fixed issue with prefix flag, removed checking for default interface and gateway

Author: shadowy-pycoder

README.md

@@ -35,6 +35,8 @@ Usage of nf:
         Enable NA (neighbor advertisement) spoofing
   -nocolor
         Disable colored output
+  -p string
+        IPv6 prefix for RA spoofing
   -ra
         Enable RA (router advertisement) spoofing. It is enabled when no spoof mode specified)
   -rdnss
@@ -49,3 +51,25 @@ Usage of nf:
 ### Usage as a library
 
 See [https://github.com/shadowy-pycoder/go-http-proxy-to-socks](https://github.com/shadowy-pycoder/go-http-proxy-to-socks)
+
+### Example lab to test this tool
+
+![Test RA lab](resources/RA_test.png)
+
+1. Kali machine with Host-only network vboxnet0
+2. Mint machine with Host-only network vboxnet1
+3. Cisco IOS on Linux (IOL) Layer 2 Advanced Enterprise K9, Version 17.16.01a (x86_64)
+
+On Kali machine run:
+
+```shell
+nf -d -auto -ra -i eth0 -p 2001:db8:7a31:4400::/64
+```
+
+On Mint machine run:
+
+```shell
+ip -6 route
+```
+
+You should see Kali machine link local IP as a default gateway

cmd/nf/main.go

@@ -70,9 +70,6 @@ func root(args []string) error {
 	})
 	flags.DurationVar(&conf.RouterLifetime, "rlt", time.Duration(600*time.Second), "Router lifetime for RA spoofing")
 	flags.DurationVar(&conf.PacketInterval, "interval", time.Duration(5*time.Second), "Interval between sent packets")
-	if err := flags.Parse(args); err != nil {
-		return err
-	}
 	prefix := flags.String("p", "", "IPv6 prefix for RA spoofing")
 	if err := flags.Parse(args); err != nil {
 		return err

ndpspoof.go

@@ -322,25 +322,23 @@ func (nr *NDPSpoofer) NeighCache() *NeighCache {
 
 func NewNDPSpoofer(conf *NDPSpoofConfig) (*NDPSpoofer, error) {
 	ndpspoofer := &NDPSpoofer{}
-	var iface *net.Interface
 	var err error
 	if !conf.RA && !conf.NA {
 		return nil, fmt.Errorf("no attack vectors enabled")
 	}
-	iface, err = network.GetDefaultInterface()
-	if err != nil {
-		iface, err = network.GetDefaultInterfaceFromRouteIPv6()
-		if err != nil {
-			return nil, err
-		}
-	}
 	if conf.Interface != "" {
 		ndpspoofer.iface, err = net.InterfaceByName(conf.Interface)
 		if err != nil {
 			return nil, err
 		}
 	} else {
-		ndpspoofer.iface = iface
+		ndpspoofer.iface, err = network.GetDefaultInterface()
+		if err != nil {
+			ndpspoofer.iface, err = network.GetDefaultInterfaceFromRouteIPv6()
+			if err != nil {
+				return nil, err
+			}
+		}
 	}
 	prefixLocal, err := network.GetIPv6LinkLocalUnicastPrefixFromInterface(ndpspoofer.iface)
 	if err != nil {
@@ -353,26 +351,6 @@ func NewNDPSpoofer(conf *NDPSpoofConfig) (*NDPSpoofer, error) {
 	if err == nil {
 		ndpspoofer.hostIPGlobal = &hostIPGlobal
 	}
-	if conf.Gateway != nil && network.Is6(*conf.Gateway) {
-		ndpspoofer.gwIP = conf.Gateway
-	} else {
-		var gwIP netip.Addr
-		if ndpspoofer.iface.Name != iface.Name {
-			gwIP, err = network.GetGatewayIPv6FromInterface(ndpspoofer.iface.Name)
-			if err != nil {
-				return nil, fmt.Errorf("failed fetching gateway ip: %w", err)
-			}
-		} else {
-			gwIP, err = network.GetDefaultGatewayIPv6()
-			if err != nil {
-				gwIP, err = network.GetDefaultGatewayIPv6FromRoute()
-				if err != nil {
-					return nil, fmt.Errorf("failed fetching gateway ip: %w", err)
-				}
-			}
-		}
-		ndpspoofer.gwIP = &gwIP
-	}
 	if conf.RA {
 		ndpspoofer.raEnabled = true
 		if conf.Prefix != nil {
@@ -418,6 +396,16 @@ func NewNDPSpoofer(conf *NDPSpoofConfig) (*NDPSpoofer, error) {
 		}
 	}
 	if conf.NA {
+		if conf.Gateway != nil && network.Is6(*conf.Gateway) {
+			ndpspoofer.gwIP = conf.Gateway
+		} else {
+			var gwIP netip.Addr
+			gwIP, err = network.GetGatewayIPv6FromInterface(ndpspoofer.iface.Name)
+			if err != nil {
+				return nil, fmt.Errorf("failed fetching gateway ip: %w", err)
+			}
+			ndpspoofer.gwIP = &gwIP
+		}
 		ndpspoofer.naEnabled = true
 		ndpspoofer.neighCache = &NeighCache{Ifname: ndpspoofer.iface.Name, Entries: make(map[string]net.HardwareAddr)}
 		err = ndpspoofer.neighCache.Refresh()

resources/RA_test.png

@@ -1,3 +1,3 @@
 package ndpspoof
 
-const Version string = "nf v0.0.4"
+const Version string = "nf v0.0.5"