RFM69 hat library Part10

Encryption: Rasmatic/RFM69-Arduino-Library

The RFM69CW/RFM69HCW modules (based on the Semtech SX1231/SX1231H) have built in support for AES128 encryption. In this test harness I’m exploring the RFM69 AES128 implementation.

In the Arduino code I found the order of initialisation was critical. Because of the way the Rasmatic library is written the call to vRF69SetAesKey has to be after the vInitialize.

void setup() 
{
  Serial.begin(9600);

  pinMode(SENDER_DETECT_PIN, INPUT_PULLUP);  
  
  radio.Modulation     = FSK;
  radio.COB            = RFM69;
  radio.Frequency      = 915000;
  radio.OutputPower    = 10+18;          //10dBm OutputPower
  radio.PreambleLength = 16;             //16Byte preamble
  radio.FixedPktLength = false;          //packet in message which need to be send
  radio.CrcDisable     = false;          //CRC On
  radio.AesOn          = false;
  radio.SymbolTime     = 416000;         //2.4Kbps
  radio.Devation       = 35;             //35KHz for devation
  radio.BandWidth      = 100;            //100KHz for bandwidth
  radio.SyncLength     = 3;              //
  radio.SyncWord[0]    = 0xAA;
  radio.SyncWord[1]    = 0x2D;
  radio.SyncWord[2]    = 0xD4;

  // Highly secure 16byte fixed length key
  radio.AesKey[0] = 0x0;
  radio.AesKey[1] = 0x1;
  radio.AesKey[2] = 0x2;
  radio.AesKey[3] = 0x3;
  radio.AesKey[4] = 0x4;
  radio.AesKey[5] = 0x5;
  radio.AesKey[6] = 0x6;
  radio.AesKey[7] = 0x7;
  radio.AesKey[8] = 0x8;
  radio.AesKey[9] = 0x9;
  radio.AesKey[10] = 0xA;
  radio.AesKey[11] = 0xB;
  radio.AesKey[12] = 0xC;
  radio.AesKey[13] = 0xD;
  radio.AesKey[14] = 0xE;
  radio.AesKey[15] = 0xF;
  radio.AesOn = true ;

  radio.vInitialize();

  radio.vRF69SetAesKey();

When I first fired up the Arduino client on the Windows 10 IoT Core device I hadn’t configured the AES key but had enabled encryption.

19:21:25 Received 13 byte message =!{��>�_��5
19:21:26.114 RegIrqFlags 01000110
19:21:26 Received 13 byte message ���gǺm,0|��
19:21:26.273 Send-Done
19:21:26.453 RegIrqFlags 00001000
19:21:26.467 Transmit-Done
19:21:27.244 RegIrqFlags 01000110
19:21:27 Received 13 byte message w6�H�Y���#"#
19:21:28.373 RegIrqFlags 01000110
19:21:28 Received 13 byte message c�u�$mԙ���M{
...
Restart Arduino client
...
19:21:34.836 RegIrqFlags 01000110
19:21:34 Received 13 byte message ���gǺm,0|��
19:21:35.965 RegIrqFlags 01000110
19:21:35 Received 13 byte message w6�H�Y���#"#
19:21:36.429 Send-Done
19:21:36.610 RegIrqFlags 00001000
19:21:36.624 Transmit-Done
19:21:37.095 RegIrqFlags 01000110
19:21:37 Received 13 byte message c�u�$mԙ���M{
The program '[1560] backgroundTaskHost.exe' has exited with code -1 (0xffffffff).

When I restarted the Arduino client I got the same sequences of characters in the messages so it looks like the RFM69 encryption is most probably using electronic code book (ECB) rather than a mode with a changing initialisation vector(IV) e.g. cypher block chaining(CBC). (which wasn’t a surprise)

After modifying the Windows 10 IoT Core application to receive and transmit encrypted payloads

/*
    Copyright ® 2019 July devMobile Software, All Rights Reserved

	 MIT License

	 Permission is hereby granted, free of charge, to any person obtaining a copy
	 of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
	 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	 copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all
	 copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	 SOFTWARE

