Import: Handle uploads with sha1 starting with 0 properly

[mediawiki.git] / includes / MimeMagic.php

<?php
/**
 * Module defining helper functions for detecting and dealing with MIME types.
 *
 * 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
 */

/**
 * Defines a set of well known MIME types
 * This is used as a fallback to mime.types files.
 * An extensive list of well known MIME types is provided by
 * the file mime.types in the includes directory.
 *
 * This list concatenated with mime.types is used to create a MIME <-> ext
 * map. Each line contains a MIME type followed by a space separated list of
 * extensions. If multiple extensions for a single MIME type exist or if
 * multiple MIME types exist for a single extension then in most cases
 * MediaWiki assumes that the first extension following the MIME type is the
 * canonical extension, and the first time a MIME type appears for a certain
 * extension is considered the canonical MIME type.
 *
 * (Note that appending $wgMimeTypeFile to the end of MM_WELL_KNOWN_MIME_TYPES
 * sucks because you can't redefine canonical types. This could be fixed by
 * appending MM_WELL_KNOWN_MIME_TYPES behind $wgMimeTypeFile, but who knows
 * what will break? In practice this probably isn't a problem anyway -- Bryan)
 */
define( 'MM_WELL_KNOWN_MIME_TYPES', <<<END_STRING
application/ogg ogx ogg ogm ogv oga spx
application/pdf pdf
application/vnd.oasis.opendocument.chart odc
application/vnd.oasis.opendocument.chart-template otc
application/vnd.oasis.opendocument.database odb
application/vnd.oasis.opendocument.formula odf
application/vnd.oasis.opendocument.formula-template otf
application/vnd.oasis.opendocument.graphics odg
application/vnd.oasis.opendocument.graphics-template otg
application/vnd.oasis.opendocument.image odi
application/vnd.oasis.opendocument.image-template oti
application/vnd.oasis.opendocument.presentation odp
application/vnd.oasis.opendocument.presentation-template otp
application/vnd.oasis.opendocument.spreadsheet ods
application/vnd.oasis.opendocument.spreadsheet-template ots
application/vnd.oasis.opendocument.text odt
application/vnd.oasis.opendocument.text-master otm
application/vnd.oasis.opendocument.text-template ott
application/vnd.oasis.opendocument.text-web oth
application/x-javascript js
application/x-shockwave-flash swf
audio/midi mid midi kar
audio/mpeg mpga mpa mp2 mp3
audio/x-aiff aif aiff aifc
audio/x-wav wav
audio/ogg oga spx ogg
image/x-bmp bmp
image/gif gif
image/jpeg jpeg jpg jpe
image/png png
image/svg+xml svg
image/svg svg
image/tiff tiff tif
image/vnd.djvu djvu
image/x.djvu djvu
image/x-djvu djvu
image/x-portable-pixmap ppm
image/x-xcf xcf
text/plain txt
text/html html htm
video/ogg ogv ogm ogg
video/mpeg mpg mpeg
END_STRING
);

/**
 * Defines a set of well known MIME info entries
 * This is used as a fallback to mime.info files.
 * An extensive list of well known MIME types is provided by
 * the file mime.info in the includes directory.
 */
define( 'MM_WELL_KNOWN_MIME_INFO', <<<END_STRING
application/pdf [OFFICE]
application/vnd.oasis.opendocument.chart [OFFICE]
application/vnd.oasis.opendocument.chart-template [OFFICE]
application/vnd.oasis.opendocument.database [OFFICE]
application/vnd.oasis.opendocument.formula [OFFICE]
application/vnd.oasis.opendocument.formula-template [OFFICE]
application/vnd.oasis.opendocument.graphics [OFFICE]
application/vnd.oasis.opendocument.graphics-template [OFFICE]
application/vnd.oasis.opendocument.image [OFFICE]
application/vnd.oasis.opendocument.image-template [OFFICE]
application/vnd.oasis.opendocument.presentation [OFFICE]
application/vnd.oasis.opendocument.presentation-template [OFFICE]
application/vnd.oasis.opendocument.spreadsheet [OFFICE]
application/vnd.oasis.opendocument.spreadsheet-template [OFFICE]
application/vnd.oasis.opendocument.text [OFFICE]
application/vnd.oasis.opendocument.text-template [OFFICE]
application/vnd.oasis.opendocument.text-master [OFFICE]
application/vnd.oasis.opendocument.text-web [OFFICE]
text/javascript application/x-javascript [EXECUTABLE]
application/x-shockwave-flash [MULTIMEDIA]
audio/midi [AUDIO]
audio/x-aiff [AUDIO]
audio/x-wav [AUDIO]
audio/mp3 audio/mpeg [AUDIO]
application/ogg audio/ogg video/ogg [MULTIMEDIA]
image/x-bmp image/x-ms-bmp image/bmp [BITMAP]
image/gif [BITMAP]
image/jpeg [BITMAP]
image/png [BITMAP]
image/svg+xml [DRAWING]
image/tiff [BITMAP]
image/vnd.djvu [BITMAP]
image/x-xcf [BITMAP]
image/x-portable-pixmap [BITMAP]
text/plain [TEXT]
text/html [TEXT]
video/ogg [VIDEO]
video/mpeg [VIDEO]
unknown/unknown application/octet-stream application/x-empty [UNKNOWN]
END_STRING
);

