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| 1 | <?php |
| 2 | /** |
| 3 | * This program is free software; you can redistribute it and/or modify |
| 4 | * it under the terms of the GNU General Public License as published by |
| 5 | * the Free Software Foundation; either version 2 of the License, or |
| 6 | * (at your option) any later version. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 16 | * http://www.gnu.org/copyleft/gpl.html |
| 17 | * |
| 18 | * @file |
| 19 | */ |
| 20 | |
| 21 | /** |
| 22 | * XML syntax and type checker. |
| 23 | * |
| 24 | * Since MediaWiki 1.24.2, this uses XMLReader instead of xml_parse, which gives us |
| 25 | * more control over the expansion of XML entities. When passed to the |
| 26 | * callback, entities will be fully expanded, but may report the XML is |
| 27 | * invalid if expanding the entities are likely to cause a DoS. |
| 28 | * |
| 29 | * @newable |
| 30 | * @since 1.12.0 |
| 31 | * @ingroup Mime |
| 32 | */ |
| 33 | class XmlTypeCheck { |
| 34 | /** |
| 35 | * @var bool|null Will be set to true or false to indicate whether the file is |
| 36 | * well-formed XML. Note that this doesn't check schema validity. |
| 37 | */ |
| 38 | public $wellFormed = null; |
| 39 | |
| 40 | /** |
| 41 | * @var bool Will be set to true if the optional element filter returned |
| 42 | * a match at some point. |
| 43 | */ |
| 44 | public $filterMatch = false; |
| 45 | |
| 46 | /** |
| 47 | * Will contain the type of filter hit if the optional element filter returned |
| 48 | * a match at some point. |
| 49 | * @var mixed |
| 50 | */ |
| 51 | public $filterMatchType = false; |
| 52 | |
| 53 | /** |
| 54 | * @var string Name of the document's root element, including any namespace |
| 55 | * as an expanded URL. |
| 56 | */ |
| 57 | public $rootElement = ''; |
| 58 | |
| 59 | /** |
| 60 | * @var string[] A stack of strings containing the data of each xml element as it's processed. |
| 61 | * Append data to the top string of the stack, then pop off the string and process it when the |
| 62 | * element is closed. |
| 63 | */ |
| 64 | protected $elementData = []; |
| 65 | |
| 66 | /** |
| 67 | * @var array A stack of element names and attributes, as we process them. |
| 68 | */ |
| 69 | protected $elementDataContext = []; |
| 70 | |
| 71 | /** |
| 72 | * @var int Current depth of the data stack. |
| 73 | */ |
| 74 | protected $stackDepth = 0; |
| 75 | |
| 76 | /** @var callable|null */ |
| 77 | protected $filterCallback; |
| 78 | |
| 79 | /** |
| 80 | * @var array Additional parsing options |
| 81 | */ |
| 82 | private $parserOptions = [ |
| 83 | 'processing_instruction_handler' => null, |
| 84 | 'external_dtd_handler' => '', |
| 85 | 'dtd_handler' => '', |
| 86 | 'require_safe_dtd' => true |
| 87 | ]; |
| 88 | |
| 89 | /** |
| 90 | * Allow filtering an XML file. |
| 91 | * |
| 92 | * Filters should return either true or a string to indicate something |
| 93 | * is wrong with the file. $this->filterMatch will store if the |
| 94 | * file failed validation (true = failed validation). |
| 95 | * $this->filterMatchType will contain the validation error. |
| 96 | * $this->wellFormed will contain whether the xml file is well-formed. |
| 97 | * |
| 98 | * @note If multiple filters are hit, only one of them will have the |
| 99 | * result stored in $this->filterMatchType. |
| 100 | * |
| 101 | * @param string $input a filename or string containing the XML element |
| 102 | * @param callable|null $filterCallback (optional) |
| 103 | * Function to call to do additional custom validity checks from the |
| 104 | * SAX element handler event. This gives you access to the element |
| 105 | * namespace, name, attributes, and text contents. |
