Special case opus mime detction

[mediawiki.git] / includes / libs / mime / XmlTypeCheck.php

<?php
/**
 * XML syntax and type checker.
 *
 * Since 1.24.2, it uses XMLReader instead of xml_parse, which gives us
 * more control over the expansion of XML entities. When passed to the
 * callback, entities will be fully expanded, but may report the XML is
 * invalid if expanding the entities are likely to cause a DoS.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

class XmlTypeCheck {
        /**
         * Will be set to true or false to indicate whether the file is
         * well-formed XML. Note that this doesn't check schema validity.
         */
        public $wellFormed = null;

        /**
         * Will be set to true if the optional element filter returned
         * a match at some point.
         */
        public $filterMatch = false;

        /**
         * Will contain the type of filter hit if the optional element filter returned
         * a match at some point.
         * @var mixed
         */
        public $filterMatchType = false;

        /**
         * Name of the document's root element, including any namespace
         * as an expanded URL.
         */
        public $rootElement = '';

        /**
         * A stack of strings containing the data of each xml element as it's processed. Append
         * data to the top string of the stack, then pop off the string and process it when the
         * element is closed.
         */
        protected $elementData = [];

        /**
         * A stack of element names and attributes, as we process them.
         */
        protected $elementDataContext = [];

        /**
         * Current depth of the data stack.
         */
        protected $stackDepth = 0;

        /**
         * Additional parsing options
         */
        private $parserOptions = [
                'processing_instruction_handler' => '',
        ];

        /**
         * @param string $input a filename or string containing the XML element
         * @param callable $filterCallback (optional)
         *        Function to call to do additional custom validity checks from the
         *        SAX element handler event. This gives you access to the element
         *        namespace, name, attributes, and text contents.
         *        Filter should return 'true' to toggle on $this->filterMatch
         * @param bool $isFile (optional) indicates if the first parameter is a
         *        filename (default, true) or if it is a string (false)
         * @param array $options list of additional parsing options:
         *        processing_instruction_handler: Callback for xml_set_processing_instruction_handler
         */
        function __construct( $input, $filterCallback = null, $isFile = true, $options = [] ) {
                $this->filterCallback = $filterCallback;
                $this->parserOptions = array_merge( $this->parserOptions, $options );
                $this->validateFromInput( $input, $isFile );
        }

        /**
         * Alternative constructor: from filename
         *
         * @param string $fname the filename of an XML document
         * @param callable $filterCallback (optional)
         *        Function to call to do additional custom validity checks from the
         *        SAX element handler event. This gives you access to the element
         *        namespace, name, and attributes, but not to text contents.
         *        Filter should return 'true' to toggle on $this->filterMatch
         * @return XmlTypeCheck
         */
        public static function newFromFilename( $fname, $filterCallback = null ) {
                return new self( $fname, $filterCallback, true );
        }

        /**
         * Alternative constructor: from string
         *
         * @param string $string a string containing an XML element
         * @param callable $filterCallback (optional)
         *        Function to call to do additional custom validity checks from the
         *        SAX element handler event. This gives you access to the element
         *        namespace, name, and attributes, but not to text contents.
         *        Filter should return 'true' to toggle on $this->filterMatch
         * @return XmlTypeCheck
         */
        public static function newFromString( $string, $filterCallback = null ) {
                return new self( $string, $filterCallback, false );
        }

        /**
         * Get the root element. Simple accessor to $rootElement
         *
         * @return string
         */
        public function getRootElement() {
                return $this->rootElement;
        }

        /**
         * @param string $fname the filename
         */
        private function validateFromInput( $xml, $isFile ) {
                $reader = new XMLReader();
                if ( $isFile ) {
                        $s = $reader->open( $xml, null, LIBXML_NOERROR | LIBXML_NOWARNING );
                } else {
                        $s = $reader->XML( $xml, null, LIBXML_NOERROR | LIBXML_NOWARNING );
                }
                if ( $s !== true ) {
                        // Couldn't open the XML
                        $this->wellFormed = false;
                } else {
                        $oldDisable = libxml_disable_entity_loader( true );
                        $reader->setParserProperty( XMLReader::SUBST_ENTITIES, true );
                        try {
                                $this->validate( $reader );
                        } catch ( Exception $e ) {
                                // Calling this malformed, because we didn't parse the whole
                                // thing. Maybe just an external entity refernce.
                                $this->wellFormed = false;
                                $reader->close();
                                libxml_disable_entity_loader( $oldDisable );
                                throw $e;
                        }
                        $reader->close();
                        libxml_disable_entity_loader( $oldDisable );
                }
        }

        private function readNext( XMLReader $reader ) {
                set_error_handler( [ $this, 'XmlErrorHandler' ] );
                $ret = $reader->read();
                restore_error_handler();
                return $ret;
        }

        public function XmlErrorHandler( $errno, $errstr ) {
                $this->wellFormed = false;
        }

        private function validate( $reader ) {
                // First, move through anything that isn't an element, and
                // handle any processing instructions with the callback
                do {
                        if ( !$this->readNext( $reader ) ) {
                                // Hit the end of the document before any elements
                                $this->wellFormed = false;
                                return;
                        }
                        if ( $reader->nodeType === XMLReader::PI ) {
                                $this->processingInstructionHandler( $reader->name, $reader->value );
                        }
                } while ( $reader->nodeType != XMLReader::ELEMENT );

