MediaWiki  master
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
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
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:270
readXml( $metafield=null)
Read an XML snippet from an element.
Definition: SVGReader.php:212
debug( $data)
Definition: SVGReader.php:292
read()
Read the SVG.
Definition: SVGReader.php:124
const DEFAULT_WIDTH
Definition: SVGReader.php:32
$matches