 */
namespace devMobile.IoT.Rfm69Hcw.Encryption
{
	using System;
	using System.Diagnostics;
	using System.Runtime.InteropServices.WindowsRuntime;
	using System.Text;
	using System.Threading.Tasks;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Gpio;
	using Windows.Devices.Spi;

	public sealed class Rfm69HcwDevice
	{
		private SpiDevice Rfm69Hcw;
		private GpioPin InterruptGpioPin = null;
		private const byte RegisterAddressReadMask = 0X7f;
		private const byte RegisterAddressWriteMask = 0x80;

		public Rfm69HcwDevice(int chipSelectPin, int resetPin, int interruptPin)
		{
			SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
			var settings = new SpiConnectionSettings(chipSelectPin)
			{
				ClockFrequency = 500000,
				Mode = SpiMode.Mode0,
			};

			// Factory reset pin configuration
			GpioController gpioController = GpioController.GetDefault();
			GpioPin resetGpioPin = gpioController.OpenPin(resetPin);
			resetGpioPin.SetDriveMode(GpioPinDriveMode.Output);
			resetGpioPin.Write(GpioPinValue.High);
			Task.Delay(100);
			resetGpioPin.Write(GpioPinValue.Low);
			Task.Delay(10);

			// Interrupt pin for RX message & TX done notification 
			InterruptGpioPin = gpioController.OpenPin(interruptPin);
			resetGpioPin.SetDriveMode(GpioPinDriveMode.Input);

			InterruptGpioPin.ValueChanged += InterruptGpioPin_ValueChanged;

			Rfm69Hcw = spiController.GetDevice(settings);
		}

		private void InterruptGpioPin_ValueChanged(GpioPin sender, GpioPinValueChangedEventArgs args)
		{
			if (args.Edge != GpioPinEdge.RisingEdge)
			{
				return;
			}

			byte irqFlags = this.RegisterReadByte(0x28); // RegIrqFlags2
			Debug.WriteLine("{0:HH:mm:ss.fff} RegIrqFlags {1}", DateTime.Now, Convert.ToString((byte)irqFlags, 2).PadLeft(8, '0'));
			if ((irqFlags & 0b00000100) == 0b00000100)  // PayLoadReady set
			{
				// Read the length of the buffer
				byte numberOfBytes = this.RegisterReadByte(0x0);

				// Allocate buffer for message
				byte[] messageBytes = new byte[numberOfBytes];

				for (int i = 0; i < numberOfBytes; i++)
				{
					messageBytes[i] = this.RegisterReadByte(0x00); // RegFifo
				}

				string messageText = UTF8Encoding.UTF8.GetString(messageBytes);
				Debug.WriteLine("{0:HH:mm:ss} Received {1} byte message {2}", DateTime.Now, messageBytes.Length, messageText);
			}

			if ((irqFlags & 0b00001000) == 0b00001000)  // PacketSent set
			{
				this.RegisterWriteByte(0x01, 0b00010000); // RegOpMode set ReceiveMode
				Debug.WriteLine("{0:HH:mm:ss.fff} Transmit-Done", DateTime.Now);
			}
		}

		public Byte RegisterReadByte(byte address)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[1];
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.TransferSequential(writeBuffer, readBuffer);

			return readBuffer[0];
		}

		public byte[] RegisterRead(byte address, int length)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[length];
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.TransferSequential(writeBuffer, readBuffer);

			return readBuffer;
		}

		public void RegisterWriteByte(byte address, byte value)
		{
			byte[] writeBuffer = new byte[] { address |= RegisterAddressWriteMask, value };
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.Write(writeBuffer);
		}

		public void RegisterWrite(byte address, [ReadOnlyArray()] byte[] bytes)
		{
			byte[] writeBuffer = new byte[1 + bytes.Length];
			Debug.Assert(Rfm69Hcw != null);

			Array.Copy(bytes, 0, writeBuffer, 1, bytes.Length);
			writeBuffer[0] = address |= RegisterAddressWriteMask;

			Rfm69Hcw.Write(writeBuffer);
		}

		public void RegisterDump()
		{
			Debug.WriteLine("Register dump");
			for (byte registerIndex = 0; registerIndex <= 0x3D; registerIndex++)
			{
				byte registerValue = this.RegisterReadByte(registerIndex);

