/*
 * 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 <http://www.gnu.org/licenses/>
 *
 */

/* Functions that relate to the TLS handshake procedure.
 */

#include "gnutls_int.h"
#include "errors.h"
#include "dh.h"
#include "debug.h"
#include "algorithms.h"
#include "cipher.h"
#include "buffers.h"
#include "mbuffers.h"
#include "kx.h"
#include "handshake.h"
#include "num.h"
#include "hash_int.h"
#include "db.h"
#include "hello_ext.h"
#include "supplemental.h"
#include "auth.h"
#include "sslv2_compat.h"
#include <auth/cert.h>
#include "constate.h"
#include <record.h>
#include <state.h>
#include <random.h>
#include <dtls.h>
#include "secrets.h"
#include "tls13/hello_retry.h"
#include "tls13/encrypted_extensions.h"
#include "tls13/certificate_request.h"
#include "tls13/certificate_verify.h"
#include "tls13/certificate.h"
#include "tls13/finished.h"
#include "tls13/key_update.h"
#include "ext/pre_shared_key.h"

static int generate_rms_keys(gnutls_session_t session);
static int generate_and_set_hs_traffic_keys(gnutls_session_t session);
static int generate_ap_traffic_keys(gnutls_session_t session);

#define SAVE_TRANSCRIPT \
	if (session->internals.flags & GNUTLS_POST_HANDSHAKE_AUTH) { \
		/* If post-handshake auth is in use we need a copy of the original \
		 * handshake transcript */ \
		memcpy( &session->internals.post_handshake_hash_buffer, \
			&session->internals.handshake_hash_buffer, \
			sizeof(session->internals.handshake_hash_buffer)); \
		_gnutls_buffer_init(&session->internals.handshake_hash_buffer); \
	}

/*
 * _gnutls13_handshake_client
 * This function performs the client side of the handshake of the TLS/SSL protocol.
 */
int _gnutls13_handshake_client(gnutls_session_t session)
{
	int ret = 0;

	switch (STATE) {
	case STATE99:
	case STATE100:
#ifdef TLS13_APPENDIX_D4
		/* We send it before keys are generated. That works because CCS
		 * is always being cached and queued and not being sent directly */
		ret = _gnutls_send_change_cipher_spec(session, AGAIN(STATE100));
		STATE = STATE100;
		IMED_RET("send change cipher spec", ret, 0);
#endif
		FALLTHROUGH;
	case STATE101:
		ret =
		    generate_and_set_hs_traffic_keys(session);
		STATE = STATE101;
		IMED_RET_FATAL("generate session keys", ret, 0);
		FALLTHROUGH;
	case STATE102:
		ret = _gnutls13_recv_encrypted_extensions(session);
		STATE = STATE102;
		IMED_RET("recv encrypted extensions", ret, 0);
		FALLTHROUGH;
	case STATE103:
		ret = _gnutls13_recv_certificate_request(session);
		STATE = STATE103;
		IMED_RET("recv certificate request", ret, 0);
		FALLTHROUGH;
	case STATE104:
		ret = _gnutls13_recv_certificate(session);
		STATE = STATE104;
		IMED_RET("recv certificate", ret, 0);
		FALLTHROUGH;
	case STATE105:
		ret = _gnutls13_recv_certificate_verify(session);
		STATE = STATE105;
		IMED_RET("recv server certificate verify", ret, 0);
		FALLTHROUGH;
	case STATE106:
		ret = _gnutls_run_verify_callback(session, GNUTLS_CLIENT);
		STATE = STATE106;
		if (ret < 0)
			return gnutls_assert_val(ret);
		FALLTHROUGH;
	case STATE107:
		ret = _gnutls13_recv_finished(session);
		STATE = STATE107;
		IMED_RET("recv finished", ret, 0);
		FALLTHROUGH;
	case STATE108:
		ret = _gnutls13_send_certificate(session, AGAIN(STATE108));
		STATE = STATE108;
		IMED_RET("send certificate", ret, 0);
		FALLTHROUGH;
	case STATE109:
		ret = _gnutls13_send_certificate_verify(session, AGAIN(STATE109));
		STATE = STATE109;
		IMED_RET("send certificate verify", ret, 0);
		FALLTHROUGH;
	case STATE110:
		ret = _gnutls13_send_finished(session, AGAIN(STATE110));
		STATE = STATE110;
		IMED_RET("send finished", ret, 0);
		FALLTHROUGH;
	case STATE111:
		STATE = STATE111;

