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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_server_max_fragment_length.h"
#include <sys/param.h>
#include "error/s2n_errno.h"
#include "stuffer/s2n_stuffer.h"
#include "tls/s2n_connection.h"
#include "tls/s2n_tls.h"
#include "tls/s2n_tls_parameters.h"
#include "utils/s2n_safety.h"
static bool s2n_max_fragment_length_should_send(struct s2n_connection *conn);
static int s2n_max_fragment_length_send(struct s2n_connection *conn, struct s2n_stuffer *out);
static int s2n_max_fragment_length_recv(struct s2n_connection *conn, struct s2n_stuffer *extension);
const s2n_extension_type s2n_server_max_fragment_length_extension = {
.iana_value = TLS_EXTENSION_MAX_FRAG_LEN,
.is_response = true,
.send = s2n_max_fragment_length_send,
.recv = s2n_max_fragment_length_recv,
.should_send = s2n_max_fragment_length_should_send,
.if_missing = s2n_extension_noop_if_missing,
};
static bool s2n_max_fragment_length_should_send(struct s2n_connection *conn)
{
return conn && conn->negotiated_mfl_code != S2N_TLS_MAX_FRAG_LEN_EXT_NONE;
}
static int s2n_max_fragment_length_send(struct s2n_connection *conn, struct s2n_stuffer *out)
{
POSIX_ENSURE_REF(conn);
POSIX_GUARD(s2n_stuffer_write_uint8(out, conn->negotiated_mfl_code));
return S2N_SUCCESS;
}
static int s2n_max_fragment_length_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
{
POSIX_ENSURE_REF(conn);
POSIX_ENSURE_REF(conn->config);
uint8_t mfl_code;
POSIX_GUARD(s2n_stuffer_read_uint8(extension, &mfl_code));
/*
*= https://tools.ietf.org/rfc/rfc6066#section-4
*# Similarly, if a client
*# receives a maximum fragment length negotiation response that differs
*# from the length it requested, it MUST also abort the handshake with
*# an "illegal_parameter" alert.
*/
S2N_ERROR_IF(mfl_code != conn->config->mfl_code, S2N_ERR_MAX_FRAG_LEN_MISMATCH);
/*
*= https://tools.ietf.org/rfc/rfc6066#section-4
*# Once a maximum fragment length other than 2^14 has been successfully
*# negotiated, the client and server MUST immediately begin fragmenting
*# messages (including handshake messages) to ensure that no fragment
*# larger than the negotiated length is sent.
*/
conn->negotiated_mfl_code = mfl_code;
POSIX_GUARD_RESULT(s2n_connection_set_max_fragment_length(conn, conn->max_outgoing_fragment_length));
return S2N_SUCCESS;
}
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