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SVGReader.php
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1 <?php
31 class SVGReader {
32  const DEFAULT_WIDTH = 512;
33  const DEFAULT_HEIGHT = 512;
34  const NS_SVG = 'http://www.w3.org/2000/svg';
35  const LANG_PREFIX_MATCH = 1;
36  const LANG_FULL_MATCH = 2;
37 
39  private $reader = null;
40 
42  private $mDebug = false;
43 
45  private $metadata = [];
46  private $languages = [];
47  private $languagePrefixes = [];
48 
54  function __construct( $source ) {
55  global $wgSVGMetadataCutoff;
56  $this->reader = new XMLReader();
57 
58  // Don't use $file->getSize() since file object passed to SVGHandler::getMetadata is bogus.
59  $size = filesize( $source );
60  if ( $size === false ) {
61  throw new MWException( "Error getting filesize of SVG." );
62  }
63 
64  if ( $size > $wgSVGMetadataCutoff ) {
65  $this->debug( "SVG is $size bytes, which is bigger than $wgSVGMetadataCutoff. Truncating." );
66  $contents = file_get_contents( $source, false, null, 0, $wgSVGMetadataCutoff );
67  if ( $contents === false ) {
68  throw new MWException( 'Error reading SVG file.' );
69  }
70  $this->reader->XML( $contents, null, LIBXML_NOERROR | LIBXML_NOWARNING );
71  } else {
72  $this->reader->open( $source, null, LIBXML_NOERROR | LIBXML_NOWARNING );
73  }
74 
75  // Expand entities, since Adobe Illustrator uses them for xmlns
76  // attributes (T33719). Note that libxml2 has some protection
77  // against large recursive entity expansions so this is not as
78  // insecure as it might appear to be. However, it is still extremely
79  // insecure. It's necessary to wrap any read() calls with
80  // libxml_disable_entity_loader() to avoid arbitrary local file
81  // inclusion, or even arbitrary code execution if the expect
82  // extension is installed (T48859).
83  $oldDisable = libxml_disable_entity_loader( true );
84  $this->reader->setParserProperty( XMLReader::SUBST_ENTITIES, true );
85 
86  $this->metadata['width'] = self::DEFAULT_WIDTH;
87  $this->metadata['height'] = self::DEFAULT_HEIGHT;
88 
89  // The size in the units specified by the SVG file
90  // (for the metadata box)
91  // Per the SVG spec, if unspecified, default to '100%'
92  $this->metadata['originalWidth'] = '100%';
93  $this->metadata['originalHeight'] = '100%';
94 
95  // Because we cut off the end of the svg making an invalid one. Complicated
96  // try catch thing to make sure warnings get restored. Seems like there should
97  // be a better way.
98  Wikimedia\suppressWarnings();
99  try {
100  $this->read();
101  } catch ( Exception $e ) {
102  // Note, if this happens, the width/height will be taken to be 0x0.
103  // Should we consider it the default 512x512 instead?
104  Wikimedia\restoreWarnings();
105  libxml_disable_entity_loader( $oldDisable );
106  throw $e;
107  }
108  Wikimedia\restoreWarnings();
109  libxml_disable_entity_loader( $oldDisable );
110  }
111 
115  public function getMetadata() {
116  return $this->metadata;
117  }
118 
124  protected function read() {
125  $keepReading = $this->reader->read();
126 
127  /* Skip until first element */
128  while ( $keepReading && $this->reader->nodeType != XMLReader::ELEMENT ) {
129  $keepReading = $this->reader->read();
130  }
131 
132  if ( $this->reader->localName != 'svg' || $this->reader->namespaceURI != self::NS_SVG ) {
133  throw new MWException( "Expected <svg> tag, got " .
