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<title>[52304] trunk: KSES: Allow attributes to be restricted via callbacks.</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/52304">52304</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/52304","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>peterwilsoncc</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2021-12-02 00:54:03 +0000 (Thu, 02 Dec 2021)</dd>
</dl>
<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>KSES: Allow attributes to be restricted via callbacks.
Add callback validation to HTML tag attributes for increased flexibility over an array of values only.
In `object` tags, validate the `data` attribute via a callback to ensure it is a PDF and matches the `type` attribute. This prevents mime type mismatches in browsers.
Follow up to <a href="https://core.trac.wordpress.org/changeset/51963">[51963]</a>.
Props Pento, dd32, swissspidy, xknown, peterwilsoncc.
Fixes <a href="https://core.trac.wordpress.org/ticket/54261">#54261</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludesksesphp">trunk/src/wp-includes/kses.php</a></li>
<li><a href="#trunktestsphpunittestsksesphp">trunk/tests/phpunit/tests/kses.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludesksesphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/kses.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/kses.php 2021-12-01 23:59:55 UTC (rev 52303)
+++ trunk/src/wp-includes/kses.php 2021-12-02 00:54:03 UTC (rev 52304)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -272,7 +272,10 @@
</span><span class="cx" style="display: block; padding: 0 10px"> 'xml:lang' => true,
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'object' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- 'data' => true,
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ 'data' => array(
+ 'required' => true,
+ 'value_callback' => '_wp_kses_allow_pdf_objects',
+ ),
</ins><span class="cx" style="display: block; padding: 0 10px"> 'type' => array(
</span><span class="cx" style="display: block; padding: 0 10px"> 'required' => true,
</span><span class="cx" style="display: block; padding: 0 10px"> 'values' => array( 'application/pdf' ),
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1661,6 +1664,17 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $ok = false;
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> break;
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+ case 'value_callback':
+ /*
+ * The value_callback check is used when you want to make sure that the attribute
+ * value is accepted by the callback function.
+ */
+
+ if ( ! call_user_func( $checkvalue, $value ) ) {
+ $ok = false;
+ }
+ break;
</ins><span class="cx" style="display: block; padding: 0 10px"> } // End switch.
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> return $ok;
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -2566,3 +2580,34 @@
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> return $value;
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+/**
+ * Helper function to check if this is a safe PDF URL.
+ *
+ * @since 5.9.0
+ * @access private
+ * @ignore
+ *
+ * @param string $url The URL to check.
+ * @return bool True if the URL is safe, false otherwise.
+ */
+function _wp_kses_allow_pdf_objects( $value ) {
+ // We're not interested in URLs that contain query strings or fragments.
+ if ( strpos( $value, '?' ) !== false || strpos( $value, '#' ) !== false ) {
+ return false;
+ }
+
+ // If it doesn't have a PDF extension, it's not safe.
+ if ( 0 !== substr_compare( $value, '.pdf', -4, 4, true ) ) {
+ return false;
+ }
+
+ // If the URL host matches the current site's media URL, it's safe.
+ $upload_info = wp_upload_dir( null, false );
+ $upload_host = wp_parse_url( $upload_info['url'], PHP_URL_HOST );
+ if ( 0 === strpos( $value, "http://$upload_host/" ) || 0 === strpos( $value, "https://$upload_host/" ) ) {
+ return true;
+ }
+
+ return false;
+}
</ins></span></pre></div>
<a id="trunktestsphpunittestsksesphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/kses.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/kses.php 2021-12-01 23:59:55 UTC (rev 52303)
+++ trunk/tests/phpunit/tests/kses.php 2021-12-02 00:54:03 UTC (rev 52304)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1517,61 +1517,85 @@
</span><span class="cx" style="display: block; padding: 0 10px"> function data_wp_kses_object_tag_allowed() {
</span><span class="cx" style="display: block; padding: 0 10px"> return array(
</span><span class="cx" style="display: block; padding: 0 10px"> 'valid value for type' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'invalid value for type' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/exe" data="https://wordpress.org/foo.exe" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/exe" data="https://example.org/foo.exe" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, last invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/pdf" type="application/exe" data="https://wordpress.org/foo.pdf" />',
- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/pdf" type="application/exe" data="https://example.org/foo.pdf" />',
+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, first uppercase, last invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object TYPE="application/pdf" type="application/exe" data="https://wordpress.org/foo.pdf" />',
- '<object TYPE="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object TYPE="application/pdf" type="application/exe" data="https://example.org/foo.pdf" />',
+ '<object TYPE="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, last upper case and invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/pdf" TYPE="application/exe" data="https://wordpress.org/foo.pdf" />',
- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/pdf" TYPE="application/exe" data="https://example.org/foo.pdf" />',
+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, first invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/exe" type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/exe" type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, first upper case and invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object TYPE="application/exe" type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object TYPE="application/exe" type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple type attributes, first invalid, last uppercase' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/exe" TYPE="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/exe" TYPE="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple object tags, last invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" /><object type="application/exe" data="https://wordpress.org/foo.exe" />',
- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/pdf" data="https://example.org/foo.pdf" /><object type="application/exe" data="https://example.org/foo.exe" />',
+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'multiple object tags, first invalid' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/exe" data="https://wordpress.org/foo.exe" /><object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
- '<object type="application/pdf" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/exe" data="https://example.org/foo.exe" /><object type="application/pdf" data="https://example.org/foo.pdf" />',
+ '<object type="application/pdf" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'type attribute with partially incorrect value' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="application/pdfa" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="application/pdfa" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'type attribute with empty value' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type="" data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type="" data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'type attribute with no value' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object type data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object type data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><span class="cx" style="display: block; padding: 0 10px"> 'no type attribute' => array(
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- '<object data="https://wordpress.org/foo.pdf" />',
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ '<object data="https://example.org/foo.pdf" />',
</ins><span class="cx" style="display: block; padding: 0 10px"> '',
</span><span class="cx" style="display: block; padding: 0 10px"> ),
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ 'different protocol in url' => array(
+ '<object type="application/pdf" data="http://example.org/foo.pdf" />',
+ '<object type="application/pdf" data="http://example.org/foo.pdf" />',
+ ),
+ 'query string on url' => array(
+ '<object type="application/pdf" data="https://example.org/foo.pdf?lol=.pdf" />',
+ '',
+ ),
+ 'fragment on url' => array(
+ '<object type="application/pdf" data="https://example.org/foo.pdf#lol.pdf" />',
+ '',
+ ),
+ 'wrong extension' => array(
+ '<object type="application/pdf" data="https://example.org/foo.php" />',
+ '',
+ ),
+ 'protocol relative url' => array(
+ '<object type="application/pdf" data="//example.org/foo.pdf" />',
+ '',
+ ),
+ 'relative url' => array(
+ '<object type="application/pdf" data="/cat/foo.pdf" />',
+ '',
+ ),
</ins><span class="cx" style="display: block; padding: 0 10px"> );
</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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