mirror of
https://github.com/ezyang/htmlpurifier.git
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d3abcb90e3
The new logic is as follows:
* Given a URL to insert into url(), check that it is properly URL
encoded (in particular, a doublequote and backslash never occurs
within it) and then place it as url("http://example.com").
* Given a font name, if it is strictly alphanumeric, it is safe to omit
quotes. Otherwise, wrap in double quotes and replace '"' with '\22 '
(note trailing space) and '\' with '\5C ' (ditto).
We introduce expandCSSEscape() which is a hack for common parsing
idioms in CSS; this means that CSS escapes are now recognized inside
URLs as well as unquoted font names.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>
73 lines
2.4 KiB
PHP
73 lines
2.4 KiB
PHP
<?php
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/**
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* Validates a font family list according to CSS spec
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* @todo whitelisting allowed fonts would be nice
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*/
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class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
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{
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public function validate($string, $config, $context) {
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static $generic_names = array(
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'serif' => true,
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'sans-serif' => true,
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'monospace' => true,
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'fantasy' => true,
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'cursive' => true
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);
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// assume that no font names contain commas in them
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$fonts = explode(',', $string);
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$final = '';
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foreach($fonts as $font) {
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$font = trim($font);
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if ($font === '') continue;
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// match a generic name
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if (isset($generic_names[$font])) {
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$final .= $font . ', ';
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continue;
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}
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// match a quoted name
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if ($font[0] === '"' || $font[0] === "'") {
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$length = strlen($font);
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if ($length <= 2) continue;
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$quote = $font[0];
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if ($font[$length - 1] !== $quote) continue;
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$font = substr($font, 1, $length - 2);
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}
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$font = $this->expandCSSEscape($font);
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// $font is a pure representation of the font name
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if (ctype_alnum($font) && $font !== '') {
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// very simple font, allow it in unharmed
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$final .= $font . ', ';
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continue;
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}
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// bugger out on whitespace. form feed (0C) really
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// shouldn't show up regardless
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$font = str_replace(array("\n", "\t", "\r", "\x0C"), ' ', $font);
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// These ugly transforms don't pose a security
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// risk (as \\ and \" might). We could try to be clever and
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// use single-quote wrapping when there is a double quote
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// present, but I have choosen not to implement that.
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// (warning: this code relies on the selection of quotation
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// mark below)
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$font = str_replace('\\', '\\5C ', $font);
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$font = str_replace('"', '\\22 ', $font);
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// complicated font, requires quoting
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$final .= "\"$font\", "; // note that this will later get turned into "
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}
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$final = rtrim($final, ', ');
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if ($final === '') return false;
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return $final;
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}
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}
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// vim: et sw=4 sts=4
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