/**
 * Implements functions related to MIME types such as detection and mapping to
 * file extension.
 *
 * Instances of this class are stateless, there only needs to be one global instance
 * of MimeMagic. Please use MimeMagic::singleton() to get that instance.
 */
class MimeMagic {
        /**
         * @var array Mapping of media types to arrays of MIME types.
         * This is used by findMediaType and getMediaType, respectively
         */
        protected $mMediaTypes = null;

        /** @var array Map of MIME type aliases
         */
        protected $mMimeTypeAliases = null;

        /** @var array Map of MIME types to file extensions (as a space separated list)
         */
        protected $mMimeToExt = null;

        /** @var array Map of file extensions types to MIME types (as a space separated list)
         */
        public $mExtToMime = null;

        /** @var IEContentAnalyzer
         */
        protected $mIEAnalyzer;

        /** @var string Extra MIME types, set for example by media handling extensions
         */
        private $mExtraTypes = '';

        /** @var string Extra MIME info, set for example by media handling extensions
         */
        private $mExtraInfo = '';

        /** @var Config */
        private $mConfig;

        /** @var MimeMagic The singleton instance
         */
        private static $instance = null;

        /** Initializes the MimeMagic object. This is called by MimeMagic::singleton().
         *
         * This constructor parses the mime.types and mime.info files and build internal mappings.
         *
         * @todo Make this constructor private once everything uses the singleton instance
         * @param Config $config
         */
        function __construct( Config $config = null ) {
                if ( !$config ) {
                        wfDebug( __METHOD__ . ' called with no Config instance passed to it' );
                        $config = ConfigFactory::getDefaultInstance()->makeConfig( 'main' );
                }
                $this->mConfig = $config;

                /**
                 *   --- load mime.types ---
                 */

                global $IP;

                # Allow media handling extensions adding MIME-types and MIME-info
                Hooks::run( 'MimeMagicInit', array( $this ) );

                $types = MM_WELL_KNOWN_MIME_TYPES;

                $mimeTypeFile = $this->mConfig->get( 'MimeTypeFile' );
                if ( $mimeTypeFile == 'includes/mime.types' ) {
                        $mimeTypeFile = "$IP/$mimeTypeFile";
                }

                if ( $mimeTypeFile ) {
                        if ( is_file( $mimeTypeFile ) && is_readable( $mimeTypeFile ) ) {
                                wfDebug( __METHOD__ . ": loading mime types from $mimeTypeFile\n" );
                                $types .= "\n";
                                $types .= file_get_contents( $mimeTypeFile );
                        } else {
                                wfDebug( __METHOD__ . ": can't load mime types from $mimeTypeFile\n" );
                        }
                } else {
                        wfDebug( __METHOD__ . ": no mime types file defined, using built-ins only.\n" );
                }

                $types .= "\n" . $this->mExtraTypes;

                $types = str_replace( array( "\r\n", "\n\r", "\n\n", "\r\r", "\r" ), "\n", $types );
                $types = str_replace( "\t", " ", $types );

                $this->mMimeToExt = array();
                $this->mExtToMime = array();

                $lines = explode( "\n", $types );
                foreach ( $lines as $s ) {
                        $s = trim( $s );
                        if ( empty( $s ) ) {
                                continue;
                        }
                        if ( strpos( $s, '#' ) === 0 ) {
                                continue;
                        }

                        $s = strtolower( $s );
                        $i = strpos( $s, ' ' );

                        if ( $i === false ) {
                                continue;
                        }

                        $mime = substr( $s, 0, $i );
                        $ext = trim( substr( $s, $i + 1 ) );

                        if ( empty( $ext ) ) {
                                continue;
                        }

                        if ( !empty( $this->mMimeToExt[$mime] ) ) {
                                $this->mMimeToExt[$mime] .= ' ' . $ext;
                        } else {
                                $this->mMimeToExt[$mime] = $ext;
                        }

                        $extensions = explode( ' ', $ext );

                        foreach ( $extensions as $e ) {
                                $e = trim( $e );
                                if ( empty( $e ) ) {
                                        continue;
                                }

                                if ( !empty( $this->mExtToMime[$e] ) ) {
                                        $this->mExtToMime[$e] .= ' ' . $mime;
                                } else {
                                        $this->mExtToMime[$e] = $mime;
                                }
                        }
                }

                /**
                 *   --- load mime.info ---
                 */

                $mimeInfoFile = $this->mConfig->get( 'MimeInfoFile' );
                if ( $mimeInfoFile == 'includes/mime.info' ) {
                        $mimeInfoFile = "$IP/$mimeInfoFile";
                }

                $info = MM_WELL_KNOWN_MIME_INFO;

                if ( $mimeInfoFile ) {
                        if ( is_file( $mimeInfoFile ) && is_readable( $mimeInfoFile ) ) {
                                wfDebug( __METHOD__ . ": loading mime info from $mimeInfoFile\n" );
                                $info .= "\n";
                                $info .= file_get_contents( $mimeInfoFile );
                        } else {
                                wfDebug( __METHOD__ . ": can't load mime info from $mimeInfoFile\n" );
                        }
                } else {
                        wfDebug( __METHOD__ . ": no mime info file defined, using built-ins only.\n" );
                }