| 106 | * Filter should return a truthy value describing the error. |
| 107 | * @param bool $isFile (optional) indicates if the first parameter is a |
| 108 | * filename (default, true) or if it is a string (false) |
| 109 | * @param array $options list of additional parsing options: |
| 110 | * processing_instruction_handler: Callback for xml_set_processing_instruction_handler |
| 111 | * external_dtd_handler: Callback for the url of external dtd subset |
| 112 | * dtd_handler: Callback given the full text of the <!DOCTYPE declaration. |
| 113 | * require_safe_dtd: Only allow non-recursive entities in internal dtd (default true) |
| 114 | */ |
| 115 | public function __construct( $input, $filterCallback = null, $isFile = true, $options = [] ) { |
| 116 | $this->filterCallback = $filterCallback; |
| 117 | $this->parserOptions = array_merge( $this->parserOptions, $options ); |
| 118 | $this->validateFromInput( $input, $isFile ); |
| 119 | } |
| 120 | |
| 121 | /** |
| 122 | * Alternative constructor: from filename |
| 123 | * |
| 124 | * @param string $fname the filename of an XML document |
| 125 | * @param callable|null $filterCallback (optional) |
| 126 | * Function to call to do additional custom validity checks from the |
| 127 | * SAX element handler event. This gives you access to the element |
| 128 | * namespace, name, and attributes, but not to text contents. |
| 129 | * Filter should return 'true' to toggle on $this->filterMatch |
| 130 | * @return XmlTypeCheck |
| 131 | */ |
| 132 | public static function newFromFilename( $fname, $filterCallback = null ) { |
| 133 | return new self( $fname, $filterCallback, true ); |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Alternative constructor: from string |
| 138 | * |
| 139 | * @param string $string a string containing an XML element |
| 140 | * @param callable|null $filterCallback (optional) |
| 141 | * Function to call to do additional custom validity checks from the |
| 142 | * SAX element handler event. This gives you access to the element |
| 143 | * namespace, name, and attributes, but not to text contents. |
| 144 | * Filter should return 'true' to toggle on $this->filterMatch |
| 145 | * @return XmlTypeCheck |
| 146 | */ |
| 147 | public static function newFromString( $string, $filterCallback = null ) { |
| 148 | return new self( $string, $filterCallback, false ); |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * Get the root element. Simple accessor to $rootElement |
| 153 | * |
| 154 | * @return string |
| 155 | */ |
| 156 | public function getRootElement() { |
| 157 | return $this->rootElement; |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * @param string $xml |
| 162 | * @param bool $isFile |
| 163 | */ |
| 164 | private function validateFromInput( $xml, $isFile ) { |
| 165 | $reader = new XMLReader(); |
| 166 | if ( $isFile ) { |
| 167 | $s = $reader->open( $xml, null, LIBXML_NOERROR | LIBXML_NOWARNING ); |
| 168 | } else { |
| 169 | $s = $reader->XML( $xml, null, LIBXML_NOERROR | LIBXML_NOWARNING ); |
| 170 | } |
| 171 | if ( $s !== true ) { |
| 172 | // Couldn't open the XML |
| 173 | $this->wellFormed = false; |
| 174 | } else { |
| 175 | // phpcs:ignore Generic.PHP.NoSilencedErrors -- suppress deprecation per T268847 |
| 176 | $oldDisable = @libxml_disable_entity_loader( true ); |
| 177 | $reader->setParserProperty( XMLReader::SUBST_ENTITIES, true ); |
| 178 | try { |
| 179 | $this->validate( $reader ); |
| 180 | } catch ( Exception $e ) { |
| 181 | // Calling this malformed, because we didn't parse the whole |
| 182 | // thing. Maybe just an external entity refernce. |
| 183 | $this->wellFormed = false; |
| 184 | $reader->close(); |
| 185 | // phpcs:ignore Generic.PHP.NoSilencedErrors |
