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https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-14 05:11:19 -04:00
Add packet padding container for packet length shaping
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parent
c1ac2aa577
commit
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3 changed files with 194 additions and 0 deletions
47
common/packetPaddingContainer/container.go
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47
common/packetPaddingContainer/container.go
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package packetPaddingContainer
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import "encoding/binary"
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func New() PacketPaddingContainer {
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return packetPaddingContainer{}
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}
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type packetPaddingContainer struct {
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}
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func (c packetPaddingContainer) Pack(data_OWNERSHIP_RELINQUISHED []byte, padding int) []byte {
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data := append(data_OWNERSHIP_RELINQUISHED, make([]byte, padding)...)
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data_length := len(data_OWNERSHIP_RELINQUISHED)
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data = append(data, byte(data_length>>8), byte(data_length))
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return data
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}
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func (c packetPaddingContainer) Pad(padding int) []byte {
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if assertPaddingLengthIsNotNegative := padding < 0; assertPaddingLengthIsNotNegative {
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return nil
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}
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switch padding {
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case 0:
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return []byte{}
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case 1:
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return []byte{0}
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case 2:
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return []byte{0, 0}
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default:
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return append(make([]byte, padding-2), byte(padding>>8), byte(padding))
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}
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}
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func (c packetPaddingContainer) Unpack(wrappedData_OWNERSHIP_RELINQUISHED []byte) ([]byte, int) {
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if len(wrappedData_OWNERSHIP_RELINQUISHED) < 2 {
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return nil, len(wrappedData_OWNERSHIP_RELINQUISHED)
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}
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wrappedData_tail := wrappedData_OWNERSHIP_RELINQUISHED[len(wrappedData_OWNERSHIP_RELINQUISHED)-2:]
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dataLength := int(binary.BigEndian.Uint16(wrappedData_tail))
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paddingLength := len(wrappedData_OWNERSHIP_RELINQUISHED) - dataLength - 2
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if paddingLength < 0 {
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return nil, paddingLength
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}
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return wrappedData_OWNERSHIP_RELINQUISHED[:dataLength], paddingLength
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}
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34
common/packetPaddingContainer/containerIfce.go
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34
common/packetPaddingContainer/containerIfce.go
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package packetPaddingContainer
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// PacketPaddingContainer is an interface that defines methods to pad packets
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// with a given number of bytes, and to unpack the padding from a padded packet.
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// The packet format is as follows if the desired output length is greater than
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// 2 bytes:
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// | data | padding | data length |
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// The data length is a 16-bit big-endian integer that represents the length of
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// the data in bytes.
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// If the desired output length is 2 bytes or less, the packet format is as
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// follows:
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// | padding |
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// No payload will be included in the packet.
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type PacketPaddingContainer interface {
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// Pack pads the given data with the given number of bytes, and appends the
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// length of the data to the end of the data. The returned byte slice
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// contains the padded data.
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// This generates a packet with a length of
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// len(data_OWNERSHIP_RELINQUISHED) + padding + 2
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// @param data_OWNERSHIP_RELINQUISHED - The payload, this reference is consumed and should not be used after this call.
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// @param padding - The number of padding bytes to add to the data.
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Pack(data_OWNERSHIP_RELINQUISHED []byte, padding int) []byte
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// Unpack extracts the data and padding from the given padded data. It
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// returns the data and the number of padding bytes.
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// the data may be nil.
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// @param wrappedData_OWNERSHIP_RELINQUISHED - The packet, this reference is consumed and should not be used after this call.
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Unpack(wrappedData_OWNERSHIP_RELINQUISHED []byte) ([]byte, int)
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// Pad returns a padding packet of padding length.
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// If the padding length is less than 0, nil is returned.
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// @param padding - The number of padding bytes to add to the data.
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Pad(padding int) []byte
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}
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113
common/packetPaddingContainer/container_test.go
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113
common/packetPaddingContainer/container_test.go
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package packetPaddingContainer_test
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import (
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"testing"
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. "github.com/smartystreets/goconvey/convey"
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"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/packetPaddingContainer"
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)
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func TestPacketPaddingContainer(t *testing.T) {
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Convey("Given a PacketPaddingContainer", t, func() {
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container := packetPaddingContainer.New()
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Convey("When packing data with padding", func() {
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data := []byte("testdata")
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padding := 4
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packedData := container.Pack(data, padding)
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Convey("The packed data should have the correct length", func() {
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expectedLength := len(data) + padding + 2
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So(len(packedData), ShouldEqual, expectedLength)
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})
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Convey("When unpacking the packed data", func() {
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unpackedData, unpackedPadding := container.Unpack(packedData)
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Convey("The unpacked data should match the original data", func() {
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So(string(unpackedData), ShouldEqual, string(data))
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})
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Convey("The unpacked padding should match the original padding", func() {
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So(unpackedPadding, ShouldEqual, padding)
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})
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})
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})
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Convey("When packing empty data with padding", func() {
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data := []byte("")
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padding := 4
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packedData := container.Pack(data, padding)
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Convey("The packed data should have the correct length", func() {
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expectedLength := len(data) + padding + 2
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So(len(packedData), ShouldEqual, expectedLength)
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})
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Convey("When unpacking the packed data", func() {
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unpackedData, unpackedPadding := container.Unpack(packedData)
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Convey("The unpacked data should match the original data", func() {
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So(string(unpackedData), ShouldEqual, string(data))
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})
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Convey("The unpacked padding should match the original padding", func() {
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So(unpackedPadding, ShouldEqual, padding)
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})
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})
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})
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Convey("When packing data with zero padding", func() {
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data := []byte("testdata")
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padding := 0
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packedData := container.Pack(data, padding)
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Convey("The packed data should have the correct length", func() {
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expectedLength := len(data) + padding + 2
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So(len(packedData), ShouldEqual, expectedLength)
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})
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Convey("When unpacking the packed data", func() {
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unpackedData, unpackedPadding := container.Unpack(packedData)
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Convey("The unpacked data should match the original data", func() {
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So(string(unpackedData), ShouldEqual, string(data))
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})
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Convey("The unpacked padding should match the original padding", func() {
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So(unpackedPadding, ShouldEqual, padding)
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})
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})
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})
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Convey("When padding data", func() {
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Convey("With a positive padding length", func() {
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padLength := 3
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padData := container.Pad(padLength)
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Convey("The padded data should have the correct length", func() {
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So(len(padData), ShouldEqual, padLength)
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})
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})
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Convey("With a zero padding length", func() {
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padLength := 0
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padData := container.Pad(padLength)
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Convey("The padded data should be empty", func() {
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So(len(padData), ShouldEqual, 0)
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})
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})
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Convey("With a negative padding length", func() {
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padLength := -1
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padData := container.Pad(padLength)
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Convey("The padded data should be nil", func() {
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So(padData, ShouldBeNil)
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})
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})
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})
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})
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}
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