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<title>[43996] Media: Improve verification of MIME file types.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/43996">43996</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/43996","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>jeremyfelt</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2018-12-12 23:16:07 +0000 (Wed, 12 Dec 2018)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Media: Improve verification of MIME file types.
Merges <a href="https://core.trac.wordpress.org/changeset/43988">[43988]</a> to the 4.3 branch.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#branches43srcwpincludesfunctionsphp">branches/4.3/src/wp-includes/functions.php</a></li>
</ul>
<h3>Property Changed</h3>
<ul>
<li><a href="#branches43">branches/4.3/</a></li>
</ul>
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<div id="patch">
<h3>Diff</h3>
<span class="cx" style="display: block; padding: 0 10px">Index: branches/4.3
</span><span class="cx" style="display: block; padding: 0 10px">===================================================================
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">--- branches/4.3 2018-12-12 23:13:21 UTC (rev 43995)
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+++ branches/4.3 2018-12-12 23:16:07 UTC (rev 43996)
</ins><a id="branches43"></a>
<div class="propset"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Property changes: branches/4.3</h4>
<pre class="diff"><span>
</span></pre></div>
<a id="svnmergeinfo"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: svn:mergeinfo</h4></div>
<span class="cx" style="display: block; padding: 0 10px"> /branches/4.6:38615,41414
</span><span class="cx" style="display: block; padding: 0 10px"> /branches/4.8:42478
</span><span class="cx" style="display: block; padding: 0 10px"> /branches/4.9:42434
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+/branches/5.0:43988
</ins><span class="cx" style="display: block; padding: 0 10px"> /trunk:33646,33681,33688,33693,33710,33716,33727,33766,34094,34179,34219,34278,34788,34829,34834,36083,36435,37124,37651,38524,39645,39659,39759,39772,39795,39807-39808,39831,39850,39956,40148,40160,40169,40183,40195,40241,40255,40257-40259,40269,40271,40400,40538,40604,40677,40692,40704,40716,40723,40736,41072,41393,41395,41398,41457,41470,41483,41496,41522,41662,42056,42119-42120,42258-42261,42424,42433,42892-42893
</span><span class="cx" style="display: block; padding: 0 10px">\ No newline at end of property
</span><a id="branches43srcwpincludesfunctionsphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: branches/4.3/src/wp-includes/functions.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- branches/4.3/src/wp-includes/functions.php 2018-12-12 23:13:21 UTC (rev 43995)
+++ branches/4.3/src/wp-includes/functions.php 2018-12-12 23:16:07 UTC (rev 43996)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -2167,14 +2167,59 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $type = $ext = false;
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- } elseif ( function_exists( 'finfo_file' ) ) {
- // Use finfo_file if available to validate non-image files.
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ }
+
+ // Validate files that didn't get validated during previous checks.
+ if ( $type && ! $real_mime && extension_loaded( 'fileinfo' ) ) {
</ins><span class="cx" style="display: block; padding: 0 10px"> $finfo = finfo_open( FILEINFO_MIME_TYPE );
</span><span class="cx" style="display: block; padding: 0 10px"> $real_mime = finfo_file( $finfo, $file );
</span><span class="cx" style="display: block; padding: 0 10px"> finfo_close( $finfo );
</span><span class="cx" style="display: block; padding: 0 10px">
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- // If the extension does not match the file's real type, return false.
- if ( $real_mime !== $type ) {
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ // 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 ) ) {
</ins><span class="cx" style="display: block; padding: 0 10px"> $type = $ext = false;
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span></span></pre>
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