From c8bbd79d2dfe46b3f1ef12d6f127317c4546249d Mon Sep 17 00:00:00 2001
From: Felix Arntz <flixos90@git.wordpress.org>
Date: Fri, 19 Feb 2021 21:11:02 +0000
Subject: [PATCH] Security: Fix bug in `wp_is_local_html_output()`.

Prior to this changeset, the check for the correct RSD link output was relying on a specific protocol, although it needs to accept both the HTTP and HTTPS version of the URL.

Props TimothyBlynJacobs.
Fixes #52542. See #47577.


git-svn-id: https://develop.svn.wordpress.org/trunk@50391 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/https-detection.php     | 4 ++--
 tests/phpunit/tests/https-detection.php | 7 +++++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/https-detection.php b/src/wp-includes/https-detection.php
index 2ced175047..7642fda3da 100644
--- a/src/wp-includes/https-detection.php
+++ b/src/wp-includes/https-detection.php
@@ -204,7 +204,7 @@ function wp_cron_conditionally_prevent_sslverify( $request ) {
 function wp_is_local_html_output( $html ) {
 	// 1. Check if HTML includes the site's Really Simple Discovery link.
 	if ( has_action( 'wp_head', 'rsd_link' ) ) {
-		$pattern = esc_url( site_url( 'xmlrpc.php?rsd', 'rpc' ) ); // See rsd_link().
+		$pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( site_url( 'xmlrpc.php?rsd', 'rpc' ) ) ); // See rsd_link().
 		return false !== strpos( $html, $pattern );
 	}
 
@@ -218,7 +218,7 @@ function wp_is_local_html_output( $html ) {
 	// 3. Check if HTML includes the site's REST API link.
 	if ( has_action( 'wp_head', 'rest_output_link_wp_head' ) ) {
 		// Try both HTTPS and HTTP since the URL depends on context.
-		$pattern = esc_url( preg_replace( '#^https?:(?=//)#', '', get_rest_url() ) ); // See rest_output_link_wp_head().
+		$pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( get_rest_url() ) ); // See rest_output_link_wp_head().
 		return false !== strpos( $html, $pattern );
 	}
 
diff --git a/tests/phpunit/tests/https-detection.php b/tests/phpunit/tests/https-detection.php
index 70eeef51fd..e8c9d9057f 100644
--- a/tests/phpunit/tests/https-detection.php
+++ b/tests/phpunit/tests/https-detection.php
@@ -171,6 +171,7 @@ class Tests_HTTPS_Detection extends WP_UnitTestCase {
 
 	/**
 	 * @ticket 47577
+	 * @ticket 52542
 	 */
 	public function test_wp_is_local_html_output_via_rsd_link() {
 		// HTML includes RSD link.
@@ -183,6 +184,12 @@ class Tests_HTTPS_Detection extends WP_UnitTestCase {
 		$html     = $this->get_sample_html_string( $head_tag );
 		$this->assertTrue( wp_is_local_html_output( $html ) );
 
+		// HTML includes RSD link with alternative URL scheme.
+		$head_tag = get_echo( 'rsd_link' );
+		$head_tag = false !== strpos( $head_tag, 'https://' ) ? str_replace( 'https://', 'http://', $head_tag ) : str_replace( 'http://', 'https://', $head_tag );
+		$html     = $this->get_sample_html_string( $head_tag );
+		$this->assertTrue( wp_is_local_html_output( $html ) );
+
 		// HTML does not include RSD link.
 		$html = $this->get_sample_html_string();
 		$this->assertFalse( wp_is_local_html_output( $html ) );