Add DTLS 1.2 Mulicast Example.
Anthony Hu
parent
a9d5b45b15
commit
dfed0437ab
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# DTLS Multicast Examples Makefile
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CC = gcc
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WOLFSSL_INSTALL_DIR = /usr/local
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CFLAGS = -Wall -I$(WOLFSSL_INSTALL_DIR)/include
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LIBS = -L$(WOLFSSL_INSTALL_DIR)/lib -lwolfssl -lm
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# build targets
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TARGETS = mcast-peer
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all: $(TARGETS)
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mcast-peer: mcast-peer.c
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$(CC) -o $@ $< $(CFLAGS) $(LIBS)
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clean:
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rm -f $(TARGETS)
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# Helper targets for running the example
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run-node0:
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./mcast-peer 0
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run-node1:
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./mcast-peer 1
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run-node2:
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./mcast-peer 2
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# DTLS 1.2 Multicast Example
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This example demonstrates DTLS 1.2 multicast communication using wolfSSL's multicast APIs. Three peer applications can securely communicate with each other over UDP multicast.
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## Overview
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DTLS multicast allows multiple peers to share encrypted/authenticated communication over IP multicast. Unlike traditional TLS/DTLS which uses a handshake to establish keys, multicast DTLS uses pre-shared secrets that are distributed out-of-band to all participants.
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This example uses:
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- **WDM-NULL-SHA256** cipher suite (NULL encryption with SHA-256 for message authentication)
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- Pre-shared secret material (PMS, client random, server random)
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- Multicast group `239.255.0.1:12345`
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NOTE: Since this is using NULL encryption, all messages going over the wire are plaintext. This example provides no confidentiality.
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## Requirements
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wolfSSL must be built with multicast support:
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```bash
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cd /path/to/wolfssl
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./configure --enable-dtls --enable-mcast
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make
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```
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## Building
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```bash
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make
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```
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## Usage
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Run each peer in a separate terminal with a unique node ID (0, 1, or 2):
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```bash
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# Terminal 1
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./mcast-peer 0
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# Terminal 2
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./mcast-peer 1
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# Terminal 3
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./mcast-peer 2
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```
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Each peer will:
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1. Join the multicast group
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2. Send a message every 3 seconds
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3. Receive and display messages from other peers
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4. Exit cleanly on Ctrl+C
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## Example Output
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```
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=== DTLS Multicast Peer - Node 0 ===
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Node 0: Sockets ready, joined multicast group 239.255.0.1:12345
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Node 0: Added peer 1 to receive tracking
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Node 0: Added peer 2 to receive tracking
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Node 0: Ready. Press Ctrl+C to exit.
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Node 0: Sending messages every 3 seconds...
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Node 0: Sent: "Hello from node 0, message #1"
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Node 0: Received from peer 1: "Hello from node 1, message #1"
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Node 0: Received from peer 2: "Hello from node 2, message #1"
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```
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## API Usage Notes
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The wolfSSL multicast APIs must be called in a specific order:
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1. `wolfSSL_CTX_mcast_set_member_id()` - Set this node's ID
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2. `wolfSSL_CTX_set_cipher_list()` - Set multicast cipher suite
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3. `wolfSSL_new()` - Create SSL objects
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4. `wolfSSL_mcast_peer_add()` - Register expected peers (**before** setting secret)
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5. `wolfSSL_set_secret()` - Set the pre-shared secret (**after** adding peers)
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6. `wolfSSL_write()` / `wolfSSL_mcast_read()` - Send/receive messages
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**Important**: `wolfSSL_mcast_peer_add()` must be called BEFORE `wolfSSL_set_secret()` because `wolfSSL_mcast_peer_add()` zeros the peer entry (including the epoch), and `wolfSSL_set_secret()` sets the epoch for all registered peers.