| 186 | @libxml_disable_entity_loader( $oldDisable ); |
| 187 | throw $e; |
| 188 | } |
| 189 | $reader->close(); |
| 190 | // phpcs:ignore Generic.PHP.NoSilencedErrors |
| 191 | @libxml_disable_entity_loader( $oldDisable ); |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | private function readNext( XMLReader $reader ) { |
| 196 | set_error_handler( function ( $line, $file ) { |
| 197 | $this->wellFormed = false; |
| 198 | return true; |
| 199 | } ); |
| 200 | $ret = $reader->read(); |
| 201 | restore_error_handler(); |
| 202 | return $ret; |
| 203 | } |
| 204 | |
| 205 | private function validate( $reader ) { |
| 206 | // First, move through anything that isn't an element, and |
| 207 | // handle any processing instructions with the callback |
| 208 | do { |
| 209 | if ( !$this->readNext( $reader ) ) { |
| 210 | // Hit the end of the document before any elements |
| 211 | $this->wellFormed = false; |
| 212 | return; |
| 213 | } |
| 214 | if ( $reader->nodeType === XMLReader::PI ) { |
| 215 | $this->processingInstructionHandler( $reader->name, $reader->value ); |
| 216 | } |
| 217 | if ( $reader->nodeType === XMLReader::DOC_TYPE ) { |
| 218 | $this->dtdHandler( $reader ); |
| 219 | } |
| 220 | } while ( $reader->nodeType != XMLReader::ELEMENT ); |
| 221 | |
| 222 | // Process the rest of the document |
| 223 | do { |
| 224 | switch ( $reader->nodeType ) { |
| 225 | case XMLReader::ELEMENT: |
| 226 | $name = $this->expandNS( |
| 227 | $reader->name, |
| 228 | $reader->namespaceURI |
| 229 | ); |
| 230 | if ( $this->rootElement === '' ) { |
| 231 | $this->rootElement = $name; |
| 232 | } |
| 233 | $empty = $reader->isEmptyElement; |
| 234 | $attrs = $this->getAttributesArray( $reader ); |
| 235 | $this->elementOpen( $name, $attrs ); |
| 236 | if ( $empty ) { |
| 237 | $this->elementClose(); |
| 238 | } |
| 239 | break; |
| 240 | |
| 241 | case XMLReader::END_ELEMENT: |
| 242 | $this->elementClose(); |
| 243 | break; |
| 244 | |
| 245 | case XMLReader::WHITESPACE: |
| 246 | case XMLReader::SIGNIFICANT_WHITESPACE: |
| 247 | case XMLReader::CDATA: |
| 248 | case XMLReader::TEXT: |
| 249 | $this->elementData( $reader->value ); |
| 250 | break; |
| 251 | |
| 252 | case XMLReader::ENTITY_REF: |
| 253 | // Unexpanded entity (maybe external?), |
| 254 | // don't send to the filter (xml_parse didn't) |
| 255 | break; |
| 256 | |
| 257 | case XMLReader::COMMENT: |
| 258 | // Don't send to the filter (xml_parse didn't) |
| 259 | break; |
| 260 | |
| 261 | case XMLReader::PI: |
| 262 | // Processing instructions can happen after the header too |
| 263 | $this->processingInstructionHandler( |
| 264 | $reader->name, |
| 265 | $reader->value |
| 266 | ); |
| 267 | break; |
| 268 | case XMLReader::DOC_TYPE: |
| 269 | // We should never see a doctype after first |
| 270 | // element. |
| 271 | $this->wellFormed = false; |
| 272 | break; |
| 273 | default: |
| 274 | // One of DOC, ENTITY, END_ENTITY, |
| 275 | // NOTATION, or XML_DECLARATION |
| 276 | // xml_parse didn't send these to the filter, so we won't. |
| 277 | } |
| 278 | } while ( $this->readNext( $reader ) ); |
| 279 | |
| 280 | if ( $this->stackDepth !== 0 ) { |
| 281 | $this->wellFormed = false; |
| 282 | } elseif ( $this->wellFormed === null ) { |
| 283 | $this->wellFormed = true; |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | /** |
| 288 | * Get all of the attributes for an XMLReader's current node |
| 289 | * @param XMLReader $r |
| 290 | * @return array of attributes |
| 291 | */ |
| 292 | private function getAttributesArray( XMLReader $r ) { |
| 293 | $attrs = []; |
| 294 | while ( $r->moveToNextAttribute() ) { |
| 295 | if ( $r->namespaceURI === 'http://www.w3.org/2000/xmlns/' ) { |