		ret =
		    generate_ap_traffic_keys(session);
		IMED_RET_FATAL("generate app keys", ret, 0);

		ret = generate_rms_keys(session);
		IMED_RET_FATAL("generate rms keys", ret, 0);

		/* set traffic keys */
		ret = _tls13_connection_state_init(session, STAGE_APP);
		IMED_RET_FATAL("set app keys", ret, 0);

		STATE = STATE0;
		break;
	default:
		return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
	}


	/* explicitly reset any false start flags */
	session->internals.recv_state = RECV_STATE_0;
	session->internals.initial_negotiation_completed = 1;

	SAVE_TRANSCRIPT;

	if (session->internals.resumed != RESUME_FALSE)
		_gnutls_set_resumed_parameters(session);

	return 0;
}

static int generate_non_auth_rms_keys(gnutls_session_t session)
{
	int ret;
	/* we simulate client finished */
	uint8_t finished[MAX_HASH_SIZE+TLS_HANDSHAKE_HEADER_SIZE];
	unsigned spos;

	ret = _gnutls13_compute_finished(session->security_parameters.prf,
					 session->key.proto.tls13.hs_ckey,
					 &session->internals.handshake_hash_buffer,
					 finished+TLS_HANDSHAKE_HEADER_SIZE);
	if (ret < 0)
		return gnutls_assert_val(ret);

	spos = session->internals.handshake_hash_buffer.length;

	finished[0] = GNUTLS_HANDSHAKE_FINISHED;
	_gnutls_write_uint24(session->security_parameters.prf->output_size, finished+1);

	ret = _gnutls_buffer_append_data(&session->internals.handshake_hash_buffer, finished,
					 TLS_HANDSHAKE_HEADER_SIZE+session->security_parameters.prf->output_size);
	if (ret < 0)
		return gnutls_assert_val(ret);

	ret = _tls13_derive_secret(session, RMS_MASTER_LABEL, sizeof(RMS_MASTER_LABEL)-1,
				   session->internals.handshake_hash_buffer.data,
				   session->internals.handshake_hash_buffer.length,
				   session->key.proto.tls13.temp_secret,
				   session->key.proto.tls13.ap_rms);
	if (ret < 0)
		return gnutls_assert_val(ret);

	session->internals.handshake_hash_buffer.length = spos;

	return 0;
}

static int generate_rms_keys(gnutls_session_t session)
{
	int ret;

	ret = _tls13_derive_secret(session, RMS_MASTER_LABEL, sizeof(RMS_MASTER_LABEL)-1,
				   session->internals.handshake_hash_buffer.data,
				   session->internals.handshake_hash_buffer_client_finished_len,
				   session->key.proto.tls13.temp_secret,
				   session->key.proto.tls13.ap_rms);
	if (ret < 0)
		return gnutls_assert_val(ret);

	return 0;
}

static int generate_ap_traffic_keys(gnutls_session_t session)
{
	int ret;
	uint8_t zero[MAX_HASH_SIZE];

	ret = _tls13_derive_secret(session, DERIVED_LABEL, sizeof(DERIVED_LABEL)-1,
				   NULL, 0, session->key.proto.tls13.temp_secret,
				   session->key.proto.tls13.temp_secret);
	if (ret < 0)
		return gnutls_assert_val(ret);