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## Key Concepts
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### Multicast Member ID
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Each peer has a unique ID (0-255) set via `wolfSSL_CTX_mcast_set_member_id()`. This ID is embedded in outgoing DTLS records and used by receivers to identify the sender.
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### Pre-Shared Secret
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All peers must use identical secret material:
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- Pre-master secret (PMS)
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- Client random
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- Server random
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- Cipher suite identifier
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In production, this material would be distributed securely out-of-band (e.g., via a key server).
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### NULL Encryption
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This example is using NULL encryption. That means all messages going over the wire are plaintext. This example provides no confidentiality.
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## References
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- [wolfSSL Manual - DTLS](https://www.wolfssl.com/documentation/manuals/wolfssl/chapter02.html)
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- [RFC 6347 - DTLS 1.2](https://tools.ietf.org/html/rfc6347)
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@ -0,0 +1,457 @@
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/* mcast-peer.c
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*
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* Copyright (C) 2006-2025 wolfSSL Inc.
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*
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* This file is part of wolfSSL. (formerly known as CyaSSL)
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*
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* wolfSSL is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* wolfSSL is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*
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*=============================================================================
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*
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* Example of DTLS 1.2 multicast with PSK using wolfSSL.
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* Three peers can communicate with each other over multicast.
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*
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* Usage: ./mcast-peer <node_id>
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* where node_id is 0, 1, or 2
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*
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* Requires wolfSSL built with: ./configure --enable-dtls --enable-mcast
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*/
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#include <wolfssl/options.h>
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#include <wolfssl/ssl.h>
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#include <wolfssl/error-ssl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <signal.h>
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#include <sys/socket.h>
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#include <sys/select.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <fcntl.h>
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#include <time.h>
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/* Multicast group settings */
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#define MCAST_GROUP "239.255.0.1"
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#define MCAST_PORT 12345
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#define MSGLEN 256
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/* Number of peers in the multicast group */
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#define NUM_PEERS 3
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/* Pre-shared secret components (must be same for all peers) */
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#define PMS_SIZE 48
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#define RANDOM_SIZE 32
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/* Epoch for the multicast session */
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#define MCAST_EPOCH 1
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#if defined(WOLFSSL_DTLS) && defined(WOLFSSL_MULTICAST)
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/* Global flag for clean shutdown */
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static volatile sig_atomic_t running = 1;
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static void sig_handler(int sig)
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{
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(void)sig;
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running = 0;
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}
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/*
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* Setup a multicast UDP socket for sending to the group
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*/
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static int setup_tx_socket(struct sockaddr_in* txAddr)
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{
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int sd;
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unsigned char ttl = 1;
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int on = 1;
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sd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sd < 0) {
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perror("socket (tx)");
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return -1;
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}
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/* Set TTL for multicast */
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if (setsockopt(sd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0) {
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perror("setsockopt IP_MULTICAST_TTL");
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close(sd);
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return -1;
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}
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/* Enable loopback so other processes on same host can receive */
