50 lines
2.8 KiB
Markdown
50 lines
2.8 KiB
Markdown
[[!template id=plugin name=htmlscrubber core=1 author="[[Joey]]"]]
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[[!tag type/html]]
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This plugin is enabled by default. It sanitizes the html on pages it renders
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to avoid XSS attacks and the like.
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It excludes all html tags and attributes except for those that are
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whitelisted using the same lists as used by Mark Pilgrim's Universal Feed
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Parser, documented at <http://feedparser.org/docs/html-sanitization.html>.
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Notably it strips `style` and `link` tags, and the `style` attribute.
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All attributes that can be used to specify an url are checked to make sure
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that the url is in a known, safe scheme, and to block embedded javascript
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in such urls.
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It uses the [[!cpan HTML::Scrubber]] perl module to perform its html
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sanitisation, and this perl module also deals with various entity encoding
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tricks.
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While I believe that this makes ikiwiki as resistant to malicious html
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content as anything else on the web, I cannot guarantee that it will
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actually protect every user of every browser from every browser security
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hole, badly designed feature, etc. I can provide NO WARRANTY, like it says
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in ikiwiki's [[GPL]] license.
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The web's security model is *fundamentally broken*; ikiwiki's html
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sanitisation is only a patch on the underlying gaping hole that is your web
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browser.
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Note that enabling or disabling the htmlscrubber plugin also affects some
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other HTML-related functionality, such as whether [[meta]] allows
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potentially unsafe HTML tags.
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The `htmlscrubber_skip` configuration setting can be used to skip scrubbing
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of some pages. Set it to a [[ikiwiki/PageSpec]], such as "!*/Discussion", and pages
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matching that can have all the evil CSS, JavsScript, and unsafe html
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elements you like. One safe way to use this is to use [[lockedit]] to lock
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those pages, so only admins can edit them.
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----
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Some examples of embedded javascript that won't be let through when this
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plugin is active:
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* script tag test <script>window.location='http://example.org';</script>
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* <span style="background: url(javascript:window.location='http://example.org/')">CSS script test</span>
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* <span style="any: expression(window.location='http://example.org/')">entity-encoded CSS script test</span>
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* <span style="any: expression(window.location='http://example.org/')">entity-encoded CSS script test</span>
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* <a href="javascript:alert('foo')">click me</a>
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