	memset(zero, 0, session->security_parameters.prf->output_size);
	ret = _tls13_update_secret(session, zero, session->security_parameters.prf->output_size);
	if (ret < 0)
		return gnutls_assert_val(ret);

	ret = _tls13_derive_secret(session, EXPORTER_MASTER_LABEL, sizeof(EXPORTER_MASTER_LABEL)-1,
				   session->internals.handshake_hash_buffer.data,
				   session->internals.handshake_hash_buffer_server_finished_len,
				   session->key.proto.tls13.temp_secret,
				   session->key.proto.tls13.ap_expkey);
	if (ret < 0)
		return gnutls_assert_val(ret);

	_gnutls_nss_keylog_write(session, "EXPORTER_SECRET",
				 session->key.proto.tls13.ap_expkey,
				 session->security_parameters.prf->output_size);

	_gnutls_epoch_bump(session);
	ret = _gnutls_epoch_dup(session);
	if (ret < 0)
		return gnutls_assert_val(ret);

	return 0;
}

static int generate_and_set_hs_traffic_keys(gnutls_session_t session)
{
	int ret;
	unsigned null_key = 0;

	if (unlikely(session->key.proto.tls13.temp_secret_size == 0))
		return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

	if ((session->security_parameters.entity == GNUTLS_CLIENT &&
	      (!(session->internals.hsk_flags & HSK_KEY_SHARE_RECEIVED) ||
	        (!(session->internals.hsk_flags & HSK_PSK_KE_MODE_DHE_PSK) &&
	           session->internals.resumed != RESUME_FALSE))) ||
	    (session->security_parameters.entity == GNUTLS_SERVER &&
	      !(session->internals.hsk_flags & HSK_KEY_SHARE_SENT))) {

		if ((session->internals.hsk_flags & HSK_PSK_SELECTED) &&
		    (session->internals.hsk_flags & HSK_PSK_KE_MODE_PSK)) {
			null_key = 1;
		}
	}

	if (null_key) {
		uint8_t digest[MAX_HASH_SIZE];
		unsigned digest_size;

		if (unlikely(session->security_parameters.prf == NULL))
			return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

		digest_size = session->security_parameters.prf->output_size;
		memset(digest, 0, digest_size);

		ret = _tls13_update_secret(session, digest, digest_size);
		if (ret < 0) {
			gnutls_assert();
			return ret;
		}
	} else {
		if (unlikely(session->key.key.size == 0))
			return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

		ret = _tls13_update_secret(session, session->key.key.data, session->key.key.size);
		if (ret < 0) {
			gnutls_assert();
			return ret;
		}
	}

	ret = _tls13_connection_state_init(session, STAGE_HS);
	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	return 0;
}

#define TICKETS_TO_SEND 1

/*
 * _gnutls13_handshake_server
 * This function does the server stuff of the handshake protocol.
 */
int _gnutls13_handshake_server(gnutls_session_t session)
{
	int ret = 0;

	switch (STATE) {
	case STATE90:
		ret = _gnutls13_handshake_hash_buffers_synth(session, session->security_parameters.prf, 0);
		STATE = STATE90;
		IMED_RET_FATAL("reset handshake buffers", ret, 0);
		FALLTHROUGH;
	case STATE91:
		ret = _gnutls13_send_hello_retry_request(session, AGAIN(STATE91));
		STATE = STATE91;
		IMED_RET("send hello retry request", ret, 0);
		FALLTHROUGH;
	case STATE92:
#ifdef TLS13_APPENDIX_D4
		ret = _gnutls_send_change_cipher_spec(session, AGAIN(STATE92));
		STATE = STATE92;
		IMED_RET("send change cipher spec", ret, 0);
#endif
		FALLTHROUGH;
	case STATE93:
		ret =
		    _gnutls_recv_handshake(session,
					   GNUTLS_HANDSHAKE_CLIENT_HELLO,
					   0, NULL);
		if (ret == GNUTLS_E_INT_RET_0) {
			/* this is triggered by post_client_hello, and instructs the
			 * handshake to proceed but be put on hold */
			ret = GNUTLS_E_INTERRUPTED;
			STATE = STATE94; /* hello already parsed -> move to next state */
		} else {
			STATE = STATE93;
		}

