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JpegMetadataExtractor.php
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1 <?php
24 use Wikimedia\XMPReader\Reader as XMPReader;
25 
35  const MAX_JPEG_SEGMENTS = 200;
36 
37  // the max segment is a sanity check.
38  // A jpeg file should never even remotely have
39  // that many segments. Your average file has about 10.
40 
52  static function segmentSplitter( $filename ) {
53  $showXMP = XMPReader::isSupported();
54 
55  $segmentCount = 0;
56 
57  $segments = [
58  'XMP_ext' => [],
59  'COM' => [],
60  'PSIR' => [],
61  ];
62 
63  if ( !$filename ) {
64  throw new MWException( "No filename specified for " . __METHOD__ );
65  }
66  if ( !file_exists( $filename ) || is_dir( $filename ) ) {
67  throw new MWException( "Invalid file $filename passed to " . __METHOD__ );
68  }
69 
70  $fh = fopen( $filename, "rb" );
71 
72  if ( !$fh ) {
73  throw new MWException( "Could not open file $filename" );
74  }
75 
76  $buffer = fread( $fh, 2 );
77  if ( $buffer !== "\xFF\xD8" ) {
78  throw new MWException( "Not a jpeg, no SOI" );
79  }
80  while ( !feof( $fh ) ) {
81  $buffer = fread( $fh, 1 );
82  $segmentCount++;
83  if ( $segmentCount > self::MAX_JPEG_SEGMENTS ) {
84  // this is just a sanity check
85  throw new MWException( 'Too many jpeg segments. Aborting' );
86  }
87  while ( $buffer !== "\xFF" && !feof( $fh ) ) {
88  // In theory JPEG files are not allowed to contain anything between the sections,
89  // but in practice they sometimes do. It's customary to ignore the garbage data.
90  $buffer = fread( $fh, 1 );
91  }
92 
93  $buffer = fread( $fh, 1 );
94  while ( $buffer === "\xFF" && !feof( $fh ) ) {
95  // Skip through any 0xFF padding bytes.
96  $buffer = fread( $fh, 1 );
97  }
98  if ( $buffer === "\xFE" ) {
99  // COM section -- file comment
100  // First see if valid utf-8,
101  // if not try to convert it to windows-1252.
102  $com = $oldCom = trim( self::jpegExtractMarker( $fh ) );
103  UtfNormal\Validator::quickIsNFCVerify( $com );
104  // turns $com to valid utf-8.
105  // thus if no change, its utf-8, otherwise its something else.
106  if ( $com !== $oldCom ) {
107  Wikimedia\suppressWarnings();
108  $com = $oldCom = iconv( 'windows-1252', 'UTF-8//IGNORE', $oldCom );
109  Wikimedia\restoreWarnings();
110  }
111  // Try it again, if its still not a valid string, then probably
112  // binary junk or some really weird encoding, so don't extract.
113  UtfNormal\Validator::quickIsNFCVerify( $com );
114  if ( $com === $oldCom ) {
115  $segments["COM"][] = $oldCom;
116  } else {
117  wfDebug( __METHOD__ . " Ignoring JPEG comment as is garbage.\n" );
118  }
119  } elseif ( $buffer === "\xE1" ) {
120  // APP1 section (Exif, XMP, and XMP extended)
121  // only extract if XMP is enabled.
122  $temp = self::jpegExtractMarker( $fh );
123  // check what type of app segment this is.
124  if ( substr( $temp, 0, 29 ) === "http://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
125  // use trim to remove trailing \0 chars
126  $segments["XMP"] = trim( substr( $temp, 29 ) );
127  } elseif ( substr( $temp, 0, 35 ) === "http://ns.adobe.com/xmp/extension/\x00" && $showXMP ) {
128  // use trim to remove trailing \0 chars
129  $segments["XMP_ext"][] = trim( substr( $temp, 35 ) );
130  } elseif ( substr( $temp, 0, 29 ) === "XMP\x00://ns.adobe.com/xap/1.0/\x00" && $showXMP ) {
131  // Some images (especially flickr images) seem to have this.
132  // I really have no idea what the deal is with them, but
133  // whatever...
134  // use trim to remove trailing \0 chars
135  $segments["XMP"] = trim( substr( $temp, 29 ) );
136  wfDebug( __METHOD__ . ' Found XMP section with wrong app identifier '
137  . "Using anyways.\n" );
138  } elseif ( substr( $temp, 0, 6 ) === "Exif\0\0" ) {
139  // Just need to find out what the byte order is.
140  // because php's exif plugin sucks...
141  // This is a II for little Endian, MM for big. Not a unicode BOM.
