From 9c3ce8628020e25399ffc8a079a509617302e127 Mon Sep 17 00:00:00 2001
From: ryan <ryan@1a063a9b-81f0-0310-95a4-ce76da25c4cd>
Date: Tue, 15 May 2012 18:46:03 +0000
Subject: [PATCH] API for allowing cross origin resource sharing.

* Allowed origin whitelist that can be altered by plugins
* Validation of the request origin against the whitelist
* Send Access-Control-Allow-Origin if origin allowed
* get_http_origin(), get_allowed_http_origins(), is_allowed_http_origin(), send_origin_headers()

See #20681



git-svn-id: http://core.svn.wordpress.org/trunk@20794 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/class-wp-customize.php | 12 +----
 wp-includes/http.php               | 77 ++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+), 11 deletions(-)

diff --git a/wp-includes/class-wp-customize.php b/wp-includes/class-wp-customize.php
index 198d979bf..ffae10619 100644
--- a/wp-includes/class-wp-customize.php
+++ b/wp-includes/class-wp-customize.php
@@ -71,17 +71,7 @@ final class WP_Customize {
 		if ( ! isset( $_REQUEST['customize'] ) || 'on' != $_REQUEST['customize'] )
 			return;
 
-		$url = parse_url( admin_url() );
-		$allowed_origins = array( 'http://' . $url[ 'host' ],  'https://' . $url[ 'host' ] );
-		// @todo preserve port?
-		if ( isset( $_SERVER[ 'HTTP_ORIGIN' ] ) && in_array( $_SERVER[ 'HTTP_ORIGIN' ], $allowed_origins ) ) {
-			$origin = $_SERVER[ 'HTTP_ORIGIN' ];
-		} else {
-			$origin = $url[ 'scheme' ] . '://' . $url[ 'host' ];
-		}
-
-		@header( 'Access-Control-Allow-Origin: ' .  $origin );
-		@header( 'Access-Control-Allow-Credentials: true' );
+		send_origin_headers();
 
 		$this->start_previewing_theme();
 		show_admin_bar( false );
diff --git a/wp-includes/http.php b/wp-includes/http.php
index 6d3dcffa6..dd9df6e73 100644
--- a/wp-includes/http.php
+++ b/wp-includes/http.php
@@ -222,3 +222,80 @@ function wp_http_supports( $capabilities = array(), $url = null ) {
 
 	return (bool) $objFetchSite->_get_first_available_transport( $capabilities );
 }
+
+/**
+ * Get the HTTP Origin of the current request.
+ *
+ * @since 3.4.0
+ *
+ * @return string URL of the origin. Empty string if no origin.
+ */
+function get_http_origin() {
+	$origin = '';
+	if ( ! empty ( $_SERVER[ 'HTTP_ORIGIN' ] ) )
+		$origin = $_SERVER[ 'HTTP_ORIGIN' ];
+
+	return apply_filters( 'http_origin', $origin );
+}
+
+/**
+ * Retrieve list of allowed http origins.
+ *
+ * @since 3.4.0
+ *
+ * @return array Array of origin URLs.
+ */
+function get_allowed_http_origins() {
+	$admin_origin = parse_url( admin_url() );
+	$home_origin = parse_url( home_url() );
+
+	// @todo preserve port?
+	$allowed_origins = array_unique( array(
+		'http://' . $admin_origin[ 'host' ],
+		'https://' . $admin_origin[ 'host' ],
+		'http://' . $home_origin[ 'host' ],
+		'https://' . $home_origin[ 'host' ],
+	) );
+
+	return apply_filters( 'allowed_http_origins' , $allowed_origins );
+}
+
+/**
+ * Determines if the http origin is an authorized one.
+ *
+ * @since 3.4.0
+ *
+ * @param string Origin URL. If not provided, the value of get_http_origin() is used.
+ * @return bool True if the origin is allowed. False otherwise.
+ */
+function is_allowed_http_origin( $origin = null ) {
+	$origin_arg = $origin;
+
+	if ( null === $origin )
+		$origin = get_http_origin();
+
+	if ( $origin && ! in_array( $origin, get_allowed_http_origins() ) )
+		$origin = '';
+
+	return apply_filters( 'allowed_http_origin', $origin, $origin_arg );
+}
+
+/**
+ * Send Access-Control-Allow-Origin and related headers if the current request
+ * is from an allowed origin.
+ *
+ * @since 3.4.0
+ *
+ * @return bool|string Returns the origin URL if headers are sent. Returns false
+ * if headers are not sent.
+ */
+function send_origin_headers() {
+	$origin = get_http_origin();
+	if ( ! is_allowed_http_origin( $origin ) )
+		return false;
+
+	@header( 'Access-Control-Allow-Origin: ' .  $origin );
+	@header( 'Access-Control-Allow-Credentials: true' );
+
+	return $origin;
+}
\ No newline at end of file