		IMED_RET("recv client hello", ret, 0);
		FALLTHROUGH;
	case STATE94:
		ret = _gnutls_send_server_hello(session, AGAIN(STATE94));
		STATE = STATE94;
		IMED_RET("send hello", ret, 0);
		FALLTHROUGH;
	case STATE99:
	case STATE100:
#ifdef TLS13_APPENDIX_D4
		/* don't send CCS twice: when HRR has already been
		 * sent, CCS should have followed it (see above) */
		if (!(session->internals.hsk_flags & HSK_HRR_SENT)) {
			ret = _gnutls_send_change_cipher_spec(session, AGAIN(STATE100));
			STATE = STATE100;
			IMED_RET("send change cipher spec", ret, 0);
		}
#endif
		FALLTHROUGH;
	case STATE101:
		ret =
		    generate_and_set_hs_traffic_keys(session);
		STATE = STATE101;
		IMED_RET_FATAL("generate session keys", ret, 0);
		FALLTHROUGH;
	case STATE102:
		ret = _gnutls13_send_encrypted_extensions(session, AGAIN(STATE102));
		STATE = STATE102;
		IMED_RET("send encrypted extensions", ret, 0);
		FALLTHROUGH;
	case STATE103:
		ret = _gnutls13_send_certificate_request(session, AGAIN(STATE103));
		STATE = STATE103;
		IMED_RET("send certificate request", ret, 0);
		FALLTHROUGH;
	case STATE104:
		ret = _gnutls13_send_certificate(session, AGAIN(STATE104));
		STATE = STATE104;
		IMED_RET("send certificate", ret, 0);
		FALLTHROUGH;
	case STATE105:
		ret = _gnutls13_send_certificate_verify(session, AGAIN(STATE105));
		STATE = STATE105;
		IMED_RET("send certificate verify", ret, 0);
		FALLTHROUGH;
	case STATE106:
		ret = _gnutls13_send_finished(session, AGAIN(STATE106));
		STATE = STATE106;
		IMED_RET("send finished", ret, 0);
		FALLTHROUGH;
	case STATE107:
		/* At this point our sending keys should be the app keys
		 * see 4.4.4 at draft-ietf-tls-tls13-28 */
		ret =
		    generate_ap_traffic_keys(session);
		IMED_RET_FATAL("generate app keys", ret, 0);

		/* If the session is unauthenticated, try to optimize the handshake by
		 * sending the session ticket early. */
		if (!(session->internals.hsk_flags & (HSK_CRT_REQ_SENT|HSK_PSK_SELECTED))) {
			STATE = STATE107;

			ret = generate_non_auth_rms_keys(session);
			IMED_RET_FATAL("generate rms keys", ret, 0);

			session->internals.hsk_flags |= HSK_EARLY_START_USED;
			_gnutls_handshake_log("HSK[%p]: unauthenticated session eligible for early start\n", session);
		}

		ret = _tls13_write_connection_state_init(session, STAGE_APP);
		IMED_RET_FATAL("set write app keys", ret, 0);

		_gnutls_handshake_log("HSK[%p]: switching early to application traffic keys\n", session);

		FALLTHROUGH;
	case STATE108:
		if (session->internals.resumed != RESUME_FALSE)
			_gnutls_set_resumed_parameters(session);

		if (session->internals.hsk_flags & HSK_EARLY_START_USED) {
			ret = _gnutls13_send_session_ticket(session, TICKETS_TO_SEND,
							    AGAIN(STATE108));

			STATE = STATE108;
			IMED_RET("send session ticket", ret, 0);

