HomeKit Accessory Emulation for Particle / Arduino Development Boards.
Using recently released HomeKit Non-commercial HAP Specification to create an embedded accessory client. Goal of this project is to test C/C++ based SHA-512 based SRP enabled HAP protocols for eventual porting to Particle.io or Arduino libraries. This project contains a Mac OS based XCode project to test embedded code available here: https://github.com/moflo/homekit-particle
This project allows for the testing of embedded C/C++ code for use in Particle / Arduino boards by briding the C/C++ code with high-level Swift and Objective-C based native HomeKit APIs. This Mac OS based application acts as a HomeKit accessory, broadcasting it's presence over Bonjour to be discovered by the iOS Home app. Once discovered, the user starts the pairing process to use the Home app to establish a connection with thie emulator. This process allows for the testing of several C/C++ libraries which can then be used in the embedded device. Specifically, this emulator allows for the testing of the following libraries:
- SRP protocol with N = 3072, g = 5 radix
- ChaCha20_Poly1305 cypher
- ed25519 codec
- sha512 encoding
- HTTP1.1 compliant router
- TLV8 codec
Please note, the TCP and UDP code uses native Mac OS libraries as it is expected that embedded code will use native communication libraries for Particle / Arduino.
Finally, this current implementation uses the crypto library from WolfSSL / WolfCrypto for ARM compatibility. You can find our more about this library online, https://github.com/wolfSSL/wolfssl.
Mac OS based single window utility (ViewContoller.swift) calls Objective-C bridging functions (*.mm) to access C/C++ libraries contained in C++ classes.
- HAPController : HAPContoller.mm / HAPController_Bridge.h
- TLV8 : TLV8_Bridge.mm / TLV8_Bridge.h
- WebClient : WebClient_Bridge.mm / WebClient_Bridge.h
- Swift based testing : homekit-emulatorTests
- macOS 10.10+ (v1.1.2+)
- Xcode 8 with Swift 3
- Cocoapods 1.2.1+
pod install
Using XCode unit testing with Swift Nible library and the Objective-C bridges in the homekit-emulatorTests target. Run individual unit tests within XCode, or via the CLI.
Install Wireshark app, and Bonjour Browser for protocol testing. Save UDP packets on local ethernet channel using the TCPdump command line tool and open the results in Wireshark to test the validity of MDNS packets:
sudo tcpdump -i en0 -s 0 -w ./test.dmp
wireshark -r test.dmp -Y mdns
Use Apple supplied "HomeKit Accessory Simulator" to generate valid MDNS HomeKit packets and use the trace methods above to compare packet & response structure. This provides "blackbox" testing, you can observe valid UDP packet structure but we still need a method to compare use of custom crypto libraries (SHA512, etc.)
Likewise, run this HomeKit Emulator MacOS app to compare MDNS packet structure & reponse protocol. This emulator uses native Cocoa MDNS (ie., NetService) function calls to register a HomeKit accessory, and can be observed within the iOS Home app. Importantly, it then uses 3rd party C/C++ libraries for SRP & Crypto functions so that those libraries can be validated before embedding them in Particle / Arduino project libraries, etc.
HTTP1.1 based pairing process. Initial request from Home app is a POST request to start pairing process...
Text Dump:
POST /pair-setup HTTP/1.1
Host: emulator._hap._tcp.local
Content-Length: 6
Content-Type: application/pairing+tlv8
Hex Dump:
50 4F 53 54 20 2F 70 61 69 72 2D 73 65 74 75 70 20 48 54 54 50 2F 31 2E 31 0D 0A 48 6F 73 74 3A 20 65 6D 75 6C 61 74 6F 72 2E 5F 68 61 70 2E 5F 74 63 70 2E 6C 6F 63 61 6C 0D 0A 43 6F 6E 74 65 6E 74 2D 4C 65 6E 67 74 68 3A 20 36 0D 0A 43 6F 6E 74 65 6E 74 2D 54 79 70 65 3A 20 61 70 70 6C 69 63 61 74 69 6F 6E 2F 70 61 69 72 69 6E 67 2B 74 6C 76 38 0D 0A 0D 0A 00 01 00 06 01 01 00 00
TLV8 Payload: 00 01 00 06 01 01
HAP Encoding:
Type 00 = kTLVType_Method_None
Data 00 = kTLVType_State_None
Type 06 = kTLVType_State
Data 01 = kTLVType_State_M1
Questions:
1, why is this a two-tuple TLV8 payload?
2, why is the second tuple the stat command?
Emulator Response: 48545450 2f312e30 20323030 204f4b0d 0a436f6e 74656e74 2d547970 653a2061 70706c69 63617469 6f6e2f70 61697269 6e672b74 6c76380d 0a436f6e 74656e74 2d4c656e 6774683a 20303030 0d0a0d0a
HTTP/1.1 200 OK
Content-Type: application/pairing+tlv8
Content-Length: 000
Result: Error socketDidDisconnect - "unknown error"
GCDAsyncSocket: Accepted new socket from ( "192.168.15.5", 50932 ):0 GCDAsyncSocket: didRead - ( "126 bytes" ) Write byte count: GCDAsyncSocket: socketDidDisconnect - ( "unknown error" )