karlentwistle/ruby_home

require_relative "application_controller"

module RubyHome
  module HTTP
    class PairVerifiesController < ApplicationController
      post "/" do
        content_type "application/pairing+tlv8"

        verify_accessory_paired

        case unpack_request[:state]
        when 1
          verify_start_response
        when 3
          verify_finish_response
        end
      end

      private

      def verify_start_response
        secret_key = RbNaCl::PrivateKey.generate
        public_key = secret_key.public_key.to_bytes
        client_public_key = RbNaCl::PublicKey.new(unpack_request[:public_key])
        shared_secret = RbNaCl::GroupElement.new(client_public_key).mult(secret_key).to_bytes
        session.shared_secret = shared_secret

        accessoryinfo = [
          public_key.unpack1("H*"),
          accessory_info.device_id.unpack1("H*"),
          client_public_key.to_bytes.unpack1("H*")
        ].join

        signing_key = accessory_info.signing_key
        accessorysignature = signing_key.sign([accessoryinfo].pack("H*"))

        subtlv = tlv(identifier: accessory_info.device_id, signature: accessorysignature)

        hkdf = HAP::Crypto::HKDF.new(info: "Pair-Verify-Encrypt-Info", salt: "Pair-Verify-Encrypt-Salt")
        session_key = hkdf.encrypt(shared_secret)
        session.session_key = session_key

        chacha20poly1305ietf = HAP::Crypto::ChaCha20Poly1305.new(session_key)
        nonce = HexHelper.pad("PV-Msg02")
        encrypted_data = chacha20poly1305ietf.encrypt(nonce, subtlv)

        tlv state: 2, public_key: public_key, encrypted_data: encrypted_data
      end

      def verify_finish_response
        verify_finish = VerifyFinishService.new(
          encrypted_data: unpack_request[:encrypted_data],
          session_key: session.session_key,
          shared_secret: session.shared_secret,
          accessory_info: accessory_info
        ).run

        if verify_finish.success?
          session.controller_to_accessory_key = verify_finish.controller_to_accessory_key
          session.accessory_to_controller_key = verify_finish.accessory_to_controller_key

          session.session_key = nil
          session.shared_secret = nil

          tlv state: 4
        else
          tlv state: 4, error: 2
        end
      end

      def verify_accessory_paired
        halt 403 unless accessory_info.paired?
      end
    end
  end
end