                $info .= "\n" . $this->mExtraInfo;

                $info = str_replace( array( "\r\n", "\n\r", "\n\n", "\r\r", "\r" ), "\n", $info );
                $info = str_replace( "\t", " ", $info );

                $this->mMimeTypeAliases = array();
                $this->mMediaTypes = array();

                $lines = explode( "\n", $info );
                foreach ( $lines as $s ) {
                        $s = trim( $s );
                        if ( empty( $s ) ) {
                                continue;
                        }
                        if ( strpos( $s, '#' ) === 0 ) {
                                continue;
                        }

                        $s = strtolower( $s );
                        $i = strpos( $s, ' ' );

                        if ( $i === false ) {
                                continue;
                        }

                        # print "processing MIME INFO line $s<br>";

                        $match = array();
                        if ( preg_match( '!\[\s*(\w+)\s*\]!', $s, $match ) ) {
                                $s = preg_replace( '!\[\s*(\w+)\s*\]!', '', $s );
                                $mtype = trim( strtoupper( $match[1] ) );
                        } else {
                                $mtype = MEDIATYPE_UNKNOWN;
                        }

                        $m = explode( ' ', $s );

                        if ( !isset( $this->mMediaTypes[$mtype] ) ) {
                                $this->mMediaTypes[$mtype] = array();
                        }

                        foreach ( $m as $mime ) {
                                $mime = trim( $mime );
                                if ( empty( $mime ) ) {
                                        continue;
                                }

                                $this->mMediaTypes[$mtype][] = $mime;
                        }

                        if ( count( $m ) > 1 ) {
                                $main = $m[0];
                                $mCount = count( $m );
                                for ( $i = 1; $i < $mCount; $i += 1 ) {
                                        $mime = $m[$i];
                                        $this->mMimeTypeAliases[$mime] = $main;
                                }
                        }
                }
        }

        /**
         * Get an instance of this class
         * @return MimeMagic
         */
        public static function singleton() {
                if ( self::$instance === null ) {
                        self::$instance = new MimeMagic(
                                ConfigFactory::getDefaultInstance()->makeConfig( 'main' )
                        );
                }
                return self::$instance;
        }

        /**
         * Adds to the list mapping MIME to file extensions.
         * As an extension author, you are encouraged to submit patches to
         * MediaWiki's core to add new MIME types to mime.types.
         * @param string $types
         */
        public function addExtraTypes( $types ) {
                $this->mExtraTypes .= "\n" . $types;
        }

        /**
         * Adds to the list mapping MIME to media type.
         * As an extension author, you are encouraged to submit patches to
         * MediaWiki's core to add new MIME info to mime.info.
         * @param string $info
         */
        public function addExtraInfo( $info ) {
                $this->mExtraInfo .= "\n" . $info;
        }

        /**
         * Returns a list of file extensions for a given MIME type as a space
         * separated string or null if the MIME type was unrecognized. Resolves
         * MIME type aliases.
         *
         * @param string $mime
         * @return string|null
         */
        public function getExtensionsForType( $mime ) {
                $mime = strtolower( $mime );

                // Check the mime-to-ext map
                if ( isset( $this->mMimeToExt[$mime] ) ) {
                        return $this->mMimeToExt[$mime];
                }

                // Resolve the MIME type to the canonical type
                if ( isset( $this->mMimeTypeAliases[$mime] ) ) {
                        $mime = $this->mMimeTypeAliases[$mime];
                        if ( isset( $this->mMimeToExt[$mime] ) ) {
                                return $this->mMimeToExt[$mime];
                        }
                }

                return null;
        }

        /**
         * Returns a list of MIME types for a given file extension as a space
         * separated string or null if the extension was unrecognized.
         *
         * @param string $ext
         * @return string|null
         */
        public function getTypesForExtension( $ext ) {
                $ext = strtolower( $ext );

                $r = isset( $this->mExtToMime[$ext] ) ? $this->mExtToMime[$ext] : null;
                return $r;
        }

        /**
         * Returns a single MIME type for a given file extension or null if unknown.
         * This is always the first type from the list returned by getTypesForExtension($ext).
         *
         * @param string $ext
         * @return string|null
         */
        public function guessTypesForExtension( $ext ) {
                $m = $this->getTypesForExtension( $ext );
                if ( is_null( $m ) ) {
                        return null;
                }

                // TODO: Check if this is needed; strtok( $m, ' ' ) should be sufficient
                $m = trim( $m );
                $m = preg_replace( '/\s.*$/', '', $m );

                return $m;
        }

        /**
         * Tests if the extension matches the given MIME type. Returns true if a
         * match was found, null if the MIME type is unknown, and false if the
         * MIME type is known but no matches where found.
         *
         * @param string $extension
         * @param string $mime
         * @return bool|null
         */
        public function isMatchingExtension( $extension, $mime ) {
                $ext = $this->getExtensionsForType( $mime );

                if ( !$ext ) {
                        return null; // Unknown MIME type
                }

                $ext = explode( ' ', $ext );

                $extension = strtolower( $extension );
                return in_array( $extension, $ext );
        }

