initial

binary.go

@@ -0,0 +1,26 @@
+package dnsmsg
+
+//TODO: use binary.BigEndian in entire package (because of lower cost (golang/go#42958)) (but probably after golang/go#54097 gets fixed)
+
+func unpackUint16(b []byte) uint16 {
+	_ = b[1]
+	return uint16(b[0])<<8 | uint16(b[1])
+}
+
+func unpackUint32(b []byte) uint32 {
+	_ = b[3]
+	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
+}
+
+func appendUint16(b []byte, v uint16) []byte {
+	return append(b, byte(v>>8), byte(v))
+}
+
+func appendUint32(b []byte, v uint32) []byte {
+	return append(b,
+		byte(v>>24),
+		byte(v>>16),
+		byte(v>>8),
+		byte(v),
+	)
+}

builder.go

@@ -0,0 +1,192 @@
+package dnsmsg
+
+import (
+	"errors"
+)
+
+func MakeQuery[T name](msg []byte, id uint16, flags Flags, q Question[T]) []byte {
+	// Header
+	msg = appendUint16(msg, id)
+	msg = appendUint16(msg, uint16(flags))
+	msg = appendUint16(msg, 1)
+	msg = appendUint16(msg, 0)
+	msg = appendUint16(msg, 0)
+	msg = appendUint16(msg, 0)
+
+	// Question
+	appendName(msg, q.Name)
+
+	msg = appendUint16(msg, uint16(q.Type))
+	msg = appendUint16(msg, uint16(q.Class))
+	return msg
+}
+
+func MakeQueryWithEDNS0[T name](msg []byte, id uint16, flags Flags, q Question[T], ends0 EDNS0) []byte {
+	// Header
+	msg = appendUint16(msg, id)
+	msg = appendUint16(msg, uint16(flags))
+	msg = appendUint16(msg, 1)
+	msg = appendUint16(msg, 0)
+	msg = appendUint16(msg, 0)
+	msg = appendUint16(msg, 1)
+
+	// Question
+	appendName(msg, q.Name)
+	msg = appendUint16(msg, uint16(q.Type))
+	msg = appendUint16(msg, uint16(q.Class))
+
+	// EDNS0
+	msg = append(msg, 0) // root name
+	msg = appendUint16(msg, uint16(TypeOPT))
+	msg = appendUint16(msg, ends0.Payload)
+
+	// TODO: support rest of EDNS0 stuff.
+	msg = appendUint32(msg, 0)
+	msg = appendUint16(msg, 0)
+	return msg
+}
+
+func appendName[T name](buf []byte, n T) []byte {
+	switch n := any(n).(type) {
+	case Name:
+		return appendEscapedName(buf, n.name)
+	case ParserName:
+		return n.appendRawName(buf)
+	default:
+		panic("appendName: unsupported name type")
+	}
+}
+
+var errInvalidName = errors.New("invalid name")
+
+type Name struct {
+	name string
+}
+
+func NewName(name string) (Name, error) {
+	if !isValidEscapedName(name) {
+		return Name{}, errInvalidName
+	}
+	return Name{name: name}, nil
+}
+
+func isValidEscapedName(m string) bool {
+	if m == "" {
+		return false
+	}
+
+	if m == "." {
+		return true
+	}
+
+	labelLength := 0
+	nameLength := 0
+	inEscape := false
+	rooted := false
+
+	for i := 0; i < len(m); i++ {
+		char := m[i]
+		rooted = false
+
+		switch char {
+		case '.':
+			if inEscape {
+				labelLength++
+				inEscape = false
+				continue
+			}
+			if labelLength == 0 || labelLength > maxLabelLength {
+				return false
+			}
+			rooted = true
+			nameLength += labelLength + 1
+			labelLength = 0
+		case '\\':
+			inEscape = !inEscape
+			if !inEscape {
+				labelLength++
+			}
+		default:
+			if inEscape && isDigit(char) {
+				if len(m[i:]) < 3 || !isDigit(m[i+1]) || !isDigit(m[i+2]) {
+					return false
+				}
+				if _, ok := decodeDDD([3]byte{char, m[i+1], m[i+2]}); !ok {
+					return false
+				}
+				i += 2
+			}
+			inEscape = false
+			labelLength++
+		}
+	}
+
+	nameLength += labelLength
+
+	if inEscape {
+		return false
+	}
+
+	if nameLength > 254 || nameLength == 254 && !rooted {
+		return false
+	}
+
+	return true
+}
+
+func appendEscapedName(buf []byte, m string) []byte {
+	labelLength := byte(0)
+
+	labelIndex := len(buf)
+	buf = append(buf, 0)
+
+	for i := 0; i < len(m); i++ {
+		char := m[i]
+		switch char {
+		case '.':
+			buf[labelIndex] = labelLength
+			labelLength = 0
+			labelIndex = len(buf)
+			buf = append(buf, 0)
+		case '\\':
+			if isDigit(m[i+1]) {
+				labelLength++
+				ddd, _ := decodeDDD([3]byte{m[i+1], m[i+2], m[i+3]})
+				buf = append(buf, ddd)
+				i += 3
+				continue
+			}
+			buf = append(buf, m[i+1])
+			i += 1
+			labelLength++
+		default:
+			labelLength++
+			buf = append(buf, char)
+		}
+	}
+
+	if labelLength != 0 {
+		buf[labelIndex] = labelLength
+	}
+
+	if buf[len(buf)-1] != 0 {
+		buf = append(buf, 0)
+	}
+
+	return buf
+}
+
+func isDigit(char byte) bool {
+	return char >= '0' && char <= '9'
+}
+
+func decodeDDD(ddd [3]byte) (uint8, bool) {
+	ddd[0] -= '0'
+	ddd[1] -= '0'
+	ddd[2] -= '0'
+	num := uint16(ddd[0])*100 + uint16(ddd[1])*10 + uint16(ddd[2])
+	if num > 255 {
+		return 0, false
+	}
+	return uint8(num), true
+}