| 296 | // XMLReader treats xmlns attributes as normal |
| 297 | // attributes, while xml_parse doesn't |
| 298 | continue; |
| 299 | } |
| 300 | $name = $this->expandNS( $r->name, $r->namespaceURI ); |
| 301 | $attrs[$name] = $r->value; |
| 302 | } |
| 303 | return $attrs; |
| 304 | } |
| 305 | |
| 306 | /** |
| 307 | * @param string $name element or attribute name, maybe with a full or short prefix |
| 308 | * @param string $namespaceURI |
| 309 | * @return string the name prefixed with namespaceURI |
| 310 | */ |
| 311 | private function expandNS( $name, $namespaceURI ) { |
| 312 | if ( $namespaceURI ) { |
| 313 | $parts = explode( ':', $name ); |
| 314 | $localname = array_pop( $parts ); |
| 315 | return "$namespaceURI:$localname"; |
| 316 | } |
| 317 | return $name; |
| 318 | } |
| 319 | |
| 320 | /** |
| 321 | * @param string $name |
| 322 | * @param array $attribs |
| 323 | */ |
| 324 | private function elementOpen( $name, $attribs ) { |
| 325 | $this->elementDataContext[] = [ $name, $attribs ]; |
| 326 | $this->elementData[] = ''; |
| 327 | $this->stackDepth++; |
| 328 | } |
| 329 | |
| 330 | private function elementClose() { |
| 331 | [ $name, $attribs ] = array_pop( $this->elementDataContext ); |
| 332 | $data = array_pop( $this->elementData ); |
| 333 | $this->stackDepth--; |
| 334 | $callbackReturn = false; |
| 335 | |
| 336 | if ( is_callable( $this->filterCallback ) ) { |
| 337 | $callbackReturn = ( $this->filterCallback )( $name, $attribs, $data ); |
| 338 | } |
| 339 | if ( $callbackReturn ) { |
| 340 | // Filter hit! |
| 341 | $this->filterMatch = true; |
| 342 | $this->filterMatchType = $callbackReturn; |
| 343 | } |
| 344 | } |
| 345 | |
| 346 | /** |
| 347 | * @param string $data |
| 348 | */ |
| 349 | private function elementData( $data ) { |
| 350 | // Collect any data here, and we'll run the callback in elementClose |
| 351 | $this->elementData[ $this->stackDepth - 1 ] .= trim( $data ); |
| 352 | } |
| 353 | |
| 354 | /** |
| 355 | * @param string $target |
| 356 | * @param string $data |
| 357 | */ |
| 358 | private function processingInstructionHandler( $target, $data ) { |
| 359 | $callbackReturn = false; |
| 360 | if ( $this->parserOptions['processing_instruction_handler'] ) { |
| 361 | // @phan-suppress-next-line PhanTypeInvalidCallable false positive |
| 362 | $callbackReturn = $this->parserOptions['processing_instruction_handler']( |
| 363 | $target, |
| 364 | $data |
| 365 | ); |
| 366 | } |
| 367 | if ( $callbackReturn ) { |
| 368 | // Filter hit! |
| 369 | $this->filterMatch = true; |
| 370 | $this->filterMatchType = $callbackReturn; |
| 371 | } |
| 372 | } |
| 373 | |
| 374 | /** |
| 375 | * Handle coming across a <!DOCTYPE declaration. |
| 376 | * |
| 377 | * @param XMLReader $reader Reader currently pointing at DOCTYPE node. |
| 378 | */ |
| 379 | private function dtdHandler( XMLReader $reader ) { |
| 380 | $externalCallback = $this->parserOptions['external_dtd_handler']; |
| 381 | $generalCallback = $this->parserOptions['dtd_handler']; |
| 382 | $checkIfSafe = $this->parserOptions['require_safe_dtd']; |
| 383 | if ( !$externalCallback && !$generalCallback && !$checkIfSafe ) { |
| 384 | return; |
| 385 | } |
| 386 | $dtd = $reader->readOuterXml(); |
| 387 | $callbackReturn = false; |
| 388 | |
| 389 | if ( $generalCallback ) { |
| 390 | $callbackReturn = $generalCallback( $dtd ); |
| 391 | } |
| 392 | if ( $callbackReturn ) { |
| 393 | // Filter hit! |
| 394 | $this->filterMatch = true; |
| 395 | $this->filterMatchType = $callbackReturn; |
| 396 | $callbackReturn = false; |
| 397 | } |
| 398 | |
| 399 | $parsedDTD = $this->parseDTD( $dtd ); |
| 400 | if ( $externalCallback && isset( $parsedDTD['type'] ) ) { |
