Dirty version, only for remote access

proxy/layer-nbns/layer-nbns.go

@@ -0,0 +1,246 @@
+// based on https://github.com/aler9/landiscover/blob/main/layer-nbns.go (MIT License)
+
+package layer_nbns
+
+import (
+	"encoding/binary"
+	"fmt"
+	"strings"
+
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+)
+
+type layerNbns struct {
+	layers.BaseLayer
+	TransactionID   uint16
+	IsResponse      bool
+	Opcode          uint8
+	Truncated       bool
+	Recursion       bool
+	Broadcast       bool
+	Questions       []nbnsQuestion
+	Answers         []nbnsAnswer
+	AuthorityCount  uint16
+	AdditionalCount uint16
+}
+
+func NewLayerNbns() *layerNbns {
+	return &layerNbns{}
+}
+
+type nbnsQuestion struct {
+	Query string
+	Type  uint16
+	Class uint16
+}
+
+type nbnsAnswer struct {
+	Query string
+	Type  uint16
+	Class uint16
+	TTL   uint32
+	Names []nbnsAnswerName
+}
+
+type nbnsAnswerName struct {
+	Name  string
+	Type  uint8
+	Flags uint16
+}
+
+func (l *layerNbns) DecodeFromBytes(data []byte) error {
+	l.BaseLayer = layers.BaseLayer{Contents: data}
+
+	if len(data) < 12 {
+		return fmt.Errorf("invalid packet")
+	}
+
+	l.TransactionID = binary.BigEndian.Uint16(data[0:2])
+	l.IsResponse = (data[3] >> 7) == 0x01
+	l.Opcode = (data[3] >> 3) & 0x0F
+	l.Truncated = (data[3] >> 1) == 0x01
+	l.Recursion = data[3] == 0x01
+	l.Broadcast = (data[4] >> 4) == 0x01
+	questionCount := binary.BigEndian.Uint16(data[4:6])
+	answerCount := binary.BigEndian.Uint16(data[6:8])
+	l.AuthorityCount = binary.BigEndian.Uint16(data[8:10])
+	l.AdditionalCount = binary.BigEndian.Uint16(data[10:12])
+	pos := 12
+
+	if questionCount > 0 {
+		return fmt.Errorf("is question, unsupported")
+	}
+
+	l.Questions = nil
+	for i := uint16(0); i < questionCount; i++ {
+		q := nbnsQuestion{}
+
+		var read int
+		q.Query, read = dnsQueryDecode(data, pos)
+		if read <= 0 {
+			return fmt.Errorf("invalid string")
+		}
+		pos += read
+
+		q.Type = binary.BigEndian.Uint16(data[pos+0 : pos+2])
+		q.Class = binary.BigEndian.Uint16(data[pos+2 : pos+4])
+		pos += 4
+		l.Questions = append(l.Questions, q)
+	}
+
+	l.Answers = nil
+	for i := uint16(0); i < answerCount; i++ {
+		a := nbnsAnswer{}
+
+		var read int
+		a.Query, read = dnsQueryDecode(data, pos)
+		if read <= 0 {
+			return fmt.Errorf("invalid string")
+		}
+		pos += read
+
+		a.Type = binary.BigEndian.Uint16(data[pos+0 : pos+2])
+		a.Class = binary.BigEndian.Uint16(data[pos+2 : pos+4])
+		a.TTL = binary.BigEndian.Uint32(data[pos+4 : pos+8])
+		dataLen := binary.BigEndian.Uint16(data[pos+8 : pos+10])
+		pos += 10
+
+		if a.Type == 0x21 { // NB_STAT
+			pos2 := pos
+			nameCount := data[pos2]
+			pos2++
+
+			for j := uint8(0); j < nameCount; j++ {
+				a.Names = append(a.Names, nbnsAnswerName{
+					Name:  strings.TrimSuffix(string(data[pos2:pos2+15]), " "),
+					Type:  data[pos2+15],
+					Flags: binary.BigEndian.Uint16(data[pos2+16 : pos2+18]),
+				})
+				pos2 += 18
+			}
+		}
+
+		pos += int(dataLen)
+		l.Answers = append(l.Answers, a)
+	}
+
+	// TODO: Decode Authorities and Additional Information
+
+	return nil
+}
+
+func (l *layerNbns) SerializeTo(b gopacket.SerializeBuffer) error {
+	data, err := b.AppendBytes(12)
+	if err != nil {
+		panic(err)
+	}
+
+	binary.BigEndian.PutUint16(data[0:2], l.TransactionID)
+	if l.IsResponse {
+		data[3] |= 0x01 << 7
+	}
+	data[3] |= l.Opcode << 3
+	if l.Truncated {
+		data[3] |= 0x01 << 1
+	}
+	if l.Recursion {
+		data[3] |= 0x01
+	}
+	if l.Broadcast {
+		data[4] |= 0x01 << 4
+	}
+	binary.BigEndian.PutUint16(data[4:6], uint16(len(l.Questions)))
+	binary.BigEndian.PutUint16(data[6:8], uint16(len(l.Answers)))
+	binary.BigEndian.PutUint16(data[8:10], l.AuthorityCount)
+	binary.BigEndian.PutUint16(data[10:12], l.AdditionalCount)
+
+	for _, q := range l.Questions {
+		enc := dnsQueryEncode(q.Query)
+
+		data, err := b.AppendBytes(len(enc) + 4)
+		if err != nil {
+			panic(err)
+		}
+
+		copy(data[:len(enc)], enc)
+		data = data[len(enc):]
+		binary.BigEndian.PutUint16(data[0:2], q.Type)
+		binary.BigEndian.PutUint16(data[2:4], q.Class)
+	}
+
+	// TODO: encode answers, authorities and additional informations
+
+	return nil
+}
+
+// Source: https://github.com/aler9/landiscover/blob/main/utils.go
+// <size>part<size>part
+func dnsQueryDecode(data []byte, start int) (string, int) {
+	var read []byte
+	toread := uint8(0)
+	pos := start
+
+	for ; true; pos++ {
+		if pos >= len(data) { // decoding terminated before null character
+			return "", -1
+		}
+		if data[pos] == 0x00 {
+			if toread > 0 { // decoding terminated before part parsing
+				return "", -1
+			}
+			break // query correctly decoded
+		}
+
+		if toread == 0 { // we need a size or pointer
+			if len(read) > 0 { // add separator
+				read = append(read, '.')
+			}
+
+			if (data[pos] & 0xC0) == 0xC0 { // pointer
+				ptr := int(binary.BigEndian.Uint16(data[pos:pos+2]) & 0x3FFF)
+				pos++ // skip next byte
+
+				substr, subread := dnsQueryDecode(data, ptr)
+				if subread <= 0 {
+					return "", -1
+				}
+				read = append(read, []byte(substr)...)
+				break // query correctly decoded
+			} else { // size
+				toread = data[pos]
+			}
+		} else { // byte inside part
+			read = append(read, data[pos])
+			toread--
+		}
+	}
+	return string(read), pos + 1 - start
+}
+
+func dnsQueryEncode(in string) []byte {
+	tmp := strings.Split(in, ".")
+
+	l := 0
+	for _, part := range tmp {
+		bpart := []byte(part)
+		l++
+		l += len(bpart)
+	}
+	l++
+
+	ret := make([]byte, l)
+	i := 0
+
+	for _, part := range tmp {
+		bpart := []byte(part)
+		ret[i] = uint8(len(bpart))
+		i++
+		copy(ret[i:], bpart)
+		i += len(bpart)
+	}
+
+	ret[i] = uint8(0)
+
+	return ret
+}

