Wrap serial

go.mod

@@ -7,9 +7,11 @@ require (
 	github.com/arduino/iot-client-go v1.3.3
 	github.com/bcmi-labs/oniudra-cli v0.15.8
 	github.com/eclipse/paho.mqtt.golang v1.3.2
+	github.com/howeyc/crc16 v0.0.0-20171223171357-2b2a61e366a6
 	github.com/juju/errors v0.0.0-20200330140219-3fe23663418f
 	github.com/sirupsen/logrus v1.8.1
 	github.com/spf13/cobra v1.1.3
+	go.bug.st/serial v1.3.0
 	golang.org/x/net v0.0.0-20210505024714-0287a6fb4125 // indirect
 	golang.org/x/oauth2 v0.0.0-20210628180205-a41e5a781914
 	golang.org/x/sys v0.0.0-20210503173754-0981d6026fa6 // indirect

go.sum

@@ -136,6 +136,8 @@ github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/creack/goselect v0.1.1/go.mod h1:a/NhLweNvqIYMuxcMOuWY516Cimucms3DglDzQP3hKY=
+github.com/creack/goselect v0.1.2 h1:2DNy14+JPjRBgPzAd1thbQp4BSIihxcBf0IXhQXDRa0=
+github.com/creack/goselect v0.1.2/go.mod h1:a/NhLweNvqIYMuxcMOuWY516Cimucms3DglDzQP3hKY=
 github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/daaku/go.zipexe v1.0.0/go.mod h1:z8IiR6TsVLEYKwXAoE/I+8ys/sDkgTzSL0CLnGVd57E=
@@ -295,6 +297,8 @@ github.com/hashicorp/logutils v1.0.0/go.mod h1:QIAnNjmIWmVIIkWDTG1z5v++HQmx9WQRO
 github.com/hashicorp/mdns v1.0.0/go.mod h1:tL+uN++7HEJ6SQLQ2/p+z2pH24WQKWjBPkE0mNTz8vQ=
 github.com/hashicorp/memberlist v0.1.3/go.mod h1:ajVTdAv/9Im8oMAAj5G31PhhMCZJV2pPBoIllUwCN7I=
 github.com/hashicorp/serf v0.8.2/go.mod h1:6hOLApaqBFA1NXqRQAsxw9QxuDEvNxSQRwA/JwenrHc=
+github.com/howeyc/crc16 v0.0.0-20171223171357-2b2a61e366a6 h1:IIVxLyDUYErC950b8kecjoqDet8P5S4lcVRUOM6rdkU=
+github.com/howeyc/crc16 v0.0.0-20171223171357-2b2a61e366a6/go.mod h1:JslaLRrzGsOKJgFEPBP65Whn+rdwDQSk0I0MCRFe2Zw=
 github.com/howeyc/gopass v0.0.0-20170109162249-bf9dde6d0d2c/go.mod h1:lADxMC39cJJqL93Duh1xhAs4I2Zs8mKS89XWXFGp9cs=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
@@ -501,6 +505,8 @@ go.bug.st/cleanup v1.0.0/go.mod h1:EqVmTg2IBk4znLbPD28xne3abjsJftMdqqJEjhn70bk=
 go.bug.st/downloader/v2 v2.1.1/go.mod h1:VZW2V1iGKV8rJL2ZEGIDzzBeKowYv34AedJz13RzVII=
 go.bug.st/relaxed-semver v0.0.0-20190922224835-391e10178d18/go.mod h1:Cx1VqMtEhE9pIkEyUj3LVVVPkv89dgW8aCKrRPDR/uE=
 go.bug.st/serial v1.1.2/go.mod h1:VmYBeyJWp5BnJ0tw2NUJHZdJTGl2ecBGABHlzRK1knY=
+go.bug.st/serial v1.3.0 h1:liPN6f/Xk0qaUByg0H2LOSns+2RuAuNXmXZyQOLVwVE=
+go.bug.st/serial v1.3.0/go.mod h1:8TT7u/SwwNIpJ8QaG4s+HTjFt9ReXs2cdOU7ZEk50Dk=
 go.bug.st/serial.v1 v0.0.0-20180827123349-5f7892a7bb45/go.mod h1:dRSl/CVCTf56CkXgJMDOdSwNfo2g1orOGE/gBGdvjZw=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.mozilla.org/gopgagent v0.0.0-20170926210634-4d7ea76ff71a/go.mod h1:YDKUvO0b//78PaaEro6CAPH6NqohCmL2Cwju5XI2HoE=

internal/serial/protocol.go

@@ -0,0 +1,53 @@
+package serial
+
+var (
+	// msgStart is the initial byte sequence of every packet
+	msgStart = [2]byte{0x55, 0xAA}
+	// msgEnd is the final byte sequence of every packet
+	msgEnd = [2]byte{0xAA, 0x55}
+)
+
+const (
+	// Position of payload field
+	payloadField = 5
+	// Position of payload length field
+	payloadLenField = 3
+	// Length of payload length field
+	payloadLenFieldLen = 2
+	// Length of the signature field
+	crcFieldLen = 2
+)
+
+// MsgType indicates the type of the packet
+type MsgType byte
+
+const (
+	None MsgType = iota
+	Cmd
+	Data
+	Response
+)
+
+// Command indicates the command that should be
+// executed on the board to be provisioned.
+type Command byte
+
+const (
+	SketchInfo Command = iota + 1
+	CSR
+	Locked
+	GetLocked
+	WriteCrypto
+	BeginStorage
+	SetDeviceID
+	SetYear
+	SetMonth
+	SetDay
+	SetHour
+	SetValidity
+	SetCertSerial
+	SetAuthKey
+	SetSignature
+	EndStorage
+	ReconstructCert
+)

