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git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@435 48356398-32a2-884e-a903-53898d9a118a
49 lines
2.4 KiB
Plaintext
49 lines
2.4 KiB
Plaintext
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Security
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Like anything that claims to afford security, HTML_Purifier can be circumvented
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through negligence of people. This class will do its job: no more, no less,
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and it's up to you to provide it the proper information and proper context
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to be effective. Things to remember:
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1. Character Encoding: UTF-8.
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Currently, the parser runs under the assumption that it is dealing
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with UTF-8. Not ISO-8859-1 or Windows-1252, UTF-8. And definitely not "no
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character encoding explicitly stated" or UTF-7. If you're not using UTF-8 as
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your character encoding, make sure you configure HTML Purifier or switch
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to UTF-8. Now. Also, make sure any input is properly converted to UTF-8, or
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the parser will mangle it badly (though it won't be a security risk if you're
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outputting it as UTF-8 though). Character encoding is, in general, a knotty
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issue, but do yourself a favor and learn about it:
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<http://www.joelonsoftware.com/articles/Unicode.html>
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2. Doctype: XHTML 1.0 Transitional
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This is what the parser is outputting. For the most
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part, it's compatible with HTML 4.01, but XHTML enforces some very nice things
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that all web developers should use. Regardless, NO DOCTYPE is a NO. Quirks mode
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has waaaay too many quirks for a little parser to handle. We did not select
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strict in order to prevent ourselves from being too draconic on users, but
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this may be configurable in the future. Do you want standards compliance?
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The doctype is a good place to start.
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3. IDs
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They need to be unique, but without some knowledge of the
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rest of the document, it's difficult to know what's unique. %Attr.IDBlacklist
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needs to be set: we may want to consider disallowing IDs by default to
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save lazy programmers.
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4. [PROJECTED] Links
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We're not going to try for spam protection (although
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some hooks for such a module might be nice) but we may offer the ability to
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only accept relative URLs. Pick the one that's right for you.
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5. CSS
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While we can prevent the most flagrant cases from affecting your
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layout (such as absolutely positioned elements), no amount of code is going
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to protect your pages from being attacked by garish colors and plain old
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bad taste. A neat feature would be the ability to define acceptable colors
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in a document, but that's not likely to be implemented for a while. In the
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meantime, be sure to make sure that floated elements (permitted, since they
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can be quite useful) can't mess up your layout. Once again, we may want to
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disable this by default to protect lazy developers.
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