proxy/main.go

@@ -12,6 +12,7 @@ import (
 	"net"
 	"os"
 	"proxy/cmd"
+	nbns "proxy/layer-nbns"
 	. "proxy/util"
 	"strconv"
 	"time"
@@ -81,7 +82,7 @@ func main() {
 	c2, VmReader, VmWriter = cmd.Start(*sockProxy)
 	go pipeForward(cmd.In)
 	go pipeForward(cmd.Out)
-	if NewIP == nil {
+	if NewIP == nil && !Passthrough {
 		sendDHCPRequest(dhcp4.Discover, net.IPv4zero)
 	}
 	if *sockMain != "-" {
@@ -121,6 +122,17 @@ func pipeForward(prefix string) {
 			WritePcap("/tmp/pkg_"+strconv.FormatInt(time.Now().Unix(), 10)+".pcap", frameBytes)
 		}
 
+		// Forward original frame to other plug
+		if Passthrough {
+			if _, err := writer.Write(frameLength); err != nil {
+				log.Error("Error forwarding original packet length", err)
+			}
+			if _, err := writer.Write(frameBytes); err != nil {
+				log.Error("Error forwarding original packet data", err)
+			}
+			continue
+		}
+
 		// Convert frame to full stack packet
 		packet := gopacket.NewPacket(frameBytes, layers.LayerTypeEthernet, gopacket.Default)
 
