encodeForHtml() vs htmlEditFormat()

StackOverflow https://stackoverflow.com/questions/10597073

  •  09-06-2021
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Pregunta

encodeForHtml() (new in CF10) vs htmlEditFormat(), how are they different?

¿Fue útil?

Solución

I think it is same as encodeForHTML function in java's OWASP ESAPI. More secure to avoid XSS attack to use content in HTML.

<cfsavecontent variable="htmlcontent">
<html>
    <head>
        <script>function hello() {alert('hello')}</script>
    </head>
    <body>
        <a href="#bookmark">Book Mark &amp; Anchor</a><br/>
        <div class="xyz">Div contains & here.</div>
        <IMG     SRC=&#x6A&#x61&#x76&#x61&#x73&#x63&#x72&#x69&#x70&#x74&#x3A&#x61&#x6C&#x65&#x72&#x74&#x28&#    x27&#x58&#x53&#x53&#x27&#x29>
    <IMG SRC=&#0000106&#0000097&#0000118&#0000097&#0000115&#0000099&#0000114&#0000105&#0000112&#0000116&#0000058&#0000097&#0000108&#0000101&#0000114&#0000116&#0000040&#0000039&#0000088&#0000083&#0000083&#0000039&#0000041>
</body>
</html></cfsavecontent>

<cfoutput>#htmleditformat(htmlcontent)#</cfoutput>
<br />
<cfoutput>#encodeforhtml(htmlcontent)#</cfoutput>

Otros consejos

EncodeFor* functions are based on the OWASP ESAPI libraries. The main difference is that HTMLEditFormat() merely replaces "bad" strings, like &, < and > with good strings, like &amp;, &lt; and &gt; whereas EncodeForHTML() is smarter, with one advantage being it can recognize content that is already encoded and not double-encode it.

For example, if a user submitted the following content to your site:

<div>
Here is <i>test</i> html content includes<br/>
<script>alert('hello')</script>
Notice how &amp; rendered with both functions.
</div>

Both HTMLEditFormat() and EncodeForHTML() would properly escape the '<' and '>' characters. But HTMLEditFormat() would blindly encode the & again such that your output looks like:

... how &amp;amp; rendered ...

Where it would otherwise look like with encodeForHTML():

... how &amp; rendered ...

HTMLEditFormat() couldn't tell that the ampersand was already encoded, so it re-encoded it again. This is a trivial example, but it demonstrates how the ESAPI libraries are smarter and, therefore, more secure.

Bottom line, there's no reason to use HTMLEditFormat() in CF10+. For maximum protection, you should replace the Format functions with the Encode functions.

The complete example above and more background are at isummation: http://www.isummation.com/blog/day-2-avoid-cross-site-scripting-xss-using-coldfusion-10-part-1/

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