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