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/*
* Copyright (C) 2001-2012 Free Software Foundation, Inc.
* Copyright (C) 2017-2018 Red Hat, 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/supported_versions.h>
#include "handshake.h"
static int supported_versions_recv_params(gnutls_session_t session,
const uint8_t * data,
size_t data_size);
static int supported_versions_send_params(gnutls_session_t session,
gnutls_buffer_st * extdata);
const hello_ext_entry_st ext_mod_supported_versions = {
.name = "Supported Versions",
.tls_id = 43,
.gid = GNUTLS_EXTENSION_SUPPORTED_VERSIONS,
.validity = GNUTLS_EXT_FLAG_CLIENT_HELLO | GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO |
GNUTLS_EXT_FLAG_TLS13_SERVER_HELLO | GNUTLS_EXT_FLAG_HRR|GNUTLS_EXT_FLAG_TLS,
.client_parse_point = GNUTLS_EXT_VERSION_NEG, /* force parsing prior to EXT_TLS extensions */
.server_parse_point = GNUTLS_EXT_VERSION_NEG,
.recv_func = supported_versions_recv_params,
.send_func = supported_versions_send_params,
.pack_func = NULL,
.unpack_func = NULL,
.deinit_func = NULL,
.cannot_be_overriden = 1
};
static int
supported_versions_recv_params(gnutls_session_t session,
const uint8_t * data, size_t data_size)
{
const version_entry_st *vers;
uint8_t major, minor;
size_t bytes;
int ret;
if (session->security_parameters.entity == GNUTLS_SERVER) {
const version_entry_st *old_vers;
const version_entry_st *cli_vers = NULL;
vers = _gnutls_version_max(session);
old_vers = get_version(session);
/* do not parse this extension when we haven't TLS1.3
* enabled. That is because we cannot handle earlier protocol
* negotiation (such as SSL3.0) with this */
if (vers && !vers->tls13_sem)
return 0;
DECR_LEN(data_size, 1);
bytes = data[0];
data++;
if (bytes % 2 == 1)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
DECR_LEN(data_size, bytes);
if (data_size != 0)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
while (bytes > 0) {
major = data[0];
minor = data[1];
data += 2;
bytes -= 2;
_gnutls_handshake_log("EXT[%p]: Found version: %d.%d\n",
session, (int)major, (int)minor);
if (!_gnutls_nversion_is_supported(session, major, minor))
continue;
/* Prefer the latest possible version
* regardless of the client's precedence. See
* https://gitlab.com/gnutls/gnutls/issues/837
* for the rationale.
*/
if (!cli_vers ||
major > cli_vers->major ||
(major == cli_vers->major &&
minor > cli_vers->minor))
cli_vers = nversion_to_entry(major, minor);
}
if (!cli_vers)
return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
session->security_parameters.pversion = cli_vers;
_gnutls_handshake_log("EXT[%p]: Negotiated version: %d.%d\n",
session,
(int)cli_vers->major,
(int)cli_vers->minor);
if (old_vers != cli_vers) {
/* regenerate the random value to set
* downgrade sentinel if necessary
*/
ret = _gnutls_gen_server_random(session, cli_vers->id);
if (ret < 0)
return gnutls_assert_val(ret);
}
return 0;
} else { /* client */
if (!have_creds_for_tls13(session)) {
/* if we don't have certificate or PSK (which work under TLS1.3)
* don't try to negotiate version using the extension. We fallback
* instead to the normal TLS negotiation which has a cap on TLS1.2.
*/
return 0;
}
DECR_LEN(data_size, 2);
if (data_size != 0)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
major = data[0];
minor = data[1];
vers = nversion_to_entry(major, minor);
if (!vers)
return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
set_adv_version(session, major, minor);
_gnutls_handshake_log("EXT[%p]: Negotiated version: %d.%d\n",
session, (int)major, (int)minor);
if (!vers->tls13_sem)
return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
ret = _gnutls_negotiate_version(session, major, minor, 1);
if (ret < 0) {
gnutls_assert();
return ret;
}
}
return 0;
}
/* returns data_size or a negative number on failure
*/
static int
supported_versions_send_params(gnutls_session_t session,
gnutls_buffer_st * extdata)
{
uint8_t versions[32];
size_t versions_size;
const version_entry_st *vers;
int ret;
/* this function sends the client extension data (dnsname) */
if (session->security_parameters.entity == GNUTLS_CLIENT) {
vers = _gnutls_version_max(session);
/* Do not advertise this extension if we are not doing certificate
* or PSK authentication; i.e., do not try to do TLS1.3 if we have
* credentials which do not fit it. */
if (!have_creds_for_tls13(session)) {
/* if we don't have certificate or PSK (which work under TLS1.3)
* don't try to negotiate version using the extension. We fallback
* instead to the normal TLS negotiation which has a cap on TLS1.2.
*/
return 0;
}
/* do not advertise this extension when we haven't TLS1.3
* enabled. */
if (vers && !vers->tls13_sem)
return 0;
ret = _gnutls_write_supported_versions(session, versions, sizeof(versions));
if (ret <= 0) /* if this function doesn't succeed do not send anything */
return 0;
versions_size = ret;
ret = _gnutls_buffer_append_data_prefix(extdata, 8, versions, versions_size);
if (ret < 0)
return gnutls_assert_val(ret);
return versions_size+2;
} else {
vers = get_version(session);
if (unlikely(vers == NULL))
return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
/* don't use this extension to negotiate versions <= 1.2,
* pretend we don't support it, so that we use a single
* code path to negotiate these protocols. */
if (!vers->tls13_sem)
return 0;
ret = _gnutls_buffer_append_data(extdata, &vers->major, 1);
if (ret < 0)
return gnutls_assert_val(ret);
ret = _gnutls_buffer_append_data(extdata, &vers->minor, 1);
if (ret < 0)
return gnutls_assert_val(ret);
return 2;
}
return 0;
}
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