| 401 | $callbackReturn = $externalCallback( |
| 402 | $parsedDTD['type'], |
| 403 | $parsedDTD['publicid'] ?? null, |
| 404 | $parsedDTD['systemid'] ?? null |
| 405 | ); |
| 406 | } |
| 407 | if ( $callbackReturn ) { |
| 408 | // Filter hit! |
| 409 | $this->filterMatch = true; |
| 410 | $this->filterMatchType = $callbackReturn; |
| 411 | } |
| 412 | |
| 413 | if ( $checkIfSafe && isset( $parsedDTD['internal'] ) && |
| 414 | !$this->checkDTDIsSafe( $parsedDTD['internal'] ) |
| 415 | ) { |
| 416 | $this->wellFormed = false; |
| 417 | } |
| 418 | } |
| 419 | |
| 420 | /** |
| 421 | * Check if the internal subset of the DTD is safe. |
| 422 | * |
| 423 | * We whitelist an extremely restricted subset of DTD features. |
| 424 | * |
| 425 | * Safe is defined as: |
| 426 | * * Only contains entity definitions (e.g. No <!ATLIST ) |
| 427 | * * Entity definitions are not "system" entities |
| 428 | * * Entity definitions are not "parameter" (i.e. %) entities |
| 429 | * * Entity definitions do not reference other entities except & |
| 430 | * and quotes. Entity aliases (where the entity contains only |
| 431 | * another entity are allowed) |
| 432 | * * Entity references aren't overly long (>255 bytes). |
| 433 | * * <!ATTLIST svg xmlns:xlink CDATA #FIXED "http://www.w3.org/1999/xlink"> |
| 434 | * allowed if matched exactly for compatibility with graphviz |
| 435 | * * Comments. |
| 436 | * |
| 437 | * @param string $internalSubset The internal subset of the DTD |
| 438 | * @return bool true if safe. |
| 439 | */ |
| 440 | private function checkDTDIsSafe( $internalSubset ) { |
| 441 | $res = preg_match( |
| 442 | '/^(?:\s*<!ENTITY\s+\S+\s+' . |
| 443 | '(?:"(?:&[^"%&;]{1,64};|(?:[^"%&]|&|"){0,255})"' . |
| 444 | '|\'(?:&[^\'%&;]{1,64};|(?:[^\'%&]|&|'){0,255})\')\s*>' . |
| 445 | '|\s*<!--(?:[^-]|-[^-])*-->' . |
| 446 | '|\s*<!ATTLIST svg xmlns:xlink CDATA #FIXED ' . |
| 447 | '"http:\/\/www.w3.org\/1999\/xlink">)*\s*$/', |
| 448 | $internalSubset |
| 449 | ); |
| 450 | |
| 451 | return (bool)$res; |
| 452 | } |
| 453 | |
| 454 | /** |
| 455 | * Parse DTD into parts. |
| 456 | * |
| 457 | * If there is an error parsing the dtd, sets wellFormed to false. |
| 458 | * |
| 459 | * @param string $dtd |
| 460 | * @return array Possibly containing keys publicid, systemid, type and internal. |
| 461 | */ |
| 462 | private function parseDTD( $dtd ) { |
| 463 | $m = []; |
| 464 | $res = preg_match( |
| 465 | '/^<!DOCTYPE\s*\S+\s*' . |
| 466 | '(?:(?P<typepublic>PUBLIC)\s*' . |
| 467 | '(?:"(?P<pubquote>[^"]*)"|\'(?P<pubapos>[^\']*)\')' . // public identifer |
| 468 | '\s*"(?P<pubsysquote>[^"]*)"|\'(?P<pubsysapos>[^\']*)\'' . // system identifier |
| 469 | '|(?P<typesystem>SYSTEM)\s*' . |
| 470 | '(?:"(?P<sysquote>[^"]*)"|\'(?P<sysapos>[^\']*)\')' . |
| 471 | ')?\s*' . |
| 472 | '(?:\[\s*(?P<internal>.*)\])?\s*>$/s', |
| 473 | $dtd, |
| 474 | $m |
| 475 | ); |
| 476 | if ( !$res ) { |
| 477 | $this->wellFormed = false; |
| 478 | return []; |
| 479 | } |
| 480 | $parsed = []; |
| 481 | foreach ( $m as $field => $value ) { |
| 482 | if ( $value === '' || is_numeric( $field ) ) { |
| 483 | continue; |
| 484 | } |
| 485 | switch ( $field ) { |
| 486 | case 'typepublic': |
| 487 | case 'typesystem': |
| 488 | $parsed['type'] = $value; |
| 489 | break; |
| 490 | case 'pubquote': |
| 491 | case 'pubapos': |
| 492 | $parsed['publicid'] = $value; |
| 493 | break; |
| 494 | case 'pubsysquote': |
| 495 | case 'pubsysapos': |
| 496 | case 'sysquote': |
| 497 | case 'sysapos': |
| 498 | $parsed['systemid'] = $value; |
| 499 | break; |
| 500 | case 'internal': |
| 501 | $parsed['internal'] = $value; |
| 502 | break; |
| 503 | } |
| 504 | } |
| 505 | return $parsed; |
| 506 | } |
| 507 | } |