From 125842d80dee1e16b9d6b7ebe8c05c2ec89d4b3f Mon Sep 17 00:00:00 2001
From: Lucas Clemente <lucas@clemente.io>
Date: Sat, 6 Aug 2016 17:54:11 +0200
Subject: [PATCH] simplify key derivation

---
 crypto/key_derivation.go | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/crypto/key_derivation.go b/crypto/key_derivation.go
index 37c98ddc3..cbd487758 100644
--- a/crypto/key_derivation.go
+++ b/crypto/key_derivation.go
@@ -43,23 +43,14 @@ func deriveKeys(version protocol.VersionNumber, forwardSecure bool, sharedSecret
 
 	r := hkdf.New(sha256.New, sharedSecret, nonces, info.Bytes())
 
-	otherKey := make([]byte, keyLen)
-	myKey := make([]byte, keyLen)
-	otherIV := make([]byte, 4)
-	myIV := make([]byte, 4)
-
-	if _, err := io.ReadFull(r, otherKey); err != nil {
-		return nil, nil, nil, nil, err
-	}
-	if _, err := io.ReadFull(r, myKey); err != nil {
-		return nil, nil, nil, nil, err
-	}
-	if _, err := io.ReadFull(r, otherIV); err != nil {
-		return nil, nil, nil, nil, err
-	}
-	if _, err := io.ReadFull(r, myIV); err != nil {
+	s := make([]byte, 2*keyLen+2*4)
+	if _, err := io.ReadFull(r, s); err != nil {
 		return nil, nil, nil, nil, err
 	}
+	otherKey := s[:keyLen]
+	myKey := s[keyLen : 2*keyLen]
+	otherIV := s[2*keyLen : 2*keyLen+4]
+	myIV := s[2*keyLen+4:]
 
 	if !forwardSecure && version >= protocol.Version33 {
 		if err := diversify(myKey, myIV, divNonce); err != nil {