add ParseCommand to apdu pkg

apdu/command.go

@@ -3,8 +3,12 @@ package apdu
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 )
 
+// ErrBadRawCommand is an error returned by ParseCommand in case the command data is not long enough.
+var ErrBadRawCommand = errors.New("command must be at least 4 bytes")
+
 // Command struct represent the data sent as an APDU command with CLA, Ins, P1, P2, Lc, Data, and Le.
 type Command struct {
 	Cla        uint8
@@ -76,3 +80,52 @@ func (c *Command) Serialize() ([]byte, error) {
 
 	return buf.Bytes(), nil
 }
+
+func (c *Command) deserialize(data []byte) error {
+	if len(data) < 4 {
+		return ErrBadRawCommand
+	}
+
+	buf := bytes.NewReader(data)
+
+	if err := binary.Read(buf, binary.BigEndian, &c.Cla); err != nil {
+		return err
+	}
+
+	if err := binary.Read(buf, binary.BigEndian, &c.Ins); err != nil {
+		return err
+	}
+
+	if err := binary.Read(buf, binary.BigEndian, &c.P1); err != nil {
+		return err
+	}
+
+	if err := binary.Read(buf, binary.BigEndian, &c.P2); err != nil {
+		return err
+	}
+
+	var lc uint8
+	if err := binary.Read(buf, binary.BigEndian, &lc); err != nil {
+		return nil
+	}
+
+	cmdData := make([]byte, lc)
+	if err := binary.Read(buf, binary.BigEndian, &cmdData); err != nil {
+		return nil
+	}
+	c.Data = cmdData
+
+	var le uint8
+	if err := binary.Read(buf, binary.BigEndian, &le); err != nil {
+		return nil
+	}
+	c.SetLe(le)
+
+	return nil
+}
+
+// ParseCommand parses a raw command and returns a Command
+func ParseCommand(raw []byte) (*Command, error) {
+	cmd := &Command{}
+	return cmd, cmd.deserialize(raw)
+}

apdu/command_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/status-im/keycard-go/hexutils"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestNewCommand(t *testing.T) {
@@ -27,3 +28,16 @@ func TestNewCommand(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, expected, hexutils.BytesToHexWithSpaces(result))
 }
+
+func TestParseCommand(t *testing.T) {
+	raw := hexutils.HexToBytes("0102030402050607")
+	cmd, err := ParseCommand(raw)
+	require.Nil(t, err)
+	assert.Equal(t, uint8(0x01), cmd.Cla)
+	assert.Equal(t, uint8(0x02), cmd.Ins)
+	assert.Equal(t, uint8(0x03), cmd.P1)
+	assert.Equal(t, uint8(0x04), cmd.P2)
+	assert.Equal(t, []byte{0x05, 0x06}, cmd.Data)
+	assert.True(t, cmd.requiresLe)
+	assert.Equal(t, uint8(0x07), cmd.le)
+}