mirror of
https://github.com/ezyang/htmlpurifier.git
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Protect against font family innerHTML/cssText attacks.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>
This commit is contained in:
Edward Z. Yang
parent
0dd9e4faf4
commit
afb007d22f
3
NEWS
3
NEWS
@ -19,6 +19,9 @@ NEWS ( CHANGELOG and HISTORY ) HTMLPurifier
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spaces. This constitutes a slight semantic change, which can be
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reverted using %Output.FixInnerHTML. Reported by Neike Taika-Tessaro
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and Mario Heiderich.
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# Protect against cssText/innerHTML by restricting allowed characters
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used in fonts further than mandated by the specification. Reported
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by Neike Taika-Tessaro and Mario Heiderich.
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! Added %HTML.Nofollow to add rel="nofollow" to external links.
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! More types of SPL autoloaders allowed on later versions of PHP.
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! Implementations for position, top, left, right, bottom, z-index
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@ -96,27 +96,32 @@
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</directive>
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<directive id="Output.CommentScriptContents">
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<file name="HTMLPurifier/Generator.php">
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<line>56</line>
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<line>61</line>
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</file>
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</directive>
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<directive id="Output.FixInnerHTML">
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<file name="HTMLPurifier/Generator.php">
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<line>62</line>
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</file>
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</directive>
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<directive id="Output.SortAttr">
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<file name="HTMLPurifier/Generator.php">
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<line>57</line>
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<line>63</line>
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</file>
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</directive>
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<directive id="Output.FlashCompat">
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<file name="HTMLPurifier/Generator.php">
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<line>58</line>
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<line>64</line>
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</file>
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</directive>
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<directive id="Output.TidyFormat">
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<file name="HTMLPurifier/Generator.php">
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<line>87</line>
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<line>93</line>
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</file>
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</directive>
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<directive id="Core.NormalizeNewlines">
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<file name="HTMLPurifier/Generator.php">
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<line>101</line>
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<line>107</line>
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</file>
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<file name="HTMLPurifier/Lexer.php">
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<line>266</line>
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@ -124,7 +129,7 @@
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</directive>
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<directive id="Output.Newline">
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<file name="HTMLPurifier/Generator.php">
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<line>102</line>
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<line>108</line>
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</file>
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</directive>
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<directive id="HTML.BlockWrapper">
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@ -254,6 +259,9 @@
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<file name="HTMLPurifier/URIDefinition.php">
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<line>64</line>
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</file>
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<file name="HTMLPurifier/URIScheme.php">
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<line>75</line>
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</file>
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</directive>
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<directive id="URI.Base">
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<file name="HTMLPurifier/URIDefinition.php">
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@ -288,6 +296,11 @@
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<line>12</line>
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</file>
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</directive>
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<directive id="CSS.AllowedFonts">
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<file name="HTMLPurifier/AttrDef/CSS/FontFamily.php">
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<line>50</line>
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</file>
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</directive>
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<directive id="Attr.AllowedClasses">
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<file name="HTMLPurifier/AttrDef/HTML/Class.php">
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<line>18</line>
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@ -454,7 +467,7 @@
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</directive>
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<directive id="Core.EscapeInvalidTags">
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<file name="HTMLPurifier/Strategy/MakeWellFormed.php">
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<line>45</line>
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<line>53</line>
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</file>
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<file name="HTMLPurifier/Strategy/RemoveForeignElements.php">
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<line>19</line>
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@ -6,6 +6,39 @@
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class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
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{
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protected $mask = null;
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public function __construct() {
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$this->mask = '- ';
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for ($c = 'a'; $c <= 'z'; $c++) $this->mask .= $c;
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for ($c = 'A'; $c <= 'Z'; $c++) $this->mask .= $c;
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for ($c = '0'; $c <= '9'; $c++) $this->mask .= $c; // cast-y, but should be fine
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// special bytes used by UTF-8
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for ($i = 0x80; $i <= 0xFF; $i++) {
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// We don't bother excluding invalid bytes in this range,
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// because the our restriction of well-formed UTF-8 will
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// prevent these from ever occurring.
