Add AlwaysAllowOutbound to session firewall

src/yggdrasil/config/config.go

@@ -30,6 +30,7 @@ type SessionFirewall struct {
 	Enable                        bool     `comment:"Enable or disable the session firewall. If disabled, network traffic\nfrom any node will be allowed. If enabled, the below rules apply."`
 	AllowFromDirect               bool     `comment:"Allow network traffic from directly connected peers."`
 	AllowFromRemote               bool     `comment:"Allow network traffic from remote nodes on the network that you are\nnot directly peered with."`
+	AlwaysAllowOutbound           bool     `comment:"Allow outbound network traffic regardless of AllowFromDirect or\nAllowFromRemote. This does allow a remote node to send unsolicited\ntraffic back to you for the length of the session."`
 	WhitelistEncryptionPublicKeys []string `comment:"List of public keys from which network traffic is always accepted,\nregardless of AllowFromDirect or AllowFromRemote."`
 	BlacklistEncryptionPublicKeys []string `comment:"List of public keys from which network traffic is always rejected,\nregardless of the whitelist, AllowFromDirect or AllowFromRemote."`
 }

src/yggdrasil/core.go

@@ -108,7 +108,11 @@ func (c *Core) Start(nc *config.NodeConfig, log *log.Logger) error {
 	}
 
 	c.sessions.setSessionFirewallState(nc.SessionFirewall.Enable)
-	c.sessions.setSessionFirewallDefaults(nc.SessionFirewall.AllowFromDirect, nc.SessionFirewall.AllowFromRemote)
+	c.sessions.setSessionFirewallDefaults(
+		nc.SessionFirewall.AllowFromDirect,
+		nc.SessionFirewall.AllowFromRemote,
+		nc.SessionFirewall.AlwaysAllowOutbound,
+	)
 	c.sessions.setSessionFirewallWhitelist(nc.SessionFirewall.WhitelistEncryptionPublicKeys)
 	c.sessions.setSessionFirewallBlacklist(nc.SessionFirewall.BlacklistEncryptionPublicKeys)
 

src/yggdrasil/search.go

@@ -184,6 +184,10 @@ func (s *searches) checkDHTRes(info *searchInfo, res *dhtRes) bool {
 	sinfo, isIn := s.core.sessions.getByTheirPerm(&res.Key)
 	if !isIn {
 		sinfo = s.core.sessions.createSession(&res.Key)
+		if sinfo == nil {
+			// nil if the DHT search finished but the session wasn't allowed
+			return true
+		}
 		_, isIn := s.core.sessions.getByTheirPerm(&res.Key)
 		if !isIn {
 			panic("This should never happen")

src/yggdrasil/session.go

@@ -112,6 +112,7 @@ type sessions struct {
 	sessionFirewallEnabled              bool
 	sessionFirewallAllowsDirect         bool
 	sessionFirewallAllowsRemote         bool
+	sessionFirewallAlwaysAllowsOutbound bool
 	sessionFirewallWhitelist            []string
 	sessionFirewallBlacklist            []string
 }
@@ -135,9 +136,10 @@ func (ss *sessions) setSessionFirewallState(enabled bool) {
 
 // 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) {
+func (ss *sessions) setSessionFirewallDefaults(allowsDirect bool, allowsRemote bool, alwaysAllowsOutbound bool) {
 	ss.sessionFirewallAllowsDirect = allowsDirect
 	ss.sessionFirewallAllowsRemote = allowsRemote
+	ss.sessionFirewallAlwaysAllowsOutbound = alwaysAllowsOutbound
 }
 
 // Set the session firewall whitelist - nodes always allowed to open sessions.
@@ -152,7 +154,7 @@ func (ss *sessions) setSessionFirewallBlacklist(blacklist []string) {
 
 // Determines whether the session with a given publickey is allowed based on
 // session firewall rules.
-func (ss *sessions) isSessionAllowed(pubkey *boxPubKey) bool {
+func (ss *sessions) isSessionAllowed(pubkey *boxPubKey, initiator bool) bool {
 	// Allow by default if the session firewall is disabled
 	if !ss.sessionFirewallEnabled {
 		return true
@@ -179,6 +181,12 @@ func (ss *sessions) isSessionAllowed(pubkey *boxPubKey) bool {
 			}
 		}
 	}
+	// Allow outbound sessions if appropriate
+	if ss.sessionFirewallAlwaysAllowsOutbound {
+		if initiator {
+			return true
+		}
+	}
 	// Look and see if the pubkey is that of a direct peer
 	var isDirectPeer bool
 	for _, peer := range ss.core.peers.ports.Load().(map[switchPort]*peer) {
@@ -252,6 +260,11 @@ func (ss *sessions) getByTheirSubnet(snet *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 *boxPubKey) *sessionInfo {
+	if ss.sessionFirewallEnabled {
+		if !ss.isSessionAllowed(theirPermKey, true) {
+			return nil
+		}
+	}
 	sinfo := sessionInfo{}
 	sinfo.core = ss.core
 	sinfo.theirPermPub = *theirPermKey
@@ -391,7 +404,7 @@ func (ss *sessions) handlePing(ping *sessionPing) {
 	sinfo, isIn := ss.getByTheirPerm(&ping.SendPermPub)
 	// Check the session firewall
 	if !isIn && ss.sessionFirewallEnabled {
-		if !ss.isSessionAllowed(&ping.SendPermPub) {
+		if !ss.isSessionAllowed(&ping.SendPermPub, false) {
 			return
 		}
 	}