From b2ef28fa0a50391bebb15907d4e81cb05d192eb5 Mon Sep 17 00:00:00 2001
From: Andrea Franz <andrea@gravityblast.com>
Date: Fri, 14 Sep 2018 13:30:16 +0200
Subject: [PATCH] add command and response structs

---
 apdu/command.go       | 60 +++++++++++++++++++++++++++++++++++++++++++
 apdu/command_test.go  | 43 +++++++++++++++++++++++++++++++
 apdu/response.go      | 46 +++++++++++++++++++++++++++++++++
 apdu/response_test.go | 26 +++++++++++++++++++
 4 files changed, 175 insertions(+)
 create mode 100644 apdu/command.go
 create mode 100644 apdu/command_test.go
 create mode 100644 apdu/response.go
 create mode 100644 apdu/response_test.go

diff --git a/apdu/command.go b/apdu/command.go
new file mode 100644
index 0000000..1d76f61
--- /dev/null
+++ b/apdu/command.go
@@ -0,0 +1,60 @@
+package apdu
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+type Command struct {
+	Cla  uint8
+	Ins  uint8
+	P1   uint8
+	P2   uint8
+	Data []byte
+	Le   uint8
+}
+
+func NewCommand(cla, ins, p1, p2 uint8, data []byte) *Command {
+	return &Command{
+		Cla:  cla,
+		Ins:  ins,
+		P1:   p1,
+		P2:   p2,
+		Data: data,
+	}
+}
+
+func (c *Command) serialize() ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	if err := binary.Write(buf, binary.BigEndian, c.Cla); err != nil {
+		return nil, err
+	}
+
+	if err := binary.Write(buf, binary.BigEndian, c.Ins); err != nil {
+		return nil, err
+	}
+
+	if err := binary.Write(buf, binary.BigEndian, c.P1); err != nil {
+		return nil, err
+	}
+
+	if err := binary.Write(buf, binary.BigEndian, c.P2); err != nil {
+		return nil, err
+	}
+
+	if len(c.Data) > 0 {
+		if err := binary.Write(buf, binary.BigEndian, uint8(len(c.Data))); err != nil {
+			return nil, err
+		}
+		if err := binary.Write(buf, binary.BigEndian, c.Data); err != nil {
+			return nil, err
+		}
+	}
+
+	if err := binary.Write(buf, binary.BigEndian, c.Le); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
diff --git a/apdu/command_test.go b/apdu/command_test.go
new file mode 100644
index 0000000..2fe13bc
--- /dev/null
+++ b/apdu/command_test.go
@@ -0,0 +1,43 @@
+package apdu
+
+import (
+	"encoding/hex"
+	"fmt"
+	"log"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func hexToBytes(s string) []byte {
+	b := make([]byte, hex.DecodedLen(len(s)))
+	_, err := hex.Decode(b, []byte(s))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return b[:]
+}
+
+func bytesToHexWithSpaces(b []byte) string {
+	return fmt.Sprintf("% X", b)
+}
+
+func bytesToHex(b []byte) string {
+	return fmt.Sprintf("%X", b)
+}
+
+func TestNewCommand(t *testing.T) {
+	var cla uint8 = 0x80
+	var ins uint8 = 0x50
+	var p1 uint8 = 1
+	var p2 uint8 = 2
+	data := hexToBytes("84762336c5187fe8")
+
+	cmd := NewCommand(cla, ins, p1, p2, data)
+	expected := "80 50 01 02 08 84 76 23 36 C5 18 7F E8 00"
+
+	result, err := cmd.serialize()
+	assert.NoError(t, err)
+	assert.Equal(t, expected, bytesToHexWithSpaces(result))
+}
diff --git a/apdu/response.go b/apdu/response.go
new file mode 100644
index 0000000..f2f0878
--- /dev/null
+++ b/apdu/response.go
@@ -0,0 +1,46 @@
+package apdu
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+)
+
+type Response struct {
+	Data []byte
+	Sw1  uint8
+	Sw2  uint8
+	Sw   uint16
+}
+
+var ErrBadRawResponse = errors.New("response data must be at least 2 bytes")
+
+func (r *Response) deserialize(data []byte) error {
+	if len(data) < 2 {
+		return ErrBadRawResponse
+	}
+
+	r.Data = make([]byte, len(data)-2)
+	buf := bytes.NewReader(data)
+
+	if err := binary.Read(buf, binary.BigEndian, &r.Data); err != nil {
+		return err
+	}
+
+	if err := binary.Read(buf, binary.BigEndian, &r.Sw1); err != nil {
+		return err
+	}
+
+	if err := binary.Read(buf, binary.BigEndian, &r.Sw2); err != nil {
+		return err
+	}
+
+	r.Sw = (uint16(r.Sw1) << 8) | uint16(r.Sw2)
+
+	return nil
+}
+
+func ParseResponse(data []byte) (*Response, error) {
+	r := &Response{}
+	return r, r.deserialize(data)
+}
diff --git a/apdu/response_test.go b/apdu/response_test.go
new file mode 100644
index 0000000..8e27c51
--- /dev/null
+++ b/apdu/response_test.go
@@ -0,0 +1,26 @@
+package apdu
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseResponse(t *testing.T) {
+	raw := hexToBytes("000002650183039536622002003b5e508f751c0af3016e3fbc23d3a69000")
+	resp, err := ParseResponse(raw)
+
+	assert.NoError(t, err)
+	assert.Equal(t, uint8(0x90), resp.Sw1)
+	assert.Equal(t, uint8(0x00), resp.Sw2)
+	assert.Equal(t, uint16(0x9000), resp.Sw)
+
+	expected := "000002650183039536622002003B5E508F751C0AF3016E3FBC23D3A6"
+	assert.Equal(t, expected, bytesToHex(resp.Data))
+}
+
+func TestParseResponse_BadData(t *testing.T) {
+	raw := hexToBytes("")
+	_, err := ParseResponse(raw)
+	assert.Equal(t, ErrBadRawResponse, err)
+}