				Debug.WriteLine("Register 0x{0:x2} - Value 0X{1:x2} - Bits {2}", registerIndex, registerValue, Convert.ToString(registerValue, 2).PadLeft(8, '0'));
			}
		}
	}


	public sealed class StartupTask : IBackgroundTask
	{
		private const int ChipSelectLine = 1;
		private const int ResetPin = 25;
		private const int InterruptPin = 22;
		private Rfm69HcwDevice rfm69Device = new Rfm69HcwDevice(ChipSelectLine, ResetPin, InterruptPin);

		const double RH_RF6M9HCW_FXOSC = 32000000.0;
		const double RH_RFM69HCW_FSTEP = RH_RF6M9HCW_FXOSC / 524288.0;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			//rfm69Device.RegisterDump();

			// regOpMode standby
			rfm69Device.RegisterWriteByte(0x01, 0b00000100);

			// BitRate MSB/LSB
			rfm69Device.RegisterWriteByte(0x03, 0x34);
			rfm69Device.RegisterWriteByte(0x04, 0x00);

			// Frequency deviation
			rfm69Device.RegisterWriteByte(0x05, 0x02);
			rfm69Device.RegisterWriteByte(0x06, 0x3d);

			// Calculate the frequency accoring to the datasheett
			byte[] bytes = BitConverter.GetBytes((uint)(915000000.0 / RH_RFM69HCW_FSTEP));
			Debug.WriteLine("Byte Hex 0x{0:x2} 0x{1:x2} 0x{2:x2} 0x{3:x2}", bytes[0], bytes[1], bytes[2], bytes[3]);
			rfm69Device.RegisterWriteByte(0x07, bytes[2]);
			rfm69Device.RegisterWriteByte(0x08, bytes[1]);
			rfm69Device.RegisterWriteByte(0x09, bytes[0]);

			// RegRxBW
			rfm69Device.RegisterWriteByte(0x19, 0x2a);

			// RegDioMapping1
			rfm69Device.RegisterWriteByte(0x26, 0x01);

			// Setup preamble length to 16 (default is 3) RegPreambleMsb RegPreambleLsb
			rfm69Device.RegisterWriteByte(0x2C, 0x0);
			rfm69Device.RegisterWriteByte(0x2D, 0x10);

			// RegSyncConfig Set the Sync length and byte values SyncOn + 3 custom sync bytes
			rfm69Device.RegisterWriteByte(0x2e, 0x90);

			// RegSyncValues1 thru RegSyncValues3
			rfm69Device.RegisterWriteByte(0x2f, 0xAA);
			rfm69Device.RegisterWriteByte(0x30, 0x2D);
			rfm69Device.RegisterWriteByte(0x31, 0xD4);

			// RegPacketConfig1 Variable length with CRC on
			rfm69Device.RegisterWriteByte(0x37, 0x90);

			// Set the AES key and turn on AES RegPacketConfig2
			rfm69Device.RegisterWriteByte(0x3D, 0x03);
	
			rfm69Device.RegisterWriteByte(0x3E, 0x00);
			rfm69Device.RegisterWriteByte(0x3F, 0x01);
			rfm69Device.RegisterWriteByte(0x40, 0x02);
			rfm69Device.RegisterWriteByte(0x41, 0x03);
			rfm69Device.RegisterWriteByte(0x42, 0x04);
			rfm69Device.RegisterWriteByte(0x43, 0x05);
			rfm69Device.RegisterWriteByte(0x44, 0x06);
			rfm69Device.RegisterWriteByte(0x45, 0x07);
			rfm69Device.RegisterWriteByte(0x46, 0x08);
			rfm69Device.RegisterWriteByte(0x47, 0x09);
			rfm69Device.RegisterWriteByte(0x48, 0x0A);
			rfm69Device.RegisterWriteByte(0x49, 0x0B);
			rfm69Device.RegisterWriteByte(0x4A, 0x0C);
			rfm69Device.RegisterWriteByte(0x4B, 0x0D);
			rfm69Device.RegisterWriteByte(0x4C, 0x0E);
			rfm69Device.RegisterWriteByte(0x4D, 0x0F);
			
