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<?php | |
/** | |
* @file | |
* Contains \Drupal\Component\Utility\Xss. | |
*/ | |
namespace Drupal\Component\Utility; | |
/** | |
* Provides helper to filter for cross-site scripting. | |
* | |
* @ingroup utility | |
*/ | |
class Xss { | |
/** | |
* The list of HTML tags allowed by filterAdmin(). | |
* | |
* @var array | |
* | |
* @see \Drupal\Component\Utility\Xss::filterAdmin() | |
*/ | |
protected static $adminTags = array('a', 'abbr', 'acronym', 'address', 'article', 'aside', 'b', 'bdi', 'bdo', 'big', 'blockquote', 'br', 'caption', 'cite', 'code', 'col', 'colgroup', 'command', 'dd', 'del', 'details', 'dfn', 'div', 'dl', 'dt', 'em', 'figcaption', 'figure', 'footer', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'header', 'hgroup', 'hr', 'i', 'img', 'ins', 'kbd', 'li', 'mark', 'menu', 'meter', 'nav', 'ol', 'output', 'p', 'pre', 'progress', 'q', 'rp', 'rt', 'ruby', 's', 'samp', 'section', 'small', 'span', 'strong', 'sub', 'summary', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'time', 'tr', 'tt', 'u', 'ul', 'var', 'wbr'); | |
/** | |
* The default list of HTML tags allowed by filter(). | |
* | |
* @var array | |
* | |
* @see \Drupal\Component\Utility\Xss::filter() | |
*/ | |
protected static $htmlTags = array('a', 'em', 'strong', 'cite', 'blockquote', 'code', 'ul', 'ol', 'li', 'dl', 'dt', 'dd'); | |
/** | |
* Filters HTML to prevent cross-site-scripting (XSS) vulnerabilities. | |
* | |
* Based on kses by Ulf Harnhammar, see http://sourceforge.net/projects/kses. | |
* For examples of various XSS attacks, see: http://ha.ckers.org/xss.html. | |
* | |
* This code does four things: | |
* - Removes characters and constructs that can trick browsers. | |
* - Makes sure all HTML entities are well-formed. | |
* - Makes sure all HTML tags and attributes are well-formed. | |
* - Makes sure no HTML tags contain URLs with a disallowed protocol (e.g. | |
* javascript:). | |
* | |
* @param $string | |
* The string with raw HTML in it. It will be stripped of everything that | |
* can cause an XSS attack. | |
* @param array $html_tags | |
* An array of HTML tags. | |
* | |
* @return string | |
* An XSS safe version of $string, or an empty string if $string is not | |
* valid UTF-8. | |
* | |
* @see \Drupal\Component\Utility\Unicode::validateUtf8() | |
* | |
* @ingroup sanitization | |
*/ | |
public static function filter($string, array $html_tags = NULL) { | |
if (is_null($html_tags)) { | |
$html_tags = static::$htmlTags; | |
} | |
// Only operate on valid UTF-8 strings. This is necessary to prevent cross | |
// site scripting issues on Internet Explorer 6. | |
if (!Unicode::validateUtf8($string)) { | |
return ''; | |
} | |
// Remove NULL characters (ignored by some browsers). | |
$string = str_replace(chr(0), '', $string); | |
// Remove Netscape 4 JS entities. | |
$string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string); | |
// Defuse all HTML entities. | |
$string = str_replace('&', '&', $string); | |
// Change back only well-formed entities in our whitelist: | |
// Decimal numeric entities. | |
$string = preg_replace('/&#([0-9]+;)/', '&#\1', $string); | |
// Hexadecimal numeric entities. | |
$string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string); | |
// Named entities. | |
$string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string); | |
$html_tags = array_flip($html_tags); | |
// Late static binding does not work inside anonymous functions. | |
$class = get_called_class(); | |
$splitter = function ($matches) use ($html_tags, $class) { | |
return $class::split($matches[1], $html_tags, $class); | |
}; | |
// Strip any tags that are not in the whitelist. | |
return preg_replace_callback('% | |
( | |
