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/*
* 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 "tls/extensions/s2n_npn.h"
#include "tls/extensions/s2n_client_alpn.h"
#include "tls/extensions/s2n_server_alpn.h"
#include "tls/s2n_protocol_preferences.h"
#include "tls/s2n_tls.h"
#include "tls/s2n_tls_parameters.h"
#include "utils/s2n_safety.h"
bool s2n_npn_should_send(struct s2n_connection *conn)
{
/*
*= https://datatracker.ietf.org/doc/id/draft-agl-tls-nextprotoneg-03#section-3
*# For the same reasons, after a handshake has been performed for a
*# given connection, renegotiations on the same connection MUST NOT
*# include the "next_protocol_negotiation" extension.
*/
return s2n_client_alpn_should_send(conn) && conn->config->npn_supported && !s2n_handshake_is_renegotiation(conn);
}
int s2n_client_npn_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
{
/* Only use the NPN extension to negotiate a protocol if we don't have
* an option to use the ALPN extension.
*/
if (s2n_npn_should_send(conn) && !s2n_server_alpn_should_send(conn)) {
conn->npn_negotiated = true;
}
return S2N_SUCCESS;
}
const s2n_extension_type s2n_client_npn_extension = {
.iana_value = TLS_EXTENSION_NPN,
.is_response = false,
.send = s2n_extension_send_noop,
.recv = s2n_client_npn_recv,
.should_send = s2n_npn_should_send,
.if_missing = s2n_extension_noop_if_missing,
};
bool s2n_server_npn_should_send(struct s2n_connection *conn)
{
return conn->npn_negotiated;
}
int s2n_server_npn_send(struct s2n_connection *conn, struct s2n_stuffer *out)
{
struct s2n_blob *app_protocols = NULL;
POSIX_GUARD(s2n_connection_get_protocol_preferences(conn, &app_protocols));
POSIX_ENSURE_REF(app_protocols);
POSIX_GUARD(s2n_stuffer_write(out, app_protocols));
return S2N_SUCCESS;
}
int s2n_server_npn_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
{
struct s2n_blob *supported_protocols = NULL;
POSIX_GUARD(s2n_connection_get_protocol_preferences(conn, &supported_protocols));
POSIX_ENSURE_REF(supported_protocols);
if (supported_protocols->size == 0) {
/* No protocols configured */
return S2N_SUCCESS;
}
/*
*= https://datatracker.ietf.org/doc/id/draft-agl-tls-nextprotoneg-03#section-3
*# The "extension_data" field of a "next_protocol_negotiation" extension
*# in a "ServerHello" contains an optional list of protocols advertised
*# by the server.
*/
if (s2n_stuffer_data_available(extension)) {
POSIX_GUARD_RESULT(s2n_select_server_preference_protocol(conn, extension, supported_protocols));
}
/*
*= https://datatracker.ietf.org/doc/id/draft-agl-tls-nextprotoneg-03#section-4
*# In the event that the client doesn't support any of server's protocols, or
*# the server doesn't advertise any, it SHOULD select the first protocol
*# that it supports.
*/
if (s2n_get_application_protocol(conn) == NULL) {
struct s2n_stuffer stuffer = { 0 };
POSIX_GUARD(s2n_stuffer_init(&stuffer, supported_protocols));
POSIX_GUARD(s2n_stuffer_skip_write(&stuffer, supported_protocols->size));
struct s2n_blob protocol = { 0 };
POSIX_GUARD_RESULT(s2n_protocol_preferences_read(&stuffer, &protocol));
POSIX_ENSURE_LT(protocol.size, sizeof(conn->application_protocol));
POSIX_CHECKED_MEMCPY(conn->application_protocol, protocol.data, protocol.size);
conn->application_protocol[protocol.size] = '\0';
}
conn->npn_negotiated = true;
return S2N_SUCCESS;
}
const s2n_extension_type s2n_server_npn_extension = {
.iana_value = TLS_EXTENSION_NPN,
.is_response = true,
.send = s2n_server_npn_send,
.recv = s2n_server_npn_recv,
.should_send = s2n_server_npn_should_send,
.if_missing = s2n_extension_noop_if_missing,
};
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