Add dns provider duckdns.org (#513)

* Add dns provider duckdns see http://www.duckdns.org/spec.jsp for more info

* Add DNS challenge provider 'exec' (#508)

As discussed in #505, this commits adds a very simple DNS provider which
calls out to an external program which must then add or remove the DNS
record.

* Update duckdns to support caddy, and cleanup some comments

cli.go

@@ -208,6 +208,7 @@ Here is an example bash command using the CloudFlare DNS provider:
 	fmt.Fprintln(w, "\tdigitalocean:\tDO_AUTH_TOKEN")
 	fmt.Fprintln(w, "\tdnsimple:\tDNSIMPLE_EMAIL, DNSIMPLE_OAUTH_TOKEN")
 	fmt.Fprintln(w, "\tdnsmadeeasy:\tDNSMADEEASY_API_KEY, DNSMADEEASY_API_SECRET")
+	fmt.Fprintln(w, "\tduckdns:\tDUCKDNS_TOKEN")
 	fmt.Fprintln(w, "\texoscale:\tEXOSCALE_API_KEY, EXOSCALE_API_SECRET, EXOSCALE_ENDPOINT")
 	fmt.Fprintln(w, "\tgandi:\tGANDI_API_KEY")
 	fmt.Fprintln(w, "\tgandiv5:\tGANDIV5_API_KEY")

providers/dns/dns_providers.go

@@ -13,6 +13,7 @@ import (
 	"github.com/xenolf/lego/providers/dns/dnsimple"
 	"github.com/xenolf/lego/providers/dns/dnsmadeeasy"
 	"github.com/xenolf/lego/providers/dns/dnspod"
+	"github.com/xenolf/lego/providers/dns/duckdns"
 	"github.com/xenolf/lego/providers/dns/dyn"
 	"github.com/xenolf/lego/providers/dns/exec"
 	"github.com/xenolf/lego/providers/dns/exoscale"
@@ -55,6 +56,8 @@ func NewDNSChallengeProviderByName(name string) (acme.ChallengeProvider, error)
 		provider, err = dnsmadeeasy.NewDNSProvider()
 	case "dnspod":
 		provider, err = dnspod.NewDNSProvider()
+	case "duckdns":
+		provider, err = duckdns.NewDNSProvider()
 	case "dyn":
 		provider, err = dyn.NewDNSProvider()
 	case "exoscale":

providers/dns/duckdns/duckdns.go

@@ -0,0 +1,82 @@
+// Adds lego support for http://duckdns.org .
+//
+// See http://www.duckdns.org/spec.jsp for more info on updating TXT records.
+package duckdns
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/xenolf/lego/acme"
+)
+
+// DNSProvider adds and removes the record for the DNS challenge
+type DNSProvider struct {
+	// The duckdns api token
+	token string
+}
+
+// NewDNSProvider returns a new DNS provider using
+// environment variable DUCKDNS_TOKEN for adding and removing the DNS record.
+func NewDNSProvider() (*DNSProvider, error) {
+	duckdnsToken := os.Getenv("DUCKDNS_TOKEN")
+
+	return NewDNSProviderCredentials(duckdnsToken)
+}
+
+// NewDNSProviderCredentials uses the supplied credentials to return a
+// DNSProvider instance configured for http://duckdns.org .
+func NewDNSProviderCredentials(duckdnsToken string) (*DNSProvider, error) {
+	if duckdnsToken == "" {
+		return nil, errors.New("environment variable DUCKDNS_TOKEN not set")
+	}
+
+	return &DNSProvider{token: duckdnsToken}, nil
+}
+
+// makeDuckdnsURL creates a url to clear the set or unset the TXT record.
+// txt == "" will clear the TXT record.
+func makeDuckdnsURL(domain, token, txt string) string {
+	requestBase := fmt.Sprintf("https://www.duckdns.org/update?domains=%s&token=%s", domain, token)
+	if txt == "" {
+		return requestBase + "&clear=true"
+	}
+	return requestBase + "&txt=" + txt
+}
+
+func issueDuckdnsRequest(url string) error {
+	response, err := acme.HTTPClient.Get(url)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	bodyBytes, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		return err
+	}
+	body := string(bodyBytes)
+	if body != "OK" {
+		return fmt.Errorf("Request to change TXT record for duckdns returned the following result (%s) this does not match expectation (OK) used url [%s]", body, url)
+	}
+	return nil
+}
+
+// Present creates a TXT record to fulfil the dns-01 challenge.
+// In duckdns you only have one TXT record shared with
+// the domain and all sub domains.
+//
+// To update the TXT record we just need to make one simple get request.
+func (d *DNSProvider) Present(domain, token, keyAuth string) error {
+	_, txtRecord, _ := acme.DNS01Record(domain, keyAuth)
+	url := makeDuckdnsURL(domain, d.token, txtRecord)
+	return issueDuckdnsRequest(url)
+}
+
+// CleanUp clears duckdns TXT record
+func (d *DNSProvider) CleanUp(domain, token, keyAuth string) error {
+	url := makeDuckdnsURL(domain, d.token, "")
+	return issueDuckdnsRequest(url)
+}

providers/dns/duckdns/duckdns_test.go

@@ -0,0 +1,65 @@
+package duckdns
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	duckdnsLiveTest bool
+	duckdnsToken    string
+	duckdnsDomain   string
+)
+
+func init() {
+	duckdnsToken = os.Getenv("DUCKDNS_TOKEN")
+	duckdnsDomain = os.Getenv("DUCKDNS_DOMAIN")
+	if len(duckdnsDomain) > 0 && len(duckdnsDomain) > 0 {
+		duckdnsLiveTest = true
+	}
+}
+
+func restoreDuckdnsEnv() {
+	os.Setenv("DUCKDNS_TOKEN", duckdnsToken)
+}
+
+func TestNewDNSProviderValidEnv(t *testing.T) {
+	os.Setenv("DUCKDNS_TOKEN", "123")
+	_, err := NewDNSProvider()
+	assert.NoError(t, err)
+	restoreDuckdnsEnv()
+}
+func TestNewDNSProviderMissingCredErr(t *testing.T) {
+	os.Setenv("DUCKDNS_TOKEN", "")
+	_, err := NewDNSProvider()
+	assert.EqualError(t, err, "environment variable DUCKDNS_TOKEN not set")
+	restoreDuckdnsEnv()
+}
+func TestLiveDuckdnsPresent(t *testing.T) {
+	if !duckdnsLiveTest {
+		t.Skip("skipping live test")
+	}
+
+	provider, err := NewDNSProvider()
+	assert.NoError(t, err)
+
+	err = provider.Present(duckdnsDomain, "", "123d==")
+	assert.NoError(t, err)
+}
+
+func TestLiveDuckdnsCleanUp(t *testing.T) {
+	if !duckdnsLiveTest {
+		t.Skip("skipping live test")
+	}
+
+	time.Sleep(time.Second * 10)
+
+	provider, err := NewDNSProvider()
+	assert.NoError(t, err)
+
+	err = provider.CleanUp(duckdnsDomain, "", "123d==")
+	assert.NoError(t, err)
+}