[Owncloud] Problems with the current template engine

[Bernhard Posselt]

Hi Viktor,

Yeah, HAML is great :)

Could you provide a link to your templating engine, I dont find any
information on that on Google. Or do you mean PHP in general (phtml as
in the extension)?


On 10/09/2012 04:20 PM, Victor Dubiniuk wrote:
> Hi Bernhard,
>
> I have a long experience with Smarty and tried a couple of other template
> engines. Most of them is nothing but PHP written in PHP.
> There are some brilliant exclusions like Slim and Haml in Ruby but both are
> not implemented in PHP completely.
> I consider phtml to be the best option for templates.  One can say it is
> weird for designers but any other non-HTML syntax is weird for designers
> either.
> It's just my humble opinion.  :)
>
> ---
> Victor
>
> On Tue, Oct 9, 2012 at 5:06 PM, Bernhard Posselt <nukeawhale at gmail.com>wrote:
>
>> Hi guys,
>>
>> I've ran into multiple problems with the current template engine setup.
>>
>> * Lack of documenation:
>> Since these are only used by Owncloud, we have to maintain the
>> documentation on the template engine. Using a third party engine would
>> simplify documentation since we only would have to document how this is
>> built into Owncloud. Not to mention that there isnt actually any
>> documentation about the current templating engine at all from what Ive
>> found (http://api.owncloud.org/classes/OCP.Template.html)
>>
>> * Lack of template inheritance:
>> Currently we can only organize templates by splitting them into
>> different parts and including them in a Top-Down like fashion. Template
>> inheritance solves this kinds of problems (an example:
>>
>> https://docs.djangoproject.com/en/dev/topics/templates/#template-inheritance
>> )
>>
>> * Weird and unsafe XSS escaping:
>> Most important topic for me. We currently escape values when they're
>> assigned to a template like $tpl->assign('var', $var). If you dont want
>> to invoke the XSS protection on the variable, you use
>> $tpl->assign('var', $var, false) which is really weird and non obvious.
>> Also: What do we escape? IIRC variables and arrays, but what about
>> objects? We at the news app pass an array with objects to the template
>> layer. Are the properties escaped? If they are, this could lead to
>> potential weird behaviour, not to speak of the performance impact
>> (reflection). As you see, theres no sane way to do XSS escaping when
>> passing values to the template layer.
>>
>> The solution? Easy: escape the values when they are printed to the
>> template. Most template engines forbid you to use PHP in the templates
>> (which is a good decision) and provide their own print statements like
>> Django's {{ variable }} or Rail's <%= variable %>. All printed values
>> are automatically escaped by default! If you want to prevent escaping
>> you just use a filter like {{ var|safe }}. The word safe alone gets me
>> thinking: why is it called safe? What are the risks?
>>
>> * Allowing PHP code in templates:
>> This is not only a security problem stated by the previous point, but
>> also an invitation to code mess. Allowing PHP code in the template
>> tempts people to disregard the MVC principles (like for instance doing
>> database queries in the templates, we have that problem too, I admit),
>> which makes your templates really inflexible and really hard to change.
>> Everytime I try to clean up our templates or adjust them, I give up in
>> frustration because I'd have to adjust all templates, some of which are
>> generated in a recursive way and thus also very complicated to understand.
>>
>> Coming from Django I've looked at two similar engines:
>>
>> http://www.h2o-template.org/
>> http://twig.sensiolabs.org/
>>
>> Both have good documentation, Twig doesnt do autoescaping but theres a
>> block for that. I'm curious about other suggestions, and it would also
>> be fine if they could be reviewed from a security context.
>>
>> PS: Sorry for the long post, here's a potato
>> http://efr0702.files.wordpress.com/2012/03/potato-b.jpg
>>
>> Cheers
>>
>> Bernhard Posselt
>>
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