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<?php |
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namespace SilverStripe\Forms\HTMLEditor; |
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use DOMAttr; |
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use DOMElement; |
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use SilverStripe\Core\Config\Configurable; |
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use SilverStripe\Core\Injector\Injectable; |
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use SilverStripe\View\Parsers\HTMLValue; |
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use stdClass; |
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/** |
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* Sanitises an HTMLValue so it's contents are the elements and attributes that are whitelisted |
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* using the same configuration as TinyMCE |
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* |
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* See www.tinymce.com/wiki.php/configuration:valid_elements for details on the spec of TinyMCE's |
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* whitelist configuration |
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*/ |
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class HTMLEditorSanitiser |
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{ |
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use Configurable; |
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use Injectable; |
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/** |
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* rel attribute to add to link elements which have a target attribute (usually "_blank") |
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* this is to done to prevent reverse tabnabbing - see https://www.owasp.org/index.php/Reverse_Tabnabbing |
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* noopener includes the behaviour we want, though some browsers don't yet support it and rely |
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* upon using noreferrer instead - see https://caniuse.com/rel-noopener for current browser compatibility |
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* set this to null if you would like to disable this behaviour |
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* set this to an empty string if you would like to remove rel attributes that were previously set |
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* |
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* @var string |
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*/ |
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private static $link_rel_value = 'noopener noreferrer'; |
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/** @var stdClass - $element => $rule hash for whitelist element rules where the element name isn't a pattern */ |
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protected $elements = []; |
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/** @var stdClass - Sequential list of whitelist element rules where the element name is a pattern */ |
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protected $elementPatterns = []; |
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/** @var stdClass - The list of attributes that apply to all further whitelisted elements added */ |
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protected $globalAttributes = []; |
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/** |
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* Construct a sanitiser from a given HTMLEditorConfig |
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* |
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* Note that we build data structures from the current state of HTMLEditorConfig - later changes to |
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* the passed instance won't cause this instance to update it's whitelist |
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* |
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* @param HTMLEditorConfig $config |
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*/ |
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public function __construct(HTMLEditorConfig $config) |
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{ |
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$valid = $config->getOption('valid_elements'); |
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if ($valid) { |
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$this->addValidElements($valid); |
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} |
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$valid = $config->getOption('extended_valid_elements'); |
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if ($valid) { |
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$this->addValidElements($valid); |
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} |
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} |
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/** |
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* Given a TinyMCE pattern (close to unix glob style), create a regex that does the match |
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* |
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* @param $str - The TinyMCE pattern |
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* @return string - The equivalent regex |
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*/ |
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protected function patternToRegex($str) |
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{ |
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return '/^' . preg_replace('/([?+*])/', '.$1', $str ?? '') . '$/'; |
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} |
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/** |
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* Given a valid_elements string, parse out the actual element and attribute rules and add to the |
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* internal whitelist |
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* |
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* Logic based heavily on javascript version from tiny_mce_src.js |
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* |
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* @param string $validElements - The valid_elements or extended_valid_elements string to add to the whitelist |
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*/ |
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protected function addValidElements($validElements) |
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{ |
