Add support for Let's Encrypt

Add configuration and certificate manager to use letsencrypt

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

configuration/configuration.go

@@ -95,6 +95,19 @@ type Configuration struct {
 			// Specifies the CA certs for client authentication
 			// A file may contain multiple CA certificates encoded as PEM
 			ClientCAs []string `yaml:"clientcas,omitempty"`
+
+			// LetsEncrypt is used to configuration setting up TLS through
+			// Let's Encrypt instead of manually specifying certificate and
+			// key. If a TLS certificate is specified, the Let's Encrypt
+			// section will not be used.
+			LetsEncrypt struct {
+				// CacheFile specifies cache file to use for lets encrypt
+				// certificates and keys.
+				CacheFile string `yaml:"cachefile,omitempty"`
+
+				// Email is the email to use during Let's Encrypt registration
+				Email string `yaml:"email,omitempty"`
+			} `yaml:"letsencrypt,omitempty"`
 		} `yaml:"tls,omitempty"`
 
 		// Headers is a set of headers to include in HTTP responses. A common

configuration/configuration_test.go

@@ -73,6 +73,10 @@ var configStruct = Configuration{
 			Certificate string   `yaml:"certificate,omitempty"`
 			Key         string   `yaml:"key,omitempty"`
 			ClientCAs   []string `yaml:"clientcas,omitempty"`
+			LetsEncrypt struct {
+				CacheFile string `yaml:"cachefile,omitempty"`
+				Email     string `yaml:"email,omitempty"`
+			} `yaml:"letsencrypt,omitempty"`
 		} `yaml:"tls,omitempty"`
 		Headers http.Header `yaml:"headers,omitempty"`
 		Debug   struct {
@@ -83,6 +87,10 @@ var configStruct = Configuration{
 			Certificate string   `yaml:"certificate,omitempty"`
 			Key         string   `yaml:"key,omitempty"`
 			ClientCAs   []string `yaml:"clientcas,omitempty"`
+			LetsEncrypt struct {
+				CacheFile string `yaml:"cachefile,omitempty"`
+				Email     string `yaml:"email,omitempty"`
+			} `yaml:"letsencrypt,omitempty"`
 		}{
 			ClientCAs: []string{"/path/to/ca.pem"},
 		},

registry/registry.go

@@ -9,6 +9,8 @@ import (
 	"os"
 	"time"
 
+	"rsc.io/letsencrypt"
+
 	log "github.com/Sirupsen/logrus"
 	"github.com/Sirupsen/logrus/formatters/logstash"
 	"github.com/bugsnag/bugsnag-go"
@@ -111,11 +113,10 @@ func (registry *Registry) ListenAndServe() error {
 		return err
 	}
 
-	if config.HTTP.TLS.Certificate != "" {
+	if config.HTTP.TLS.Certificate != "" || config.HTTP.TLS.LetsEncrypt.CacheFile != "" {
 		tlsConf := &tls.Config{
 			ClientAuth:               tls.NoClientCert,
 			NextProtos:               []string{"http/1.1"},
-			Certificates:             make([]tls.Certificate, 1),
 			MinVersion:               tls.VersionTLS10,
 			PreferServerCipherSuites: true,
 			CipherSuites: []uint16{
@@ -130,10 +131,27 @@ func (registry *Registry) ListenAndServe() error {
 			},
 		}
 
+		if config.HTTP.TLS.LetsEncrypt.CacheFile != "" {
+			if config.HTTP.TLS.Certificate != "" {
+				return fmt.Errorf("cannot specify both certificate and Let's Encrypt")
+			}
+			var m letsencrypt.Manager
+			if err := m.CacheFile(config.HTTP.TLS.LetsEncrypt.CacheFile); err != nil {
+				return err
+			}
+			if !m.Registered() {
+				if err := m.Register(config.HTTP.TLS.LetsEncrypt.Email, nil); err != nil {
+					return err
+				}
+			}
+			tlsConf.GetCertificate = m.GetCertificate
+		} else {
+			tlsConf.Certificates = make([]tls.Certificate, 1)
 			tlsConf.Certificates[0], err = tls.LoadX509KeyPair(config.HTTP.TLS.Certificate, config.HTTP.TLS.Key)
 			if err != nil {
 				return err
 			}
+		}
 
 		if len(config.HTTP.TLS.ClientCAs) != 0 {
 			pool := x509.NewCertPool()