From 6026e0a014965a91d0d7ca8d63e0c285cbee2c75 Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Sun, 6 May 2018 16:32:34 -0500
Subject: [PATCH] Optional peer authentication, if non-empty then incoming TCP
 and all UDP peers must match one of these box keys

---
 src/yggdrasil/config/config.go |  1 +
 src/yggdrasil/debug.go         |  6 ++++++
 src/yggdrasil/peer.go          | 13 ++++++++++---
 src/yggdrasil/tcp.go           | 17 +++++++++++++----
 src/yggdrasil/udp.go           |  8 ++++++++
 yggdrasil.go                   |  7 +++++++
 6 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/src/yggdrasil/config/config.go b/src/yggdrasil/config/config.go
index 30c8d23..d1b58a9 100644
--- a/src/yggdrasil/config/config.go
+++ b/src/yggdrasil/config/config.go
@@ -5,6 +5,7 @@ type NodeConfig struct {
 	Listen      string
 	AdminListen string
 	Peers       []string
+	PeerBoxPubs []string
 	BoxPub      string
 	BoxPriv     string
 	SigPub      string
diff --git a/src/yggdrasil/debug.go b/src/yggdrasil/debug.go
index f87bb75..5358379 100644
--- a/src/yggdrasil/debug.go
+++ b/src/yggdrasil/debug.go
@@ -397,6 +397,12 @@ func (c *Core) DEBUG_setIfceExpr(expr *regexp.Regexp) {
 	c.ifceExpr = expr
 }
 
+func (c *Core) DEBUG_addAuthBoxPub(boxBytes []byte) {
+	var box boxPubKey
+	copy(box[:], boxBytes)
+	c.peers.authBoxPubs[box] = struct{}{}
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 func DEBUG_simLinkPeers(p, q *peer) {
diff --git a/src/yggdrasil/peer.go b/src/yggdrasil/peer.go
index ea05728..c32557d 100644
--- a/src/yggdrasil/peer.go
+++ b/src/yggdrasil/peer.go
@@ -30,9 +30,10 @@ import "math"
 //import "fmt"
 
 type peers struct {
-	core  *Core
-	mutex sync.Mutex   // Synchronize writes to atomic
-	ports atomic.Value //map[Port]*peer, use CoW semantics
+	core        *Core
+	authBoxPubs map[boxPubKey]struct{}
+	mutex       sync.Mutex   // Synchronize writes to atomic
+	ports       atomic.Value //map[Port]*peer, use CoW semantics
 	//ports map[Port]*peer
 }
 
@@ -41,6 +42,12 @@ func (ps *peers) init(c *Core) {
 	defer ps.mutex.Unlock()
 	ps.putPorts(make(map[switchPort]*peer))
 	ps.core = c
+	ps.authBoxPubs = make(map[boxPubKey]struct{})
+}
+
+func (ps *peers) isAuthBoxPub(box *boxPubKey) bool {
+	_, isIn := ps.authBoxPubs[*box]
+	return isIn || len(ps.authBoxPubs) == 0
 }
 
 func (ps *peers) getPorts() map[switchPort]*peer {
diff --git a/src/yggdrasil/tcp.go b/src/yggdrasil/tcp.go
index 3a4e9fb..be2ba83 100644
--- a/src/yggdrasil/tcp.go
+++ b/src/yggdrasil/tcp.go
@@ -62,7 +62,7 @@ func (iface *tcpInterface) listener() {
 		if err != nil {
 			panic(err)
 		}
-		go iface.handler(sock)
+		go iface.handler(sock, true)
 	}
 }
 
@@ -81,7 +81,7 @@ func (iface *tcpInterface) callWithConn(conn net.Conn) {
 				delete(iface.calls, raddr)
 				iface.mutex.Unlock()
 			}()
-			iface.handler(conn)
+			iface.handler(conn, false)
 		}
 	}()
 }
@@ -106,12 +106,12 @@ func (iface *tcpInterface) call(saddr string) {
 			if err != nil {
 				return
 			}
-			iface.handler(conn)
+			iface.handler(conn, false)
 		}
 	}()
 }
 
-func (iface *tcpInterface) handler(sock net.Conn) {
+func (iface *tcpInterface) handler(sock net.Conn, incoming bool) {
 	defer sock.Close()
 	// Get our keys
 	keys := []byte{}
@@ -150,6 +150,15 @@ func (iface *tcpInterface) handler(sock net.Conn) {
 	if equiv(info.sig[:], iface.core.sigPub[:]) {
 		return
 	}
+	// Check if we're authorized to connect to this key / IP
+	if incoming && !iface.core.peers.isAuthBoxPub(&info.box) {
+		// Allow unauthorized peers if they're link-local
+		raddrStr, _, _ := net.SplitHostPort(sock.RemoteAddr().String())
+		raddr := net.ParseIP(raddrStr)
+		if !raddr.IsLinkLocalUnicast() {
+			return
+		}
+	}
 	// Check if we already have a connection to this node, close and block if yes
 	info.localAddr, _, _ = net.SplitHostPort(sock.LocalAddr().String())
 	info.remoteAddr, _, _ = net.SplitHostPort(sock.RemoteAddr().String())
diff --git a/src/yggdrasil/udp.go b/src/yggdrasil/udp.go
index fffda93..53aaec1 100644
--- a/src/yggdrasil/udp.go
+++ b/src/yggdrasil/udp.go
@@ -204,6 +204,14 @@ func (iface *udpInterface) handleKeys(msg []byte, addr connAddr) {
 	iface.mutex.RUnlock()
 	if !isIn {
 		udpAddr := addr.toUDPAddr()
+		// Check if we're authorized to connect to this key / IP
+		// TODO monitor and always allow outgoing connections
+		if !iface.core.peers.isAuthBoxPub(&ks.box) {
+			// Allow unauthorized peers if they're link-local
+			if !udpAddr.IP.IsLinkLocalUnicast() {
+				return
+			}
+		}
 		themNodeID := getNodeID(&ks.box)
 		themAddr := address_addrForNodeID(themNodeID)
 		themAddrString := net.IP(themAddr[:]).String()
diff --git a/yggdrasil.go b/yggdrasil.go
index 30c6a79..e2b75ae 100644
--- a/yggdrasil.go
+++ b/yggdrasil.go
@@ -58,6 +58,13 @@ func (n *node) init(cfg *nodeConfig, logger *log.Logger) {
 		panic(err)
 	}
 	n.core.DEBUG_setIfceExpr(ifceExpr)
+	for _, pBoxStr := range cfg.PeerBoxPubs {
+		pbox, err := hex.DecodeString(pBoxStr)
+		if err != nil {
+			panic(err)
+		}
+		n.core.DEBUG_addAuthBoxPub(pbox)
+	}
 
 	logger.Println("Starting interface...")
 	n.core.DEBUG_setupAndStartGlobalTCPInterface(cfg.Listen) // Listen for peers on TCP