@@ -136,11 +148,9 @@ func pipeForward(prefix string) {
 
 			// Handle DHCPv4 packet (based on IPv4)
 			if dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4); dhcpLayer != nil {
-				if !Passthrough {
 				handleDHCP(dhcpLayer.LayerContents(), frame.DstMAC, frame.SrcMAC, prefix)
 				continue
 			}
-			}
 
 			filterIP(prefix, &ipv4Packet.DstIP, &ipv4Packet.SrcIP, ipv4Packet.LayerType())
 
@@ -164,11 +174,24 @@ func pipeForward(prefix string) {
 				if err := udpPacket.SetNetworkLayerForChecksum(ipv4Packet); err != nil {
 					log.Error(prefix, "Error setting network layer for UDP checksum", err)
 				}
+
+				if udpPacket.SrcPort == 137 && udpPacket.DstPort == 137 {
+					log.Info(prefix, "Trying to decode NBNS payload")
+					l := nbns.NewLayerNbns()
+					if err := l.DecodeFromBytes(udpPacket.Payload); err != nil {
+						log.Warning("Error decoding NBNS: ", err)
+					}
+					print(l)
+				}
+
+				if udpPacket.SrcPort == 138 && udpPacket.DstPort == 138 {
+					log.Info(prefix, "NBDS payload, not implemented (yet)")
+				}
 			}
 		}
 
 		// Drop IPv6 packets
-		if ipv6layer := packet.Layer(layers.LayerTypeIPv6); ipv6layer != nil && !Passthrough {
+		if ipv6layer := packet.Layer(layers.LayerTypeIPv6); ipv6layer != nil {
 			log.Info(prefix, "IPv6 packet dropped")
 			continue
 		}
@@ -183,17 +206,6 @@ func pipeForward(prefix string) {
 
 		log.Debug("End packet")
 
-		// Forward original frame to other plug
-		if Passthrough {
-			if _, err := writer.Write(frameLength); err != nil {
-				log.Error("Error forwarding original packet length", err)
-			}
-			if _, err := writer.Write(frameBytes); err != nil {
-				log.Error("Error forwarding original packet data", err)
-			}
-			continue
-		}
-
 		// Serialize packet back to binary
 		buf := gopacket.NewSerializeBuffer()
 		opts := gopacket.SerializeOptions{ComputeChecksums: true, FixLengths: true}

test-env/envctl

@@ -39,10 +39,10 @@ start)
     $qemu -m 512 -nic vde,mac='52:54:00:12:34:66',sock=$RUN/sw_proxy2.sock -hda alpine2.qcow2 -daemonize -vnc :2 -pidfile $alpine2
     ;;&
   win1 | win | vms | all)
-    $qemu -vga cirrus -smp 1 -net nic,model=rtl8139 -net vde,sock=$RUN/sw_proxy1.sock -soundhw sb16 -m 128 -usb -usbdevice tablet -drive file=images/win98.raw,format=raw,index=0,media=disk  -daemonize -vnc :1 -pidfile $win1
+    $qemu -vga cirrus -smp 1 -net nic,model=rtl8139 -net vde,sock=$RUN/sw_proxy1.sock -soundhw sb16 -m 128 -usb -usbdevice tablet -drive file=images/win98.raw,format=raw,index=0,media=disk -cdrom images/Win98SE.iso -daemonize -vnc :1 -pidfile $win1
     ;;&
   win2 | win | vms | all)
-    $qemu -vga cirrus -smp 1 -net nic,model=rtl8139 -net vde,sock=$RUN/sw_proxy2.sock -soundhw sb16 -m 128 -usb -usbdevice tablet -drive file=images/win98-2.raw,format=raw,index=0,media=disk -daemonize -vnc :2 -pidfile $win2
+    $qemu -vga cirrus -smp 1 -net nic,model=rtl8139,macaddr='52:54:00:12:34:66' -net vde,sock=$RUN/sw_proxy2.sock -soundhw sb16 -m 128 -usb -usbdevice tablet -drive file=images/win98-2.raw,format=raw,index=0,media=disk -cdrom images/Win98SE.iso -daemonize -vnc :2 -pidfile $win2
     ;;&
   kali | vms | all)
     $qemu -m 1024 -nic user -nic vde,mac='52:54:00:12:34:76',sock=$RUN/sw_proxy3.sock -hda kali.qcow2 -daemonize -vnc :3 -pidfile $kali