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JpegMetadataExtractor.php
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1 <?php
24 use Wikimedia\AtEase\AtEase;
25 use Wikimedia\XMPReader\Reader as XMPReader;
26 
40  private const MAX_JPEG_SEGMENTS = 200;
41 
53  public static function segmentSplitter( $filename ) {
54  $showXMP = XMPReader::isSupported();
55 
56  $segmentCount = 0;
57 
58  $segments = [
59  'XMP_ext' => [],
60  'COM' => [],
61  'PSIR' => [],
62  ];
63 
64  if ( !$filename ) {
65  throw new MWException( "No filename specified for " . __METHOD__ );
66  }
67  if ( !file_exists( $filename ) || is_dir( $filename ) ) {
68  throw new MWException( "Invalid file $filename passed to " . __METHOD__ );
69  }
70 
71  $fh = fopen( $filename, "rb" );
72 
73  if ( !$fh ) {
74  throw new MWException( "Could not open file $filename" );
75  }
76 
77  $buffer = fread( $fh, 2 );
78  if ( $buffer !== "\xFF\xD8" ) {
79  throw new MWException( "Not a jpeg, no SOI" );
80  }
81  while ( !feof( $fh ) ) {
82  $buffer = fread( $fh, 1 );
83  $segmentCount++;
84  if ( $segmentCount > self::MAX_JPEG_SEGMENTS ) {
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  AtEase::suppressWarnings();
108  $com = $oldCom = iconv( 'windows-1252', 'UTF-8//IGNORE', $oldCom );
109  AtEase::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." );
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." );
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?!" );
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  } elseif ( in_array( $buffer, [
161  "\xC0", "\xC1", "\xC2", "\xC3", "\xC5", "\xC6", "\xC7",
162  "\xC9", "\xCA", "\xCB", "\xCD", "\xCE", "\xCF" ] )
163  ) {
164  // SOF0, SOF1, SOF2, ... (same list as getimagesize)
165  $temp = self::jpegExtractMarker( $fh );
166  $segments["SOF"] = wfUnpack( 'Cbits/nheight/nwidth/Ccomponents', $temp );
167  } else {
168  // segment we don't care about, so skip
169  $size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
170  if ( $size['int'] < 2 ) {
171  throw new MWException( "invalid marker size in jpeg" );
172  }
173  // Note it's possible to seek beyond end of file if truncated.
174  // fseek doesn't report a failure in this case.
175  fseek( $fh, $size['int'] - 2, SEEK_CUR );
176  }
177  }
178  // shouldn't get here.
179  throw new MWException( "Reached end of jpeg file unexpectedly" );
180  }
181 
188  private static function jpegExtractMarker( &$fh ) {
189  $size = wfUnpack( "nint", fread( $fh, 2 ), 2 );
190  if ( $size['int'] < 2 ) {
191  throw new MWException( "invalid marker size in jpeg" );
192  }
193  if ( $size['int'] === 2 ) {
194  // fread( ..., 0 ) generates a warning
195  return '';
196  }
197  $segment = fread( $fh, $size['int'] - 2 );
198  if ( strlen( $segment ) !== $size['int'] - 2 ) {
199  throw new MWException( "Segment shorter than expected" );
200  }
201 
202  return $segment;
203  }
204 
219  public static function doPSIR( $app13 ) {
220  if ( !$app13 ) {
221  throw new MWException( "No App13 segment given" );
222  }
223  // First compare hash with real thing
224  // 0x404 contains IPTC, 0x425 has hash
225  // This is used to determine if the iptc is newer than
226  // the xmp data, as xmp programs update the hash,
227  // where non-xmp programs don't.
228 
229  $offset = 14; // skip past PHOTOSHOP 3.0 identifier. should already be checked.
230  $appLen = strlen( $app13 );
231  $realHash = "";
232  $recordedHash = "";
233 
234  // the +12 is the length of an empty item.
235  while ( $offset + 12 <= $appLen ) {
236  $valid = true;
237  if ( substr( $app13, $offset, 4 ) !== '8BIM' ) {
238  // its supposed to be 8BIM
239  // but apparently sometimes isn't esp. in
240  // really old jpg's
241  $valid = false;
242  }
243  $offset += 4;
244  $id = substr( $app13, $offset, 2 );
245  // id is a 2 byte id number which identifies
246  // the piece of info this record contains.
247 
248  $offset += 2;
249 
250  // some record types can contain a name, which
251  // is a pascal string 0-padded to be an even
252  // number of bytes. Most times (and any time
253  // we care) this is empty, making it two null bytes.
254 
255  $lenName = ord( substr( $app13, $offset, 1 ) ) + 1;
256  // we never use the name so skip it. +1 for length byte
257  if ( $lenName % 2 == 1 ) {
258  $lenName++;
259  } // pad to even.
260  $offset += $lenName;
261 
262  // now length of data (unsigned long big endian)
263  $lenData = wfUnpack( 'Nlen', substr( $app13, $offset, 4 ), 4 );
264  // PHP can take issue with very large unsigned ints and make them negative.
265  // Which should never ever happen, as this has to be inside a segment
266  // which is limited to a 16 bit number.
267  if ( $lenData['len'] < 0 ) {
268  throw new MWException( "Too big PSIR (" . $lenData['len'] . ')' );
269  }
270 
271  $offset += 4; // 4bytes length field;
272 
273  // this should not happen, but check.
274  if ( $lenData['len'] + $offset > $appLen ) {
275  throw new MWException( "PSIR data too long. (item length=" . $lenData['len']
276  . "; offset=$offset; total length=$appLen)" );
277  }
278 
279  if ( $valid ) {
280  switch ( $id ) {
281  case "\x04\x04":
282  // IPTC block
283  $realHash = md5( substr( $app13, $offset, $lenData['len'] ), true );
284  break;
285  case "\x04\x25":
286  $recordedHash = substr( $app13, $offset, $lenData['len'] );
287  break;
288  }
289  }
290 
291  // if odd, add 1 to length to account for
292  // null pad byte.
293  if ( $lenData['len'] % 2 == 1 ) {
294  $lenData['len']++;
295  }
296  $offset += $lenData['len'];
297  }
298 
299  if ( !$realHash || !$recordedHash ) {
300  return 'iptc-no-hash';
301  } elseif ( $realHash === $recordedHash ) {
302  return 'iptc-good-hash';
303  } else { /*$realHash !== $recordedHash */
304  return 'iptc-bad-hash';
305  }
306  }
307 }
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
wfUnpack( $format, $data, $length=false)
Wrapper around php's unpack.
Class for reading jpegs and extracting metadata.
const MAX_JPEG_SEGMENTS
The max segment is a safety check.
static doPSIR( $app13)
This reads the photoshop image resource.
static segmentSplitter( $filename)
Function to extract metadata segments of interest from jpeg files based on GIFMetadataExtractor.
static jpegExtractMarker(&$fh)
Helper function for jpegSegmentSplitter.
MediaWiki exception.
Definition: MWException.php:31