From 27b78b925df96183b7e45fd5f3a4802e3c36cc98 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Fri, 19 Apr 2019 21:23:15 +0100
Subject: [PATCH] Move mutexes around

---
 src/yggdrasil/conn.go    | 30 +++++++++++++++++++-----------
 src/yggdrasil/session.go | 12 ------------
 2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/src/yggdrasil/conn.go b/src/yggdrasil/conn.go
index fd65743c..e337b34f 100644
--- a/src/yggdrasil/conn.go
+++ b/src/yggdrasil/conn.go
@@ -73,18 +73,26 @@ func (c *Conn) Read(b []byte) (int, error) {
 			return 0, errors.New("session was closed")
 		}
 		defer util.PutBytes(p.Payload)
-		if !c.session.nonceIsOK(&p.Nonce) {
-			return 0, errors.New("packet dropped due to invalid nonce")
+		err := func() error {
+			c.session.theirNonceMutex.Lock()
+			defer c.session.theirNonceMutex.Unlock()
+			if !c.session.nonceIsOK(&p.Nonce) {
+				return errors.New("packet dropped due to invalid nonce")
+			}
+			bs, isOK := crypto.BoxOpen(&c.session.sharedSesKey, p.Payload, &p.Nonce)
+			if !isOK {
+				util.PutBytes(bs)
+				return errors.New("packet dropped due to decryption failure")
+			}
+			b = b[:0]
+			b = append(b, bs...)
+			c.session.updateNonce(&p.Nonce)
+			c.session.time = time.Now()
+			return nil
+		}()
+		if err != nil {
+			return 0, err
 		}
-		bs, isOK := crypto.BoxOpen(&c.session.sharedSesKey, p.Payload, &p.Nonce)
-		if !isOK {
-			util.PutBytes(bs)
-			return 0, errors.New("packet dropped due to decryption failure")
-		}
-		b = b[:0]
-		b = append(b, bs...)
-		c.session.updateNonce(&p.Nonce)
-		c.session.time = time.Now()
 		atomic.AddUint64(&c.session.bytesRecvd, uint64(len(b)))
 		return len(b), nil
 	case <-c.session.closed:
diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index e46761d5..c5319bc7 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -79,10 +79,8 @@ func (s *sessionInfo) update(p *sessionPing) bool {
 		s.theirSesPub = p.SendSesPub
 		s.theirHandle = p.Handle
 		s.sharedSesKey = *crypto.GetSharedKey(&s.mySesPriv, &s.theirSesPub)
-		s.theirNonceMutex.Lock()
 		s.theirNonce = crypto.BoxNonce{}
 		s.theirNonceMask = 0
-		s.theirNonceMutex.Unlock()
 	}
 	if p.MTU >= 1280 || p.MTU == 0 {
 		s.theirMTU = p.MTU
@@ -272,10 +270,6 @@ func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
 		return nil
 	}
 	sinfo := sessionInfo{}
-	sinfo.myNonceMutex.Lock()
-	sinfo.theirNonceMutex.Lock()
-	defer sinfo.myNonceMutex.Unlock()
-	defer sinfo.theirNonceMutex.Unlock()
 	sinfo.core = ss.core
 	sinfo.reconfigure = make(chan chan error, 1)
 	sinfo.theirPermPub = *theirPermKey
@@ -395,9 +389,7 @@ func (ss *sessions) getPing(sinfo *sessionInfo) sessionPing {
 		Coords:      coords,
 		MTU:         sinfo.myMTU,
 	}
-	sinfo.myNonceMutex.Lock()
 	sinfo.myNonce.Increment()
-	sinfo.myNonceMutex.Unlock()
 	return ref
 }
 
@@ -501,8 +493,6 @@ func (sinfo *sessionInfo) getMTU() uint16 {
 // Checks if a packet's nonce is recent enough to fall within the window of allowed packets, and not already received.
 func (sinfo *sessionInfo) nonceIsOK(theirNonce *crypto.BoxNonce) bool {
 	// The bitmask is to allow for some non-duplicate out-of-order packets
-	sinfo.theirNonceMutex.Lock()
-	defer sinfo.theirNonceMutex.Unlock()
 	diff := theirNonce.Minus(&sinfo.theirNonce)
 	if diff > 0 {
 		return true
@@ -512,8 +502,6 @@ func (sinfo *sessionInfo) nonceIsOK(theirNonce *crypto.BoxNonce) bool {
 
 // Updates the nonce mask by (possibly) shifting the bitmask and setting the bit corresponding to this nonce to 1, and then updating the most recent nonce
 func (sinfo *sessionInfo) updateNonce(theirNonce *crypto.BoxNonce) {
-	sinfo.theirNonceMutex.Lock()
-	defer sinfo.theirNonceMutex.Unlock()
 	// Shift nonce mask if needed
 	// Set bit
 	diff := theirNonce.Minus(&sinfo.theirNonce)