			/* complete this phase of the handshake. We
			 * should be called again by gnutls_record_recv()
			 */

			if (session->internals.flags & GNUTLS_ENABLE_EARLY_START) {
				STATE = STATE112; /* finished */
				gnutls_assert();

				session->internals.recv_state = RECV_STATE_EARLY_START;
				return 0;
			}
		}
		FALLTHROUGH;
	case STATE109:
		ret = _gnutls13_recv_certificate(session);
		STATE = STATE109;
		IMED_RET("recv certificate", ret, 0);
		FALLTHROUGH;
	case STATE110:
		ret = _gnutls13_recv_certificate_verify(session);
		STATE = STATE110;
		IMED_RET("recv certificate verify", ret, 0);
		FALLTHROUGH;
	case STATE111:
		ret = _gnutls_run_verify_callback(session, GNUTLS_CLIENT);
		STATE = STATE111;
		if (ret < 0)
			return gnutls_assert_val(ret);
		FALLTHROUGH;
	case STATE112: /* can enter from STATE108 */
		ret = _gnutls13_recv_finished(session);
		STATE = STATE112;
		IMED_RET("recv finished", ret, 0);
		FALLTHROUGH;
	case STATE113:
		/* If we did request a client certificate, then we can
		 * only send the tickets here */
		STATE = STATE113;

		if (!(session->internals.hsk_flags & HSK_EARLY_START_USED)) {
			ret = generate_rms_keys(session);
			IMED_RET_FATAL("generate rms keys", ret, 0);
		}

		ret = _tls13_read_connection_state_init(session, STAGE_APP);
		IMED_RET_FATAL("set read app keys", ret, 0);

		FALLTHROUGH;
	case STATE114:
		if (!(session->internals.hsk_flags & (HSK_TLS13_TICKET_SENT|HSK_EARLY_START_USED))) {
			ret = _gnutls13_send_session_ticket(session, TICKETS_TO_SEND,
							    AGAIN(STATE114));
			STATE = STATE114;
			IMED_RET("send session ticket", ret, 0);
		}

		STATE = STATE0;
		break;
	default:
		return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
	}

	/* explicitly reset any false start flags */
	session->internals.recv_state = RECV_STATE_0;
	session->internals.initial_negotiation_completed = 1;

	SAVE_TRANSCRIPT;


	return 0;
}

/* Processes handshake messages received asynchronously after initial handshake.
 *
 * It is called once per message and should return success, or a fatal error code.
 */
int
_gnutls13_recv_async_handshake(gnutls_session_t session)
{
	int ret;
	handshake_buffer_st hsk;

	/* The following messages are expected asynchronously after
	 * the handshake process is complete */
	if (unlikely(session->internals.handshake_in_progress))
		return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);

	do {
		/* the received handshake message has already been pushed into
		 * handshake buffers. As we do not need to use the handshake hash
		 * buffers we call the lower level receive functions */
		ret = _gnutls_handshake_io_recv_int(session, GNUTLS_HANDSHAKE_ANY, &hsk, 0);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}
		session->internals.last_handshake_in = hsk.htype;

		ret = _gnutls_call_hook_func(session, hsk.htype, GNUTLS_HOOK_PRE, 1,
					     hsk.data.data, hsk.data.length);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}

		switch(hsk.htype) {
			case GNUTLS_HANDSHAKE_CERTIFICATE_REQUEST:
				if (!(session->security_parameters.entity == GNUTLS_CLIENT) ||
				    !(session->internals.flags & GNUTLS_POST_HANDSHAKE_AUTH)) {
					ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
					goto cleanup;
				}

				_gnutls_buffer_reset(&session->internals.reauth_buffer);

				/* include the handshake headers in reauth buffer */
				ret = _gnutls_buffer_append_data(&session->internals.reauth_buffer,
								 hsk.header, hsk.header_size);
				if (ret < 0) {
					gnutls_assert();
					goto cleanup;
				}

				ret = _gnutls_buffer_append_data(&session->internals.reauth_buffer,
								 hsk.data.data, hsk.data.length);
				if (ret < 0) {
					gnutls_assert();
					goto cleanup;
				}

