From 3af9aa88a310f7c2b86bae1ebb3ed3843424ce9e Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 3 Feb 2019 22:00:36 +0100
Subject: [PATCH] noise: store clamped key instead of raw key

---
 noise-helpers.go | 12 +++++++-----
 noise-types.go   |  6 ++++--
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/noise-helpers.go b/noise-helpers.go
index 1b2746c..af11f09 100644
--- a/noise-helpers.go
+++ b/noise-helpers.go
@@ -78,12 +78,14 @@ func setZero(arr []byte) {
 	}
 }
 
-func newPrivateKey() (sk NoisePrivateKey, err error) {
-	// clamping: https://cr.yp.to/ecdh.html
-	_, err = rand.Read(sk[:])
+func (sk *NoisePrivateKey) clamp() {
 	sk[0] &= 248
-	sk[31] &= 127
-	sk[31] |= 64
+	sk[31] = (sk[31] & 127) | 64
+}
+
+func newPrivateKey() (sk NoisePrivateKey, err error) {
+	_, err = rand.Read(sk[:])
+	sk.clamp()
 	return
 }
 
diff --git a/noise-types.go b/noise-types.go
index df6ee77..902905e 100644
--- a/noise-types.go
+++ b/noise-types.go
@@ -45,8 +45,10 @@ func (key NoisePrivateKey) Equals(tar NoisePrivateKey) bool {
 	return subtle.ConstantTimeCompare(key[:], tar[:]) == 1
 }
 
-func (key *NoisePrivateKey) FromHex(src string) error {
-	return loadExactHex(key[:], src)
+func (key *NoisePrivateKey) FromHex(src string) (err error) {
+	err = loadExactHex(key[:], src)
+	key.clamp()
+	return
 }
 
 func (key NoisePrivateKey) ToHex() string {