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Ignore:
Timestamp:
12/12/2018 11:04:17 PM (6 years ago)
Author:
jeremyfelt
Message:

Media: Improve verification of MIME file types.

Merges [43988] to the 4.7 branch.

Location:
branches/4.7
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • branches/4.7

  • branches/4.7/src/wp-includes/functions.php

    r43395 r43991  
    23332333        finfo_close( $finfo );
    23342334
     2335        // fileinfo often misidentifies obscure files as one of these types
     2336        $nonspecific_types = array(
     2337            'application/octet-stream',
     2338            'application/encrypted',
     2339            'application/CDFV2-encrypted',
     2340            'application/zip',
     2341        );
     2342
    23352343        /*
    2336          * If $real_mime doesn't match what we're expecting, we need to do some extra
    2337          * vetting of application mime types to make sure this type of file is allowed.
    2338          * Other mime types are assumed to be safe, but should be considered unverified.
     2344         * If $real_mime doesn't match the content type we're expecting from the file's extension,
     2345         * we need to do some additional vetting. Media types and those listed in $nonspecific_types are
     2346         * allowed some leeway, but anything else must exactly match the real content type.
    23392347         */
    2340         if ( $real_mime && ( $real_mime !== $type ) && ( 0 === strpos( $real_mime, 'application' ) ) ) {
    2341             $allowed = get_allowed_mime_types();
    2342 
    2343             if ( ! in_array( $real_mime, $allowed ) ) {
     2348        if ( in_array( $real_mime, $nonspecific_types, true ) ) {
     2349            // File is a non-specific binary type. That's ok if it's a type that generally tends to be binary.
     2350            if ( !in_array( substr( $type, 0, strcspn( $type, '/' ) ), array( 'application', 'video', 'audio' ) ) ) {
    23442351                $type = $ext = false;
    23452352            }
     2353        } elseif ( 0 === strpos( $real_mime, 'video/' ) || 0 === strpos( $real_mime, 'audio/' ) ) {
     2354            /*
     2355             * For these types, only the major type must match the real value.
     2356             * This means that common mismatches are forgiven: application/vnd.apple.numbers is often misidentified as application/zip,
     2357             * and some media files are commonly named with the wrong extension (.mov instead of .mp4)
     2358             */
     2359
     2360            if ( substr( $real_mime, 0, strcspn( $real_mime, '/' ) ) !== substr( $type, 0, strcspn( $type, '/' ) ) ) {
     2361                $type = $ext = false;
     2362            }
     2363        } else {
     2364            if ( $type !== $real_mime ) {
     2365                /*
     2366                 * Everything else including image/* and application/*:
     2367                 * If the real content type doesn't match the file extension, assume it's dangerous.
     2368                 */
     2369                $type = $ext = false;
     2370            }
     2371
     2372        }
     2373    }
     2374
     2375    // The mime type must be allowed
     2376    if ( $type ) {
     2377        $allowed = get_allowed_mime_types();
     2378
     2379        if ( ! in_array( $type, $allowed ) ) {
     2380            $type = $ext = false;
    23462381        }
    23472382    }
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