        /**
         * Returns true if the MIME type is known to represent an image format
         * supported by the PHP GD library.
         *
         * @param string $mime
         *
         * @return bool
         */
        public function isPHPImageType( $mime ) {
                // As defined by imagegetsize and image_type_to_mime
                static $types = array(
                        'image/gif', 'image/jpeg', 'image/png',
                        'image/x-bmp', 'image/xbm', 'image/tiff',
                        'image/jp2', 'image/jpeg2000', 'image/iff',
                        'image/xbm', 'image/x-xbitmap',
                        'image/vnd.wap.wbmp', 'image/vnd.xiff',
                        'image/x-photoshop',
                        'application/x-shockwave-flash',
                );

                return in_array( $mime, $types );
        }

        /**
         * Returns true if the extension represents a type which can
         * be reliably detected from its content. Use this to determine
         * whether strict content checks should be applied to reject
         * invalid uploads; if we can't identify the type we won't
         * be able to say if it's invalid.
         *
         * @todo Be more accurate when using fancy MIME detector plugins;
         *       right now this is the bare minimum getimagesize() list.
         * @param string $extension
         * @return bool
         */
        function isRecognizableExtension( $extension ) {
                static $types = array(
                        // Types recognized by getimagesize()
                        'gif', 'jpeg', 'jpg', 'png', 'swf', 'psd',
                        'bmp', 'tiff', 'tif', 'jpc', 'jp2',
                        'jpx', 'jb2', 'swc', 'iff', 'wbmp',
                        'xbm',

                        // Formats we recognize magic numbers for
                        'djvu', 'ogx', 'ogg', 'ogv', 'oga', 'spx',
                        'mid', 'pdf', 'wmf', 'xcf', 'webm', 'mkv', 'mka',
                        'webp',

                        // XML formats we sure hope we recognize reliably
                        'svg',
                );
                return in_array( strtolower( $extension ), $types );
        }

        /**
         * Improves a MIME type using the file extension. Some file formats are very generic,
         * so their MIME type is not very meaningful. A more useful MIME type can be derived
         * by looking at the file extension. Typically, this method would be called on the
         * result of guessMimeType().
         *
         * @param string $mime The MIME type, typically guessed from a file's content.
         * @param string $ext The file extension, as taken from the file name
         *
         * @return string The MIME type
         */
        public function improveTypeFromExtension( $mime, $ext ) {
                if ( $mime === 'unknown/unknown' ) {
                        if ( $this->isRecognizableExtension( $ext ) ) {
                                wfDebug( __METHOD__ . ': refusing to guess mime type for .' .
                                        "$ext file, we should have recognized it\n" );
                        } else {
                                // Not something we can detect, so simply
                                // trust the file extension
                                $mime = $this->guessTypesForExtension( $ext );
                        }
                } elseif ( $mime === 'application/x-opc+zip' ) {
                        if ( $this->isMatchingExtension( $ext, $mime ) ) {
                                // A known file extension for an OPC file,
                                // find the proper MIME type for that file extension
                                $mime = $this->guessTypesForExtension( $ext );
                        } else {
                                wfDebug( __METHOD__ . ": refusing to guess better type for $mime file, " .
                                        ".$ext is not a known OPC extension.\n" );
                                $mime = 'application/zip';
                        }
                } elseif ( $mime === 'text/plain' && $this->findMediaType( ".$ext" ) === MEDIATYPE_TEXT ) {
                        // Textual types are sometimes not recognized properly.
                        // If detected as text/plain, and has an extension which is textual
                        // improve to the extension's type. For example, csv and json are often
                        // misdetected as text/plain.
                        $mime = $this->guessTypesForExtension( $ext );
                }

                # Media handling extensions can improve the MIME detected
                Hooks::run( 'MimeMagicImproveFromExtension', array( $this, $ext, &$mime ) );

                if ( isset( $this->mMimeTypeAliases[$mime] ) ) {
                        $mime = $this->mMimeTypeAliases[$mime];
                }

                wfDebug( __METHOD__ . ": improved mime type for .$ext: $mime\n" );
                return $mime;
        }

        /**
         * MIME type detection. This uses detectMimeType to detect the MIME type
         * of the file, but applies additional checks to determine some well known
         * file formats that may be missed or misinterpreted by the default MIME
         * detection (namely XML based formats like XHTML or SVG, as well as ZIP
         * based formats like OPC/ODF files).
         *
         * @param string $file The file to check
         * @param string|bool $ext The file extension, or true (default) to extract it from the filename.
         *   Set it to false to ignore the extension. DEPRECATED! Set to false, use
         *   improveTypeFromExtension($mime, $ext) later to improve MIME type.
         *
         * @return string The MIME type of $file
         */
        public function guessMimeType( $file, $ext = true ) {
                if ( $ext ) { // TODO: make $ext default to false. Or better, remove it.
                        wfDebug( __METHOD__ . ": WARNING: use of the \$ext parameter is deprecated. " .
                                "Use improveTypeFromExtension(\$mime, \$ext) instead.\n" );
                }

                $mime = $this->doGuessMimeType( $file, $ext );

                if ( !$mime ) {
                        wfDebug( __METHOD__ . ": internal type detection failed for $file (.$ext)...\n" );
                        $mime = $this->detectMimeType( $file, $ext );
                }

                if ( isset( $this->mMimeTypeAliases[$mime] ) ) {
                        $mime = $this->mMimeTypeAliases[$mime];
                }

                wfDebug( __METHOD__ . ": guessed mime type of $file: $mime\n" );
                return $mime;
        }