<(?=[^a-zA-Z!/]) # a lone < | |
| # or | |
<!--.*?--> # a comment | |
| # or | |
<[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string | |
| # or | |
> # just a > | |
)%x', $splitter, $string); | |
} | |
/** | |
* Applies a very permissive XSS/HTML filter for admin-only use. | |
* | |
* Use only for fields where it is impractical to use the | |
* whole filter system, but where some (mainly inline) mark-up | |
* is desired (so \Drupal\Component\Utility\Html::escape() is | |
* not acceptable). | |
* | |
* Allows all tags that can be used inside an HTML body, save | |
* for scripts and styles. | |
* | |
* @param string $string | |
* The string to apply the filter to. | |
* | |
* @return string | |
* The filtered string. | |
* | |
* @ingroup sanitization | |
* | |
* @see \Drupal\Component\Utility\Xss::getAdminTagList() | |
* | |
*/ | |
public static function filterAdmin($string) { | |
return static::filter($string, static::$adminTags); | |
} | |
/** | |
* Processes an HTML tag. | |
* | |
* @param string $string | |
* The HTML tag to process. | |
* @param array $html_tags | |
* An array where the keys are the allowed tags and the values are not | |
* used. | |
* @param string $class | |
* The called class. This method is called from an anonymous function which | |
* breaks late static binding. See https://bugs.php.net/bug.php?id=66622 for | |
* more information. | |
* | |
* @return string | |
* If the element isn't allowed, an empty string. Otherwise, the cleaned up | |
* version of the HTML element. | |
*/ | |
protected static function split($string, $html_tags, $class) { | |
if (substr($string, 0, 1) != '<') { | |
// We matched a lone ">" character. | |
return '>'; | |
} | |
elseif (strlen($string) == 1) { | |
// We matched a lone "<" character. | |
return '<'; | |
} | |
if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9\-]+)\s*([^>]*)>?|(<!--.*?-->)$%', $string, $matches)) { | |
// Seriously malformed. | |
return ''; | |
} | |
$slash = trim($matches[1]); | |
$elem = &$matches[2]; | |
$attrlist = &$matches[3]; | |
$comment = &$matches[4]; | |
if ($comment) { | |
$elem = '!--'; | |
} | |
// When in whitelist mode, an element is disallowed when not listed. | |
if ($class::needsRemoval($html_tags, $elem)) { | |
return ''; | |
} | |
if ($comment) { | |
return $comment; | |
} | |
if ($slash != '') { | |
return "</$elem>"; | |
} | |
// Is there a closing XHTML slash at the end of the attributes? | |
$attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count); | |
$xhtml_slash = $count ? ' /' : ''; | |
// Clean up attributes. | |
$attr2 = implode(' ', $class::attributes($attrlist)); | |
$attr2 = preg_replace('/[<>]/', '', $attr2); | |
$attr2 = strlen($attr2) ? ' ' . $attr2 : ''; | |
return "<$elem$attr2$xhtml_slash>"; | |
} | |
/** | |
* Processes a string of HTML attributes. | |
* | |
* @param string $attributes | |
* The html attribute to process. | |
* | |
* @return string | |
* Cleaned up version of the HTML attributes. | |
*/ | |
protected static function attributes($attributes) { | |
$attributes_array = array(); | |
$mode = 0; | |
$attribute_name = ''; | |
$skip = FALSE; | |
$skip_protocol_filtering = FALSE; | |
while (strlen($attributes) != 0) { | |
// Was the last operation successful? | |
$working = 0; | |
switch ($mode) { | |
case 0: | |
// Attribute name, href for instance. | |
if (preg_match('/^([-a-zA-Z][-a-zA-Z0-9]*)/', $attributes, $match)) { | |
$attribute_name = strtolower($match[1]); | |
$skip = ($attribute_name == 'style' || substr($attribute_name, 0, 2) == 'on'); | |
// Values for attributes of type URI should be filtered for | |
// potentially malicious protocols (for example, an href-attribute | |
// starting with "javascript:"). However, for some non-URI | |
