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This is a much faster and better implementation of a pure go scanner. It uses gopacket to perform arp scanning to find devices on the network along with their mac addresses. It then performs a SYN scan on those found devices to detect when port 22 is open. Caveats are that this requires ops to be run with root privileges and has a dependency on libpcap.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,275 @@ | ||
| package discovery | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "context" | ||
| "net" | ||
| "regexp" | ||
|
|
||
| "github.com/google/gopacket" | ||
| "github.com/google/gopacket/layers" | ||
| "github.com/google/gopacket/pcap" | ||
| "github.com/projectdiscovery/mapcidr" | ||
| "github.com/robgonnella/ops/internal/logger" | ||
| "github.com/robgonnella/ops/internal/server" | ||
| "github.com/robgonnella/ops/internal/util" | ||
| "github.com/rs/zerolog/log" | ||
| ) | ||
|
|
||
| var cidrSuffix = regexp.MustCompile(`\/\d{2}$`) | ||
|
|
||
| type ARPScanner struct { | ||
| ctx context.Context | ||
| cancel context.CancelFunc | ||
| targets []string | ||
| networkInfo *util.NetworkInfo | ||
| handle *pcap.Handle | ||
| packetSource *gopacket.PacketSource | ||
| arpMap map[string]net.HardwareAddr | ||
| resultChan chan *DiscoveryResult | ||
| log logger.Logger | ||
| } | ||
|
|
||
| func NewARPScanner( | ||
| networkInfo *util.NetworkInfo, | ||
| targets []string, | ||
| resultChan chan *DiscoveryResult, | ||
| ) (*ARPScanner, error) { | ||
| ipList := []string{} | ||
|
|
||
| for _, t := range targets { | ||
| if cidrSuffix.MatchString(t) { | ||
| ips, err := mapcidr.IPAddresses(t) | ||
|
|
||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| ipList = append(ipList, ips...) | ||
| } else { | ||
| ipList = append(ipList, t) | ||
| } | ||
| } | ||
|
|
||
| // Open up a pcap handle for packet reads/writes. | ||
| handle, err := pcap.OpenLive( | ||
| networkInfo.Interface.Name, | ||
| 65536, | ||
| true, | ||
| pcap.BlockForever, | ||
| ) | ||
|
|
||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| src := gopacket.NewPacketSource(handle, layers.LayerTypeEthernet) | ||
|
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| ctx, cancel := context.WithCancel(context.Background()) | ||
|
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| scanner := &ARPScanner{ | ||
| ctx: ctx, | ||
| cancel: cancel, | ||
| targets: ipList, | ||
| handle: handle, | ||
| packetSource: src, | ||
| networkInfo: networkInfo, | ||
| arpMap: map[string]net.HardwareAddr{}, | ||
| resultChan: resultChan, | ||
| log: logger.New(), | ||
| } | ||
|
|
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| go scanner.readPackets() | ||
|
|
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| return scanner, nil | ||
| } | ||
|
|
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| func (s *ARPScanner) Scan() error { | ||
| return s.writeARP() | ||
| } | ||
|
|
||
| func (s *ARPScanner) Stop() { | ||
| s.cancel() | ||
| s.handle.Close() | ||
| } | ||
|
|
||
| func (s *ARPScanner) readPackets() { | ||
| for { | ||
| select { | ||
| case <-s.ctx.Done(): | ||
| return | ||
| case packet := <-s.packetSource.Packets(): | ||
| arpLayer := packet.Layer(layers.LayerTypeARP) | ||
|
|
||
| if arpLayer != nil { | ||
| s.handleARPLayer(arpLayer.(*layers.ARP)) | ||
| continue | ||
| } | ||
|
|
||
| s.handleNonARPPacket(packet) | ||
| } | ||
| } | ||
| } | ||
|
|
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| func (s *ARPScanner) handleARPLayer(arp *layers.ARP) { | ||
| if arp.Operation != layers.ARPReply { | ||
| // not an arp reply | ||
| return | ||
| } | ||
|
|
||
| if bytes.Equal([]byte(s.networkInfo.Interface.HardwareAddr), arp.SourceHwAddress) { | ||
| // This is a packet I sent. | ||
| return | ||
| } | ||
|
|
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| ip := net.IP(arp.SourceProtAddress) | ||
| mac := net.HardwareAddr(arp.SourceHwAddress) | ||
|
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| s.arpMap[ip.String()] = mac | ||
|
|
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| s.writeSyn(ip, mac) | ||
| } | ||
|
|
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| func (s *ARPScanner) handleNonARPPacket(packet gopacket.Packet) { | ||
| // Find the packets we care about, and print out logging | ||
| // information about them. All others are ignored. | ||
