/*
 * Copyright (C) 2011-2012 Free Software Foundation, Inc.
 * Copyright (C) 2017 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 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 "state.h"
#include "datum.h"
#include "x509.h"
#include "auth/ecdhe.h"
#include "ecc.h"
#include "ext/supported_groups.h"
#include "algorithms.h"
#include "auth/psk.h"
#include "auth/cert.h"
#include "pk.h"

static int gen_ecdhe_server_kx(gnutls_session_t, gnutls_buffer_st *);
static int proc_ecdhe_server_kx(gnutls_session_t session, uint8_t *data,
				size_t _data_size);
static int proc_ecdhe_client_kx(gnutls_session_t session, uint8_t *data,
				size_t _data_size);

#if defined(ENABLE_ECDHE)
const mod_auth_st ecdhe_ecdsa_auth_struct = {
	"ECDHE_ECDSA",
	_gnutls_gen_cert_server_crt,
	_gnutls_gen_cert_client_crt,
	gen_ecdhe_server_kx,
	_gnutls_gen_ecdh_common_client_kx, /* This is the only difference */
	_gnutls_gen_cert_client_crt_vrfy,
	_gnutls_gen_cert_server_cert_req,

	_gnutls_proc_crt,
	_gnutls_proc_crt,
	proc_ecdhe_server_kx,
	proc_ecdhe_client_kx,
	_gnutls_proc_cert_client_crt_vrfy,
	_gnutls_proc_cert_cert_req
};

const mod_auth_st ecdhe_rsa_auth_struct = {
	"ECDHE_RSA",
	_gnutls_gen_cert_server_crt,
	_gnutls_gen_cert_client_crt,
	gen_ecdhe_server_kx,
	_gnutls_gen_ecdh_common_client_kx, /* This is the only difference */
	_gnutls_gen_cert_client_crt_vrfy,
	_gnutls_gen_cert_server_cert_req,

	_gnutls_proc_crt,
	_gnutls_proc_crt,
	proc_ecdhe_server_kx,
	proc_ecdhe_client_kx,
	_gnutls_proc_cert_client_crt_vrfy,
	_gnutls_proc_cert_cert_req
};

static int calc_ecdh_key(gnutls_session_t session, gnutls_datum_t *psk_key,
			 const gnutls_ecc_curve_entry_st *ecurve)
{
	gnutls_pk_params_st pub;
	int ret;
	gnutls_datum_t tmp_dh_key;

	gnutls_pk_params_init(&pub);
	pub.params[ECC_X] = session->key.proto.tls12.ecdh.x;
	pub.params[ECC_Y] = session->key.proto.tls12.ecdh.y;
	pub.raw_pub.data = session->key.proto.tls12.ecdh.raw.data;
	pub.raw_pub.size = session->key.proto.tls12.ecdh.raw.size;
	pub.curve = ecurve->id;

	ret = _gnutls_pk_derive(ecurve->pk, &tmp_dh_key,
				&session->key.proto.tls12.ecdh.params, &pub);
	if (ret < 0) {
		ret = gnutls_assert_val(ret);
		goto cleanup;
	}

	if (psk_key == NULL) {
		memcpy(&session->key.key, &tmp_dh_key, sizeof(gnutls_datum_t));
		tmp_dh_key.data = NULL; /* no longer needed */
	} else {
		ret = _gnutls_set_psk_session_key(session, psk_key,
						  &tmp_dh_key);
		_gnutls_free_key_datum(&tmp_dh_key);

		if (ret < 0) {
			ret = gnutls_assert_val(ret);
			goto cleanup;
		}
	}

	ret = 0;

cleanup:
	/* no longer needed */
	_gnutls_mpi_release(&session->key.proto.tls12.ecdh.x);
	_gnutls_mpi_release(&session->key.proto.tls12.ecdh.y);
	_gnutls_free_datum(&session->key.proto.tls12.ecdh.raw);
	gnutls_pk_params_release(&session->key.proto.tls12.ecdh.params);
	return ret;
}

int _gnutls_proc_ecdh_common_client_kx(
	gnutls_session_t session, uint8_t *data, size_t _data_size,
	const struct gnutls_group_entry_st *group, gnutls_datum_t *psk_key)
{
	ssize_t data_size = _data_size;
	int ret, i = 0;
	unsigned point_size;
	const gnutls_ecc_curve_entry_st *ecurve;

	if (group == NULL)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	ecurve = _gnutls_ecc_curve_get_params(group->curve);
	if (ecurve == NULL)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	DECR_LEN(data_size, 1);
	point_size = data[i];
	i += 1;

	if (point_size == 0) {
		ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
		goto cleanup;
	}

	DECR_LEN(data_size, point_size);

	if (ecurve->pk == GNUTLS_PK_EC) {
		ret = _gnutls_ecc_ansi_x962_import(
			&data[i], point_size, &session->key.proto.tls12.ecdh.x,
			&session->key.proto.tls12.ecdh.y);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}
	} else if (ecurve->pk == GNUTLS_PK_ECDH_X25519 ||
		   ecurve->pk == GNUTLS_PK_ECDH_X448) {
		if (ecurve->size != point_size)
			return gnutls_assert_val(
				GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

		ret = _gnutls_set_datum(&session->key.proto.tls12.ecdh.raw,
					&data[i], point_size);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}

