commit 4ae7ae24a5c980d334d18a880d00d27ad1bd2a97 · seiso.moe/magna

+79 -37

domain_name.go

···

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       // decode_domain decodes a domain name from a buffer starting at offset.

     

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       // It returns the domain name along with the offset and error.

     

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       func decode_domain(buf []byte, offset int) (string, int, error) {

     

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       -
       	labels := make([]string, 0)

     

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       	var builder strings.Builder

     

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       	firstLabel := true

     

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       +
       

     

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       	seen_offsets := make(map[int]struct{})

     

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       	has_jumped := false

     

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       	prev_offset := 0

     

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       	finalOffsetAfterJump := -1

     

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       +
       

     

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       	currentOffset := offset

     

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       	var length uint8

     

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       	var label []byte

     

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       	var sec byte

     

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       	var err error

     

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       	for {

     

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       		length, offset, err = getU8(buf, offset)

     

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       		if _, found := seen_offsets[currentOffset]; found {

     

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       			return "", len(buf), &DomainCompressionError{}

     

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       		}

     

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       		seen_offsets[currentOffset] = struct{}{}

     

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       		length, nextOffsetAfterLen, err := getU8(buf, currentOffset)

     

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       		if err != nil {

     

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       			return "", len(buf), err

     

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       		}

     

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       		if length == 0 {

     

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       			currentOffset = nextOffsetAfterLen

     

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       			break

     

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       		}

     

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       -
       		if length&0xC0 == 0xC0 {

     

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       			sec, offset, err = getU8(buf, offset)

     

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       		if (length & 0xC0) == 0xC0 {

     

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       			sec, nextOffsetAfterPtr, err := getU8(buf, nextOffsetAfterLen)

     

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       			if err != nil {

     

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       				return "", len(buf), err

     

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       			}

     

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       			if !has_jumped {

     

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       				prev_offset = offset

     

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       				has_jumped = true

     

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       			}

     

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       			jumpTargetOffset := int(length&0x3F)<<8 | int(sec)

     

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       			if _, found := seen_offsets[offset]; found {

     

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       			if jumpTargetOffset >= len(buf) {

     

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       				return "", len(buf), &BufferOverflowError{Length: len(buf), Offset: jumpTargetOffset}

     

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       			}

     

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       			if _, found := seen_offsets[jumpTargetOffset]; found {

     

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       				return "", len(buf), &DomainCompressionError{}

     

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       			}

     

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       			seen_offsets[offset] = struct{}{}

     

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       			offset = int(length&0x3F)<<8 | int(sec)

     

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       		} else {

     

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       			if length > 63 {

     

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       				return "", len(buf), &InvalidLabelError{Length: int(length)}

     

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       			if finalOffsetAfterJump == -1 {

     

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       				finalOffsetAfterJump = nextOffsetAfterPtr

     

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       			}

     

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       			label, offset, err = getSlice(buf, offset, int(length))

     

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       			if err != nil {

     

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       				return "", len(buf), err

     

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       			}

     

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       			currentOffset = jumpTargetOffset

     

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       			continue

     

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       		}

     

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       			labels = append(labels, string(label))

     

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       		if length > 63 {

     

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       			return "", len(buf), &InvalidLabelError{Length: int(length)}

     

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       		}

     

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       +
       

     

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       		labelBytes, nextOffsetAfterLabel, err := getSlice(buf, nextOffsetAfterLen, int(length))

     

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       		if err != nil {

     

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       			return "", len(buf), err

     

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       		}

     

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       +
       

     

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       		if !firstLabel {

     

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       			builder.WriteByte('.')

     

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       		}

     

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       		builder.Write(labelBytes)

     

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       		firstLabel = false

     

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       		currentOffset = nextOffsetAfterLabel

     

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       +
       

     

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       	}

     

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       	if has_jumped {

     

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       		offset = prev_offset

     

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       	finalReadOffset := currentOffset

     

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       	if finalOffsetAfterJump != -1 {

     

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       		finalReadOffset = finalOffsetAfterJump

     

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       	}

     

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       	return strings.Join(labels, "."), offset, nil

     

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       	return builder.String(), finalReadOffset, nil

     

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       }

     

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       // encode_domain returns the bytes of the input bytes appened with the encoded domain name.

     

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       func encode_domain(bytes []byte, domain_name string, offsets *map[string]uint16) []byte {

     

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       	pos := uint16(len(bytes))

     

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       	if domain_name == "." || domain_name == "" {

     

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       		return append(bytes, 0)

     

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       	}

     

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       	labels := strings.Split(domain_name, ".")