| net := packet.NetworkLayer() | ||
|
|
||
| if net == nil { | ||
| return | ||
| } | ||
|
|
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| srcIP := net.NetworkFlow().Src().String() | ||
|
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| mac, ok := s.arpMap[srcIP] | ||
|
|
||
| if !ok { | ||
| return | ||
| } | ||
|
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| tcpLayer := packet.Layer(layers.LayerTypeTCP) | ||
|
|
||
| if tcpLayer == nil { | ||
| return | ||
| } | ||
|
|
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| tcp, ok := tcpLayer.(*layers.TCP) | ||
|
|
||
| if !ok { | ||
| // this should never happen. | ||
| return | ||
| } | ||
|
|
||
| if tcp.DstPort != 54321 { | ||
| return | ||
| } | ||
|
|
||
| if tcp.SrcPort != 22 { | ||
| return | ||
| } | ||
|
|
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| res := &DiscoveryResult{ | ||
| ID: mac.String(), | ||
| IP: srcIP, | ||
| Hostname: "", | ||
| OS: "", | ||
| Status: server.StatusOnline, | ||
| } | ||
|
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| port := Port{ | ||
| ID: 22, | ||
| Status: PortClosed, | ||
| } | ||
|
|
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| if tcp.SYN && tcp.ACK { | ||
| port.Status = PortOpen | ||
| } | ||
|
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| res.Ports = []Port{port} | ||
|
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| s.resultChan <- res | ||
| } | ||
|
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| func (s *ARPScanner) writeARP() error { | ||
| // Set up all the layers' fields we can. | ||
| eth := layers.Ethernet{ | ||
| SrcMAC: s.networkInfo.Interface.HardwareAddr, | ||
| DstMAC: net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, | ||
| EthernetType: layers.EthernetTypeARP, | ||
| } | ||
|
|
||
| arp := layers.ARP{ | ||
| AddrType: layers.LinkTypeEthernet, | ||
| Protocol: layers.EthernetTypeIPv4, | ||
| HwAddressSize: 6, | ||
| ProtAddressSize: 4, | ||
| Operation: layers.ARPRequest, | ||
| SourceHwAddress: []byte(s.networkInfo.Interface.HardwareAddr), | ||
| SourceProtAddress: []byte(s.networkInfo.UserIP.To4()), | ||
| DstHwAddress: []byte{0, 0, 0, 0, 0, 0}, | ||
| } | ||
|
|
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| // Set up buffer and options for serialization. | ||
| buf := gopacket.NewSerializeBuffer() | ||
|
|
||
| opts := gopacket.SerializeOptions{ | ||
| FixLengths: true, | ||
| ComputeChecksums: true, | ||
| } | ||
|
|
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| // Send one packet for every address. | ||
| for _, ip := range s.targets { | ||
| arp.DstProtAddress = []byte(net.ParseIP(ip).To4()) | ||
|
|
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| if err := gopacket.SerializeLayers(buf, opts, ð, &arp); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| if err := s.handle.WritePacketData(buf.Bytes()); err != nil { | ||
| log.Error().Err(err).Msg("") | ||
| } | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func (s *ARPScanner) writeSyn(ip net.IP, mac net.HardwareAddr) { | ||
| // Construct all the network layers we need. | ||
| eth := layers.Ethernet{ | ||
| SrcMAC: s.networkInfo.Interface.HardwareAddr, | ||
| DstMAC: mac, | ||
| EthernetType: layers.EthernetTypeIPv4, | ||
| } | ||
|
|
||
| ip4 := layers.IPv4{ | ||
| SrcIP: s.networkInfo.UserIP.To4(), | ||
| DstIP: ip.To4(), | ||
| Version: 4, | ||
| TTL: 64, | ||
| Protocol: layers.IPProtocolTCP, | ||
| } | ||
|
|
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| tcp := layers.TCP{ | ||
| SrcPort: 54321, | ||
| DstPort: 22, | ||
| SYN: true, | ||
| } | ||
|
|
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| tcp.SetNetworkLayerForChecksum(&ip4) | ||
|
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| buf := gopacket.NewSerializeBuffer() | ||
|
|
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| opts := gopacket.SerializeOptions{ | ||
| FixLengths: true, | ||
| ComputeChecksums: true, | ||
| } | ||
|
|
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| if err := gopacket.SerializeLayers(buf, opts, ð, &ip4, &tcp); err != nil { | ||
| s.log.Error().Err(err).Msg("failed to serialize syn layers") | ||
| return | ||
| } | ||
|
|
||
| if err := s.handle.WritePacketData(buf.Bytes()); err != nil { | ||
| s.log.Error().Err(err).Msg("failed to send syn packet") | ||
| } | ||
| } |
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