traefik/vendor/github.com/xenolf/lego/challenge/dns01/precheck.go

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2019-01-07 17:30:06 +00:00
package dns01
import (
"fmt"
"net"
"strings"
"github.com/miekg/dns"
)
// PreCheckFunc checks DNS propagation before notifying ACME that the DNS challenge is ready.
type PreCheckFunc func(fqdn, value string) (bool, error)
func AddPreCheck(preCheck PreCheckFunc) ChallengeOption {
// Prevent race condition
check := preCheck
return func(chlg *Challenge) error {
chlg.preCheck.checkFunc = check
return nil
}
}
func DisableCompletePropagationRequirement() ChallengeOption {
return func(chlg *Challenge) error {
chlg.preCheck.requireCompletePropagation = false
return nil
}
}
type preCheck struct {
// checks DNS propagation before notifying ACME that the DNS challenge is ready.
checkFunc PreCheckFunc
// require the TXT record to be propagated to all authoritative name servers
requireCompletePropagation bool
}
func newPreCheck() preCheck {
return preCheck{
requireCompletePropagation: true,
}
}
func (p preCheck) call(fqdn, value string) (bool, error) {
if p.checkFunc == nil {
return p.checkDNSPropagation(fqdn, value)
}
return p.checkFunc(fqdn, value)
}
// checkDNSPropagation checks if the expected TXT record has been propagated to all authoritative nameservers.
func (p preCheck) checkDNSPropagation(fqdn, value string) (bool, error) {
// Initial attempt to resolve at the recursive NS
r, err := dnsQuery(fqdn, dns.TypeTXT, recursiveNameservers, true)
if err != nil {
return false, err
}
if !p.requireCompletePropagation {
return true, nil
}
if r.Rcode == dns.RcodeSuccess {
// If we see a CNAME here then use the alias
for _, rr := range r.Answer {
if cn, ok := rr.(*dns.CNAME); ok {
if cn.Hdr.Name == fqdn {
fqdn = cn.Target
break
}
}
}
}
authoritativeNss, err := lookupNameservers(fqdn)
if err != nil {
return false, err
}
return checkAuthoritativeNss(fqdn, value, authoritativeNss)
}
// checkAuthoritativeNss queries each of the given nameservers for the expected TXT record.
func checkAuthoritativeNss(fqdn, value string, nameservers []string) (bool, error) {
for _, ns := range nameservers {
r, err := dnsQuery(fqdn, dns.TypeTXT, []string{net.JoinHostPort(ns, "53")}, false)
if err != nil {
return false, err
}
if r.Rcode != dns.RcodeSuccess {
return false, fmt.Errorf("NS %s returned %s for %s", ns, dns.RcodeToString[r.Rcode], fqdn)
}
var records []string
var found bool
for _, rr := range r.Answer {
if txt, ok := rr.(*dns.TXT); ok {
record := strings.Join(txt.Txt, "")
records = append(records, record)
if record == value {
found = true
break
}
}
}
if !found {
return false, fmt.Errorf("NS %s did not return the expected TXT record [fqdn: %s, value: %s]: %s", ns, fqdn, value, strings.Join(records, " ,"))
}
}
return true, nil
}