From 51026d762ef9958353327f0180770b3e60e1555c Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Mon, 14 Jan 2019 18:24:35 +0000
Subject: [PATCH] Make session firewall thread-safe for config updates

---
 src/yggdrasil/session.go | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index 3c8e013..3cd1cf7 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -7,6 +7,7 @@ package yggdrasil
 import (
 	"bytes"
 	"encoding/hex"
+	"sync"
 	"time"
 
 	"github.com/yggdrasil-network/yggdrasil-go/src/address"
@@ -115,6 +116,7 @@ type sessions struct {
 	addrToPerm   map[address.Address]*crypto.BoxPubKey
 	subnetToPerm map[address.Subnet]*crypto.BoxPubKey
 	// Options from the session firewall
+	sessionFirewallMutex                sync.RWMutex
 	sessionFirewallEnabled              bool
 	sessionFirewallAllowsDirect         bool
 	sessionFirewallAllowsRemote         bool
@@ -157,12 +159,16 @@ func (ss *sessions) init(core *Core) {
 
 // Enable or disable the session firewall
 func (ss *sessions) setSessionFirewallState(enabled bool) {
+	ss.sessionFirewallMutex.Lock()
+	defer ss.sessionFirewallMutex.Unlock()
 	ss.sessionFirewallEnabled = enabled
 }
 
 // Set the session firewall defaults (first parameter is whether to allow
 // sessions from direct peers, second is whether to allow from remote nodes).
 func (ss *sessions) setSessionFirewallDefaults(allowsDirect bool, allowsRemote bool, alwaysAllowsOutbound bool) {
+	ss.sessionFirewallMutex.Lock()
+	defer ss.sessionFirewallMutex.Unlock()
 	ss.sessionFirewallAllowsDirect = allowsDirect
 	ss.sessionFirewallAllowsRemote = allowsRemote
 	ss.sessionFirewallAlwaysAllowsOutbound = alwaysAllowsOutbound
@@ -170,17 +176,24 @@ func (ss *sessions) setSessionFirewallDefaults(allowsDirect bool, allowsRemote b
 
 // Set the session firewall whitelist - nodes always allowed to open sessions.
 func (ss *sessions) setSessionFirewallWhitelist(whitelist []string) {
+	ss.sessionFirewallMutex.Lock()
+	defer ss.sessionFirewallMutex.Unlock()
 	ss.sessionFirewallWhitelist = whitelist
 }
 
 // Set the session firewall blacklist - nodes never allowed to open sessions.
 func (ss *sessions) setSessionFirewallBlacklist(blacklist []string) {
+	ss.sessionFirewallMutex.Lock()
+	defer ss.sessionFirewallMutex.Unlock()
 	ss.sessionFirewallBlacklist = blacklist
 }
 
 // Determines whether the session with a given publickey is allowed based on
 // session firewall rules.
 func (ss *sessions) isSessionAllowed(pubkey *crypto.BoxPubKey, initiator bool) bool {
+	ss.sessionFirewallMutex.RLock()
+	defer ss.sessionFirewallMutex.RUnlock()
+
 	// Allow by default if the session firewall is disabled
 	if !ss.sessionFirewallEnabled {
 		return true
@@ -286,10 +299,8 @@ func (ss *sessions) getByTheirSubnet(snet *address.Subnet) (*sessionInfo, bool)
 // Creates a new session and lazily cleans up old/timedout existing sessions.
 // This includse initializing session info to sane defaults (e.g. lowest supported MTU).
 func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
-	if ss.sessionFirewallEnabled {
-		if !ss.isSessionAllowed(theirPermKey, true) {
-			return nil
-		}
+	if !ss.isSessionAllowed(theirPermKey, true) {
+		return nil
 	}
 	sinfo := sessionInfo{}
 	sinfo.core = ss.core
@@ -465,11 +476,14 @@ func (ss *sessions) handlePing(ping *sessionPing) {
 	// Get the corresponding session (or create a new session)
 	sinfo, isIn := ss.getByTheirPerm(&ping.SendPermPub)
 	// Check the session firewall
+	ss.sessionFirewallMutex.RLock()
 	if !isIn && ss.sessionFirewallEnabled {
 		if !ss.isSessionAllowed(&ping.SendPermPub, false) {
+			ss.sessionFirewallMutex.RUnlock()
 			return
 		}
 	}
+	ss.sessionFirewallMutex.RUnlock()
 	if !isIn || sinfo.timedout() {
 		if isIn {
 			sinfo.close()