				/* Application is expected to handle re-authentication
				 * explicitly.  */
				ret = GNUTLS_E_REAUTH_REQUEST;
				goto cleanup;

			case GNUTLS_HANDSHAKE_KEY_UPDATE:
				ret = _gnutls13_recv_key_update(session, &hsk.data);
				if (ret < 0) {
					gnutls_assert();
					goto cleanup;
				}

				/* Handshake messages MUST NOT span key changes, i.e., we
				 * should not have any other pending handshake messages from
				 * the same record. */
				if (session->internals.handshake_recv_buffer_size != 0) {
					ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
					goto cleanup;
				}
				break;
			case GNUTLS_HANDSHAKE_NEW_SESSION_TICKET:
				if (session->security_parameters.entity != GNUTLS_CLIENT) {
					ret = gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
					goto cleanup;
				}

				ret = _gnutls13_recv_session_ticket(session, &hsk.data);
				if (ret < 0) {
					gnutls_assert();
					goto cleanup;
				}

				memcpy(session->internals.tls13_ticket.resumption_master_secret,
				       session->key.proto.tls13.ap_rms,
				       session->key.proto.tls13.temp_secret_size);

				session->internals.tls13_ticket.prf = session->security_parameters.prf;
				session->internals.hsk_flags |= HSK_TICKET_RECEIVED;
				break;
			default:
				gnutls_assert();
				ret = GNUTLS_E_UNEXPECTED_PACKET;
				goto cleanup;
		}

		ret = _gnutls_call_hook_func(session, hsk.htype, GNUTLS_HOOK_POST, 1, hsk.data.data, hsk.data.length);
		if (ret < 0) {
			gnutls_assert();
			goto cleanup;
		}
		_gnutls_handshake_buffer_clear(&hsk);

	} while (_gnutls_record_buffer_get_size(session) > 0);

	session->internals.recv_state = RECV_STATE_0;

	return 0;

 cleanup:
	/* if we have pending/partial handshake data in buffers, ensure that
	 * next read will read handshake data */
	if (_gnutls_record_buffer_get_size(session) > 0)
		session->internals.recv_state = RECV_STATE_ASYNC_HANDSHAKE;
	else
		session->internals.recv_state = RECV_STATE_0;

	_gnutls_handshake_buffer_clear(&hsk);
	return ret;
}

/**
 * gnutls_session_ticket_send:
 * @session: is a #gnutls_session_t type.
 * @nr: the number of tickets to send
 * @flags: must be zero
 *
 * Sends a fresh session ticket to the peer. This is relevant only
 * in server side under TLS1.3. This function may also return %GNUTLS_E_AGAIN
 * or %GNUTLS_E_INTERRUPTED.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or a negative error code.
 **/
int gnutls_session_ticket_send(gnutls_session_t session, unsigned nr, unsigned flags)
{
	int ret = 0;
	const version_entry_st *vers = get_version(session);

	if (!vers->tls13_sem || session->security_parameters.entity == GNUTLS_CLIENT)
		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	if (nr == 0)
		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	switch (TICKET_STATE) {
	case TICKET_STATE0:
		ret = _gnutls_io_write_flush(session);
		TICKET_STATE = TICKET_STATE0;
		if (ret < 0) {
			gnutls_assert();
			return ret;
		}
		FALLTHROUGH;
	case TICKET_STATE1:
		ret =
		    _gnutls13_send_session_ticket(session, nr, TICKET_STATE==TICKET_STATE1?1:0);
		TICKET_STATE = TICKET_STATE1;
		if (ret < 0) {
			gnutls_assert();
			return ret;
		}
		break;
	default:
		gnutls_assert();
		return GNUTLS_E_INTERNAL_ERROR;
	}

	TICKET_STATE = TICKET_STATE0;

	return 0;
}