/*
* Copyright (C) 2002-2012 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
*
*/
/* This file contains common stuff in Ephemeral Diffie-Hellman (DHE)
* and Anonymous DH key exchange(DHA). These are used in the handshake
* procedure of the certificate and anonymous authentication.
*/
#include "gnutls_int.h"
#include "auth.h"
#include "errors.h"
#include "dh.h"
#include "num.h"
#include "tls-sig.h"
#include
#include
#include
#include
#include
#include
#include
#if defined(ENABLE_DHE) || defined(ENABLE_ANON)
/* Frees the dh_info_st structure.
*/
void _gnutls_free_dh_info(dh_info_st * dh)
{
dh->secret_bits = 0;
_gnutls_free_datum(&dh->prime);
_gnutls_free_datum(&dh->generator);
_gnutls_free_datum(&dh->public_key);
}
int
_gnutls_proc_dh_common_client_kx(gnutls_session_t session,
uint8_t * data, size_t _data_size,
gnutls_datum_t * psk_key)
{
uint16_t n_Y;
size_t _n_Y;
int ret;
ssize_t data_size = _data_size;
gnutls_datum_t tmp_dh_key = {NULL, 0};
gnutls_pk_params_st peer_pub;
gnutls_pk_params_init(&peer_pub);
DECR_LEN(data_size, 2);
n_Y = _gnutls_read_uint16(&data[0]);
_n_Y = n_Y;
DECR_LEN(data_size, n_Y);
if (data_size != 0)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
if (_gnutls_mpi_init_scan_nz(&session->key.proto.tls12.dh.client_Y, &data[2], _n_Y)) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER; /* most likely zero or illegal size */
}
_gnutls_dh_set_peer_public(session, session->key.proto.tls12.dh.client_Y);
peer_pub.params[DH_Y] = session->key.proto.tls12.dh.client_Y;
/* calculate the key after calculating the message */
ret = _gnutls_pk_derive(GNUTLS_PK_DH, &tmp_dh_key, &session->key.proto.tls12.dh.params, &peer_pub);
if (ret < 0) {
gnutls_assert();
goto error;
}
if (psk_key == NULL) {
session->key.key.data = tmp_dh_key.data;
session->key.key.size = tmp_dh_key.size;
} else { /* In DHE_PSK the key is set differently */
ret =
_gnutls_set_psk_session_key(session, psk_key,
&tmp_dh_key);
_gnutls_free_temp_key_datum(&tmp_dh_key);
}
if (ret < 0) {
gnutls_assert();
goto error;
}
ret = 0;
error:
_gnutls_mpi_release(&session->key.proto.tls12.dh.client_Y);
gnutls_pk_params_clear(&session->key.proto.tls12.dh.params);
return ret;
}
int _gnutls_gen_dh_common_client_kx(gnutls_session_t session,
gnutls_buffer_st * data)
{
return _gnutls_gen_dh_common_client_kx_int(session, data, NULL);
}
int
_gnutls_gen_dh_common_client_kx_int(gnutls_session_t session,
gnutls_buffer_st * data,
gnutls_datum_t * pskkey)
{
int ret;
gnutls_pk_params_st peer_pub;
gnutls_datum_t tmp_dh_key = {NULL, 0};
unsigned init_pos = data->length;
gnutls_pk_params_init(&peer_pub);
ret =
_gnutls_pk_generate_keys(GNUTLS_PK_DH, 0,
&session->key.proto.tls12.dh.params, 1);
if (ret < 0)
return gnutls_assert_val(ret);
_gnutls_dh_set_secret_bits(session, _gnutls_mpi_get_nbits(session->key.proto.tls12.dh.params.params[DH_X]));
ret = _gnutls_buffer_append_mpi(data, 16, session->key.proto.tls12.dh.params.params[DH_Y], 0);
if (ret < 0) {
gnutls_assert();
goto error;
}
peer_pub.params[DH_Y] = session->key.proto.tls12.dh.client_Y;
