139 lines
3.0 KiB
Go
139 lines
3.0 KiB
Go
/*
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* A name server which sends back the IP address of its client, the
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* recursive resolver. When queried for type TXT, it sends back the text
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* form of the address. When queried for type A (resp. AAAA), it sends
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* back the IPv4 (resp. v6) address.
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*
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* Similar services: whoami.ultradns.net, whoami.akamai.net. Also (but it
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* is not their normal goal): rs.dns-oarc.net, porttest.dns-oarc.net,
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* amiopen.openresolvers.org.
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*
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* Original version from:
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* Stephane Bortzmeyer <stephane+grong@bortzmeyer.org>
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*
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* Adapted to Go DNS (i.e. completely rewritten)
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* Miek Gieben <miek@miek.nl>
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*/
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package main
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import (
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"dns"
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"flag"
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"fmt"
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"log"
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"net"
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"os"
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"os/signal"
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"runtime/pprof"
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"strconv"
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)
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var (
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printf *bool
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compress *bool
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)
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const dom = "whoami.miek.nl."
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func handleReflect(w dns.ResponseWriter, r *dns.Msg) {
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var (
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v4 bool
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rr dns.RR
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str string
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a net.IP
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)
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// TC must be done here
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m := new(dns.Msg)
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m.SetReply(r)
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m.Compress = *compress
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if ip, ok := w.RemoteAddr().(*net.UDPAddr); ok {
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str = "Port: " + strconv.Itoa(ip.Port) + " (udp)"
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a = ip.IP
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v4 = a.To4() != nil
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}
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if ip, ok := w.RemoteAddr().(*net.TCPAddr); ok {
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str = "Port: " + strconv.Itoa(ip.Port) + " (tcp)"
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a = ip.IP
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v4 = a.To4() != nil
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}
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if v4 {
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rr = new(dns.RR_A)
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rr.(*dns.RR_A).Hdr = dns.RR_Header{Name: dom, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
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rr.(*dns.RR_A).A = a.To4()
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} else {
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rr = new(dns.RR_AAAA)
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rr.(*dns.RR_AAAA).Hdr = dns.RR_Header{Name: dom, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 0}
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rr.(*dns.RR_AAAA).AAAA = a
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}
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t := new(dns.RR_TXT)
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t.Hdr = dns.RR_Header{Name: dom, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}
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t.Txt = []string{str}
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switch r.Question[0].Qtype {
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case dns.TypeTXT:
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m.Answer = append(m.Answer, t)
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m.Extra = append(m.Extra, rr)
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default:
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fallthrough
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case dns.TypeAAAA, dns.TypeA:
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m.Answer = append(m.Answer, rr)
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m.Extra = append(m.Extra, t)
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}
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b, ok := m.Pack()
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if *printf {
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fmt.Printf("%v\n", m.String())
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}
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if !ok {
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log.Print("Packing failed")
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m.SetRcode(r, dns.RcodeServerFailure)
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m.Extra = nil
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m.Answer = nil
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b, _ = m.Pack()
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}
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// The reply is smaller then 512 bytes, so it will always "fit"
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w.Write(b)
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}
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func serve(net string) {
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err := dns.ListenAndServe(":8053", net, nil)
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if err != nil {
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fmt.Printf("Failed to setup the "+net+" server: %s\n", err.Error())
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}
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}
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func main() {
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cpuprofile := flag.String("cpuprofile", "", "write cpu profile to file")
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printf = flag.Bool("print", false, "print replies")
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compress = flag.Bool("compress", false, "compress replies")
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flag.Usage = func() {
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flag.PrintDefaults()
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}
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flag.Parse()
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if *cpuprofile != "" {
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f, err := os.Create(*cpuprofile)
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if err != nil {
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log.Fatal(err)
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}
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pprof.StartCPUProfile(f)
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defer pprof.StopCPUProfile()
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}
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dns.HandleFunc(".", handleReflect)
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go serve("tcp")
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go serve("udp")
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sig := make(chan os.Signal)
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signal.Notify(sig)
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forever:
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for {
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select {
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case <-sig:
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fmt.Printf("Signal received, stopping\n")
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break forever
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}
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}
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}
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