Commit 01ac0373 authored by David Fifield's avatar David Fifield
Browse files

Add random padding to the first client→server volley. 

This is an experimental workaround for possible TLS-in-DTLS
fingerprinting and throttling in China.

https://github.com/net4people/bbs/issues/255
parent 8e5ea826

client/lib/snowflake.go

+8 −5
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ The Dial function connects to a Snowflake server: 
package snowflake_client



import (

	"bytes"

	"context"

	"errors"

	"log"
@@ -35,6 +36,7 @@ import ( 
	"strings"

	"time"



	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/encapsulation"

	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/event"

	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"

	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/turbotunnel"
@@ -317,13 +319,14 @@ func newSession(snowflakes SnowflakeCollector) (net.PacketConn, *smux.Session, e 
			return nil, errors.New("handler: Received invalid Snowflake")

		}

		log.Println("---- Handler: snowflake assigned ----")

		buf := bytes.NewBuffer(nil)

		// Send the magic Turbo Tunnel token.

		_, err := conn.Write(turbotunnel.Token[:])

		if err != nil {

			return nil, err

		}

		buf.Write(turbotunnel.Token[:])

		// Send ClientID prefix.

		_, err = conn.Write(clientID[:])

		buf.Write(clientID[:])

		// Send some amount of padding.

		encapsulation.WritePadding(buf, int(2000.0 + rand.NormFloat64() * 100.0))

		_, err := conn.Write(buf.Bytes())

		if err != nil {

			return nil, err

		}