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$elementRuleRegExp = '/^([#+\-])?([^\[\/]+)(?:\/([^\[]+))?(?:\[([^\]]+)\])?$/'; |
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$attrRuleRegExp = '/^([!\-])?(\w+::\w+|[^=:<]+)?(?:([=:<])(.*))?$/'; |
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$hasPatternsRegExp = '/[*?+]/'; |
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foreach (explode(',', $validElements ?? '') as $validElement) { |
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if (preg_match($elementRuleRegExp ?? '', $validElement ?? '', $matches)) { |
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$prefix = isset($matches[1]) ? $matches[1] : null; |
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$elementName = isset($matches[2]) ? $matches[2] : null; |
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$outputName = isset($matches[3]) ? $matches[3] : null; |
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$attrData = isset($matches[4]) ? $matches[4] : null; |
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// Create the new element |
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$element = new stdClass(); |
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$element->attributes = []; |
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$element->attributePatterns = []; |
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$element->attributesRequired = []; |
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$element->attributesDefault = []; |
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$element->attributesForced = []; |
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foreach (['#' => 'paddEmpty', '-' => 'removeEmpty'] as $match => $means) { |
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$element->$means = ($prefix === $match); |
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} |
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// Copy attributes from global rule into current rule |
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if ($this->globalAttributes) { |
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$element->attributes = array_merge($element->attributes, $this->globalAttributes); |
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} |
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// Attributes defined |
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if ($attrData) { |
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foreach (explode('|', $attrData ?? '') as $attr) { |
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if (preg_match($attrRuleRegExp ?? '', $attr ?? '', $matches)) { |
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$attr = new stdClass(); |
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$attrType = isset($matches[1]) ? $matches[1] : null; |
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$attrName = isset($matches[2]) ? str_replace('::', ':', $matches[2]) : null; |
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$prefix = isset($matches[3]) ? $matches[3] : null; |
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$value = isset($matches[4]) ? $matches[4] : null; |
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// Required |
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if ($attrType === '!') { |
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$element->attributesRequired[] = $attrName; |
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$attr->required = true; |
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} elseif ($attrType === '-') { |
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// Denied from global |
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unset($element->attributes[$attrName]); |
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continue; |
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} |
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// Default value |
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if ($prefix) { |
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if ($prefix === '=') { // Default value |
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$element->attributesDefault[$attrName] = $value; |
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$attr->defaultValue = $value; |
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} elseif ($prefix === ':') { |
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// Forced value |
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$element->attributesForced[$attrName] = $value; |
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$attr->forcedValue = $value; |
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} elseif ($prefix === '<') { |
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// Required values |
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$attr->validValues = explode('?', $value ?? ''); |
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} |
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} |
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// Check for attribute patterns |
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if (preg_match($hasPatternsRegExp ?? '', $attrName ?? '')) { |
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$attr->pattern = $this->patternToRegex($attrName); |
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$element->attributePatterns[] = $attr; |
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} else { |
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$element->attributes[$attrName] = $attr; |
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} |
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} |
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} |
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} |
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// Global rule, store away these for later usage |
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if (!$this->globalAttributes && $elementName == '@') { |
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$this->globalAttributes = $element->attributes; |
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} |
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// Handle substitute elements such as b/strong |
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if ($outputName) { |
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$element->outputName = $elementName; |
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$this->elements[$outputName] = $element; |
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} |
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// Add pattern or exact element |
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if (preg_match($hasPatternsRegExp ?? '', $elementName ?? '')) { |
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$element->pattern = $this->patternToRegex($elementName); |
