Merge pull request #432 from neilalexander/gatekeeper

Implement session gatekeeper functions

cmd/yggdrasil/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"encoding/hex"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -20,22 +21,21 @@ import (
 
 	"github.com/yggdrasil-network/yggdrasil-go/src/admin"
 	"github.com/yggdrasil-network/yggdrasil-go/src/config"
+	"github.com/yggdrasil-network/yggdrasil-go/src/crypto"
 	"github.com/yggdrasil-network/yggdrasil-go/src/multicast"
 	"github.com/yggdrasil-network/yggdrasil-go/src/tuntap"
 	"github.com/yggdrasil-network/yggdrasil-go/src/yggdrasil"
 )
 
-type nodeConfig = config.NodeConfig
-type Core = yggdrasil.Core
-
 type node struct {
-	core      Core
+	core      yggdrasil.Core
+	state     *config.NodeState
 	tuntap    tuntap.TunAdapter
 	multicast multicast.Multicast
 	admin     admin.AdminSocket
 }
 
-func readConfig(useconf *bool, useconffile *string, normaliseconf *bool) *nodeConfig {
+func readConfig(useconf *bool, useconffile *string, normaliseconf *bool) *config.NodeConfig {
 	// Use a configuration file. If -useconf, the configuration will be read
 	// from stdin. If -useconffile, the configuration will be read from the
 	// filesystem.
@@ -116,7 +116,7 @@ func main() {
 	logging := flag.String("logging", "info,warn,error", "comma-separated list of logging levels to enable")
 	flag.Parse()
 
-	var cfg *nodeConfig
+	var cfg *config.NodeConfig
 	var err error
 	switch {
 	case *version:
@@ -181,18 +181,20 @@ func main() {
 	n := node{}
 	// Now start Yggdrasil - this starts the DHT, router, switch and other core
 	// components needed for Yggdrasil to operate
-	state, err := n.core.Start(cfg, logger)
+	n.state, err = n.core.Start(cfg, logger)
 	if err != nil {
 		logger.Errorln("An error occurred during startup")
 		panic(err)
 	}
+	// Register the session firewall gatekeeper function
+	n.core.SetSessionGatekeeper(n.sessionFirewall)
 	// Start the admin socket
-	n.admin.Init(&n.core, state, logger, nil)
+	n.admin.Init(&n.core, n.state, logger, nil)
 	if err := n.admin.Start(); err != nil {
 		logger.Errorln("An error occurred starting admin socket:", err)
 	}
 	// Start the multicast interface
-	n.multicast.Init(&n.core, state, logger, nil)
+	n.multicast.Init(&n.core, n.state, logger, nil)
 	if err := n.multicast.Start(); err != nil {
 		logger.Errorln("An error occurred starting multicast:", err)
 	}
@@ -200,7 +202,7 @@ func main() {
 	// Start the TUN/TAP interface
 	if listener, err := n.core.ConnListen(); err == nil {
 		if dialer, err := n.core.ConnDialer(); err == nil {
-			n.tuntap.Init(state, logger, listener, dialer)
+			n.tuntap.Init(n.state, logger, listener, dialer)
 			if err := n.tuntap.Start(); err != nil {
 				logger.Errorln("An error occurred starting TUN/TAP:", err)
 			}
@@ -251,3 +253,66 @@ func main() {
 	}
 exit:
 }
+
+func (n *node) sessionFirewall(pubkey *crypto.BoxPubKey, initiator bool) bool {
+	n.state.Mutex.RLock()
+	defer n.state.Mutex.RUnlock()
+
+	// Allow by default if the session firewall is disabled
+	if !n.state.Current.SessionFirewall.Enable {
+		return true
+	}
+
+	// Prepare for checking whitelist/blacklist
+	var box crypto.BoxPubKey
+	// Reject blacklisted nodes
+	for _, b := range n.state.Current.SessionFirewall.BlacklistEncryptionPublicKeys {
+		key, err := hex.DecodeString(b)
+		if err == nil {
+			copy(box[:crypto.BoxPubKeyLen], key)
+			if box == *pubkey {
+				return false
+			}
+		}
+	}
+
+	// Allow whitelisted nodes
+	for _, b := range n.state.Current.SessionFirewall.WhitelistEncryptionPublicKeys {
+		key, err := hex.DecodeString(b)
+		if err == nil {
+			copy(box[:crypto.BoxPubKeyLen], key)
+			if box == *pubkey {
+				return true
+			}
+		}
+	}
+
+	// Allow outbound sessions if appropriate
+	if n.state.Current.SessionFirewall.AlwaysAllowOutbound {
+		if initiator {
+			return true
+		}
+	}
+
+	// Look and see if the pubkey is that of a direct peer
+	var isDirectPeer bool
+	for _, peer := range n.core.GetPeers() {
+		if peer.PublicKey == *pubkey {
+			isDirectPeer = true
+			break
+		}
+	}
+
+	// Allow direct peers if appropriate
+	if n.state.Current.SessionFirewall.AllowFromDirect && isDirectPeer {
+		return true
+	}
+
+	// Allow remote nodes if appropriate
+	if n.state.Current.SessionFirewall.AllowFromRemote && !isDirectPeer {
+		return true
+	}
+
+	// Finally, default-deny if not matching any of the above rules
+	return false
+}

src/yggdrasil/api.go

@@ -395,6 +395,19 @@ func (c *Core) GetNodeInfo(keyString, coordString string, nocache bool) (NodeInf
 	return NodeInfoPayload{}, errors.New(fmt.Sprintf("getNodeInfo timeout: %s", keyString))
 }
 
