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/*
* Copyright (C) 2018 Red Hat, Inc.
*
* Author: Daiki Ueno
*
* This file is part of GnuTLS.
*
* The GnuTLS is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>
*
*/
/* This file contains the code for the Record Size Limit TLS extension.
*/
#include "gnutls_int.h"
#include "errors.h"
#include "num.h"
#include "hello_ext.h"
#include "ext/record_size_limit.h"
static int _gnutls_record_size_limit_recv_params(gnutls_session_t session,
const uint8_t *data,
size_t data_size);
static int _gnutls_record_size_limit_send_params(gnutls_session_t session,
gnutls_buffer_st *extdata);
const hello_ext_entry_st ext_mod_record_size_limit = {
.name = "Record Size Limit",
.tls_id = 28,
.gid = GNUTLS_EXTENSION_RECORD_SIZE_LIMIT,
.client_parse_point = GNUTLS_EXT_MANDATORY,
.server_parse_point = GNUTLS_EXT_MANDATORY,
.validity = GNUTLS_EXT_FLAG_TLS | GNUTLS_EXT_FLAG_DTLS |
GNUTLS_EXT_FLAG_CLIENT_HELLO | GNUTLS_EXT_FLAG_EE |
GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO,
.recv_func = _gnutls_record_size_limit_recv_params,
.send_func = _gnutls_record_size_limit_send_params
};
static int _gnutls_record_size_limit_recv_params(gnutls_session_t session,
const uint8_t *data,
size_t data_size)
{
ssize_t new_size;
const version_entry_st *vers;
DECR_LEN(data_size, 2);
if (data_size != 0)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
new_size = _gnutls_read_uint16(data);
/* protocol error */
if (new_size < 64)
return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
session->internals.hsk_flags |= HSK_RECORD_SIZE_LIMIT_RECEIVED;
/* we do not want to accept sizes outside of our supported range */
if (new_size < (session->internals.allow_small_records ?
MIN_RECORD_SIZE_SMALL :
MIN_RECORD_SIZE)) {
/* for server, reject it by omitting the extension in the reply */
if (session->security_parameters.entity == GNUTLS_SERVER) {
_gnutls_handshake_log(
"EXT[%p]: client requested too small record_size_limit %u; ignoring\n",
session, (unsigned)new_size);
return gnutls_assert_val(0);
} else {
_gnutls_handshake_log(
"EXT[%p]: server requested too small record_size_limit %u; closing the connection\n",
session, (unsigned)new_size);
return gnutls_assert_val(
GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
}
}
session->internals.hsk_flags |= HSK_RECORD_SIZE_LIMIT_NEGOTIATED;
/* client uses the reception of this extension as an
* indication of the request was accepted by the server */
if (session->security_parameters.entity == GNUTLS_CLIENT)
session->security_parameters.max_record_recv_size =
session->security_parameters.max_user_record_recv_size;
_gnutls_handshake_log("EXT[%p]: record_size_limit %u negotiated\n",
session, (unsigned)new_size);
/* subtract 1 octet for content type */
vers = get_version(session);
if (unlikely(vers == NULL))
return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
session->security_parameters.max_record_send_size =
MIN(new_size - vers->tls13_sem,
session->security_parameters.max_user_record_send_size);
return 0;
}
/* returns data_size or a negative number on failure
*/
static int _gnutls_record_size_limit_send_params(gnutls_session_t session,
gnutls_buffer_st *extdata)
{
int ret;
uint16_t send_size;
assert(session->security_parameters.max_user_record_recv_size >= 64 &&
session->security_parameters.max_user_record_recv_size <=
DEFAULT_MAX_RECORD_SIZE);
send_size = session->security_parameters.max_user_record_recv_size;
if (session->security_parameters.entity == GNUTLS_SERVER) {
const version_entry_st *vers;
/* if we had received the extension and rejected, don't send it */
if (session->internals.hsk_flags &
HSK_RECORD_SIZE_LIMIT_RECEIVED &&
!(session->internals.hsk_flags &
HSK_RECORD_SIZE_LIMIT_NEGOTIATED))
return gnutls_assert_val(0);
/* add 1 octet for content type */
vers = get_version(session);
if (unlikely(vers == NULL))
return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
session->security_parameters.max_record_recv_size = send_size;
send_size += vers->tls13_sem;
} else {
const version_entry_st *vers;
/* add 1 octet for content type */
vers = _gnutls_version_max(session);
if (unlikely(vers == NULL))
return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
send_size += vers->tls13_sem;
}
ret = _gnutls_buffer_append_prefix(extdata, 16, send_size);
if (ret < 0)
return gnutls_assert_val(ret);
session->internals.hsk_flags |= HSK_RECORD_SIZE_LIMIT_SENT;
return 2;
}
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