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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2025-present Eclipse ThreadX Contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Secure Component */
/** */
/** Datagram Transport Layer Security (DTLS) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_dtls.h"
#include "nx_udp.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_dtls_receive_callback PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function serves as the notification callback provided to NetX */
/* that is invoked when a UDP packet has been received. It checks the */
/* DTLS session cache for a matching client (based on IP address and */
/* port) and then invokes the application callback with the */
/* appropriate session object. If a previous session was not found, a */
/* new session is allocated (if available) and the DTLS handshake is */
/* initiated. Once the handshake is complete the user callback is */
/* invoked as above. */
/* */
/* INPUT */
/* */
/* socket_ptr UDP socket */
/* */
/* OUTPUT */
/* */
/* N/A */
/* */
/* CALLS */
/* */
/* _nxd_udp_source_extract Extract IP address and port */
/* _nx_udp_socket_port_get Get local port */
/* nx_secure_dtls_session_cache_find Check DTLS session cache */
/* nx_secure_dtls_session_cache_get_new Get new DTLS session */
/* nx_secure_tls_packet_release Release packet */
/* nx_packet_allocate Allocate packet */
/* _nxd_udp_socket_send Send UDP packet */
/* nx_udp_socket_receive Receive packet */
/* tx_thread_wait_abort Abort wait process */
/* tx_mutex_get Get protection mutex */
/* tx_mutex_put Put protection mutex */
/* [nx_secure_dtls_error_notify] Notify application of error */
/* [nx_secure_dtls_receive_notify] Notify application of packet */
/* receive */
/* */
/* CALLED BY */
/* */
/* Application Code */
/* */
/**************************************************************************/
VOID _nx_secure_dtls_receive_callback(NX_UDP_SOCKET *socket_ptr)
{
#ifdef NX_SECURE_ENABLE_DTLS
TX_INTERRUPT_SAVE_AREA
NXD_ADDRESS ip_address;
UINT remote_port;
UINT local_port;
UINT status;
ULONG packet_type;
NX_PACKET *packet_ptr;
UCHAR *send_data;
NX_PACKET *temp_packet_ptr;
NX_SECURE_DTLS_SERVER *dtls_server;
NX_SECURE_DTLS_SESSION *dtls_session;
if(socket_ptr -> nx_udp_socket_receive_head == NX_NULL)
{
return;
}
/* Extract IP address and port from received packet. */
socket_ptr -> nx_udp_socket_receive_head -> nx_packet_prepend_ptr += sizeof(NX_UDP_HEADER);
status = _nxd_udp_source_extract(socket_ptr->nx_udp_socket_receive_head, &ip_address, &remote_port);
socket_ptr -> nx_udp_socket_receive_head -> nx_packet_prepend_ptr -= sizeof(NX_UDP_HEADER);
if(status != NX_SUCCESS)
{
return;
}
/* Extract local port from socket. */
status = _nx_udp_socket_port_get(socket_ptr, &local_port);
if(status != NX_SUCCESS)
{
return;
}
/* Get the DTLS server from our UDP socket so we can access the session cache. */
dtls_server = (NX_SECURE_DTLS_SERVER*)(socket_ptr -> nx_udp_socket_reserved_ptr);
/* Check session cache for existing DTLS session. */
status = nx_secure_dtls_session_cache_find(dtls_server, &dtls_session, &ip_address, remote_port, local_port);
/* Do we have an established session? */
if(status == NX_SECURE_DTLS_SESSION_NOT_FOUND)
{
/* If received packet is ALERT, just drop it. */
if ((socket_ptr -> nx_udp_socket_receive_head -> nx_packet_length < NX_SECURE_DTLS_RECORD_HEADER_SIZE) ||
(socket_ptr -> nx_udp_socket_receive_head -> nx_packet_prepend_ptr[8] == NX_SECURE_TLS_ALERT))
{
/* Lockout interrupts. */
TX_DISABLE
/* Remove the header packet from the queue. */
packet_ptr = socket_ptr -> nx_udp_socket_receive_head;
socket_ptr -> nx_udp_socket_receive_head = packet_ptr -> nx_packet_queue_next;
packet_ptr -> nx_packet_queue_next = NX_NULL;
/* If this was the last packet, set the tail pointer to NULL. */
if (socket_ptr -> nx_udp_socket_receive_head == NX_NULL)
{
socket_ptr -> nx_udp_socket_receive_tail = NX_NULL;
}
/* Decrease the queued packet count. */
socket_ptr -> nx_udp_socket_receive_count--;
/* Restore interrupts. */
TX_RESTORE
/* Release the packet. */
nx_secure_tls_packet_release(packet_ptr);
return;
}
/* Get a new session. */
status = nx_secure_dtls_session_cache_get_new(dtls_server, &dtls_session, &ip_address, remote_port, local_port);
/* Make sure we got a session. */
if(status == NX_SECURE_TLS_NO_FREE_DTLS_SESSIONS)
{
/* No session? Drop the connection with an internal error alert.
See RFC 5246 Sec. 7.2.2 - internal error is used for memory allocation failures.
