mirror of
https://github.com/ezyang/htmlpurifier.git
synced 2024-12-23 08:51:53 +00:00
198 lines
8.8 KiB
PHP
198 lines
8.8 KiB
PHP
<?php
|
||
|
||
/**
|
||
* Validates a font family list according to CSS spec
|
||
*/
|
||
class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
|
||
{
|
||
|
||
protected $mask = null;
|
||
|
||
public function __construct() {
|
||
$this->mask = '_- ';
|
||
for ($c = 'a'; $c <= 'z'; $c++) $this->mask .= $c;
|
||
for ($c = 'A'; $c <= 'Z'; $c++) $this->mask .= $c;
|
||
for ($c = '0'; $c <= '9'; $c++) $this->mask .= $c; // cast-y, but should be fine
|
||
// special bytes used by UTF-8
|
||
for ($i = 0x80; $i <= 0xFF; $i++) {
|
||
// We don't bother excluding invalid bytes in this range,
|
||
// because the our restriction of well-formed UTF-8 will
|
||
// prevent these from ever occurring.
|
||
$this->mask .= chr($i);
|
||
}
|
||
|
||
/*
|
||
PHP's internal strcspn implementation is
|
||
O(length of string * length of mask), making it inefficient
|
||
for large masks. However, it's still faster than
|
||
preg_match 8)
|
||
for (p = s1;;) {
|
||
spanp = s2;
|
||
do {
|
||
if (*spanp == c || p == s1_end) {
|
||
return p - s1;
|
||
}
|
||
} while (spanp++ < (s2_end - 1));
|
||
c = *++p;
|
||
}
|
||
*/
|
||
// possible optimization: invert the mask.
|
||
}
|
||
|
||
public function validate($string, $config, $context) {
|
||
static $generic_names = array(
|
||
'serif' => true,
|
||
'sans-serif' => true,
|
||
'monospace' => true,
|
||
'fantasy' => true,
|
||
'cursive' => true
|
||
);
|
||
$allowed_fonts = $config->get('CSS.AllowedFonts');
|
||
|
||
// assume that no font names contain commas in them
|
||
$fonts = explode(',', $string);
|
||
$final = '';
|
||
foreach($fonts as $font) {
|
||
$font = trim($font);
|
||
if ($font === '') continue;
|
||
// match a generic name
|
||
if (isset($generic_names[$font])) {
|
||
if ($allowed_fonts === null || isset($allowed_fonts[$font])) {
|
||
$final .= $font . ', ';
|
||
}
|
||
continue;
|
||
}
|
||
// match a quoted name
|
||
if ($font[0] === '"' || $font[0] === "'") {
|
||
$length = strlen($font);
|
||
if ($length <= 2) continue;
|
||
$quote = $font[0];
|
||
if ($font[$length - 1] !== $quote) continue;
|
||
$font = substr($font, 1, $length - 2);
|
||
}
|
||
|
||
$font = $this->expandCSSEscape($font);
|
||
|
||
// $font is a pure representation of the font name
|
||
|
||
if ($allowed_fonts !== null && !isset($allowed_fonts[$font])) {
|
||
continue;
|
||
}
|
||
|
||
if (ctype_alnum($font) && $font !== '') {
|
||
// very simple font, allow it in unharmed
|
||
$final .= $font . ', ';
|
||
continue;
|
||
}
|
||
|
||
// bugger out on whitespace. form feed (0C) really
|
||
// shouldn't show up regardless
|
||
$font = str_replace(array("\n", "\t", "\r", "\x0C"), ' ', $font);
|
||
|
||
// Here, there are various classes of characters which need
|
||
// to be treated differently:
|
||
// - Alphanumeric characters are essentially safe. We
|
||
// handled these above.
|
||
// - Spaces require quoting, though most parsers will do
|
||
// the right thing if there aren't any characters that
|
||
// can be misinterpreted
|
||
// - Dashes rarely occur, but they fairly unproblematic
|
||
// for parsing/rendering purposes.
|
||
// The above characters cover the majority of Western font
|
||
// names.
