lego/acme/dns_challenge_rfc2136.go

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package acme
import (
"fmt"
"github.com/miekg/dns"
"time"
)
// DNSProviderRFC2136 is an implementation of the DNSProvider interface that
// uses dynamic DNS updates (RFC 2136) to create TXT records on a nameserver.
type DNSProviderRFC2136 struct {
nameserver string
zone string
tsigKey string
tsigSecret string
}
// NewDNSProviderRFC2136 returns a new DNSProviderRFC2136 instance.
// To disable TSIG authentication 'tsigKey' and 'tsigSecret' must be set to the empty string.
// 'nameserver' must be a network address in the the form "host:port". 'zone' must be the fully
// qualified name of the zone.
func NewDNSProviderRFC2136(nameserver, zone, tsigKey, tsigSecret string) (*DNSProviderRFC2136, error) {
d := &DNSProviderRFC2136{
nameserver: nameserver,
zone: zone,
}
if len(tsigKey) > 0 && len(tsigSecret) > 0 {
d.tsigKey = tsigKey
d.tsigSecret = tsigSecret
}
return d, nil
}
// CreateTXTRecord creates a TXT record using the specified parameters
func (r *DNSProviderRFC2136) CreateTXTRecord(fqdn, value string, ttl int) error {
return r.changeRecord("INSERT", fqdn, value, ttl)
}
// RemoveTXTRecord removes the TXT record matching the specified parameters
func (r *DNSProviderRFC2136) RemoveTXTRecord(fqdn, value string, ttl int) error {
return r.changeRecord("REMOVE", fqdn, value, ttl)
}
func (r *DNSProviderRFC2136) changeRecord(action, fqdn, value string, ttl int) error {
// Create RR
rr := new(dns.TXT)
rr.Hdr = dns.RR_Header{Name: fqdn, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: uint32(ttl)}
rr.Txt = []string{value}
rrs := make([]dns.RR, 1)
rrs[0] = rr
// Create dynamic update packet
m := new(dns.Msg)
m.SetUpdate(dns.Fqdn(r.zone))
switch action {
case "INSERT":
m.Insert(rrs)
case "REMOVE":
m.Remove(rrs)
default:
return fmt.Errorf("Unexpected action: %s", action)
}
// Setup client
c := new(dns.Client)
c.SingleInflight = true
// TSIG authentication / msg signing
if len(r.tsigKey) > 0 && len(r.tsigSecret) > 0 {
m.SetTsig(dns.Fqdn(r.tsigKey), dns.HmacMD5, 300, time.Now().Unix())
c.TsigSecret = map[string]string{dns.Fqdn(r.tsigKey): r.tsigSecret}
}
// Send the query
reply, _, err := c.Exchange(m, r.nameserver)
if err != nil {
return fmt.Errorf("DNS update failed: %v", err)
}
if reply != nil && reply.Rcode != dns.RcodeSuccess {
return fmt.Errorf("DNS update failed. Server replied: %s", dns.RcodeToString[reply.Rcode])
}
return nil
}