+// SetSessionGatekeeper allows you to configure a handler function for deciding
+// whether a session should be allowed or not. The default session firewall is
+// implemented in this way. The function receives the public key of the remote
+// side and a boolean which is true if we initiated the session or false if we
+// received an incoming session request. The function should return true to
+// allow the session or false to reject it.
+func (c *Core) SetSessionGatekeeper(f func(pubkey *crypto.BoxPubKey, initiator bool) bool) {
+	c.sessions.isAllowedMutex.Lock()
+	defer c.sessions.isAllowedMutex.Unlock()
+
+	c.sessions.isAllowedHandler = f
+}
+
 // SetLogger sets the output logger of the Yggdrasil node after startup. This
 // may be useful if you want to redirect the output later.
 func (c *Core) SetLogger(log *log.Logger) {

src/yggdrasil/session.go

@@ -6,7 +6,6 @@ package yggdrasil
 
 import (
 	"bytes"
-	"encoding/hex"
 	"sync"
 	"time"
 
@@ -116,6 +115,8 @@ type sessions struct {
 	listenerMutex    sync.Mutex
 	reconfigure      chan chan error
 	lastCleanup      time.Time
+	isAllowedHandler func(pubkey *crypto.BoxPubKey, initiator bool) bool // Returns true or false if session setup is allowed
+	isAllowedMutex   sync.RWMutex                                        // Protects the above
 	permShared       map[crypto.BoxPubKey]*crypto.BoxSharedKey           // Maps known permanent keys to their shared key, used by DHT a lot
 	sinfos           map[crypto.Handle]*sessionInfo                      // Maps (secret) handle onto session info
 	conns            map[crypto.Handle]*Conn                             // Maps (secret) handle onto connections
@@ -155,70 +156,17 @@ func (ss *sessions) init(core *Core) {
 	ss.lastCleanup = time.Now()
 }
 
-// Determines whether the session firewall is enabled.
-func (ss *sessions) isSessionFirewallEnabled() bool {
-	ss.core.config.Mutex.RLock()
-	defer ss.core.config.Mutex.RUnlock()
-
-	return ss.core.config.Current.SessionFirewall.Enable
-}
-
 // 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.core.config.Mutex.RLock()
-	defer ss.core.config.Mutex.RUnlock()
+	ss.isAllowedMutex.RLock()
+	defer ss.isAllowedMutex.RUnlock()
 
-	// Allow by default if the session firewall is disabled
-	if !ss.isSessionFirewallEnabled() {
+	if ss.isAllowedHandler == nil {
 		return true
 	}
-	// Prepare for checking whitelist/blacklist
-	var box crypto.BoxPubKey
-	// Reject blacklisted nodes
-	for _, b := range ss.core.config.Current.SessionFirewall.BlacklistEncryptionPublicKeys {
-		key, err := hex.DecodeString(b)
-		if err == nil {
-			copy(box[:crypto.BoxPubKeyLen], key)
-			if box == *pubkey {
-				return false
-			}
-		}
-	}
-	// Allow whitelisted nodes
-	for _, b := range ss.core.config.Current.SessionFirewall.WhitelistEncryptionPublicKeys {
-		key, err := hex.DecodeString(b)
-		if err == nil {
-			copy(box[:crypto.BoxPubKeyLen], key)
-			if box == *pubkey {
-				return true
-			}
-		}
-	}
-	// Allow outbound sessions if appropriate
-	if ss.core.config.Current.SessionFirewall.AlwaysAllowOutbound {
-		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.core.config.Current.SessionFirewall.AllowFromDirect && isDirectPeer {
-		return true
-	}
-	// Allow remote nodes if appropriate
-	if ss.core.config.Current.SessionFirewall.AllowFromRemote && !isDirectPeer {
-		return true
-	}
-	// Finally, default-deny if not matching any of the above rules
-	return false
+
+	return ss.isAllowedHandler(pubkey, initiator)
 }
 
 // Gets the session corresponding to a given handle.
@@ -271,6 +219,7 @@ func (ss *sessions) getByTheirSubnet(snet *address.Subnet) (*sessionInfo, bool)
 // includse initializing session info to sane defaults (e.g. lowest supported
 // MTU).
 func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
+	// TODO: this check definitely needs to be moved
 	if !ss.isSessionAllowed(theirPermKey, true) {
 		return nil
 	}
@@ -444,12 +393,12 @@ 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.isSessionFirewallEnabled() {
-		if !ss.isSessionAllowed(&ping.SendPermPub, false) {
+	// Check if the session is allowed
+	// TODO: this check may need to be moved
+	if !isIn && !ss.isSessionAllowed(&ping.SendPermPub, false) {
 		return
 	}
-	}
+	// Create the session if it doesn't already exist
 	if !isIn {
 		ss.createSession(&ping.SendPermPub)
 		sinfo, isIn = ss.getByTheirPerm(&ping.SendPermPub)