANDSHAKE_FAILURE,

                                "Server sent ECC curve prohibited by policy");

            }

         const std::string curve_name = state.callbacks().tls_decode_group_param(curve_id);

         if(curve_name == "")

            throw Decoding_Error("Server sent unknown named curve " +

                                 std::to_string(static_cast<uint16_t>(curve_id)));

         const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> ecdh_result =

            state.callbacks().tls_ecdh_agree(curve_name, peer_public_value, policy, rng,

                                             state.server_hello()->prefers_compressed_ec_points());

         if(kex_algo == Kex_Algo::ECDH)

            {

            m_pre_master = ecdh_result.first;

            }

         else

            {

            append_tls_length_value(m_pre_master, ecdh_result.first, 2);

            append_tls_length_value(m_pre_master, psk.bits_of(), 2);

            }

         append_tls_length_value(m_key_material, ecdh_result.second, 1);

         }

#if defined(BOTAN_HAS_SRP6)

      else if(kex_algo == Kex_Algo::SRP_SHA)

         {

         const BigInt N = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));

         const BigInt g = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));

         std::vector<uint8_t> salt = reader.get_range<uint8_t>(1, 1, 255);

         const BigInt B = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));

         const std::string srp_group = srp6_group_identifier(N, g);

         const std::string srp_identifier =

            creds.srp_identifier("tls-client", hostname);

         const std::string srp_password =

            creds.srp_password("tls-client", hostname, srp_identifier);

         std::pair<BigInt, SymmetricKey> srp_vals =

            srp6_client_agree(srp_identifier,

                              srp_password,

                              srp_group,

                              "SHA-1",

                              salt,

                              B,

                              rng);

         append_tls_length_value(m_key_material, BigInt::encode(srp_vals.first), 2);

         m_pre_master = srp_vals.second.bits_of();

         }

#endif

#if defined(BOTAN_HAS_CECPQ1)

      else if(kex_algo == Kex_Algo::CECPQ1)

         {

         const std::vector<uint8_t> cecpq1_offer = reader.get_range<uint8_t>(2, 1, 65535);

         if(cecpq1_offer.size() != CECPQ1_OFFER_BYTES)

            throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Invalid CECPQ1 key size");

         std::vector<uint8_t> newhope_accept(CECPQ1_ACCEPT_BYTES);

         secure_vector<uint8_t> shared_secret(CECPQ1_SHARED_KEY_BYTES);

         CECPQ1_accept(shared_secret.data(), newhope_accept.data(), cecpq1_offer.data(), rng);

         append_tls_length_value(m_key_material, newhope_accept, 2);

         m_pre_master = shared_secret;

         }

#endif

      else

         {

         throw Internal_Error("Client_Key_Exchange: Unknown key exchange method was negotiated");

         }

      reader.assert_done();

      }

   else

      {

      // No server key exchange msg better mean RSA kex + RSA key in cert

      if(kex_algo != Kex_Algo::STATIC_RSA)

         throw Unexpected_Message("No server kex message, but negotiated a key exchange that required it");

      if(!server_public_key)

         throw Internal_Error("No server public key for RSA exchange");

      if(auto rsa_pub = dynamic_cast<const RSA_PublicKey*>(server_public_key))

         {

         const Protocol_Version offered_version = state.client_hello()->version();

         rng.random_vec(m_pre_master, 48);

         m_pre_master[0] = offered_version.major_version();

         m_pre_master[1] = offered_version.minor_version();

         PK_Encryptor_EME encryptor(*rsa_pub, rng, "PKCS1v15");

         const std::vector<uint8_t> encrypted_key = encryptor.encrypt(m_pre_master, rng);

         append_tls_length_value(m_key_material, encrypted_key, 2);

         }

      else

         throw TLS_Exception(Alert::HANDSHAKE_FAILURE,

                             "Expected a RSA key in server cert but got " +

                             server_public_key->algo_name());

      }

   state.hash().update(io.send(*this));

   }

/*

* Read a Client Key Exchange message

*/

Client_Key_Exchange::Client_Key_Exchange(const std::vector<uint8_t>& contents,

                                         const Handshake_State& state,

                                         const Private_Key* server_rsa_kex_key,

                                         Credentials_Manager& creds,

                                         const Policy& policy,

                                         RandomNumberGenerator& rng)

   {

   const Kex_Algo kex_algo = state.ciphersuite().kex_method();

   if(kex_algo == Kex_Algo::STATIC_RSA)

      {

      BOTAN_ASSERT(state.server_certs() && !state.server_certs()->cert_chain().empty(),

                   "RSA key exchange negotiated so server sent a certificate");

      if(!server_rsa_kex_key)

         throw Internal_Error("Expected RSA kex but no server kex key set");

      if(!dynamic_cast<const RSA_PrivateKey*>(server_rsa_kex_key))

         throw Internal_Error("Expected RSA key but got " + server_rsa_kex_key->algo_name());

      TLS_Data_Reader reader("ClientKeyExchange", contents);

      const std::vector<uint8_t> encrypted_pre_master = reader.get_range<uint8_t>(2, 0, 65535);

      reader.assert_done();

      PK_Decryptor_EME decryptor(*server_rsa_kex_key, rng, "PKCS1v15");

      const uint8_t client_major = state.client_hello()->version().major_version();

      const uint8_t client_minor = state.client_hello()->version().minor_version();

      /*

      * PK_Decryptor::decrypt_or_random will return a random value if

      * either the length does not match the expected value or if the

      * version number embedded in the PMS does not match the one sent

      * in the client hello.