/* calculate the key after calculating the message */
ret = _gnutls_pk_derive(GNUTLS_PK_DH, &tmp_dh_key, &session->key.proto.tls12.dh.params, &peer_pub);
if (ret < 0) {
gnutls_assert();
goto error;
}
if (session->security_parameters.cs->kx_algorithm != GNUTLS_KX_DHE_PSK) {
session->key.key.data = tmp_dh_key.data;
session->key.key.size = tmp_dh_key.size;
} else { /* In DHE_PSK the key is set differently */
ret =
_gnutls_set_psk_session_key(session, pskkey,
&tmp_dh_key);
_gnutls_free_temp_key_datum(&tmp_dh_key);
}
if (ret < 0) {
gnutls_assert();
goto error;
}
ret = data->length - init_pos;
error:
gnutls_pk_params_clear(&session->key.proto.tls12.dh.params);
return ret;
}
/* Returns the bytes parsed */
int
_gnutls_proc_dh_common_server_kx(gnutls_session_t session,
uint8_t * data, size_t _data_size)
{
uint16_t n_Y, n_g, n_p;
size_t _n_Y, _n_g, _n_p, _n_q;
uint8_t *data_p;
uint8_t *data_g;
uint8_t *data_Y;
uint8_t *data_q = NULL;
int i, bits, ret, p_bits;
unsigned j;
ssize_t data_size = _data_size;
/* just in case we are resuming a session */
gnutls_pk_params_release(&session->key.proto.tls12.dh.params);
gnutls_pk_params_init(&session->key.proto.tls12.dh.params);
i = 0;
DECR_LEN(data_size, 2);
n_p = _gnutls_read_uint16(&data[i]);
i += 2;
DECR_LEN(data_size, n_p);
data_p = &data[i];
i += n_p;
DECR_LEN(data_size, 2);
n_g = _gnutls_read_uint16(&data[i]);
i += 2;
DECR_LEN(data_size, n_g);
data_g = &data[i];
i += n_g;
DECR_LEN(data_size, 2);
n_Y = _gnutls_read_uint16(&data[i]);
i += 2;
DECR_LEN(data_size, n_Y);
data_Y = &data[i];
_n_Y = n_Y;
_n_g = n_g;
_n_p = n_p;
if (_gnutls_mpi_init_scan_nz(&session->key.proto.tls12.dh.client_Y, data_Y, _n_Y) != 0) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
/* if we are doing RFC7919 */
if (session->internals.priorities->groups.have_ffdhe != 0) {
/* verify whether the received parameters match the advertised, otherwise
* log that. */
for (j=0;jinternals.priorities->groups.size;j++) {
if (session->internals.priorities->groups.entry[j]->generator &&
session->internals.priorities->groups.entry[j]->generator->size == n_g &&
session->internals.priorities->groups.entry[j]->prime->size == n_p &&
memcmp(session->internals.priorities->groups.entry[j]->generator->data,
data_g, n_g) == 0 &&
memcmp(session->internals.priorities->groups.entry[j]->prime->data,
data_p, n_p) == 0) {
session->internals.hsk_flags |= HSK_USED_FFDHE;
_gnutls_session_group_set(session, session->internals.priorities->groups.entry[j]);
session->key.proto.tls12.dh.params.qbits = *session->internals.priorities->groups.entry[j]->q_bits;
data_q = session->internals.priorities->groups.entry[j]->q->data;
_n_q = session->internals.priorities->groups.entry[j]->q->size;
break;
}
}
if (!(session->internals.hsk_flags & HSK_USED_FFDHE)) {
_gnutls_audit_log(session, "FFDHE groups advertised, but server didn't support it; falling back to server's choice\n");
}
}
#ifdef ENABLE_FIPS140
if (gnutls_fips140_mode_enabled() &&
!_gnutls_dh_prime_match_fips_approved(data_p, n_p, data_g, n_g, NULL, NULL)) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
#endif