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$this->mask .= chr($i);
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}
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/*
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PHP's internal strcspn implementation is
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O(length of string * length of mask), making it inefficient
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for large masks. However, it's still faster than
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preg_match 8)
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for (p = s1;;) {
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spanp = s2;
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do {
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if (*spanp == c || p == s1_end) {
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return p - s1;
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}
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} while (spanp++ < (s2_end - 1));
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c = *++p;
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}
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*/
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// possible optimization: invert the mask.
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}
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public function validate($string, $config, $context) {
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static $generic_names = array(
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'serif' => true,
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@ -56,17 +89,103 @@ class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
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// shouldn't show up regardless
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$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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// Here, there are various classes of characters which need
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// to be treated differently:
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// - Alphanumeric characters are essentially safe. We
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// handled these above.
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// - Spaces require quoting, though most parsers will do
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// the right thing if there aren't any characters that
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// can be misinterpreted
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// - Dashes rarely occur, but they fairly unproblematic
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// for parsing/rendering purposes.
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// The above characters cover the majority of Western font
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// names.
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// - Arbitrary Unicode characters not in ASCII. Because
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// most parsers give little thought to Unicode, treatment
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// of these codepoints is basically uniform, even for
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// punctuation-like codepoints. These characters can
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// show up in non-Western pages and are supported by most
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// major browsers, for example: "ＭＳ 明朝" is a
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// legitimate font-name
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// <http://ja.wikipedia.org/wiki/MS_明朝>. See
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// the CSS3 spec for more examples:
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// <http://www.w3.org/TR/2011/WD-css3-fonts-20110324/localizedfamilynames.png>
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// You can see live samples of these on the Internet:
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// <http://www.google.co.jp/search?q=font-family+ＭＳ+明朝|ゴシック>
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// However, most of these fonts have ASCII equivalents:
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// for example, 'MS Mincho', and it's considered
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// professional to use ASCII font names instead of
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// Unicode font names. Thanks Takeshi Terada for
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// providing this information.
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// The following characters, to my knowledge, have not been
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// used to name font names.
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// - Single quote. While theoretically you might find a
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// font name that has a single quote in its name (serving
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// as an apostrophe, e.g. Dave's Scribble), I haven't
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// been able to find any actual examples of this.
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// Internet Explorer's cssText translation (which I
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// believe is invoked by innerHTML) normalizes any
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// quoting to single quotes, and fails to escape single
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// quotes. (Note that this is not IE's behavior for all
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// CSS properties, just some sort of special casing for
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// font-family). So a single quote *cannot* be used
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// safely in the font-family context if there will be an
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// innerHTML/cssText translation. Note that Firefox 3.x
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// does this too.
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// - Double quote. In IE, these get normalized to
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// single-quotes, no matter what the encoding. (Fun
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// fact, in IE8, the 'content' CSS property gained
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// support, where they special cased to preserve encoded
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// double quotes, but still translate unadorned double
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// quotes into single quotes.) So, because their
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// fixpoint behavior is identical to single quotes, they
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// cannot be allowed either. Firefox 3.x displays
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// single-quote style behavior.
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// - Backslashes are reduced by one (so \\ -> \) every
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// iteration, so they cannot be used safely. This shows
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// up in IE7, IE8 and FF3
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// - Semicolons, commas and backticks are handled properly.
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// - The rest of the ASCII punctuation is handled properly.
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// We haven't checked what browsers do to unadorned
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// versions, but this is not important as long as the
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// browser doesn't /remove/ surrounding quotes (as IE does
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// for HTML).
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//
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// With these results in hand, we conclude that there are
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// various levels of safety:
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// - Paranoid: alphanumeric, spaces and dashes(?)
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// - International: Paranoid + non-ASCII Unicode
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// - Edgy: Everything except quotes, backslashes
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// - NoJS: Standards compliance, e.g. sod IE. Note that
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// with some judicious character escaping (since certain
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// types of escaping doesn't work) this is theoretically
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// OK as long as innerHTML/cssText is not called.
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// We believe that international is a reasonable default
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// (that we will implement now), and once we do more
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// extensive research, we may feel comfortable with dropping
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// it down to edgy.
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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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// Edgy: alphanumeric, spaces, dashes and Unicode. Use of
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// str(c)spn assumes that the string was already well formed
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// Unicode (which of course it is).
