pim/dyndns-go
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Pim van Pelt
2017-12-22 16:42:32 +01:00
commit 530888899a
5 changed files with 420 additions and 0 deletions
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42
README.md Normal file
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# Source
http://mkaczanowski.com/golang-build-dynamic-dns-service-go/
# Compiling
```
go get github.com/miekg/dns/...
go get github.com/boltdb/bolt/...
go build dyndns-server.go
ls -la dyndns-server
```
# Deploying
MACH=dyn.paphosting.net
scp dyndns-server root@$MACH:/usr/local/sbin
scp systemd/dyndns-server.service root@$MACH:/etc/systemd/system/
# Running
ssh root@$MACH
adduser dyndns
mkdir /var/dyndns
chown dyndns /var/dyndns
service dyndns-server start
# Testing
cat << EOL > update.txt
server $MACH 53
debug yes
key key bWFyaWVsbGU=
zone dyn.ipng.nl.
update delete test.dyn.ipng.nl. A
update delete test.dyn.ipng.nl. AAAA
update add test.dyn.ipng.nl. 120 A 192.0.2.1
update add test.dyn.ipng.nl. 120 AAAA 2001:db8::1
show
send
EOL
nsupdate update.txt

322
dyndns-server.go Normal file
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package main
import (
"errors"
"flag"
"github.com/boltdb/bolt"
"github.com/miekg/dns"
"log"
"math"
"net"
"os"
"os/signal"
"strconv"
"strings"
"syscall"
"time"
)
var (
tsig *string
db_path *string
ip *string
port *int
bdb *bolt.DB
logfile *string
pid_file *string
)
const rr_bucket = "rr"
func getKey(domain string, rtype uint16) (r string, e error) {
if n, ok := dns.IsDomainName(domain); ok {
labels := dns.SplitDomainName(domain)
// Reverse domain, starting from top-level domain
// eg. ".com.mkaczanowski.test"
var tmp string
for i := 0; i < int(math.Floor(float64(n/2))); i++ {
tmp = labels[i]
labels[i] = labels[n-1]
labels[n-1] = tmp
}
reverse_domain := strings.Join(labels, ".")
r = strings.Join([]string{reverse_domain, strconv.Itoa(int(rtype))}, "_")
} else {
e = errors.New("Invailid domain: " + domain)
log.Println(e.Error())
}
return r, e
}
func createBucket(bucket string) (err error) {
err = bdb.Update(func(tx *bolt.Tx) error {
_, err := tx.CreateBucketIfNotExists([]byte(bucket))
if err != nil {
e := errors.New("Create bucket: " + bucket)
log.Println(e.Error())
return e
}
return nil
})
return err
}
func deleteRecord(domain string, rtype uint16) (err error) {
key, _ := getKey(domain, rtype)
err = bdb.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(rr_bucket))
err := b.Delete([]byte(key))
if err != nil {
e := errors.New("Delete record failed for domain: " + domain)
log.Println(e.Error())
return e
}
return nil
})
return err
}
func storeRecord(rr dns.RR) (err error) {
key, _ := getKey(rr.Header().Name, rr.Header().Rrtype)
err = bdb.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(rr_bucket))
err := b.Put([]byte(key), []byte(rr.String()))
if err != nil {
e := errors.New("Store record failed: " + rr.String())
log.Println(e.Error())
return e
}
return nil
})
return err
}
func getRecord(domain string, rtype uint16) (rr dns.RR, err error) {
key, _ := getKey(domain, rtype)
var v []byte
err = bdb.View(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(rr_bucket))
v = b.Get([]byte(key))
if string(v) == "" {
e := errors.New("Record not found, key: " + key)
log.Println(e.Error())
return e
}
return nil
})
if err == nil {
rr, err = dns.NewRR(string(v))
}
return rr, err
}
func updateRecord(r dns.RR, q *dns.Question) {
var (
rr dns.RR
name string
rtype uint16
ttl uint32
ip net.IP
)
header := r.Header()
name = header.Name
rtype = header.Rrtype
ttl = header.Ttl
if _, ok := dns.IsDomainName(name); ok {
if header.Class == dns.ClassANY && header.Rdlength == 0 { // Delete record
deleteRecord(name, rtype)
} else { // Add record
rheader := dns.RR_Header{
Name: name,
Rrtype: rtype,
Class: dns.ClassINET,
Ttl: ttl,
}
if a, ok := r.(*dns.A); ok {
rrr, err := getRecord(name, rtype)
if err == nil {
rr = rrr.(*dns.A)
} else {
rr = new(dns.A)
}
ip = a.A
rr.(*dns.A).Hdr = rheader
rr.(*dns.A).A = ip
} else if a, ok := r.(*dns.AAAA); ok {
rrr, err := getRecord(name, rtype)
if err == nil {
rr = rrr.(*dns.AAAA)
} else {
rr = new(dns.AAAA)
}
ip = a.AAAA
rr.(*dns.AAAA).Hdr = rheader
rr.(*dns.AAAA).AAAA = ip
}
storeRecord(rr)
}
}
}
func parseQuery(m *dns.Msg) {
var rr dns.RR
for _, q := range m.Question {
if read_rr, e := getRecord(q.Name, q.Qtype); e == nil {
rr = read_rr.(dns.RR)
if rr.Header().Name == q.Name {
m.Answer = append(m.Answer, rr)
}
}
}
}
func handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
switch r.Opcode {
case dns.OpcodeQuery:
parseQuery(m)
case dns.OpcodeUpdate:
for _, question := range r.Question {
for _, rr := range r.Ns {
updateRecord(rr, &question)
}
}
}
if r.IsTsig() != nil {
if w.TsigStatus() == nil {
m.SetTsig(r.Extra[len(r.Extra)-1].(*dns.TSIG).Hdr.Name,
dns.HmacMD5, 300, time.Now().Unix())
} else {
log.Println("Status", w.TsigStatus().Error())
}
}
w.WriteMsg(m)
}
func serve(name, secret string, ip string, port int) {
server := &dns.Server{Addr: "[" +ip + "]:" + strconv.Itoa(port), Net: "udp"}
if name != "" {
server.TsigSecret = map[string]string{name: secret}
}
err := server.ListenAndServe()
defer server.Shutdown()
if err != nil {
log.Fatalf("Failed to setup the udp server: %sn", err.Error())
}
}
func main() {
var (
name string // tsig keyname
secret string // tsig base64
fh *os.File // logfile handle
)
// Parse flags
logfile = flag.String("logfile", "", "path to log file")
port = flag.Int("port", 53, "server port")
ip = flag.String("ip", "::", "ip to listen on")
tsig = flag.String("tsig", "", "use MD5 hmac tsig: keyname:base64")
db_path = flag.String("db_path", "/var/dyndns/dyndns.db", "location where db will be stored")
pid_file = flag.String("pid", "/var/dyndns/go-dyndns.pid", "pid file location")
flag.Parse()
// Open db
db, err := bolt.Open(*db_path, 0600,
&bolt.Options{Timeout: 10 * time.Second})
if err != nil {
log.Fatal(err)
}
defer db.Close()
bdb = db
// Create dns bucket if doesn't exist
createBucket(rr_bucket)
// Attach request handler func
dns.HandleFunc(".", handleDnsRequest)
// Tsig extract
if *tsig != "" {
a := strings.SplitN(*tsig, ":", 2)
name, secret = dns.Fqdn(a[0]), a[1]
}
// Logger setup
if *logfile != "" {
if _, err := os.Stat(*logfile); os.IsNotExist(err) {
if file, err := os.Create(*logfile); err != nil {
if err != nil {
log.Panic("Couldn't create log file: ", err)
}
fh = file
}
} else {
fh, _ = os.OpenFile(*logfile, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
}
defer fh.Close()
log.SetOutput(fh)
}
// Pidfile
file, err := os.OpenFile(*pid_file, os.O_RDWR|os.O_CREATE, 0666)
if err != nil {
log.Panic("Couldn't create pid file: ", err)
} else {
file.Write([]byte(strconv.Itoa(syscall.Getpid())))
defer file.Close()
}
// Start server
go serve(name, secret, *ip, *port)
sig := make(chan os.Signal)
signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
endless:
for {
select {
case s := <-sig:
log.Printf("Signal (%d) received, stopping", s)
break endless
}
}
}

