/* * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/apache2.0 * * or in the "license" file accompanying this file. This file is distributed * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either * express or implied. See the License for the specific language governing * permissions and limitations under the License. */ #include <stdint.h> #include <sys/param.h> #include "tls/extensions/s2n_ems.h" #include "tls/s2n_tls.h" #include "utils/s2n_safety.h" static int s2n_server_ems_recv(struct s2n_connection *conn, struct s2n_stuffer *extension); static bool s2n_server_ems_should_send(struct s2n_connection *conn); static int s2n_server_ems_if_missing(struct s2n_connection *conn); /** *= https://tools.ietf.org/rfc/rfc7627#section-5.1 *# *# This document defines a new TLS extension, "extended_master_secret" *# (with extension type 0x0017), which is used to signal both client and *# server to use the extended master secret computation. The *# "extension_data" field of this extension is empty. Thus, the entire *# encoding of the extension is 00 17 00 00 (in hexadecimal.) **/ const s2n_extension_type s2n_server_ems_extension = { .iana_value = TLS_EXTENSION_EMS, .is_response = true, .send = s2n_extension_send_noop, .recv = s2n_server_ems_recv, .should_send = s2n_server_ems_should_send, .if_missing = s2n_server_ems_if_missing, }; static int s2n_server_ems_recv(struct s2n_connection *conn, struct s2n_stuffer *extension) { POSIX_ENSURE_REF(conn); /* Read nothing. The extension just needs to exist without any data. */ POSIX_ENSURE(s2n_stuffer_data_available(extension) == 0, S2N_ERR_UNSUPPORTED_EXTENSION); conn->ems_negotiated = true; return S2N_SUCCESS; } static bool s2n_server_ems_should_send(struct s2n_connection *conn) { return conn && conn->actual_protocol_version < S2N_TLS13; } static int s2n_server_ems_if_missing(struct s2n_connection *conn) { POSIX_ENSURE_REF(conn); /** *= https://tools.ietf.org/rfc/rfc7627#section-5.3 *# If the original session used the extension but the new ServerHello *# does not contain the extension, the client MUST abort the *# handshake. **/ POSIX_ENSURE(!conn->ems_negotiated, S2N_ERR_MISSING_EXTENSION); return S2N_SUCCESS; }