/*
			// Clear out the AES key
			rfm69Device.RegisterWriteByte(0x3E, 0x0);
			rfm69Device.RegisterWriteByte(0x3F, 0x0);
			rfm69Device.RegisterWriteByte(0x40, 0x0);
			rfm69Device.RegisterWriteByte(0x41, 0x0);
			rfm69Device.RegisterWriteByte(0x42, 0x0);
			rfm69Device.RegisterWriteByte(0x43, 0x0);
			rfm69Device.RegisterWriteByte(0x44, 0x0);
			rfm69Device.RegisterWriteByte(0x45, 0x0);
			rfm69Device.RegisterWriteByte(0x46, 0x0);
			rfm69Device.RegisterWriteByte(0x47, 0x0);
			rfm69Device.RegisterWriteByte(0x48, 0x0);
			rfm69Device.RegisterWriteByte(0x49, 0x0);
			rfm69Device.RegisterWriteByte(0x4A, 0x0);
			rfm69Device.RegisterWriteByte(0x4B, 0x0);
			rfm69Device.RegisterWriteByte(0x4C, 0x0);
			rfm69Device.RegisterWriteByte(0x4D, 0x0);
*/			

			rfm69Device.RegisterDump();

			while (true)
			{
				// Standby mode while loading message into FIFO
				rfm69Device.RegisterWriteByte(0x01, 0b00000100);

				byte[] messageBuffer = UTF8Encoding.UTF8.GetBytes("hello world " + DateTime.Now.ToLongTimeString());
				rfm69Device.RegisterWriteByte(0x0, (byte)messageBuffer.Length);
				rfm69Device.RegisterWrite(0x0, messageBuffer);

				// Transmit mode once FIFO loaded
				rfm69Device.RegisterWriteByte(0x01, 0b00001100);

				Debug.WriteLine("{0:HH:mm:ss.fff} Send-Done", DateTime.Now);

				Task.Delay(5000).Wait();
			}
		}
	}
}

I could see inbound messages from the transmit Arduino and Windows 10 device interleaved on the receive Arduino.

21:06:12.735 -> RX start
21:06:12.735 -> 0x0: 0x0
21:06:12.769 -> 0x1: 0x10
21:06:12.769 -> 0x2: 0x0
…
21:06:13.453 -> 0x3B: 0x0
21:06:13.453 -> 0x3C: 0x1
21:06:13.487 -> 0x3D: 0x1
21:06:15.218 -> MessageIn:hello world 9:06:15 PM
21:06:20.317 -> MessageIn:hello world 9:06:20 PM
21:06:24.559 -> MessageIn:Hello world:0
21:06:25.384 -> MessageIn:hello world 9:06:25 PM
21:06:28.009 -> MessageIn:Hello world:1
21:06:30.454 -> MessageIn:hello world 9:06:30 PM
21:06:31.455 -> MessageIn:Hello world:2
21:06:34.939 -> MessageIn:Hello world:3
21:06:35.596 -> MessageIn:hello world 9:06:35 PM
21:06:38.389 -> MessageIn:Hello world:4
21:06:40.666 -> MessageIn:hello world 9:06:40 PM
21:06:41.838 -> MessageIn:Hello world:5
21:06:45.316 -> MessageIn:Hello world:6
21:06:45.731 -> MessageIn:hello world 9:06:45 PM
21:06:48.761 -> MessageIn:Hello world:7
21:06:50.799 -> MessageIn:hello world 9:06:50 PM
21:06:52.214 -> MessageIn:Hello world:8

The next step will be merging and refactoring the test harness to extract the code for accessing the RFM69 registers into a separate class, then defining enumerations and constants for all the RFM69 settings.