     

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       	for i, label := range labels {

     

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       		remaining_labels := strings.Join(labels[i:], ".")

     

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       	labelIndices := []int{0}

     

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       	for i, r := range domain_name {

     

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       		if r == '.' {

     

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       			labelIndices = append(labelIndices, i+1)

     

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       		}

     

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       	}

     

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       		if offset, found := (*offsets)[remaining_labels]; found {

     

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       	for i := 0; i < len(labelIndices); i++ {

     

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       		suffix := domain_name[labelIndices[i]:]

     

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       		if offset, found := (*offsets)[suffix]; found {

     

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       			pointer := 0xC000 | offset

     

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       			return binary.BigEndian.AppendUint16(bytes, pointer)

     

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       		}

     

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       		(*offsets)[remaining_labels] = pos

     

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       		bytes = append(bytes, uint8(len(label)))

     

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       		bytes = append(bytes, []byte(label)...)

     

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       		pos += 1 + uint16(len(label))

     

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       		currentPos := uint16(len(bytes))

     

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       		if currentPos <= 0x3FFF {

     

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       			(*offsets)[suffix] = currentPos

     

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       		}

     

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       		start := labelIndices[i]

     

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       		end := len(domain_name)

     

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       		if i+1 < len(labelIndices) {

     

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       			end = labelIndices[i+1] - 1

     

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       		}

     

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       		labelBytes := []byte(domain_name[start:end])

     

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       		if len(labelBytes) == 0 {

     

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       			continue

     

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       		}

     

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       		if len(labelBytes) > 63 {

     

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       			labelBytes = labelBytes[:63]

     

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       		}

     

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       		bytes = append(bytes, byte(len(labelBytes)))

     

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       		bytes = append(bytes, labelBytes...)

     

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       	}

     

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       	return append(bytes, 0)

+47

domain_test.go

···

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       	"github.com/stretchr/testify/assert"

     

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       )

     

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       func BenchmarkDecodeDomainSimple(b *testing.B) {

     

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       	input := []byte{3, 'w', 'w', 'w', 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0}

     

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       	for i := 0; i < b.N; i++ {

     

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       		_, _, _ = decode_domain(input, 0)

     

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       	}

     

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       }

     

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       func BenchmarkDecodeDomainCompressed(b *testing.B) {

     

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       	input := []byte{

     

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       		0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 0x03, 'c', 'o', 'm', 0x00,

     

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       		0x03, 'f', 'o', 'o', 0xc0, 0x00,

     

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       	}

     

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       	offset := 13

     

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       	b.ResetTimer()

     

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       	for i := 0; i < b.N; i++ {

     

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       		_, _, _ = decode_domain(input, offset)

     

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       	}

     

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       }

     

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       func BenchmarkEncodeDomainSimple(b *testing.B) {

     

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       	domain := "www.example.com"

     

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       	offsets := make(map[string]uint16)

     

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       	out := make([]byte, 0, 64)

     

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       	b.ResetTimer()

     

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       	for i := 0; i < b.N; i++ {

     

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       		_ = encode_domain(out[:0], domain, &offsets)

     

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       		for k := range offsets {

     

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       			delete(offsets, k)

     

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       		}

     

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       	}

     

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       }

     

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       func BenchmarkEncodeDomainWithCompression(b *testing.B) {

     

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       	domain1 := "www.example.com"

     

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       	domain2 := "mail.example.com"

     

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       	offsets := make(map[string]uint16)

     

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       	out := make([]byte, 0, 128)

     

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       	b.ResetTimer()

     

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       	for i := 0; i < b.N; i++ {

     

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       		tempOut := encode_domain(out[:0], domain1, &offsets)

     

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       		_ = encode_domain(tempOut, domain2, &offsets)

     

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       		for k := range offsets {

     

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       			delete(offsets, k)

     

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       		}

     

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       	}

     

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       }

     

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       func TestDecodeDomain(t *testing.T) {

     

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       	tests := []struct {

     

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       		name           string

+1 -1

header.go

···

       49
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       // Encode encodes the header packet to the byte representation.

     

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       func (h *Header) Encode() []byte {

     

       52
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       	var bytes []byte

     

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       	bytes := make([]byte, 0, 12)

     

       53
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       	bytes = binary.BigEndian.AppendUint16(bytes, h.ID)

     

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