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systemd/dyndns-server.service Normal file
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[Unit]
Description=DynDNS server in Go
# Documentation=See git@git.ipng.nl:pim/dyndns-go.git
[Service]
User=dyndns
Group=nogroup
ExecStart=/usr/local/sbin/dyndns-server -port=53 -ip=:: -tsig=key:bWFyaWVsbGU=
Restart=always
ProtectSystem=full
ProtectHome=true
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
AmbientCapabilities=CAP_NET_BIND_SERVICE
[Install]
WantedBy=multi-user.target

30
update-dyndns.sh Executable file
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#!/bin/sh
SERVER="dyn.paphosting.net"
PORT="53"
TSIG="bWFyaWVsbGU="
INTERFACE_A="eth0"
INTERFACE_AAAA="eth0"
# Generated variables follow:
UPDATE_FILE="/tmp/go-dyndns-nsupdate.$$"
A_RECORD=$(ip addr show $INTERFACE_A | awk '/inet .*scope global/ { ip=$2; gsub("/.*","", ip); } END { print ip}')
AAAA_RECORD=$(ip addr show $INTERFACE_AAAA | awk '/inet6 .*scope global/ { ip=$2; gsub("/.*","", ip); } END { print ip}')
HOSTNAME_SHORT=$(hostname -s)
cat << EOL > $UPDATE_FILE
server $SERVER $PORT
key key bWFyaWVsbGU=
; debug
zone dyn.ipng.nl.
; update delete ${HOSTNAME_SHORT}.dyn.ipng.nl. A
; update delete ${HOSTNAME_SHORT}.dyn.ipng.nl. AAAA
update add ${HOSTNAME_SHORT}.dyn.ipng.nl. 120 A ${A_RECORD}
update add ${HOSTNAME_SHORT}.dyn.ipng.nl. 120 AAAA ${AAAA_RECORD}
show
send
EOL
nsupdate ${UPDATE_FILE}
rm -f ${UPDATE_FILE}

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update.txt Normal file
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server 194.1.163.24 53
debug yes
key key bWFyaWVsbGU=
zone dyn.ipng.nl.
update delete test.dyn.ipng.nl. A
update delete test.dyn.ipng.nl. AAAA
update add test.dyn.ipng.nl. 120 A 192.0.2.1
update add test.dyn.ipng.nl. 120 AAAA 2001:db8::1
show
send