134  $this->reader->localName . " in NS " . $this->reader->namespaceURI );
135  }
136  $this->debug( "<svg> tag is correct." );
137  $this->handleSVGAttribs();
138 
139  $exitDepth = $this->reader->depth;
140  $keepReading = $this->reader->read();
141  while ( $keepReading ) {
142  $tag = $this->reader->localName;
143  $type = $this->reader->nodeType;
144  $isSVG = ( $this->reader->namespaceURI == self::NS_SVG );
145 
146  $this->debug( "$tag" );
147 
148  if ( $isSVG && $tag == 'svg' && $type == XMLReader::END_ELEMENT
149  && $this->reader->depth <= $exitDepth
150  ) {
151  break;
152  } elseif ( $isSVG && $tag == 'title' ) {
153  $this->readField( $tag, 'title' );
154  } elseif ( $isSVG && $tag == 'desc' ) {
155  $this->readField( $tag, 'description' );
156  } elseif ( $isSVG && $tag == 'metadata' && $type == XMLReader::ELEMENT ) {
157  $this->readXml( 'metadata' );
158  } elseif ( $isSVG && $tag == 'script' ) {
159  // We normally do not allow scripted svgs.
160  // However its possible to configure MW to let them
161  // in, and such files should be considered animated.
162  $this->metadata['animated'] = true;
163  } elseif ( $tag !== '#text' ) {
164  $this->debug( "Unhandled top-level XML tag $tag" );
165 
166  // Recurse into children of current tag, looking for animation and languages.
167  $this->animateFilterAndLang( $tag );
168  }
169 
170  // Goto next element, which is sibling of current (Skip children).
171  $keepReading = $this->reader->next();
172  }
173 
174  $this->reader->close();
175 
176  $this->metadata['translations'] = $this->languages + $this->languagePrefixes;
177 
178  return true;
179  }
180 
187  private function readField( $name, $metafield = null ) {
188  $this->debug( "Read field $metafield" );
189  if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) {
190  return;
191  }
192  $keepReading = $this->reader->read();
193  while ( $keepReading ) {
194  if ( $this->reader->localName == $name
195  && $this->reader->namespaceURI == self::NS_SVG
196  && $this->reader->nodeType == XMLReader::END_ELEMENT
197  ) {
198  break;
199  } elseif ( $this->reader->nodeType == XMLReader::TEXT ) {
200  $this->metadata[$metafield] = trim( $this->reader->value );
201  }
202  $keepReading = $this->reader->read();
203  }
204  }
205 
212  private function readXml( $metafield = null ) {
213  $this->debug( "Read top level metadata" );
214  if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) {
215  return;
216  }
217  // @todo Find and store type of xml snippet. metadata['metadataType'] = "rdf"
218  $this->metadata[$metafield] = trim( $this->reader->readInnerXml() );
219 
220  $this->reader->next();
221  }
222 
229  private function animateFilterAndLang( $name ) {
230  $this->debug( "animate filter for tag $name" );
231  if ( $this->reader->nodeType != XMLReader::ELEMENT ) {
232  return;
233  }
234  if ( $this->reader->isEmptyElement ) {
235  return;
236  }
237  $exitDepth = $this->reader->depth;
238  $keepReading = $this->reader->read();
239  while ( $keepReading ) {
240  if ( $this->reader->localName == $name && $this->reader->depth <= $exitDepth
241  && $this->reader->nodeType == XMLReader::END_ELEMENT
242  ) {
243  break;
244  } elseif ( $this->reader->namespaceURI == self::NS_SVG
245  && $this->reader->nodeType == XMLReader::ELEMENT
246  ) {
247  $sysLang = $this->reader->getAttribute( 'systemLanguage' );
248  if ( !is_null( $sysLang ) && $sysLang !== '' ) {
249  // See https://www.w3.org/TR/SVG/struct.html#SystemLanguageAttribute
250  $langList = explode( ',', $sysLang );
251  foreach ( $langList as $langItem ) {
252  $langItem = trim( $langItem );
253  if ( Language::isWellFormedLanguageTag( $langItem ) ) {
254  $this->languages[$langItem] = self::LANG_FULL_MATCH;
255  }
256  // Note, the standard says that any prefix should work,
257  // here we do only the initial prefix, since that will catch
258  // 99% of cases, and we are going to compare against fallbacks.