                // Process the rest of the document
                do {
                        switch ( $reader->nodeType ) {
                                case XMLReader::ELEMENT:
                                        $name = $this->expandNS(
                                                $reader->name,
                                                $reader->namespaceURI
                                        );
                                        if ( $this->rootElement === '' ) {
                                                $this->rootElement = $name;
                                        }
                                        $empty = $reader->isEmptyElement;
                                        $attrs = $this->getAttributesArray( $reader );
                                        $this->elementOpen( $name, $attrs );
                                        if ( $empty ) {
                                                $this->elementClose();
                                        }
                                        break;

                                case XMLReader::END_ELEMENT:
                                        $this->elementClose();
                                        break;

                                case XMLReader::WHITESPACE:
                                case XMLReader::SIGNIFICANT_WHITESPACE:
                                case XMLReader::CDATA:
                                case XMLReader::TEXT:
                                        $this->elementData( $reader->value );
                                        break;

                                case XMLReader::ENTITY_REF:
                                        // Unexpanded entity (maybe external?),
                                        // don't send to the filter (xml_parse didn't)
                                        break;

                                case XMLReader::COMMENT:
                                        // Don't send to the filter (xml_parse didn't)
                                        break;

                                case XMLReader::PI:
                                        // Processing instructions can happen after the header too
                                        $this->processingInstructionHandler(
                                                $reader->name,
                                                $reader->value
                                        );
                                        break;
                                default:
                                        // One of DOC, DOC_TYPE, ENTITY, END_ENTITY,
                                        // NOTATION, or XML_DECLARATION
                                        // xml_parse didn't send these to the filter, so we won't.
                        }
                } while ( $this->readNext( $reader ) );

                if ( $this->stackDepth !== 0 ) {
                        $this->wellFormed = false;
                } elseif ( $this->wellFormed === null ) {
                        $this->wellFormed = true;
                }
        }

        /**
         * Get all of the attributes for an XMLReader's current node
         * @param $r XMLReader
         * @return array of attributes
         */
        private function getAttributesArray( XMLReader $r ) {
                $attrs = [];
                while ( $r->moveToNextAttribute() ) {
                        if ( $r->namespaceURI === 'http://www.w3.org/2000/xmlns/' ) {
                                // XMLReader treats xmlns attributes as normal
                                // attributes, while xml_parse doesn't
                                continue;
                        }
                        $name = $this->expandNS( $r->name, $r->namespaceURI );
                        $attrs[$name] = $r->value;
                }
                return $attrs;
        }

        /**
         * @param $name element or attribute name, maybe with a full or short prefix
         * @param $namespaceURI the namespaceURI
         * @return string the name prefixed with namespaceURI
         */
        private function expandNS( $name, $namespaceURI ) {
                if ( $namespaceURI ) {
                        $parts = explode( ':', $name );
                        $localname = array_pop( $parts );
                        return "$namespaceURI:$localname";
                }
                return $name;
        }

        /**
         * @param $name
         * @param $attribs
         */
        private function elementOpen( $name, $attribs ) {
                $this->elementDataContext[] = [ $name, $attribs ];
                $this->elementData[] = '';
                $this->stackDepth++;
        }

        private function elementClose() {
                list( $name, $attribs ) = array_pop( $this->elementDataContext );
                $data = array_pop( $this->elementData );
                $this->stackDepth--;
                $callbackReturn = false;

                if ( is_callable( $this->filterCallback ) ) {
                        $callbackReturn = call_user_func(
                                $this->filterCallback,
                                $name,
                                $attribs,
                                $data
                        );
                }
                if ( $callbackReturn ) {
                        // Filter hit!
                        $this->filterMatch = true;
                        $this->filterMatchType = $callbackReturn;
                }
        }

        /**
         * @param $data
         */
        private function elementData( $data ) {
                // Collect any data here, and we'll run the callback in elementClose
                $this->elementData[ $this->stackDepth - 1 ] .= trim( $data );
        }

        /**
         * @param $target
         * @param $data
         */
        private function processingInstructionHandler( $target, $data ) {
                $callbackReturn = false;
                if ( $this->parserOptions['processing_instruction_handler'] ) {
                        $callbackReturn = call_user_func(
                                $this->parserOptions['processing_instruction_handler'],
                                $target,
                                $data
                        );
                }
                if ( $callbackReturn ) {
                        // Filter hit!
                        $this->filterMatch = true;
                        $this->filterMatchType = $callbackReturn;
                }
        }
}