[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3058) HTML and CSS sanitation filters for Seam Text

[Christian Bauer (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBSEAM-3058?page=comments#action_12415141 ] 
            
Christian Bauer commented on JBSEAM-3058:
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Implemented in trunk SeamTextParser.Sanitizer with the allowed elements/attributes/attribute values and CSS filtering from, following http://wiki.whatwg.org/wiki/Sanitization_rules. See the Javadoc for changed and additions. Certain markup is now no longer valid, e.g. <div style="border: 1px solid;"> now has to be <div style="border-width: 1px; border-style: solid;">. This is an issue for Seam 2.0.x backporting but we have to disallow _something_. I'll look at that again and then also commit to 2.0.x branch.



> HTML and CSS sanitation filters for Seam Text
> ---------------------------------------------
>
>                 Key: JBSEAM-3058
>                 URL: http://jira.jboss.com/jira/browse/JBSEAM-3058
>             Project: Seam
>          Issue Type: Task
>          Components: Wiki, Seam Text
>            Reporter: Christian Bauer
>         Assigned To: Christian Bauer
>            Priority: Blocker
>             Fix For: 2.0.x
>
>
> Although we only allow certain elments and attributes, and do not allow quotes and ampersands in HTML fragments parsed through Seam Text, various XSS attack vectors are still open. 
> 1. We can't remove IMG and A from the allowed list of HTML elements because they are already used in probably hundreds of documents. So we need to filter the SRC and HREF attribute values.
> 2. We need to filter the STYLE attribute on any element, because a) background:url(javascript) is executed on most browser b) Internet Explorer also executes background-color: expression(javascript). But, the STYLE attribute it is used for document layout on production sites (mostly with DIV elements) and there simply is no alternative.
> The following rules from the Ruby/Python rules can be a starting point: http://wiki.whatwg.org/wiki/Sanitization_rules
> First, implement the callbacks/stacks in seam-text.g so this filter can be hooked in as a SeamTextParser extension.

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