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XHTTP transport: New options for bypassing CDN's detection (#5414)
Usage: https://github.com/XTLS/Xray-core/pull/5414#issuecomment-3770071786 Closes https://github.com/XTLS/Xray-core/issues/4346 --------- Co-authored-by: 风扇滑翔翼 <Fangliding.fshxy@outlook.com>
This commit is contained in:
Dmitrii Makhno
@@ -0,0 +1,307 @@
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package splithttp
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import (
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"crypto/rand"
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"math"
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"net/http"
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"net/url"
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"strings"
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"golang.org/x/net/http2/hpack"
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)
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type PaddingMethod string
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const (
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PaddingMethodRepeatX PaddingMethod = "repeat-x"
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PaddingMethodTokenish PaddingMethod = "tokenish"
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)
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const charsetBase62 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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// Huffman encoding gives ~20% size reduction for base62 sequences
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const avgHuffmanBytesPerCharBase62 = 0.8
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const validationTolerance = 2
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type XPaddingPlacement struct {
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Placement string
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Key string
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Header string
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RawURL string
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}
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type XPaddingConfig struct {
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Length int
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Placement XPaddingPlacement
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Method PaddingMethod
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}
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func randStringFromCharset(n int, charset string) (string, bool) {
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if n <= 0 || len(charset) == 0 {
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return "", false
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}
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m := len(charset)
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limit := byte(256 - (256 % m))
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result := make([]byte, n)
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i := 0
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buf := make([]byte, 256)
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for i < n {
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if _, err := rand.Read(buf); err != nil {
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return "", false
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}
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for _, rb := range buf {
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if rb >= limit {
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continue
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}
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result[i] = charset[int(rb)%m]
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i++
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if i == n {
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break
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}
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}
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}
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return string(result), true
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}
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func absInt(x int) int {
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if x < 0 {
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return -x
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}
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return x
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}
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func GenerateTokenishPaddingBase62(targetHuffmanBytes int) string {
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n := int(math.Ceil(float64(targetHuffmanBytes) / avgHuffmanBytesPerCharBase62))
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if n < 1 {
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n = 1
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}
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randBase62Str, ok := randStringFromCharset(n, charsetBase62)
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if !ok {
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return ""
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}
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const maxIter = 150
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adjustChar := byte('X')
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// Adjust until close enough
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for iter := 0; iter < maxIter; iter++ {
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currentLength := int(hpack.HuffmanEncodeLength(randBase62Str))
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diff := currentLength - targetHuffmanBytes
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if absInt(diff) <= validationTolerance {
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return randBase62Str
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}
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if diff < 0 {
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// Too small -> append padding char(s)
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randBase62Str += string(adjustChar)
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// Avoid a long run of identical chars
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if adjustChar == 'X' {
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adjustChar = 'Z'
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} else {
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adjustChar = 'X'
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}
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} else {
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// Too big -> remove from the end
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if len(randBase62Str) <= 1 {
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return randBase62Str
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}
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randBase62Str = randBase62Str[:len(randBase62Str)-1]
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}
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}
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return randBase62Str
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}
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func GeneratePadding(method PaddingMethod, length int) string {
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if length <= 0 {
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return ""
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}
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// https://www.rfc-editor.org/rfc/rfc7541.html#appendix-B
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// h2's HPACK Header Compression feature employs a huffman encoding using a static table.
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// 'X' and 'Z' are assigned an 8 bit code, so HPACK compression won't change actual padding length on the wire.
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// https://www.rfc-editor.org/rfc/rfc9204.html#section-4.1.2-2
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// h3's similar QPACK feature uses the same huffman table.