We don't have a DTLS session, so build a simple DTLS alert record to send. */
/* Lockout interrupts. */
TX_DISABLE
/* Remove the header packet from the queue. */
packet_ptr = socket_ptr -> nx_udp_socket_receive_head;
socket_ptr -> nx_udp_socket_receive_head = packet_ptr -> nx_packet_queue_next;
packet_ptr -> nx_packet_queue_next = NX_NULL;
/* If this was the last packet, set the tail pointer to NULL. */
if (socket_ptr -> nx_udp_socket_receive_head == NX_NULL)
{
socket_ptr -> nx_udp_socket_receive_tail = NX_NULL;
}
/* Decrease the queued packet count. */
socket_ptr -> nx_udp_socket_receive_count--;
/* Restore interrupts. */
TX_RESTORE
/* Release the packet. */
nx_secure_tls_packet_release(packet_ptr);
/* Get a packet to send the alert to the client. */
if (ip_address.nxd_ip_version == NX_IP_VERSION_V4)
{
packet_type = NX_IPv4_UDP_PACKET;
}
else
{
packet_type = NX_IPv6_UDP_PACKET;
}
status = nx_packet_allocate(socket_ptr->nx_udp_socket_ip_ptr->nx_ip_default_packet_pool,
&packet_ptr, packet_type, NX_NO_WAIT);
if(status != NX_SUCCESS)
{
return;
}
if (((ULONG)(packet_ptr -> nx_packet_data_end) - (ULONG)(packet_ptr -> nx_packet_append_ptr)) < 15)
{
/* Packet buffer too small. */
nx_secure_tls_packet_release(packet_ptr);
return;
}
send_data = packet_ptr -> nx_packet_append_ptr;
/* Build the DTLS record header. */
send_data[0] = NX_SECURE_TLS_ALERT;
/* Set the version number - use DTLS 1.2. */
send_data[1] = (UCHAR)(NX_SECURE_DTLS_VERSION_MAJOR);
send_data[2] = (UCHAR)(NX_SECURE_DTLS_VERSION_MINOR_1_2);
/* DTLS Epoch counter. */
send_data[3] = 0;
send_data[4] = 0;
/* DTLS sequence number. */
send_data[5] = 0;
send_data[6] = 0;
send_data[7] = 0;
send_data[8] = 0;
send_data[9] = 0;
send_data[10] = 0;
/* DTLS message length - 2 bytes for the alert. */
send_data[11] = 0;
send_data[12] = 2;
/* Populate the record with the alert level and alert number to send to the remote host. */
send_data[13] = (UCHAR)(NX_SECURE_TLS_ALERT_LEVEL_FATAL);
send_data[14] = (UCHAR)(NX_SECURE_TLS_ALERT_INTERNAL_ERROR);
/* Make sure the caller has the right length of data to send. */
packet_ptr -> nx_packet_append_ptr = packet_ptr -> nx_packet_append_ptr + 15;
packet_ptr -> nx_packet_length = 15;
/* Send the UDP packet containing our record. */
status = _nxd_udp_socket_send(socket_ptr, packet_ptr, &ip_address, remote_port);
/* Notify the application that we had to drop an incoming connection. */
if(dtls_server->nx_secure_dtls_error_notify != NX_NULL)
{
dtls_server->nx_secure_dtls_error_notify(NX_NULL, NX_SECURE_TLS_NO_FREE_DTLS_SESSIONS);
}
return;
}
/* Receive our packet. */
status = nx_udp_socket_receive(socket_ptr, &packet_ptr, NX_NO_WAIT);
if (status)
{
return;
}
/* New session, retrieve the UDP packet and place in our session receive queue. */
dtls_session -> nx_secure_dtls_receive_queue_head = packet_ptr;
/* Make sure the queue pointer is cleared. */
packet_ptr -> nx_packet_queue_next = NX_NULL;
/* Notify the application of a new connection - it is up to the application to call
nx_secure_dtls_session_start to kick off the handshake! */
dtls_server -> nx_secure_dtls_connect_notify(dtls_session, &ip_address, remote_port);
}
else
{
/* Receive our packet. */
status = nx_udp_socket_receive(socket_ptr, &packet_ptr, NX_NO_WAIT);
if (status)
{
return;
}
/* Get the protection before modifying the queue pointer. */
tx_mutex_get(&_nx_secure_tls_protection, TX_WAIT_FOREVER);
if (!dtls_session -> nx_secure_dtls_session_in_use)
{
/* Session is not in use. */
tx_mutex_put(&_nx_secure_tls_protection);
return;
}
/* Established session, make sure that we append to the end of the receive queue. */
if (dtls_session -> nx_secure_dtls_receive_queue_head == NX_NULL)
{
dtls_session -> nx_secure_dtls_receive_queue_head = packet_ptr;
}
else
{
temp_packet_ptr = dtls_session -> nx_secure_dtls_receive_queue_head;
while(temp_packet_ptr -> nx_packet_queue_next != NX_NULL)
{
temp_packet_ptr = temp_packet_ptr -> nx_packet_queue_next;
}
temp_packet_ptr -> nx_packet_queue_next = packet_ptr;
}
/* Make sure the queue pointer is cleared. */
packet_ptr -> nx_packet_queue_next = NX_NULL;
/* Is there any thread waiting for packet? */
if (dtls_session -> nx_secure_dtls_thread_suspended)
{
/* Yes. Just abort it. */
tx_thread_wait_abort(dtls_session -> nx_secure_dtls_thread_suspended);
dtls_session -> nx_secure_dtls_thread_suspended = NX_NULL;
}
/* If the handshake isn't finished, don't notify application. */
if (dtls_session -> nx_secure_dtls_tls_session.nx_secure_tls_server_state < NX_SECURE_TLS_SERVER_STATE_HANDSHAKE_FINISHED)
{
/* Release the protection. */
tx_mutex_put(&_nx_secure_tls_protection);
return;
}
/* Release the protection. */
tx_mutex_put(&_nx_secure_tls_protection);
/* Invoke the session callback to notify application of packet receive. */
dtls_server -> nx_secure_dtls_receive_notify(dtls_session);
}
#else
NX_PARAMETER_NOT_USED(socket_ptr);
return;
#endif /* NX_SECURE_ENABLE_DTLS */
}
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