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<title>[24915] trunk/wp-includes: Additional checks when evaluating the safety of an HTTP request, to avoid false negatives.</title>
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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://core.trac.wordpress.org/changeset/24915">24915</a></dd>
<dt>Author</dt> <dd>nacin</dd>
<dt>Date</dt> <dd>2013-07-31 06:44:57 +0000 (Wed, 31 Jul 2013)</dd>
</dl>
<h3>Log Message</h3>
<pre>Additional checks when evaluating the safety of an HTTP request, to avoid false negatives.
* Check if the host is considered a safe redirect host.
* Check if the host is another domain in a multisite installation.
* Add a filter to control this.
This only occurs when the DNS resolution of a domain points elsewhere in an internal network, but only internally (and has its own public IP outside the network). This could be considered a bad configuration.
fixes <a href="http://core.trac.wordpress.org/ticket/24646">#24646</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkwpincludesdefaultfiltersphp">trunk/wp-includes/default-filters.php</a></li>
<li><a href="#trunkwpincludeshttpphp">trunk/wp-includes/http.php</a></li>
<li><a href="#trunkwpincludesmsdefaultfiltersphp">trunk/wp-includes/ms-default-filters.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkwpincludesdefaultfiltersphp"></a>
<div class="modfile"><h4>Modified: trunk/wp-includes/default-filters.php (24914 => 24915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/wp-includes/default-filters.php 2013-07-31 06:05:34 UTC (rev 24914)
+++ trunk/wp-includes/default-filters.php 2013-07-31 06:44:57 UTC (rev 24915)
</span><span class="lines">@@ -196,6 +196,8 @@
</span><span class="cx"> add_filter( 'pingback_ping_source_uri', 'pingback_ping_source_uri' );
</span><span class="cx"> add_filter( 'xmlrpc_pingback_error', 'xmlrpc_pingback_error' );
</span><span class="cx">
</span><ins>+add_filter( 'http_request_host_is_external', 'allowed_http_request_hosts', 10, 2 );
+
</ins><span class="cx"> // Actions
</span><span class="cx"> add_action( 'wp_head', 'wp_enqueue_scripts', 1 );
</span><span class="cx"> add_action( 'wp_head', 'feed_links', 2 );
</span></span></pre></div>
<a id="trunkwpincludeshttpphp"></a>
<div class="modfile"><h4>Modified: trunk/wp-includes/http.php (24914 => 24915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/wp-includes/http.php 2013-07-31 06:05:34 UTC (rev 24914)
+++ trunk/wp-includes/http.php 2013-07-31 06:44:57 UTC (rev 24915)
</span><span class="lines">@@ -451,15 +451,16 @@
</span><span class="cx"> $ip = false;
</span><span class="cx"> }
</span><span class="cx"> if ( $ip ) {
</span><del>- if ( '127.0.0.1' === $ip )
- return false;
</del><span class="cx"> $parts = array_map( 'intval', explode( '.', $ip ) );
</span><del>- if ( 10 === $parts[0] )
- return false;
- if ( 172 === $parts[0] && 16 <= $parts[1] && 31 >= $parts[1] )
- return false;
- if ( 192 === $parts[0] && 168 === $parts[1] )
- return false;
</del><ins>+ if ( '127.0.0.1' === $ip
+ || ( 10 === $parts[0] )
+ || ( 172 === $parts[0] && 16 <= $parts[1] && 31 >= $parts[1] )
+ || ( 192 === $parts[0] && 168 === $parts[1] )
+ ) {
+ // If host appears local, reject unless specifically allowed.
+ if ( ! apply_filters( 'http_request_host_is_external', false, $host, $url ) )
+ return false;
+ }
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -475,3 +476,44 @@
</span><span class="cx">
</span><span class="cx"> return false;
</span><span class="cx"> }
</span><ins>+
+/**
+ * Whitelists allowed redirect hosts for safe HTTP requests as well.
+ *
+ * Attached to the http_request_host_is_external filter.
+ *
+ * @since 3.6.0
+ *
+ * @param bool $is_external
+ * @param string $host
+ * @return bool
+ */
+function allowed_http_request_hosts( $is_external, $host ) {
+ if ( ! $is_external && wp_validate_redirect( 'http://' . $host ) )
+ $is_external = true;
+ return $is_external;
+}
+
+/**
+ * Whitelists any domain in a multisite installation for safe HTTP requests.
+ *
+ * Attached to the http_request_host_is_external filter.
+ *
+ * @since 3.6.0
+ *
+ * @param bool $is_external
+ * @param string $host
+ * @return bool
+ */
+function ms_allowed_http_request_hosts( $is_external, $host ) {
+ global $wpdb, $current_site;
+ static $queried = array();
+ if ( $is_external )
+ return $is_external;
+ if ( $host === $current_site->domain )
+ return true;
+ if ( isset( $queried[ $host ] ) )
+ return $queried[ $host ];
+ $queried[ $host ] = (bool) $wpdb->get_var( $wpdb->prepare( "SELECT domain FROM $wpdb->blogs WHERE domain = %s LIMIT 1", $host ) );
+ return $queried[ $host ];
+}
</ins></span></pre></div>
<a id="trunkwpincludesmsdefaultfiltersphp"></a>
<div class="modfile"><h4>Modified: trunk/wp-includes/ms-default-filters.php (24914 => 24915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/wp-includes/ms-default-filters.php 2013-07-31 06:05:34 UTC (rev 24914)
+++ trunk/wp-includes/ms-default-filters.php 2013-07-31 06:44:57 UTC (rev 24915)
</span><span class="lines">@@ -63,4 +63,7 @@
</span><span class="cx"> remove_filter( 'option_home', '_config_wp_home' );
</span><span class="cx">
</span><span class="cx"> // If the network upgrade hasn't run yet, assume ms-files.php rewriting is used.
</span><del>-add_filter( 'default_site_option_ms_files_rewriting', '__return_true' );
</del><span class="cx">\ No newline at end of file
</span><ins>+add_filter( 'default_site_option_ms_files_rewriting', '__return_true' );
+
+// Whitelist multisite domains for HTTP requests
+add_filter( 'http_request_host_is_external', 'ms_allowed_http_request_hosts', 20, 2 );
</ins></span></pre>
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