builder_test.go

@@ -0,0 +1,145 @@
+package dnsmsg
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+var (
+	escapes          = "\\.\\223\\.\\\\"
+	escapesCharCount = 4
+	label54          = escapes + strings.Repeat("a", 54-2*escapesCharCount) + escapes
+	label63          = escapes + strings.Repeat("a", 63-2*escapesCharCount) + escapes
+	label64          = escapes + strings.Repeat("a", 64-2*escapesCharCount) + escapes
+)
+
+var newNameTests = []struct {
+	name             string
+	ok               bool
+	diferentAsString bool
+}{
+	{name: "", ok: false},
+	{name: ".", ok: true},
+	{name: "com.", ok: true},
+	{name: "com", ok: true},
+
+	{name: "go.dev", ok: true},
+	{name: "go.dev.", ok: true},
+	{name: "www.go.dev", ok: true},
+	{name: "www.go.dev.", ok: true},
+
+	{name: "www..go.dev", ok: false},
+	{name: ".www.go.dev", ok: false},
+	{name: "..www.go.dev", ok: false},
+	{name: "www.go.dev..", ok: false},
+
+	{name: "www.go.dev\\.", ok: true},
+	{name: "www.go.dev\\..", ok: true},
+	{name: "www.go.dev\\...", ok: false},
+	{name: "www\\..go.dev", ok: true},
+	{name: "www\\...go.dev", ok: false},
+
+	{name: "\\\\www.go.dev.", ok: true},
+	{name: "\\\\www.go.dev.", ok: true},
+	{name: "www.go.dev\\\\\\.", ok: true},
+	{name: "www.go.dev\\\\\\.", ok: true},
+	{name: "\\ww\\ w.go.dev", ok: true, diferentAsString: true},
+	{name: "ww\\w.go.dev", ok: true, diferentAsString: true},
+	{name: "www.go.dev\\\\", ok: true},
+
+	{name: "\\223www.go.dev", ok: true},
+	{name: "\\000www.go.dev", ok: true},
+	{name: "\\255www.go.dev", ok: true},
+
+	{name: "\\256www.go.dev", ok: false},
+	{name: "\\999www.go.dev", ok: false},
+	{name: "\\12www.go.dev", ok: false},
+	{name: "\\1www.go.dev", ok: false},
+	{name: "www.go.dev\\223", ok: true},
+	{name: "www.go.dev\\12", ok: false},
+	{name: "www.go.dev\\1", ok: false},
+	{name: "www.go.dev\\", ok: false},
+
+	{name: label63 + ".go.dev", ok: true},
+	{name: label64 + ".go.dev", ok: false},
+
+	// 253B non-rooted name.
+	{
+		name: fmt.Sprintf("%[1]v.%[1]v.%[1]v.%v.go.dev", label63, label54),
+		ok:   true,
+	},
+
+	// 254B rooted name.
+	{
+		name: fmt.Sprintf("%[1]v.%[1]v.%[1]v.%v.go.dev.", label63, label54),
+		ok:   true,
+	},
+
+	// 254B non-rooted name.
+	{
+		name: fmt.Sprintf("%[1]v.%[1]v.%[1]v.%va.go.dev", label63, label54),
+		ok:   false,
+	},
+
+	// 255B rooted name.
+	{
+		name: fmt.Sprintf("%[1]v.%[1]v.%[1]v.%va.go.dev.", label63, label54),
+		ok:   false,
+	},
+}
+
+func TestNewName(t *testing.T) {
+	for _, v := range newNameTests {
+		_, err := NewName(v.name)
+		expectErr := errInvalidName
+		if v.ok {
+			expectErr = nil
+		}
+		if expectErr != err {
+			t.Errorf("'%v' got error: %v, expected: %v", v.name, err, expectErr)
+		}
+	}
+}
+
+func TestAppendEscapedName(t *testing.T) {
+	for _, v := range newNameTests {
+		n, err := NewName(v.name)
+		if err != nil {
+			continue
+		}
+
+		packedName := appendEscapedName(nil, v.name)
+
+		p, err := NewParser(packedName)
+		if err != nil {
+			continue
+		}
+
+		name := ParserName{m: &p, nameStart: 0}
+		_, err = name.unpack()
+		if err != nil {
+			t.Errorf("'%v' failed while unpacking packed name: %v\n\traw: %v", v.name, err, packedName)
+			continue
+		}
+
+		if !name.EqualName(n) {
+			t.Errorf("'%v' ParserName is not equal to name\n\traw: %v", v.name, packedName)
+			continue
+		}
+
+		if v.diferentAsString {
+			continue
+		}
+
+		expectName := v.name
+		dotAtEnd := expectName[len(expectName)-1] == '.'
+		if !dotAtEnd || (len(expectName) > 2 && dotAtEnd && expectName[len(expectName)-2] == '\\') {
+			expectName += "."
+		}
+
+		if name := name.String(); name != expectName {
+			t.Errorf("'%v' got name: %v, expected: %v\n\traw: %v", v.name, name, expectName, packedName)
+		}
+	}
+}

go.mod

@@ -0,0 +1,3 @@
+module github.com/mateusz834/dnsmsg
+
+go 1.20