Attempts to determine the real file type of a file.
If unable to, the file name extension will be used to determine type.
If it's determined that the extension does not match the file's real type, then the "proper_filename" value will be set with a proper filename and extension.
Currently this function only supports renaming images validated via wp_get_image_mime().
Suppose we upload a picture from a site that we can't trust for sure. So after uploading we need to check if it is really an image file and not some other type of file with the same extension as the image, for example, png, jpg, etc.
$file_url = 'http://placekitten.com/200/300';
// for the download_url function
require_once ABSPATH . 'wp-admin/includes/file.php';
$tmpfile = download_url( $file_url );
$checked = wp_check_filetype_and_ext( $tmpfile, 'kitten.jpg' );
print_r( $checked );
function wp_check_filetype_and_ext( $file, $filename, $mimes = null ) {
$proper_filename = false;
// Do basic extension validation and MIME mapping.
$wp_filetype = wp_check_filetype( $filename, $mimes );
$ext = $wp_filetype['ext'];
$type = $wp_filetype['type'];
// We can't do any further validation without a file to work with.
if ( ! file_exists( $file ) ) {
return compact( 'ext', 'type', 'proper_filename' );
}
$real_mime = false;
// Validate image types.
if ( $type && str_starts_with( $type, 'image/' ) ) {
// Attempt to figure out what type of image it actually is.
$real_mime = wp_get_image_mime( $file );
if ( $real_mime && $real_mime !== $type ) {
/**
* Filters the list mapping image mime types to their respective extensions.
*
* @since 3.0.0
*
* @param array $mime_to_ext Array of image mime types and their matching extensions.
*/
$mime_to_ext = apply_filters(
'getimagesize_mimes_to_exts',
array(
'image/jpeg' => 'jpg',
'image/png' => 'png',
'image/gif' => 'gif',
'image/bmp' => 'bmp',
'image/tiff' => 'tif',
'image/webp' => 'webp',
'image/avif' => 'avif',
)
);
// Replace whatever is after the last period in the filename with the correct extension.
if ( ! empty( $mime_to_ext[ $real_mime ] ) ) {
$filename_parts = explode( '.', $filename );
array_pop( $filename_parts );
$filename_parts[] = $mime_to_ext[ $real_mime ];
$new_filename = implode( '.', $filename_parts );
if ( $new_filename !== $filename ) {
$proper_filename = $new_filename; // Mark that it changed.
}
// Redefine the extension / MIME.
$wp_filetype = wp_check_filetype( $new_filename, $mimes );
$ext = $wp_filetype['ext'];
$type = $wp_filetype['type'];
} else {
// Reset $real_mime and try validating again.
$real_mime = false;
}
}
}
// 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 );
$google_docs_types = array(
'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
);
foreach ( $google_docs_types as $google_docs_type ) {
/*
* finfo_file() can return duplicate mime type for Google docs,
* this conditional reduces it to a single instance.
*
* @see https://bugs.php.net/bug.php?id=77784
* @see https://core.trac.wordpress.org/ticket/57898
*/
if ( 2 === substr_count( $real_mime, $google_docs_type ) ) {
$real_mime = $google_docs_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' ), true ) ) {
$type = false;
$ext = false;
}
} elseif ( str_starts_with( $real_mime, 'video/' ) || str_starts_with( $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 = false;
$ext = false;
}
} elseif ( 'text/plain' === $real_mime ) {
// A few common file types are occasionally detected as text/plain; allow those.
if ( ! in_array(
$type,
array(
'text/plain',
'text/csv',
'application/csv',
'text/richtext',
'text/tsv',
'text/vtt',
),
true
)
) {
$type = false;
$ext = false;
}
} elseif ( 'application/csv' === $real_mime ) {
// Special casing for CSV files.
if ( ! in_array(
$type,
array(
'text/csv',
'text/plain',
'application/csv',
),
true
)
) {
$type = false;
$ext = false;
}
} elseif ( 'text/rtf' === $real_mime ) {
// Special casing for RTF files.
if ( ! in_array(
$type,
array(
'text/rtf',
'text/plain',
'application/rtf',
),
true
)
) {
$type = false;
$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 = false;
$ext = false;
}
}
}
// The mime type must be allowed.
if ( $type ) {
$allowed = get_allowed_mime_types();
if ( ! in_array( $type, $allowed, true ) ) {
$type = false;
$ext = false;
}
}
/**
* Filters the "real" file type of the given file.
*
* @since 3.0.0
* @since 5.1.0 The $real_mime parameter was added.
*
* @param array $wp_check_filetype_and_ext {
* Values for the extension, mime type, and corrected filename.
*
* @type string|false $ext File extension, or false if the file doesn't match a mime type.
* @type string|false $type File mime type, or false if the file doesn't match a mime type.
* @type string|false $proper_filename File name with its correct extension, or false if it cannot be determined.
* }
* @param string $file Full path to the file.
* @param string $filename The name of the file (may differ from $file due to
* $file being in a tmp directory).
* @param string[]|null $mimes Array of mime types keyed by their file extension regex, or null if
* none were provided.
* @param string|false $real_mime The actual mime type or false if the type cannot be determined.
*/
return apply_filters( 'wp_check_filetype_and_ext', compact( 'ext', 'type', 'proper_filename' ), $file, $filename, $mimes, $real_mime );
}