Netduino 3 Wifi Azure Service Bus client certificate issue

A few months ago I wrote a post about using a Netduino 3 wifi device to push data to an Azure Event Hub. Last week I wanted to reuse some of the code for another gateway I was building but it didn’t appear to work. When my application made an HTTPS request to the service bus endpoint of my Event Hub it failed with an exception. Initially I though it might be a problem with wildcard certificates so I build a small demo program which makes three HTTPS requests to endpoints with different certificate configurations (for more detail see the code below).

using System;
using System.Net;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Net.NetworkInformation;

namespace devMobile.Netduino3WifiCertificateQuery
{
   public class Program
   {
      public static void Main()
      {
         // Wait for Network address if DHCP
         NetworkInterface networkInterface = NetworkInterface.GetAllNetworkInterfaces()[0];
         if (networkInterface.IsDhcpEnabled)
         {
            Debug.Print(" Waiting for IP address ");
            while (NetworkInterface.GetAllNetworkInterfaces()[0].IPAddress == IPAddress.Any.ToString())
            {
               Debug.Print(".");
               Thread.Sleep(250);
            }
         }

         // Baseline check with google
         Debug.Print("https://www.google.co.nz");
         try
         {
            using (HttpWebRequest request = (HttpWebRequest)WebRequest.Create(@"https://www.google.co.nz"))
            {
               request.Method = "GET";
               request.KeepAlive = false;
               request.Timeout = 5000;
               request.ReadWriteTimeout = 5000;
               request.KeepAlive = false;

               using (var response = (HttpWebResponse)request.GetResponse())
               {
                  Debug.Print("HTTP Status:" + response.StatusCode + " : " + response.StatusDescription);
               }
            }
         }
         catch (Exception ex)
         {
            Debug.Print(ex.Message);
         }

         /*
         DNS Name=*.wordpress.com
         DNS Name=wordpress.com
         */
         Debug.Print("https://wordpress.wordpress.com/");
         try
         {
            using (HttpWebRequest request = (HttpWebRequest)WebRequest.Create(@"https://wordpress.wordpress.com/"))
            {
               //request.Proxy = proxy; 
               request.Method = "GET";
               request.KeepAlive = false;
               request.Timeout = 5000;
               request.ReadWriteTimeout = 5000;
               request.KeepAlive = false;


               using (var response = (HttpWebResponse)request.GetResponse())
               {
                  Debug.Print("HTTP Status:" + response.StatusCode + " : " + response.StatusDescription);
               }
            }
         }
         catch (Exception ex)
         {
            Debug.Print(ex.Message);
         }


         /*
         DNS Name=*.servicebus.windows.net
         DNS Name=servicebus.windows.net
         */
         Debug.Print(@"https://myhomemonitor.servicebus.windows.net/");
         try
         {
            using (HttpWebRequest request = (HttpWebRequest)WebRequest.Create(@"https://myhomemonitor.servicebus.windows.net/"))
            {
               //request.Proxy = proxy; 
               request.Method = "GET";
               request.KeepAlive = false;
               request.Timeout = 5000;
               request.ReadWriteTimeout = 5000;
               request.KeepAlive = false;

               using (var response = (HttpWebResponse)request.GetResponse())
               {
                  Debug.Print("HTTP Status:" + response.StatusCode + " : " + response.StatusDescription);
               }
            }
         }
         catch (Exception ex)
         {
            Debug.Print(ex.Message);
         }
      }
   }
}

I then noticed that when I looked at the certificate details of the endpoint where the requests were failing in Google Chrome (only occurred in Chrome) there was a warming about “obsolete cryptography”.

Google Chrome info about ok certificate

Google Chrome info about ok certificate

Google Chrome info about error causing certificate

Google Chrome info about possibly error causing certificate

I have downloaded the Netduino 3 Wifi IP stack code from github and have traced down to the native interop call which appears to be failing at the very bottom of the stack. My post at Netduino.com has additional detail about my debugging efforts.

Now I’m wondering if the crypto required by newish certificate for the service bus endpoint is not supported/needs to be enabled for the TI CC3100 SimpleLink Wifi network processor.

 

HTTPS with NetMF calling an Azure Service Bus endpoint

Back in Q1 of 2013 I posted a sample application which called an Azure Service Bus end point just to confirm that the certificate configuration etc. was good.

Since I published that sample the Azure Root certificate has been migrated so I have created a new project which uses the Baltimore Cyber Trust Root certificate.

The sample Azure ServiceBus client uses a wired LAN connection (original one used wifi module) and to run it locally you will have to update the Date information around line 24.