        /**
         * Guess the MIME type from the file contents.
         *
         * @todo Remove $ext param
         *
         * @param string $file
         * @param mixed $ext
         * @return bool|string
         * @throws MWException
         */
        private function doGuessMimeType( $file, $ext ) {
                // Read a chunk of the file
                MediaWiki\suppressWarnings();
                $f = fopen( $file, 'rb' );
                MediaWiki\restoreWarnings();

                if ( !$f ) {
                        return 'unknown/unknown';
                }

                $fsize = filesize( $file );
                if ( $fsize === false ) {
                        return 'unknown/unknown';
                }

                $head = fread( $f, 1024 );
                $tailLength = min( 65558, $fsize ); // 65558 = maximum size of a zip EOCDR
                if ( fseek( $f, -1 * $tailLength, SEEK_END ) === -1 ) {
                        throw new MWException(
                                "Seeking $tailLength bytes from EOF failed in " . __METHOD__ );
                }
                $tail = fread( $f, $tailLength );
                fclose( $f );

                wfDebug( __METHOD__ . ": analyzing head and tail of $file for magic numbers.\n" );

                // Hardcode a few magic number checks...
                $headers = array(
                        // Multimedia...
                        'MThd'             => 'audio/midi',
                        'OggS'             => 'application/ogg',

                        // Image formats...
                        // Note that WMF may have a bare header, no magic number.
                        "\x01\x00\x09\x00" => 'application/x-msmetafile', // Possibly prone to false positives?
                        "\xd7\xcd\xc6\x9a" => 'application/x-msmetafile',
                        '%PDF'             => 'application/pdf',
                        'gimp xcf'         => 'image/x-xcf',

                        // Some forbidden fruit...
                        'MZ'               => 'application/octet-stream', // DOS/Windows executable
                        "\xca\xfe\xba\xbe" => 'application/octet-stream', // Mach-O binary
                        "\x7fELF"          => 'application/octet-stream', // ELF binary
                );

                foreach ( $headers as $magic => $candidate ) {
                        if ( strncmp( $head, $magic, strlen( $magic ) ) == 0 ) {
                                wfDebug( __METHOD__ . ": magic header in $file recognized as $candidate\n" );
                                return $candidate;
                        }
                }

                /* Look for WebM and Matroska files */
                if ( strncmp( $head, pack( "C4", 0x1a, 0x45, 0xdf, 0xa3 ), 4 ) == 0 ) {
                        $doctype = strpos( $head, "\x42\x82" );
                        if ( $doctype ) {
                                // Next byte is datasize, then data (sizes larger than 1 byte are very stupid muxers)
                                $data = substr( $head, $doctype + 3, 8 );
                                if ( strncmp( $data, "matroska", 8 ) == 0 ) {
                                        wfDebug( __METHOD__ . ": recognized file as video/x-matroska\n" );
                                        return "video/x-matroska";
                                } elseif ( strncmp( $data, "webm", 4 ) == 0 ) {
                                        wfDebug( __METHOD__ . ": recognized file as video/webm\n" );
                                        return "video/webm";
                                }
                        }
                        wfDebug( __METHOD__ . ": unknown EBML file\n" );
                        return "unknown/unknown";
                }

                /* Look for WebP */
                if ( strncmp( $head, "RIFF", 4 ) == 0 && strncmp( substr( $head, 8, 7 ), "WEBPVP8", 7 ) == 0 ) {
                        wfDebug( __METHOD__ . ": recognized file as image/webp\n" );
                        return "image/webp";
                }

                /**
                 * Look for PHP.  Check for this before HTML/XML...  Warning: this is a
                 * heuristic, and won't match a file with a lot of non-PHP before.  It
                 * will also match text files which could be PHP. :)
                 *
                 * @todo FIXME: For this reason, the check is probably useless -- an attacker
                 * could almost certainly just pad the file with a lot of nonsense to
                 * circumvent the check in any case where it would be a security
                 * problem.  On the other hand, it causes harmful false positives (bug
                 * 16583).  The heuristic has been cut down to exclude three-character
                 * strings like "<? ", but should it be axed completely?
                 */
                if ( ( strpos( $head, '<?php' ) !== false ) ||
                        ( strpos( $head, "<\x00?\x00p\x00h\x00p" ) !== false ) ||
                        ( strpos( $head, "<\x00?\x00 " ) !== false ) ||
                        ( strpos( $head, "<\x00?\x00\n" ) !== false ) ||
                        ( strpos( $head, "<\x00?\x00\t" ) !== false ) ||
                        ( strpos( $head, "<\x00?\x00=" ) !== false ) ) {

                        wfDebug( __METHOD__ . ": recognized $file as application/x-php\n" );
                        return 'application/x-php';
                }

                /**
                 * look for XML formats (XHTML and SVG)
                 */
                $xml = new XmlTypeCheck( $file );
                if ( $xml->wellFormed ) {
                        $xmlMimeTypes = $this->mConfig->get( 'XMLMimeTypes' );
                        if ( isset( $xmlMimeTypes[$xml->getRootElement()] ) ) {
                                return $xmlMimeTypes[$xml->getRootElement()];
                        } else {
                                return 'application/xml';
                        }
                }