// attributes performing this filtering causes valid and safe data | |
// to be mangled. We prevent this by skipping protocol filtering on | |
// such attributes. | |
// @see \Drupal\Component\Utility\UrlHelper::filterBadProtocol() | |
// @see http://www.w3.org/TR/html4/index/attributes.html | |
$skip_protocol_filtering = substr($attribute_name, 0, 5) === 'data-' || in_array($attribute_name, array( | |
'title', | |
'alt', | |
)); | |
$working = $mode = 1; | |
$attributes = preg_replace('/^[-a-zA-Z][-a-zA-Z0-9]*/', '', $attributes); | |
} | |
break; | |
case 1: | |
// Equals sign or valueless ("selected"). | |
if (preg_match('/^\s*=\s*/', $attributes)) { | |
$working = 1; $mode = 2; | |
$attributes = preg_replace('/^\s*=\s*/', '', $attributes); | |
break; | |
} | |
if (preg_match('/^\s+/', $attributes)) { | |
$working = 1; $mode = 0; | |
if (!$skip) { | |
$attributes_array[] = $attribute_name; | |
} | |
$attributes = preg_replace('/^\s+/', '', $attributes); | |
} | |
break; | |
case 2: | |
// Attribute value, a URL after href= for instance. | |
if (preg_match('/^"([^"]*)"(\s+|$)/', $attributes, $match)) { | |
$thisval = $skip_protocol_filtering ? $match[1] : UrlHelper::filterBadProtocol($match[1]); | |
if (!$skip) { | |
$attributes_array[] = "$attribute_name=\"$thisval\""; | |
} | |
$working = 1; | |
$mode = 0; | |
$attributes = preg_replace('/^"[^"]*"(\s+|$)/', '', $attributes); | |
break; | |
} | |
if (preg_match("/^'([^']*)'(\s+|$)/", $attributes, $match)) { | |
$thisval = $skip_protocol_filtering ? $match[1] : UrlHelper::filterBadProtocol($match[1]); | |
if (!$skip) { | |
$attributes_array[] = "$attribute_name='$thisval'"; | |
} | |
$working = 1; $mode = 0; | |
$attributes = preg_replace("/^'[^']*'(\s+|$)/", '', $attributes); | |
break; | |
} | |
if (preg_match("%^([^\s\"']+)(\s+|$)%", $attributes, $match)) { | |
$thisval = $skip_protocol_filtering ? $match[1] : UrlHelper::filterBadProtocol($match[1]); | |
if (!$skip) { | |
$attributes_array[] = "$attribute_name=\"$thisval\""; | |
} | |
$working = 1; $mode = 0; | |
$attributes = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attributes); | |
} | |
break; | |
} | |
if ($working == 0) { | |
// Not well formed; remove and try again. | |
$attributes = preg_replace('/ | |
^ | |
( | |
"[^"]*("|$) # - a string that starts with a double quote, up until the next double quote or the end of the string | |
| # or | |
\'[^\']*(\'|$)| # - a string that starts with a quote, up until the next quote or the end of the string | |
| # or | |
\S # - a non-whitespace character | |
)* # any number of the above three | |
\s* # any number of whitespaces | |
/x', '', $attributes); | |
$mode = 0; | |
} | |
} | |
// The attribute list ends with a valueless attribute like "selected". | |
if ($mode == 1 && !$skip) { | |
$attributes_array[] = $attribute_name; | |
} | |
return $attributes_array; | |
} | |
/** | |
* Whether this element needs to be removed altogether. | |
* | |
* @param $html_tags | |
* The list of HTML tags. | |
* @param $elem | |
* The name of the HTML element. | |
* | |
* @return bool | |
* TRUE if this element needs to be removed. | |
*/ | |
protected static function needsRemoval($html_tags, $elem) { | |
return !isset($html_tags[strtolower($elem)]); | |
} | |
/** | |
* Gets the list of HTML tags allowed by Xss::filterAdmin(). | |
* | |
* @return array | |
* The list of HTML tags allowed by filterAdmin(). | |
*/ | |
public static function getAdminTagList() { | |
return static::$adminTags; | |
} | |
/** | |
* Gets the standard list of HTML tags allowed by Xss::filter(). | |
* | |
* @return array | |
* The list of HTML tags allowed by Xss::filter(). | |
*/ | |
public static function getHtmlTagList() { | |
return static::$htmlTags; | |
} | |
} |