		/* RFC7748 requires to mask the MSB in the final byte
		 * for X25519 (not X448) */
		if (ecurve->id == GNUTLS_ECC_CURVE_X25519) {
			session->key.proto.tls12.ecdh.raw.data[point_size - 1] &=
				0x7f;
		}
	} else {
		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
	}

	if (data_size != 0) {
		ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
		goto cleanup;
	}

	/* generate pre-shared key */
	ret = calc_ecdh_key(session, psk_key, ecurve);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}
cleanup:
	_gnutls_mpi_release(&session->key.proto.tls12.ecdh.x);
	_gnutls_mpi_release(&session->key.proto.tls12.ecdh.y);
	_gnutls_free_datum(&session->key.proto.tls12.ecdh.raw);
	gnutls_pk_params_clear(&session->key.proto.tls12.ecdh.params);
	return ret;
}

static int proc_ecdhe_client_kx(gnutls_session_t session, uint8_t *data,
				size_t _data_size)
{
	gnutls_certificate_credentials_t cred;

	cred = (gnutls_certificate_credentials_t)_gnutls_get_cred(
		session, GNUTLS_CRD_CERTIFICATE);
	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	return _gnutls_proc_ecdh_common_client_kx(session, data, _data_size,
						  get_group(session), NULL);
}

int _gnutls_gen_ecdh_common_client_kx(gnutls_session_t session,
				      gnutls_buffer_st *data)
{
	return _gnutls_gen_ecdh_common_client_kx_int(session, data, NULL);
}

int _gnutls_gen_ecdh_common_client_kx_int(gnutls_session_t session,
					  gnutls_buffer_st *data,
					  gnutls_datum_t *psk_key)
{
	int ret;
	gnutls_datum_t out;
	const gnutls_group_entry_st *group = get_group(session);
	const gnutls_ecc_curve_entry_st *ecurve;
	int pk;
	unsigned init_pos = data->length;

	if (group == NULL)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	ecurve = _gnutls_ecc_curve_get_params(group->curve);
	if (ecurve == NULL)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	pk = ecurve->pk;

	/* generate temporal key */
	ret = _gnutls_pk_generate_keys(
		pk, ecurve->id, &session->key.proto.tls12.ecdh.params, 1);
	if (ret < 0)
		return gnutls_assert_val(ret);

	if (pk == GNUTLS_PK_EC) {
		ret = _gnutls_ecc_ansi_x962_export(
			ecurve->id,
			session->key.proto.tls12.ecdh.params
				.params[ECC_X] /* x */,
			session->key.proto.tls12.ecdh.params
				.params[ECC_Y] /* y */,
			&out);

		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}

		ret = _gnutls_buffer_append_data_prefix(data, 8, out.data,
							out.size);

		_gnutls_free_datum(&out);

		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}
	} else if (pk == GNUTLS_PK_ECDH_X25519 || pk == GNUTLS_PK_ECDH_X448) {
		ret = _gnutls_buffer_append_data_prefix(
			data, 8,
			session->key.proto.tls12.ecdh.params.raw_pub.data,
			session->key.proto.tls12.ecdh.params.raw_pub.size);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}
	}

	/* generate pre-shared key */
	ret = calc_ecdh_key(session, psk_key, ecurve);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	ret = data->length - init_pos;
cleanup:
	gnutls_pk_params_clear(&session->key.proto.tls12.ecdh.params);
	return ret;
}

static int proc_ecdhe_server_kx(gnutls_session_t session, uint8_t *data,
				size_t _data_size)
{
	int ret;
	gnutls_datum_t vparams;

	ret = _gnutls_proc_ecdh_common_server_kx(session, data, _data_size);
	if (ret < 0)
		return gnutls_assert_val(ret);

	vparams.data = data;
	vparams.size = ret;

	return _gnutls_proc_dhe_signature(session, data + ret, _data_size - ret,
					  &vparams);
}

int _gnutls_proc_ecdh_common_server_kx(gnutls_session_t session, uint8_t *data,
				       size_t _data_size)
{
	int i, ret;
	unsigned point_size;
	const gnutls_group_entry_st *group;
	ssize_t data_size = _data_size;
	const gnutls_ecc_curve_entry_st *ecurve;

