Add the URL prefix on the main webapp

server/http.go

@@ -144,8 +144,8 @@ func New(loginService *LoginService, authClient authclient.Client, config *Confi
 	// handler, optional CSRF protection, custom HTTP headers,
 	// etc.
 	mainh := http.NewServeMux()
-	mainh.HandleFunc("/logout", h.handleLogout)
-	mainh.HandleFunc("/", h.handleGrantTicket)
+	mainh.HandleFunc(h.urlFor("/logout"), h.handleLogout)
+	mainh.HandleFunc(h.urlFor("/"), h.handleGrantTicket)
 
 	loginh := login.New(mainh, devMgr, authClient,
 		config.AuthService, config.U2FAppID, urlPrefix,