Template engine
From LimeSurvey Manual
Since Louis factored out all HTML from qanda and added a configuration file to the templates, it's a small task to add a template engine, replace the PHP views with e.g. Twig templates.
Use-case
- Template providers don't have to worry about core changes in the question view files
- Template providers can apply any CSS framework specific HTML they want, like Foundation
Requirements
Must have
- Template files in template zip packages can override question view files
- Template zip package can upload template files in template editor
Should have
- Possible to edit Twig/Mustache templates in template editor
Could have
- Include another file : the actual view use different files
Comparison between Twig and Mustache
Function | Twig | Mustache |
---|---|---|
Echo variable | {{var}} | {{var}} |
Echo field in variable | {{var.field}}, {{var['field']}} | {{#var}} {{field}} {{/var}} |
Loop variable | {% for user in users %} ... {% endfor %} | {{#users}} ... {{/users}} |
Branch on boolean | {% if trueOrFalse %} ... {% endif %} | {{#trueOfFalse}} ... {{/trueOrFalse}} |
Translate | Add a filter, like {{"Translate me"|eT}} | Bind eT to lambda and then {{#eT}} "String to translate"" {{/eT}} |
Sandbox | Yes | Not needed |
Security
Longer article about template injection: http://blog.portswigger.net/2015/08/server-side-template-injection.html
The lowest risk approach is to simply use a trivial template engine such as Mustache
About CPU load: It wold be easy for a template designer to make a loop within a loop within a loop etc, to exhaust the CPU power of the server. This vulnerability is in all template engines where you can loop an array (Mustache, Twig). To protect against this, the server should have a max script runtime set.
- BUT: Rendering PDF takes a long time, how to know the right limit?