                /**
                 * look for shell scripts
                 */
                $script_type = null;

                # detect by shebang
                if ( substr( $head, 0, 2 ) == "#!" ) {
                        $script_type = "ASCII";
                } elseif ( substr( $head, 0, 5 ) == "\xef\xbb\xbf#!" ) {
                        $script_type = "UTF-8";
                } elseif ( substr( $head, 0, 7 ) == "\xfe\xff\x00#\x00!" ) {
                        $script_type = "UTF-16BE";
                } elseif ( substr( $head, 0, 7 ) == "\xff\xfe#\x00!" ) {
                        $script_type = "UTF-16LE";
                }

                if ( $script_type ) {
                        if ( $script_type !== "UTF-8" && $script_type !== "ASCII" ) {
                                // Quick and dirty fold down to ASCII!
                                $pack = array( 'UTF-16BE' => 'n*', 'UTF-16LE' => 'v*' );
                                $chars = unpack( $pack[$script_type], substr( $head, 2 ) );
                                $head = '';
                                foreach ( $chars as $codepoint ) {
                                        if ( $codepoint < 128 ) {
                                                $head .= chr( $codepoint );
                                        } else {
                                                $head .= '?';
                                        }
                                }
                        }

                        $match = array();

                        if ( preg_match( '%/?([^\s]+/)(\w+)%', $head, $match ) ) {
                                $mime = "application/x-{$match[2]}";
                                wfDebug( __METHOD__ . ": shell script recognized as $mime\n" );
                                return $mime;
                        }
                }

                // Check for ZIP variants (before getimagesize)
                if ( strpos( $tail, "PK\x05\x06" ) !== false ) {
                        wfDebug( __METHOD__ . ": ZIP header present in $file\n" );
                        return $this->detectZipType( $head, $tail, $ext );
                }

                MediaWiki\suppressWarnings();
                $gis = getimagesize( $file );
                MediaWiki\restoreWarnings();

                if ( $gis && isset( $gis['mime'] ) ) {
                        $mime = $gis['mime'];
                        wfDebug( __METHOD__ . ": getimagesize detected $file as $mime\n" );
                        return $mime;
                }

                // Also test DjVu
                $deja = new DjVuImage( $file );
                if ( $deja->isValid() ) {
                        wfDebug( __METHOD__ . ": detected $file as image/vnd.djvu\n" );
                        return 'image/vnd.djvu';
                }

                # Media handling extensions can guess the MIME by content
                # It's intentionally here so that if core is wrong about a type (false positive),
                # people will hopefully nag and submit patches :)
                $mime = false;
                # Some strings by reference for performance - assuming well-behaved hooks
                Hooks::run(
                        'MimeMagicGuessFromContent',
                        array( $this, &$head, &$tail, $file, &$mime )
                );

                return $mime;
        }

        /**
         * Detect application-specific file type of a given ZIP file from its
         * header data.  Currently works for OpenDocument and OpenXML types...
         * If can't tell, returns 'application/zip'.
         *
         * @param string $header Some reasonably-sized chunk of file header
         * @param string|null $tail The tail of the file
         * @param string|bool $ext The file extension, or true to extract it from the filename.
         *   Set it to false (default) to ignore the extension. DEPRECATED! Set to false,
         *   use improveTypeFromExtension($mime, $ext) later to improve MIME type.
         *
         * @return string
         */
        function detectZipType( $header, $tail = null, $ext = false ) {
                if ( $ext ) { # TODO: remove $ext param
                        wfDebug( __METHOD__ . ": WARNING: use of the \$ext parameter is deprecated. " .
                                "Use improveTypeFromExtension(\$mime, \$ext) instead.\n" );
                }

                $mime = 'application/zip';
                $opendocTypes = array(
                        'chart-template',
                        'chart',
                        'formula-template',
                        'formula',
                        'graphics-template',
                        'graphics',
                        'image-template',
                        'image',
                        'presentation-template',
                        'presentation',
                        'spreadsheet-template',
                        'spreadsheet',
                        'text-template',
                        'text-master',
                        'text-web',
                        'text' );

                // http://lists.oasis-open.org/archives/office/200505/msg00006.html
                $types = '(?:' . implode( '|', $opendocTypes ) . ')';
                $opendocRegex = "/^mimetype(application\/vnd\.oasis\.opendocument\.$types)/";

                $openxmlRegex = "/^\[Content_Types\].xml/";

