luci-base: only render theme specific sysauth template when it exists

Avoid displaying non-fatal "File not found" exceptions when a theme is not
shipping an own sysauth template.

Fixes: #6118
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 15 insertions, 7 deletions

diff --git a/modules/luci-base/ucode/dispatcher.uc b/modules/luci-base/ucode/dispatcher.uc
index 9d310bb5c2..9500528743 100644
--- a/modules/luci-base/ucode/dispatcher.uc
+++ b/modules/luci-base/ucode/dispatcher.uc
@@ -922,16 +922,18 @@ dispatch = function(_http, path) {
 					http.header('X-LuCI-Login-Required', 'yes');
 
 					let scope = { duser: 'root', fuser: user };
+					let theme_sysauth = `themes/${basename(runtime.env.media)}/sysauth`;
 
-					try {
-						runtime.render(`themes/${basename(runtime.env.media)}/sysauth`, scope);
-					}
-					catch (e) {
-						runtime.env.media_error = `${e}`;
-						runtime.render('sysauth', scope);
+					if (runtime.is_ucode_template(theme_sysauth) || runtime.is_lua_template(theme_sysauth)) {
+						try {
+							return runtime.render(theme_sysauth, scope);
+						}
+						catch (e) {
+							runtime.env.media_error = `${e}`;
+						}
 					}
 
-					return;
+					return runtime.render('sysauth', scope);
 				}
 
 				let cookie_name = (http.getenv('HTTPS') == 'on') ? 'sysauth_https' : 'sysauth_http',
diff --git a/modules/luci-base/ucode/runtime.uc b/modules/luci-base/ucode/runtime.uc
index 89e396d468..e460127e2c 100644
--- a/modules/luci-base/ucode/runtime.uc
+++ b/modules/luci-base/ucode/runtime.uc
@@ -65,6 +65,12 @@ const Class = {
 		return access(`${template_directory}/${path}.ut`);
 	},
 
+	is_lua_template: function(path) {
+		let vm = this.init_lua(true);
+
+		return vm && access(`${vm.get('_G', 'luci', 'template', 'viewdir')}/${path}.htm`);
+	},
+
 	render_ucode: function(path, scope) {
 		let tmplfunc = loadfile(path, { raw_mode: false });