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Media: Improve verification of MIME file types. 

Merges [43988] to the 4.6 branch.

Built from https://develop.svn.wordpress.org/branches/4.6@43992


git-svn-id: http://core.svn.wordpress.org/branches/4.6@43824 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This commit is contained in:
Jeremy Felt 2018-12-12 23:08:22 +00:00
parent 4f99911c22
commit bcbb4f7808
1 changed files with 49 additions and 4 deletions
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53
wp-includes/functions.php
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@ -2313,14 +2313,59 @@ function wp_check_filetype_and_ext( $file, $filename, $mimes = null ) {
$type = $ext = false;
}
}
} elseif ( function_exists( 'finfo_file' ) ) {
// Use finfo_file if available to validate non-image files.
}
// Validate files that didn't get validated during previous checks.
if ( $type && ! $real_mime && extension_loaded( 'fileinfo' ) ) {
$finfo = finfo_open( FILEINFO_MIME_TYPE );
$real_mime = finfo_file( $finfo, $file );
finfo_close( $finfo );
// If the extension does not match the file's real type, return false.
if ( $real_mime !== $type ) {
// fileinfo often misidentifies obscure files as one of these types
$nonspecific_types = array(
'application/octet-stream',
'application/encrypted',
'application/CDFV2-encrypted',
'application/zip',
);
/*
* If $real_mime doesn't match the content type we're expecting from the file's extension,
* we need to do some additional vetting. Media types and those listed in $nonspecific_types are
* allowed some leeway, but anything else must exactly match the real content type.
*/
if ( in_array( $real_mime, $nonspecific_types, true ) ) {
// File is a non-specific binary type. That's ok if it's a type that generally tends to be binary.
if ( !in_array( substr( $type, 0, strcspn( $type, '/' ) ), array( 'application', 'video', 'audio' ) ) ) {
$type = $ext = false;
}
} elseif ( 0 === strpos( $real_mime, 'video/' ) || 0 === strpos( $real_mime, 'audio/' ) ) {
/*
* For these types, only the major type must match the real value.
* This means that common mismatches are forgiven: application/vnd.apple.numbers is often misidentified as application/zip,
* and some media files are commonly named with the wrong extension (.mov instead of .mp4)
*/
if ( substr( $real_mime, 0, strcspn( $real_mime, '/' ) ) !== substr( $type, 0, strcspn( $type, '/' ) ) ) {
$type = $ext = false;
}
} else {
if ( $type !== $real_mime ) {
/*
* Everything else including image/* and application/*:
* If the real content type doesn't match the file extension, assume it's dangerous.
*/
$type = $ext = false;
}
}
}
// The mime type must be allowed
if ( $type ) {
$allowed = get_allowed_mime_types();
if ( ! in_array( $type, $allowed ) ) {
$type = $ext = false;
}
}