Beispiel #1
0
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
                                         Handshake_State& state,
                                         const Policy& policy,
                                         Credentials_Manager& creds,
                                         RandomNumberGenerator& rng,
                                         const Private_Key* signing_key)
   {
   const std::string hostname = state.client_hello()->sni_hostname();
   const Kex_Algo kex_algo = state.ciphersuite().kex_method();

   if(kex_algo == Kex_Algo::PSK || kex_algo == Kex_Algo::DHE_PSK || kex_algo == Kex_Algo::ECDHE_PSK)
      {
      std::string identity_hint =
         creds.psk_identity_hint("tls-server", hostname);

      append_tls_length_value(m_params, identity_hint, 2);
      }

   if(kex_algo == Kex_Algo::DH || kex_algo == Kex_Algo::DHE_PSK)
      {
      const std::vector<Group_Params> dh_groups = state.client_hello()->supported_dh_groups();

      Group_Params shared_group = Group_Params::NONE;

      /*
      If the client does not send any DH groups in the supported groups
      extension, but does offer DH ciphersuites, we select a group arbitrarily
      */

      if(dh_groups.empty())
         {
         shared_group = policy.default_dh_group();
         }
      else
         {
         shared_group = policy.choose_key_exchange_group(dh_groups);
         }

      if(shared_group == Group_Params::NONE)
         throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
               "Could not agree on a DH group with the client");

      BOTAN_ASSERT(group_param_is_dh(shared_group), "DH groups for the DH ciphersuites god");

      const std::string group_name = state.callbacks().tls_decode_group_param(shared_group);
      std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, DL_Group(group_name)));

      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
      append_tls_length_value(m_params, dh->public_value(), 2);
      m_kex_key.reset(dh.release());
      }
   else if(kex_algo == Kex_Algo::ECDH || kex_algo == Kex_Algo::ECDHE_PSK)
      {
      const std::vector<Group_Params> ec_groups = state.client_hello()->supported_ecc_curves();

      if(ec_groups.empty())
         throw Internal_Error("Client sent no ECC extension but we negotiated ECDH");

      Group_Params shared_group = policy.choose_key_exchange_group(ec_groups);

      if(shared_group == Group_Params::NONE)
         throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "No shared ECC group with client");

      std::vector<uint8_t> ecdh_public_val;

      if(shared_group == Group_Params::X25519)
         {
#if defined(BOTAN_HAS_CURVE_25519)
         std::unique_ptr<Curve25519_PrivateKey> x25519(new Curve25519_PrivateKey(rng));
         ecdh_public_val = x25519->public_value();
         m_kex_key.reset(x25519.release());
#else
         throw Internal_Error("Negotiated X25519 somehow, but it is disabled");
#endif
         }
      else
         {
         Group_Params curve = policy.choose_key_exchange_group(ec_groups);

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

         EC_Group ec_group(curve_name);
         std::unique_ptr<ECDH_PrivateKey> ecdh(new ECDH_PrivateKey(rng, ec_group));

         // follow client's preference for point compression
         ecdh_public_val = ecdh->public_value(
            state.client_hello()->prefers_compressed_ec_points() ?
            PointGFp::COMPRESSED : PointGFp::UNCOMPRESSED);

         m_kex_key.reset(ecdh.release());
         }

      const uint16_t named_curve_id = static_cast<uint16_t>(shared_group);
      m_params.push_back(3); // named curve
      m_params.push_back(get_byte(0, named_curve_id));
      m_params.push_back(get_byte(1, named_curve_id));

      append_tls_length_value(m_params, ecdh_public_val, 1);
      }
#if defined(BOTAN_HAS_SRP6)
   else if(kex_algo == Kex_Algo::SRP_SHA)
      {
      const std::string srp_identifier = state.client_hello()->srp_identifier();

      std::string group_id;
      BigInt v;
      std::vector<uint8_t> salt;

      const bool found = creds.srp_verifier("tls-server", hostname,
                                            srp_identifier,
                                            group_id, v, salt,
                                            policy.hide_unknown_users());

      if(!found)
         throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
                             "Unknown SRP user " + srp_identifier);

      m_srp_params.reset(new SRP6_Server_Session);

