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/*
* Copyright (C) 2017 Free Software Foundation, Inc.
*
* Author: Ander Juaristi
*
* 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 <http://www.gnu.org/licenses/>
*
*/
#include "gnutls_int.h"
#include "ext/psk_ke_modes.h"
#include "ext/pre_shared_key.h"
#include <assert.h>
static void get_server_kx_algo_order(gnutls_session_t session, int *psk_pos, int *dhpsk_pos)
{
unsigned i;
*psk_pos = INT_MAX;
*dhpsk_pos = INT_MAX;
for (i = 0; i < session->internals.priorities->_kx.algorithms; i++) {
if (session->internals.priorities->_kx.priority[i] == GNUTLS_KX_PSK &&
*psk_pos == INT_MAX)
*psk_pos = i;
else if ((session->internals.priorities->_kx.priority[i] == GNUTLS_KX_DHE_PSK ||
session->internals.priorities->_kx.priority[i] == GNUTLS_KX_ECDHE_PSK) &&
*dhpsk_pos == INT_MAX)
*dhpsk_pos = i;
if (*psk_pos != INT_MAX && *dhpsk_pos != INT_MAX)
break;
}
}
static void get_client_kx_algo_order(gnutls_session_t session, int *psk_pos, int *dhpsk_pos)
{
*dhpsk_pos = INT_MAX;
*psk_pos = INT_MAX;
for (unsigned i = 0; i < session->internals.psk_ke_modes_size; i++) {
if (session->internals.psk_ke_modes[i] == PSK_DHE_KE)
*dhpsk_pos = i;
else if (session->internals.psk_ke_modes[i] == PSK_KE)
*psk_pos = i;
}
}
static int check_ke_modes(gnutls_session_t session)
{
int mode = -1;
int psk_pos, dhpsk_pos;
int cli_psk_pos, cli_dhpsk_pos;
get_server_kx_algo_order(session, &psk_pos, &dhpsk_pos);
get_client_kx_algo_order(session, &cli_psk_pos, &cli_dhpsk_pos);
if (session->internals.priorities->server_precedence) {
if (dhpsk_pos != INT_MAX && cli_dhpsk_pos != INT_MAX && dhpsk_pos < psk_pos)
mode = PSK_DHE_KE;
else if (psk_pos != INT_MAX && cli_psk_pos != INT_MAX && psk_pos < dhpsk_pos)
mode = PSK_KE;
} else {
if (dhpsk_pos != INT_MAX && cli_dhpsk_pos != INT_MAX && cli_dhpsk_pos < cli_psk_pos)
mode = PSK_DHE_KE;
else if (psk_pos != INT_MAX && cli_psk_pos != INT_MAX && cli_psk_pos < cli_dhpsk_pos)
mode = PSK_KE;
}
return mode;
}
static int make_data(gnutls_session_t session, uint8_t data[2])
{
int pos = 0;
unsigned have_dhpsk = 0;
unsigned have_psk = 0;
for (unsigned i = 0; i < session->internals.priorities->_kx.algorithms; i++) {
if (session->internals.priorities->_kx.priority[i] == GNUTLS_KX_PSK && !have_psk) {
assert(pos <= 1);
data[pos++] = PSK_KE;
session->internals.hsk_flags |= HSK_PSK_KE_MODE_PSK;
have_psk = 1;
} else if ((session->internals.priorities->_kx.priority[i] == GNUTLS_KX_DHE_PSK ||
session->internals.priorities->_kx.priority[i] == GNUTLS_KX_ECDHE_PSK) && !have_dhpsk) {
assert(pos <= 1);
data[pos++] = PSK_DHE_KE;
session->internals.hsk_flags |= HSK_PSK_KE_MODE_DHE_PSK;
have_dhpsk = 1;
}
if (have_psk && have_dhpsk)
break;
}
return pos;
}
static int
psk_ke_modes_send_params(gnutls_session_t session,
gnutls_buffer_t extdata)
{
int ret;
gnutls_psk_client_credentials_t cred;
const version_entry_st *vers;
uint8_t data[2];
unsigned pos;
/* Server doesn't send psk_key_exchange_modes */
if (session->security_parameters.entity == GNUTLS_SERVER)
return 0;
vers = _gnutls_version_max(session);
if (!vers || !vers->tls13_sem)
return 0;
cred = (gnutls_psk_client_credentials_t)
_gnutls_get_cred(session, GNUTLS_CRD_PSK);
if (cred == NULL || _gnutls_have_psk_credentials(cred) == 0) {
/* No out-of-band PSKs - do we have a session ticket? */
if (!session->internals.session_ticket_enable ||
session->internals.tls13_ticket.ticket.data == NULL)
return 0;
} else {
if (!session->internals.priorities->have_psk)
return 0;
}
pos = make_data(session, data);
if (pos > 0) {
ret = _gnutls_buffer_append_data_prefix(extdata, 8, data, pos);
if (ret < 0)
return gnutls_assert_val(ret);
session->internals.hsk_flags |= HSK_PSK_KE_MODES_SENT;
}
return 0;
}
static int
psk_ke_modes_recv_params(gnutls_session_t session,
const unsigned char *data, size_t _len)
{
uint8_t ke_modes_len;
ssize_t len = _len;
const version_entry_st *vers = get_version(session);
int selected_ke_modes[2];
unsigned have_dhpsk = 0;
unsigned have_psk = 0;
unsigned i, pos = 0;
/* Server doesn't send psk_key_exchange_modes */
if (session->security_parameters.entity == GNUTLS_CLIENT)
return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);
if (!vers || !vers->tls13_sem)
return 0;
DECR_LEN(len, 1);
ke_modes_len = *(data++);
for (i = 0; i < ke_modes_len; i++) {
DECR_LEN(len, 1);
switch (data[i]) {
case PSK_DHE_KE:
selected_ke_modes[pos++] = PSK_DHE_KE;
have_dhpsk = 1;
break;
case PSK_KE:
selected_ke_modes[pos++] = PSK_KE;
have_psk = 1;
break;
default:
session->internals.hsk_flags |= HSK_PSK_KE_MODE_INVALID;
return 0;
}
if (have_dhpsk && have_psk)
break;
}
for (i = 0; i < pos; i++)
session->internals.psk_ke_modes[i] = selected_ke_modes[i];
session->internals.psk_ke_modes_size = pos;
switch (check_ke_modes(session)) {
case PSK_DHE_KE:
session->internals.hsk_flags |= HSK_PSK_KE_MODE_DHE_PSK;
_gnutls_handshake_log("EXT[%p]: Selected DHE-PSK mode\n", session);
break;
case PSK_KE:
session->internals.hsk_flags |= HSK_PSK_KE_MODE_PSK;
_gnutls_handshake_log("EXT[%p]: Selected PSK mode\n", session);
break;
default:
return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
}
return 0;
}
const hello_ext_entry_st ext_psk_ke_modes = {
.name = "PSK Key Exchange Modes",
.tls_id = 45,
.gid = GNUTLS_EXTENSION_PSK_KE_MODES,
.parse_type = GNUTLS_EXT_TLS,
.validity = GNUTLS_EXT_FLAG_CLIENT_HELLO | GNUTLS_EXT_FLAG_TLS13_SERVER_HELLO,
.send_func = psk_ke_modes_send_params,
.recv_func = psk_ke_modes_recv_params
};
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