|
||
// - Arbitrary Unicode characters not in ASCII. Because
|
||
// most parsers give little thought to Unicode, treatment
|
||
// of these codepoints is basically uniform, even for
|
||
// punctuation-like codepoints. These characters can
|
||
// show up in non-Western pages and are supported by most
|
||
// major browsers, for example: "ＭＳ 明朝" is a
|
||
// legitimate font-name
|
||
// <http://ja.wikipedia.org/wiki/MS_明朝>. See
|
||
// the CSS3 spec for more examples:
|
||
// <http://www.w3.org/TR/2011/WD-css3-fonts-20110324/localizedfamilynames.png>
|
||
// You can see live samples of these on the Internet:
|
||
// <http://www.google.co.jp/search?q=font-family+ＭＳ+明朝|ゴシック>
|
||
// However, most of these fonts have ASCII equivalents:
|
||
// for example, 'MS Mincho', and it's considered
|
||
// professional to use ASCII font names instead of
|
||
// Unicode font names. Thanks Takeshi Terada for
|
||
// providing this information.
|
||
// The following characters, to my knowledge, have not been
|
||
// used to name font names.
|
||
// - Single quote. While theoretically you might find a
|
||
// font name that has a single quote in its name (serving
|
||
// as an apostrophe, e.g. Dave's Scribble), I haven't
|
||
// been able to find any actual examples of this.
|
||
// Internet Explorer's cssText translation (which I
|
||
// believe is invoked by innerHTML) normalizes any
|
||
// quoting to single quotes, and fails to escape single
|
||
// quotes. (Note that this is not IE's behavior for all
|
||
// CSS properties, just some sort of special casing for
|
||
// font-family). So a single quote *cannot* be used
|
||
// safely in the font-family context if there will be an
|
||
// innerHTML/cssText translation. Note that Firefox 3.x
|
||
// does this too.
|
||
// - Double quote. In IE, these get normalized to
|
||
// single-quotes, no matter what the encoding. (Fun
|
||
// fact, in IE8, the 'content' CSS property gained
|
||
// support, where they special cased to preserve encoded
|
||
// double quotes, but still translate unadorned double
|
||
// quotes into single quotes.) So, because their
|
||
// fixpoint behavior is identical to single quotes, they
|
||
// cannot be allowed either. Firefox 3.x displays
|
||
// single-quote style behavior.
|
||
// - Backslashes are reduced by one (so \\ -> \) every
|
||
// iteration, so they cannot be used safely. This shows
|
||
// up in IE7, IE8 and FF3
|
||
// - Semicolons, commas and backticks are handled properly.
|
||
// - The rest of the ASCII punctuation is handled properly.
|
||
// We haven't checked what browsers do to unadorned
|
||
// versions, but this is not important as long as the
|
||
// browser doesn't /remove/ surrounding quotes (as IE does
|
||
// for HTML).
|
||
//
|
||
// With these results in hand, we conclude that there are
|
||
// various levels of safety:
|
||
// - Paranoid: alphanumeric, spaces and dashes(?)
|
||
// - International: Paranoid + non-ASCII Unicode
|
||
// - Edgy: Everything except quotes, backslashes
|
||
// - NoJS: Standards compliance, e.g. sod IE. Note that
|
||
// with some judicious character escaping (since certain
|
||
// types of escaping doesn't work) this is theoretically
|
||
// OK as long as innerHTML/cssText is not called.
|
||
// We believe that international is a reasonable default
|
||
// (that we will implement now), and once we do more
|
||
// extensive research, we may feel comfortable with dropping
|
||
// it down to edgy.
|
||
|
||
// Edgy: alphanumeric, spaces, dashes, underscores and Unicode. Use of
|
||
// str(c)spn assumes that the string was already well formed
|
||
// Unicode (which of course it is).
|
||
if (strspn($font, $this->mask) !== strlen($font)) {
|
||
continue;
|
||
}
|
||
|
||
// Historical:
|
||
// In the absence of innerHTML/cssText, these ugly
|
||
// transforms don't pose a security risk (as \\ and \"
|
||
// might--these escapes are not supported by most browsers).
|
||
// We could try to be clever and use single-quote wrapping
|
||
// when there is a double quote present, but I have choosen
|
||
// not to implement that. (NOTE: you can reduce the amount
|
||
// of escapes by one depending on what quoting style you use)
|
||
// $font = str_replace('\\', '\\5C ', $font);
|
||
// $font = str_replace('"', '\\22 ', $font);
|
||
// $font = str_replace("'", '\\27 ', $font);
|
||
|
||
// font possibly with spaces, requires quoting
|
||
$final .= "'$font', ";
|
||
}
|
||
$final = rtrim($final, ', ');
|
||
if ($final === '') return false;
|
||
return $final;
|
||
}
|
||
|
||
}
|
||
|
||
// vim: et sw=4 sts=4
|