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tlsfrag.go
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tlsfrag.go
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package chained
import (
"encoding/hex"
"math/rand"
"net"
"regexp"
"strconv"
"strings"
"github.com/Jigsaw-Code/outline-sdk/transport"
"github.com/Jigsaw-Code/outline-sdk/transport/tlsfrag"
"github.com/getlantern/common/config"
"github.com/getlantern/errors"
)
func wrapTLSFrag(conn net.Conn, pc *config.ProxyConfig) net.Conn {
fragFunc, ok := makeFragFunc(pc)
if ok {
tlsFragConn, err := tlsfrag.WrapConnFunc(&streamConn{conn}, fragFunc)
if err != nil {
log.Errorf("tlsfrag: wrapping error: %w", err)
return conn
}
return tlsFragConn
}
return conn
}
func makeFragFunc(pc *config.ProxyConfig) (tlsfrag.FragFunc, bool) {
fragStr, ok := pc.PluggableTransportSettings["tlsfrag"]
if !ok {
return nil, false
}
// fragStr should be of the form <frag func> or <frag func>:<func config>.
// Example: "index:3" or "regex:foo.*" or "regex:test" or "rand:10,80"
funcType, cfg, hasCfg := strings.Cut(fragStr, ":")
if !hasCfg {
log.Error("tlsfrag: missing config specifier")
return nil, false
}
if cfg == "" {
log.Error("tlsfrag: empty config specifier")
return nil, false
}
switch funcType {
case "index":
index, err := strconv.Atoi(cfg)
if err != nil {
log.Errorf("tlsfrag: bad index specifier: %v", err)
return nil, false
}
return func(_ []byte) int { return index }, true
case "regex":
regex, err := regexp.Compile(hex.EncodeToString([]byte(cfg)))
if err != nil {
log.Errorf("tlsfrag: bad regex specifier: %v", err)
return nil, false
}
return func(b []byte) int {
loc := regex.FindIndex([]byte(hex.EncodeToString(b)))
if loc == nil {
return 0
}
log.Debugf("tlsfrag: regex match at index: %v", loc[0]/2)
return loc[0] / 2
}, true
case "rand":
min, max, err := parseRange(cfg)
if err != nil {
log.Errorf("tlsfrag: bad rand specifier: %v", err)
return nil, false
}
return func(_ []byte) int {
randIndex := min + rand.Intn(max-min)
log.Debugf("tlsfrag: rand index: %v", randIndex)
return randIndex
}, true
default:
log.Errorf("tlsfrag: unrecognized func type '%s'", funcType)
return nil, false
}
}
func parseRange(cfg string) (int, int, error) {
parts := strings.Split(cfg, ",")
if len(parts) != 2 {
return 0, 0, errors.New("expected two parts")
}
min, err := strconv.Atoi(parts[0])
if err != nil {
return 0, 0, errors.New("bad min: %v", err)
}
max, err := strconv.Atoi(parts[1])
if err != nil {
return 0, 0, errors.New("bad max: %v", err)
}
if min > max {
return 0, 0, errors.New("min > max")
}
return min, max, nil
}
type streamConn struct {
net.Conn
}
func (sc *streamConn) CloseRead() error {
return sc.Close()
}
func (sc *streamConn) CloseWrite() error {
return sc.Close()
}
var _ transport.StreamConn = (*streamConn)(nil)