/* * 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 #include #include #include #include #include #include #include #include #include #if defined(BOTAN_HAS_CECPQ1) #include #endif #if defined(BOTAN_HAS_SRP6) #include #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 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 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") { const std::vector modulus = reader.get_range(2, 1, 65535); const std::vector generator = reader.get_range(2, 1, 65535); const std::vector peer_public_value = reader.get_range(2, 1, 65535); if(reader.remaining_bytes()) throw Decoding_Error("Bad params size for DH key exchange"); const std::pair, std::vector> dh_result = state.callbacks().tls_dh_agree(modulus, generator, peer_public_value, policy, rng); if(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 == "ECDH" || 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 uint16_t curve_id = reader.get_uint16_t(); const std::string curve_name = Supported_Elliptic_Curves::curve_id_to_name(curve_id); if(curve_name == "") throw Decoding_Error("Server sent unknown named curve " + std::to_string(curve_id)); if(!policy.allowed_ecc_curve(curve_name)) { throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Server sent ECC curve prohibited by policy"); } const std::vector peer_public_value = reader.get_range(1, 1, 255); const std::pair, std::vector> ecdh_result = state.callbacks().tls_ecdh_agree(curve_name, peer_public_value, policy, rng, state.server_hello()->prefers_compressed_ec_points()); if(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 == "SRP_SHA") { const BigInt N = BigInt::decode(reader.get_range(2, 1, 65535)); const BigInt g = BigInt::decode(reader.get_range(2, 1, 65535)); std::vector salt = reader.get_range(1, 1, 255); const BigInt B = BigInt::decode(reader.get_range(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 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 == "CECPQ1") { const std::vector cecpq1_offer = reader.get_range(2, 1, 65535); if(cecpq1_offer.size() != CECPQ1_OFFER_BYTES) throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Invalid CECPQ1 key size"); std::vector newhope_accept(CECPQ1_ACCEPT_BYTES); secure_vector 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 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(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, rng, "PKCS1v15"); const std::vector 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& 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(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 encrypted_pre_master = reader.get_range(2, 0, 65535); 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(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 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(2, 0, 65535))).bits_of(); } #endif #if defined(BOTAN_HAS_CECPQ1) else if(kex_algo == "CECPQ1") { const CECPQ1_key& cecpq1_offer = state.server_kex()->cecpq1_key(); const std::vector cecpq1_accept = reader.get_range(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 == "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(&private_key); if(!ka_key) throw Internal_Error("Expected key agreement key type but got " + private_key.algo_name()); std::vector client_pubkey; if(ka_key->algo_name() == "DH") { client_pubkey = reader.get_range(2, 0, 65535); } else { client_pubkey = reader.get_range(1, 1, 255); } try { PK_Key_Agreement ka(*ka_key, rng, "Raw"); secure_vector 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); } } } }