password connectors: allow overriding the username attribute (password prompt)

This allows users of the LDAP connector to give users of Dex' login
prompt an idea of what they should enter for a username.

Before, irregardless of how the LDAP connector was set up, the prompt
was

    Username
    [_________________]

    Password
    [_________________]

Now, this is configurable, and can be used to say "MyCorp SSO Login" if
that's what it is.

If it's not configured, it will default to "Username".

For the passwordDB connector (local users), it is set to "Email
Address", since this is what it uses.

Signed-off-by: Stephan Renatus <srenatus@chef.io>

server/handlers.go

@@ -250,7 +250,7 @@ func (s *Server) handleConnectorLogin(w http.ResponseWriter, r *http.Request) {
 			}
 			http.Redirect(w, r, callbackURL, http.StatusFound)
 		case connector.PasswordConnector:
-			if err := s.templates.password(w, r.URL.String(), "", false); err != nil {
+			if err := s.templates.password(w, r.URL.String(), "", usernamePrompt(conn), false); err != nil {
 				s.logger.Errorf("Server template error: %v", err)
 			}
 		case connector.SAMLConnector:
@@ -298,7 +298,7 @@ func (s *Server) handleConnectorLogin(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 		if !ok {
-			if err := s.templates.password(w, r.URL.String(), username, true); err != nil {
+			if err := s.templates.password(w, r.URL.String(), username, usernamePrompt(passwordConnector), true); err != nil {
 				s.logger.Errorf("Server template error: %v", err)
 			}
 			return
@@ -1005,3 +1005,11 @@ func (s *Server) tokenErrHelper(w http.ResponseWriter, typ string, description s
 		s.logger.Errorf("token error response: %v", err)
 	}
 }
+
+// Check for username prompt override from connector. Defaults to "Username".
+func usernamePrompt(conn connector.PasswordConnector) string {
+	if attr := conn.Prompt(); attr != "" {
+		return attr
+	}
+	return "Username"
+}

server/server.go

@@ -344,6 +344,10 @@ func (db passwordDB) Refresh(ctx context.Context, s connector.Scopes, identity c
 	return identity, nil
 }
 
+func (db passwordDB) Prompt() string {
+	return "Email Address"
+}
+
 // newKeyCacher returns a storage which caches keys so long as the next
 func newKeyCacher(s storage.Storage, now func() time.Time) storage.Storage {
 	if now == nil {

server/server_test.go

@@ -1017,6 +1017,16 @@ func TestPasswordDB(t *testing.T) {
 
 }
 
+func TestPasswordDBUsernamePrompt(t *testing.T) {
+	s := memory.New(logger)
+	conn := newPasswordDB(s)
+
+	expected := "Email Address"
+	if actual := conn.Prompt(); actual != expected {
+		t.Errorf("expected %v, got %v", expected, actual)
+	}
+}
+
 type storageWithKeysTrigger struct {
 	storage.Storage
 	f func()

server/templates.go

@@ -139,6 +139,7 @@ func loadTemplates(c webConfig, templatesDir string) (*templates, error) {
 		"issuer": func() string { return c.issuer },
 		"logo":   func() string { return c.logoURL },
 		"url":    func(s string) string { return join(c.issuerURL, s) },
+		"lower":  strings.ToLower,
 	}
 
 	tmpls, err := template.New("").Funcs(funcs).ParseFiles(filenames...)
@@ -189,12 +190,13 @@ func (t *templates) login(w http.ResponseWriter, connectors []connectorInfo) err
 	return renderTemplate(w, t.loginTmpl, data)
 }
 
-func (t *templates) password(w http.ResponseWriter, postURL, lastUsername string, lastWasInvalid bool) error {
+func (t *templates) password(w http.ResponseWriter, postURL, lastUsername, usernamePrompt string, lastWasInvalid bool) error {
 	data := struct {
-		PostURL  string
-		Username string
-		Invalid  bool
-	}{postURL, lastUsername, lastWasInvalid}
+		PostURL        string
+		Username       string
+		UsernamePrompt string
+		Invalid        bool
+	}{postURL, lastUsername, usernamePrompt, lastWasInvalid}
 	return renderTemplate(w, t.passwordTmpl, data)
 }