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$this->elementPatterns[] = $element; |
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} else { |
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$this->elements[$elementName] = $element; |
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} |
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} |
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} |
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} |
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/** |
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* Given an element tag, return the rule structure for that element |
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* @param string $tag The element tag |
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* @return stdClass The element rule |
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*/ |
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protected function getRuleForElement($tag) |
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{ |
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if (isset($this->elements[$tag])) { |
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return $this->elements[$tag]; |
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} |
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foreach ($this->elementPatterns as $element) { |
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if (preg_match($element->pattern ?? '', $tag ?? '')) { |
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return $element; |
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} |
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} |
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return null; |
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} |
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/** |
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* Given an attribute name, return the rule structure for that attribute |
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* |
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* @param object $elementRule |
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* @param string $name The attribute name |
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* @return stdClass The attribute rule |
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*/ |
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protected function getRuleForAttribute($elementRule, $name) |
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{ |
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if (isset($elementRule->attributes[$name])) { |
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return $elementRule->attributes[$name]; |
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} |
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foreach ($elementRule->attributePatterns as $attribute) { |
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if (preg_match($attribute->pattern ?? '', $name ?? '')) { |
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return $attribute; |
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} |
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} |
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return null; |
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} |
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/** |
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* Given a DOMElement and an element rule, check if that element passes the rule |
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* @param DOMElement $element The element to check |
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* @param stdClass $rule The rule to check against |
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* @return bool True if the element passes (and so can be kept), false if it fails (and so needs stripping) |
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*/ |
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protected function elementMatchesRule($element, $rule = null) |
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{ |
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// If the rule doesn't exist at all, the element isn't allowed |
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if (!$rule) { |
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return false; |
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} |
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// If the rule has attributes required, check them to see if this element has at least one |
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if ($rule->attributesRequired) { |
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$hasMatch = false; |
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foreach ($rule->attributesRequired as $attr) { |
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if ($element->getAttribute($attr)) { |
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$hasMatch = true; |
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break; |
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} |
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} |
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if (!$hasMatch) { |
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return false; |
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} |
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} |
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// If the rule says to remove empty elements, and this element is empty, remove it |
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if ($rule->removeEmpty && !$element->firstChild) { |
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return false; |
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} |
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// No further tests required, element passes |
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return true; |
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} |
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/** |
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* Given a DOMAttr and an attribute rule, check if that attribute passes the rule |
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* @param DOMAttr $attr - the attribute to check |
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* @param stdClass $rule - the rule to check against |
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* @return bool - true if the attribute passes (and so can be kept), false if it fails (and so needs stripping) |
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*/ |
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protected function attributeMatchesRule($attr, $rule = null) |
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{ |