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if (setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, &on, sizeof(on)) < 0) {
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perror("setsockopt IP_MULTICAST_LOOP");
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close(sd);
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return -1;
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}
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/* Setup destination address */
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memset(txAddr, 0, sizeof(*txAddr));
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txAddr->sin_family = AF_INET;
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txAddr->sin_addr.s_addr = inet_addr(MCAST_GROUP);
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txAddr->sin_port = htons(MCAST_PORT);
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/* Connect to multicast address for sending */
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if (connect(sd, (struct sockaddr*)txAddr, sizeof(*txAddr)) < 0) {
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perror("connect (tx)");
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close(sd);
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return -1;
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}
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return sd;
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}
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/*
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* Setup a multicast UDP socket for receiving from the group
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*/
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static int setup_rx_socket(void)
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{
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int sd;
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int on = 1;
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struct sockaddr_in addr;
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struct ip_mreq mreq;
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sd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sd < 0) {
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perror("socket (rx)");
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return -1;
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}
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/* Allow multiple sockets to use the same port */
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if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0) {
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perror("setsockopt SO_REUSEADDR");
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close(sd);
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return -1;
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}
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#ifdef SO_REUSEPORT
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if (setsockopt(sd, SOL_SOCKET, SO_REUSEPORT, &on, sizeof(on)) < 0) {
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perror("setsockopt SO_REUSEPORT");
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close(sd);
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return -1;
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}
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#endif
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/* Bind to multicast port */
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memset(&addr, 0, sizeof(addr));
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addr.sin_family = AF_INET;
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addr.sin_addr.s_addr = htonl(INADDR_ANY);
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addr.sin_port = htons(MCAST_PORT);
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if (bind(sd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
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perror("bind (rx)");
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close(sd);
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return -1;
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}
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/* Join the multicast group */
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mreq.imr_multiaddr.s_addr = inet_addr(MCAST_GROUP);
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mreq.imr_interface.s_addr = htonl(INADDR_ANY);
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if (setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
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perror("setsockopt IP_ADD_MEMBERSHIP");
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close(sd);
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return -1;
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}
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/* Set non-blocking for receive */
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{
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int flags = fcntl(sd, F_GETFL, 0);
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if (flags < 0 || fcntl(sd, F_SETFL, flags | O_NONBLOCK) < 0) {
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perror("fcntl");
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close(sd);
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return -1;
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}
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}
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return sd;
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}
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int main(int argc, char** argv)
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{
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int ret;
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int myId;
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int txSd = -1;
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int rxSd = -1;
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WOLFSSL_CTX* ctx = NULL;
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WOLFSSL* sslTx = NULL;
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WOLFSSL* sslRx = NULL;
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struct sockaddr_in txAddr;
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int i;
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/* Pre-shared secret components - same for all peers */
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unsigned char pms[PMS_SIZE];