      */

      const size_t expected_plaintext_size = 48;

      const size_t expected_content_size = 2;

      const uint8_t expected_content_bytes[expected_content_size] = { client_major, client_minor };

      const uint8_t expected_content_pos[expected_content_size] = { 0, 1 };

      m_pre_master =

         decryptor.decrypt_or_random(encrypted_pre_master.data(),

                                     encrypted_pre_master.size(),

                                     expected_plaintext_size,

                                     rng,

                                     expected_content_bytes,

                                     expected_content_pos,

                                     expected_content_size);

      }

   else

      {

      TLS_Data_Reader reader("ClientKeyExchange", contents);

      SymmetricKey psk;

      if(key_exchange_is_psk(kex_algo))

         {

         const std::string psk_identity = reader.get_string(2, 0, 65535);

         psk = creds.psk("tls-server",

                         state.client_hello()->sni_hostname(),

                         psk_identity);

         if(psk.length() == 0)

            {

            if(policy.hide_unknown_users())

               psk = SymmetricKey(rng, 16);

            else

               throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,

                                   "No PSK for identifier " + psk_identity);

            }

         }

      if(kex_algo == Kex_Algo::PSK)

         {

         std::vector<uint8_t> zeros(psk.length());

         append_tls_length_value(m_pre_master, zeros, 2);

         append_tls_length_value(m_pre_master, psk.bits_of(), 2);

         }

#if defined(BOTAN_HAS_SRP6)

      else if(kex_algo == Kex_Algo::SRP_SHA)

         {

         SRP6_Server_Session& srp = state.server_kex()->server_srp_params();

         m_pre_master = srp.step2(BigInt::decode(reader.get_range<uint8_t>(2, 0, 65535))).bits_of();

         }

#endif

#if defined(BOTAN_HAS_CECPQ1)

      else if(kex_algo == Kex_Algo::CECPQ1)

         {

         const CECPQ1_key& cecpq1_offer = state.server_kex()->cecpq1_key();

         const std::vector<uint8_t> cecpq1_accept = reader.get_range<uint8_t>(2, 0, 65535);

         if(cecpq1_accept.size() != CECPQ1_ACCEPT_BYTES)

            throw Decoding_Error("Invalid size for CECPQ1 accept message");

         m_pre_master.resize(CECPQ1_SHARED_KEY_BYTES);

         CECPQ1_finish(m_pre_master.data(), cecpq1_offer, cecpq1_accept.data());

         }

#endif

      else if(kex_algo == Kex_Algo::DH ||

              kex_algo == Kex_Algo::DHE_PSK ||

              kex_algo == Kex_Algo::ECDH ||

              kex_algo == Kex_Algo::ECDHE_PSK)

         {

         const Private_Key& private_key = state.server_kex()->server_kex_key();

         const PK_Key_Agreement_Key* ka_key =

            dynamic_cast<const PK_Key_Agreement_Key*>(&private_key);

         if(!ka_key)

            throw Internal_Error("Expected key agreement key type but got " +

                                 private_key.algo_name());

         std::vector<uint8_t> client_pubkey;

         if(ka_key->algo_name() == "DH")

            {

            client_pubkey = reader.get_range<uint8_t>(2, 0, 65535);

            }

         else

            {

            client_pubkey = reader.get_range<uint8_t>(1, 1, 255);

            }

         try

            {

            PK_Key_Agreement ka(*ka_key, rng, "Raw");

            secure_vector<uint8_t> shared_secret = ka.derive_key(0, client_pubkey).bits_of();

            if(ka_key->algo_name() == "DH")

               shared_secret = CT::strip_leading_zeros(shared_secret);

            if(kex_algo == Kex_Algo::DHE_PSK ||

               kex_algo == Kex_Algo::ECDHE_PSK)

               {

               append_tls_length_value(m_pre_master, shared_secret, 2);

               append_tls_length_value(m_pre_master, psk.bits_of(), 2);

               }

            else

               m_pre_master = shared_secret;

            }

         catch(Invalid_Argument& e)

            {

            throw TLS_Exception(Alert::ILLEGAL_PARAMETER, e.what());

            }

         catch(std::exception&)

            {

            /*

            * Something failed in the DH/ECDH computation. To avoid possible

            * attacks which are based on triggering and detecting some edge

            * failure condition, randomize the pre-master output and carry on,

            * allowing the protocol to fail later in the finished checks.

            */

            rng.random_vec(m_pre_master, ka_key->public_value().size());

            }

         reader.assert_done();

         }

      else

         throw Internal_Error("Client_Key_Exchange: Unknown key exchange negotiated");

      }

   }

}

}