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sniffer.go
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sniffer.go
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package main
import (
"encoding/json"
"flag"
"fmt"
"log"
"os"
"regexp"
"sort"
"strconv"
"strings"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
)
type syslogCapture struct {
Payload string `json:"payload"`
UnixTime int64 `json:"unixTime"`
}
type sysloghost struct {
IPv4Package uint64 `json:"ipv4Package"`
IPv6Package uint64 `json:"ipv6Package"`
UDPDatagrams uint64 `json:"udpDatagrams"`
TCPPackages uint64 `json:"tcpPackages"`
SampleEvent syslogCapture `json:"sampleEvent"`
}
var ipAddrs = make(map[string]sysloghost)
const (
// The same default as tcpdump.
defaultSnapLen = 262144
)
func addPayloadToMap(srcIP string, pkt gopacket.Packet) {
var syslogMsgRegexp = regexp.MustCompile(`.*<\d+>.*$`)
syslogHost := ipAddrs[srcIP]
if syslogHost.SampleEvent.Payload != "" {
// Seen before
return
}
applicationLayer := pkt.ApplicationLayer()
if applicationLayer != nil {
payload := string(applicationLayer.Payload())
//log.Print("Source ip: ", srcIP, " Payload: ", payload)
if syslogMsgRegexp.MatchString(payload) {
newSyslogMsg := syslogCapture{payload, time.Now().Unix()}
syslogHost.SampleEvent = newSyslogMsg
ipAddrs[srcIP] = syslogHost
}
}
}
func analysePacket(pkt gopacket.Packet) {
// Let's see if the packet is IP (even though the ether type told us)
ipLayer := pkt.Layer(layers.LayerTypeIPv4)
scrIP := ""
if ipLayer != nil {
//fmt.Println("IPv4 layer detected.")
ip, _ := ipLayer.(*layers.IPv4)
scrIP = ip.SrcIP.String()
sysloghost := ipAddrs[scrIP]
sysloghost.IPv4Package = sysloghost.IPv4Package + 1
ipAddrs[scrIP] = sysloghost
}
ip6Layer := pkt.Layer(layers.LayerTypeIPv6)
if ip6Layer != nil {
//fmt.Println("IPv6 layer detected.")
ip, _ := ip6Layer.(*layers.IPv6)
scrIP = ip.SrcIP.String()
sysloghost := ipAddrs[scrIP]
sysloghost.IPv6Package = sysloghost.IPv6Package + 1
ipAddrs[scrIP] = sysloghost
}
tcpLayer := pkt.Layer(layers.LayerTypeTCP)
if tcpLayer != nil {
sysloghost := ipAddrs[scrIP]
sysloghost.TCPPackages = sysloghost.TCPPackages + 1
ipAddrs[scrIP] = sysloghost
}
udpLayer := pkt.Layer(layers.LayerTypeUDP)
if udpLayer != nil {
sysloghost := ipAddrs[scrIP]
sysloghost.UDPDatagrams = sysloghost.UDPDatagrams + 1
ipAddrs[scrIP] = sysloghost
}
addPayloadToMap(scrIP, pkt)
}
func sniff(intf string, bpffiler string, duration time.Duration) {
handle, err := pcap.OpenLive(intf, defaultSnapLen, true, 1000)
if err != nil {
panic(err)
}
defer handle.Close()
if err := handle.SetBPFFilter(bpffiler); err != nil {
panic(err)
}
timer := time.NewTicker(duration)
defer timer.Stop()
src := gopacket.NewPacketSource(handle, handle.LinkType())
for {
select {
case pkt := <-src.Packets():
// process a packet in pkt
analysePacket(pkt)
case <-timer.C:
// timed out waiting for 2s seconds
return
}
}
}
func _UnescapeUnicodeCharactersInJSON(_jsonRaw json.RawMessage) (json.RawMessage, error) {
str, err := strconv.Unquote(strings.Replace(strconv.Quote(string(_jsonRaw)), `\\u`, `\u`, -1))
if err != nil {
return nil, err
}
return []byte(str), nil
}
func main() {
interfacePtr := flag.String("i", "eth0", "Interface to listen on")
portPtr := flag.Int("p", 514, "Port to listen for")
secondsPtr := flag.Int64("t", 60, "Number of seconds to listen on interface")
flag.Parse()
bpffiler := "port " + strconv.Itoa(*portPtr)
duration := time.Duration(*secondsPtr * int64(time.Second))
if *interfacePtr == "" {
log.Fatal("Interface flag (-i) needs to be set!")
os.Exit(1)
}
sniff(*interfacePtr, bpffiler, duration)
if len(ipAddrs) == 0 {
return
}
keys := make([]string, 0, len(ipAddrs))
for k := range ipAddrs {
keys = append(keys, k)
}
sort.Strings(keys)
jsonByte, err := json.Marshal(ipAddrs)
if err != nil {
log.Println("Failed with json Mashal", err)
}
jsonRawUnescapedBytes, _ := _UnescapeUnicodeCharactersInJSON(jsonByte)
fmt.Println(string(jsonRawUnescapedBytes))
}