259  // This differs mildly from how the spec says languages should be
260  // handled, however it matches better how the MediaWiki language
261  // preference is generally handled.
262  $dash = strpos( $langItem, '-' );
263  // Intentionally checking both !false and > 0 at the same time.
264  if ( $dash ) {
265  $itemPrefix = substr( $langItem, 0, $dash );
266  if ( Language::isWellFormedLanguageTag( $itemPrefix ) ) {
267  $this->languagePrefixes[$itemPrefix] = self::LANG_PREFIX_MATCH;
268  }
269  }
270  }
271  }
272  switch ( $this->reader->localName ) {
273  case 'script':
274  // Normally we disallow files with
275  // <script>, but its possible
276  // to configure MW to disable
277  // such checks.
278  case 'animate':
279  case 'set':
280  case 'animateMotion':
281  case 'animateColor':
282  case 'animateTransform':
283  $this->debug( "HOUSTON WE HAVE ANIMATION" );
284  $this->metadata['animated'] = true;
285  break;
286  }
287  }
288  $keepReading = $this->reader->read();
289  }
290  }
291 
292  private function debug( $data ) {
293  if ( $this->mDebug ) {
294  wfDebug( "SVGReader: $data\n" );
295  }
296  }
297 
303  private function handleSVGAttribs() {
304  $defaultWidth = self::DEFAULT_WIDTH;
305  $defaultHeight = self::DEFAULT_HEIGHT;
306  $aspect = 1.0;
307  $width = null;
308  $height = null;
309 
310  if ( $this->reader->getAttribute( 'viewBox' ) ) {
311  // min-x min-y width height
312  $viewBox = preg_split( '/\s*[\s,]\s*/', trim( $this->reader->getAttribute( 'viewBox' ) ) );
313  if ( count( $viewBox ) == 4 ) {
314  $viewWidth = $this->scaleSVGUnit( $viewBox[2] );
315  $viewHeight = $this->scaleSVGUnit( $viewBox[3] );
316  if ( $viewWidth > 0 && $viewHeight > 0 ) {
317  $aspect = $viewWidth / $viewHeight;
318  $defaultHeight = $defaultWidth / $aspect;
319  }
320  }
321  }
322  if ( $this->reader->getAttribute( 'width' ) ) {
323  $width = $this->scaleSVGUnit( $this->reader->getAttribute( 'width' ), $defaultWidth );
324  $this->metadata['originalWidth'] = $this->reader->getAttribute( 'width' );
325  }
326  if ( $this->reader->getAttribute( 'height' ) ) {
327  $height = $this->scaleSVGUnit( $this->reader->getAttribute( 'height' ), $defaultHeight );
328  $this->metadata['originalHeight'] = $this->reader->getAttribute( 'height' );
329  }
330 
331  if ( !isset( $width ) && !isset( $height ) ) {
332  $width = $defaultWidth;
333  $height = $width / $aspect;
334  } elseif ( isset( $width ) && !isset( $height ) ) {
335  $height = $width / $aspect;
336  } elseif ( isset( $height ) && !isset( $width ) ) {
337  $width = $height * $aspect;
338  }
339 
340  if ( $width > 0 && $height > 0 ) {
341  $this->metadata['width'] = intval( round( $width ) );
342  $this->metadata['height'] = intval( round( $height ) );
343  }
344  }
345 
354  static function scaleSVGUnit( $length, $viewportSize = 512 ) {
355  static $unitLength = [
356  'px' => 1.0,
357  'pt' => 1.25,
358  'pc' => 15.0,
359  'mm' => 3.543307,
360  'cm' => 35.43307,
361  'in' => 90.0,
362  'em' => 16.0, // fake it?
363  'ex' => 12.0, // fake it?
