Merge pull request #187 from neilalexander/sessionfirewall

Add session firewall

src/yggdrasil/config/config.go

@@ -16,6 +16,7 @@ type NodeConfig struct {
 	IfName                      string              `comment:"Local network interface name for TUN/TAP adapter, or \"auto\" to select\nan interface automatically, or \"none\" to run without TUN/TAP."`
 	IfTAPMode                   bool                `comment:"Set local network interface to TAP mode rather than TUN mode if\nsupported by your platform - option will be ignored if not."`
 	IfMTU                       int                 `comment:"Maximux Transmission Unit (MTU) size for your local TUN/TAP interface.\nDefault is the largest supported size for your platform. The lowest\npossible value is 1280."`
+	SessionFirewall             SessionFirewall     `comment:"The session firewall controls who can send/receive network traffic\nto/from. This is useful if you want to protect this node without\nresorting to using a real firewall. This does not affect traffic\nbeing routed via this node to somewhere else. Rules are prioritised as\nfollows: whitelist, blacklist, always allow outgoing, direct, remote."`
 	//Net                         NetConfig `comment:"Extended options for connecting to peers over other networks."`
 }
 
@@ -24,3 +25,12 @@ type NetConfig struct {
 	Tor TorConfig `comment:"Experimental options for configuring peerings over Tor."`
 	I2P I2PConfig `comment:"Experimental options for configuring peerings over I2P."`
 }
+
+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

@@ -107,6 +107,15 @@ func (c *Core) Start(nc *config.NodeConfig, log *log.Logger) error {
 		return err
 	}
 
+	c.sessions.setSessionFirewallState(nc.SessionFirewall.Enable)
+	c.sessions.setSessionFirewallDefaults(
+		nc.SessionFirewall.AllowFromDirect,
+		nc.SessionFirewall.AllowFromRemote,
+		nc.SessionFirewall.AlwaysAllowOutbound,
+	)
+	c.sessions.setSessionFirewallWhitelist(nc.SessionFirewall.WhitelistEncryptionPublicKeys)
+	c.sessions.setSessionFirewallBlacklist(nc.SessionFirewall.BlacklistEncryptionPublicKeys)
+
 	if err := c.router.start(); err != nil {
 		c.log.Println("Failed to start router")
 		return err

src/yggdrasil/peer.go

@@ -17,7 +17,7 @@ import (
 type peers struct {
 	core                        *Core
 	mutex                       sync.Mutex   // Synchronize writes to atomic
-	ports                       atomic.Value //map[Port]*peer, use CoW semantics
+	ports                       atomic.Value //map[switchPort]*peer, use CoW semantics
 	authMutex                   sync.RWMutex
 	allowedEncryptionPublicKeys map[boxPubKey]struct{}
 }

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

@@ -6,6 +6,7 @@ package yggdrasil
 
 import (
 	"bytes"
+	"encoding/hex"
 	"time"
 )
 
@@ -107,6 +108,13 @@ type sessions struct {
 	byTheirPerm  map[boxPubKey]*handle
 	addrToPerm   map[address]*boxPubKey
 	subnetToPerm map[subnet]*boxPubKey
+	// Options from the session firewall
+	sessionFirewallEnabled              bool
+	sessionFirewallAllowsDirect         bool
+	sessionFirewallAllowsRemote         bool
+	sessionFirewallAlwaysAllowsOutbound bool
+	sessionFirewallWhitelist            []string
+	sessionFirewallBlacklist            []string
 }
 
 // Initializes the session struct.
@@ -121,6 +129,84 @@ func (ss *sessions) init(core *Core) {
 	ss.lastCleanup = time.Now()
 }
 
+// Enable or disable the session firewall
+func (ss *sessions) setSessionFirewallState(enabled bool) {
+	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.sessionFirewallAllowsDirect = allowsDirect
+	ss.sessionFirewallAllowsRemote = allowsRemote
+	ss.sessionFirewallAlwaysAllowsOutbound = alwaysAllowsOutbound
+}
+
+// Set the session firewall whitelist - nodes always allowed to open sessions.
+func (ss *sessions) setSessionFirewallWhitelist(whitelist []string) {
+	ss.sessionFirewallWhitelist = whitelist
+}
+
+// Set the session firewall blacklist - nodes never allowed to open sessions.
+func (ss *sessions) setSessionFirewallBlacklist(blacklist []string) {
+	ss.sessionFirewallBlacklist = blacklist
+}
+
+// Determines whether the session with a given publickey is allowed based on
+// session firewall rules.
+func (ss *sessions) isSessionAllowed(pubkey *boxPubKey, initiator bool) bool {
+	// Allow by default if the session firewall is disabled
+	if !ss.sessionFirewallEnabled {
+		return true
+	}
+	// Prepare for checking whitelist/blacklist
+	var box boxPubKey
+	// Reject blacklisted nodes
+	for _, b := range ss.sessionFirewallBlacklist {
+		key, err := hex.DecodeString(b)
+		if err == nil {
+			copy(box[:boxPubKeyLen], key)
+			if box == *pubkey {
+				return false
+			}
+		}
+	}
+	// Allow whitelisted nodes
+	for _, b := range ss.sessionFirewallWhitelist {
+		key, err := hex.DecodeString(b)
+		if err == nil {
+			copy(box[:boxPubKeyLen], key)
+			if box == *pubkey {
+				return true
+			}
+		}
+	}
+	// 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) {
+		if peer.box == *pubkey {
+			isDirectPeer = true
+			break
+		}
+	}
+	// Allow direct peers if appropriate
+	if ss.sessionFirewallAllowsDirect && isDirectPeer {
+		return true
+	}
+	// Allow remote nodes if appropriate
+	if ss.sessionFirewallAllowsRemote && !isDirectPeer {
+		return true
+	}
+	// Finally, default-deny if not matching any of the above rules
+	return false
+}
+
 // Gets the session corresponding to a given handle.
 func (ss *sessions) getSessionForHandle(handle *handle) (*sessionInfo, bool) {
 	sinfo, isIn := ss.sinfos[*handle]
@@ -174,6 +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
@@ -311,6 +402,12 @@ func (ss *sessions) sendPingPong(sinfo *sessionInfo, isPong bool) {
 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
+	if !isIn && ss.sessionFirewallEnabled {
+		if !ss.isSessionAllowed(&ping.SendPermPub, false) {
+			return
+		}
+	}
 	if !isIn || sinfo.timedout() {
 		if isIn {
 			sinfo.close()

yggdrasil.go

@@ -66,6 +66,9 @@ func generateConfig(isAutoconf bool) *nodeConfig {
 	cfg.IfName = defaults.GetDefaults().DefaultIfName
 	cfg.IfMTU = defaults.GetDefaults().DefaultIfMTU
 	cfg.IfTAPMode = defaults.GetDefaults().DefaultIfTAPMode
+	cfg.SessionFirewall.Enable = false
+	cfg.SessionFirewall.AllowFromDirect = true
+	cfg.SessionFirewall.AllowFromRemote = true
 
 	return &cfg
 }