if (_gnutls_mpi_init_scan_nz(&session->key.proto.tls12.dh.params.params[DH_G], data_g, _n_g) != 0) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
if (_gnutls_mpi_init_scan_nz(&session->key.proto.tls12.dh.params.params[DH_P], data_p, _n_p) != 0) {
gnutls_assert();
/* we release now because session->key.proto.tls12.dh.params.params_nr is not yet set */
_gnutls_mpi_release(&session->key.proto.tls12.dh.params.params[DH_G]);
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
if (data_q && _gnutls_mpi_init_scan_nz(
&session->key.proto.tls12.dh.params.params[DH_Q],
data_q, _n_q) != 0) {
/* we release now because params_nr is not yet set */
_gnutls_mpi_release(
&session->key.proto.tls12.dh.params.params[DH_P]);
_gnutls_mpi_release(
&session->key.proto.tls12.dh.params.params[DH_G]);
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
/* include, possibly empty, q */
session->key.proto.tls12.dh.params.params_nr = 3;
session->key.proto.tls12.dh.params.algo = GNUTLS_PK_DH;
if (!(session->internals.hsk_flags & HSK_USED_FFDHE)) {
bits = _gnutls_dh_get_min_prime_bits(session);
if (bits < 0) {
gnutls_assert();
return bits;
}
p_bits = _gnutls_mpi_get_nbits(session->key.proto.tls12.dh.params.params[DH_P]);
if (p_bits < bits) {
/* the prime used by the peer is not acceptable
*/
gnutls_assert();
_gnutls_debug_log
("Received a prime of %u bits, limit is %u\n",
(unsigned) _gnutls_mpi_get_nbits(session->key.proto.tls12.dh.params.params[DH_P]),
(unsigned) bits);
return GNUTLS_E_DH_PRIME_UNACCEPTABLE;
}
if (p_bits >= DEFAULT_MAX_VERIFY_BITS) {
gnutls_assert();
_gnutls_debug_log
("Received a prime of %u bits, limit is %u\n",
(unsigned) p_bits,
(unsigned) DEFAULT_MAX_VERIFY_BITS);
return GNUTLS_E_DH_PRIME_UNACCEPTABLE;
}
}
_gnutls_dh_save_group(session, session->key.proto.tls12.dh.params.params[DH_G],
session->key.proto.tls12.dh.params.params[DH_P]);
_gnutls_dh_set_peer_public(session, session->key.proto.tls12.dh.client_Y);
ret = n_Y + n_p + n_g + 6;
return ret;
}
int
_gnutls_dh_common_print_server_kx(gnutls_session_t session,
gnutls_buffer_st * data)
{
int ret;
unsigned q_bits = session->key.proto.tls12.dh.params.qbits;
unsigned init_pos = data->length;
if (q_bits < 192 && q_bits != 0) {
gnutls_assert();
_gnutls_debug_log("too small q_bits value for DH: %u\n", q_bits);
q_bits = 0; /* auto-detect */
}
/* Y=g^x mod p */
ret =
_gnutls_pk_generate_keys(GNUTLS_PK_DH, q_bits,
&session->key.proto.tls12.dh.params, 1);
if (ret < 0)
return gnutls_assert_val(ret);
_gnutls_dh_set_secret_bits(session, _gnutls_mpi_get_nbits(session->key.proto.tls12.dh.params.params[DH_X]));
ret = _gnutls_buffer_append_mpi(data, 16, session->key.proto.tls12.dh.params.params[DH_P], 0);
if (ret < 0) {
gnutls_assert();
goto cleanup;
}
ret = _gnutls_buffer_append_mpi(data, 16, session->key.proto.tls12.dh.params.params[DH_G], 0);
if (ret < 0) {
gnutls_assert();
goto cleanup;
}
ret = _gnutls_buffer_append_mpi(data, 16, session->key.proto.tls12.dh.params.params[DH_Y], 0);
if (ret < 0) {
gnutls_assert();
goto cleanup;
}
ret = data->length - init_pos;
cleanup:
return ret;
}
#endif