1<?php
  2/**
  3 * HTTPS detection functions.
  4 *
  5 * @package WordPress
  6 * @since 5.7.0
  7 */
  8
  9/**
 10 * Checks whether the website is using HTTPS.
 11 *
 12 * This is based on whether both the home and site URL are using HTTPS.
 13 *
 14 * @since 5.7.0
 15 * @see wp_is_home_url_using_https()
 16 * @see wp_is_site_url_using_https()
 17 *
 18 * @return bool True if using HTTPS, false otherwise.
 19 */
 20function wp_is_using_https() {
 21	if ( ! wp_is_home_url_using_https() ) {
 22		return false;
 23	}
 24
 25	return wp_is_site_url_using_https();
 26}
 27
 28/**
 29 * Checks whether the current site URL is using HTTPS.
 30 *
 31 * @since 5.7.0
 32 * @see home_url()
 33 *
 34 * @return bool True if using HTTPS, false otherwise.
 35 */
 36function wp_is_home_url_using_https() {
 37	return 'https' === wp_parse_url( home_url(), PHP_URL_SCHEME );
 38}
 39
 40/**
 41 * Checks whether the current site's URL where WordPress is stored is using HTTPS.
 42 *
 43 * This checks the URL where WordPress application files (e.g. wp-blog-header.php or the wp-admin/ folder)
 44 * are accessible.
 45 *
 46 * @since 5.7.0
 47 * @see site_url()
 48 *
 49 * @return bool True if using HTTPS, false otherwise.
 50 */
 51function wp_is_site_url_using_https() {
 52	/*
 53	 * Use direct option access for 'siteurl' and manually run the 'site_url'
 54	 * filter because `site_url()` will adjust the scheme based on what the
 55	 * current request is using.
 56	 */
 57	/** This filter is documented in wp-includes/link-template.php */
 58	$site_url = apply_filters( 'site_url', get_option( 'siteurl' ), '', null, null );
 59
 60	return 'https' === wp_parse_url( $site_url, PHP_URL_SCHEME );
 61}
 62
 63/**
 64 * Checks whether HTTPS is supported for the server and domain.
 65 *
 66 * This function makes an HTTP request through `wp_get_https_detection_errors()`
 67 * to check for HTTPS support. As this process can be resource-intensive,
 68 * it should be used cautiously, especially in performance-sensitive environments,
 69 * to avoid potential latency issues.
 70 *
 71 * @since 5.7.0
 72 *
 73 * @return bool True if HTTPS is supported, false otherwise.
 74 */
 75function wp_is_https_supported() {
 76	$https_detection_errors = wp_get_https_detection_errors();
 77
 78	// If there are errors, HTTPS is not supported.
 79	return empty( $https_detection_errors );
 80}
 81
 82/**
 83 * Runs a remote HTTPS request to detect whether HTTPS supported, and stores potential errors.
 84 *
 85 * This function checks for HTTPS support by making an HTTP request. As this process can be resource-intensive,
 86 * it should be used cautiously, especially in performance-sensitive environments.
 87 * It is called when HTTPS support needs to be validated.
 88 *
 89 * @since 6.4.0
 90 * @access private
 91 *
 92 * @return array An array containing potential detection errors related to HTTPS, or an empty array if no errors are found.
 93 */
 94function wp_get_https_detection_errors() {
 95	/**
 96	 * Short-circuits the process of detecting errors related to HTTPS support.
 97	 *
 98	 * Returning a `WP_Error` from the filter will effectively short-circuit the default logic of trying a remote
 99	 * request to the site over HTTPS, storing the errors array from the returned `WP_Error` instead.
100	 *
101	 * @since 6.4.0
102	 *
103	 * @param null|WP_Error $pre Error object to short-circuit detection,
104	 *                           or null to continue with the default behavior.
105	 */
106	$support_errors = apply_filters( 'pre_wp_get_https_detection_errors', null );
107	if ( is_wp_error( $support_errors ) ) {
108		return $support_errors->errors;
109	}
110
111	$support_errors = new WP_Error();
112
113	$response = wp_remote_request(
114		home_url( '/', 'https' ),
115		array(
116			'headers'   => array(
117				'Cache-Control' => 'no-cache',
118			),
119			'sslverify' => true,
120		)
121	);
122
123	if ( is_wp_error( $response ) ) {
124		$unverified_response = wp_remote_request(
125			home_url( '/', 'https' ),
126			array(
127				'headers'   => array(
128					'Cache-Control' => 'no-cache',
129				),
130				'sslverify' => false,
131			)
132		);
133
134		if ( is_wp_error( $unverified_response ) ) {
135			$support_errors->add(
136				'https_request_failed',
137				__( 'HTTPS request failed.' )
138			);
139		} else {
140			$support_errors->add(
141				'ssl_verification_failed',
142				__( 'SSL verification failed.' )
143			);
144		}
145
146		$response = $unverified_response;
147	}
148
149	if ( ! is_wp_error( $response ) ) {
150		if ( 200 !== wp_remote_retrieve_response_code( $response ) ) {
151			$support_errors->add( 'bad_response_code', wp_remote_retrieve_response_message( $response ) );
152		} elseif ( false === wp_is_local_html_output( wp_remote_retrieve_body( $response ) ) ) {
153			$support_errors->add( 'bad_response_source', __( 'It looks like the response did not come from this site.' ) );
154		}
155	}
156
157	return $support_errors->errors;
158}
159
160/**
161 * Checks whether a given HTML string is likely an output from this WordPress site.
162 *
163 * This function attempts to check for various common WordPress patterns whether they are included in the HTML string.
164 * Since any of these actions may be disabled through third-party code, this function may also return null to indicate
165 * that it was not possible to determine ownership.
166 *
167 * @since 5.7.0
168 * @access private
169 *
170 * @param string $html Full HTML output string, e.g. from a HTTP response.
171 * @return bool|null True/false for whether HTML was generated by this site, null if unable to determine.
172 */
173function wp_is_local_html_output( $html ) {
174	// 1. Check if HTML includes the site's Really Simple Discovery link.
175	if ( has_action( 'wp_head', 'rsd_link' ) ) {
176		$pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( site_url( 'xmlrpc.php?rsd', 'rpc' ) ) ); // See rsd_link().
177		return str_contains( $html, $pattern );
178	}
179
180	// 2. Check if HTML includes the site's REST API link.
181	if ( has_action( 'wp_head', 'rest_output_link_wp_head' ) ) {
182		// Try both HTTPS and HTTP since the URL depends on context.
183		$pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( get_rest_url() ) ); // See rest_output_link_wp_head().
184		return str_contains( $html, $pattern );
185	}
186
187	// Otherwise the result cannot be determined.
188	return null;
189}
190