142  $byteOrderMarker = substr( $temp, 6, 2 );
143  if ( $byteOrderMarker === 'MM' ) {
144  $segments['byteOrder'] = 'BE';
145  } elseif ( $byteOrderMarker === 'II' ) {
146  $segments['byteOrder'] = 'LE';
147  } else {
148  wfDebug( __METHOD__ . " Invalid byte ordering?!\n" );
149  }
150  }
151  } elseif ( $buffer === "\xED" ) {
152  // APP13 - PSIR. IPTC and some photoshop stuff
153  $temp = self::jpegExtractMarker( $fh );
154  if ( substr( $temp, 0, 14 ) === "Photoshop 3.0\x00" ) {
155  $segments["PSIR"][] = $temp;
156  }
157  } elseif ( $buffer === "\xD9" || $buffer === "\xDA" ) {
158  // EOI - end of image or SOS - start of scan. either way we're past any interesting segments
159  return $segments;
160  } else {
161  // segment we don't care about, so skip
162  $size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
163  if ( $size['int'] < 2 ) {
164  throw new MWException( "invalid marker size in jpeg" );
165  }
166  // Note it's possible to seek beyond end of file if truncated.
167  // fseek doesn't report a failure in this case.
168  fseek( $fh, $size['int'] - 2, SEEK_CUR );
169  }
170  }
171  // shouldn't get here.
172  throw new MWException( "Reached end of jpeg file unexpectedly" );
173  }
174 
181  private static function jpegExtractMarker( &$fh ) {
182  $size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
183  if ( $size['int'] < 2 ) {
184  throw new MWException( "invalid marker size in jpeg" );
185  }
186  if ( $size['int'] === 2 ) {
187  // fread( ..., 0 ) generates a warning
188  return '';
189  }
190  $segment = fread( $fh, $size['int'] - 2 );
191  if ( strlen( $segment ) !== $size['int'] - 2 ) {
192  throw new MWException( "Segment shorter than expected" );
193  }
194 
195  return $segment;
196  }
197 
212  public static function doPSIR( $app13 ) {
213  if ( !$app13 ) {
214  throw new MWException( "No App13 segment given" );
215  }
216  // First compare hash with real thing
217  // 0x404 contains IPTC, 0x425 has hash
218  // This is used to determine if the iptc is newer than
219  // the xmp data, as xmp programs update the hash,
220  // where non-xmp programs don't.
221 
222  $offset = 14; // skip past PHOTOSHOP 3.0 identifier. should already be checked.
223  $appLen = strlen( $app13 );
224  $realHash = "";
225  $recordedHash = "";
226 
227  // the +12 is the length of an empty item.
228  while ( $offset + 12 <= $appLen ) {
229  $valid = true;
230  if ( substr( $app13, $offset, 4 ) !== '8BIM' ) {
231  // its supposed to be 8BIM
232  // but apparently sometimes isn't esp. in
233  // really old jpg's
234  $valid = false;
235  }
236  $offset += 4;
237  $id = substr( $app13, $offset, 2 );
238  // id is a 2 byte id number which identifies
239  // the piece of info this record contains.
240 
241  $offset += 2;
242 
243  // some record types can contain a name, which
244  // is a pascal string 0-padded to be an even
245  // number of bytes. Most times (and any time
246  // we care) this is empty, making it two null bytes.
247 
248  $lenName = ord( substr( $app13, $offset, 1 ) ) + 1;
249  // we never use the name so skip it. +1 for length byte
250  if ( $lenName % 2 == 1 ) {
251  $lenName++;
252  } // pad to even.
253  $offset += $lenName;
254 
255  // now length of data (unsigned long big endian)
256  $lenData = wfUnpack( 'Nlen', substr( $app13, $offset, 4 ), 4 );
257  // PHP can take issue with very large unsigned ints and make them negative.
258  // Which should never ever happen, as this has to be inside a segment
259  // which is limited to a 16 bit number.
260  if ( $lenData['len'] < 0 ) {
261  throw new MWException( "Too big PSIR (" . $lenData['len'] . ')' );
262  }
263 
264  $offset += 4; // 4bytes length field;
265 
266  // this should not happen, but check.
267  if ( $lenData['len'] + $offset > $appLen ) {
268  throw new MWException( "PSIR data too long. (item length=" . $lenData['len']
269  . "; offset=$offset; total length=$appLen)" );
270  }
271 
272  if ( $valid ) {
273  switch ( $id ) {
274  case "\x04\x04":
275  // IPTC block
276  $realHash = md5( substr( $app13, $offset, $lenData['len'] ), true );
277  break;
278  case "\x04\x25":
279  $recordedHash = substr( $app13, $offset, $lenData['len'] );
280  break;
281  }
282  }
283 
284  // if odd, add 1 to length to account for
285  // null pad byte.
286  if ( $lenData['len'] % 2 == 1 ) {
287  $lenData['len']++;
288  }
289  $offset += $lenData['len'];
290  }
291 
292  if ( !$realHash || !$recordedHash ) {
293  return 'iptc-no-hash';
294  } elseif ( $realHash === $recordedHash ) {
295  return 'iptc-good-hash';
296  } else { /*$realHash !== $recordedHash */
297  return 'iptc-bad-hash';
298  }
299  }
300 }
static jpegExtractMarker(&$fh)
Helper function for jpegSegmentSplitter.
static segmentSplitter( $filename)
Function to extract metadata segments of interest from jpeg files based on GIFMetadataExtractor.
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
static doPSIR( $app13)
This reads the photoshop image resource.
Class for reading jpegs and extracting metadata.
wfUnpack( $format, $data, $length=false)
Wrapper around php&#39;s unpack.