                if ( preg_match( $opendocRegex, substr( $header, 30 ), $matches ) ) {
                        $mime = $matches[1];
                        wfDebug( __METHOD__ . ": detected $mime from ZIP archive\n" );
                } elseif ( preg_match( $openxmlRegex, substr( $header, 30 ) ) ) {
                        $mime = "application/x-opc+zip";
                        # TODO: remove the block below, as soon as improveTypeFromExtension is used everywhere
                        if ( $ext !== true && $ext !== false ) {
                                /** This is the mode used by getPropsFromPath
                                 * These MIME's are stored in the database, where we don't really want
                                 * x-opc+zip, because we use it only for internal purposes
                                 */
                                if ( $this->isMatchingExtension( $ext, $mime ) ) {
                                        /* A known file extension for an OPC file,
                                         * find the proper mime type for that file extension
                                         */
                                        $mime = $this->guessTypesForExtension( $ext );
                                } else {
                                        $mime = "application/zip";
                                }
                        }
                        wfDebug( __METHOD__ . ": detected an Open Packaging Conventions archive: $mime\n" );
                } elseif ( substr( $header, 0, 8 ) == "\xd0\xcf\x11\xe0\xa1\xb1\x1a\xe1" &&
                                ( $headerpos = strpos( $tail, "PK\x03\x04" ) ) !== false &&
                                preg_match( $openxmlRegex, substr( $tail, $headerpos + 30 ) ) ) {
                        if ( substr( $header, 512, 4 ) == "\xEC\xA5\xC1\x00" ) {
                                $mime = "application/msword";
                        }
                        switch ( substr( $header, 512, 6 ) ) {
                                case "\xEC\xA5\xC1\x00\x0E\x00":
                                case "\xEC\xA5\xC1\x00\x1C\x00":
                                case "\xEC\xA5\xC1\x00\x43\x00":
                                        $mime = "application/vnd.ms-powerpoint";
                                        break;
                                case "\xFD\xFF\xFF\xFF\x10\x00":
                                case "\xFD\xFF\xFF\xFF\x1F\x00":
                                case "\xFD\xFF\xFF\xFF\x22\x00":
                                case "\xFD\xFF\xFF\xFF\x23\x00":
                                case "\xFD\xFF\xFF\xFF\x28\x00":
                                case "\xFD\xFF\xFF\xFF\x29\x00":
                                case "\xFD\xFF\xFF\xFF\x10\x02":
                                case "\xFD\xFF\xFF\xFF\x1F\x02":
                                case "\xFD\xFF\xFF\xFF\x22\x02":
                                case "\xFD\xFF\xFF\xFF\x23\x02":
                                case "\xFD\xFF\xFF\xFF\x28\x02":
                                case "\xFD\xFF\xFF\xFF\x29\x02":
                                        $mime = "application/vnd.msexcel";
                                        break;
                        }

                        wfDebug( __METHOD__ . ": detected a MS Office document with OPC trailer\n" );
                } else {
                        wfDebug( __METHOD__ . ": unable to identify type of ZIP archive\n" );
                }
                return $mime;
        }

        /**
         * Internal MIME type detection. Detection is done using an external
         * program, if $wgMimeDetectorCommand is set. Otherwise, the fileinfo
         * extension is tried if it is available. If detection fails and $ext
         * is not false, the MIME type is guessed from the file extension,
         * using guessTypesForExtension.
         *
         * If the MIME type is still unknown, getimagesize is used to detect the
         * MIME type if the file is an image. If no MIME type can be determined,
         * this function returns 'unknown/unknown'.
         *
         * @param string $file The file to check
         * @param string|bool $ext The file extension, or true (default) to extract it from the filename.
         *   Set it to false to ignore the extension. DEPRECATED! Set to false, use
         *   improveTypeFromExtension($mime, $ext) later to improve MIME type.
         *
         * @return string The MIME type of $file
         */
        private function detectMimeType( $file, $ext = true ) {
                /** @todo Make $ext default to false. Or better, remove it. */
                if ( $ext ) {
                        wfDebug( __METHOD__ . ": WARNING: use of the \$ext parameter is deprecated. "
                                . "Use improveTypeFromExtension(\$mime, \$ext) instead.\n" );
                }

                $mimeDetectorCommand = $this->mConfig->get( 'MimeDetectorCommand' );
                $m = null;
                if ( $mimeDetectorCommand ) {
                        $args = wfEscapeShellArg( $file );
                        $m = wfShellExec( "$mimeDetectorCommand $args" );
                } elseif ( function_exists( "finfo_open" ) && function_exists( "finfo_file" ) ) {
                        $mime_magic_resource = finfo_open( FILEINFO_MIME );

                        if ( $mime_magic_resource ) {
                                $m = finfo_file( $mime_magic_resource, $file );
                                finfo_close( $mime_magic_resource );
                        } else {
                                wfDebug( __METHOD__ . ": finfo_open failed on " . FILEINFO_MIME . "!\n" );
                        }
                } else {
                        wfDebug( __METHOD__ . ": no magic mime detector found!\n" );
                }

                if ( $m ) {
                        # normalize
                        $m = preg_replace( '![;, ].*$!', '', $m ); # strip charset, etc
                        $m = trim( $m );
                        $m = strtolower( $m );

                        if ( strpos( $m, 'unknown' ) !== false ) {
                                $m = null;
                        } else {
                                wfDebug( __METHOD__ . ": magic mime type of $file: $m\n" );
                                return $m;
                        }
                }

                // If desired, look at extension as a fallback.
                if ( $ext === true ) {
                        $i = strrpos( $file, '.' );
                        $ext = strtolower( $i ? substr( $file, $i + 1 ) : '' );
                }
                if ( $ext ) {
                        if ( $this->isRecognizableExtension( $ext ) ) {
                                wfDebug( __METHOD__ . ": refusing to guess mime type for .$ext file, "
                                        . "we should have recognized it\n" );
                        } else {
                                $m = $this->guessTypesForExtension( $ext );
                                if ( $m ) {
                                        wfDebug( __METHOD__ . ": extension mime type of $file: $m\n" );
                                        return $m;
                                }
                        }
                }

