Wiki source code of Homoiconicity

Version 8.1 by Nicolas Gregoire on 2012/01/05 00:25
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Nicolas Gregoire 2.2 1 == Definition ==
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Nicolas Gregoire 2.1 3 Homoiconicity is the property of a programming language that the code and the data are stored in the same format. For example, the following languages are homoiconics :
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5 * ASM : using bytes stored in memory
6 * Lisp : using lists and theirs sub-types
Nicolas Gregoire 2.1 7 * XSLT : using the XML format
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Nicolas Gregoire 2.2 11 == Triggering embedded code ==
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13 In some contexts (like browsers), XSLT code execution can be triggered while a XML document is parsed, via a xsl:stylesheet tag. The executed XSLT code can be stored on the Internet or in the XML document itself (homoiconicity + self-reference trick). A [[blog post>>http://scarybeastsecurity.blogspot.com/2011/01/harmless-svg-xslt-curiousity.html||rel="__blank"]] by Chris Evans describes a pseudo SVG file triggering a simple RAM DoS . But we can do better ;-)
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Nicolas Gregoire 7.1 15 == Exploiting via dynamic SVG images ==
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Nicolas Gregoire 4.1 17 We can create XML files which will be interpreted by browsers like perfectly valid self-contained dynamic SVG images. The SVG file is then generated on the fly by the (Turing complete) XSLT engine of the browser.
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Nicolas Gregoire 4.1 19 In the following example, the XSLT code will :
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Nicolas Gregoire 2.2 21 * fingerprint the underlying XSLT engine
Nicolas Gregoire 7.1 22 * draw a circle (red if Webkit, green otherwise)
Nicolas Gregoire 8.1 23 * try to exploit [[CVE-2011-1774>>http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1774||rel="__blank" title="CVE-2011-1774"]] if Webkit is detected
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Nicolas Gregoire 8.1 25 Screenshot of Opera :
Nicolas Gregoire 7.1 26 [[image:svg-opera-small.png||style="display: block; margin-left: auto; margin-right: auto"]]
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30 Screenshot of Epiphany :
Nicolas Gregoire 7.1 31 [[image:svg-webkit-small.png||style="display: block; margin-left: auto; margin-right: auto"]]
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Nicolas Gregoire 2.2 33 == Evil SVG images ==
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Nicolas Gregoire 8.1 35 Exploitcolor depends of the OS, ...) and exploit a specific vulnerability. This was demonstrated with [[CVE-2011-1774>>http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1774||rel="__blank" title="CVE-2011-1774"]] and a Webkit exploit tested on Windows, Linux, iOS and webOS.
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37 From a security point of view, it is important to audit
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42 As the SVG format is valid XML too, t
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44 The process is the following :
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46 * The source XML file (do not