Refactor DNS precheck

acme/dns_challenge.go

@@ -13,11 +13,9 @@ import (
 	"github.com/miekg/dns"
 )
 
-type preCheckDNSFunc func() bool
+type preCheckDNSFunc func(domain, fqdn string) bool
 
-var preCheckDNS = func() bool {
-	return true
-}
+var preCheckDNS preCheckDNSFunc = checkDNS
 
 var preCheckDNSFallbackCount = 5
 
@@ -54,42 +52,7 @@ func (s *dnsChallenge) Solve(chlng challenge, domain string) error {
 		return err
 	}
 
-	if preCheckDNS() {
-		// check if the expected DNS entry was created. If not wait for some time and try again.
-		m := new(dns.Msg)
-		m.SetQuestion(domain+".", dns.TypeSOA)
-		c := new(dns.Client)
-		in, _, err := c.Exchange(m, "8.8.8.8:53")
-		if err != nil {
-			return err
-		}
-
-		var authorativeNS string
-		for _, answ := range in.Answer {
-			soa := answ.(*dns.SOA)
-			authorativeNS = soa.Ns
-		}
-
-		fallbackCnt := 0
-		for fallbackCnt < preCheckDNSFallbackCount {
-			m.SetQuestion(fqdn, dns.TypeTXT)
-			in, _, err = c.Exchange(m, authorativeNS+":53")
-			if err != nil {
-				return err
-			}
-
-			if len(in.Answer) > 0 {
-				break
-			}
-
-			fallbackCnt++
-			if fallbackCnt >= preCheckDNSFallbackCount {
-				return errors.New("Could not retrieve the value from DNS in a timely manner. Aborting.")
-			}
-
-			time.Sleep(time.Second * time.Duration(fallbackCnt))
-		}
-	}
+	preCheckDNS(domain, fqdn)
 
 	jsonBytes, err := json.Marshal(challenge{Resource: "challenge", Type: chlng.Type, Token: chlng.Token, KeyAuthorization: keyAuth})
 	if err != nil {
@@ -138,3 +101,42 @@ Loop:
 
 	return nil
 }
+
+func checkDNS(domain, fqdn string) bool {
+	// check if the expected DNS entry was created. If not wait for some time and try again.
+	m := new(dns.Msg)
+	m.SetQuestion(domain+".", dns.TypeSOA)
+	c := new(dns.Client)
+	in, _, err := c.Exchange(m, "8.8.8.8:53")
+	if err != nil {
+		return false
+	}
+
+	var authorativeNS string
+	for _, answ := range in.Answer {
+		soa := answ.(*dns.SOA)
+		authorativeNS = soa.Ns
+	}
+
+	fallbackCnt := 0
+	for fallbackCnt < preCheckDNSFallbackCount {
+		m.SetQuestion(fqdn, dns.TypeTXT)
+		in, _, err = c.Exchange(m, authorativeNS+":53")
+		if err != nil {
+			return false
+		}
+
+		if len(in.Answer) > 0 {
+			return true
+		}
+
+		fallbackCnt++
+		if fallbackCnt >= preCheckDNSFallbackCount {
+			return false
+		}
+
+		time.Sleep(time.Second * time.Duration(fallbackCnt))
+	}
+
+	return false
+}

acme/dns_challenge_test.go

@@ -11,8 +11,8 @@ import (
 )
 
 func TestDNSValidServerResponse(t *testing.T) {
-	preCheckDNS = func() bool {
-		return false
+	preCheckDNS = func(domain, fqdn string) bool {
+		return true
 	}
 	privKey, _ := generatePrivateKey(rsakey, 512)