364  '' => 1.0, // "User units" pixels by default
365  ];
366  $matches = [];
367  if ( preg_match(
368  '/^\s*([-+]?\d*(?:\.\d+|\d+)(?:[Ee][-+]?\d+)?)\s*(em|ex|px|pt|pc|cm|mm|in|%|)\s*$/',
369  $length,
370  $matches
371  ) ) {
372  $length = floatval( $matches[1] );
373  $unit = $matches[2];
374  if ( $unit == '%' ) {
375  return $length * 0.01 * $viewportSize;
376  } else {
377  return $length * $unitLength[$unit];
378  }
379  } else {
380  // Assume pixels
381  return floatval( $length );
382  }
383  }
384 }
const NS_SVG
Definition: SVGReader.php:34
__construct( $source)
Creates an SVGReader drawing from the source provided.
Definition: SVGReader.php:54
readField( $name, $metafield=null)
Read a textelement from an element.
Definition: SVGReader.php:187
$wgSVGMetadataCutoff
Don&#39;t read SVG metadata beyond this point.
animateFilterAndLang( $name)
Filter all children, looking for animated elements.
Definition: SVGReader.php:229
div flags Integer display flags(NO_ACTION_LINK, NO_EXTRA_USER_LINKS) 'LogException' returning false will NOT prevent logging $e
Definition: hooks.txt:2146
bool $mDebug
Definition: SVGReader.php:42
const LANG_PREFIX_MATCH
Definition: SVGReader.php:35
handleSVGAttribs()
Parse the attributes of an SVG element.
Definition: SVGReader.php:303
$languagePrefixes
Definition: SVGReader.php:47
$source
array $metadata
Definition: SVGReader.php:45
static scaleSVGUnit( $length, $viewportSize=512)
Return a rounded pixel equivalent for a labeled CSS/SVG length.
Definition: SVGReader.php:354
null XMLReader $reader
Definition: SVGReader.php:39
const LANG_FULL_MATCH
Definition: SVGReader.php:36
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
const DEFAULT_HEIGHT
Definition: SVGReader.php:33
this hook is for auditing only or null if authentication failed before getting that far or null if we can t even determine that When $user is not null
Definition: hooks.txt:767
This document is intended to provide useful advice for parties seeking to redistribute MediaWiki to end users It s targeted particularly at maintainers for Linux since it s been observed that distribution packages of MediaWiki often break We ve consistently had to recommend that users seeking support use official tarballs instead of their distribution s and this often solves whatever problem the user is having It would be nice if this could such as
Definition: distributors.txt:9
static isWellFormedLanguageTag( $code, $lenient=false)
Returns true if a language code string is a well-formed language tag according to RFC 5646...
Definition: Language.php:334
injection txt This is an overview of how MediaWiki makes use of dependency injection The design described here grew from the discussion of RFC T384 The term dependency this means that anything an object needs to operate should be injected from the the object itself should only know narrow no concrete implementation of the logic it relies on The requirement to inject everything typically results in an architecture that based on two main types of and essentially stateless service objects that use other service objects to operate on the value objects As of the beginning MediaWiki is only starting to use the DI approach Much of the code still relies on global state or direct resulting in a highly cyclical dependency which acts as the top level factory for services in MediaWiki which can be used to gain access to default instances of various services MediaWikiServices however also allows new services to be defined and default services to be redefined Services are defined or redefined by providing a callback the instantiator that will return a new instance of the service When it will create an instance of MediaWikiServices and populate it with the services defined in the files listed by thereby bootstrapping the DI framework Per $wgServiceWiringFiles lists includes ServiceWiring php
Definition: injection.txt:35
readXml( $metafield=null)
Read an XML snippet from an element.
Definition: SVGReader.php:212
Allows to change the fields on the form that will be generated $name
Definition: hooks.txt:271
debug( $data)
Definition: SVGReader.php:292
read()
Read the SVG.
Definition: SVGReader.php:124
const DEFAULT_WIDTH
Definition: SVGReader.php:32
$matches