	/* just in case we are resuming a session */
	gnutls_pk_params_release(&session->key.proto.tls12.ecdh.params);

	gnutls_pk_params_init(&session->key.proto.tls12.ecdh.params);

	i = 0;
	DECR_LEN(data_size, 1);
	if (data[i++] != 3)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	DECR_LEN(data_size, 2);

	group = _gnutls_tls_id_to_group(_gnutls_read_uint16(&data[i]));
	if (group == NULL || group->curve == 0) {
		_gnutls_debug_log("received unknown curve %u.%u\n",
				  (unsigned)data[i], (unsigned)data[i + 1]);
		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
	} else {
		_gnutls_debug_log("received curve %s\n", group->name);
	}

	i += 2;

	if (!_gnutls_session_supports_group(session, group->id))
		return gnutls_assert_val(GNUTLS_E_ECC_UNSUPPORTED_CURVE);

	ecurve = _gnutls_ecc_curve_get_params(group->curve);
	if (ecurve == NULL) {
		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
	}

	_gnutls_session_group_set(session, group);

	DECR_LEN(data_size, 1);
	point_size = data[i];
	i++;

	DECR_LEN(data_size, point_size);

	if (ecurve->pk == GNUTLS_PK_EC) {
		ret = _gnutls_ecc_ansi_x962_import(
			&data[i], point_size, &session->key.proto.tls12.ecdh.x,
			&session->key.proto.tls12.ecdh.y);
		if (ret < 0)
			return gnutls_assert_val(ret);

	} else if (ecurve->pk == GNUTLS_PK_ECDH_X25519 ||
		   ecurve->pk == GNUTLS_PK_ECDH_X448) {
		if (ecurve->size != point_size)
			return gnutls_assert_val(
				GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

		ret = _gnutls_set_datum(&session->key.proto.tls12.ecdh.raw,
					&data[i], point_size);
		if (ret < 0)
			return gnutls_assert_val(ret);

		/* RFC7748 requires to mask the MSB in the final byte
		 * for X25519 (not X448) */
		if (ecurve->id == GNUTLS_ECC_CURVE_X25519) {
			session->key.proto.tls12.ecdh.raw.data[point_size - 1] &=
				0x7f;
		}
	} else {
		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
	}

	i += point_size;

	return i;
}

/* If the psk flag is set, then an empty psk_identity_hint will
 * be inserted */
int _gnutls_ecdh_common_print_server_kx(gnutls_session_t session,
					gnutls_buffer_st *data,
					const gnutls_group_entry_st *group)
{
	uint8_t p;
	int ret;
	gnutls_datum_t out;
	unsigned init_pos = data->length;

	if (group == NULL || group->curve == 0)
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);

	/* just in case we are resuming a session */
	gnutls_pk_params_release(&session->key.proto.tls12.ecdh.params);

	gnutls_pk_params_init(&session->key.proto.tls12.ecdh.params);

	/* curve type */
	p = 3;

	ret = _gnutls_buffer_append_data(data, &p, 1);
	if (ret < 0)
		return gnutls_assert_val(ret);

	ret = _gnutls_buffer_append_prefix(data, 16, group->tls_id);
	if (ret < 0)
		return gnutls_assert_val(ret);

	/* generate temporal key */
	ret = _gnutls_pk_generate_keys(group->pk, group->curve,
				       &session->key.proto.tls12.ecdh.params,
				       1);
	if (ret < 0)
		return gnutls_assert_val(ret);

	if (group->pk == GNUTLS_PK_EC) {
		ret = _gnutls_ecc_ansi_x962_export(
			group->curve,
			session->key.proto.tls12.ecdh.params
				.params[ECC_X] /* x */,
			session->key.proto.tls12.ecdh.params
				.params[ECC_Y] /* y */,
			&out);
		if (ret < 0)
			return gnutls_assert_val(ret);

		ret = _gnutls_buffer_append_data_prefix(data, 8, out.data,
							out.size);

		_gnutls_free_datum(&out);

		if (ret < 0)
			return gnutls_assert_val(ret);

	} else if (group->pk == GNUTLS_PK_ECDH_X25519 ||
		   group->pk == GNUTLS_PK_ECDH_X448) {
		ret = _gnutls_buffer_append_data_prefix(
			data, 8,
			session->key.proto.tls12.ecdh.params.raw_pub.data,
			session->key.proto.tls12.ecdh.params.raw_pub.size);
		if (ret < 0)
			return gnutls_assert_val(ret);
	} else {
		return gnutls_assert_val(GNUTLS_E_ECC_NO_SUPPORTED_CURVES);
	}

	return data->length - init_pos;
}

static int gen_ecdhe_server_kx(gnutls_session_t session, gnutls_buffer_st *data)
{
	int ret = 0;
	gnutls_certificate_credentials_t cred;
	unsigned sig_pos;

	cred = (gnutls_certificate_credentials_t)_gnutls_get_cred(
		session, GNUTLS_CRD_CERTIFICATE);
	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	if ((ret = _gnutls_auth_info_init(session, GNUTLS_CRD_CERTIFICATE,
					  sizeof(cert_auth_info_st), 1)) < 0) {
		gnutls_assert();
		return ret;
	}

	sig_pos = data->length;

	ret = _gnutls_ecdh_common_print_server_kx(session, data,
						  get_group(session));
	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	/* Generate the signature. */
	return _gnutls_gen_dhe_signature(session, data, &data->data[sig_pos],
					 data->length - sig_pos);
}

#endif