129 lines
3.9 KiB
Go
129 lines
3.9 KiB
Go
// Package rfc2136 implements a DNS provider for solving the DNS-01 challenge
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// using the rfc2136 dynamic update.
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package rfc2136
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import (
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"fmt"
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"net"
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"os"
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"strings"
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"time"
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"github.com/miekg/dns"
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"github.com/xenolf/lego/acme"
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)
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// DNSProvider is an implementation of the acme.ChallengeProvider interface that
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// uses dynamic DNS updates (RFC 2136) to create TXT records on a nameserver.
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type DNSProvider struct {
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nameserver string
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tsigAlgorithm string
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tsigKey string
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tsigSecret string
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}
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// NewDNSProvider returns a DNSProvider instance configured for rfc2136
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// dynamic update. Credentials must be passed in the environment variables:
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// RFC2136_NAMESERVER, RFC2136_TSIG_ALGORITHM, RFC2136_TSIG_KEY and
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// RFC2136_TSIG_SECRET. To disable TSIG authentication, leave the TSIG
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// variables unset. RFC2136_NAMESERVER must be a network address in the form
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// "host" or "host:port".
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func NewDNSProvider() (*DNSProvider, error) {
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nameserver := os.Getenv("RFC2136_NAMESERVER")
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tsigAlgorithm := os.Getenv("RFC2136_TSIG_ALGORITHM")
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tsigKey := os.Getenv("RFC2136_TSIG_KEY")
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tsigSecret := os.Getenv("RFC2136_TSIG_SECRET")
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return NewDNSProviderCredentials(nameserver, tsigAlgorithm, tsigKey, tsigSecret)
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}
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// NewDNSProviderCredentials uses the supplied credentials to return a
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// DNSProvider instance configured for rfc2136 dynamic update. To disable TSIG
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// authentication, leave the TSIG parameters as empty strings.
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// nameserver must be a network address in the form "host" or "host:port".
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func NewDNSProviderCredentials(nameserver, tsigAlgorithm, tsigKey, tsigSecret string) (*DNSProvider, error) {
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if nameserver == "" {
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return nil, fmt.Errorf("RFC2136 nameserver missing")
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}
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// Append the default DNS port if none is specified.
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if _, _, err := net.SplitHostPort(nameserver); err != nil {
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if strings.Contains(err.Error(), "missing port") {
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nameserver = net.JoinHostPort(nameserver, "53")
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} else {
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return nil, err
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}
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}
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d := &DNSProvider{
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nameserver: nameserver,
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}
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if tsigAlgorithm == "" {
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tsigAlgorithm = dns.HmacMD5
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}
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d.tsigAlgorithm = tsigAlgorithm
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if len(tsigKey) > 0 && len(tsigSecret) > 0 {
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d.tsigKey = tsigKey
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d.tsigSecret = tsigSecret
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}
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return d, nil
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}
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// Present creates a TXT record using the specified parameters
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func (r *DNSProvider) Present(domain, token, keyAuth string) error {
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fqdn, value, ttl := acme.DNS01Record(domain, keyAuth)
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return r.changeRecord("INSERT", fqdn, value, ttl)
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}
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// CleanUp removes the TXT record matching the specified parameters
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func (r *DNSProvider) CleanUp(domain, token, keyAuth string) error {
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fqdn, value, ttl := acme.DNS01Record(domain, keyAuth)
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return r.changeRecord("REMOVE", fqdn, value, ttl)
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}
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func (r *DNSProvider) changeRecord(action, fqdn, value string, ttl int) error {
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// Find the zone for the given fqdn
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zone, err := acme.FindZoneByFqdn(fqdn, []string{r.nameserver})
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if err != nil {
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return err
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}
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// Create RR
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rr := new(dns.TXT)
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rr.Hdr = dns.RR_Header{Name: fqdn, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: uint32(ttl)}
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rr.Txt = []string{value}
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rrs := []dns.RR{rr}
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// Create dynamic update packet
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m := new(dns.Msg)
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m.SetUpdate(zone)
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switch action {
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case "INSERT":
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// Always remove old challenge left over from who knows what.
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m.RemoveRRset(rrs)
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m.Insert(rrs)
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case "REMOVE":
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m.Remove(rrs)
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default:
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return fmt.Errorf("Unexpected action: %s", action)
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}
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// Setup client
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c := new(dns.Client)
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c.SingleInflight = true
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// TSIG authentication / msg signing
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if len(r.tsigKey) > 0 && len(r.tsigSecret) > 0 {
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m.SetTsig(dns.Fqdn(r.tsigKey), r.tsigAlgorithm, 300, time.Now().Unix())
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c.TsigSecret = map[string]string{dns.Fqdn(r.tsigKey): r.tsigSecret}
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}
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// Send the query
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reply, _, err := c.Exchange(m, r.nameserver)
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if err != nil {
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return fmt.Errorf("DNS update failed: %v", err)
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}
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if reply != nil && reply.Rcode != dns.RcodeSuccess {
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return fmt.Errorf("DNS update failed. Server replied: %s", dns.RcodeToString[reply.Rcode])
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}
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return nil
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}
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