      BigInt B = m_srp_params->step1(v, group_id,
                                     "SHA-1", rng);

      DL_Group group(group_id);

      append_tls_length_value(m_params, BigInt::encode(group.get_p()), 2);
      append_tls_length_value(m_params, BigInt::encode(group.get_g()), 2);
      append_tls_length_value(m_params, salt, 1);
      append_tls_length_value(m_params, BigInt::encode(B), 2);
      }
#endif
#if defined(BOTAN_HAS_CECPQ1)
   else if(kex_algo == Kex_Algo::CECPQ1)
      {
      std::vector<uint8_t> cecpq1_offer(CECPQ1_OFFER_BYTES);
      m_cecpq1_key.reset(new CECPQ1_key);
      CECPQ1_offer(cecpq1_offer.data(), m_cecpq1_key.get(), rng);
      append_tls_length_value(m_params, cecpq1_offer, 2);
      }
#endif
   else if(kex_algo != Kex_Algo::PSK)
      {
      throw Internal_Error("Server_Key_Exchange: Unknown kex type " +
                           kex_method_to_string(kex_algo));
      }

   if(state.ciphersuite().signature_used())
      {
      BOTAN_ASSERT(signing_key, "Signing key was set");

      std::pair<std::string, Signature_Format> format =
         state.choose_sig_format(*signing_key, m_scheme, false, policy);

      std::vector<uint8_t> buf = state.client_hello()->random();

      buf += state.server_hello()->random();
      buf += params();

      m_signature =
         state.callbacks().tls_sign_message(*signing_key, rng,
                                            format.first, format.second, buf);
      }

   state.hash().update(io.send(*this));
   }
Beispiel #2
0
/*
* Read a Client Key Exchange message
*/
Client_Key_Exchange::Client_Key_Exchange(const std::vector<byte>& contents,
                                         const Handshake_State& state,
                                         const Private_Key* server_rsa_kex_key,
                                         Credentials_Manager& creds,
                                         const Policy& policy,
                                         RandomNumberGenerator& rng)
   {
   const std::string kex_algo = state.ciphersuite().kex_algo();

   if(kex_algo == "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());

      PK_Decryptor_EME decryptor(*server_rsa_kex_key, "PKCS1v15");

      Protocol_Version client_version = state.client_hello()->version();

      /*
      * This is used as the pre-master if RSA decryption fails.
      * Otherwise we can be used as an oracle. See Bleichenbacher
      * "Chosen Ciphertext Attacks against Protocols Based on RSA
      * Encryption Standard PKCS #1", Crypto 98
      *
      * Create it here instead if in the catch clause as otherwise we
      * expose a timing channel WRT the generation of the fake value.
      * Some timing channel likely remains due to exception handling
      * and the like.
      */
      secure_vector<byte> fake_pre_master = rng.random_vec(48);
      fake_pre_master[0] = client_version.major_version();
      fake_pre_master[1] = client_version.minor_version();

      try
         {
         TLS_Data_Reader reader("ClientKeyExchange", contents);
         m_pre_master = decryptor.decrypt(reader.get_range<byte>(2, 0, 65535));

         if(m_pre_master.size() != 48 ||
            client_version.major_version() != m_pre_master[0] ||
            client_version.minor_version() != m_pre_master[1])
            {
            throw Decoding_Error("Client_Key_Exchange: Secret corrupted");
            }
         }
      catch(...)
         {
         m_pre_master = fake_pre_master;
         }
      }
   else
      {
      TLS_Data_Reader reader("ClientKeyExchange", contents);

