From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Sun, 3 Feb 2019 01:08:16 +0000 (+0100)
Subject: tai64n: whiten nano seconds
X-Git-Tag: 0.0.20190409~123
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a5ca02d79a953c883694061bba5c683b220fbfe4;p=thirdparty%2Fwireguard-go.git

tai64n: whiten nano seconds

Avoid being too precise of a time oracle.
---

diff --git a/tai64n/tai64n.go b/tai64n/tai64n.go
index f402f05..565aaa4 100644
--- a/tai64n/tai64n.go
+++ b/tai64n/tai64n.go
@@ -12,7 +12,8 @@ import (
 )
 
 const TimestampSize = 12
-const base = uint64(4611686018427387914)
+const base = uint64(0x400000000000000a)
+const whitenerMask = uint32(0x1000000 - 1)
 
 type Timestamp [TimestampSize]byte
 
@@ -20,7 +21,7 @@ func Now() Timestamp {
 	var tai64n Timestamp
 	now := time.Now()
 	secs := base + uint64(now.Unix())
-	nano := uint32(now.Nanosecond())
+	nano := uint32(now.Nanosecond()) &^ whitenerMask
 	binary.BigEndian.PutUint64(tai64n[:], secs)
 	binary.BigEndian.PutUint32(tai64n[8:], nano)
 	return tai64n