X-Git-Url: https://scripts.mit.edu/gitweb/autoinstalls/mediawiki.git/blobdiff_plain/005c63129390e462618d69b42e7fd90eb81f8b9e..HEAD:/includes/media/GIFMetadataExtractor.php

diff --git a/includes/media/GIFMetadataExtractor.php b/includes/media/GIFMetadataExtractor.php
index fac9012b..ac5fc81c 100644
--- a/includes/media/GIFMetadataExtractor.php
+++ b/includes/media/GIFMetadataExtractor.php
@@ -1,175 +1,347 @@
 <?php
 /**
-  * GIF frame counter.
-  * Originally written in Perl by Steve Sanbeg.
-  * Ported to PHP by Andrew Garrett
-  * Deliberately not using MWExceptions to avoid external dependencies, encouraging
-  * redistribution.
-  */
+ * GIF frame counter.
+ *
+ * Originally written in Perl by Steve Sanbeg.
+ * Ported to PHP by Andrew Garrett
+ * Deliberately not using MWExceptions to avoid external dependencies, encouraging
+ * redistribution.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Media
+ */
 
+/**
+ * GIF frame counter.
+ *
+ * @ingroup Media
+ */
 class GIFMetadataExtractor {
-	static $gif_frame_sep;
-	static $gif_extension_sep;
-	static $gif_term;
+	/** @var string */
+	private static $gifFrameSep;
+
+	/** @var string */
+	private static $gifExtensionSep;
+
+	/** @var string */
+	private static $gifTerm;
+
+	const VERSION = 1;
+
+	// Each sub-block is less than or equal to 255 bytes.
+	// Most of the time its 255 bytes, except for in XMP
+	// blocks, where it's usually between 32-127 bytes each.
+	const MAX_SUBBLOCKS = 262144; // 5mb divided by 20.
 
+	/**
+	 * @throws Exception
+	 * @param string $filename
+	 * @return array
+	 */
 	static function getMetadata( $filename ) {
-		self::$gif_frame_sep = pack( "C", ord("," ) );
-		self::$gif_extension_sep = pack( "C", ord("!" ) );
-		self::$gif_term = pack( "C", ord(";" ) );
-		
+		self::$gifFrameSep = pack( "C", ord( "," ) ); // 2C
+		self::$gifExtensionSep = pack( "C", ord( "!" ) ); // 21
+		self::$gifTerm = pack( "C", ord( ";" ) ); // 3B
+
 		$frameCount = 0;
 		$duration = 0.0;
 		$isLooped = false;
-		
-		if (!$filename)
+		$xmp = "";
+		$comment = [];
+
+		if ( !$filename ) {
 			throw new Exception( "No file name specified" );
-		elseif ( !file_exists($filename) || is_dir($filename) )
+		} elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
 			throw new Exception( "File $filename does not exist" );
-		
-		$fh = fopen( $filename, 'r' );
-		
-		if (!$fh)
+		}
+
+		$fh = fopen( $filename, 'rb' );
+
+		if ( !$fh ) {
 			throw new Exception( "Unable to open file $filename" );
-		
+		}
+
 		// Check for the GIF header
 		$buf = fread( $fh, 6 );
-		if ( !($buf == 'GIF87a' || $buf == 'GIF89a') ) {
+		if ( !( $buf == 'GIF87a' || $buf == 'GIF89a' ) ) {
 			throw new Exception( "Not a valid GIF file; header: $buf" );
 		}
-		
-		// Skip over width and height.
-		fread( $fh, 4 );
-		
+
+		// Read width and height.
+		$buf = fread( $fh, 2 );
+		$width = unpack( 'v', $buf )[1];
+		$buf = fread( $fh, 2 );
+		$height = unpack( 'v', $buf )[1];
+
 		// Read BPP
 		$buf = fread( $fh, 1 );
 		$bpp = self::decodeBPP( $buf );
-		
+
 		// Skip over background and aspect ratio
 		fread( $fh, 2 );
-		
+
 		// Skip over the GCT
 		self::readGCT( $fh, $bpp );
-		
-		while( !feof( $fh ) ) {
+
+		while ( !feof( $fh ) ) {
 			$buf = fread( $fh, 1 );
-			
-			if ($buf == self::$gif_frame_sep) {
+
+			if ( $buf == self::$gifFrameSep ) {
 				// Found a frame
 				$frameCount++;
-				
-				## Skip bounding box
+
+				# # Skip bounding box
 				fread( $fh, 8 );
-				
-				## Read BPP
+
+				# # Read BPP
 				$buf = fread( $fh, 1 );
 				$bpp = self::decodeBPP( $buf );
-				
-				## Read GCT
+
+				# # Read GCT
 				self::readGCT( $fh, $bpp );
 				fread( $fh, 1 );
-				self::skipBlock( $fh );	
-			} elseif ( $buf == self::$gif_extension_sep ) {
+				self::skipBlock( $fh );
+			} elseif ( $buf == self::$gifExtensionSep ) {
 				$buf = fread( $fh, 1 );
-				$extension_code = unpack( 'C', $buf );
-				$extension_code = $extension_code[1];
-				
-				if ($extension_code == 0xF9) {
+				if ( strlen( $buf ) < 1 ) {
+					throw new Exception( "Ran out of input" );
+				}
+				$extension_code = unpack( 'C', $buf )[1];
+
+				if ( $extension_code == 0xF9 ) {
 					// Graphics Control Extension.
 					fread( $fh, 1 ); // Block size
-					
+
 					fread( $fh, 1 ); // Transparency, disposal method, user input
-					
+
 					$buf = fread( $fh, 2 ); // Delay, in hundredths of seconds.
