godot/modules/mbedtls/packet_peer_mbed_dtls.cpp

/*************************************************************************/
/*  packet_peer_mbed_dtls.cpp                                            */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "packet_peer_mbed_dtls.h"
#include "mbedtls/platform_util.h"

#include "core/io/stream_peer_ssl.h"
#include "core/os/file_access.h"

int PacketPeerMbedDTLS::bio_send(void *ctx, const unsigned char *buf, size_t len) {
	if (buf == nullptr || len <= 0) {
		return 0;
	}

	PacketPeerMbedDTLS *sp = (PacketPeerMbedDTLS *)ctx;

	ERR_FAIL_COND_V(sp == nullptr, 0);

	Error err = sp->base->put_packet((const uint8_t *)buf, len);
	if (err == ERR_BUSY) {
		return MBEDTLS_ERR_SSL_WANT_WRITE;
	} else if (err != OK) {
		ERR_FAIL_V(MBEDTLS_ERR_SSL_INTERNAL_ERROR);
	}
	return len;
}

int PacketPeerMbedDTLS::bio_recv(void *ctx, unsigned char *buf, size_t len) {
	if (buf == nullptr || len <= 0) {
		return 0;
	}

	PacketPeerMbedDTLS *sp = (PacketPeerMbedDTLS *)ctx;

	ERR_FAIL_COND_V(sp == nullptr, 0);

	int pc = sp->base->get_available_packet_count();
	if (pc == 0) {
		return MBEDTLS_ERR_SSL_WANT_READ;
	} else if (pc < 0) {
		ERR_FAIL_V(MBEDTLS_ERR_SSL_INTERNAL_ERROR);
	}

	const uint8_t *buffer;
	int buffer_size = 0;
	Error err = sp->base->get_packet(&buffer, buffer_size);
	if (err != OK) {
		return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
	}
	memcpy(buf, buffer, buffer_size);
	return buffer_size;
}

void PacketPeerMbedDTLS::_cleanup() {
	ssl_ctx->clear();
	base = Ref<PacketPeer>();
	status = STATUS_DISCONNECTED;
}

int PacketPeerMbedDTLS::_set_cookie() {
	// Setup DTLS session cookie for this client
	uint8_t client_id[18];
	IP_Address addr = base->get_packet_address();
	uint16_t port = base->get_packet_port();
	memcpy(client_id, addr.get_ipv6(), 16);
	memcpy(&client_id[16], (uint8_t *)&port, 2);
	return mbedtls_ssl_set_client_transport_id(ssl_ctx->get_context(), client_id, 18);
}

Error PacketPeerMbedDTLS::_do_handshake() {
	int ret = 0;
	while ((ret = mbedtls_ssl_handshake(ssl_ctx->get_context())) != 0) {
		if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
			if (ret != MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED) {
				ERR_PRINT("TLS handshake error: " + itos(ret));
				SSLContextMbedTLS::print_mbedtls_error(ret);
			}
			_cleanup();
			status = STATUS_ERROR;
			return FAILED;
		}
		// Will retry via poll later
		return OK;
	}

	status = STATUS_CONNECTED;
	return OK;
}

Error PacketPeerMbedDTLS::connect_to_peer(Ref<PacketPeerUDP> p_base, bool p_validate_certs, const String &p_for_hostname, Ref<X509Certificate> p_ca_certs) {
	ERR_FAIL_COND_V(!p_base.is_valid() || !p_base->is_connected_to_host(), ERR_INVALID_PARAMETER);

	base = p_base;
	int ret = 0;
	int authmode = p_validate_certs ? MBEDTLS_SSL_VERIFY_REQUIRED : MBEDTLS_SSL_VERIFY_NONE;

	Error err = ssl_ctx->init_client(MBEDTLS_SSL_TRANSPORT_DATAGRAM, authmode, p_ca_certs);
	ERR_FAIL_COND_V(err != OK, err);

	mbedtls_ssl_set_hostname(ssl_ctx->get_context(), p_for_hostname.utf8().get_data());
	mbedtls_ssl_set_bio(ssl_ctx->get_context(), this, bio_send, bio_recv, nullptr);
	mbedtls_ssl_set_timer_cb(ssl_ctx->get_context(), &timer, mbedtls_timing_set_delay, mbedtls_timing_get_delay);

	status = STATUS_HANDSHAKING;

	if ((ret = _do_handshake()) != OK) {
		status = STATUS_ERROR_HOSTNAME_MISMATCH;
		return FAILED;
	}

