Add preliminary support for packet length obfuscation.

The same algorithm as ScrambleSuit is used, except:
 * SipHash-2-4 in OFB mode is used to create the distribution.
 * The system CSPRNG is used when sampling the distribution.

This fixes most of #3, all that remains is generating and sending a
persistent distribution on the server side to the client.

1 files changed, 3 insertions, 6 deletions

diff --git a/handshake_ntor.go b/handshake_ntor.go
index ea9de71..84cd93c 100644
--- a/handshake_ntor.go
+++ b/handshake_ntor.go
@@ -363,13 +363,10 @@ func findMark(mark, buf []byte, startPos, maxPos int) int {
 	return pos + startPos
 }
 
-func makePad(min, max int64) ([]byte, error) {
-	padLen, err := randRange(min, max)
-	if err != nil {
-		return nil, err
-	}
+func makePad(min, max int) ([]byte, error) {
+	padLen := randRange(min, max)
 	pad := make([]byte, padLen)
-	_, err = rand.Read(pad)
+	_, err := rand.Read(pad)
 	if err != nil {
 		return nil, err
 	}