Added rekeying (-r secs) client/server

xsnet/chan.go

@@ -57,9 +57,9 @@ func expandKeyMat(keymat []byte, blocksize int) []byte {
 	return keymat
 }
 
-/* Support functionality to set up encryption after a channel has
-been negotiated via xsnet.go
-*/
+/* (Re-)initialize the keystream and hmac state for an xsnet.Conn, returning
+   a cipherStream and hash
+ */
 func (hc *Conn) getStream(keymat []byte) (rc cipher.Stream, mc hash.Hash, err error) {
 	var key []byte
 	var block cipher.Block

xsnet/consts.go

@@ -78,6 +78,7 @@ const (
 	CSOTunDisconn   // server -> client: tunnel rport disconnected
 	CSOTunHangup    // client -> server: tunnel lport hung up
 	CSOKeepAlive    // bidir keepalive packet to monitor main connection
+	CSORekey        // TODO: rekey/re-select session cipher/hash algs
 )
 
 // TunEndpoint.tunCtl control values - used to control workers for client

xsnet/net.go

@@ -88,6 +88,7 @@ type (
 		Cols       uint16
 
 		keepalive uint // if this reaches zero, conn is considered dead
+		rekey     uint // if nonzero, rekeying interval in seconds
 		Pproc     int  // proc ID of command run on this conn
 		chaff     ChaffConfig
 		tuns      *map[uint16](*TunEndpoint)
@@ -1345,6 +1346,12 @@ func (hc *Conn) Read(b []byte) (n int, err error) {
 				// payload of keepalive (2 bytes) is not currently used (0x55aa fixed)
 				_ = binary.BigEndian.Uint16(payloadBytes[0:2])
 				hc.ResetKeepAlive()
+			case CSORekey:
+				// rekey
+				//logger.LogDebug(fmt.Sprintf("[Got rekey [%02x %02x %02x ...]\n",
+				//	payloadBytes[0], payloadBytes[1], payloadBytes[2]))
+				rekeyData := payloadBytes
+				hc.r, hc.rm, err = hc.getStream(rekeyData)
 			case CSOTermSize:
 				fmt.Sscanf(string(payloadBytes), "%d %d", &hc.Rows, &hc.Cols)
 				log.Printf("[TermSize pkt: rows %v cols %v]\n", hc.Rows, hc.Cols)
@@ -1461,13 +1468,18 @@ func (hc *Conn) Read(b []byte) (n int, err error) {
 // Write a byte slice
 //
 // See go doc io.Writer
-func (hc Conn) Write(b []byte) (n int, err error) {
+func (hc *Conn) Write(b []byte) (n int, err error) {
+	//logger.LogDebug("[+Write]")
 	n, err = hc.WritePacket(b, CSONone)
+	//logger.LogDebug("[-Write]")
 	return n, err
 }
 
 // Write a byte slice with specified ctrlStatOp byte
 func (hc *Conn) WritePacket(b []byte, ctrlStatOp byte) (n int, err error) {
+	hc.Lock()
+	defer hc.Unlock()
+
 	//log.Printf("[Encrypting...]\r\n")
 	var hmacOut []uint8
 	var payloadLen uint32
@@ -1495,15 +1507,6 @@ func (hc *Conn) WritePacket(b []byte, ctrlStatOp byte) (n int, err error) {
 		b = append([]byte{byte(padSide)}, append([]byte{byte(padLen)}, append(b, padBytes...)...)...)
 	}
 
-	// N.B. Originally this Lock() surrounded only the
-	// calls to binary.Write(hc.c ..) however there appears
-	// to be some other unshareable state in the Conn
-	// struct that must be protected to serialize main and
-	// chaff data written to it.
-	//
-	// Would be nice to determine if the mutex scope
-	// could be tightened.
-	hc.Lock()
 	payloadLen = uint32(len(b))
 	if hc.logPlainText {
 		log.Printf("  >:ptext:\r\n%s\r\n", hex.Dump(b[0:payloadLen]))
@@ -1561,7 +1564,6 @@ func (hc *Conn) WritePacket(b []byte, ctrlStatOp byte) (n int, err error) {
 	} else {
 		//fmt.Println("[a]WriteError!")
 	}
-	hc.Unlock()
 
 	if err != nil {
 		log.Println(err)
@@ -1593,6 +1595,40 @@ func (hc *Conn) SetupChaff(msecsMin uint, msecsMax uint, szMax uint) {
 	hc.chaff.szMax = szMax
 }
 
+func (hc *Conn) ShutdownRekey() {
+	hc.rekey = 0
+}
+
+func (hc *Conn) RekeyHelper(intervalSecs uint) {
+	go func() {
+		hc.rekey = intervalSecs
+		for {
+			if hc.rekey != 0 {
+				//logger.LogDebug(fmt.Sprintf("[rekeyHelper Loop]\n"))
+				time.Sleep(time.Duration(hc.rekey) * time.Second)
+
+				// Send rekey to other end
+				rekeyData := make([]byte, 64)
+				_, err := crand.Read(rekeyData)
+				//logger.LogDebug(fmt.Sprintf("[rekey [%02x %02x %02x ...]\n",
+				//	rekeyData[0], rekeyData[1], rekeyData[2]))
+				//logger.LogDebug("[+rekeyHelper]")
+				_, err = hc.WritePacket(rekeyData, CSORekey)
+				hc.Lock()
+				hc.w, hc.wm, err = hc.getStream(rekeyData)
+				//logger.LogDebug("[-rekeyHelper]")
+				hc.Unlock()
+				if err != nil {
+					log.Printf("[rekey WritePacket err! (%v) rekey dying ...]\n", err)
+					return
+				}
+			} else {
+				return
+			}
+		}
+	}()
+}
+
 // Helper routine to spawn a chaffing goroutine for each Conn
 func (hc *Conn) chaffHelper() {
 	go func() {
@@ -1605,7 +1641,9 @@ func (hc *Conn) chaffHelper() {
 				min := int(hc.chaff.msecsMin)
 				nextDuration = rand.Intn(int(hc.chaff.msecsMax)-min) + min
 				_, _ = rand.Read(bufTmp)
+				//logger.LogDebug("[+chaffHelper]")
 				_, err := hc.WritePacket(bufTmp, CSOChaff)
+				//logger.LogDebug("[-chaffHelper]")
 				if err != nil {
 					log.Println("[ *** error - chaffHelper shutting down *** ]")
 					hc.chaff.shutdown = true
@@ -1642,7 +1680,9 @@ func (hc *Conn) keepaliveHelper() {
 		for {
 			nextDuration := 10000
 			bufTmp := []byte{0x55, 0xaa}
+			//logger.LogDebug("[+keepaliveHelper]")
 			_, err := hc.WritePacket(bufTmp, CSOKeepAlive)
+			//logger.LogDebug("[-keepaliveHelper]")
 			//logger.LogDebug(fmt.Sprintf("[keepalive]\n"))
 			if err != nil {
 				logger.LogDebug(fmt.Sprintf("[ *** error - keepaliveHelper quitting *** ]\n"))