forked from TrueCloudLab/lego
108 lines
2.5 KiB
Go
108 lines
2.5 KiB
Go
package acme
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import (
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"crypto/sha256"
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"encoding/base64"
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"errors"
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"fmt"
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"log"
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"strings"
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"time"
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"github.com/miekg/dns"
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)
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type preCheckDNSFunc func(domain, fqdn string) bool
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var preCheckDNS preCheckDNSFunc = checkDNS
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var preCheckDNSFallbackCount = 5
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// DNS01Record returns a DNS record which will fulfill the `dns-01` challenge
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func DNS01Record(domain, keyAuth string) (fqdn string, value string, ttl int) {
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keyAuthShaBytes := sha256.Sum256([]byte(keyAuth))
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// base64URL encoding without padding
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keyAuthSha := base64.URLEncoding.EncodeToString(keyAuthShaBytes[:sha256.Size])
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value = strings.TrimRight(keyAuthSha, "=")
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ttl = 120
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fqdn = fmt.Sprintf("_acme-challenge.%s.", domain)
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return
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}
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// dnsChallenge implements the dns-01 challenge according to ACME 7.5
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type dnsChallenge struct {
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jws *jws
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validate validateFunc
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provider ChallengeProvider
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}
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func (s *dnsChallenge) Solve(chlng challenge, domain string) error {
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logf("[INFO] acme: Trying to solve DNS-01")
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if s.provider == nil {
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return errors.New("No DNS Provider configured")
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}
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// Generate the Key Authorization for the challenge
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keyAuth, err := getKeyAuthorization(chlng.Token, &s.jws.privKey.PublicKey)
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if err != nil {
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return err
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}
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err = s.provider.Present(domain, chlng.Token, keyAuth)
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if err != nil {
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return fmt.Errorf("Error presenting token %s", err)
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}
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defer func() {
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err := s.provider.CleanUp(domain, chlng.Token, keyAuth)
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if err != nil {
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log.Printf("Error cleaning up %s %v ", domain, err)
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}
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}()
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fqdn, _, _ := DNS01Record(domain, keyAuth)
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preCheckDNS(domain, fqdn)
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return s.validate(s.jws, domain, chlng.URI, challenge{Resource: "challenge", Type: chlng.Type, Token: chlng.Token, KeyAuthorization: keyAuth})
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}
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func checkDNS(domain, fqdn string) bool {
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// check if the expected DNS entry was created. If not wait for some time and try again.
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m := new(dns.Msg)
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m.SetQuestion(domain+".", dns.TypeSOA)
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c := new(dns.Client)
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in, _, err := c.Exchange(m, "8.8.8.8:53")
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if err != nil {
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return false
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}
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var authorativeNS string
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for _, answ := range in.Answer {
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soa := answ.(*dns.SOA)
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authorativeNS = soa.Ns
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}
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fallbackCnt := 0
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for fallbackCnt < preCheckDNSFallbackCount {
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m.SetQuestion(fqdn, dns.TypeTXT)
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in, _, err = c.Exchange(m, authorativeNS+":53")
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if err != nil {
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return false
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}
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if len(in.Answer) > 0 {
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return true
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}
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fallbackCnt++
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if fallbackCnt >= preCheckDNSFallbackCount {
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return false
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}
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time.Sleep(time.Second * time.Duration(fallbackCnt))
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}
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return false
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}
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