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// If the rule doesn't exist at all, the attribute isn't allowed |
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if (!$rule) { |
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return false; |
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} |
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// If the rule has a set of valid values, check them to see if this attribute is one |
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if (isset($rule->validValues) && !in_array($attr->value, $rule->validValues ?? [])) { |
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return false; |
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} |
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// No further tests required, attribute passes |
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return true; |
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} |
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/** |
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* Given an SS_HTMLValue instance, will remove and elements and attributes that are |
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* not explicitly included in the whitelist passed to __construct on instance creation |
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* |
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* @param HTMLValue $html - The HTMLValue to remove any non-whitelisted elements & attributes from |
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*/ |
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public function sanitise(HTMLValue $html) |
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{ |
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if (!$this->elements && !$this->elementPatterns) { |
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return; |
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} |
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$linkRelValue = $this->config()->get('link_rel_value'); |
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$doc = $html->getDocument(); |
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/** @var DOMElement $el */ |
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foreach ($html->query('//body//*') as $el) { |
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$elementRule = $this->getRuleForElement($el->tagName); |
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// If this element isn't allowed, strip it |
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if (!$this->elementMatchesRule($el, $elementRule)) { |
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// If it's a script or style, we don't keep contents |
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if ($el->tagName === 'script' || $el->tagName === 'style') { |
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$el->parentNode->removeChild($el); |
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} else { |
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// Otherwise we replace this node with all it's children |
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// First, create a new fragment with all of $el's children moved into it |
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$frag = $doc->createDocumentFragment(); |
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while ($el->firstChild) { |
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$frag->appendChild($el->firstChild); |
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} |
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// Then replace $el with the frags contents (which used to be it's children) |
|
315
|
|
|
$el->parentNode->replaceChild($frag, $el); |
|
316
|
|
|
} |
|
317
|
|
|
} else { |
|
318
|
|
|
// Otherwise tidy the element |
|
319
|
|
|
// First, if we're supposed to pad & this element is empty, fix that |
|
320
|
|
|
if ($elementRule->paddEmpty && !$el->firstChild) { |
|
321
|
|
|
$el->nodeValue = ' '; |
|
322
|
|
|
} |
|
323
|
|
|
|
|
324
|
|
|
// Then filter out any non-whitelisted attributes |
|
325
|
|
|
$children = $el->attributes; |
|
326
|
|
|
$i = $children->length; |
|
327
|
|
|
while ($i--) { |
|
328
|
|
|
$attr = $children->item($i); |
|
329
|
|
|
$attributeRule = $this->getRuleForAttribute($elementRule, $attr->name); |
|
330
|
|
|
|
|
331
|
|
|
// If this attribute isn't allowed, strip it |
|
332
|
|
|
if (!$this->attributeMatchesRule($attr, $attributeRule)) { |
|
333
|
|
|
$el->removeAttributeNode($attr); |
|
334
|
|
|
} |
|
335
|
|
|
} |
|
336
|
|
|
|
|
337
|
|
|
// Then enforce any default attributes |
|
338
|
|
|
foreach ($elementRule->attributesDefault as $attr => $default) { |
|
339
|
|
|
if (!$el->getAttribute($attr)) { |
|
340
|
|
|
$el->setAttribute($attr, $default); |
|
341
|
|
|
} |
|
342
|
|
|
} |
|
343
|
|
|
|
|
344
|
|
|
// And any forced attributes |
|
345
|
|
|
foreach ($elementRule->attributesForced as $attr => $forced) { |
|
346
|
|
|
$el->setAttribute($attr, $forced); |
|
347
|
|
|
} |
|
348
|
|
|
|
|
349
|
|
|
// Matches "javascript:" with any arbitrary linebreaks inbetween the characters. |
|
350
|
|
|
$regex = '/^\s*' . implode('\v*', str_split('javascript:')) . '/'; |
|
|
|
|
|
|
351
|
|
|
// Strip out javascript execution in href or src attributes. |
|
352
|
|
|
foreach (['src', 'href'] as $dangerAttribute) { |
|
353
|
|
|
if ($el->hasAttribute($dangerAttribute)) { |
|
354
|
|
|
if (preg_match($regex, $el->getAttribute($dangerAttribute))) { |
|
355
|
|
|
$el->removeAttribute($dangerAttribute); |
|
356
|
|
|
} |
|
357
|
|
|
} |
|
358
|
|
|
} |
|
359
|
|
|
} |
|
360
|
|
|
|
|
361
|
|
|
if ($el->tagName === 'a' && $linkRelValue !== null) { |
|
362
|
|
|
$this->addRelValue($el, $linkRelValue); |
|
363
|
|
|
} |
|
364
|
|
|
} |
|
365
|
|
|
} |
|
366
|
|
|
|
|
367
|
|
|
/** |
|
368
|
|
|
* Adds rel="noopener noreferrer" to link elements with a target attribute |
|
369
|
|
|
* |
|
370
|
|
|
* @param DOMElement $el |
|
371
|
|
|
* @param string|null $linkRelValue |
|
372
|
|
|
*/ |
|
373
|
|
|
private function addRelValue(DOMElement $el, $linkRelValue) |
|
374
|
|
|
{ |
|
375
|
|
|
// user has checked the checkbox 'open link in new window' |
|
376
|
|
|
if ($el->getAttribute('target') && $el->getAttribute('rel') !== $linkRelValue) { |
|
377
|
|
|
if ($linkRelValue !== '') { |
|
378
|
|
|
$el->setAttribute('rel', $linkRelValue); |
|
379
|
|
|
} else { |
|
380
|
|
|
$el->removeAttribute('rel'); |
|
381
|
|
|
} |
|
382
|
|
|
} elseif ($el->getAttribute('rel') === $linkRelValue && !$el->getAttribute('target')) { |
|
383
|
|
|
// user previously checked 'open link in new window' and noopener was added, |
|
384
|
|
|
// now user has unchecked the checkbox so we can remove noopener |
|
385
|
|
|
$el->removeAttribute('rel'); |
|
386
|
|
|
} |
|
387
|
|
|
} |
|
388
|
|
|
} |
|
389
|
|
|
|
silverstripe /
silverstripe-framework
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