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Media: Improve verification of MIME file types.

git-svn-id: https://develop.svn.wordpress.org/branches/5.0@43988 602fd350-edb4-49c9-b593-d223f7449a82
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jeremyfelt committed Dec 12, 2018
1 parent 1b91971 commit db9c4258f68f999f14c40349b4d37c717c814938
Showing with 63 additions and 8 deletions.
  1. +41 −6 src/wp-includes/functions.php
  2. +22 −2 tests/phpunit/tests/functions.php
@@ -2349,17 +2349,52 @@ function wp_check_filetype_and_ext( $file, $filename, $mimes = null ) {
$real_mime = finfo_file( $finfo, $file );
finfo_close( $finfo );
// 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 what we're expecting, we need to do some extra
* vetting of application mime types to make sure this type of file is allowed.
* Other mime types are assumed to be safe, but should be considered unverified.
* 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 ( $real_mime && ( $real_mime !== $type ) && ( 0 === strpos( $real_mime, 'application' ) ) ) {
$allowed = get_allowed_mime_types();
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 ( ! in_array( $real_mime, $allowed ) ) {
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;
}
}
@@ -1115,8 +1115,8 @@ public function _wp_check_filetype_and_ext_data() {
DIR_TESTDATA . '/formatting/big5.txt',
'big5.jpg',
array(
'ext' => 'jpg',
'type' => 'image/jpeg',
'ext' => false,
'type' => false,
'proper_filename' => false,
),
),
@@ -1130,6 +1130,26 @@ public function _wp_check_filetype_and_ext_data() {
'proper_filename' => false,
),
),
// Non-image file not allowed even if it's named like one.
array(
DIR_TESTDATA . '/export/crazy-cdata.xml',
'crazy-cdata.jpg',
array(
'ext' => false,
'type' => false,
'proper_filename' => false,
),
),
// Non-image file not allowed if it's named like something else.
array(
DIR_TESTDATA . '/export/crazy-cdata.xml',
'crazy-cdata.doc',
array(
'ext' => false,
'type' => false,
'proper_filename' => false,
),
),
);
// Test a few additional file types on single sites.

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