configuration/configuration.go

@@ -114,6 +114,10 @@ type Configuration struct {
 				// Email is the email to use during Let's Encrypt registration
 				Email string `yaml:"email,omitempty"`
+
+				// Hosts specifies the hosts which are allowed to obtain Let's
+				// Encrypt certificates.
+				Hosts []string `yaml:"hosts,omitempty"`
 			} `yaml:"letsencrypt,omitempty"`
 		} `yaml:"tls,omitempty"`

configuration/configuration_test.go

@@ -78,8 +78,9 @@ var configStruct = Configuration{
 			Key         string   `yaml:"key,omitempty"`
 			ClientCAs   []string `yaml:"clientcas,omitempty"`
 			LetsEncrypt struct {
-				CacheFile string `yaml:"cachefile,omitempty"`
-				Email     string `yaml:"email,omitempty"`
+				CacheFile string   `yaml:"cachefile,omitempty"`
+				Email     string   `yaml:"email,omitempty"`
+				Hosts     []string `yaml:"hosts,omitempty"`
 			} `yaml:"letsencrypt,omitempty"`
 		} `yaml:"tls,omitempty"`
 		Headers http.Header `yaml:"headers,omitempty"`
@@ -95,8 +96,9 @@ var configStruct = Configuration{
 			Key         string   `yaml:"key,omitempty"`
 			ClientCAs   []string `yaml:"clientcas,omitempty"`
 			LetsEncrypt struct {
-				CacheFile string `yaml:"cachefile,omitempty"`
-				Email     string `yaml:"email,omitempty"`
+				CacheFile string   `yaml:"cachefile,omitempty"`
+				Email     string   `yaml:"email,omitempty"`
+				Hosts     []string `yaml:"hosts,omitempty"`
 			} `yaml:"letsencrypt,omitempty"`
 		}{
 			ClientCAs: []string{"/path/to/ca.pem"},

docs/configuration.md

@@ -215,6 +215,7 @@ http:
     letsencrypt:
       cachefile: /path/to/cache-file
       email: emailused@letsencrypt.com
+      hosts: [myregistryaddress.org]
   debug:
     addr: localhost:5001
   headers:
@@ -738,6 +739,7 @@ http:
     letsencrypt:
       cachefile: /path/to/cache-file
       email: emailused@letsencrypt.com
+      hosts: [myregistryaddress.org]
   debug:
     addr: localhost:5001
   headers:
@@ -782,12 +784,15 @@ TLS certificates provided by
 > accessible on port `443`. The registry defaults to listening on port `5000`.
 > If you run the registry as a container, consider adding the flag `-p 443:5000`
 > to the `docker run` command or using a similar setting in a cloud
-> configuration.
+> configuration. You should also set the `hosts` option to the list of hostnames
+> that are valid for this registry to avoid trying to get certificates for random
+> hostnames due to malicious clients connecting with bogus SNI hostnames.
 | Parameter | Required | Description                                           |
 |-----------|----------|-------------------------------------------------------|
 | `cachefile` | yes    | Absolute path to a file where the Let's Encrypt agent can cache data. |
 | `email`   | yes      | The email address used to register with Let's Encrypt. |
+| `hosts`   | no       | The hostnames allowed for Let's Encrypt certificates. |
 ### `debug`

registry/registry.go

@@ -147,6 +147,9 @@ func (registry *Registry) ListenAndServe() error {
 					return err
 				}
 			}
+			if len(config.HTTP.TLS.LetsEncrypt.Hosts) > 0 {
+				m.SetHosts(config.HTTP.TLS.LetsEncrypt.Hosts)
+			}
 			tlsConf.GetCertificate = m.GetCertificate
 		} else {
 			tlsConf.Certificates = make([]tls.Certificate, 1)