      SymmetricKey psk;

      if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
         {
         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 == "PSK")
         {
         std::vector<byte> 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 == "SRP_SHA")
         {
         SRP6_Server_Session& srp = state.server_kex()->server_srp_params();

         m_pre_master = srp.step2(BigInt::decode(reader.get_range<byte>(2, 0, 65535))).bits_of();
         }
#endif
      else if(kex_algo == "DH" || kex_algo == "DHE_PSK" ||
              kex_algo == "ECDH" || 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());

         try
            {
            PK_Key_Agreement ka(*ka_key, "Raw");

            std::vector<byte> client_pubkey;

            if(ka_key->algo_name() == "DH")
               client_pubkey = reader.get_range<byte>(2, 0, 65535);
            else
               client_pubkey = reader.get_range<byte>(1, 0, 255);

            secure_vector<byte> 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 == "DHE_PSK" || 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(std::exception &)
            {
            /*
            * Something failed in the DH computation. To avoid possible
            * timing attacks, randomize the pre-master output and carry
            * on, allowing the protocol to fail later in the finished
            * checks.
            */
            m_pre_master = rng.random_vec(ka_key->public_value().size());
            }
         }
      else
         throw Internal_Error("Client_Key_Exchange: Unknown kex type " + kex_algo);
      }
   }
Beispiel #3
0
/*
* 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 std::string kex_algo = state.ciphersuite().kex_algo();

   if(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<byte> 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 == "DHE_PSK" || 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 == "DH" || kex_algo == "DHE_PSK")
         {
         BigInt p = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
         BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
         BigInt Y = BigInt::decode(reader.get_range<byte>(2, 1, 65535));

         if(reader.remaining_bytes())
            throw Decoding_Error("Bad params size for DH key exchange");

         if(p.bits() < policy.minimum_dh_group_size())
            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
                                "Server sent DH group of " +
                                std::to_string(p.bits()) +
                                " bits, policy requires at least " +
                                std::to_string(policy.minimum_dh_group_size()));

         /*
         * A basic check for key validity. As we do not know q here we
         * cannot check that Y is in the right subgroup. However since
         * our key is ephemeral there does not seem to be any
         * advantage to bogus keys anyway.
         */
         if(Y <= 1 || Y >= p - 1)
            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
                                "Server sent bad DH key for DHE exchange");

         DL_Group group(p, g);

         if(!group.verify_group(rng, false))
            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
                                "DH group validation failed");

         DH_PublicKey counterparty_key(group, Y);

         DH_PrivateKey priv_key(rng, group);

         PK_Key_Agreement ka(priv_key, "Raw");

         secure_vector<byte> dh_secret = CT::strip_leading_zeros(
            ka.derive_key(0, counterparty_key.public_value()).bits_of());

         if(kex_algo == "DH")
            m_pre_master = dh_secret;
         else
            {
            append_tls_length_value(m_pre_master, dh_secret, 2);
            append_tls_length_value(m_pre_master, psk.bits_of(), 2);
            }

         append_tls_length_value(m_key_material, priv_key.public_value(), 2);
         }
      else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
         {
         const byte curve_type = reader.get_byte();

         if(curve_type != 3)
            throw Decoding_Error("Server sent non-named ECC curve");

         const u16bit curve_id = reader.get_u16bit();

         const std::string name = Supported_Elliptic_Curves::curve_id_to_name(curve_id);

         if(name == "")
            throw Decoding_Error("Server sent unknown named curve " + std::to_string(curve_id));

         EC_Group group(name);

         std::vector<byte> ecdh_key = reader.get_range<byte>(1, 1, 255);

         ECDH_PublicKey counterparty_key(group, OS2ECP(ecdh_key, group.get_curve()));

         ECDH_PrivateKey priv_key(rng, group);

         PK_Key_Agreement ka(priv_key, "Raw");

         secure_vector<byte> ecdh_secret =
            ka.derive_key(0, counterparty_key.public_value()).bits_of();

         if(kex_algo == "ECDH")
            m_pre_master = ecdh_secret;
         else
            {
            append_tls_length_value(m_pre_master, ecdh_secret, 2);
            append_tls_length_value(m_pre_master, psk.bits_of(), 2);
            }

         append_tls_length_value(m_key_material, priv_key.public_value(), 1);
         }
#if defined(BOTAN_HAS_SRP6)
      else if(kex_algo == "SRP_SHA")
         {
         const BigInt N = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
         const BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
         std::vector<byte> salt = reader.get_range<byte>(1, 1, 255);
         const BigInt B = BigInt::decode(reader.get_range<byte>(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
      else
         {
         throw Internal_Error("Client_Key_Exchange: Unknown kex " +
                              kex_algo);
         }

      reader.assert_done();
      }
   else
      {
      // No server key exchange msg better mean RSA kex + RSA key in cert

      if(kex_algo != "RSA")
         throw Unexpected_Message("No server kex but negotiated kex " + kex_algo);

