add derivationpath pkg

derivationpath/derivationpath.go

@@ -0,0 +1,214 @@
+package keycard
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+type StartingPoint int
+
+const (
+	tokenMaster    = 0x6D // char m
+	tokenSeparator = 0x2F // char /
+	tokenHardened  = 0x27 // char '
+	tokenDot       = 0x2E // char .
+
+	hardenedStart = 0x80000000 // 2^31
+)
+
+const (
+	StartingPointMaster StartingPoint = iota + 1
+	StartingPointCurrent
+	StartingPointParent
+)
+
+type parseFunc = func() error
+
+type parser struct {
+	r                    *strings.Reader
+	f                    parseFunc
+	pos                  int
+	path                 []uint32
+	start                StartingPoint
+	currentToken         string
+	currentTokenHardened bool
+}
+
+func newParser(path string) *parser {
+	p := &parser{
+		r: strings.NewReader(path),
+	}
+
+	p.reset()
+
+	return p
+}
+
+func (p *parser) reset() {
+	p.r.Seek(0, io.SeekStart)
+	p.pos = 0
+	p.start = StartingPointCurrent
+	p.f = p.parseStart
+	p.path = make([]uint32, 0)
+	p.resetCurrentToken()
+}
+
+func (p *parser) resetCurrentToken() {
+	p.currentToken = ""
+	p.currentTokenHardened = false
+}
+
+func (p *parser) parse() (StartingPoint, []uint32, error) {
+	for {
+		err := p.f()
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+			} else {
+				err = fmt.Errorf("at position %d, %s", p.pos, err.Error())
+			}
+
+			return p.start, p.path, err
+		}
+	}
+
+	return p.start, p.path, nil
+}
+
+func (p *parser) readByte() (byte, error) {
+	b, err := p.r.ReadByte()
+	if err != nil {
+		return b, err
+	}
+
+	p.pos++
+
+	return b, nil
+}
+
+func (p *parser) unreadByte() error {
+	err := p.r.UnreadByte()
+	if err != nil {
+		return err
+	}
+
+	p.pos--
+
+	return nil
+}
+
+func (p *parser) parseStart() error {
+	b, err := p.readByte()
+	if err != nil {
+		return err
+	}
+
+	if b == tokenMaster {
+		p.start = StartingPointMaster
+		p.f = p.parseSeparator
+		return nil
+	}
+
+	if b == tokenDot {
+		b2, err := p.readByte()
+		if err != nil {
+			return err
+		}
+
+		if b2 == tokenDot {
+			p.f = p.parseSeparator
+			p.start = StartingPointParent
+			return nil
+		}
+
+		p.f = p.parseSeparator
+		p.start = StartingPointCurrent
+		return p.unreadByte()
+	}
+
+	p.f = p.parseSegment
+
+	return p.unreadByte()
+}
+
+func (p *parser) saveSegment() error {
+	if len(p.currentToken) > 0 {
+		i, err := strconv.ParseUint(p.currentToken, 10, 32)
+		if err != nil {
+			return err
+		}
+
+		if i >= hardenedStart {
+			p.pos -= len(p.currentToken) - 1
+			return fmt.Errorf("index must be lower than 2^31, got %d", i)
+		}
+
+		if p.currentTokenHardened {
+			i += hardenedStart
+		}
+
+		p.path = append(p.path, uint32(i))
+	}
+
+	p.f = p.parseSegment
+	p.resetCurrentToken()
+
+	return nil
+}
+
+func (p *parser) parseSeparator() error {
+	b, err := p.readByte()
+	if err != nil {
+		return err
+	}
+
+	if b == tokenSeparator {
+		return p.saveSegment()
+	}
+
+	return fmt.Errorf("expected %s, got %s", string(tokenSeparator), string(b))
+}
+
+func (p *parser) parseSegment() error {
+	b, err := p.readByte()
+	if err == io.EOF {
+		if len(p.currentToken) == 0 {
+			return fmt.Errorf("expected number, got EOF")
+		}
+
+		if newErr := p.saveSegment(); newErr != nil {
+			return newErr
+		}
+
+		return err
+	}
+
+	if err != nil {
+		return err
+	}
+
+	if len(p.currentToken) > 0 && b == tokenSeparator {
+		return p.saveSegment()
+	}
+
+	if len(p.currentToken) > 0 && b == tokenHardened {
+		p.currentTokenHardened = true
+		p.f = p.parseSeparator
+		return nil
+	}
+
+	if b < 0x30 || b > 0x39 {
+		return fmt.Errorf("expected number, got %s", string(b))
+	}
+
+	p.currentToken = fmt.Sprintf("%s%s", p.currentToken, string(b))
+
+	return nil
+}
+
+func Parse(str string) (StartingPoint, []uint32, error) {
+	p := newParser(str)
+	return p.parse()
+}

derivationpath/derivationpath_test.go

@@ -0,0 +1,86 @@
+package keycard
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParse(t *testing.T) {
+	scenarios := []struct {
+		path                  string
+		expectedPath          []uint32
+		expectedStartingPoint StartingPoint
+		err                   error
+	}{
+		{
+			path:                  "",
+			expectedPath:          []uint32{},
+			expectedStartingPoint: StartingPointCurrent,
+		},
+		{
+			path:                  "1",
+			expectedPath:          []uint32{1},
+			expectedStartingPoint: StartingPointCurrent,
+		},
+		{
+			path:                  "..",
+			expectedPath:          []uint32{},
+			expectedStartingPoint: StartingPointParent,
+		},
+		{
+			path:                  "m",
+			expectedPath:          []uint32{},
+			expectedStartingPoint: StartingPointMaster,
+		},
+		{
+			path:                  "m/1",
+			expectedPath:          []uint32{1},
+			expectedStartingPoint: StartingPointMaster,
+		},
+		{
+			path:                  "m/1/2",
+			expectedPath:          []uint32{1, 2},
+			expectedStartingPoint: StartingPointMaster,
+		},
+		{
+			path:                  "m/1/2'/3",
+			expectedPath:          []uint32{1, 2147483650, 3},
+			expectedStartingPoint: StartingPointMaster,
+		},
+		{
+			path: "m/",
+			err:  fmt.Errorf("at position 2, expected number, got EOF"),
+		},
+		{
+			path: "m/1//2",
+			err:  fmt.Errorf("at position 5, expected number, got /"),
+		},
+		{
+			path: "m/1'2",
+			err:  fmt.Errorf("at position 5, expected /, got 2"),
+		},
+		{
+			path: "m/'/2",
+			err:  fmt.Errorf("at position 3, expected number, got '"),
+		},
+		{
+			path: "m/2147483648",
+			err:  fmt.Errorf("at position 3, index must be lower than 2^31, got 2147483648"),
+		},
+	}
+
+	for i, s := range scenarios {
+		t.Run(fmt.Sprintf("scenario %d", i), func(t *testing.T) {
+			startingPoint, path, err := Parse(s.path)
+			if s.err == nil {
+				assert.NoError(t, err)
+				assert.Equal(t, s.expectedStartingPoint, startingPoint)
+				assert.Equal(t, s.expectedPath, path)
+			} else {
+				assert.Equal(t, s.err, err)
+			}
+		})
+	}
+}