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unsigned char clientRandom[RANDOM_SIZE];
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unsigned char serverRandom[RANDOM_SIZE];
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/* WDM-NULL-SHA256 cipher suite bytes */
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unsigned char suite[2] = { 0x00, 0xFE };
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time_t lastSend = 0;
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int msgCount = 0;
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/* Parse arguments */
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if (argc != 2) {
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fprintf(stderr, "Usage: %s <node_id>\n", argv[0]);
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fprintf(stderr, " node_id: 0, 1, or 2\n");
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return 1;
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}
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myId = atoi(argv[1]);
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if (myId < 0 || myId >= NUM_PEERS) {
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fprintf(stderr, "Error: node_id must be 0, 1, or 2\n");
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return 1;
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}
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/* Setup signal handler */
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signal(SIGINT, sig_handler);
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signal(SIGTERM, sig_handler);
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printf("=== DTLS Multicast Peer - Node %d ===\n", myId);
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/* Enable debug output if built with --enable-debug */
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#ifdef DEBUG_WOLFSSL
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wolfSSL_Debugging_ON();
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#endif
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/* Initialize the pre-shared secrets (same for all peers) */
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memset(pms, 0x23, sizeof(pms));
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memset(clientRandom, 0xA5, sizeof(clientRandom));
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memset(serverRandom, 0x5A, sizeof(serverRandom));
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/* Initialize wolfSSL */
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ret = wolfSSL_Init();
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_Init failed: %d\n", ret);
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return 1;
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}
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/* Create DTLS 1.2 context */
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ctx = wolfSSL_CTX_new(wolfDTLSv1_2_client_method());
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if (ctx == NULL) {
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fprintf(stderr, "Error: wolfSSL_CTX_new failed\n");
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goto cleanup;
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}
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/* Set multicast member ID */
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ret = wolfSSL_CTX_mcast_set_member_id(ctx, (unsigned short)myId);
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_CTX_mcast_set_member_id failed: %d\n", ret);
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goto cleanup;
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}
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/* Set multicast cipher suite (NULL cipher with SHA256 for integrity) */
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ret = wolfSSL_CTX_set_cipher_list(ctx, "WDM-NULL-SHA256");
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_CTX_set_cipher_list failed: %d\n", ret);
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fprintf(stderr, "Make sure wolfSSL is built with --enable-mcast\n");
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goto cleanup;
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}
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/* Setup sockets */
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txSd = setup_tx_socket(&txAddr);
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if (txSd < 0) {
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goto cleanup;
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}
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rxSd = setup_rx_socket();
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if (rxSd < 0) {
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goto cleanup;
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}
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printf("Node %d: Sockets ready, joined multicast group %s:%d\n",
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myId, MCAST_GROUP, MCAST_PORT);
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/* Create SSL object for transmitting */
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sslTx = wolfSSL_new(ctx);
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if (sslTx == NULL) {
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fprintf(stderr, "Error: wolfSSL_new (tx) failed\n");
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goto cleanup;
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}
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/* Create SSL object for receiving */
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sslRx = wolfSSL_new(ctx);
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if (sslRx == NULL) {
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fprintf(stderr, "Error: wolfSSL_new (rx) failed\n");
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goto cleanup;
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}
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/* Set socket file descriptors */
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wolfSSL_set_fd(sslTx, txSd);
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wolfSSL_set_fd(sslRx, rxSd);
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/* Set using nonblock for receive */
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wolfSSL_dtls_set_using_nonblock(sslRx, 1);
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/* Add peers for receive tracking BEFORE setting secret.
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* IMPORTANT: wolfSSL_mcast_peer_add() zeros the peer entry, including
