[jira] [Commented] (SLING-5944) Sightly doesn't allow to overwrite the context for `data-sly-element`

["Konrad Windszus (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SLING-5944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15405544#comment-15405544 ] 

Konrad Windszus commented on SLING-5944:
----------------------------------------

Since the list of allowed element names is hard coded in https://github.com/apache/sling/blob/1aa2c8be782ecb858de9030501e67edc4aba1357/bundles/scripting/sightly/engine/src/main/java/org/apache/sling/scripting/sightly/impl/engine/extension/XSSRuntimeExtension.java#L168 currently there is no way to output other element names through {{data-sly-element}}.

> Sightly doesn't allow to overwrite the context for `data-sly-element`
> ---------------------------------------------------------------------
>
>                 Key: SLING-5944
>                 URL: https://issues.apache.org/jira/browse/SLING-5944
>             Project: Sling
>          Issue Type: Bug
>          Components: Scripting
>    Affects Versions: Scripting Sightly Engine 1.0.18
>            Reporter: Konrad Windszus
>
> For the following Sightly script
> {code}
> <a data-sly-element="${'invalidelement' @ context='unsafe'}"></a>
> {code}
> the generated Servlet looks like this
> {code}
> Object var_tagvar0 = renderContext.call("xss", renderContext.call("xss", "invalidelement", "unsafe"), "elementName");
>     if (RenderUtils.toBoolean(var_tagvar0)) {
>         out.write("<");
>         out.write(RenderUtils.toString(var_tagvar0));
>     }
>     if (!RenderUtils.toBoolean(var_tagvar0)) {
>         out.write("<a");
>     }
>     out.write(">");
>     if (RenderUtils.toBoolean(var_tagvar0)) {
>         out.write("</");
>         out.write(RenderUtils.toString(var_tagvar0));
>         out.write(">");
>     }
>     if (!RenderUtils.toBoolean(var_tagvar0)) {
>         out.write("</a>");
>     }
> {code}
> So the element name is XSS protected twice. First with 'unsafe' (which doesn't modify the given literal) and then with 'elementname', which removes the literal.
> This contradicts the documentation at https://docs.adobe.com/docs/en/htl/docs/block-statements.html#element which says
> {quote}
> For security reasons, data-sly-element accepts only the following element names:
> a abbr address article aside b bdi bdo blockquote br caption cite code col colgroup
> data dd del dfn div dl dt em figcaption figure footer h1 h2 h3 h4 h5 h6 header i ins
> kbd li main mark nav ol p pre q rp rt ruby s samp section small span strong sub 
> sup table tbody td tfoot th thead time tr u var wbr
> To set other elements, XSS security must be turned off (@context='unsafe').
> {quote}
> The HTL spec only says
> {quote}
> The element name is automatically XSS-protected with the elementName context, which by the way doesn't allow elements like <script>, <style>, <form>, or <input> (see the Display Context section for the exact list).
> {quote}
> (https://github.com/Adobe-Marketing-Cloud/htl-spec/blob/master/SPECIFICATION.md#224-element).
> I am wondering, if it really is just impossible to give out arbitrary tag names with {{data-sly-element}}. 
> IMHO if another context is given, that one should replace the "elementName" context, instead of being added on top.



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