From 306385f9c23d93e0058a810c586ee9c59968fdeb Mon Sep 17 00:00:00 2001
From: Qian Wang <cbeuw.andy@gmail.com>
Date: Sat, 24 Nov 2018 01:24:47 +0000
Subject: [PATCH] Uncomment header obfuscation

---
 internal/multiplex/switchboard.go | 11 +++++++++++
 internal/util/obfs.go             | 26 +++++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/internal/multiplex/switchboard.go b/internal/multiplex/switchboard.go
index d0e46aa..69736a8 100644
--- a/internal/multiplex/switchboard.go
+++ b/internal/multiplex/switchboard.go
@@ -154,6 +154,17 @@ func (sb *switchboard) deplex(ce *connEnclave) {
 		}
 		frame := sb.session.deobfs(buf[:n])
 
+		// FIXME: there has been a bug in which a packet has
+		// a seemingly corrupted StreamID (e.g. when the largest streamID is something like 3000
+		// and suddently a streamID of 3358661675 is added.
+		// It happens once ~6 hours and the occourance is realy unstable
+		// I couldn't find a way to reproduce it. But I do have some clue.
+		// I commented out the util.genXorKeys function so that the stream headers are being
+		// sent in plaintext, and this bug didn't happen again. So I suspect it has to do
+		// with xxHash. Either it's to do with my usage of the libary or the implementation
+		// of the library. Maybe there's a race somewhere? I may eventually use another
+		// method to encrypt the headers. xxHash isn't cryptographic afterall.
+
 		stream := sb.session.getOrAddStream(frame.StreamID, frame.Closing == 1)
 		// if the frame is telling us to close a closed stream
 		// (this happens when ss-server and ss-local closes the stream
diff --git a/internal/util/obfs.go b/internal/util/obfs.go
index 6fc9f0c..7c9b70d 100644
--- a/internal/util/obfs.go
+++ b/internal/util/obfs.go
@@ -3,7 +3,7 @@ package util
 import (
 	"encoding/binary"
 
-	//xxhash "github.com/OneOfOne/xxhash"
+	xxhash "github.com/OneOfOne/xxhash"
 	mux "github.com/cbeuw/Cloak/internal/multiplex"
 )
 
@@ -11,18 +11,18 @@ import (
 // The keys are generated from the SID and the payload of the frame.
 // FIXME: this code will panic if len(data)<18.
 func genXorKeys(secret []byte, data []byte) (i uint32, ii uint32, iii uint32) {
-	/*
-		h := xxhash.New32()
-		ret := make([]uint32, 3)
-		preHash := make([]byte, 16)
-		for j := 0; j < 3; j++ {
-			copy(preHash[0:10], secret[j*10:j*10+10])
-			copy(preHash[10:16], data[j*6:j*6+6])
-			h.Write(preHash)
-			ret[j] = h.Sum32()
-		}
-		return ret[0], ret[1], ret[2]
-	*/
+
+	h := xxhash.New32()
+	ret := make([]uint32, 3)
+	preHash := make([]byte, 16)
+	for j := 0; j < 3; j++ {
+		copy(preHash[0:10], secret[j*10:j*10+10])
+		copy(preHash[10:16], data[j*6:j*6+6])
+		h.Write(preHash)
+		ret[j] = h.Sum32()
+	}
+	return ret[0], ret[1], ret[2]
+
 	return 0, 0, 0
 }