Fix ACME certificate for wildcard and root domains

provider/acme/provider.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/BurntSushi/ty/fun"
+	"github.com/cenk/backoff"
 	"github.com/containous/flaeg"
 	"github.com/containous/traefik/log"
 	"github.com/containous/traefik/rules"
@@ -74,6 +75,8 @@ type Certificate struct {
 type DNSChallenge struct {
 	Provider         string         `description:"Use a DNS-01 based challenge provider rather than HTTPS."`
 	DelayBeforeCheck flaeg.Duration `description:"Assume DNS propagates after a delay in seconds rather than finding and querying nameservers."`
+	preCheckTimeout  time.Duration
+	preCheckInterval time.Duration
 }
 
 // HTTPChallenge contains HTTP challenge Configuration
@@ -262,6 +265,16 @@ func (p *Provider) getClient() (*acme.Client, error) {
 		if err != nil {
 			return nil, err
 		}
+
+		// Same default values than LEGO
+		p.DNSChallenge.preCheckTimeout = 60 * time.Second
+		p.DNSChallenge.preCheckInterval = 2 * time.Second
+
+		// Set the precheck timeout into the DNSChallenge provider
+		if challengeProviderTimeout, ok := provider.(acme.ChallengeProviderTimeout); ok {
+			p.DNSChallenge.preCheckTimeout, p.DNSChallenge.preCheckInterval = challengeProviderTimeout.Timeout()
+		}
+
 	} else if p.HTTPChallenge != nil && len(p.HTTPChallenge.EntryPoint) > 0 {
 		log.Debug("Using HTTP Challenge provider.")
 
@@ -361,13 +374,20 @@ func (p *Provider) resolveCertificate(domain types.Domain, domainFromConfigurati
 		return nil, fmt.Errorf("cannot get ACME client %v", err)
 	}
 
+	var certificate *acme.CertificateResource
 	bundle := true
-
-	certificate, err := client.ObtainCertificate(uncheckedDomains, bundle, nil, OSCPMustStaple)
-	if err != nil {
-		return nil, fmt.Errorf("cannot obtain certificates: %+v", err)
+	if p.useCertificateWithRetry(uncheckedDomains) {
+		certificate, err = obtainCertificateWithRetry(domains, client, p.DNSChallenge.preCheckTimeout, p.DNSChallenge.preCheckInterval, bundle)
+	} else {
+		certificate, err = client.ObtainCertificate(domains, bundle, nil, OSCPMustStaple)
 	}
 
+	if err != nil {
+		return nil, fmt.Errorf("unable to generate a certificate for the domains %v: %v", uncheckedDomains, err)
+	}
+	if certificate == nil {
+		return nil, fmt.Errorf("domains %v do not generate a certificate", uncheckedDomains)
+	}
 	if len(certificate.Certificate) == 0 || len(certificate.PrivateKey) == 0 {
 		return nil, fmt.Errorf("domains %v generate certificate with no value: %v", uncheckedDomains, certificate)
 	}
@@ -384,6 +404,60 @@ func (p *Provider) resolveCertificate(domain types.Domain, domainFromConfigurati
 	return certificate, nil
 }
 
+func (p *Provider) useCertificateWithRetry(domains []string) bool {
+	// Check if we can use the retry mechanism only if we use the DNS Challenge and if is there are at least 2 domains to check
+	if p.DNSChallenge != nil && len(domains) > 1 {
+		rootDomain := ""
+		for _, searchWildcardDomain := range domains {
+			// Search a wildcard domain if not already found
+			if len(rootDomain) == 0 && strings.HasPrefix(searchWildcardDomain, "*.") {
+				rootDomain = strings.TrimPrefix(searchWildcardDomain, "*.")
+				if len(rootDomain) > 0 {
+					// Look for a root domain which matches the wildcard domain
+					for _, searchRootDomain := range domains {
+						if rootDomain == searchRootDomain {
+							// If the domains list contains a wildcard domain and its root domain, we can use the retry mechanism to obtain the certificate
+							return true
+						}
+					}
+				}
+				// There is only one wildcard domain in the slice, if its root domain has not been found, the retry mechanism does not have to be used
+				return false
+			}
+		}
+	}
+
+	return false
+}
+
+func obtainCertificateWithRetry(domains []string, client *acme.Client, timeout, interval time.Duration, bundle bool) (*acme.CertificateResource, error) {
+	var certificate *acme.CertificateResource
+	var err error
+
+	operation := func() error {
+		certificate, err = client.ObtainCertificate(domains, bundle, nil, OSCPMustStaple)
+		return err
+	}
+
+	notify := func(err error, time time.Duration) {
+		log.Errorf("Error obtaining certificate retrying in %s", time)
+	}
+
+	// Define a retry backOff to let LEGO tries twice to obtain a certificate for both wildcard and root domain
+	ebo := backoff.NewExponentialBackOff()
+	ebo.MaxElapsedTime = 2 * timeout
+	ebo.MaxInterval = interval
+	rbo := backoff.WithMaxRetries(ebo, 2)
+
+	err = backoff.RetryNotify(safe.OperationWithRecover(operation), rbo, notify)
+	if err != nil {
+		log.Errorf("Error obtaining certificate: %v", err)
+		return nil, err
+	}
+
+	return certificate, nil
+}
+
 func dnsOverrideDelay(delay flaeg.Duration) error {
 	if delay == 0 {
 		return nil