      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();

         m_pre_master = rng.random_vec(48);
         m_pre_master[0] = offered_version.major_version();
         m_pre_master[1] = offered_version.minor_version();

         PK_Encryptor_EME encryptor(*rsa_pub, "PKCS1v15");

         const std::vector<byte> 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));
   }
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
                                         Handshake_State& state,
                                         const Policy& policy,
                                         Credentials_Manager& creds,
                                         RandomNumberGenerator& rng,
                                         const Private_Key* signing_key)
   {
   const std::string hostname = state.client_hello()->sni_hostname();
   const std::string kex_algo = state.ciphersuite().kex_algo();

   if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
      {
      std::string identity_hint =
         creds.psk_identity_hint("tls-server", hostname);

      append_tls_length_value(m_params, identity_hint, 2);
      }

   if(kex_algo == "DH" || kex_algo == "DHE_PSK")
      {
      std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, DL_Group(policy.dh_group())));

      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
      append_tls_length_value(m_params, dh->public_value(), 2);
      m_kex_key.reset(dh.release());
      }
   else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
      {
      const std::vector<std::string>& curves =
         state.client_hello()->supported_ecc_curves();

      if(curves.empty())
         throw Internal_Error("Client sent no ECC extension but we negotiated ECDH");

      const std::string curve_name = policy.choose_curve(curves);

      if(curve_name == "")
         throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
                             "Could not agree on an ECC curve with the client");

      EC_Group ec_group(curve_name);

      std::unique_ptr<ECDH_PrivateKey> ecdh(new ECDH_PrivateKey(rng, ec_group));

      const std::string ecdh_domain_oid = ecdh->domain().get_oid();
      const std::string domain = OIDS::lookup(OID(ecdh_domain_oid));

      if(domain == "")
         throw Internal_Error("Could not find name of ECDH domain " + ecdh_domain_oid);

      const u16bit named_curve_id = Supported_Elliptic_Curves::name_to_curve_id(domain);

      m_params.push_back(3); // named curve
      m_params.push_back(get_byte(0, named_curve_id));
      m_params.push_back(get_byte(1, named_curve_id));

      append_tls_length_value(m_params, ecdh->public_value(), 1);

      m_kex_key.reset(ecdh.release());
      }
#if defined(BOTAN_HAS_SRP6)
   else if(kex_algo == "SRP_SHA")
      {
      const std::string srp_identifier = state.client_hello()->srp_identifier();

      std::string group_id;
      BigInt v;
      std::vector<byte> salt;

      const bool found = creds.srp_verifier("tls-server", hostname,
                                            srp_identifier,
                                            group_id, v, salt,
                                            policy.hide_unknown_users());

      if(!found)
         throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
                             "Unknown SRP user " + srp_identifier);

      m_srp_params.reset(new SRP6_Server_Session);

      BigInt B = m_srp_params->step1(v, group_id,
                                     "SHA-1", rng);

      DL_Group group(group_id);

      append_tls_length_value(m_params, BigInt::encode(group.get_p()), 2);
      append_tls_length_value(m_params, BigInt::encode(group.get_g()), 2);
      append_tls_length_value(m_params, salt, 1);
      append_tls_length_value(m_params, BigInt::encode(B), 2);
      }
#endif
   else if(kex_algo != "PSK")
      throw Internal_Error("Server_Key_Exchange: Unknown kex type " + kex_algo);

   if(state.ciphersuite().sig_algo() != "")
      {
      BOTAN_ASSERT(signing_key, "Signing key was set");

      std::pair<std::string, Signature_Format> format =
         state.choose_sig_format(*signing_key, m_hash_algo, m_sig_algo, false, policy);

      PK_Signer signer(*signing_key, format.first, format.second);

      signer.update(state.client_hello()->random());
      signer.update(state.server_hello()->random());
      signer.update(params());
      m_signature = signer.signature(rng);
      }

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