                // Unknown type
                wfDebug( __METHOD__ . ": failed to guess mime type for $file!\n" );
                return 'unknown/unknown';
        }

        /**
         * Determine the media type code for a file, using its MIME type, name and
         * possibly its contents.
         *
         * This function relies on the findMediaType(), mapping extensions and MIME
         * types to media types.
         *
         * @todo analyse file if need be
         * @todo look at multiple extension, separately and together.
         *
         * @param string $path Full path to the image file, in case we have to look at the contents
         *        (if null, only the MIME type is used to determine the media type code).
         * @param string $mime MIME type. If null it will be guessed using guessMimeType.
         *
         * @return string A value to be used with the MEDIATYPE_xxx constants.
         */
        function getMediaType( $path = null, $mime = null ) {
                if ( !$mime && !$path ) {
                        return MEDIATYPE_UNKNOWN;
                }

                // If MIME type is unknown, guess it
                if ( !$mime ) {
                        $mime = $this->guessMimeType( $path, false );
                }

                // Special code for ogg - detect if it's video (theora),
                // else label it as sound.
                if ( $mime == 'application/ogg' && file_exists( $path ) ) {

                        // Read a chunk of the file
                        $f = fopen( $path, "rt" );
                        if ( !$f ) {
                                return MEDIATYPE_UNKNOWN;
                        }
                        $head = fread( $f, 256 );
                        fclose( $f );

                        $head = str_replace( 'ffmpeg2theora', '', strtolower( $head ) );

                        // This is an UGLY HACK, file should be parsed correctly
                        if ( strpos( $head, 'theora' ) !== false ) {
                                return MEDIATYPE_VIDEO;
                        } elseif ( strpos( $head, 'vorbis' ) !== false ) {
                                return MEDIATYPE_AUDIO;
                        } elseif ( strpos( $head, 'flac' ) !== false ) {
                                return MEDIATYPE_AUDIO;
                        } elseif ( strpos( $head, 'speex' ) !== false ) {
                                return MEDIATYPE_AUDIO;
                        } else {
                                return MEDIATYPE_MULTIMEDIA;
                        }
                }

                // Check for entry for full MIME type
                if ( $mime ) {
                        $type = $this->findMediaType( $mime );
                        if ( $type !== MEDIATYPE_UNKNOWN ) {
                                return $type;
                        }
                }

                // Check for entry for file extension
                if ( $path ) {
                        $i = strrpos( $path, '.' );
                        $e = strtolower( $i ? substr( $path, $i + 1 ) : '' );

                        // TODO: look at multi-extension if this fails, parse from full path
                        $type = $this->findMediaType( '.' . $e );
                        if ( $type !== MEDIATYPE_UNKNOWN ) {
                                return $type;
                        }
                }

                // Check major MIME type
                if ( $mime ) {
                        $i = strpos( $mime, '/' );
                        if ( $i !== false ) {
                                $major = substr( $mime, 0, $i );
                                $type = $this->findMediaType( $major );
                                if ( $type !== MEDIATYPE_UNKNOWN ) {
                                        return $type;
                                }
                        }
                }

                if ( !$type ) {
                        $type = MEDIATYPE_UNKNOWN;
                }

                return $type;
        }

        /**
         * Returns a media code matching the given MIME type or file extension.
         * File extensions are represented by a string starting with a dot (.) to
         * distinguish them from MIME types.
         *
         * This function relies on the mapping defined by $this->mMediaTypes
         * @access private
         * @param string $extMime
         * @return int|string
         */
        function findMediaType( $extMime ) {
                if ( strpos( $extMime, '.' ) === 0 ) {
                        // If it's an extension, look up the MIME types
                        $m = $this->getTypesForExtension( substr( $extMime, 1 ) );
                        if ( !$m ) {
                                return MEDIATYPE_UNKNOWN;
                        }

                        $m = explode( ' ', $m );
                } else {
                        // Normalize MIME type
                        if ( isset( $this->mMimeTypeAliases[$extMime] ) ) {
                                $extMime = $this->mMimeTypeAliases[$extMime];
                        }

                        $m = array( $extMime );
                }

                foreach ( $m as $mime ) {
                        foreach ( $this->mMediaTypes as $type => $codes ) {
                                if ( in_array( $mime, $codes, true ) ) {
                                        return $type;
                                }
                        }
                }

                return MEDIATYPE_UNKNOWN;
        }

        /**
         * Get the MIME types that various versions of Internet Explorer would
         * detect from a chunk of the content.
         *
         * @param string $fileName The file name (unused at present)
         * @param string $chunk The first 256 bytes of the file
         * @param string $proposed The MIME type proposed by the server
         * @return array
         */
        public function getIEMimeTypes( $fileName, $chunk, $proposed ) {
                $ca = $this->getIEContentAnalyzer();
                return $ca->getRealMimesFromData( $fileName, $chunk, $proposed );
        }

        /**
         * Get a cached instance of IEContentAnalyzer
         *
         * @return IEContentAnalyzer
         */
        protected function getIEContentAnalyzer() {
                if ( is_null( $this->mIEAnalyzer ) ) {
                        $this->mIEAnalyzer = new IEContentAnalyzer;
                }
                return $this->mIEAnalyzer;
        }
}