/*
* Copyright (C) 2001-2012 Free Software Foundation, Inc.
*
* Author: Nikos Mavrogiannopoulos
*
* 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 Max Record Size TLS extension.
*/
#include "gnutls_int.h"
#include "errors.h"
#include "num.h"
#include <hello_ext.h>
#include <ext/max_record.h>
static int _gnutls_max_record_recv_params(gnutls_session_t session,
const uint8_t * data,
size_t data_size);
static int _gnutls_max_record_send_params(gnutls_session_t session,
gnutls_buffer_st * extdata);
/* Maps record size to numbers according to the
* extensions draft.
*/
static int _gnutls_mre_num2record(int num);
static int _gnutls_mre_record2num(uint16_t record_size);
const hello_ext_entry_st ext_mod_max_record_size = {
.name = "Maximum Record Size",
.tls_id = 1,
.gid = GNUTLS_EXTENSION_MAX_RECORD_SIZE,
.parse_type = GNUTLS_EXT_TLS,
.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_max_record_recv_params,
.send_func = _gnutls_max_record_send_params
};
/*
* In case of a server: if a MAX_RECORD_SIZE extension type is received then it stores
* into the session the new value. The server may use gnutls_get_max_record_size(),
* in order to access it.
*
* In case of a client: If a different max record size (than the default) has
* been specified then it sends the extension.
*
*/
static int
_gnutls_max_record_recv_params(gnutls_session_t session,
const uint8_t * data, size_t data_size)
{
ssize_t new_size;
if (session->internals.hsk_flags & HSK_RECORD_SIZE_LIMIT_NEGOTIATED)
return 0;
if (session->security_parameters.entity == GNUTLS_SERVER) {
if (data_size > 0) {
DECR_LEN(data_size, 1);
new_size = _gnutls_mre_num2record(data[0]);
if (new_size < 0) {
gnutls_assert();
return new_size;
}
session->security_parameters.max_record_send_size =
new_size;
session->security_parameters.max_record_recv_size =
new_size;
}
} else { /* CLIENT SIDE - we must check if the sent record size is the right one
*/
if (data_size > 0) {
if (data_size != 1) {
gnutls_assert();
return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
}
new_size = _gnutls_mre_num2record(data[0]);
if (new_size < 0) {
gnutls_assert();
return new_size;
}
if (new_size != session->security_parameters.
max_user_record_send_size) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
} else {
session->security_parameters.
max_record_send_size = new_size;
session->security_parameters.
max_record_recv_size = new_size;
}
}
}
return 0;
}
/* returns data_size or a negative number on failure
*/
static int
_gnutls_max_record_send_params(gnutls_session_t session,
gnutls_buffer_st * extdata)
{
uint8_t p;
int ret;
/* this function sends the client extension data (dnsname) */
if (session->security_parameters.entity == GNUTLS_CLIENT) {
/* if the user limits for sending and receiving are
* different, that means the programmer had chosen to
* use record_size_limit instead */
if (session->security_parameters.max_user_record_send_size !=
session->security_parameters.max_user_record_recv_size)
return 0;
if (session->security_parameters.max_user_record_send_size !=
DEFAULT_MAX_RECORD_SIZE) {
ret = _gnutls_mre_record2num
(session->security_parameters.
max_user_record_send_size);
/* it's not an error, as long as we send the
* record_size_limit extension with that value */
if (ret < 0)
return 0;
p = (uint8_t) ret;
ret = _gnutls_buffer_append_data(extdata, &p, 1);
if (ret < 0)
return gnutls_assert_val(ret);
return 1;
}
} else { /* server side */
if (session->internals.hsk_flags & HSK_RECORD_SIZE_LIMIT_SENT)
return 0;
if (session->security_parameters.max_record_recv_size !=
DEFAULT_MAX_RECORD_SIZE) {
ret = _gnutls_mre_record2num
(session->security_parameters.
max_record_recv_size);
if (ret < 0)
return gnutls_assert_val(ret);
p = (uint8_t) ret;
ret = _gnutls_buffer_append_data(extdata, &p, 1);
if (ret < 0)
return gnutls_assert_val(ret);
return 1;
}
}
return 0;
}
/* Maps numbers to record sizes according to the
* extensions draft.
*/
static int _gnutls_mre_num2record(int num)
{
switch (num) {
case 1:
return 512;
case 2:
return 1024;
case 3:
return 2048;
case 4:
return 4096;
default:
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
}
/* Maps record size to numbers according to the
* extensions draft.
*/
static int _gnutls_mre_record2num(uint16_t record_size)
{
switch (record_size) {
case 512:
return 1;
case 1024:
return 2;
case 2048:
return 3;
case 4096:
return 4;
default:
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
}
/**
* gnutls_record_get_max_size:
* @session: is a #gnutls_session_t type.
*
* Get the record size. The maximum record size is negotiated by the
* client after the first handshake message.
*
* Returns: The maximum record packet size in this connection.
**/
size_t gnutls_record_get_max_size(gnutls_session_t session)
{
/* Recv will hold the negotiated max record size
* always.
*/
return session->security_parameters.max_record_recv_size;
}
/**
* gnutls_record_set_max_size:
* @session: is a #gnutls_session_t type.
* @size: is the new size
*
* This function sets the maximum amount of plaintext sent and
* received in a record in this connection.
*
* Prior to 3.6.4, this function was implemented using a TLS extension
* called 'max fragment length', which limits the acceptable values to
* 512(=2^9), 1024(=2^10), 2048(=2^11) and 4096(=2^12).
*
* Since 3.6.4, the limit is also negotiated through a new TLS
* extension called 'record size limit', which doesn't have the
* limitation, as long as the value ranges between 512 and 16384.
* Note that while the 'record size limit' extension is preferred, not
* all TLS implementations use or even understand the extension.
*
* Deprecated: if the client can assume that the 'record size limit'
* extension is supported by the server, we recommend using
* gnutls_record_set_max_recv_size() instead.
*
* Returns: On success, %GNUTLS_E_SUCCESS (0) is returned,
* otherwise a negative error code is returned.
**/
ssize_t gnutls_record_set_max_size(gnutls_session_t session, size_t size)
{
if (size < MIN_RECORD_SIZE || size > DEFAULT_MAX_RECORD_SIZE)
return GNUTLS_E_INVALID_REQUEST;
if (session->internals.handshake_in_progress)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
session->security_parameters.max_user_record_send_size = size;
session->security_parameters.max_user_record_recv_size = size;
return 0;
}
/**
* gnutls_record_set_max_recv_size:
* @session: is a #gnutls_session_t type.
* @size: is the new size
*
* This function sets the maximum amount of plaintext received in a
* record in this connection.
*
* The limit is also negotiated through a TLS extension called 'record
* size limit'. Note that while the 'record size limit' extension is
* preferred, not all TLS implementations use or even understand the
* extension.
*
* Returns: On success, %GNUTLS_E_SUCCESS (0) is returned,
* otherwise a negative error code is returned.
*
* Since: 3.6.8
**/
ssize_t gnutls_record_set_max_recv_size(gnutls_session_t session, size_t size)
{
if (size <
(session->internals.allow_small_records ?
MIN_RECORD_SIZE_SMALL : MIN_RECORD_SIZE) ||
size > DEFAULT_MAX_RECORD_SIZE)
return GNUTLS_E_INVALID_REQUEST;
if (session->internals.handshake_in_progress)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
session->security_parameters.max_user_record_recv_size = size;
return 0;
}