lego/acme/dns_challenge.go
LukeHandle 20ab8300eb Use zone name when talking to DNS APIs
This should handle multiple zones more efficiently
2016-03-21 00:18:49 +00:00

266 lines
7.3 KiB
Go

package acme
import (
"crypto/sha256"
"encoding/base64"
"errors"
"fmt"
"log"
"net"
"strings"
"time"
"github.com/miekg/dns"
"golang.org/x/net/publicsuffix"
)
type preCheckDNSFunc func(fqdn, value string) (bool, error)
var (
preCheckDNS preCheckDNSFunc = checkDNSPropagation
fqdnToZone = map[string]string{}
)
var RecursiveNameserver = "google-public-dns-a.google.com:53"
// DNS01Record returns a DNS record which will fulfill the `dns-01` challenge
func DNS01Record(domain, keyAuth string) (fqdn string, value string, ttl int) {
keyAuthShaBytes := sha256.Sum256([]byte(keyAuth))
// base64URL encoding without padding
keyAuthSha := base64.URLEncoding.EncodeToString(keyAuthShaBytes[:sha256.Size])
value = strings.TrimRight(keyAuthSha, "=")
ttl = 120
fqdn = fmt.Sprintf("_acme-challenge.%s.", domain)
return
}
// dnsChallenge implements the dns-01 challenge according to ACME 7.5
type dnsChallenge struct {
jws *jws
validate validateFunc
provider ChallengeProvider
}
func (s *dnsChallenge) Solve(chlng challenge, domain string) error {
logf("[INFO][%s] acme: Trying to solve DNS-01", domain)
if s.provider == nil {
return errors.New("No DNS Provider configured")
}
// Generate the Key Authorization for the challenge
keyAuth, err := getKeyAuthorization(chlng.Token, s.jws.privKey)
if err != nil {
return err
}
err = s.provider.Present(domain, chlng.Token, keyAuth)
if err != nil {
return fmt.Errorf("Error presenting token %s", err)
}
defer func() {
err := s.provider.CleanUp(domain, chlng.Token, keyAuth)
if err != nil {
log.Printf("Error cleaning up %s %v ", domain, err)
}
}()
fqdn, value, _ := DNS01Record(domain, keyAuth)
logf("[INFO][%s] Checking DNS record propagation...", domain)
var timeout, interval time.Duration
switch provider := s.provider.(type) {
case ChallengeProviderTimeout:
timeout, interval = provider.Timeout()
default:
timeout, interval = 60*time.Second, 2*time.Second
}
err = WaitFor(timeout, interval, func() (bool, error) {
return preCheckDNS(fqdn, value)
})
if err != nil {
return err
}
return s.validate(s.jws, domain, chlng.URI, challenge{Resource: "challenge", Type: chlng.Type, Token: chlng.Token, KeyAuthorization: keyAuth})
}
// checkDNSPropagation checks if the expected TXT record has been propagated to all authoritative nameservers.
func checkDNSPropagation(fqdn, value string) (bool, error) {
// Initial attempt to resolve at the recursive NS
r, err := dnsQuery(fqdn, dns.TypeTXT, RecursiveNameserver, true)
if err != nil {
return false, err
}
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, 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 found bool
for _, rr := range r.Answer {
if txt, ok := rr.(*dns.TXT); ok {
if strings.Join(txt.Txt, "") == value {
found = true
break
}
}
}
if !found {
return false, fmt.Errorf("NS %s did not return the expected TXT record", ns)
}
}
return true, nil
}
// dnsQuery sends a DNS query to the given nameserver.
// The nameserver should include a port, to facilitate testing where we talk to a mock dns server.
func dnsQuery(fqdn string, rtype uint16, nameserver string, recursive bool) (in *dns.Msg, err error) {
m := new(dns.Msg)
m.SetQuestion(fqdn, rtype)
m.SetEdns0(4096, false)
if !recursive {
m.RecursionDesired = false
}
in, err = dns.Exchange(m, nameserver)
if err == dns.ErrTruncated {
tcp := &dns.Client{Net: "tcp"}
in, _, err = tcp.Exchange(m, nameserver)
}
return
}
// lookupNameservers returns the authoritative nameservers for the given fqdn.
func lookupNameservers(fqdn string) ([]string, error) {
var authoritativeNss []string
zone, err := FindZoneByFqdn(fqdn, RecursiveNameserver)
if err != nil {
return nil, err
}
r, err := dnsQuery(zone, dns.TypeNS, RecursiveNameserver, true)
if err != nil {
return nil, err
}
for _, rr := range r.Answer {
if ns, ok := rr.(*dns.NS); ok {
authoritativeNss = append(authoritativeNss, strings.ToLower(ns.Ns))
}
}
if len(authoritativeNss) > 0 {
return authoritativeNss, nil
}
return nil, fmt.Errorf("Could not determine authoritative nameservers")
}
// FindZoneByFqdn determines the zone of the given fqdn
func FindZoneByFqdn(fqdn, nameserver string) (string, error) {
// Do we have it cached?
if zone, ok := fqdnToZone[fqdn]; ok {
return zone, nil
}
// Query the authoritative nameserver for a hopefully non-existing SOA record,
// in the authority section of the reply it will have the SOA of the
// containing zone. rfc2308 has this to say on the subject:
// Name servers authoritative for a zone MUST include the SOA record of
// the zone in the authority section of the response when reporting an
// NXDOMAIN or indicating that no data (NODATA) of the requested type exists
in, err := dnsQuery(fqdn, dns.TypeSOA, nameserver, true)
if err != nil {
return "", err
}
if in.Rcode != dns.RcodeNameError {
if in.Rcode != dns.RcodeSuccess {
return "", fmt.Errorf("NS %s returned %s for %s", nameserver, dns.RcodeToString[in.Rcode], fqdn)
}
// We have a success, so one of the answers has to be a SOA RR
for _, ans := range in.Answer {
if soa, ok := ans.(*dns.SOA); ok {
zone := soa.Hdr.Name
// If we ended up on one of the TLDs, it means the domain did not exist.
publicsuffix, _ := publicsuffix.PublicSuffix(UnFqdn(zone))
if publicsuffix == UnFqdn(zone) {
return "", fmt.Errorf("Could not determine zone authoritatively")
}
fqdnToZone[fqdn] = zone
return zone, nil
}
}
// Or it is NODATA, fall through to NXDOMAIN
}
// Search the authority section for our precious SOA RR
for _, ns := range in.Ns {
if soa, ok := ns.(*dns.SOA); ok {
zone := soa.Hdr.Name
// If we ended up on one of the TLDs, it means the domain did not exist.
publicsuffix, _ := publicsuffix.PublicSuffix(UnFqdn(zone))
if publicsuffix == UnFqdn(zone) {
return "", fmt.Errorf("Could not determine zone authoritatively")
}
fqdnToZone[fqdn] = zone
return zone, nil
}
}
return "", fmt.Errorf("NS %s did not return the expected SOA record in the authority section", nameserver)
}
// ClearFqdnCache clears the cache of fqdn to zone mappings. Primarily used in testing.
func ClearFqdnCache() {
fqdnToZone = map[string]string{}
}
// ToFqdn converts the name into a fqdn appending a trailing dot.
func ToFqdn(name string) string {
n := len(name)
if n == 0 || name[n-1] == '.' {
return name
}
return name + "."
}
// UnFqdn converts the fqdn into a name removing the trailing dot.
func UnFqdn(name string) string {
n := len(name)
if n != 0 && name[n-1] == '.' {
return name[:n-1]
}
return name
}