159 lines
6.8 KiB
PHP
159 lines
6.8 KiB
PHP
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<?php
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/////////////////////////////////////////////////////////////////
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/// getID3() by James Heinrich <info@getid3.org> //
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// available at https://github.com/JamesHeinrich/getID3 //
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// or https://www.getid3.org //
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// or http://getid3.sourceforge.net //
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// see readme.txt for more details //
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/////////////////////////////////////////////////////////////////
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// //
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// module.misc.pdf.php //
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// module for analyzing PDF files //
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// dependencies: NONE //
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// ///
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/////////////////////////////////////////////////////////////////
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if (!defined('GETID3_INCLUDEPATH')) { // prevent path-exposing attacks that access modules directly on public webservers
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exit;
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}
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class getid3_pdf extends getid3_handler
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{
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/** misc.pdf
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* return full details of PDF Cross-Reference Table (XREF)
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*
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* @var bool
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*/
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public $returnXREF = false;
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/**
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* @return bool
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*/
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public function Analyze() {
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$info = &$this->getid3->info;
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$this->fseek(0);
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if (preg_match('#^%PDF-([0-9\\.]+)$#', rtrim($this->fgets()), $matches)) {
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$info['pdf']['header']['version'] = floatval($matches[1]);
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$info['fileformat'] = 'pdf';
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// the PDF Cross-Reference Table (XREF) is located near the end of the file
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// the starting offset is specified in the penultimate section, on the two lines just before "%%EOF"
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// the first line is "startxref", the second line is the byte offset of the XREF.
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// We know the length of "%%EOF" and "startxref", but the offset could be 2-10 bytes,
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// and we're not sure if the line ends are one or two bytes, so we might find "startxref" as little as 18(?) bytes
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// from EOF, but it could 30 bytes, so we start 40 bytes back just to be safe and do a search for the data we want.
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$this->fseek(-40, SEEK_END);
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if (preg_match('#[\r\n]startxref[ \r\n]+([0-9]+)[ \r\n]+#', $this->fread(40), $matches)) {
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$info['pdf']['trailer']['startxref'] = intval($matches[1]);
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$this->parseXREF($info['pdf']['trailer']['startxref']);
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if (!empty($info['pdf']['xref']['offset'])) {
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while (!$this->feof() && (max(array_keys($info['pdf']['xref']['offset'])) > $info['pdf']['xref']['count'])) {
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// suspect that there may be another XREF entry somewhere in the file, brute-force scan for it
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/*
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// starting at last known entry of main XREF table
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$this->fseek(max($info['pdf']['xref']['offset']));
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*/
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// starting at the beginning of the file
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$this->fseek(0);
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while (!$this->feof()) {
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$XREFoffset = $this->ftell();
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if (rtrim($this->fgets()) == 'xref') {
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if (empty($info['pdf']['xref']['xref_offsets']) || !in_array($XREFoffset, $info['pdf']['xref']['xref_offsets'])) {
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$this->parseXREF($XREFoffset);
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break;
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}
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}
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}
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}
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asort($info['pdf']['xref']['offset']);
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$maxObjLengths = array();
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$prevOffset = 0;
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$prevObjNum = 0;
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foreach ($info['pdf']['xref']['offset'] as $objectNumber => $offset) {
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// walk through all listed offsets to calculate the maximum possible length for each known object
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if ($prevObjNum) {
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$maxObjLengths[$prevObjNum] = $offset - $prevOffset;
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}
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$prevOffset = $offset;
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$prevObjNum = $objectNumber;
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}
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ksort($maxObjLengths);
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foreach ($info['pdf']['xref']['offset'] as $objectNumber => $offset) {
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if ($info['pdf']['xref']['entry'][$objectNumber] == 'f') {
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// "free" object means "deleted", ignore
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continue;
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}
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if (!empty($maxObjLengths[$objectNumber]) && ($maxObjLengths[$objectNumber] < $this->getid3->option_fread_buffer_size)) {
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// ignore object that are zero-size or >32kB, they are unlikely to contain information we're interested in
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$this->fseek($offset);
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$objBlob = $this->fread($maxObjLengths[$objectNumber]);
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if (preg_match('#^'.$objectNumber.'[\\x00 \\r\\n\\t]*([0-9]+)[\\x00 \\r\\n\\t]*obj[\\x00 \\r\\n\\t]*(.*)(endobj)?[\\x00 \\r\\n\\t]*$#s', $objBlob, $matches)) {
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list($dummy, $generation, $objectData) = $matches;
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if (preg_match('#^<<[\r\n\s]*(/Type|/Pages|/Parent [0-9]+ [0-9]+ [A-Z]|/Count [0-9]+|/Kids *\\[[0-9A-Z ]+\\]|[\r\n\s])+[\r\n\s]*>>#', $objectData, $matches)) {
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if (preg_match('#/Count ([0-9]+)#', $objectData, $matches)) {
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$info['pdf']['pages'] = (int) $matches[1];
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break; // for now this is the only data we're looking for in the PDF not need to loop through every object in the file (and a large PDF may contain MANY objects). And it MAY be possible that there are other objects elsewhere in the file that define additional (or removed?) pages
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}
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}
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} else {
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$this->error('Unexpected structure "'.substr($objBlob, 0, 100).'" at offset '.$offset);
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break;
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}
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}
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}
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if (!$this->returnXREF) {
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unset($info['pdf']['xref']['offset'], $info['pdf']['xref']['generation'], $info['pdf']['xref']['entry'], $info['pdf']['xref']['xref_offsets']);
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}
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} else {
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$this->error('Did not find "xref" at offset '.$info['pdf']['trailer']['startxref']);
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}
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} else {
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$this->error('Did not find "startxref" in the last 40 bytes of the PDF');
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}
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$this->warning('PDF parsing incomplete in this version of getID3() ['.$this->getid3->version().']');
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return true;
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}
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$this->error('Did not find "%PDF" at the beginning of the PDF');
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return false;
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}
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/**
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* @return bool
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*/
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private function parseXREF($XREFoffset) {
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$info = &$this->getid3->info;
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$this->fseek($XREFoffset);
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if (rtrim($this->fgets()) == 'xref') {
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$info['pdf']['xref']['xref_offsets'][$XREFoffset] = $XREFoffset;
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list($firstObjectNumber, $XREFcount) = explode(' ', rtrim($this->fgets()));
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$firstObjectNumber = (int) $firstObjectNumber;
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$XREFcount = (int) $XREFcount;
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$info['pdf']['xref']['count'] = $XREFcount + (!empty($info['pdf']['xref']['count']) ? $info['pdf']['xref']['count'] : 0);
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for ($i = 0; $i < $XREFcount; $i++) {
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$line = rtrim($this->fgets());
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if (preg_match('#^([0-9]+) ([0-9]+) ([nf])$#', $line, $matches)) {
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$info['pdf']['xref']['offset'][($firstObjectNumber + $i)] = (int) $matches[1];
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$info['pdf']['xref']['generation'][($firstObjectNumber + $i)] = (int) $matches[2];
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$info['pdf']['xref']['entry'][($firstObjectNumber + $i)] = $matches[3];
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} else {
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$this->error('failed to parse XREF entry #'.$i.' in XREF table at offset '.$XREFoffset);
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return false;
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}
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}
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sort($info['pdf']['xref']['xref_offsets']);
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return true;
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}
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$this->warning('failed to find expected XREF structure at offset '.$XREFoffset);
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return false;
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}
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}
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