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<?php |
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namespace PhpOffice\PhpSpreadsheet\Reader\Security; |
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use PhpOffice\PhpSpreadsheet\Reader; |
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class XmlScanner |
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{ |
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/** |
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* Identifies whether the thread-safe libxmlDisableEntityLoader() function is available. |
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* |
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* @var bool |
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*/ |
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private $libxmlDisableEntityLoader = false; |
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/** |
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* Store the initial setting of libxmlDisableEntityLoader so that we can resore t later. |
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* |
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* @var bool |
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*/ |
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private $previousLibxmlDisableEntityLoaderValue; |
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/** |
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* String used to identify risky xml elements. |
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* |
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* @var string |
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*/ |
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private $pattern; |
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private $callback; |
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private function __construct($pattern = '<!DOCTYPE') |
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{ |
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$this->pattern = $pattern; |
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$this->libxmlDisableEntityLoader = $this->identifyLibxmlDisableEntityLoaderAvailability(); |
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if ($this->libxmlDisableEntityLoader) { |
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$this->previousLibxmlDisableEntityLoaderValue = libxml_disable_entity_loader(true); |
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} |
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} |
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public function __destruct() |
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{ |
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if ($this->libxmlDisableEntityLoader) { |
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libxml_disable_entity_loader($this->previousLibxmlDisableEntityLoaderValue); |
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} |
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} |
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public static function getInstance(Reader\IReader $reader) |
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{ |
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switch (true) { |
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case $reader instanceof Reader\Html: |
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return new self('<!ENTITY'); |
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case $reader instanceof Reader\Xlsx: |
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case $reader instanceof Reader\Xml: |
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case $reader instanceof Reader\Ods: |
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case $reader instanceof Reader\Gnumeric: |
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return new self('<!DOCTYPE'); |
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default: |
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return new self('<!DOCTYPE'); |
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} |
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} |
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private function identifyLibxmlDisableEntityLoaderAvailability() |
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{ |
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if (PHP_MAJOR_VERSION == 7) { |
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switch (PHP_MINOR_VERSION) { |
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case 2: |
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return PHP_RELEASE_VERSION >= 1; |
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case 1: |
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return PHP_RELEASE_VERSION >= 13; |
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case 0: |
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return PHP_RELEASE_VERSION >= 27; |
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} |
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return true; |
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} |
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return false; |
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} |
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public function setAdditionalCallback(callable $callback) |
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{ |
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$this->callback = $callback; |
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} |
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/** |
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* Scan the XML for use of <!ENTITY to prevent XXE/XEE attacks. |
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* |
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* @param mixed $xml |
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* |
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* @throws Reader\Exception |
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* |
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* @return string |
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*/ |
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public function scan($xml) |
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{ |
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$pattern = '/encoding="(.*?)"/'; |
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$result = preg_match($pattern, $xml, $matches); |
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$charset = $result ? $matches[1] : 'UTF-8'; |
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if ($charset !== 'UTF-8') { |
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$xml = mb_convert_encoding($xml, 'UTF-8', $charset); |
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} |
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// Don't rely purely on libxml_disable_entity_loader() |
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$pattern = '/\\0?' . implode('\\0?', str_split($this->pattern)) . '\\0?/'; |
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if (preg_match($pattern, $xml)) { |
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throw new Reader\Exception('Detected use of ENTITY in XML, spreadsheet file load() aborted to prevent XXE/XEE attacks'); |
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} |
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if ($this->callback !== null && is_callable($this->callback)) { |
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$xml = call_user_func($this->callback, $xml); |
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} |
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return $xml; |
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} |
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/** |
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* Scan theXML for use of <!ENTITY to prevent XXE/XEE attacks. |
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* |
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* @param string $filestream |
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* |
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* @throws Reader\Exception |
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* |
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* @return string |
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*/ |
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public function scanFile($filestream) |
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{ |
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return $this->scan(file_get_contents($filestream)); |
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} |
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} |
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PHPOffice /
PhpSpreadsheet