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switch method {
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case PaddingMethodRepeatX:
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return strings.Repeat("X", length)
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case PaddingMethodTokenish:
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paddingValue := GenerateTokenishPaddingBase62(length)
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if paddingValue == "" {
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return strings.Repeat("X", length)
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}
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return paddingValue
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default:
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return strings.Repeat("X", length)
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}
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}
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func ApplyPaddingToCookie(req *http.Request, name, value string) {
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if req == nil || name == "" || value == "" {
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return
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}
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req.AddCookie(&http.Cookie{
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Name: name,
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Value: value,
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Path: "/",
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})
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}
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func ApplyPaddingToQuery(u *url.URL, key, value string) {
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if u == nil || key == "" || value == "" {
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return
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}
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q := u.Query()
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q.Set(key, value)
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u.RawQuery = q.Encode()
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}
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func (c *Config) GetNormalizedXPaddingBytes() RangeConfig {
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if c.XPaddingBytes == nil || c.XPaddingBytes.To == 0 {
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return RangeConfig{
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From: 100,
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To: 1000,
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}
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}
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return *c.XPaddingBytes
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}
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func (c *Config) ApplyXPaddingToHeader(h http.Header, config XPaddingConfig) {
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if h == nil {
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return
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}
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paddingValue := GeneratePadding(config.Method, config.Length)
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switch p := config.Placement; p.Placement {
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case PlacementHeader:
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h.Set(p.Header, paddingValue)
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case PlacementQueryInHeader:
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u, err := url.Parse(p.RawURL)
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if err != nil || u == nil {
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return
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}
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u.RawQuery = p.Key + "=" + paddingValue
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h.Set(p.Header, u.String())
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}
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}
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func (c *Config) ApplyXPaddingToRequest(req *http.Request, config XPaddingConfig) {
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if req == nil {
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return
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}
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if req.Header == nil {
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req.Header = make(http.Header)
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}
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placement := config.Placement.Placement
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if placement == PlacementHeader || placement == PlacementQueryInHeader {
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c.ApplyXPaddingToHeader(req.Header, config)
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return
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}
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paddingValue := GeneratePadding(config.Method, config.Length)
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switch placement {
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case PlacementCookie:
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ApplyPaddingToCookie(req, config.Placement.Key, paddingValue)
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case PlacementQuery:
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ApplyPaddingToQuery(req.URL, config.Placement.Key, paddingValue)
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}
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}
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func (c *Config) ExtractXPaddingFromRequest(req *http.Request, obfsMode bool) (string, string) {
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if req == nil {
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return "", ""
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}
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if !obfsMode {
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referrer := req.Header.Get("Referer")
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if referrer != "" {
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if referrerURL, err := url.Parse(referrer); err == nil {
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paddingValue := referrerURL.Query().Get("x_padding")
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paddingPlacement := PlacementQueryInHeader + "=Referer, key=x_padding"
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return paddingValue, paddingPlacement
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}
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} else {
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paddingValue := req.URL.Query().Get("x_padding")
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return paddingValue, PlacementQuery + ", key=x_padding"
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}
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}
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key := c.XPaddingKey
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header := c.XPaddingHeader
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if cookie, err := req.Cookie(key); err == nil {
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if cookie != nil && cookie.Value != "" {
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paddingValue := cookie.Value
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paddingPlacement := PlacementCookie + ", key=" + key
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return paddingValue, paddingPlacement
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}
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}
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headerValue := req.Header.Get(header)
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if headerValue != "" {
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if c.XPaddingPlacement == PlacementHeader {
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paddingPlacement := PlacementHeader + "=" + header
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return headerValue, paddingPlacement
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}
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if parsedURL, err := url.Parse(headerValue); err == nil {
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paddingPlacement := PlacementQueryInHeader + "=" + header + ", key=" + key
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return parsedURL.Query().Get(key), paddingPlacement
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}
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}
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queryValue := req.URL.Query().Get(key)
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if queryValue != "" {
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paddingPlacement := PlacementQuery + ", key=" + key
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return queryValue, paddingPlacement
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}
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return "", ""
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}
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func (c *Config) IsPaddingValid(paddingValue string, from, to int32, method PaddingMethod) bool {
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if paddingValue == "" {
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return false
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}
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if to <= 0 {
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r := c.GetNormalizedXPaddingBytes()
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from, to = r.From, r.To
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}
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switch method {
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case PaddingMethodRepeatX:
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n := int32(len(paddingValue))
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return n >= from && n <= to
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case PaddingMethodTokenish:
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const tolerance = int32(validationTolerance)
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n := int32(hpack.HuffmanEncodeLength(paddingValue))
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f := from - tolerance
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t := to + tolerance
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if f < 0 {
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f = 0
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}
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return n >= f && n <= t
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default:
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n := int32(len(paddingValue))
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return n >= from && n <= to
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}
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}
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