internal/serial/serial.go

@@ -0,0 +1,155 @@
+package serial
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/howeyc/crc16"
+	"go.bug.st/serial"
+)
+
+// Serial is a wrapper of serial port interface that
+// features specific functions to send provisioning
+// commands through the serial port to an arduino device.
+type Serial struct {
+	port serial.Port
+}
+
+// NewSerial instantiate and returns a Serial instance.
+// The Serial Connect method should be called before using
+// its send/receive functions.
+func NewSerial() *Serial {
+	s := &Serial{}
+	return s
+}
+
+// Connect tries to connect Serial to a specific serial port.
+func (s *Serial) Connect(address string) error {
+	mode := &serial.Mode{
+		BaudRate: 57600,
+	}
+	port, err := serial.Open(address, mode)
+	if err != nil {
+		err = fmt.Errorf("%s: %w", "connecting to serial port", err)
+		return err
+	}
+	s.port = port
+
+	s.port.SetReadTimeout(time.Millisecond * 2000)
+	return nil
+}
+
+// Send allows to send a provisioning command to a connected arduino device.
+func (s *Serial) Send(cmd Command, payload []byte) error {
+	payload = append([]byte{byte(cmd)}, payload...)
+	msg := encode(Cmd, payload)
+
+	_, err := s.port.Write(msg)
+	if err != nil {
+		err = fmt.Errorf("%s: %w", "sending message through serial", err)
+		return err
+	}
+
+	return nil
+}
+
+// SendReceive allows to send a provisioning command to a connected arduino device.
+// Then, it waits for a response from the device and, if any, returns it.
+// If no response is received after 2 seconds, an error is returned.
+func (s *Serial) SendReceive(cmd Command, payload []byte) ([]byte, error) {
+	err := s.Send(cmd, payload)
+	if err != nil {
+		return nil, err
+	}
+	return s.receive()
+}
+
+// Close should be used when the Serial connection isn't used anymore.
+// After that, Serial could Connect again to any port.
+func (s *Serial) Close() error {
+	return s.port.Close()
+}
+
+// receive allows to wait for a response from an arduino device under provisioning.
+// Its timeout is set to 2 seconds. It returns an error if the response is not valid
+// or if the timeout expires.
+// TODO: consider refactoring using a more explicit procedure:
+// start := s.Read(buff, MsgStartLength)
+// payloadLen := s.Read(buff, payloadFieldLen)
+func (s *Serial) receive() ([]byte, error) {
+	buff := make([]byte, 1000)
+	var resp []byte
+
+	received := 0
+	payloadLen := 0
+	// Wait to receive the entire packet that is long as the preamble (from msgStart to payload length field)
+	// plus the actual payload length plus the length of the ending sequence.
+	for received < (payloadLenField+payloadLenFieldLen)+payloadLen+len(msgEnd) {
+		n, err := s.port.Read(buff)
+		if err != nil {
+			err = fmt.Errorf("%s: %w", "receiving from serial", err)
+			return nil, err
+		}
+		if n == 0 {
+			break
+		}
+		received += n
+		resp = append(resp, buff[:n]...)
+
+		// Update the payload length as soon as it is received.
+		if payloadLen == 0 && received >= (payloadLenField+payloadLenFieldLen) {
+			payloadLen = int(binary.BigEndian.Uint16(resp[payloadLenField:(payloadLenField + payloadLenFieldLen)]))
+			// TODO: return error if payloadLen is too large.
+		}
+	}
+
+	if received == 0 {
+		err := errors.New("receiving from serial: timeout, nothing received")
+		return nil, err
+	}
+
+	// TODO: check if msgStart is present
+
+	if !bytes.Equal(resp[received-len(msgEnd):], msgEnd[:]) {
+		err := errors.New("receiving from serial: end of message (0xAA, 0x55) not found")
+		return nil, err
+	}
+
+	payload := resp[payloadField : payloadField+payloadLen-crcFieldLen]
+	ch := crc16.Checksum(payload, crc16.CCITTTable)
+	// crc is contained in the last bytes of the payload
+	cp := binary.BigEndian.Uint16(resp[payloadField+payloadLen-crcFieldLen : payloadField+payloadLen])
+	if ch != cp {
+		err := errors.New("receiving from serial: signature of received message is not valid")
+		return nil, err
+	}
+
+	return payload, nil
+}
+
+// encode is internally used to create a valid provisioning packet
+func encode(mType MsgType, msg []byte) []byte {
+	// Insert the preamble sequence followed by the message type
+	packet := append(msgStart[:], byte(mType))
+
+	// Append the packet length
+	bLen := make([]byte, payloadLenFieldLen)
+	binary.BigEndian.PutUint16(bLen, (uint16(len(msg) + crcFieldLen)))
+	packet = append(packet, bLen...)
+
+	// Append the message payload
+	packet = append(packet, msg...)
+
+	// Calculate and append the message signature
+	ch := crc16.Checksum(msg, crc16.CCITTTable)
+	checksum := make([]byte, crcFieldLen)
+	binary.BigEndian.PutUint16(checksum, ch)
+	packet = append(packet, checksum...)
+
+	// Append final byte sequence
+	packet = append(packet, msgEnd[:]...)
+	return packet
+}