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if (strspn($font, $this->mask) !== strlen($font)) {
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continue;
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}
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// Historical:
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// In the absence of innerHTML/cssText, these ugly
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// transforms don't pose a security risk (as \\ and \"
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// might--these escapes are not supported by most browsers).
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// We could try to be clever and use single-quote wrapping
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// when there is a double quote present, but I have choosen
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// not to implement that. (NOTE: you can reduce the amount
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// of escapes by one depending on what quoting style you use)
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// $font = str_replace('\\', '\\5C ', $font);
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// $font = str_replace('"', '\\22 ', $font);
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// $font = str_replace("'", '\\27 ', $font);
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// font possibly with spaces, requires quoting
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$final .= "'$font', ";
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}
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$final = rtrim($final, ', ');
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if ($final === '') return false;
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@ -185,7 +185,7 @@ class HTMLPurifier_URI
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// Reconstruct the result
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// One might wonder about parsing quirks from browsers after
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// this reconstruction. Unfortunately, parsing behaviro depends
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// this reconstruction. Unfortunately, parsing behavior depends
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// on what *scheme* was employed (file:///foo is handled *very*
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// differently than http:///foo), so unfortunately we have to
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// defer to the schemes to do the right thing.
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@ -8,30 +8,32 @@ class HTMLPurifier_AttrDef_CSS_FontFamilyTest extends HTMLPurifier_AttrDefHarnes
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$this->def = new HTMLPurifier_AttrDef_CSS_FontFamily();
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$this->assertDef('Gill, Helvetica, sans-serif');
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$this->assertDef('"Times New Roman", serif');
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$this->assertDef('\'Times New Roman\'', '"Times New Roman"');
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$this->assertDef("'Times New Roman', serif");
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$this->assertDef("\"Times New Roman\"", "'Times New Roman'");
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$this->assertDef('01234');
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$this->assertDef(',', false);
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$this->assertDef('Times New Roman, serif', '"Times New Roman", serif');
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$this->assertDef($d = '"John\'s Font"');
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$this->assertDef("John's Font", $d);
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$this->assertDef($d = "\"\xE5\xAE\x8B\xE4\xBD\x93\"");
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$this->assertDef('Times New Roman, serif', "'Times New Roman', serif");
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$this->assertDef($d = "'\xE5\xAE\x8B\xE4\xBD\x93'");
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$this->assertDef("\xE5\xAE\x8B\xE4\xBD\x93", $d);
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$this->assertDef("'\\','f'", "\"\\5C \", f");
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$this->assertDef("'\\01'", "\"\"");
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$this->assertDef("'\\20'", "\" \"");
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$this->assertDef("\\0020", "\" \"");
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$this->assertDef("'\\01'", "''");
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$this->assertDef("'\\20'", "' '");
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$this->assertDef("\\0020", "' '");
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$this->assertDef("'\\000045'", "E");
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$this->assertDef("','", false);
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$this->assertDef("',' foobar','", "\" foobar\"");
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$this->assertDef("'\\27'", "\"'\"");
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$this->assertDef('"\\22"', "\"\\22 \"");
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$this->assertDef('"\\""', "\"\\22 \"");
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$this->assertDef('"\'"', "\"'\"");
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$this->assertDef("',' foobar','", "' foobar'");
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$this->assertDef("'\\000045a'", "Ea");
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$this->assertDef("'\\00045 a'", "Ea");
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$this->assertDef("'\\00045 a'", "\"E a\"");
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$this->assertDef("'\\00045 a'", "'E a'");
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$this->assertDef("'\\\nf'", "f");
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// No longer supported, except maybe in NoJS mode (see source
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// file for more explanation)
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//$this->assertDef($d = '"John\'s Font"');
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//$this->assertDef("John's Font", $d);
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//$this->assertDef("'\\','f'", "\"\\5C \", f");
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//$this->assertDef("'\\27'", "\"'\"");
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//$this->assertDef('"\\22"', "\"\\22 \"");
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//$this->assertDef('"\\""', "\"\\22 \"");
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//$this->assertDef('"\'"', "\"'\"");
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}
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function testAllowed() {
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@ -40,8 +42,8 @@ class HTMLPurifier_AttrDef_CSS_FontFamilyTest extends HTMLPurifier_AttrDefHarnes