-					$delay = unpack( 'v', $buf );
-					$delay = $delay[1];
+					if ( strlen( $buf ) < 2 ) {
+						throw new Exception( "Ran out of input" );
+					}
+					$delay = unpack( 'v', $buf )[1];
 					$duration += $delay * 0.01;
-					
+
 					fread( $fh, 1 ); // Transparent colour index
-					
+
 					$term = fread( $fh, 1 ); // Should be a terminator
-					$term = unpack( 'C', $term );
-					$term = $term[1];
-					if ($term != 0 )
+					if ( strlen( $term ) < 1 ) {
+						throw new Exception( "Ran out of input" );
+					}
+					$term = unpack( 'C', $term )[1];
+					if ( $term != 0 ) {
 						throw new Exception( "Malformed Graphics Control Extension block" );
-				} elseif ($extension_code == 0xFF) {
+					}
+				} elseif ( $extension_code == 0xFE ) {
+					// Comment block(s).
+					$data = self::readBlock( $fh );
+					if ( $data === "" ) {
+						throw new Exception( 'Read error, zero-length comment block' );
+					}
+
+					// The standard says this should be ASCII, however its unclear if
+					// thats true in practise. Check to see if its valid utf-8, if so
+					// assume its that, otherwise assume its windows-1252 (iso-8859-1)
+					$dataCopy = $data;
+					// quickIsNFCVerify has the side effect of replacing any invalid characters
+					UtfNormal\Validator::quickIsNFCVerify( $dataCopy );
+
+					if ( $dataCopy !== $data ) {
+						MediaWiki\suppressWarnings();
+						$data = iconv( 'windows-1252', 'UTF-8', $data );
+						MediaWiki\restoreWarnings();
+					}
+
+					$commentCount = count( $comment );
+					if ( $commentCount === 0
+						|| $comment[$commentCount - 1] !== $data
+					) {
+						// Some applications repeat the same comment on each
+						// frame of an animated GIF image, so if this comment
+						// is identical to the last, only extract once.
+						$comment[] = $data;
+					}
+				} elseif ( $extension_code == 0xFF ) {
 					// Application extension (Netscape info about the animated gif)
+					// or XMP (or theoretically any other type of extension block)
 					$blockLength = fread( $fh, 1 );
-					$blockLength = unpack( 'C', $blockLength );
-					$blockLength = $blockLength[1];
+					if ( strlen( $blockLength ) < 1 ) {
+						throw new Exception( "Ran out of input" );
+					}
+					$blockLength = unpack( 'C', $blockLength )[1];
 					$data = fread( $fh, $blockLength );
-					
-					// NETSCAPE2.0 (application name)
-					if ($blockLength != 11 || $data != 'NETSCAPE2.0') {
-						fseek( $fh, -($blockLength + 1), SEEK_CUR );
+
+					if ( $blockLength != 11 ) {
+						wfDebug( __METHOD__ . " GIF application block with wrong length\n" );
+						fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
 						self::skipBlock( $fh );
 						continue;
 					}
-					
-					$data = fread( $fh, 2 ); // Block length and introduction, should be 03 01
-					
-					if ($data != "\x03\x01") {
-						throw new Exception( "Expected \x03\x01, got $data" );
-					}
-					
-					// Unsigned little-endian integer, loop count or zero for "forever"
-					$loopData = fread( $fh, 2 );
-					$loopData = unpack( 'v', $loopData );
-					$loopCount = $loopData[1];
-					
-					if ($loopCount != 1) {
-						$isLooped = true;
+
+					// NETSCAPE2.0 (application name for animated gif)
+					if ( $data == 'NETSCAPE2.0' ) {
+						$data = fread( $fh, 2 ); // Block length and introduction, should be 03 01
+
+						if ( $data != "\x03\x01" ) {
+							throw new Exception( "Expected \x03\x01, got $data" );
+						}
+
+						// Unsigned little-endian integer, loop count or zero for "forever"
+						$loopData = fread( $fh, 2 );
+						if ( strlen( $loopData ) < 2 ) {
+							throw new Exception( "Ran out of input" );
+						}
+						$loopCount = unpack( 'v', $loopData )[1];
+
+						if ( $loopCount != 1 ) {
+							$isLooped = true;
+						}
+
+						// Read out terminator byte
+						fread( $fh, 1 );
+					} elseif ( $data == 'XMP DataXMP' ) {
+						// application name for XMP data.