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* nextEpoch. wolfSSL_set_secret() sets nextEpoch for all entries.
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* So peers must be added first, then secret set afterward. */
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for (i = 0; i < NUM_PEERS; i++) {
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if (i != myId) {
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ret = wolfSSL_mcast_peer_add(sslRx, (unsigned short)i, 0);
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_mcast_peer_add(%d) failed: %d\n",
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i, ret);
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goto cleanup;
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}
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printf("Node %d: Added peer %d to receive tracking\n", myId, i);
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}
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}
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/* Set the pre-shared secret for both SSL objects.
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* This must be called AFTER adding peers so their nextEpoch gets set. */
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ret = wolfSSL_set_secret(sslTx, MCAST_EPOCH, pms, sizeof(pms),
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clientRandom, serverRandom, suite);
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_set_secret (tx) failed: %d\n", ret);
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goto cleanup;
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}
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ret = wolfSSL_set_secret(sslRx, MCAST_EPOCH, pms, sizeof(pms),
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clientRandom, serverRandom, suite);
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if (ret != WOLFSSL_SUCCESS) {
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fprintf(stderr, "Error: wolfSSL_set_secret (rx) failed: %d\n", ret);
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goto cleanup;
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}
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/* Flush any stale packets from previous runs */
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{
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char discard[MSGLEN];
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struct timeval tv_flush = {0, 0};
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fd_set fds;
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while (1) {
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FD_ZERO(&fds);
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FD_SET(rxSd, &fds);
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if (select(rxSd + 1, &fds, NULL, NULL, &tv_flush) <= 0)
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break;
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if (recv(rxSd, discard, sizeof(discard), 0) <= 0)
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break;
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}
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}
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printf("Node %d: Ready. Press Ctrl+C to exit.\n", myId);
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printf("Node %d: Sending messages every 3 seconds...\n\n", myId);
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/* Main loop */
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while (running) {
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fd_set readfds;
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struct timeval tv;
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time_t now;
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FD_ZERO(&readfds);
|
||||
FD_SET(rxSd, &readfds);
|
||||
tv.tv_sec = 1;
|
||||
tv.tv_usec = 0;
|
||||
|
||||
ret = select(rxSd + 1, &readfds, NULL, NULL, &tv);
|
||||
if (ret < 0) {
|
||||
if (errno == EINTR) continue;
|
||||
perror("select");
|
||||
break;
|
||||
}
|
||||
|
||||
/* Check for incoming messages */
|
||||
if (ret > 0 && FD_ISSET(rxSd, &readfds)) {
|
||||
unsigned char buf[MSGLEN];
|
||||
unsigned short peerId = 0;
|
||||
int recvLen;
|
||||
|
||||
recvLen = wolfSSL_mcast_read(sslRx, &peerId, buf, sizeof(buf) - 1);
|
||||
if (recvLen > 0) {
|
||||
/* Ignore our own messages (loopback) */
|
||||
if (peerId != (unsigned short)myId) {
|
||||
buf[recvLen] = '\0';
|
||||
printf("Node %d: Received from peer %d: \"%s\"\n",
|
||||
myId, peerId, buf);
|
||||
}
|
||||
}
|
||||
else if (recvLen < 0) {
|
||||
int err = wolfSSL_get_error(sslRx, recvLen);
|
||||
if (err != WOLFSSL_ERROR_WANT_READ) {
|
||||
/* Ignore decryption errors from our own packets */
|
||||
if (err != DECRYPT_ERROR && err != VERIFY_MAC_ERROR) {
|
||||
char errStr[80];
|
||||
wolfSSL_ERR_error_string(err, errStr);
|
||||
fprintf(stderr, "Node %d: Read error: %s (%d)\n",
|
||||
myId, errStr, err);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* Send a message every 3 seconds */
|
||||
now = time(NULL);
|
||||
if (now - lastSend >= 3) {
|
||||
char msg[MSGLEN];
|
||||
int writeLen;
|
||||
|
||||
snprintf(msg, sizeof(msg), "Hello from node %d, message #%d",
|
||||
myId, ++msgCount);
|
||||
|
||||
writeLen = wolfSSL_write(sslTx, msg, (int)strlen(msg));
|
||||
if (writeLen > 0) {
|
||||
printf("Node %d: Sent: \"%s\"\n", myId, msg);
|
||||
}
|
||||
else {
|
||||
int err = wolfSSL_get_error(sslTx, writeLen);
|
||||
char errStr[80];
|
||||
wolfSSL_ERR_error_string(err, errStr);
|
||||
fprintf(stderr, "Node %d: Write error: %s (%d)\n",
|
||||
myId, errStr, err);
|
||||
}
|
||||
|
||||
lastSend = now;
|
||||
}
|
||||
}
|
||||
|
||||
printf("\nNode %d: Shutting down...\n", myId);
|
||||
|
||||
cleanup:
|
||||
if (sslTx != NULL) {
|
||||
wolfSSL_free(sslTx);
|
||||
}
|
||||
if (sslRx != NULL) {
|
||||
wolfSSL_free(sslRx);
|
||||
}
|
||||
if (ctx != NULL) {
|
||||
wolfSSL_CTX_free(ctx);
|
||||
}
|
||||
if (rxSd >= 0) {
|
||||
/* Leave multicast group */
|
||||
struct ip_mreq mreq;
|
||||
mreq.imr_multiaddr.s_addr = inet_addr(MCAST_GROUP);
|
||||
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
|
||||
setsockopt(rxSd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
|
||||
close(rxSd);
|
||||
}
|
||||
if (txSd >= 0) {
|
||||
close(txSd);
|
||||
}
|
||||
wolfSSL_Cleanup();
|
||||
|
||||
printf("Node %d: Goodbye!\n", myId);
|
||||
return 0;
|
||||
}
|
||||
#else
|
||||
int main()
|
||||
{
|
||||
fprintf(stderr, "Please configure the wolfssl library with --enable-dtls --enable-mcast.\n");
|
||||
return EXIT_FAILURE;
|
||||
}
|
||||
#endif /* WOLFSSL_DTLS && WOLFSSL_MULTICAST */
|
||||
Loading…
Reference in New Issue