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$this->assertDef('serif');
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$this->assertDef('sans-serif', false);
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$this->assertDef('serif, sans-serif', 'serif');
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$this->assertDef('Times New Roman', '"Times New Roman"');
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$this->assertDef('"Times New Roman"');
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$this->assertDef('Times New Roman', "'Times New Roman'");
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$this->assertDef("'Times New Roman'");
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$this->assertDef('foo', false);
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}
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@ -11,10 +11,10 @@ class HTMLPurifier_AttrDef_CSS_FontTest extends HTMLPurifier_AttrDefHarness
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// hodgepodge of usage cases from W3C spec, but " -> '
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$this->assertDef('12px/14px sans-serif');
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$this->assertDef('80% sans-serif');
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$this->assertDef('x-large/110% "New Century Schoolbook", serif');
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$this->assertDef("x-large/110% 'New Century Schoolbook', serif");
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$this->assertDef('bold italic large Palatino, serif');
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$this->assertDef('normal small-caps 120%/120% fantasy');
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$this->assertDef('300 italic 1.3em/1.7em "FB Armada", sans-serif');
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$this->assertDef("300 italic 1.3em/1.7em 'FB Armada', sans-serif");
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$this->assertDef('600 9px Charcoal');
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$this->assertDef('600 9px/ 12px Charcoal', '600 9px/12px Charcoal');
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@ -62,7 +62,7 @@ class HTMLPurifier_AttrDef_CSSTest extends HTMLPurifier_AttrDefHarness
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$this->assertDef('width:-50px;', false);
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$this->assertDef('text-decoration:underline;');
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$this->assertDef('font-family:sans-serif;');
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$this->assertDef('font-family:Gill, "Times New Roman", sans-serif;');
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$this->assertDef("font-family:Gill, 'Times New Roman', sans-serif;");
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$this->assertDef('font:12px serif;');
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$this->assertDef('border:1px solid #000;');
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$this->assertDef('border-bottom:2em double #FF00FA;');
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@ -79,10 +79,13 @@ class HTMLPurifier_Filter_ExtractStyleBlocksTest extends HTMLPurifier_Harness
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}
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function test_cleanCSS_angledBrackets() {
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$this->assertCleanCSS(
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".class {\nfont-family:'</style>';\n}",
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".class {\nfont-family:\"\\3C /style\\3E \";\n}"
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);
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// [Content] No longer can smuggle in angled brackets using
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// font-family; when we add support for 'content', reinstate
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// this test.
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//$this->assertCleanCSS(
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// ".class {\nfont-family:'</style>';\n}",
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// ".class {\nfont-family:\"\\3C /style\\3E \";\n}"
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//);
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}
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function test_cleanCSS_angledBrackets2() {
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@ -97,6 +100,7 @@ class HTMLPurifier_Filter_ExtractStyleBlocksTest extends HTMLPurifier_Harness
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$this->assertCleanCSS("div {bogus:tree;}", "div {\n}");
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}
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/* [CONTENT]
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function test_cleanCSS_escapeCodes() {
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$this->assertCleanCSS(
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".class {\nfont-family:\"\\3C /style\\3E \";\n}"
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@ -109,6 +113,7 @@ class HTMLPurifier_Filter_ExtractStyleBlocksTest extends HTMLPurifier_Harness
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".class {\nfont-family:\"</style>\";\n}"
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);
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}
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*/
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function test_cleanCSS_scope() {
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$this->config->set('Filter.ExtractStyleBlocks.Scope', '#foo');
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@ -4,5 +4,5 @@ if (!function_exists('iconv')) return true;
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Core.Encoding = "Shift_JIS"
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Core.EscapeNonASCIICharacters = true
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--HTML--
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<b style="font-family:"¥";">111</b>
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<b style="font-family:'¥';">111</b>
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--# vim: et sw=4 sts=4
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@ -3,7 +3,7 @@ if (!function_exists('iconv')) return true;
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--INI--
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Core.Encoding = Shift_JIS
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--HTML--
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<b style="font-family:"¥";">111</b>
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<b style="font-family:'¥';">111</b>
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--EXPECT--
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<b style="font-family:"";">111</b>
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<b style="font-family:'';">111</b>
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--# vim: et sw=4 sts=4
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