+						// see pg 18 of XMP spec part 3.
+
+						$xmp = self::readBlock( $fh, true );
+
+						if ( substr( $xmp, -257, 3 ) !== "\x01\xFF\xFE"
+							|| substr( $xmp, -4 ) !== "\x03\x02\x01\x00"
+						) {
+							// this is just a sanity check.
+							throw new Exception( "XMP does not have magic trailer!" );
+						}
+
+						// strip out trailer.
+						$xmp = substr( $xmp, 0, -257 );
+					} else {
+						// unrecognized extension block
+						fseek( $fh, -( $blockLength + 1 ), SEEK_CUR );
+						self::skipBlock( $fh );
+						continue;
 					}
-					
-					// Read out terminator byte
-					fread( $fh, 1 );
 				} else {
 					self::skipBlock( $fh );
 				}
-			} elseif ( $buf == self::$gif_term ) {
+			} elseif ( $buf == self::$gifTerm ) {
 				break;
 			} else {
-				$byte = unpack( 'C', $buf );
-				$byte = $byte[1];
-				throw new Exception( "At position: ".ftell($fh). ", Unknown byte ".$byte );
+				if ( strlen( $buf ) < 1 ) {
+					throw new Exception( "Ran out of input" );
+				}
+				$byte = unpack( 'C', $buf )[1];
+				throw new Exception( "At position: " . ftell( $fh ) . ", Unknown byte " . $byte );
 			}
 		}
-		
-		return array(
+
+		return [
 			'frameCount' => $frameCount,
 			'looped' => $isLooped,
-			'duration' => $duration
-		);
-		
+			'duration' => $duration,
+			'xmp' => $xmp,
+			'comment' => $comment,
+		];
 	}
-	
+
+	/**
+	 * @param resource $fh
+	 * @param int $bpp
+	 * @return void
+	 */
 	static function readGCT( $fh, $bpp ) {
-		if ($bpp > 0) {
-			for( $i=1; $i<=pow(2,$bpp); ++$i ) {
+		if ( $bpp > 0 ) {
+			$max = pow( 2, $bpp );
+			for ( $i = 1; $i <= $max; ++$i ) {
 				fread( $fh, 3 );
 			}
 		}
 	}
-	
+
+	/**
+	 * @param string $data
+	 * @throws Exception
+	 * @return int
+	 */
 	static function decodeBPP( $data ) {
-		$buf = unpack( 'C', $data );
-		$buf = $buf[1];
+		if ( strlen( $data ) < 1 ) {
+			throw new Exception( "Ran out of input" );
+		}
+		$buf = unpack( 'C', $data )[1];
 		$bpp = ( $buf & 7 ) + 1;
 		$buf >>= 7;
-		
+
 		$have_map = $buf & 1;
-		
+
 		return $have_map ? $bpp : 0;
 	}
-	
+
+	/**
+	 * @param resource $fh
+	 * @throws Exception
+	 */
 	static function skipBlock( $fh ) {
 		while ( !feof( $fh ) ) {
 			$buf = fread( $fh, 1 );
-			$block_len = unpack( 'C', $buf );
-			$block_len = $block_len[1];
-			if ($block_len == 0)
+			if ( strlen( $buf ) < 1 ) {
+				throw new Exception( "Ran out of input" );
+			}
+			$block_len = unpack( 'C', $buf )[1];
+			if ( $block_len == 0 ) {
 				return;
+			}
 			fread( $fh, $block_len );
 		}
 	}
 
+	/**
+	 * Read a block. In the GIF format, a block is made up of
+	 * several sub-blocks. Each sub block starts with one byte
+	 * saying how long the sub-block is, followed by the sub-block.
+	 * The entire block is terminated by a sub-block of length
+	 * 0.
+	 * @param resource $fh File handle
+	 * @param bool $includeLengths Include the length bytes of the
+	 *  sub-blocks in the returned value. Normally this is false,
+	 *  except XMP is weird and does a hack where you need to keep
+	 *  these length bytes.
+	 * @throws Exception
+	 * @return string The data.
+	 */
+	static function readBlock( $fh, $includeLengths = false ) {
+		$data = '';
+		$subLength = fread( $fh, 1 );
+		$blocks = 0;
+
+		while ( $subLength !== "\0" ) {
+			$blocks++;
+			if ( $blocks > self::MAX_SUBBLOCKS ) {
+				throw new Exception( "MAX_SUBBLOCKS exceeded (over $blocks sub-blocks)" );
+			}
+			if ( feof( $fh ) ) {
+				throw new Exception( "Read error: Unexpected EOF." );
+			}
+			if ( $includeLengths ) {
+				$data .= $subLength;
+			}
+
+			$data .= fread( $fh, ord( $subLength ) );
+			$subLength = fread( $fh, 1 );
+		}
+
+		return $data;
+	}
 }