	return OK;
}

Error PacketPeerMbedDTLS::accept_peer(Ref<PacketPeerUDP> p_base, Ref<CryptoKey> p_key, Ref<X509Certificate> p_cert, Ref<X509Certificate> p_ca_chain, Ref<CookieContextMbedTLS> p_cookies) {
	Error err = ssl_ctx->init_server(MBEDTLS_SSL_TRANSPORT_DATAGRAM, MBEDTLS_SSL_VERIFY_NONE, p_key, p_cert, p_cookies);
	ERR_FAIL_COND_V(err != OK, err);

	base = p_base;
	base->set_blocking_mode(false);

	mbedtls_ssl_session_reset(ssl_ctx->get_context());

	int ret = _set_cookie();
	if (ret != 0) {
		_cleanup();
		ERR_FAIL_V_MSG(FAILED, "Error setting DTLS client cookie");
	}

	mbedtls_ssl_set_bio(ssl_ctx->get_context(), this, bio_send, bio_recv, nullptr);
	mbedtls_ssl_set_timer_cb(ssl_ctx->get_context(), &timer, mbedtls_timing_set_delay, mbedtls_timing_get_delay);

	status = STATUS_HANDSHAKING;

	if ((ret = _do_handshake()) != OK) {
		status = STATUS_ERROR;
		return FAILED;
	}

	return OK;
}

Error PacketPeerMbedDTLS::put_packet(const uint8_t *p_buffer, int p_bytes) {
	ERR_FAIL_COND_V(status != STATUS_CONNECTED, ERR_UNCONFIGURED);

	if (p_bytes == 0) {
		return OK;
	}

	int ret = mbedtls_ssl_write(ssl_ctx->get_context(), p_buffer, p_bytes);
	if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
		ret = 0; // non blocking io
	} else if (ret <= 0) {
		SSLContextMbedTLS::print_mbedtls_error(ret);
		_cleanup();
		return ERR_CONNECTION_ERROR;
	}

	return OK;
}

Error PacketPeerMbedDTLS::get_packet(const uint8_t **r_buffer, int &r_bytes) {
	ERR_FAIL_COND_V(status != STATUS_CONNECTED, ERR_UNCONFIGURED);

	r_bytes = 0;

	int ret = mbedtls_ssl_read(ssl_ctx->get_context(), packet_buffer, PACKET_BUFFER_SIZE);
	if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
		ret = 0; // non blocking io
	} else if (ret <= 0) {
		if (ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY) {
			// Also send close notify back
			disconnect_from_peer();
		} else {
			_cleanup();
			status = STATUS_ERROR;
			SSLContextMbedTLS::print_mbedtls_error(ret);
		}
		return ERR_CONNECTION_ERROR;
	}
	*r_buffer = packet_buffer;
	r_bytes = ret;

	return OK;
}

void PacketPeerMbedDTLS::poll() {
	if (status == STATUS_HANDSHAKING) {
		_do_handshake();
		return;
	} else if (status != STATUS_CONNECTED) {
		return;
	}

	ERR_FAIL_COND(!base.is_valid());

	int ret = mbedtls_ssl_read(ssl_ctx->get_context(), nullptr, 0);

	if (ret < 0 && ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
		if (ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY) {
			// Also send close notify back
			disconnect_from_peer();
		} else {
			_cleanup();
			status = STATUS_ERROR;
			SSLContextMbedTLS::print_mbedtls_error(ret);
		}
	}
}

int PacketPeerMbedDTLS::get_available_packet_count() const {
	ERR_FAIL_COND_V(status != STATUS_CONNECTED, 0);

	return mbedtls_ssl_get_bytes_avail(&(ssl_ctx->ssl)) > 0 ? 1 : 0;
}

int PacketPeerMbedDTLS::get_max_packet_size() const {
	return 488; // 512 (UDP in Godot) - 24 (DTLS header)
}

PacketPeerMbedDTLS::PacketPeerMbedDTLS() {
	ssl_ctx.instance();
}

PacketPeerMbedDTLS::~PacketPeerMbedDTLS() {
	disconnect_from_peer();
}

void PacketPeerMbedDTLS::disconnect_from_peer() {
	if (status != STATUS_CONNECTED && status != STATUS_HANDSHAKING) {
		return;
	}

	if (status == STATUS_CONNECTED) {
		int ret = 0;
		// Send SSL close notification, blocking, but ignore other errors.
		do {
			ret = mbedtls_ssl_close_notify(ssl_ctx->get_context());
		} while (ret == MBEDTLS_ERR_SSL_WANT_WRITE);
	}

	_cleanup();
}

PacketPeerMbedDTLS::Status PacketPeerMbedDTLS::get_status() const {
	return status;
}

PacketPeerDTLS *PacketPeerMbedDTLS::_create_func() {
	return memnew(PacketPeerMbedDTLS);
}

void PacketPeerMbedDTLS::initialize_dtls() {
	_create = _create_func;
	available = true;
}

void PacketPeerMbedDTLS::finalize_dtls() {
	_create = nullptr;
	available = false;
}